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GEOL6363 Carbonate Sedimentalogy - Day3 01-27-2023
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01:41 Okay, sorry about that. So those, those of you that are
01:56 , I just said I'm going to the test. I'll scan them,
02:00 return them back to you then I'll you a version with my answers on
02:09 . Okay. And um then we'll the basis for comparison and then we
02:14 discuss, we can discuss the uh exam when we start next, uh
02:24 friday. Okay, we can go this exam briefly. Any questions you
02:28 have anything that was confusing. So then I said the final will cover
02:37 potentially anything that we've covered in the segments can be on the final
02:42 but obviously most of the final is to the stuff next weekend, which
02:47 the play types because that's really the of everything we talked about for the
02:52 two segments ties back to reservoirs and plays in the subsurface and that's what
03:01 be focusing on for the final. , alright, so last weekend we
03:12 into basically a review of a lot the first principles of carbonate geology and
03:19 talked a lot about the different pathways process evolution and live stones and Dolar
03:25 . And now we're going to get sort of building a bigger picture,
03:31 ? We're basically building a sedimentary carbonate . We've talked about all the little
03:37 parts that make up these rocks, ? The grain types of the
03:40 right? The cement fabrics and things that. And now we need to
03:45 this into a context and our first will be the environments in which these
03:51 tend to occur in some of the marine die genesis that comes along with
03:57 sedimentary environments. Because sometimes the die , the marine die genesis actually is
04:03 attribute for some of these carbonate So we want to be paying attention
04:08 not only the composition and texture, also some of the early marine die
04:13 fabrics because they keys into position along deposition on profile. So what I'm
04:22 do over the next two days is gonna take you through modern carbonate
04:26 I'm gonna give you a feel for setting. I'm going to give you
04:29 feel for the controls. I'm going try to give you a feel for
04:31 scale. Uh There's no way the I show you can do justice to
04:37 it's like to be in the but obviously we can't go in the
04:41 . So we're gonna have to work from the slides and I'll work in
04:46 little bit of video tomorrow, maybe afternoon and show you what some of
04:51 environments are like. Um So everything is gonna be out of context and
05:00 I'm gonna come back and talk about two end member models we use to
05:04 to guide our prediction of carbonate faces the subsurface. Okay, and you
05:10 see how I'm defining the term On this diagram. It's a rocker
05:16 rocker sediment the body of sediment Okay, that reflects an environment of
05:23 . So the term faces gets misused the time in the literature. People
05:28 terms like grain stone and pack stone a faces term. Well, what
05:32 that mean? Environmentally? It means nothing. All right. Because you
05:36 get a grain stone on a high carbonate sand body along the platform
05:40 You get a grain stone developed at beach 50 km in from the platform
05:46 . You can get a grain stone a title flat thrown up by
05:50 Okay, so we want to be precise, we want to think in
05:54 of de positional setting. So a wacky stone is a faces term.
06:01 ? It tells you the texture but tells you the environment. Platform
06:05 Restful routes stone is a faces Right. Because it tells you of
06:10 a tidal flat, wacky stone would a faces term. Okay, so
06:17 our goal toward the end here, to try to think in terms of
06:20 settings. Now, sometimes we can't that by just looking at one body
06:25 sediment out of context. Sometimes we to put it all together vertically or
06:29 really understand where we're at deposition. , and that's gonna come later tomorrow
06:37 we jump from the modern to the record and we had the time factor
06:41 we left the sedimentary environments evolve the and the geometry and this is what
06:46 call this is what I called positional and cyclist city. The buzzword in
06:53 literature is sequenced photography. Okay. we'll talk about the different approaches to
06:58 that later. But but that's where headed. All right. And then
07:03 end of tomorrow afternoon after we talked how these things are packaged together in
07:08 sequences and cyclist city. Then I'll the discussion a little bit and talk
07:12 log and seismic response and how we that information to try to break out
07:18 different packages. All right. And basically by that time next weekend we'll
07:23 ready to talk about carbonate plays and in the subsurface and try to offer
07:28 guidelines about predictability alright, In terms geological age and setting. So that's
07:36 we're spending so much time talking about because the play types actually key back
07:41 position along these depositions profiles. so what we're gonna start with today
07:47 basically a whirlwind tour of modern carbonate and these are called holocene age carbonate
07:54 . The definition of holocene as you on this diagram is is less than
07:58 years old. But really Most of I'm going to show you is only
08:04 years old or less because of the of Holocene Sea level change.
08:10 so I'll get into the whole scene level story here in a little bit
08:16 um we've been studying these modern environments for I mean really some of these
08:23 go back to late 18 hundreds, the classical studies start in the 19
08:28 . And the real devotion to studying carbon environment starts the 19 fifties.
08:33 , so for the last 60 60 70 years, we've been studying
08:37 modern environments and we do that to relate faces, attributes the texture,
08:43 fond of the process, the geometry the deposition setting. And then we
08:48 that information and we try to apply the rock record. And so the
08:53 term is compared to sediment ology. frankly it has revolutionized our understanding of
09:00 ancient carbonate systems before that. All could do is basically describe stuff.
09:05 mean, people had an idea some these deposits were associated with reefs or
09:10 ups, right. But they didn't understand the context for what controlled their
09:14 and distribution. So carbonates climatology is the key approach here. You
09:21 this in classics to people study modern islands and and estuaries and things like
09:29 . And try to apply to the record. And we do the same
09:32 carbonates, right? And we spend lot of time in the field in
09:36 modern just for that purpose to understand controls to understand the scale and then
09:41 to apply that to the rock Okay, so if you recall this
09:47 diagram, I showed you when we the first day last week, uh
09:52 map of the world. To give a feel for the setting of the
09:56 carbonate environments. And I told you of our classical modern carbonate environments and
10:04 are florida and the Bahamas. Uh caribbean, like the police, and
10:11 the Arabian gulf and the Middle and then areas in south china
10:15 northeast and northwest sides of Australia. common thread here again is that this
10:21 tropical subtropical setting. The water as talked about is clear, warm,
10:28 saturated spectra, calcium carbonate. You get persistence list of plastic settlement in
10:35 . You don't get the murky water ? You need you need that clear
10:40 for photosynthesis for many of these organisms are tied to these carbonate settings.
10:47 I mean the shallow water step is generally less than 10 m of water
10:51 . Alright. And we talked about trade wind influences that come into play
10:56 . Okay. And so I want to start thinking in terms of this
11:02 of fizzy graphic setting. You can the term paleo geography for that as
11:08 . Alright. But it's a geographic that's influenced by both climatic and other
11:15 controls that operate on a local All right. And I want you
11:20 appreciate that we need to start thinking terms of fizzy graphic setting at both
11:26 global scale and a local scale. the global scale means proximity to the
11:33 equator. We talked about this last , right? The right at the
11:38 equator, 5° on either side of equator. You don't get the trade
11:45 blowing right, that's the doldrums. once you get away from that five
11:51 to 30 on either side of the , you're influenced by these prevailing easterly
11:56 winds systems that we talked about. , and so that's the first key
12:02 on the global scale. And then local scale determines the bottom topography or
12:08 is the bottom topography. Right. we're going to talk about the two
12:11 member models in a minute that govern bottom topography and by definition they govern
12:17 symmetry or depth of water across that . And that's one of the key
12:22 on circulation of marine fluid in that . Okay. And you're going to
12:28 that the boat together can strongly impact styles of shallow marine carbonate deposition.
12:36 I showed you this diagram, last friday when we started again to
12:40 you, is this too bright for guys? Can you see this?
12:45 you falling along on the, on computers anyway? Okay. So remember
12:52 wind systems here and when we say trade winds, we don't mean they
12:55 blow out of the eastern quadrant, can be a Northeast and the southeast
13:00 and as I said last week, can vary during the year. Sometimes
13:04 can vary from week to week. that varies during the year. Sometimes
13:07 varies from year to year. And the strength of the trade winds
13:13 from 5° north of the equator to 22 on either side. And then
13:18 more gentle easterly trade winds from about to 30° on either side.
13:26 And you know for this discussion, going to focus these, trying to
13:32 you a better feel for the setting these modern carbonate environments associated with florida
13:38 beliefs. Great barrier reef. The gulf. I'm not going to talk
13:42 much about south florida and southeast but there's plenty of literature that the
13:47 that. But I think, you , for you to get a good
13:51 of how these environments are put We're basically gonna focus in on the
13:56 uh, for the shallow water carbonate story and then some of the reef
14:01 that's associated with that will also talk from police in the western caribbean and
14:07 that with a great, great barrier in Australia. And then the other
14:12 member model, which is called the ramp. That's basically based on studies
14:18 have been done in the Arabian gulf the, in the Middle East.
14:24 , so the classical, let me up here when, when I was
14:29 grad student, we didn't even think terms of ramps and platforms, we
14:34 this nebulous term called shelf, Which is a related to the old
14:40 continental shelf. And people still use term continental shelf. Right. But
14:46 , while it's still using the literature , I would highly discourage it in
14:50 world of carbonates. What we're trying do now is put it in the
14:55 of these two end Member models. , the carbonate ramp model, the
14:59 of the carbonate ramp model is the angle from an older landmass out into
15:04 basin is by definition one degree or . Right. That's essentially an imperceptible
15:10 in water depth as you go from out into deeper water. All
15:15 And in this model, the deep basin is relatively shallow tens of
15:23 maybe a few 100 m of water . Okay, we're not talking great
15:26 depth like we have in the caribbean . All right. You don't get
15:30 in a carbonate ramp model. And gonna see the most carbonate ramps are
15:35 with these shallow interpret tonic basins. structural sags that develop up on a
15:42 and they tend not to be a water depth. Okay, certainly tend
15:46 to be connected to a true deep open ocean. All right. And
15:51 the other end member model is what going to show you for the Bahamas
15:55 definition shall water platform, 10 m water depth or less dropping abruptly abruptly
16:01 into a deeper water basin. In this model, the basins tend
16:07 be really deep, hundreds of meters several thousands of meters of water
16:11 Okay, so those are the two Member models. Alright, now you
16:18 have anything in between those two. , But we need something to start
16:21 for discussion, right? Or for better improved prediction, but realize that
16:27 not uncommon for carbonate ramp to do to eventually evolve to something like a
16:32 margin platform. And I'll show you of that in our in our discussion
16:38 . Okay, it's a little bit to go from a carbonated platform that
16:43 a hole or basin that is a ft water depth like we have today
16:48 the Bahamas, the only way you revert that back to a ramp would
16:52 to fill the hole in somehow. , that's a lot of filling to
16:57 , write a lot of shoveling to sediment in there and that would probably
17:00 to be some sort of plastic influx sediment to fill that basin and convert
17:05 back to a ramp. Okay, , you know, this is the
17:10 we used to look at things until eighties, late eighties when we started
17:14 study the southern Bahamas and and appreciate trade wind effects on carbonate deposition.
17:21 now it's not enough to just think terms of the End Member models,
17:25 do, we need to also think terms of orientation to the prevailing trade
17:30 . Okay, because if you're in tropical subtropical setting, those platforms have
17:36 potential to face into the wind or have the potential to face away from
17:40 wind. Right? So when we're or leeward facing and then think about
17:45 isolated carbonate platform, that's basically the today. Right. They sit surrounded
17:52 true oceanic water depth. And so going to be a when we're facing
17:56 to the Bahamas, there's gonna be leeward facing side. And this relationship
18:01 very, very common in the rock . Okay, You build a structural
18:05 offshore, surrounded by relatively deep water a tropical subtropical setting. You're gonna
18:11 a windward side. You're gonna have leeward side. Okay. And so
18:15 need to also think in those terms with respect to the trade winds,
18:19 they govern the styles of deposition up the shallow water platform, and they
18:25 determine which side of the platform is to shed more sediment relative to the
18:30 . Okay, And so that's an concept and then the strength of the
18:35 winds determines what gets shut. Is it just the fine grained mud
18:40 silt sized material? Or is it carbonate sand that comes off with the
18:45 winds? Okay, because that creates for play development on leeward sides of
18:50 of these platforms. Okay. And course storms are always part of the
18:55 , right storms will not only shed grained carbonate material, they'll bring carbonate
19:00 and coarser debris as well. But critical way to create these so called
19:06 lapping wedges that have reservoir potential is persistently shut the course of grain material
19:13 storms don't persistently shed. Right? come maybe every 10 years, 20
19:18 they'll shed some material, but it's day to day trade wind action that
19:22 determines what gets shed. Whether these lapping wedges have aim a critic composition
19:29 poor reservoir potential or whether they have sand texture, carbonate sand texture with
19:35 reservoir potential. Okay, so, know, we're gonna spend a lot
19:41 time talking about the bahama platform complex because it is our is the basis
19:47 the state margin platform model, the end member model. And I want
19:51 to appreciate that the scale here of platform complex. So on this
19:57 you can see south florida, You see south board up here,
20:01 see the bahama platform complex here and some other carbonate settings here in the
20:09 the ancestors, in the gulf of and the western caribbean sea that we'll
20:13 about police. It's over here in western side here. This is this
20:18 a classical area of, of platform barrier reef deposition, you know,
20:25 bahama platform complex which includes the larger Bahamas that I'm highlighting with the cursor
20:32 then keiko's platform here to the which is smaller. That entire area
20:37 about 300,000 square kilometers of shallow water material. Right. So everything that's
20:43 blue essentially is 10 m of water or less. All right. I
20:49 that's pretty large area when you think it. But when you compare it
20:53 to some of our ancient carbonate like we had in the lower paleozoic
20:58 like we had in the in the cretaceous where we had these wide
21:03 right? These so called epic continental that covered most of the creighton.
21:08 small potatoes in terms of aerial Right? So one of the things
21:14 have to be careful about when you modern environments is appreciate the scale perspective
21:21 we see today and how it might back to the rock record. All
21:25 . You have to be a little there when you're applying the scale
21:30 And then what's the other thing that's ? Obviously we talked about the scalable
21:34 types last week. Right. You how they changed depending on the
21:40 Right, paleozoic stuff different than than or younger stuff sometimes. Right.
21:46 you need to keep that in So the organisms clearly we have
21:50 not all of them existed back in geological time periods, back safe in
21:55 paleozoic or Mesozoic. And so you to be careful there. Right.
22:02 really what you want to glean from modern is is the kinds of organisms
22:06 occupy these niches like reefs or sand . And take that information applied back
22:12 the rock record, right? Because are no rocket pods to speak of
22:18 . Like we had back in the , right? The strom atop roids
22:22 made reefs back in this Learning Devonian really exist today, making reefs.
22:27 , so so but despite that, mean, we can we can glean
22:31 lot of information from the modern, back to the rock record. That's
22:35 basis for comparative sediment ology. And and frankly, it's revolutionized our understanding
22:43 ancient carbonate systems and people that, know, sort of knocked this approach
22:49 find are people who've never been in modern right. They've never been to
22:52 modern setting. So they don't really what you can glean from a modern
22:57 environment. Okay, Okay. So beauty of study modern carbonate environments is
23:06 we know are fizzy graphic setting. ? We used to have satellite photographs
23:12 air photographs. Now we have right? We have google. There's
23:17 reason for you to not know where at. On a carbonate environment in
23:22 car on a carbonate platform. And for that, for that environment of
23:27 . Right? We can evaluate the depth. Right? And these carbonate
23:32 . Water is crystal clear. You see sometimes hundreds of feet underwater.
23:37 . So you'll know if you're in few feet of water depth or you're
23:40 ft of water depth. You can your tongue out and evaluate water chemistry
23:44 obviously we have tools to do that . To evaluate the saturation state,
23:49 alkalinity of seawater, the ph of . All these controls that might influence
23:56 . Either from a physical chemical standpoint from a biological standpoint. You'll know
24:01 energy of the setting, right. it's quiet water setting or whether it's
24:08 related to breaking waves or whether it's related to two too strong tidal currents
24:21 things like that. Okay. And you can evaluate the substrate. You'll
24:25 if it's a rocky bottom. You , if it's a sandy substrate of
24:28 substrate. That's important control sometimes because governs the kinds of organisms that can
24:34 in those environments. You can evaluate starting porosity and permeability. I showed
24:39 that data last weekend right from the is in florida. And then you
24:43 evaluate the sediment for starting meteorology and gives you information about the digest
24:49 Right? We talked about how important was from a digestive standpoint. Uh
24:55 saturday. Right. And at the time you can see what kinds of
24:59 attributes are forming in those environments. can collect sediments, you can punch
25:05 in and take samples, you can the texture whether it's gonna be
25:11 stone prone pack, stone or wacky prone, You can look at the
25:15 , right, the diversity of the types. You can look at the
25:19 structures. I think I showed you we extrude those cores and open them
25:23 to see sedimentary structure. You'll see of this probably. And then we
25:28 shoot high resolution seismic in the shallower to evaluate geometry and orientation. That's
25:35 beauty of working the modern. Basically you can see what's being produced
25:39 you can see what the key controls for that style of deposition.
25:44 And that's really what you need to . When you go back to the
25:47 record, What controls the occurrence of of these different faces. Okay,
25:53 go to the rock record. What you have to work with?
25:56 You have maybe some core data, some seismic data where you can get
26:01 information like this. Now we have work backwards. Right? We have
26:05 start with this and try to figure where we were right? Trying to
26:09 what the key controls were and we a better job of that now,
26:13 of comparative sediment ology. Okay. that's why I'm going to spend all
26:18 time in the next few days talking these modern environments. So you appreciate
26:23 setting. You appreciate the key You appreciate you appreciate the sedimentary geo
26:30 that evolves. Right? In terms its thickness and orientation and stuff like
26:35 . Then we'll take that information and it back to the rock record.
26:41 , so there's some general factors here influence carbonate settings. The first is
26:45 hydra graffiti. Okay, and you know, today we're dealing with
26:52 oceanic settings for areas like the Right? These are shallow water carbonate
26:58 surrounded by these deep water settings. ? So were mostly influenced by oceanic
27:03 . And what are the oceanic Their oceanic swells? Right. The
27:08 period waves that are generated on another of the basin by storms and they
27:13 across the basin and they strike the water setting on the other side.
27:19 . And the other oceanic influence will tidal currents. Okay. The day
27:23 day tidal currents which in the caribbean are what we call semi diurnal
27:30 They operate every 12 hours. And uh yeah, I get the
27:37 come in tides go out but before go back out, there's a lag
27:41 of about an hour before they Right? So that's called slack tide
27:46 water doesn't move and then it goes out. The flood, tidal currents
27:50 always stronger than the so called tidal . Okay. And then the other
27:57 we have today would fall more into , a integrate tonic basin, more
28:04 depression. Uh Our modern analog of is the Arabian gulf. Ok,
28:11 isolated by the straits of Hormuz from indian ocean and the circulation is a
28:19 bit different there and we'll talk about as a separate model later tomorrow but
28:24 realized I mentioned the the big broad continental or so called the pirate
28:30 Uh, those existed the lower for example, during the or division
28:35 we had our deficiencies, basically covering of the US Creighton and then we
28:41 the same sort of thing for a of the upper cretaceous. Right?
28:45 big epic Connell sees that extended from the gulf of Mexico all the way
28:50 to Canada. All right, so have to keep that in mind when
28:54 thinking about some of the key controls deposition. Alright, then of
28:58 the second key controller influences the seaport . So that's our two embalmer models
29:04 something in between. Right, change slope angle a little bit. It
29:08 the story just a little. but we have to talk about the
29:12 member models and that's what we'll talk and then the last influences the
29:18 And again, you know, historically used to think in terms of climate
29:22 from the standpoint of rainfall, humid Aaron, Right? No evaporates associated
29:29 humid setting. Lots of evaporates associated the arid setting, but climate also
29:37 the prevailing wind systems. Okay. that's what we try to work out
29:43 the knowing our global setting, Using the paleo geographic maps to guide
29:48 . But then proving the trade wind from the geology and that's what I'm
29:53 to try to do in our discussion the next day and a half.
29:57 , show you when we get into trade winds systems how the orientation of
30:01 sand bodies and things like that prove that the trade wind influence.
30:08 so this this diagram here is sort a catch all cartoon that illustrates potentially
30:15 all the major carbonate systems we can from shallow water out into a deeper
30:21 basin. And you'll see this again we talk about play types because theoretically
30:28 along this deposition profile, you can a carbonate play type, but it's
30:34 dependent. Okay. Because some of organisms don't exist in every geological time
30:39 to to create a play along this profile. Alright. But basically you
30:45 see there's potential for plays developed out the basin. Their potential for shutting
30:51 material from the shell water platform into water, things like turbine sites or
30:57 flows, things like that. You the potential to develop these deeper water
31:02 . Sometimes called pinnacle reefs or sometimes lower, low relief buildups. But
31:08 , that's age dependent because some of organisms can't do this every geological time
31:14 . And then sometimes you can plaster up along the edge. These are
31:18 on lapping wedges. I was talking where you can get play potential there
31:24 on the composition of those wedges. right. But historically most of our
31:29 of our shallow water carbonate deposition obviously up on the platform. Mostly.
31:33 going to see that most of our plays that we chased historically in industry
31:39 up on the carbonate platform. so from the platform margin to the
31:45 interior and this is uh the setting you can get either along the platform
31:53 the classical barrier reefs, right? linear continuous reef systems that track the
32:00 margin. So thank great barrier reef Australia. And then if you don't
32:05 the reefs, what can you get the margin? You get the high
32:08 analytics sand bodies historically due to strong current agitation because that's where you have
32:15 currents. They tend to be focused the platform margin. Alright, And
32:19 when you get away from the platform , the platform interior, you're gonna
32:23 that depending on the setting, you have widespread sheets of carbonate mud or
32:28 sands. This is where the trade influence could come into play. This
32:32 also controlled by the depth of the material. If you have pre existing
32:37 , you can create isolated small scale complexes back up on the platform and
32:43 closer to a land mass represented by pink, you can get either tidal
32:49 or beaches developed in a more platform setting. Okay, so there's a
32:54 of potential here, but you you gotta you gotta understand what controls
32:58 occurrence of distribution these different environments and is their play potential, right?
33:04 to get a better get a better on that, we start with the
33:07 just to show you what the environments deposition are like, what are the
33:12 of these environments. And then, know, we'll translate this later to
33:16 type because the play type is not one environment, right? It's an
33:20 juxtaposition of potential reservoir rock source, trapping or sealing faces. Right?
33:29 so you have to think in those when you're trying to extrapolate to play
33:35 . Okay, so what we're gonna for for this initial discussion here is
33:40 gonna just focus in on the deeper . Part of the story here and
33:45 just gonna spend a little bit of here talking about basil environments And then
33:49 four soap environment. Because I want focus most of our discussion the rest
33:55 today and part of tomorrow, up the carbonate platform itself. Okay.
34:00 about these different classical sedimentary environments. then we'll come back and put it
34:05 the context of the end member First for the steep margin platform and
34:09 later for the carbonate ramp model. , let me just make a few
34:14 here about the deep water settings to you to think about some of the
34:18 controls on baseball deposition and then the slope and believe it or not.
34:24 of these environments have played potential. , but it's it's dependent on the
34:30 of the carbonate and it's depending on other factors as well. Usually die
34:34 but but there is play potential for deeper water settings. So what I'll
34:41 I'll do for this discussion is we'll we'll sort of work backwards.
34:45 So you see the picture of this from the Devonian in Western Canada and
34:52 see the label with the depth of , the present day depth of burial
34:58 meters. And do you all know T. O. C. Is
35:00 I ask you this before? O. C. Is total organic
35:04 ? Right. This is a proxy a carbonate rock to yield hydrocarbon if
35:10 gets mature enough. Right, it the buried to the right temperature and
35:16 8% T. O. C. very high. One or 2% is
35:20 to be pretty good source rocks. 8% is almost world class.
35:25 so let's in in the rock record , I'm telling you this is a
35:32 of limestone. Okay, so we to sort of work backwards from the
35:36 fabric to sort of understand what was nature of the deposition environment.
35:41 so you know it's relatively deep because told you it's baseball. Okay,
35:46 know the H devonian. Alright, I guess the first question is to
35:53 where did the settlement come from? where would you get all this fine
36:00 carbonate mud or muck right in the , anybody remember the ways to contribute
36:09 mode that was on your quick, was on the quiz. Right.
36:20 you can locally produce it. And we talked about some of those
36:26 , right, breakdown of cal curious breakdown of of skeletal material by by
36:33 . Right. And what else did see in the, what's another way
36:41 the, in the Mesozoic and Remember those pelagic nano fossils? The
36:50 , golden brown algae. Right. little things are just a few tens
36:55 microns across that you can't see in fence section. Looks like nick.
37:00 . But a skeletal in origin and stuff dies and breaks down and contributes
37:05 the fine mud on the sea That's great in the, in the
37:11 and tertiary, but this is they didn't exist. Okay, so
37:19 don't have any ready made source of grained carbonate material in a paleozoic baseball
37:28 . Like that lives in the water . Okay, so where does this
37:32 have to come from? There's nothing in the basin that has to come
37:42 where? Hey Jason platform. Your factories, your shallow water
37:50 Okay. And then you've got to it out there. Right. So
37:53 do you get it out there? get out there by major storms.
37:59 , storms. Put this stuff in the day to day title action draws
38:04 stuff off in the deeper water and what happens? It just settles
38:09 Right. And so look at the structure here. These are the planer
38:17 lamination is right? We talked about the first day. This is the
38:21 out effect. Right stuff is in and then it just settles out to
38:27 this classical millimeter scale horizontal lamination. , finally, Okay, there should
38:51 and there should be a lecture 10 slides and lecture town for the steve
39:02 for the platform Would be be a 10 for with the text. And
39:10 there should be a lecture 10 for carbonate ramps that we'll get into
39:24 Okay, so you see the implications . Alright, if this is settled
39:29 , right, this stuff is coming the adjacent carbonate platform. This is
39:33 to affect the geometry of your base fill. So you would expect to
39:39 the basil succession thickest up against the platform. Right? If this is
39:45 hand, is is the carbonate right, dropping off the deep
39:50 The basal succession is going to be thicker. Right up against that
39:55 And then what's going to do? gonna thin to a feather edge as
39:59 go out into the basin. As you get further and further away
40:03 the source, everything thins out. ? So that's the classical geometry of
40:08 basin filled carbonate in the paleozoic because dependent on sediment source from that carbonate
40:17 . Alright. And so that's important appreciate, especially if you think that
40:23 ends up being your source rock? . Right. In terms of how
40:27 volume of hydrocarbon you could generate, going to be dependent on the geometry
40:31 that material. Right? And why we know that this has good source
40:36 potential because of the high T. . C. All right. So
40:41 turn this around and ask the Well why didn't this stuff get
40:46 Why is it dark colored? Why it organic rich? What had to
40:51 the nature of that environment of Well, definitely low energy because it's
41:01 it's dominated by this MMA critic But what's the other part of the
41:07 here? What's the nature of the quality? Is it oxygenated? Is
41:18 burned? So why wasn't an Why wasn't it burrow something had something
41:30 to happen to the water quality? . Right. We had this conversation
41:37 little bit last week. Right about when we're talking about sedimentary structures
41:43 To preserve stratification of carbonate rock. are only two ways to do that
41:48 high energy, right? Where organisms want to live the burrow because they're
41:54 get sandblasted or they're gonna get their are going to fill in all the
41:57 with sand, Right? Or to in a situation where the water quality
42:03 so poor that nothing can live And so if it's that's obviously not
42:10 energy? Right. So what are left with your left with a situation
42:14 the water quality is so poor that though soft body borrowing organisms couldn't live
42:22 . So what are the two ways do that anybody recall? Take away
42:33 oxygen Right, create anoxia, Where the oxygen level is so low
42:41 even worms can't live there. So there's no burrowing and that's how
42:47 preserve a fabric like that. So in the absence of evaporates,
42:54 fabric is created by an oxy at time of deposition. Okay, oxygen
42:59 so low that there's nothing living on sea floor this cal curious there's not
43:05 soft body burrowing organisms. Okay. there's nothing that nothing to destroy the
43:12 material, Right? If there's no , they can't eat it. If
43:16 no oxygen oxygenated seawater can't destroy the material either. Okay. So the
43:26 the only other way would be to the salinity right? To create hyper
43:30 conditions. But usually when you do , you start to pick up some
43:34 that bright minerals and things like You might see little gypsum crystals along
43:39 bedding planes and things like that. . Which has not been described for
43:44 , but has been described for other on lime stones. Okay. All
43:49 . You see the game we're playing . We're trying to work backwards
43:52 We're trying to get an understanding or , Right? So the combined dark
43:57 , the combined high T. C. The combined preserve stratification,
44:03 predominance of fine grain. The This is basically a lime mud
44:07 right? has less than 10 Sand grains. Well less than 10% sand
44:14 grains. And and it's all right . Right? That's the line mud
44:22 . Alright. So tell us something the environment deposition. Alright. So
44:30 is this is sort of the mentality want to start trying to develop thinking
44:35 terms of how we use attributes of rocks to backtrack out and figure out
44:39 setting. Right? And then the is important because it controls the the
44:45 right? Knowing that this stuff is locally produced in the water column has
44:50 be coming from the platform. It's going to show the soft lapping wedge
44:56 basically disappears into would be a shale . Okay, so so that's the
45:05 , right? And then here's another on limestone from the upper cretaceous.
45:11 Again, you need to appreciate when get into the Mesozoic, especially starting
45:16 the upper Jurassic. This is when start to evolve the pelagic or plank
45:24 microfossils and nano fossils. Right? those are the foraminifera but they make
45:31 make little sand sized grains right? are a few 100 microns across,
45:34 would see those in the sediment. the mud producer now would be what
45:40 be the golden brown algae that produces little armored ball structure called? The
45:46 sphere. It's made up of those armored, it's armored uh features,
45:53 ? The little plates, the plaster their armored structure? Those are called
45:59 lists. But there are less than microns across for scale. Right?
46:04 then when the cocoa sphere disintegrates or eaten, it breaks down into little
46:09 that make up the sediment. So in this example, What do
46:15 see here? We see a lighter . You see the T.
46:19 c. .1%. Which means there's source rock potential. And then you'll
46:27 what those were. Right burrows. the borough structure of the shrimp.
46:36 . So what's different now about the setting compared to what I just showed
46:43 from the devonian? Yeah. Right. Like that's more oxygenated.
46:53 ? It has to be to explain burrowing to explain the reduction of the
47:00 material in that environment. Because all these environments, every one of these
47:05 environment starts off with a ton of material, either tied up in the
47:10 bodies of the organisms that live there tied up in the skeletons of these
47:15 that live there. All right. the fact that you're down 2.1% tells
47:21 that you've consumed that organic material. the organisms that burrow have directly eaten
47:27 or they brought in oxygen oxygenated which they've clearly done here to create
47:33 oxidation halo that you see around the structure and that destroys the organic
47:39 Okay. But then think about you where does the sediment come from?
47:46 . So now you have the potential generate in two different places. Now
47:51 can do it locally from the water . As you remember the distribution of
47:57 plastic microfossils and anna fossils there in upper part of the water column,
48:01 in deeper water. Okay, I you the the microfossils, the
48:07 the calcite spheres that are floaters live this belt from about 20 m to
48:13 m. Okay, The average water is 80 m. That's where they
48:19 . But when they die they can down into hundreds of thousands of feet
48:24 on the depth of the basin. , so some of the stuff is
48:28 breaks up this rock came from But then there can also be introduction
48:32 material from the adjacent carbonate platform. ? Because every carbonate basin is linked
48:39 a platform or a ramp. So there's gonna be stuff shut off
48:43 that too. That mixes in. right. So when you look at
48:49 when you look at the fence you see the evidence of the pelagic
48:56 . Right? Those are the never more than about a millimeter across
49:01 scale, but you would definitely be to see these even with a hand
49:05 and core. Okay. But then money matrix that you see here is
49:11 by the co colas which are the product of cocoa sphere in which the
49:19 brown algae lived. Okay, so an important part of the story.
49:25 , now that doesn't mean that some that Mick. Right. And other
49:29 of material can't be a lock thinness this environment shut in. Okay,
49:34 can be right. But I think see the implications now for the geometry
49:40 the basin fill. Remember in the it's up against the platform, it's
49:45 . Does this? But think about and tertiary age basin, if these
49:51 occur all the way across the Right then the geometry is more sheep
49:57 . Okay, so typically in a or tertiary h basin are basin fill
50:04 more sheet like and not wedge like out nothing into deeper water.
50:12 so that's the that's a sort of common characteristic of a lot of these
50:16 basins. Alright. More widespread because have this ready made source of sediment
50:22 the water column. Alright. And would be the only thing that would
50:26 limit that the either water death. . Where it got so deep the
50:33 material dissolved out before it got to sea floor. Right. Remember that
50:40 compensation. Death we talked about the day or what else would limit the
50:47 of these organisms? They're golden brown . What do algae need for living
50:58 ? Right, so how would you sunlight in a marine environment but they
51:06 live in deep water. Remember? live in the upper part of the
51:09 column. 22, m. So would you limit light penetration there?
51:25 water? How would you do I can hardly hear you because there's
51:31 much noise here from the not turbulence and that would be due to his
51:45 . So that usually operates in deeper . Okay, remember we're still up
51:49 in the upper part of the water . So think about you get around
51:54 Mississippi River or something like that, ? You've got rivers pumping fine grain
51:59 offshore, right? That persistent influx fine grain clay is gonna cloud up
52:05 water column. That's gonna shut down penetration. Right? That's gonna kill
52:11 . That's gonna eliminate these guys. , So there could be basins in
52:16 rock record where one side is a of carbonate production in deeper water by
52:22 . Right? But if you have big river system on the other side
52:26 out classics all the time, like amazon or the Mississippi River,
52:32 then you're not going to get this of deposition, you could have an
52:35 . Okay. But normally in the record, especially with the shallow integrate
52:41 basins, we tend to see more distribution to the to the basic filled
52:47 and Mesozoic and tertiary age sequences. , alright, so this is where
52:54 always need to be thinking about the , Right? I told you
52:59 Graphic age is such a key control because it determines who the players were
53:05 where they, you know, where live. And then you got to
53:08 about what controls their occurrence and And then the other part of the
53:12 is what they're starting. Meteorology. . That's important from a porosity,
53:17 genesis standpoint. Okay. Alright, let's go through one more example here
53:23 we're gonna take a little short break . The the when you come up
53:33 to a platform setting represented by the in this diagram. All right.
53:42 What influences do you start to Alright. In deeper water? Not
53:47 do you have the potential for in pelagic carbonate deposition like we've been talking
53:53 . And for this discussion for this , let's just assume that the the
53:58 hair represents our background pelagic carbonate Okay, but what happens is you
54:04 closer and closer to the platform, start to see the influx of material
54:10 from that platform by major storm processes by trade winds. Okay, and
54:18 you start to get this inter mixing here, which is represented on the
54:23 by the gray and then the blue orange material. Okay, so in
54:30 deeper part of this succession on the here, the blue here represents the
54:35 grained material that gets swept off the platform. Either by periodic storm
54:42 And when we talk about storms, talking about winter storms or hurricane scale
54:48 activity. Okay, so winter storms related to the cold fronts that comes
54:54 the continental U. S. And usually those winds blow on the
54:59 of say 25-40 Miles an hour. ? But sometimes they can get
55:05 right? Sometimes you can have a of a day where they blow up
55:09 70 mph. All right, So kind of energy Then, of course
55:14 hurricane, right? Where you to get up to over 150
55:20 right, blowing for days on So we're gonna talk about hurricane effects
55:25 later. But that's the kind. we talk about major storm activity,
55:30 talking about this combined effect of the winter storms or cold fronts.
55:37 And every year we get 40-60 of that come through the continental us,
55:42 they go offshore into areas like the Bahamas versus the more ephemeral hurricane,
55:51 ? Which may not strike an area 15 or 20 years and then just
55:57 it in one event. Okay, . So appreciate as you come up
56:02 and closer to the platform margin, happens to the scale of the material
56:07 being shed gets coarser and coarser Okay. And that what's the other
56:15 here? The other control here you know, what's being produced along
56:19 margin. And where is this stuff from? Right. So, you
56:24 , in the world of classics, tend to think most of our shedding
56:28 during low stands. I think we this discussion last weekend. Right?
56:33 most people, most people were expect most of the coarser grain stuff
56:38 come off during a low stand and expected to be shed out through a
56:43 canyon. Right, So point sourced , but in carbonates, I told
56:49 last weekend and I'm going to reiterate today and tomorrow. Is that most
56:54 the shedding is high stand? When the platform is flooded, that
56:59 anywhere along this platform margin, potentially can shed material into the deeper water
57:06 . So we call that the line instead of point sourcing. Okay,
57:13 that's the norm for carbonates. And then don't don't assume that stuff
57:19 comes from the margin. Hurricane can stuff up well inboard of the platform
57:25 and bring it to the edge and into deeper water. Okay, so
57:31 not everything comes just from the Alright, And then what's the other
57:35 of the story here, is that you shed this stuff out into deeper
57:41 , you can do what we call the sequences. Right, So,
57:47 storm throws carbonate sand out into deeper erodes that muddy substrate and puts the
57:54 on the sea floor. Right? sand. And then when the storm
58:00 , you get a mud drape on of that. The next storm event
58:04 out, brings the stuff out and what it erodes the mud drape and
58:10 of the sand and put sand on And you do this for a
58:14 what do you start doing? You these thicker sand packages. Okay.
58:19 you end up with these thicker, 10, 20 ft there, and
58:26 gonna show you some examples of reservoirs are a few 100 m thick of
58:31 sand. Okay, That's not one . That's multiple storm events.
58:37 And that's what we call amalgamation. , so that's what we expect to
58:41 as we get closer and closer to platform margin. Okay. And then
58:48 , in the world of carbonates, of our, the most common processes
58:54 operate along this four slope setting if you're dealing with reefs, it's
58:59 to be the rock falls where the actually built to the edge, then
59:03 actually spall off and you get big of reef material shed into deeper
59:09 And things like earthquakes probably play a in that. But it could just
59:13 uh, you know, again, storm effect or something like that,
59:17 breaks some of the step off and debris flows. Right, because most
59:21 the material that makes up a reef the skeletal fragments and then the grain
59:27 are normally associated with the, the energy carbonate sand bodies that tend to
59:33 along a platform margin. Okay, here's one last example here. This
59:40 maybe some of you have seen This is on the highway driving up
59:44 El caso to Carlsbad in New And this is a famous raider
59:51 separate Permian aged the background sediment. tan sediment here is actually plastics,
59:58 are silt stones and fine sand but then you see these larger blocks
60:03 gray material and some of this is from the Some of this is coming
60:10 the Permian reef complex, sometimes miles . I mean this actually this,
60:16 outcrop is about 10 miles away from platform margin. Okay, so this
60:21 picks up steam and rolls out into water. Sometimes it's uh other kinds
60:27 carbonate sediments that were accumulated along the margin. It got pushed off by
60:32 or some other mechanism. Okay, you started to get the impression here
60:37 the process here about how your creating environment to shed carbonate material into deeper
60:43 . And that can be blocks of drive material which can be big enough
60:48 to actually have reservoir scale quality or can be sheets of material that are
60:53 brought out in the deeper water. , alright, so, and
60:58 the timing mechanism, as I is for the reasons we talked about
61:04 a digest perspective last week is in , it's Hiestand shedding on the right
61:11 is flooded machines going full blast. is when hurricanes or the stronger trade
61:17 shed persistently shed material into deeper water create the on lapping wedges that have
61:24 reservoir potential. You drop sea you shut off your carbon machine.
61:28 is when you get the car the dissolution the segmentation, But that's
61:34 good for shedding material into deeper Right? So usually the carbonate story
61:40 180° out of phase with the classics . When you tend to shed most
61:45 your course of green stuff during major in sea level. Okay.
61:50 And I'll prove this to you. Tomorrow I'll take you through and show
61:55 the data that proved this relationship back the early 80's and now been replicated
62:01 at least four or five different uh baseball settings. Okay. Alright.
62:10 any questions about the the deep water of the story? That's all I
62:16 to say. Right now, we'll back next weekend and I'll talk about
62:20 play potential for both the basil environments the four soap settings. I'll take
62:25 through case studies. So you get feel for how these things are put
62:29 and what kind of potential they have to yield hydrocarbon. Okay.
62:38 I think let's take a let's take an eight minute break here. So
62:44 go to about 3 15. We'll a break and then we'll come back
62:48 work the shallow water part of the . Alright, Starting along the platform
62:54 today and then tomorrow we'll pick up the platform interior. Okay. All
63:00 . You tie. Let's take a . Okay, I'm gonna I'm gonna
63:08 to use this laser pointer. I know how well you guys can see
63:12 on the screen, but maybe you see it better on your computer.
63:16 is good. I appreciate that. , because I know you online can't
63:24 see what I'm pointing to on on screen here. So let's try this
63:28 see how it works. Uh So gonna jump up now onto the talk
63:34 the different sedimentary environments that typically occur the shallow water carbonate platforms like we
63:41 in the Bahamas uh today. And we're gonna focus for the rest of
63:47 on the platform margin. Right? the Bahamas are facing an open
63:53 the atlantic ocean, they're influenced by conditions related either to oceanic swells or
64:01 tidal current agitation. And so I'm talk about the two environments. We
64:07 get along the margin will start first the carbonate reef for plat barrier reef
64:15 we'll talk about variations on a So you appreciate how the settings influence
64:20 characteristics of some of these recall And then we'll finish up by talking
64:24 analytics sands first from the northern Bahamas they are dominated by strong tidal current
64:33 and then I'll take you to the Bahamas keiko's platform and show you there's
64:38 way to make you. It's related the strong easterly trade wins.
64:43 Has nothing to do with tidal And actually, I think that model
64:48 sand deposition has greater applicability to the record. Alright. So We need
64:58 first talk about sea level, You need to appreciate what sea level
65:03 been doing for the last 18,000 years least. Alright, So 18,000 years
65:12 , sea level was about 120 m than it is today because of the
65:19 of the glaciers. Right? When glaciers expand, you you draw down
65:26 levels and when they melt, obviously sea level comes back up,
65:32 And we've had these major ice related level changes in the place has seen
65:37 the last two million years. And I want you to appreciate What we're
65:44 about here. Okay, so let's back 200 To 18,000 years ago.
65:51 120 m lower. All right. when the the glaciers have expanded,
65:58 ? There's a mile thick sheet of on top of Chicago where Chicago is
66:03 . Right. And then it melted sea level started to come up.
66:08 we used to think, you know the sea level rise was just
66:12 It would just come up uniformly from to where it is today and shall
66:17 this flood our carbonate platforms. But in reality we appreciate now that
66:24 doesn't do. That is one continuous sea level as we melt the
66:30 It actually occurs in pulses. And you see the boxes highlighted here
66:36 red. So when the glaciers would , sea level would pop up.
66:43 ? And then there'll be a pause when you get a pause, that's
66:47 you got carbonate deposition. And then sea level pop back up again and
66:52 down your shell water carbonate machine for period of time until you positive level
66:59 , it could catch up and start up the whole. Okay, so
67:03 is more typical really of a lot responsive carbonate shell water carbonate deposition to
67:09 sea level changes related to this glacial static uh influence. Okay, we
67:15 do it as one uniform change in level. We do it in
67:20 Right, boom, pause, boom . All right, that's the way
67:25 works. Okay. And this has well documented now in a number of
67:30 in South Board in the Bahamas, people have been able to track these
67:34 sea level changes and actually date them of the pizza. Come along with
67:39 of these sea level changes. They radiocarbon date the petes and get a
67:43 for the age relationship. Okay, here's three little three suitable curves from
67:53 different parts of the world here for last 7000 years or so because
67:58 most of what I'm going to show in the Bahamas and even in the
68:03 Gulf dates out in less than 7000 . A lot of it's just 3
68:08 5000 years of deposition or less. right. So you can see the
68:14 plots here meters for water depth years and thousands of years again. This
68:23 based on Radiocarbon dating, which is to, you can take radiocarbon dating
68:29 at least uh, 20, Okay, so south florida, sea
68:36 curve right? Which we think is for What I'm going to show you
68:39 the Bahamas, You can see where were 6000 years ago were about six
68:46 below present day sea level sea level been coming up very quickly. I'm
68:50 to show you the details of this little bit better in a minute.
68:54 then what happened about 6000 years The rate of rise started to slow
68:58 . Still coming up at a pretty rapid rate to about 3300 years
69:03 Then it started to slow down even Where it stayed like that until about
69:09 years ago. Okay, and now rate of rise is picked back up
69:14 more like this part of the profile the last 120 years. Okay,
69:18 that's florida and the Bahamas, great reef on the right here. You
69:24 see where it was 7000 years About six m lower. Shot straight
69:29 to where it is today And it's there for the last 6000 years.
69:34 , completely different sea level history. right. And then here's brazil.
69:44 is actually bottled on dated, on relationships, not carbonates, but it
69:50 you a feel for what's going on . So 7000 years ago, less
69:54 four m of water depth. And you can see about 5500 years
69:59 it shot up to four m higher it is today. And then it's
70:03 falling ever since. Okay, so know what happened to this concept of
70:09 static sealable prize? The next on on back in the 80s.
70:16 The next on talked about internally this used to used to see right sea
70:22 changed the same everywhere. Right? was their concept. Yeah. There
70:28 be a change that's uniform everywhere. what else is part of the
70:33 There's a local tectonic for environmental influences on that. Right? In order
70:41 explain something like you see here. ? Because it's not the same
70:46 I mean, this got shot down quickly when they published this paper when
70:50 published their so called you static sealed back in the 80s. Right?
70:57 not just used to see there's a tectonic and subsidence effect. Okay,
71:03 to explain the difference between south florida great barrier reef. And then clearly
71:09 explain brazil. Right, What's the for brazil? There was a mile
71:14 ice sheet on top of land. . And what happens when you melt
71:21 ice? What does land do? rebounds? Right comes back up,
71:26 take off that that thickness comes back . That explains why sea level started
71:32 because Brazilian land masses rising. so we wanna be thinking obviously in
71:41 of relative sea level, right? use static. Every basin is influenced
71:48 relative changes in sea level, incorporating use static component obviously. And then
71:54 local tectonic and subsidence a fact. , so let me take the south
72:02 curve here and break this down to little bit more detail. You can
72:07 where we put some rates to the the different parts of the sea level
72:12 . So again this is just Back years ago and you can see The
72:21 years ago. Sea level is still below 10 m deeper than it is
72:27 , shooting up very quickly. We started to melt the glaciers so
72:31 levels coming up very quickly. But still doing it in this post fashion
72:36 we talked about But faster means greater 50 cm per 100 years rate of
72:44 . Okay, I mean that's a a meter to a meter per 100
72:49 rate of rise. Imagine if we that here on the texas gulf
72:56 Oliver wouldn't exist. Alright, Bolland be underwater. Alright. And then
73:03 rate of rise slowed down to 23 per 100 years rate rate Until about
73:10 years ago. Then it slowed down four cm per 100 years rate of
73:15 . And that stayed that way until years ago. And now we're back
73:20 this part of the sea level Alright, so sea levels still coming
73:27 . There's no question about that. right. And this is not
73:30 This is tide gauge data. All . From New York to Miami.
73:36 , for the last 220 years. this is physical data, not somebody
73:42 what they think sea level is going do. So, this is not
73:47 news if you own a condo on Beach. All right, sea level
73:51 still coming up. I don't know you're familiar with Miami beach,
73:55 They talk about the king tide every , every spring, high tide right
74:00 the moon is in phase? Full . Right? You get the extra
74:05 of the moon, you get another foot of water associated with high
74:11 Okay, So what happens downtown Miami ? They get a foot foot and
74:16 half of water and some of these think it's cool to run their Ferraris
74:22 this. Right. What a stupid . Right to run your car through
74:26 water, but they think it's really . But the beachfront, the storefront
74:32 don't think it's very cool. They have to put sandbags up against
74:35 buildings to keep the water out of stores. I mean this is a
74:40 . Okay. I mean and the why I'm bringing this up is because
74:45 gonna show you stuff tomorrow that I is better understood. If you think
74:52 the fact that sea level is still up. Okay. So we need
74:55 keep that in mind. I think can see how some environments,
74:59 Like reefs and sand bodies accumulate pretty . They could probably deal with 23
75:06 per 100 years rate of rise. ? They could keep up with
75:09 But what about some of these other water settings? Now they're gonna get
75:13 gonna get drowned out even by this of rice. Okay. So you
75:18 to keep that in mind for our here for today and part of
75:23 Okay. So what we're gonna do we're gonna get into talking about platform
75:31 reefs that develop along open ocean sides these state margin platforms like the
75:38 Right, This is a very common of carbonate deposition all through geological
75:44 The organisms that make up the So are depending on the strata.
75:48 age. Right today, They're all . Right this cartoon in corals which
75:53 the magnetic corals we talked about last but back in the rock record they
75:59 things like rubio's corals for tabular corals are more cal citic. Alright.
76:07 they create what we call buildups. . So there's this term build up
76:12 the carbonate literature. Something that involves on the sea floor. Okay.
76:20 then people break this term build up two types the reef, the actual
76:26 build up. And people use the bank or mound. So what's the
76:33 A reef is a build up that has at least some evidence of frame
76:39 organisms. Right? You can see evidence for in situ orientation.
76:43 We talked about the term frame Right? And so you want to
76:51 evidence for that? You want to stuff intertwining growing together, creating some
76:55 of topography on the sea floor. those things are gonna obviously try to
76:59 up towards sea level. All compare that with what people use where
77:06 use the term bank or mound. a build up, but it lacks
77:11 frame building organisms. These are usually MMA critic kinds of build ups.
77:16 are these so called baffle stones. talked about where more delicate things,
77:23 or plating things like fileted algae trap . Right? But they don't create
77:28 rigid structure. Okay. But they build topography on the sea floor.
77:34 . The one is high energy. ? And one is quiet water.
77:40 ? The the these these once it the frame building organisms are usually quieter
77:47 . Usually in deeper water, but always. Okay. Where they accumulate
77:52 muddy matrix. Alright, so simple is if you're in the caribbean,
77:59 ? You uh you've had a long in the oil and gas business.
78:03 taken your you got this big retirement and you've cashed in and you've got
78:09 sailboat, you're sailing around the If you hit a reef, you're
78:14 know you hit a reef, Because you're gonna put a hole in
78:16 sailboat, you're gonna destroy it. , So that's the concept of the
78:22 reef, right? These are frame . But if you hit a mud
78:26 or a mud mount, right, lack the rigid structure. You're gonna
78:31 stuck in the mud during low but you're not going to damage your
78:34 . Alright, So, it's a simple concept here. And we're gonna
78:38 talking about the reefs right along these energy, open ocean platform margins.
78:44 is where you develop the high energy systems, the frame stones and associated
78:51 that make up what we call a reef. Okay, so let's spend
78:57 time talking about the model, then take you through two areas, one
79:03 the western caribbean to start, that's police reefs. Okay, And share
79:09 you the nature of the caribbean reach , and then I'll take you to
79:14 to the great barrier reef and believe or not, it's a jump in
79:19 energy, a dramatic jump in energy those two systems, and I want
79:24 to appreciate how the energy translates into influencing the character of the reef.
79:30 , so you need to appreciate how organisms respond to the energy. What
79:35 of refill system you're going to preserve the in the rock record. All
79:41 , so I drew this diagram dila straight at any one point in
79:46 where you develop the reef. Obviously it's along the platform margin and
79:53 drew it right at the inflection point you drop off into deeper water.
79:57 interesting that both examples, I'm going show you are not in this position
80:02 now, because of the way sea came up over the older Pleistocene
80:08 The rate of rise was too great initiate reef along the inflection point.
80:13 had to flood the platform And the . What that means is the reefs
80:18 start back one or two km behind true drop off of the platform.
80:24 . Okay, so both great barrier and police reefs are in that position
80:29 now. Which means they're gonna do they're gonna build out eventually to the
80:34 . Right? They have some space build out our pro grade to the
80:39 before they get to deeper water. , But for this discussion, I
80:44 it, like you see here. , and so the barrier reef is
80:49 up always of two components. The that you see here is what we
80:55 the re front. This is the . This is where you get the
81:00 amount of in situ frame stone Okay. And it turns out to
81:06 relatively narrow at any one point in today. It's only a few 100
81:11 across for scale. Okay. The of the so called reef that people
81:17 is actually debris and some of that is thrown out in front. This
81:23 what people call the slow paper and four. So paper. Okay.
81:28 then some of it is thrown behind that's what people call the bakrie
81:34 All right. So they're all there's debris shed off of that re front
81:38 major storm activity and its only major that break up the reef.
81:46 Day to day. Breaking waves do break up the reef. Okay.
81:50 the storm surge and we'll talk about that actually does these reefs in.
81:56 . Now, it also turns out most of the shedding for these open
82:02 platform margin re systems is not into water. It's up onto the
82:08 Okay. You would think it would into deeper water, but actually most
82:13 the energy comes out of deeper water pushes the stuff up onto the
82:17 Okay. So you're gonna see data shows you that on a open ocean
82:25 system, right that faces the open , which almost always means it's also
82:30 into a prevailing wind, right? the wind accentuates the the circulation
82:36 Most of the shedding is not into water. It's stuff that gets thrown
82:40 up behind the reef to make the flat. Okay. And it actually
82:46 on the leeward sides of these platforms you shed most of the material.
82:52 , So in this model, the flat is 1-2 km across for
82:59 That's 10 to 20 times wider than orange belt at any one point in
83:04 . Okay. And all that stuff generated almost entirely by major storm
83:11 tearing the reef up and throwing it . Okay, Of course. There's
83:16 local production here because there's some stuff can live on the reef flat,
83:20 ? Encrusted corals and red algae and calculus allergy that produce locally cetera.
83:26 most of this material is derived from breakdown of the orange re front.
83:33 . Now, I think you can , right if you're along the platform
83:37 , if your back further in a material setting, which which environment is
83:41 competent? It's the reef. In terms of producing more sediment.
83:46 what's going to happen through time? ? The reef margin is gonna create
83:51 faster than the back reef lagoon. ? And that's gonna create this topography
83:56 you see illustrated here, where you from the rim of the reef,
84:01 ? The shallow part of the reef slightly deeper lagoon. Back here in
84:05 yellow, Right? And that defines transition from reef margin, tobacco reef
84:13 . Right? There's always going to that topography created because of the differential
84:18 the rates of sedimentation between those two . So what do you get in
84:22 back reach again? Well, you local sediment production from anything that lives
84:27 . Right. Scattered cal curious molluscs, forums and things like
84:33 But then punctuated by small scale to scale isolated reefs. So the back
84:39 lagoon is where you get the smaller isolated patch trees developed. They start
84:46 as small scale features that might be of meters across for scale. But
84:51 storms they can shed material and they expand and coalesce into bigger scale
84:57 some of which end up being kilometer as you'll see. Okay. And
85:02 know from the modern that some of reef complexes initiate on preexisting pleistocene bedrock
85:11 that was created by during the last stand where you got dissolution,
85:15 karst. Okay. And that paleo becomes the substrate or the area.
85:21 for the next reef. Okay, sometimes it takes advantage of that
85:27 Sometimes you see the storm lobes they get pushed back by hurricanes.
85:32 the storm lobes become the topography for a reef. Okay, but you
85:39 reefs, corals, they like to the high ground, sometimes the high
85:44 is a foot above everybody else. course topography, deposition topography related to
85:51 lobes, something like that. Everybody appreciate what I'm talking about
85:57 How we're evolving the topography. The components re front and then debris sheets
86:04 be debris on both sides, but tendency is to shed more behind the
86:09 wherever that brief faces into the open . And then you'll notice when I
86:15 you through the modern, all these have channels through them that the coral
86:19 don't go forever is one continuous linear because you need a break. You
86:26 to be able to get water on off that platform. Okay. And
86:31 the reefs will go for a few , a few miles. Then they're
86:35 by a channel. Then you pick up again, broken by channel.
86:39 , that's pretty typical of all these march and barrier reefs. And you
86:44 see the numbers here for thicknesses. , this is just for the whole
86:49 . So this is basically for the 7000 years or so. The barrier
86:54 get up to over 22 m thick some places average thickness about 18
87:00 which is pretty good. Right, m of vertical growth and And 7000
87:07 is pretty impressive. Okay, everybody clear about the model and if
87:15 break the these reefs down today, in the pacific and the caribbean.
87:21 so called reef front is comprised of features called spur and groove structures.
87:29 grooves are channels to cut the right perpendicular to the reef. Uh
87:36 don't know exactly how, why we this topography, whether it's just due
87:41 the movement of water back and or whether there's a storm erosion effect
87:46 comes into play to initiate this. the group serve serve two purposes.
87:51 is they move the water on and the reef and then they allow movement
87:56 sediment from the shallow part of the out into deeper water and eventually into
88:03 based on semis. Okay. And grooves that the spurs are the construction
88:11 features. These are the frame Okay. Again, the springer structure
88:16 up parallel to the reef trend, the individual spurs are perpendicular To that
88:22 . Okay. And there's a shallow of sperm grooves that you see here
88:27 go from less than a meter to 10 m of water depth. And
88:32 going to see they're dominated by the of corals are adapted to day to
88:37 . High energy conditions, right? wave energy, oceanic swells. It
88:42 be 34 ft high, two in winter, 20 ft 20 ft swells
88:47 break across the reef. Okay. then typically there's a break. This
88:55 where you get a rubble zone and from 13 to about 25 m of
89:01 depth, you pick up the so deeper spurs and grooves. And here
89:06 spurs are colonized by more delicate Corals are branching corals because they're in
89:14 water. They don't they can live because they're not broken up by the
89:18 to day oceanic swells. Okay, you see the water depths controlling the
89:24 of those organisms, the corals. coral morphology is controlled by that.
89:30 uh that's an important part of the . Okay, so, appreciate what
89:40 going to show you here. This actually from Kinko's platform form. But
89:45 relationship holds for the police reef, gonna take you through and then the
89:51 barrier reef in Australia. Okay, you just look at, I told
89:56 , you know, 18,000 years where was sea level? Right
90:00 120m lower than present day sea And what's the evidence for that?
90:06 little notch. Alright. You see notch and this is a this is
90:11 diagram made by a marine biologist messing. I went to school with
90:16 missing at the University of Miami and went down in the Submersible off of
90:23 platform and he made this guy's an artist. Alright? And he drew
90:29 and he even picked up the notch his right non geologist saw the
90:35 Alright. And in the literature, describes this as a wave cut
90:40 Right? The sea level drops and rode into the rock by waves.
90:46 this is a biological erosion. Allnut . All right, here's the one
90:53 For the last couple of 1000 right where we had that stable sea
90:56 . Remember where the rate of rise just 4, 4 cm for 20
91:02 cm per 100 years rate of Which is nothing. All right.
91:07 is the knots that's developed along the today. And that's due to organisms
91:12 in the intertidal zone. Things like and uh in mollusk thing called titans
91:21 uses a magnetite tooth to scrape the in the intertidal zone and all these
91:27 that bore into it. They're cutting notch. Okay, So that's the
91:32 for a stable sea level. And picked that up at 120 m right
91:37 . Okay? And then sea level to shoot up and it came up
91:42 the edge. But it came up quickly. You drowned that inflection point
91:46 quickly sea level had to get up and stabilize. Okay? And it's
91:53 here in shallow water where the reefs starting. And I told you now
91:57 have a couple of kilometers of lateral that they can move out to before
92:02 get to the edge. But what's to happen when they get out to
92:06 edge? What's going to happen to barrier reef? It can pro grade
92:10 ? It can build out laterally to position right here. But then what
92:17 stuck right? You can't pro The reef cannot pro grade laterally unless
92:25 fills the hole in front of it its own debris. Okay, we
92:30 do it back here because that's still shallow. But once it gets out
92:34 , it's stuck. Right. And the problem with these steve margin
92:39 They can't pro grade great lateral Right? Because look at how deep
92:43 basin is. I mean, that's right here is 400 m of water
92:48 . Okay, So we're going to this point later. This is part
92:52 our discussion tomorrow, but I just to appreciate everything. I'm showing you
92:57 for police and great barrier reef. got a couple of kilometers that they
93:02 shoot out two before they get to edge to true drop off.
93:09 Yeah. When a reef pro it does what it builds up to
93:14 level. Okay. And what happens a coral when it gets to sea
93:20 ? Does it want to go above level? You're a marine organism.
93:26 want to be out of water? . So what are you gonna
93:29 You're gonna try to build laterally through , right? You don't want to
93:34 up above sea level. You want stay in that marine environment and good
93:38 agitation. So to build up to to a position here where you evolve
93:46 we call a mature very re profile you have the reef developed on the
93:52 edge and you have this flat, ? There's the reef flat. I
93:56 talked about the 1 to 2 kilometer belt, Right to evolve to this
94:02 or this morphology. What had that down here? Had to be the
94:07 reef. Okay. And it did it built up and out into the
94:13 ocean. Okay. And as it out this way, right, it
94:18 too shallow back here for the Okay, So the reef margin actually
94:24 abandoned. Okay. And what happens you keep building out the storms then
94:29 debris and they throw it back here they fill in that abandoned reef margin
94:35 they build up towards sea level. ? So the reef flat is the
94:39 flat, It's actually buried. The reef margin was building out.
94:45 that's how you pro grade a Okay. So when we see we
94:52 the living reef out along the right? Where you get the good
94:55 circulation and high energy? And we a relatively shallow reef flat. Stand
95:02 water, okay, just a couple feet of water on top of that
95:06 reef filling in with debris. And we drop off into the back,
95:11 again. When we see this profile cross sectional view, we call this
95:17 mature barrier reef. Alright. That it's built up the seal that's gone
95:20 far as it can go. The thing you can do now is pro
95:24 the seaward direction. Okay. And want to pay attention to the composition
95:32 comes along with these different sub environments this profile. Right? Where do
95:39 get the coarser grain stuff like the stones and grain stones? Where do
95:43 get the in situ frame stone? the binders? Okay. Where are
95:51 more baffle stone kinds of buildups? so let's just break this down.
95:58 . The seaward edge. As I , the factory is called the re
96:03 Any one point in time. That 100 200 m wide belt.
96:08 And what dominates there? The in coral production? But the kinds of
96:15 that live here is our dependent on depth and energy. So the
96:20 high energy part of the profile right is dominated by the more massive branches
96:26 in clusters. The things that are to the high energy day to day
96:32 conditions. And then what happens is go into deeper water? You see
96:37 change into more head coral and branching . Okay, because they're not adaptable
96:45 the high energy for reasons I'll talk in a minute. And then what
96:50 you get in the deepest part? that? Got down to about 25
96:53 . The deeper spurring grew was down about 25 m of water depth.
96:58 of a plate like morphology. And the biologists think that the plate
97:04 morphology is adaptation where head corals start out like this to maximize the amount
97:12 light striking their surface because you're in water. Okay, so just keep
97:19 in mind. This is something we're to take with us to the rock
97:22 . And then what do you get here in the reef flat? Remember
97:25 is mostly trouble. But the seaward where you get the strong surge of
97:32 as the wave breaks across the seaward of the reef flat, This is
97:36 you get the binders. This is you get the stuff that's hunkered
97:40 right? And crusting the debris. crusting corals and crusting red algae.
97:48 , so you get a bind But what are they binding their binding
97:52 really coarse rude stone? two grain debris. Okay, and then you
97:58 them. And you get back into the unconsolidated rubble flat of root stone
98:05 grain stone material. And then you off into the back reef lagoon.
98:09 this is where you get the small isolated Patricks who talked about,
98:15 but here, you know, you the change in morphology related to water
98:21 . Back here. The the the organisms you see back here in
98:25 water are the the morphology of the that lived in deeper water on the
98:31 side. But why are they in water now? Because they don't they
98:37 have to worry about being broken up shallow water because they're protected from that
98:42 wave energy by the reef flat. , everybody see what I'm talking
98:49 So branching coral is in deeper water because if you put them up here
98:55 shallow water, it's going to be by breaking wave energy. Okay,
98:59 gonna be torn up. So that's they're nestled in deeper water. If
99:04 put that same branching coral back here the back grief, they can be
99:09 shallow water because all that wave energy been dissipated by the reef flat.
99:15 , the wave is broken. You a good surge of water but a
99:19 of water is not going to break that branching coral. Okay, so
99:24 want to pay attention to what you here. This is the this is
99:28 diagram we try to take back to rock record for most ancient barrier reef
99:34 . And so when we core them when we look at them an outcrop
99:37 we see morphological changes and the structure the coral. Then we can relate
99:42 to this diagram and try to figure where they occurred. Okay, that's
99:46 game we try to play. All , Alright, so let's go through
99:53 two little case studies here just to you a flavor for how this these
99:56 systems are put together and we'll start With the little bit lower energy platform
100:03 or barrier reef from Belize in the Caribbean. So, our setting is
100:08 15° north of the equator. We're the heart of the strong easterly trade
100:13 bill. Okay. And you could the trade winds blow from east to
100:21 , that's the major driver for And then you can see the basin
100:25 pretty deep, that's 3000 m of depth. And then the other influence
100:30 is pre existing pleistocene topography. This an older pleistocene reef complex and offshore
100:38 reef complexes that were active during the . And then sea level dropped.
100:47 we killed the reach right by We cemented them up by car certification
100:52 freshwater Dia genesis and now we've Okay, so the classical police barrier
101:00 is the one that occurs back but appreciate their little isolated barrier reefs
101:06 these offshore satellite highs as well. , but what people talk about is
101:12 least barrier reef. Is this one here. Okay, and the tide
101:18 here is only 2 to 3 which is typical of the caribbean.
101:22 doesn't play much role here in terms deposition. Doesn't create a strong current
101:28 this open platform and currents aren't important for making reefs corals like the breaking
101:34 energy. They don't care about tidal . Okay, and then you can
101:40 , look at the back reef lagoon , very light colored up to the
101:44 here and then darker color down You can see the 30 m
101:50 Er Okay, so what's going on ? The police lagoon is shallow to
101:55 north, less than five or 10 of water depth By the time you
102:01 down here to the southern part by , it is over 30 m of
102:06 depth. So what's going on There's a big false system that cuts
102:12 here in the south. The big that cuts here from southwest to northeast
102:18 the transform fault is doing what it's down that Pleistocene platform and that's why
102:23 deeper in the south and shallower in north. Okay, so this is
102:29 of the story here for why you a change in a character of that
102:34 sediment from north to south. and then notice that this reef complex
102:40 not that far away from the Maya , the Police land mass. There
102:46 some rivers that cut off of this cut into the carbonate environ environment.
102:53 the shedding of the classics is right? It's related to periodic
102:59 it's not day to day shedding. the reef can can deal with that
103:04 grain classics get trapped along a trough to the shore line. The fine
103:10 classics work their way across that platform and as you would expect right,
103:16 clay gets trapped in deeper water. some of the lagoon, all carbonates
103:21 up with this greenish gray color that's reflection of both carbonate deposition and some
103:27 , but the clay doesn't does not the reef in because it's ephemeral and
103:35 when it sheds, right, even you have a flooding event to push
103:39 off into the marine environment. It what It bypasses the reef because day
103:44 day. Right? The reef that's being bathed by these breaking waves.
103:49 ? So the clay has no effect the reef. It just deposits either
103:53 the back reef lagoon or gets pushed into deeper water where it likely
103:58 Okay, so it's interesting this reef you're gonna see for great barrier
104:06 It also is closely aligned with the landmass and both of these do just
104:11 . Okay, Because the shedding of classics is not continuous, it's
104:16 Alright. And that's the key to a good reef developed in close proximity
104:22 a land mass. Okay. So let's take a look. All
104:27 . I skipped over some diagrams that put in your slide deck. Just
104:31 you a feel for the sediments and and stuff like that. Let me
104:35 show you how the police reef is together. Okay, And this air
104:40 is looking to the north and off the right is the deep water basin
104:46 the waves are breaking and to the of that is the so called reef
104:51 . This is where you get the group structure and then you see the
104:54 flat behind it and for scale that's a kilometer across. Okay, And
105:00 can see the white debris that's carbonate and coral debris. Then the darker
105:07 you see here is sea grass that stabilizing some of that sediment.
105:15 And notice there's an island already built here where this picture was taken that's
105:20 thrown up by major storm activity. sort of interesting. This island has
105:25 freshwater lens. So even though we're in the middle of a sedimentary reef
105:31 , you can see how you can to complicate the dia genesis right of
105:36 of these deposits because raga night is unstable in freshwater and you're building
105:44 freshwater lens here with some exposure of fresh water to these corals.
105:51 and then what do you get back ? The back reef lagoon. Where's
105:58 thing? Back reef lagoon? See transition from the lighter sand to the
106:04 colored water. That's a drop off water depth that's a little bit
106:09 But that's also an increase in sea cover, which gives you that darker
106:13 on the sea floor. Okay, let's turn around and look on look
106:17 this a different way. So now see the re front here with the
106:21 and groove structure, Shallow side of grooves again from about less than a
106:26 , about 11 m of water then typically breaks up. And that
106:31 that pavement zone that I showed you the cartoon earlier. And then the
106:35 set of spring grove group go from 13 m to 25 m of water
106:40 . Okay, the dark is again the living coral. The light color
106:46 is the grooves filled with sediment. things load up with with ripple sands
106:51 the summer. Okay. And then they don't get stripped out by a
106:57 in the summer, they're gonna get out by the swells that occurred during
107:02 winter. All right. It's a big swells that come in the winter
107:09 pull this stuff off shore and drag out into deeper water. Okay?
107:14 then you see the transition from the part of the reef front to the
107:19 of the flat. This lighter brown that you see right here is the
107:24 for coral rubble. That's the classical stone and then float float stone and
107:31 this will be grain stone that goes into the grass stabilized background. Forget
107:37 right, Everybody appreciate the transition. right. So let's take a look
107:44 how these things are put together. start with the re front shallow part
107:48 the the set of sperm grew structure the shallow reef front and the caribbean
107:54 dominated by this coral Mata. The name is moose horn coral. And
108:03 is one of the fastest growing corals , 18 cm left, 18 cm
108:08 year. Okay. And this thing to be in shallow. Breaking wave
108:15 conditions. It orients itself like The branches orient like this into the
108:22 wave energy. Alright. It can with that energy Even in the winter
108:28 the 20 ft swell, where it do so good as the storm
108:34 okay of a hurricane. So the surge, you all know? I
108:41 you all appreciate hurricanes. Right, been here, anybody here from
108:47 Harvey, I was probably did a more marine damage than Harvey did.
108:56 you all know the strength of the ? Right? Category one hurricane is
109:00 , 70 something miles an hour to and it goes up like that to
109:05 five where it's over 100 and 50 an hour winds and counterclockwise circulation.
109:12 ? And usually they're slow moving. they just move it a few miles
109:16 hour. Right? Not always, usually. And so when slow moving
109:22 do what they push a wall of in front of it that's called the
109:26 surge and the height of that storm is dependent on the strength of the
109:33 . So, category one Hurricane would us have a storm surge of about
109:40 ft with another believer or not. to 10 ft of wind wave agitation
109:45 top of that. Okay, in words, the amplitudes of the waves
109:49 get up 5 to 10 ft. , and then a category five hurricane
109:54 Katrina that hit Mississippi had a storm of 35 ft With another 5-10 ft
110:03 wind wave agitation on top of Okay, so what everybody forgets,
110:09 people who continue to build houses on marine on the beach environments,
110:17 Everybody forgets about the power of moving , Right? And how much a
110:23 foot of sea water ways? Cubic of seawater weighs 62 a half
110:29 So, imagine that wall of right? Slowly moving, pounding the
110:37 line or a beach house or Right? That's what breaks the corals
110:43 . That's what creates this fabric right . Okay, this is broken up
110:49 Mata, after a storm search. right. And then hopefully it comes
110:55 . Right? So, reef is just this wonderland of living institute
111:01 It's this mixture of in situ and , right? Because stuff is trying
111:05 grow and then it gets physically blasted a bigger storm. That's when you
111:11 the debris, you kill the What happens to the reef pieces?
111:15 gets broken up more by the right, The boars, and then
111:19 stuff takes off again. Right? this constant battle between up building and
111:24 slapped across the face by a Okay, So that that's the lesson
111:32 be learned when you if you explore reefs, right? You don't expect
111:36 the subsurface or outcrop to just see continuous growth of coral, right?
111:43 gonna find a lot of debris, ? And that's gonna be damn confusing
111:48 where you're at, right. Whether part what part of the reef,
111:50 hit the re front front of the , back of the reef. You
111:55 the challenge here. So okay, let's continue. We're in the front
112:02 the police reefs. Now we're underwater offshore. This gives you a feel
112:06 the topography of the sperm group I said the shallow spurs are dominated
112:11 the aqua for Parramatta. Okay. groups again our channels to move water
112:16 sediment on and off the reef. then you get into the deeper set
112:21 spur and groove structures. And you this relationship here where the spurs now
112:26 colonized by more delicate branching corals. is the other species of a cop
112:32 in the caribbean called serve a You don't need to remember the species
112:38 but just appreciate that these are more branching corals there really fast growing corals
112:44 grow just as fast as the moose coral. But they're not firmly
112:51 You can snorkel down and pull this off the sea floor. You couldn't
112:55 that without is firmly attached to a substrate. Right? And so now
113:02 appreciate why they're in deeper water, ? Because if you put these guys
113:06 shallower water, they're gonna be busted easily by day to day. Breaking
113:10 energy. Okay and then what's the coral species that dominates the deeper
113:17 deeper spurs. It's the head corals this dip Loria, the brain
113:24 And you say really? That's Some of these things are six ft
113:27 for scale. Why aren't they in water? Well, they are if
113:33 protected by their big branching buddies but not they're by themselves because these head
113:39 are attached by little narrow pedestal. . And if you put them in
113:45 zone of breaking wave agitation, there's much pressure on that structure that they
113:50 off the bottom like a bottle right? Like you're punching off a
113:54 top. And this is what always after hurricanes. All the head corals
113:59 stripped off and they get rolled Okay. Because of that. They
114:04 want to be in this zone if energy. So the brain corals like
114:08 see here or the star corals like see here tend to dominate in the
114:14 set of score improves. Okay, if you find them in shallow
114:18 which you do, they're usually protected the bigger branch corals. Okay.
114:26 then the deepest part of the spur groove structure involves is plating morphology.
114:30 is what it looks like underwater. is actually the same species of coral
114:36 this coral here. But look at morphology has changed. And I
114:41 this is where the marine biologists think they're building out laterally right? To
114:47 this uh greater exposure to lower light . Right? Because they still have
114:52 take care of their algo buddies. . Number corals. All these shallow
114:58 corals are colonial and they are they this symbiotic relationship with what are called
115:06 unfairly algae. I don't know if mentioned this last week or not but
115:12 doesn't hurt to repeat. So actually give the corals their color right?
115:19 the natural color of coral is white changes in coral color due to zoo
115:24 kelly algae. And the zohar belly also play a role in their
115:30 Okay. They helped create the calcified structure and then they feed the
115:37 They make sugars and they actually feed coral. Alright. Talk about an
115:44 job right for the coral, So when they talk about coral bleaching
115:49 occurs you know in a hot summer in august, right? If water
115:55 so warm and the corals bleach, not because the coral died yet.
116:01 because the so and kelly algae left . I got two hard got too
116:08 for the allergy and they got a , deeper water until the water becomes
116:13 little bit cooler and hopefully that better within a few weeks or less.
116:19 the corals are gonna die. Okay. So everybody appreciate the morphological
116:25 here is controlled by energy on the side and water death. Okay.
116:31 you go over the edge. Remember diagram I showed you at the vertical
116:38 , That vertical wall, that's the wall divers want to dive in the
116:41 , right? It's 200 m. course they don't dive down to 200
116:45 . They do the 150 ft But that vertical wall, Those like
116:52 for 200 m. And then what ? It goes like this, this
116:57 out. And what's the average slope on an open ocean? When we're
117:02 reef, it's about 45°. Okay. this is what it looks like underwater
117:08 front of the police reach. This in a Taken in a Submersible and
117:12 ft of water has true slope angle you can see what's going on
117:17 deposition. Right? Not only do have the reign of pelagic material occurring
117:23 , but you have shallow water reef coming down and sometimes it's blocks of
117:30 and people have described blocks, the of houses and police and other reefs
117:36 the caribbean. Down to something like a couple of meters and then even
117:42 materials, sand and mud size material works its way down. Okay,
117:48 , what's the term? You ever that term before? Holly nick
117:54 You don't need to remember that. a classic term anyway, but you
117:58 , big pieces and finer matrix You can see how you do it
118:03 on this slope. Okay, so potential is not going to be great
118:10 unless you can either have really big that are big enough to be a
118:14 into themselves with favorable preservation of ferocity you've got to come up with a
118:22 of debris here. That is more sand sized material, which is hard
118:26 do here. Right? Because you this pelagic brain of material mixing
118:31 Okay, now one other thing that into play here for all these reefs
118:36 there on a open ocean when we're side we've got this persistent agitation.
118:43 our discussion last week about marine You need stability and you need super
118:51 and you need a stirring rod to precipitation? Well, the front of
118:57 reef has meets all those requirements, ? The reef has built its own
119:02 . The water is warm and super . Right? It's coming up out
119:06 colder water. It's de gassing. when we lose C. 02 that
119:11 precipitation. And then you got the wave energy which is your stirring
119:17 So one of the things to think here on the upper part of the
119:22 and the then the reef front is potential for marine sedimentation. Remember this
119:29 from last week, Right? These the famous cloudy Radio fibers Sarah tonight
119:36 , they grow at rates of 8-25 per 100 years. And so the
119:45 of these cement is actually an attribute this environment, right? Is telling
119:50 you're in the frame stone, Because you got to have stability and
119:56 you're also catching that persistent agitation. , The downside is what what are
120:03 doing to ferocity on the sea You're starting to kill it.
120:07 So this is something you need to about in the subsurface. If you're
120:13 reef plays right, where am I to get the higher degree of marine
120:18 that kills some of that starting porosity permeability? Well, it's going to
120:22 the re front or the upper re . Okay, Alright, so everything
120:28 just showed you. It was just the left of this reef front.
120:33 . We started shallow set of spor right here. We worked our way
120:38 the front. We saw a change more delicate branching ahead coral. We
120:42 over the edge. Okay, And saw the slope. All right,
120:49 does the marines imitation occur from this to the left. Okay, and
120:55 what is everything to the right No marine seem impatient. Okay,
121:02 marine sanitation in the reef flat. look at the Of course the grain
121:08 occurs right here, finer and finer stuff as you go this way
121:13 the right and then you drop off the back reef again. All
121:18 so here's the seaward edge of that flat. This is what it looks
121:21 underwater. Those are the bigger pieces to that and broken up by
121:27 So that would be preserved in the record as a root stone. A
121:30 root stone with a coral algal grain matrix. But then what happens on
121:37 seaward edge, everything gets encrusted So this is a pavement.
121:44 This is the bind stone pavement that know the photos look faded here,
121:50 you could sort of see a faint tint to this rock that's living in
121:58 red algae. Okay. And then little coral. The screen is coral
122:05 a sort of popcorn texture on the that's encrusted coral. Okay, So
122:12 is where you get the n All right. So, it's a
122:16 stone with a grain stone matrix, it's also a bind stone fabric.
122:21 this is behind where the waves have broken. Okay, you got this
122:25 image of water. All right. only thing that can live in this
122:29 high energy environment are the low relief clusters. All right. Nothing dares
122:34 itself up like this. All So, that photograph is taken right
122:42 along the seaward edge of the reef . Okay. And then what happens
122:48 beautifully sorts all this stuff out. , I teach modern carbonates seminar and
123:00 platform for industry. Alright. And I bring groups down, we spend
123:05 day looking at our we have a , very refund Kinko's platform to.
123:10 very similar to what you see right and I bring our boats out to
123:16 position right here, where you see red dot. Okay, that's stand
123:21 water. We're behind the zone of wave energy. And so people get
123:26 and 34 ft of water and they that incredible surge of water,
123:31 The wave is broken. And what they standing on their standing on that
123:36 ? Okay. Just like what I you in the previous photograph,
123:40 The course rubble being paved over by clusters some scattered coral growth on top
123:46 that. All right. And then tell my boat drivers to throw out
123:51 couple 100 ft of rope behind the . And this is all optional because
123:57 never make people do anything in the they don't feel comfortable doing. But
124:01 basically do what the Australians called troll sharks, but we're not really trolling
124:07 sharks. We tell everybody behind the , okay? We slowly tell everybody
124:13 here to the lagoon and what do see? They see it changed from
124:19 bind stone fabric. Right? And you lose it right here, and
124:25 get into the root stone with a stone, and then you get into
124:29 float stone with a grain stone and then you get into a coarser
124:34 grain stone and then a finer grain stone. And then you drop off
124:39 the back briefly again. So nature all this out for you.
124:45 this is all natural sorting effect due the energy changes across that reflect and
124:51 about this. Where's your reservoir It's great from here to here.
124:57 sure, because there's no mud in system. Right, that surge of
125:01 removes any fine grained carbonate material. end up with rude stone, the
125:05 stone fabric. Excellent reservoir potential. . And then you drop off into
125:11 back refill again back here. And you see in the Northern Police
125:17 zillions of these little Pat trees because relatively shallow. Back there, These
125:23 reefs again start off maybe tens of across for scale in waters that are
125:29 five or 10 ft of water not that deep. Okay. And
125:34 you see some of the stuff coalesces the bigger scale features. Some of
125:39 briefs like this are probably several reefs have nestled together, right, Just
125:47 in the bigger scale reefs. But only now still only maybe 100 m
125:51 for scale. And they built up of the sea level because they have
125:56 on top. All right, you see these little reef shed material
126:02 write because of storm activity, but could coalesce because they're not big
126:07 Right. The lagoon here is relatively Alright, so this is characteristic of
126:13 Northern Police lagoon. Now, what's is when you go down to the
126:18 , let me back up here. corn that has been done here shows
126:22 these little reefs are nestled on pre topographic highs and inherited from the Pleistocene
126:29 of these are older reef deposits. of these are Karst topography. I
126:34 you corals like to take the high . Right? So just foot above
126:38 else is all you need and then . And basically 5 to 7000 years
126:45 accumulated a build up over 10 m . Okay, now when you go
126:53 the Southern Police again, I skipped couple of slides into your slide
126:58 Yeah, I remember were behind the reef. Right. We're in the
127:02 southern lagoon here. I told you gets up to 30 m of water
127:07 , hence the darker color. You here, you don't get these small
127:11 little patch reefs in the south. only get these big atoll. Reef
127:16 , kilometer scale reef complexes. And you could see that they are
127:30 They take on an H. one . The you see the east direction
127:36 the wind direction. Okay. The are better developed on the windward sides
127:40 you'd expect represented by the darker features the water that's living coral. Everything
127:46 why dishes debris that's broken up by , lagoons internally are relatively shallow compared
127:55 the 125 ft water depth between the . Alright, a lot of controversy
128:00 how these forms. Nobody really knows how these form. Some people think
128:05 sit on cars tolls but that's not documented. Some people think they're developed
128:10 great extreme deposits that formed during the low stand of sea level, but
128:15 not been found to exist. No beneath these reefs, you're gonna see
128:21 same sort of thing developed for the for the great barrier reefs in
128:28 And this is a dead ringer analog play type. We see all through
128:33 time from the lower palate is like the way up to the tertiary today
128:39 the younger tertiary griefs in southeast Same setting, same morphology.
128:46 But we don't understand the foundation here causes this atoll morphology. Okay,
128:54 these reefs are colonized by corals that typical of the patrons up on the
129:04 right there. The more protected you see the head corals and branching
129:08 . Again, they're protected from breaking energy by the reef margin.
129:13 So you still have good circulation here everything has to get broken up by
129:18 to create the debris that made up material. So, if you go
129:22 to that diagram, you can see where's your reservoir potential? It's on
129:27 periphery. Right? Where you've got reefs and And sands lagoon is
129:33 No good potential here. Right? , in this model, you would
129:36 what the margin. You'd ignore A critic lagoon. Right? That
129:43 ? Low energy and the critic. right. Alright, let's take a
129:48 break here. Just take a five . Well, we'll start back at
129:54 . Okay, so thank you. . So if there are no questions
130:02 the police reefs, I mean, are still pretty high energy reefs.
130:09 right, But let me take you Australia and show you something that's even
130:14 energy. And show you how that in setting is reflected by the characteristics
130:21 the of the reef. Alright, the great barrier reef is this area
130:28 red on the northeast side of the landmass. This is the longest continuous
130:35 modern barrier reef in the world. It covers an area of about 1600
130:41 kilometer length of 1600 kilometers. But actually more to the story than just
130:51 northern what locals call ribbon reefs. a southern zone here called That's related
130:57 the Capricorn bunker area. You see Channel. On this map, there's
131:03 that occurred down there. But there different style of reef deposition. The
131:07 the barrier reef didn't develop down on southern part for some reason, during
131:12 whole of stain transgression and what you are a series of these isolated atoll
131:16 complexes similar to what I just showed for police. Alright? So if
131:22 put all that together, that that is even longer from from north to
131:28 . But you see the setting we're up against the landmass. We
131:35 facing a deep water basin called the sea, right Couple 1000 ft of
131:43 depth off to the east. First 20 degrees south of the equator were
131:53 influenced by the strong easterly trade winds that the strongest trade winds are out
131:57 the southeast quadrant for this part of . And then what's unusual here is
132:03 tide range. Remember in the it was 2-3 ft of tide change
132:09 12 hours here, it is 10-12 . Okay, So when you change
132:15 level 10 to 12 ft every 12 , you get an incredibly strong tidal
132:20 that comes along with that and you're see how that's reflected in some aspects
132:26 reef deposition here. Okay, so famous great barrier reef I said,
132:34 locally called the ribbon reefs and it occurs up here on the northeast
132:41 of this trend. And again these are again a few kilometers back from
132:49 drop off. So the drop off out here. Okay. And you
132:55 why they call them the ribbon reefs locally they're broken up every few kilometers
133:00 channels. You need a way to water on and off the reef
133:05 But you basically have the same There's a thief re front would be
133:13 here in front, there's a reef , all the light colored stuff right
133:17 it. Back reef, lagoon, landmass down to the down to the
133:23 west. All right. And the back here is comparable water depth to
133:28 I showed you for beliefs. It's 100 and 25 ft of water
133:33 The only time you get patrons back where you have paleo topography and you
133:40 see some of the paleo topography. island is a granite IQ outlier of
133:45 Australian landmass. Alright. There's fringing complexes that are developed um, up
133:52 that granite basement. Okay, this a famous island. Just give you
134:01 little tourist information here. Captain James when he was sailing around exploring the
134:07 back in the 1800s, actually crashed of his boats on these reefs out
134:13 . They limped into Lizard Island. call it lizard island because it has
134:18 big monitor lizards on it. And Uh he fixed his boat and he
134:25 up to the top of Lizard which is 2000 ft above sea
134:31 And he used that lookout point to his way back out through the
134:37 And they call that cooks look That's a cook's look is right up
134:46 . Okay. You'd be surprised how thousands of people have been. Two
134:50 . Look, there's a book on . I've obviously been two cooks.
134:54 and climb up there and there's a where you can sign in literally thousands
135:01 people have been to cook's look, amazing. But this is what it
135:06 like from the air. And you see it's the lizard islands.
135:10 three little islands here and the corals right off the granite basement rock and
135:15 , they've, they've grown out to you this little atoll Marth ology
135:21 But this is what it takes in to get any kind of large scale
135:27 in a steeper lagoons. You've got have that pre existing topography here is
135:32 clearly expressed by the granite basement. problem in the beliefs was nobody can
135:38 what the foundation is yet. So they don't quite know why you
135:42 that until more morphology. But getting to the regular ribbon reefs here,
135:49 you look at them from the looking to the to the southeast at
135:54 scale, everything looks comparable to what showed you their beliefs, right?
135:58 have the deepwater bass in the coral , out to the out to the
136:04 left. And then you see the front is basically where the waves are
136:10 , right? That's the factory. then you've got the reef flat of
136:14 scale 1 to 2 kilometer wide belt debris and where it drops off into
136:19 shallow part of lagoon, you get bunch of little small scale patrons developed
136:24 here where it's shallow enough for reef . But once it gets to that
136:29 125 ft of water, then forget . Unless you've got some major pre
136:35 topography. And you see cut by again, just like on beliefs every
136:41 kilometers at this scale looks very comparable what I just showed you for
136:46 Alright? And when you fly over front of the reef, it's got
136:50 sperm group structures just like Belize. . But here's where things change when
136:56 drop down and get in the Remember what we had on beliefs?
137:00 had the big, massive branches, , dealing with that day to day
137:05 wave energy. When you go underwater on this sperm group structure, it
137:11 like a dead zone. Where's every the living stuff? Well, it's
137:16 , but it's not this, It's not the living coral. It's
137:20 high energy. The combined strong easterly in effect the 10 to 12 ft
137:26 range. Too high energy for anything to stick up like this.
137:31 So what colonize is the surface? the in clusters. It's encrusted red
137:36 . Alright. That's living in crusting algae, believe it or not on
137:41 surface there, but no corals or . They want to stick up like
137:45 because they're gonna get knocked over. , so this is the major difference
137:49 the, the pacific reefs and the reefs. Right? It's another jump
137:58 energy here compared to the caribbean And that's reflected by the predominance of
138:04 clusters, right? They dominate the and groove structure, whereas in beliefs
138:10 clusters, were only in that seaward of the reef flat, right
138:16 completely different story. Okay. And is hunkered down. So it's either
138:23 crusting coral like I showed you or at the shallow part, You get
138:28 entrusting. I'm sorry, crusty red in the previous photograph. And then
138:33 get some encrusted corals like you see . Alright. But everything's hunkered
138:38 All right. And again, nothing stick a cellphone. Alright. So
138:44 two photographs are taken out here where waves are breaking in this position.
138:49 here, the reef flat as I , is almost identical relationship to what
138:54 showed you for police. The same changes occur as you go back and
139:00 the lagoon here where it's shallow enough where you get all the shallow little
139:04 reefs. And then once it gets deep, no reef deposition.
139:09 So those little patrick's that are marked on the photograph look like this
139:14 You can see the more delicate branching now come into play again because they're
139:20 from breaking wave energy by the So, it's the same relationship.
139:26 really the major difference between the pacific beliefs is that C word re front
139:32 ? Where it's too high energy everything is low relief and cresting corals
139:37 or red algae. Okay. All . And then if you remember the
139:43 I started with I said, when get down to the southern uh complex
139:48 Capricorn channel area. What's interesting is some reason, and nobody really knows
139:55 the barrier reef never developed along this during the holocene transgression. All
140:03 And so there's no good reef along margin here. The style of reef
140:08 is expressed by this myriad of isolated reef complexes up on that drowned Pleistocene
140:17 and the korean that the Australians have here shows that these things are nuclear
140:22 on very subtle topographic features on that pricing service. That's either little topography
140:30 to older pleistocene reefs or stupa graffiti by karst during the last low
140:35 Okay, So don't assume that these systems, these linear platform margin reefs
140:42 forever. Okay, sometimes they just out. Like you saw like you
140:46 here and they're replaced really by a type of reef system in the
140:52 So these are really interesting because they're comparable. So what I showed you
140:58 beliefs, they're comparable scale there in comparable setting, but there's no barrier
141:04 front of them. Like they like was for beliefs. Alright, but
141:09 look very similar in terms of their . They developed this kilometer scale
141:17 Where's the good reef development? It's the C. Word. And windward
141:22 side. Right. The southeast trade come from this direction down here.
141:27 where you get the good reef That's what the purple basically. Purple
141:31 orange represents. Okay. And you see the re flat developed behind
141:36 But there's an asymmetry to the to width of the reef flat because the
141:41 flats not controlled by day to day . Right? It's created by storms
141:47 storms can come from any direction. don't be surprised by the asymmetry that
141:51 see here. Okay, This is not unusual. Alright. And then
141:58 of that material has been thrown up sea level to make an island.
142:02 one tree island lagoon here is relatively . And then what's the other
142:09 The reefs on the leeward side are as well developed as they would be
142:14 the other side. They're not as . They haven't built up to the
142:18 extent on the leeward side that they on the windward side. Okay,
142:24 let me show you what this one brief complex looks like from the
142:30 You can see the setting here surrounded relatively deep water. We're up on
142:35 drowned Pleistocene platform 125 ft of water . You can see another complex in
142:41 distance. Over here, there's one island which I showed you on the
142:47 , and you can see the breaking energy along the edge that zone of
142:54 brief growth. Right? And there's a good spur and groove development on
143:00 isolated features which you don't get in , but you do get here,
143:04 I think is a reflection of the energy. And then look at the
143:08 flat and it's actually been pushed back the lagoon and then look at the
143:15 here, the color of the If you recall what I showed you
143:18 police that lagoon had a little bit color. Right. Part of that
143:24 the water death. That part of is also the muddier sediment. And
143:28 see this turquoise color here, that's 15 ft of water depth.
143:34 And that turquoise color is a reflection a sandy substrate. Ok, so
143:41 something different here compared to what I you for the least. Alright,
143:46 , you know, 10-12 foot tidal means that you can you can
143:53 you could put your helicopter right here snorkel on the reefs right there or
143:58 could land right here and walk out the reef and low tide and snorkel
144:03 these reefs. But then at high , what happens is that water comes
144:07 very quickly. Right. And you hightail it back to the island because
144:11 get this incredible surge of marine water you re flood that platform that doesn't
144:21 this fabric here. This is all by storms. But what does it
144:25 to any mud that wants to accumulate here, strips out the mud.
144:29 , So, you see the implications on beliefs we had, we talked
144:34 the margin was perspective lagoon was Right? But here this whole complex
144:40 reservoir potential because you're you're stripping out the line mud. Okay. And
144:46 the reflection of the change in All right, So appreciate that.
144:51 right. And then look at the here for these for these complexes.
144:58 . Right. Excuse me. Been a cold all week. Um This
145:10 another one of these atoll reef Down by one tree reef. Lady
145:15 shows this classical asymmetry right? With great reef margin on the windward facing
145:21 lagoon, relatively unfilled, very patchy deposition on the leeward side. Those
145:27 become shoots for moving sand off the side. Alright, so appreciate this
145:36 . But appreciate that you can be this trend of a tall reef complexes
145:41 other reefs look like this where This 90 km to the north of Lady
145:50 . Same, basically same scale reef . But look what's happened to the
145:55 . Interior lagoon is completely filled It's filled in so much that you've
146:01 shallow up above sea level, that as a lighthouse on it.
146:07 here's that lighthouse from the helicopter You see this red ridge of storm
146:13 sediment at low tide. You can from the from the lighthouse all the
146:19 out to this point right here. . That'll all be out of water
146:23 then it will be re flooded during next flood tide. Alright, excuse
146:33 . Clearly what I want you to is the evolution of these systems is
146:39 uniform. Okay. That some maintain a toll morphology, some fill
146:44 Well, you know, sea level the same history for both of those
146:48 . Just one caught more of the effects than the other. Right.
146:53 , to give you this situation here most of that lagoon all interior has
146:58 filled with sediment. Alright, appreciate the spur and groove structures
147:02 You never see this in police on atoll reef complexes. But you see
147:07 here, you see them on all these complexes on great barrier reef.
147:11 I think I think what that's telling is the energy is part of the
147:16 here for making these spur and groove . Right? You can see how
147:20 can do this on the barrier reef . Right. You got that strong
147:24 wave energy. But even in these Utah accomplices get sperm structure here because
147:32 think this is a much more energetic . Okay, Everybody appreciate the contrast
147:37 . So, the Pacific reefs are , much different than the Caribbean
147:42 Alright, there's a greater species of here. They're like 25 species of
147:48 And in the Pacific there are only in the Caribbean. Alright. And
147:54 the morphological differences are are here, inquest ear's dominate these reefs, whereas
148:01 the in the caribbean, it's more the branches. The more robust branches
148:06 dominate the high energy part of the . Okay, alright, so let's
148:11 finish up the re story here by reminding you of how these reefs are
148:17 together. I think most of you me you're not snorkeled on a
148:21 is that right? No, you something to look forward to. All
148:28 . So, when you get that , Alright. I mean, try
148:32 pay attention to the way the reefs put together because everybody's first encounter in
148:37 reef is they're always looking over their for the big fish. Right?
148:43 always looking for sharks and stuff like , which are usually not a problem
148:49 a reef during the day. most big nasty sharks come out at
148:53 to feed. All right, so don't encounter them during the day,
148:59 pay attention to what's going on in reefs. Right. How much of
149:02 reef is in situ? How much this debris? I think you'll be
149:07 to see just how much debris makes these reef complexes. Alright. And
149:12 , not all the debris is from breakdown of the corals. There's stuff
149:16 lives in the ducks and crannies between coral. You see this green little
149:20 here, this is Alameda. Remember talked about Alameda last week as the
149:25 producer little stock plant, but on reefs that actually makes these bushes like
149:31 see here. And when you snorkel some of these reefs in the
149:36 you look at the sand, it like somebody took a box of Quaker
149:40 oatmeal and just dumped it on the floor. Well, that's the breakdown
149:45 of the Alameda. Alright, it down in these little oak oak meal
149:52 pieces of carbonate sand and remember how these things are. They live for
149:57 few months. Then they're replaced by plant. The rapid turnover allows you
150:02 develop a lot of, a lot carbonate sand. Okay. That fills
150:07 nooks and crannies and then we've talked the buyer rotors. Alright,
150:14 the Sediments that can be made by boring organisms to to 20 kg per
150:22 . I was just listening to a talk the other day and they were
150:27 about parrotfish. How much sediment of , you know, parrotfish are these
150:34 colored fish and they have teeth that like ours when they scrape dead
150:39 they're feeding on santa, bacteria on dead coral And an incredible number of
150:46 of sediment produced by one parrotfish, 85 kg of sediment per year.
150:54 a pair of fish which is about pick. Alright, I mean,
150:59 you can see what you're doing to reef. Right? I told you
151:02 this battle between growing up getting blasted storm energy, hurricanes and then being
151:09 on by grazers and bores like you here. So where I'm leading you
151:15 I want you to appreciate what you're to encounter in the rock record.
151:21 ? You know, if you ever involved in an exploration for carbonate plays
151:26 development of carbonate plays that are related reefs. The question always is when
151:32 put your first hole into that Right, identifying first of all did
151:38 hit the reef? And then what of the reef did I hit?
151:42 hit the reef front slope. They the reef front and they hit the
151:46 reef seaward side or leeward side. I hit the lagoon? Where do
151:52 go for the next? Well, I stay with the play.
151:57 that's the challenge. And part of problem here is represented by this diagram
152:04 . This is a map of a wall in the florida keys.
152:09 You've all heard of Key Largo? . Well, the next little key
152:13 from Key. Largo is called Windley and Windley Key has a state park
152:19 and they have a Pleistocene. A is an active quarry for some of
152:23 prices in reef and that's been turned a state park. And you can
152:27 see the quarry wall with all the and growth position. Right? All
152:34 . And so everybody say, that's a map of the reef
152:36 I see all these headquarters just growing upright position. But if you take
152:41 smaller piece of that and map which is what they did here,
152:45 red represents the in situ coral. blue represents the skeletal sand debris.
152:51 at the variability and exercise here was envision if you took a three inch
152:59 through different parts of this map. reef, how much frame stone would
153:03 see, how much debris would you ? So if you cord right
153:10 Alright, 67% of that borehole would frame stone. And everybody say I
153:15 the reef, right? No Look at the scale. But if
153:19 came over here, where's my thing over here and drilled right here,
153:28 26% of that borehole would have frame . You start to get nervous.
153:34 , did I really hit the Maybe I hit a block, the
153:38 thrown. Okay, well, what ? Right, front, side,
153:42 side? See the problem. This a challenge. Right? This is
153:46 challenge for everybody that plays these reef in the rock record, trying to
153:51 they hit the reef. And then part of the reef did they drill
153:54 ? Alright, so you need to this variability, which you would get
153:59 you snorkeled on a modern reef because you snorkel over areas where you see
154:04 of stuff and growth. And then see these depressions in between filling in
154:08 rippled skeletal sand. Okay, that's could evolve to something that looks like
154:15 with time. Okay, and then thing you want to pay attention to
154:21 ancient reef systems is take the relationships see in the modern between growth form
154:27 energy. Alright, This is what try to apply to the rock
154:31 Alright, so we go back to Devonian, we chase the storm atop
154:35 reef system. We can use the of the storm atop roids like this
154:41 figure out, you know, at whether a higher energy part of the
154:46 or a more quiet water may not whether it's deep or shallow, but
154:51 the game we can play. So and clusters remember they're always the most
154:57 high energy morphology. Okay. And robust, branching, high energy.
155:04 . And then when you start to , things get lower energy and when
155:09 get smaller branches, that's even lower or when they get played E that's
155:13 lower energy. Okay, so there's pretty good relationship here between growth morphology
155:19 energy. The sedimentation rate story I is much more debatable. Alright.
155:25 wouldn't personally, I wouldn't give this credence but but I think this is
155:30 pretty strong relationship between growth morphology and at the time of deposition.
155:38 And then this diagram from Noel James back. When is a little complicated
155:45 he's trying to show two types of buildups. Remember we talked about the
155:50 frame stone briefs, right versus the or banks. So the things that
155:55 out to the right with the light color, These are all what he
155:59 call classical frame stone buildings. And then you see the stuff that
156:06 back to the left with the little blobs. Those are the low energy
156:11 stone mud banks or mounds and things that. Okay, so we're just
156:17 about the high energy reefs here and can see who the players were depending
156:22 the geological age. So really it's until the uproar division that you start
156:27 develop these high energy platform margin buildups atop roids and corals dominate these in
156:34 lower paleozoic. And then you see lose them after the Devonian because there's
156:39 huge mass extinction at the end of Devonian. And then look at these
156:45 don't come back again until the upper . Alright, in upper Triassic and
156:51 , they're mostly corals and Strome atop . And then what happens in the
156:56 cretaceous is the middle and upper cretaceous dominated by rudest. Remember routers were
157:02 even corals, there are mollusk, ? But they can make some of
157:06 build ups and then corals dominate the . Alright, so there's a
157:11 Graphic age thing again that you need think about and when we go through
157:16 replays next weekend, I'll take you these different types just to get a
157:20 for how the strom atop right stuff different than the corals and how the
157:25 of stuff is different than than those . Okay. Alright. Any any
157:31 about the recall stuff. All I'll uh give you guys some guidelines
157:38 about the stuff that you should try take away from this discussion. Obviously
157:46 no detail right up in your notes I told you I'd have to write
157:49 book on this. And I'm not do that. And people have written
157:55 on this, but there's not enough really for you to go through and
157:59 those books. So I'll highlight some the stuff I think you should take
158:04 from the recordings. Okay, You guys doing okay? We got
158:13 another hour. So we're gonna finish with who would say? And
158:17 So I'm gonna take you through part this and we'll take another break.
158:22 , so, remember last weekend we about you ids, a non scalable
158:27 type. We don't know exactly how you is. Take on their their
158:32 analytic coatings, but we're pretty confident coatings are due to physical chemical
158:38 So, historically, to make you need super saturated seawater, you
158:46 something I wish to precipitate. So need a nucleus and you need a
158:52 rod or agitation. Right? And historically all the old literature that talks
158:58 you, it sands relates to its , to tidal current agitation. And
159:03 because it's all based on the northern models where tidal currents dominate the open
159:11 margins. Okay, so I'm gonna you through that series of models and
159:18 you variations on a theme. And then we'll take a break.
159:23 I'm gonna come back and finish up showing you there's another way to make
159:28 that has nothing to do with tidal and that's where the trade winds come
159:32 play. Okay, so remember it's are these sand sized grains,
159:39 ? By definition They're less than two size. When they get bigger than
159:45 , we modify them and call them elliptic you. It's they are polished
159:53 agitation. Right? By grand grand . The codings of almost all the
159:59 today are magnetic around the nucleus. I told you the nucleus could be
160:05 from a P Lloyd to a scalable to a court screen. Right?
160:10 I showed you for great salt All right. Doesn't matter the size
160:15 the units is controlled by the strength the agitation. So the stronger the
160:22 , the bigger the US get. you can actually use the word size
160:27 infer something about the strength of the currents are the strength of other energy
160:32 makes you it's average size fits in rock record or 250 to 500
160:39 Which is this size on, on right? Lower right, Okay,
160:44 , so let me introduce you to lay of the land here for the
160:49 Bahamas. Alright. The city of over here, Right, This is
160:55 the bahama platform complexes. This incredibly pile of mostly shallow water carbonate deposits
161:02 go back to the So the lower and arguably upper Jurassic. Alright.
161:09 think northern Bahamas are sitting probably on uh Grenet IQ basement crust.
161:16 Probably block faulted, which is part usually the normal evolution for these
161:21 They start off on some sort of faulting. All right, you can
161:25 the light blue color here represents less less than 15 m of water
161:30 Most of this is well less than m. A lot of this is
161:34 to 3 m of water depth. you can see it's cut by some
161:38 water and payments tongue of the ocean 2700 m maximum water depth, Exuma
161:45 . I think I mentioned this last was 2000 m of of water depth
161:50 all of this is surrounded by oceanic . Okay, and then there's pre
161:55 topography here. The black islands you here are the high pleistocene islands and
162:01 said some of them like a Luther , get up to 200 ft above
162:04 day sea level. They're made up both marine and windblown carbonate.
162:11 alright, so the orange here shows the distribution of these sands that are
162:18 by strong tidal current agitation. So a in a nutshell, you can
162:23 the model here, kids are confined platform margins because that's where the strong
162:29 current agitation occurs, That energy dissipates quickly up onto the platform. And
162:37 the old models, the old literature it was only for men six ft
162:40 water or less. Well, that true of this sand body on the
162:46 margin of great bahama bank. That's true of these other sand bodies at
162:51 ends of these deep water and payments the tidal currents are 2 to 3
162:55 stronger. So not only did the get bigger, The U. It's
163:02 deeper water. And some of it's like a southern tongue of the
163:07 or the area that I worked at end of Exuma sound form and 40
163:11 of water. Okay, so forget thing about you is only for me
163:18 a meter or two of water. all depends on where you're at.
163:23 . But you can see the expiration . Right? People started chasing who
163:27 stands in the rock record. Where they look? Platform margins, right
163:32 , the platforms. Something easily defendable seismic that they could chase.
163:38 so let's take a look let me you how the system these systems are
163:42 together. Alright, so I'm contrasting basically three types of sand deposits
163:53 I'm ignoring this one down here because is sort of a hybrid of a
163:58 of different sand body systems. So dark blue represents the basin.
164:06 The change from orange to blue represents platform margin. So that's the vertical
164:11 That we talked about this 200 m . Alright, and where you get
164:16 it sands in the northern Bahamas, never get a barrier reef.
164:23 this is the key key point. . And the concept here is called
164:29 default principle. It's one or the but not the two together. One
164:34 each other. Okay, so we have barrier reefs in the northern
164:39 I'll show you where those are but no, you sands occur behind
164:44 . Okay, so to get in sands, you need something still between
164:51 sand body system and the drop And that's this orange belt here,
164:56 is called coral grow grain stone. what is this? Is the rocky
165:01 with scattered coral alga growth producing of nearest scalable sand, but it's not
165:07 reef. Okay, understand what I'm . So it's one or the
165:12 but not the two together. The is if you have a barrier reef
165:17 ? And you've got these, you waves right to make good barrier
165:21 Breaking waves, the reef is gonna the energy and it's going to consume
165:27 lot of the calcium carbonate. There's gonna be anything left over for who
165:30 behind it. Okay, so that's rationale. One or the other,
165:35 not the two together. One behind other. Okay, No, the
165:42 of the tidal currents determines the geometry the sand body. So in this
165:49 here, which is related to the side, on the western side of
165:55 bahama bank. Open platform. The current strength is not that strong,
166:01 in sailor's terms. It's one not scientific terms, it's a half a
166:06 per second. Okay. And so average swimmer could swim against a half
166:14 meter per second. Title current velocity you'd have to work really hard to
166:19 it. Okay. And so what you produced here? You produced a
166:25 sand body a couple of kilometers paralleling the platform margin. But step
166:32 because you need that horrible zone in of it because that's the source of
166:36 nuclei. Okay. And then look the sand body evolves to. It
166:42 to two components. The yellow is we call active do it. Sand
166:47 . This is where we think the . S. Are agitated every title
166:51 and reforming. And then the blue stabilized to a light. The woods
166:58 formed in the yellow got thrown back winter storms and hurricanes and stabilized organically
167:04 the sea floor. Okay, so a completely different type of sediment compared
167:10 the active you like. Okay, we make this differentiation. Alright.
167:17 why do we do this? Because you talk about reservoir quality, in
167:21 experience, at least 95% of the , no matter what happens to my
167:26 to the zoo. Ids the reservoirs the yellow, the blue never develops
167:33 quality is a side or top seal the active shoal. Okay, that's
167:40 we map these separately. Alright. appreciate this. So the tidal currents
167:45 back and forth every 12 hours. ? The flood tides are stronger.
167:50 ebb tide is weaker. Okay, this is all you can produce.
167:55 right. And those tidal currents dissipate quickly once they get a few kilometers
168:00 onto the platform. Alright, contrast this with the ends of those
168:05 water payments that southern the end of tongue of the ocean on the northern
168:10 of Exuma sound. This title current double or triple. Okay, 1
168:19 1.5 m per second. And I tell you because I've experienced this.
168:25 right. In fact, I just it about two months ago and I
168:30 when I was a grad student how these day and currents were. All
168:36 . You don't swim against a two 3? Not tidal current. When
168:41 worked that area, I threw 200 of rope behind the boat.
168:46 I would snorkel down right below the , go straight down sample, grab
168:52 sample, make my observations and then I come back up, I'd hope
168:56 grab on to the end of the . That's how much you moved in
168:59 water with those stronger currents. and so you see how that translates
169:04 a different geometry. Right, is a sheet sand. The lines of
169:11 to the platform margin. But look how the sand bodies are organized
169:15 title bars that are roughly perpendicular to platform margin, so that's a reflection
169:21 the stronger tidal current agitation. so there's still a belt of active
169:26 deposition. There's still a belt of stabilized sand back here, but you
169:32 see how things change. Okay, now the sand body is up to
169:37 2025 km wide instead of 1, km wide, like you get up
169:45 . Okay, that's all due to the change in fizzy graphic setting those
169:50 water and payments. They funnel basically funnel the standing wave and they increase
169:57 velocity right when you're trying to squeeze through, you increase the velocity of
170:01 water. Okay, so that's the end member model and then a variation
170:08 the theme is the long edges of platform. We have pre existing island
170:13 shown by the black here and you've these cuts through the islands and when
170:18 try to force tidal currents through these cuts, you increase the blast even
170:23 . Right, you get up to knots of tidal current agitation. And
170:28 do you produce there? You produce are called flood title? Delta's
170:33 yellow again is the active and then light blue around it would be the
170:37 equivalent. Okay, does everybody appreciate driver here is strong tidal current
170:44 Alright, no reefs in front of of these seward sand body systems.
170:48 linear reefs. Okay, no barrier . But if you need that little
170:53 go zone of rocky bottom because you some nuclei to get the U.
170:58 . And body system going. Once goes just going there, there's some
171:04 stuff that lives on the U. . And body system right there.
171:08 molluscs and they're kind of terms and forums that live there that die and
171:14 nuclear potential nuclei. So it becomes sustaining once it gets going. But
171:19 need that horrible environment to get it . Okay, of course. There's
171:24 show on the diagram here, tidal currents produce a symmetrical ripples,
171:29 ? So your ripple train goes like with the flood title component and then
171:36 it will do this and come back other way. So what the opposed
171:42 ? A bed set with the post would be herringbone cross stratification. That's
171:48 characteristic of tidal current systems. and let me just show you how
171:56 is put together. All right, here's the photograph from one of the
172:01 flights. Looking down on the northern , right? There's Exuma sound,
172:05 area I worked. There's the open , western margin great bahama bank.
172:12 the one not system. You can the white sand body right along the
172:17 and then look at the ends of deep water and payments 2025 kilometer wide
172:22 because the tidal current strengths are 2 3 times stronger. And then the
172:26 arrow points to that area where you the pre existing island topography and you
172:31 the you get the flood tidal deltas ? Okay, so let's just take
172:38 closer look right, this is the part on the western side of great
172:42 bank, straight to florida is the . There's the horrible zone along the
172:47 which is right here and then the is the act of sand. The
172:53 gray is to stabilize stuff thrown back storms and then this is a completely
172:58 style of non allergic material that we'll about later. Okay, everybody see
173:05 that translates caracal active, stable. . Oracle on the open, open
173:15 side, the drop off would be to the left. There's a linear
173:19 body kilometer two across for scale paralleling margin and then stabilized here. And
173:28 look at the active part here. you see from the air. Are
173:33 mega ripples? These mega ripples are waves 234 ft high. Okay,
173:40 the amplitude. They don't migrate every cycle. They only get moved around
173:45 winter storms and hurricanes. Okay, . That's the fine scale ripples that
173:50 back and forth. Every title Okay. And then you see these
173:56 here, These are called spillover Those are storm generated. So there's
174:01 actual channel that Phil feeds that spillover and what do you get in the
174:06 lobe? You get the trough cross right? As you cut and fill
174:13 cut and backfill that channel. Is is it? Did you make the
174:17 ? You get that that trough cross . Alright, alright. So when
174:23 say active, that means every title . This stuff gets moved around on
174:27 surface. We say stable. We just that. It's organically stabilized on
174:32 sea floor by sea grass by other of cyanobacteria and algae. Okay.
174:40 the only way this gets reactivated is hurricanes. Okay, which is harder
174:46 do once the sea sea grass starts take hold. Right. The other
174:51 I want to appreciate is that none these title driven systems migrate in response
174:57 tidal currents. Okay, They shift and forth but they only expand laterally
175:04 get pushed around by major storm Alright. And here's two photographs that
175:10 that for the this is the southern of the ocean here. Okay and
175:16 the, Sorry, Here are two taken over about a 20-year period.
175:22 is 2001 on the top. 2020 the bottom. Just look at
175:27 just spend a second looking at those bodies, They have not moved in
175:33 years. Okay, because there's been major hurricane activity through that area.
175:40 , so this these sand body systems migrate on a day to day
175:45 Okay, you need the big hurricanes push them around to modify the sand
175:50 geometry to get them to procreate or laterally? Okay, the day to
175:55 tidal currents just move this stuff around and forth. Okay, they build
176:00 right? They shallow the sand body up. They'll bring them up to
176:04 level but they don't expand these things and they don't move them around.
176:10 , this is going to be in contrast to what I show you for
176:13 trade went system. Alright, so me just show you again, I'm
176:19 show you the detailed attributes of these . Okay, there's the there's the
176:27 bar belt then I worked Okay. and stable. Alright, dynamic system
176:36 the hurricane comes through here, a of this darker gray stuff will be
176:40 . Okay. And I've noticed over years since I've worked here that some
176:45 these channels sand bodies that are active this photograph later become stabilized.
176:50 Until the next big storm comes through reactivates the surface of the sand
176:55 Okay, and then on this side Exuma Sound is where you get the
176:59 title, Delta's developed where you have pre existing island topography. Okay,
177:05 have cuts between the islands. That's you get the flood title delta's
177:09 that look like this from here. right, so that's the five knots
177:12 tidal current velocity. Alright, But still have the active, the really
177:18 sand and then the darker gray would the stabilized part of the sand body
177:23 . Okay, so everybody appreciates the , Right? Platform margin, no
177:29 reef in front of it. And strength of the currents guides the size
177:36 the U. S. But also the geometry of the sand body.
177:40 again let's finish up. I ask the question right? Like going to
177:45 going to the rock record right? evaluating sands. How do I map
177:49 these two sub environments? Right? do I tell the active stuff from
177:54 staple? For the reasons I just right one becomes reservoir one doesn't.
178:00 so let's take a look at the would stand environment 1st underwater. You
178:08 it to be in Tennessee rippled that's rippled. Any mud produced in this
178:13 is going to be removed. So if you were to box cord
178:17 sediment you'd expect there to be a degree of preserve stratification. The other
178:23 being most borrowers don't want to live this setting. Right? There are
178:28 a few species of borrowers that can burrow this stuff but not to the
178:33 that they destroyed the stratification. So of the first things we look for
178:37 the rock record is a high degree preserved cross stratification. Okay. And
178:42 when you look at the sediments look the you is they are very well
178:47 . The outer coatings are robust and . What don't you see on the
178:53 parts of these grains. You don't a lot of that mechanization. So
178:59 remember mechanization, we talked about last when grain sit around to get micro
179:04 and transformed to a massive mike. ? You don't see any mechanization on
179:08 outer part of these grains because they're around every title cycle. Okay.
179:15 those ooh IDs are of comparable size shape that's called well sorted. And
179:22 is the one exception in carbonates where pay attention to well sorting because when
179:27 see something like this with fluids, is a reflection of the actively agitated
179:33 environment. Okay, this is the carbonate environment where you can do
179:38 Okay. And you can you can , you know, we're starting off
179:43 incredibly high permeability. So historically this the kind of sediment that turns into
179:50 that turns into a great reservoir. . And then the transition from active
179:55 stable. As you see here in air photograph, um very abrupt.
180:02 . And darker color again is due stability underwater, created by organic
180:08 So this is sea grass with its network that holds this stuff together.
180:14 cal curious green algae also stabilizes the . There's something called an algal scum
180:22 that it's like filament is cyanobacteria, not a stromatolites, but it likely
180:29 that stuff together. All right. once you stabilize that environment.
180:34 here come all the things that want live here. Right? So you
180:36 a greater diversity of skeletal material. borrowers return to this environment. So
180:42 start destroying stratification along with the roots the sea grass. And this is
180:47 you get the acolytes. Remember we about acolytes? So I hope you
180:53 got that question right today. Difference between words and acolytes. It's
180:59 precipitated grain type. Right? Light, mechanically rolls around on the
181:04 floor, santa, bacteria traps the . Well, this is the environment
181:09 it lives in forms. Okay, only time this stuff gets rolled around
181:14 during a winter storm or a Then the grain type sits there grain
181:19 sits there. Upper part gets encrusted cyanobacteria trap. Smock. Right,
181:26 . If you box score this, preserve stratification, everything's destroyed by by
181:31 probation. And then look at the . It's still you can still see
181:36 of foods. But look at the here goes to out the window,
181:42 , poorly sorted, there's mud in stuff like taking the mud out to
181:47 the thin section. So a lot the black Would be variably filled with
181:51 mud anywhere from a few percent to or 15% line mud. So these
181:56 gonna be pack stones, right? going to be poorly sorted skeletal skeletal
182:02 analytic pack stones versus the well sorted stones. Okay. So what happens
182:11 you take poorly sorted and well you bury it, which one loses
182:16 the faster it's always the more poorly stuff. And that's why historically this
182:22 ends up being a seal to the active part of the sand body
182:28 Alright. And then what a lot people don't appreciate is that is the
182:34 nature of this transition. All I mean, and you've seen it
182:37 the air now here it is So underwater when the tides are
182:43 this stuff is rippled intensively up but right next door, none of
182:48 sediment moves because it's all held stabilized sea grass and ogle scum matt.
182:56 , so this stuff is actively This stuff is by activated. See
183:00 borough mounds of the shrimp. You a course through this or a box
183:04 through this. This is what you nicely stratified, well sorted analytics.
183:10 that's going to be preserved as a grain stone. Sharp contact, poorly
183:16 biter baited, borrowed reworked fabric below . Right. And you know,
183:22 problem with sharp contacts on the rock is when people see this, they
183:27 to invoke major environmental changes, Usually involving sea level. Right?
183:32 want to change sea level wherever they a sharp contact. See what we
183:37 change here. This is the active body jumping over the stabilized during a
183:44 . Okay, This is how you this relationship. It has nothing to
183:48 with zero. Okay, this is you expect in these high energy sandbagging
183:54 , you expect the active sand bodies jump over there nearby stabilized equivalents.
184:00 , every time you get a big or really strong winter storm.
184:05 And then the last thing associated with stabilized sand body is this unique grain
184:11 that we talked about last weekend called stone. That was a type of
184:16 made up of fluids or bicker ties it's And so grape stone is to
184:21 expected associated with the stabilized a All right. Because you can can
184:28 this stuff together in a stabilized sand by either organic binding or by some
184:35 of sanitation effect. Alright, alright one last thing that's characteristic of the
184:42 the of the higher energy sand body is marine sedimentation. Okay, So
184:51 one not system that I talked about the open margin. There's no marine
184:57 involved there. Okay, you can goods, but that's about it.
185:00 can't put the words together and hold together with imitation. But the title
185:07 and the flood tidal deltas. You get marine segmentation. You get it
185:12 the active parts of the sand bodies the shoulder crest like you see here
185:17 you get it on the deeper sand here, sometimes in 20 ft of
185:22 . But where don't you get the sedimentation? You don't get it in
185:26 stabilized part, which seems counterintuitive, ? Because you need stability. You
185:32 have some dudes can't be moving around the time or they wouldn't be cemented
185:37 . So it seems counterintuitive. So me explain how you do this.
185:42 right. So in the act the segmentation only occurs on the active part
185:47 the sand body systems. So normally tides just rip across. Right?
185:52 get the asymmetrical ripples like I'm trying illustrate here. Okay, but what
185:58 during major storm activity? You throw these big mega ripples? I mentioned
186:02 mega ripples underwater. That can be to four ft high. All
186:08 When you generate something like that, you create a energy shadow behind it
186:13 the flood tidal current is always stronger the Epp. Alright, so if
186:18 can block that strong flood tidal you create an energy shadow right behind
186:24 . And what that does is within day or two, it creates a
186:28 of stability that gets occupied by that scum matt that I was talking
186:35 Okay, so when the tides are this stuff is just shooting back and
186:40 . Okay, but if you can it, taking advantage of that,
186:45 topography within a day or two, will colonize that energy shadow with this
186:51 of material. Okay, ready? what I'm saying? This is not
186:59 catalytic material. It's a loosely mesh mesh of cyanobacteria, blue green
187:08 other bacteria that holds this stuff in . Okay. And so this is
187:15 being in the field, it's difficult describe what this is like, but
187:18 you want to experience what it's like stick your fingers in it next time
187:22 make a bowl of jello right and up in the fridge, put your
187:27 in it and shake it around. that's what it feels like underwater.
187:32 is held together by the sound of . Alright, So that's the pioneer
187:37 . That's what starts the whole That creates more stability. Now the
187:42 currents flowing across will start to do we'll start to precipitate a rag a
187:48 in the upper sand. Alright, the upper part of the sand body
187:52 exposed to that marine sedimentation effect and greater right at the surface and less
187:58 less as you go in because your of cement is the overlying water
188:04 Right? And so you only create thin sheets of cemented material, They're
188:10 about this thick, 10 20 centimeters , and then they go back and
188:15 sand. Okay, so there's a degree marines imitation at the top of
188:21 crust. And then this is just 17mm below that previous thin section.
188:28 can see there's less marine cement. I went further down, you take
188:32 less marine cement, you see what's here, you're dropping out the marine
188:36 . You're choking off the system All right. So these marine cement
188:41 never very thick, They're not laterally because there's no way to stabilize the
188:47 sand body at any one point in . Okay. So from a member
188:53 the reef, you would destroy You could destroy a lot of that
188:56 on the sea floor in the sand . This is just gonna be patchy
189:00 sedimentation, different layers. It's not to dramatically reduce the the porosity of
189:07 sand body, but its presence in sand body tells you these are higher
189:13 with sand body systems. Okay. are the upper level, stronger tidal
189:18 systems. Okay, Okay. And is also where you get the stromatolites
189:24 I talked about, the kilometer stromatolites form on these hard grounds on the
189:28 parts of the sand body systems. . And uh, over the
189:47 Well, that's a meter above sea of interface normal, just very
190:00 But they're getting very every time they trying to get exposed. That's when
190:07 agreed then they have to be a and they want to award and expressive
190:14 little bit. But in between this the this is the hard ground
190:22 Okay. In between those kilometers smile . Okay, so that's how they
190:27 . Alright. And there's a paper put a paper on about the subtitle
190:34 that that you can look at. right. All right. So what's
190:40 story for northern Bahamas. Right. you're playing this model and applying it
190:45 the rock record, you would have be in an oceanic setting.
190:50 Where you get strong tidal current agitation you have to be linked to an
190:54 by some sort of payment or cut order to get that title current
191:00 And you would play for the high margins and there would be no
191:04 very reef in front. Okay. would be the model, right?
191:09 ignore the platform interior, you'd write off as low energy. And the
191:13 . Alright, That's that's in a . That's the northern bombs. All
191:19 . So, you guys want to a little stretch break or do you
191:22 to just finish up on easy? , I haven't lost my voice
191:33 So let me take you down to southern Bahamas. Alright, And show
191:37 where you can make sands that have to do with tidal current agitation.
191:43 it with uh, taking advantage of persistent strong trade wind agitation.
191:49 And we're gonna go from the northern , which are all title current dominated
191:54 to Kinko's platform, were now down the northern reaches of the tropical
192:00 This is, this is 22 degrees of the equator. So, 21
192:04 degrees north, that's in the hard strong easterly trade wind belt. The
192:09 winds up here in the northern Bahamas general easterly trade winds and here on
192:14 you can see they mostly come out the east and southeast quadrant.
192:19 And stronger means they blow more persistently the year, right, elevated
192:25 So up here in the north typical wind might be 10 or 12 miles
192:30 hour Daily winds. Okay. But southern Bahamas, the low end would
192:36 18-20 up to 30 or 40 during summer. Okay, so completely different
192:43 . All right. And so keiko's is smaller than what I just showed
192:48 for a great bahama bank obviously. you know, see there's a little
192:52 platform over here. So that's why call this area Turks and Caicos.
192:57 keiko's platform is the place everybody goes look at the geology and let me
193:03 show you a little bit closer to here. Pleistocene islands on the north
193:10 platform down here on the south and west and east. Good barrier reef
193:16 here, all along the northern margin I faces the atlantic. We started
193:22 this platform back in the 80s and thought we'd find a mini version of
193:26 Bahama Bank. In other words, thought we find the reefs on the
193:29 ocean side. Yeah, that's where at. But we thought on the
193:34 margin here would be all that sand and we thought the inner part of
193:37 platform would be mud just like it today in the northern Bahamas. And
193:42 course we were surprised. Okay, a grain stone dominated platform. Most
193:48 the grain stones are analytic and the are expressed in different ways so that
193:54 see this photograph to different styles Or two major sand body systems.
194:01 of these line up east to Right? This one here and this
194:04 here, here's the map view. call this mid platform show. We
194:09 this amber Scholl and look where they , where they initiate, they initiate
194:15 a high pleistocene island. Am Burgess behind Ambergris key and mid platform shoulders
194:24 an island called south Caicos. And trade winds blow east to west.
194:31 I don't know if you've ever heard or not because a lot of people
194:34 never heard of this concept, but concept is called tom below effect when
194:40 have pre existing topography and it's struck trade winds pushing wind waves like this
194:48 into that topography. What do they ? They diffract around both sides.
194:53 , that's the tom below effect. the wind waves would come like this
194:59 to west and they diffract and come this way from the north. They
195:04 around from the south like this, come around that topography and they would
195:08 into each other. Okay, and would happen when those two waves,
195:13 hit the water would boil like Okay, and that's where the US
195:20 start and once they get started then feed off themselves right? And the
195:26 winds, you're gonna see gradually push stuff down. They provide the agitation
195:31 they move the sand from east to to create these long linear sand body
195:37 . Okay, So this is what looks like from the air. It's
195:44 the mega ripples that are 4-5ft high , but there's no title current agitation
195:51 you're there on a calm day and winds don't blow every day.
195:55 You get some days where the winds blow and I've been on the sand
195:59 several times when that's the case, feel the water come in with the
196:05 and you feel it go back out the sand doesn't move. Okay,
196:09 currents don't move. The son of of this is driven by trade women
196:14 . Alright. And you can see two components again, the active is
196:20 , the stable is the darker Remember the northern Bahamas? Where was
196:24 marine sanitation? It was in the sand bodies and not in the stable
196:30 is just the opposite because the trade move these mega ripples around every day
196:36 you can't stabilize anything on the active . So your marine sedimentation actually occurs
196:42 here on the stabilized planks. and I'm gonna show you some video
196:48 . But yeah, basically this is a washing machine. This is like
196:53 in your washing machine and turning on wash cycle when the trade wind comes
196:57 from the north, the wind ways in from the north, they come
197:01 from the south like this the water you feel you get pushed like this
197:06 you get hit by white one wave from the north and then you get
197:09 this way it's like being in a machine. Okay, when you sit
197:14 the shallow part of the sewage sand system. So let me show you
197:22 video. Alright, the first video taken and this is what we usually
197:28 our field trips down there. Lake like april may. That's the best
197:33 because you're out of the winter storm you before the hurricane season. And
197:39 the trade winds generally blow about 18 20 miles an hour and this is
197:43 day where the trade winds were 18 20 miles an hour due east where
197:48 got that tom below effect. water boils, that's because the water
198:08 a little cloudy, pardon power, don't get anything like that on a
198:56 current system. It's laminar flow, current flow, but never that kind
199:01 agitation unless it's a real stormy Right, okay, so that's and
199:08 this is this is the same time wind but mostly coming out of the
199:13 quadrant. Mhm. Okay. colleague. Okay, it'll feel this
200:53 local wind wave agitation. A lot people this this construe this to be
201:00 where on one side of the basin have strong winds or storms and they
201:04 up these waves that go across the side of the basin and agitate.
201:09 , this is local wind wave Like having a bucket of water.
201:14 ? And when the wind is not it's smooth as all get out and
201:18 when you turn the fan on, get instantaneous agitation. This is what
201:21 talking about. Okay, this is trade winds do. Okay. And
201:29 I mentioned that these things can Alright, so my my colleague hal
201:34 superimposed google photographs for over a two period and was able to show that
201:40 these mega ripples migrate, migrated about m over a two year period.
201:47 a time period where there's no Okay, you don't get this with
201:51 title current systems, but you get with the wind waves so you can
201:56 what the system is doing, Not only generated is but they're being
202:01 downwind by the stronger easterly trade. . Against symmetrical ripples identical composition and
202:11 to what I showed you for the Bahamas. Okay, the currents don't
202:17 a role here. This is not currents are not important on keiko's
202:21 Okay, so that's the first All right, so what's what's the
202:27 ? Subtitle sand bodies and bogus and platform. Line up parallel to the
202:32 winds. Alright. The subtitle sand line up parallel when we have older
202:38 on providencia lease, which is the tourist island or west Caicos. Over
202:44 , where I showed you the evaporates the dolomite forming with the evaporates?
202:50 have older shorelines facing into the trade . You make shore line parallel
202:57 stands oriented perpendicular to the trade winds they pro grade into the trade
203:03 So let me show you west there's west Caicos, that's the
203:09 I talked about last weekend when we're about the reflux disorganization, there's the
203:15 pleistocene ridge of west Caicos north to orientation. Trade winds come right to
203:22 the Eu. It's form along a line. They started right here.
203:28 , this is a wedge of holocene . Sand that's a half a kilometer
203:33 for scale, which you don't appreciate that these are a series of beach
203:38 complexes. Alright. They form perpendicular the trade winds, but parallel to
203:45 shore line. Right so the north orientation. And if you were to
203:49 this, you would walk up about of these Beatrice complexes. The first
203:56 are about 6-7 m high. He up and down up and down up
204:02 down until you get to this last right here. This one right here
204:07 the shore line is 20 m 20 m of sand. And when
204:13 here on a windy day standing on ridge which I've been here many
204:17 You feel the salt aiding up that face. Okay, this is an
204:24 dune. Okay. And so what's the net effect here? That effect
204:29 to do what the pro grade into wind. Alright. The zoo it
204:33 have been dated. We think this ridge formed about 3300 years ago.
204:38 in 3300 years ago, this beach have pro graded at least a half
204:44 kilometer into the wind. Okay, are the US forming? Just right
204:50 . So this is shallow shore face beach environment for making new ids.
204:55 didn't get thrown up by storms. beach ridges that pro grade into the
205:00 . Okay, so this is the style of sand deposition on keiko's.
205:08 , so on a windy day, it's hard to get a boat into
205:12 beach because you've got four or five waves breaking across this beach. Because
205:17 , when you get that 20 to mile an hour wind, you really
205:22 a hard time getting a shallow boat here, a small boat into that
205:27 . Okay, everybody appreciate the The factory for making you. It's
205:33 . It turns out that most of deeper part and open part of the
205:36 is covered with sand. This is third type. These are widespread sheets
205:42 sand forming in waters as deep as and 87 or eight m.
205:49 now, clearly in the deeper water activate that and make goods, you've
205:54 to have stronger trade winds. so when the winds are blowing 30
205:58 40 miles an hour, all of platform materials actively agitated. Okay.
206:03 when you got maybe a 20 mile hour wind and seven or eight
206:07 that stuff may not be moving. right. So it doesn't move all
206:09 time. All depends on the but the net effect is you're still
206:14 a grain stone in the platform Okay. And you notice there's a
206:19 here that's not mapped as a politically it as uh the skeletal sands.
206:24 is the deepest part of the platform it gets down to 12, 13
206:28 of water depth. And um, that setting, you don't get
206:33 it's okay. You get reef related . But the going back to this
206:38 here, sorry, the yellow this is what the who is look
206:46 . They don't look like great right? They look lumpy, they
206:50 highly magnetized, but that's not the . The point is that there's no
206:54 in the system. All the mud stripped out by the trade winds
206:58 Okay. I mean, if you're for carbonate sand, you care about
207:03 or something that looks ugly like Now you care about finding good reservoir
207:08 , right? That's what the exploration always looking for. Okay, and
207:14 the next part of the story is trade winds and concert with storms.
207:18 what do what they push the sand the leeward margin to the west,
207:25 of it goes over the edge and see that happening in an area like
207:29 fit today. And there's academic seismic off of this that shows this pronounced
207:34 lapping wedge. Nobody's courted. But doesn't take rocket science to appreciate that
207:40 are probably good grain stones that make this wedge. And sometimes the stuff
207:46 get pushed over the edge. Sometimes builds up to make topography and that's
207:50 we mapped as a subtitle levee in in this position right here.
207:56 so let me just show you this spit. Okay, this is the
208:01 of the line and am Burgess and colleague Sarah Wallace has been out here
208:07 probing this stuff to see how thick was. And He was out here
208:12 July one year when the winds were about 30 miles an hour, 40
208:17 an hour. And he actually observed U. S. Shooting over the
208:21 of this leeward margin. There's no here because that's the wrong orientation.
208:26 , so that's that coral sand environment . But the U. S.
208:29 actually salt waiting right over the Okay, and then we've been down
208:35 now long enough to experience the effects two major hurricanes and one was Ike
208:41 2008 and then Irma in 2017. both of those storms took west spit
208:49 shoved all that sand over the edge fit disappeared. Okay. And eight
208:54 later it's back to looking like Alright. That's how quickly that stuff
209:00 and gets pushed down to the All right. Everybody appreciate what I'm
209:05 . All right. So, the winds are not only stripping mud and
209:11 sized material off most of the inner of the platform, but it's pushing
209:16 sand to the edge and then over edge. This is unheard of in
209:20 northern Bahamas, which I'll tell you happens there tomorrow. Okay. But
209:25 unheard of in the northern Bahamas. . And then the last part of
209:29 story is that deeper area that we've in green here. Alright. That's
209:35 deep for you. It's and deposition get the wide spread sheets like I
209:39 mapped. But you get these isolated complexes all through here. All these
209:44 circles you see here are isolated reef . The white halo is due to
209:52 that come out at night to So they eat the cyanobacteria. That's
209:57 you get the white ring. So and crabs and things like that come
210:01 of the reef at night. And keep that cyanobacteria away from the
210:08 But appreciate the scale here. Uh mean, the first thing we notice
210:13 is these reefs are shedding debris. . This happens after the storms.
210:20 you see the white debris around the , even in 10 or 12 m
210:24 water will then start taking on an . That's the trade wind agitation,
210:31 wind wave agitation. All right. then of course the storms will do
210:35 they coalesce this stuff in the bigger features. So, I'm going to
210:38 you I grief here in a minute you can see how I grief is
210:42 part of a larger, coalesced reef . So they start off with the
210:47 isolated atoll. It's not at but it's an isolated reef complex,
210:51 eventually they will coalesce in a bigger features and they're taking on orientation again
210:58 parallel to the trade winds. The linear nature of the of this
211:04 here is parallel to that easterly trade effect. Alright, let me go
211:10 to this map here and then look happens. So, the point I'm
211:15 here is we have reefs and woods . Okay, remember the northern
211:22 It was one or the other, not the two together. Alright,
211:26 here we have them together and the part of the platform up to 40
211:31 in from the open ocean and then have them again here, over here
211:35 the leeward margin. You see where platform margin changes orientation where it kicks
211:41 and gets a little bit better exposure the southeast trade winds. This is
211:45 we get these little mini platform margin developed. All right, and and
211:52 one I'm going to show you is one right here called southwest reef.
211:57 , there's west Caicos where I showed that pro grading wedge politics sand.
212:02 Southwest reef right here. You get little bit better exposure to the trade
212:07 . That also means you get less bank transportation by the trade winds of
212:13 . And so this reef is a reef, but it's only a few
212:18 in length. Okay, It's built to sea level. It has a
212:22 flat, It shows that textural change I talked about for the big barrier
212:28 . Eventually, this stuff turns into scalable sand back here. But then
212:32 happens is that scalable sand? It turned into a little sand by trade
212:36 agitation, Reefs and Woods together. . one behind the other. This
212:43 unique to the trade wind system. , you don't see this in the
212:47 Bahamas where the U. S. response to title current agitation.
213:00 Alright. Everybody appreciate what I've said . So there are two ways to
213:03 goods tidal currents trade Win. And I'm gonna argue when we get
213:11 the play types next weekend, that Caicos models are actually more appropriate for
213:17 of what we see in the rock because to get strong tidal current
213:21 you have to be linked to an ocean either directly right exposed platform or
213:28 have to be linked by some sort investment back into that isolated little intricate
213:33 basin. Okay, Alright. Any or comments? That's it for
213:41 When we come back tomorrow, we'll , we'll go back to the northern
213:45 and finish the rest of the story the northern Bahamas talk about the nature
213:50 that platform interior deposition. Then we'll about tidal flats and I'll contrast two
213:55 for making tidal flats, 1-related to when one related to trade winds augmented
214:02 storms. Okay. And then we'll up with some other elements that have
214:06 out in the northern Bahamas and sort summarize the northern Bahamian models.
214:12 And then we'll get into the ramp tomorrow. I'll take you to the
214:17 gulf and I'll show you the modern model. And then we'll be ready
214:22 talk about one of the other aspects deposition that involves evaporates because even though
214:29 strictly not, carbonate deposition is closely to a lot of carbonate systems.
214:33 , I have a short lecture on deposition. And then we're gonna make
214:38 jump and add time. So, I've talked about today, this is
214:43 much time, right? 5-7,000 years less. We're gonna make at the
214:49 to our story and talk about sequences cycles and then log expression and
214:54 That's what we'll do tomorrow. So we'll see you guys in the
214:59 . All
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