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GEOL6358 Terrigenous Depositional System - Day6 03-04-2023-Part3
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00:00 It. OK. Well, let's let's go beyond the show. Uh
00:07 look at what's happening on the invasive slope, the, the deep
00:13 systems. Uh There's a lot of references. Uh Most recently, uh
00:23 And others have published a really excellent , but it's hugely expensive. It's
00:28 $175. Um but it's the most to date compilation there is uh Weber
00:37 Slat in 20 oh seven is now little out of date but is still
00:42 amazing resource and it's available um in an E pub for a lot
00:51 And I think I gave the source that in the, the syllabus.
00:56 There's a whole bunch of other I mean, and I haven't
00:59 So uh I'm still working on uh some of these references. OK.
01:08 When we think about deep water, guess there's two questions. Um are
01:12 talking about deep water sediments deposited in water or drilling in deep water
01:26 Um The distinction between ultra deep water deep water is basically water depth.
01:34 so we clearly have been going offshore in deeper and deeper water.
01:42 really since the 1980s. Uh, if we look at that though
01:49 uh, the so called, well, let's just say nondeep water
01:57 , 85% of the, the reservoirs flu heal or delta. If we
02:06 at the deep water, uh, guess that would be deep and ultra
02:16 . 91% are turbo cents. in one sense, most of the
02:23 that we're looking for when we go uh deeper water depths were deposited in
02:30 water or beyond the shelf. Um It turns out you might also
02:36 though there's a bump in carbonate that . Well, the carbonates are clearly
02:44 deep water and so that reflects basically salt, early carbonates um that are
02:53 deep water, but I have now buried to great depths. Um if
03:00 look at the production uh in for example, tremendous increase, uh
03:07 least until 2013, if you look the increase in that Brazil, tremendous
03:16 still going. Ok. Um Some is that an awful lot of it
03:22 pres salt and it could be 20-30 barrels of recoverable oil. Uh If
03:31 look at liquid versus gas, we're getting a tremendous increase in these
03:37 water plastic reservoirs. Most of it from places like the United States and
03:47 and Angola, look how little oops how little shallow production is occurring um
04:00 Brazil. So these are some of deep water basins where we're getting exploration
04:11 deep and ultra deep. In we're looking at giant fields in this
04:21 here is referred to sometimes as the Triangle, Gulf of Mexico, East
04:33 , Brazilian Coast. Look at the of those discovered volumes in that particular
04:44 and what we mean by uh the Brazil, Angola, Nigeria, the
04:52 States. So we're gonna see a of the maybe, well, many
04:59 the examples that I'll be using, in terms of field examples are coming
05:03 those areas. Now, the subs is, is an important thing.
05:12 But it, it refers to a of the early rifting that occurred when
05:22 the Atlantic split, both the North and South Atlantic. And when that
05:30 , we had these rift valleys. We had alluvial alluvial fan and lacustrine
05:38 mainly. And then we had marine and salt. And then on top
05:45 the salt, we begin, what the trailing margin of the Atlantic
05:53 That salt is what underlies the Eoan of the north of Eoan, um
06:03 of the Norfleet formation, for But below that salt, we've got
06:09 fas and particularly in Brazil. Below salt, we have rift face
06:15 which will include a lot of the carbonates and marine carbonates. So that's
06:22 most of the carbonate production is deep subs. So early rift face
06:30 that's also why Angola, Nigeria and have a lot of commonality. That's
06:38 the Atlantic salt uh basin was. . Now, what's controlling these
06:47 Well, sea level, that's pretty tectonics that works. Rate supply of
06:52 supply. How about that? All these are things that we kind of
06:56 intuitively and all of them we've talked in the course. So let's look
07:04 the slope and let's look at the of slopes we get, we,
07:07 alluded to it to a certain extent we looked at shelf edge deltas.
07:13 so there are stable pro grading mark a slop and those are probably gonna
07:25 mainly associated with near shore. I'm , shelf edge deltas and the long
07:34 cliffs. But when we talked about deals, we also talked about unstable
07:43 the markets and that's all a completely look to the show. It's a
07:50 grading unstable shelf and about 80% of reserves, At least as a 2007
07:59 associated with that particular slope setting. . We can also envision a,
08:05 shelf that's eroding or better said I that's eroding into the shelf. We
08:12 that in Florida, we see it some cases uh in uh the eastern
08:19 rather uh northeastern part of uh the and Canada, there are areas where
08:28 have embayment due to very large Um I can't think of a setting
08:37 now but we have tect conically active like compression margins that would be both
08:47 uh and especially ocean continent, convergent also transformed, could be transformed uh
08:58 uh ocean continent, transformed like And we have extensional margins uh which
09:09 be by the way analogous to what pres salt was. And uh the
09:18 Southern Atlantic and which would be analogous the early rifted systems in the North
09:30 . The North Sea is in a of ways like the pre salt,
09:36 there was no salt deposited in the Northern Atlantic in that area of the
09:41 Atlantic. Ok. So this again at the some of the situations and
09:51 where we tend to get sand rich . Um They can be confined and
09:59 particularly associated with salt Ecton. They also be confined within uh faulted Robins
10:08 and compression thrust faulted areas or they be unconfined. So we've got these
10:19 find Robbins with the mobile substratum, associated with salt to a lesser extent
10:26 , shale in the *** delta salt South Texas, uh and salt offshore
10:37 Texas, Louisiana nonmobile substratum. We're at Robins and Riff Cheese and we're
10:44 at uh maybe little piggy basins or basins uh in compression areas. Uh
10:55 could be looking at this here, actually where we saw the Helio
11:06 So if it was ever a deep base, we might have had deep
11:10 fishes there as well. The unconfined floor, that's pretty much trailing edge
11:17 like the Gulf of Mexico once we past the shelf. Now, when
11:26 think about petroleum exploration, we can , let's begin with the, the
11:35 types. These are lit faes uh laminated but stone, massive sand.
11:45 then we could think about it in of how we pack those vertebrate,
11:52 they accumulated through time. And now looking at amalgamated bands, et
11:56 So we're going from relatively small scale to putting them into larger and larger
12:03 elements as those elements get into larger larger features. We're getting into things
12:13 distribution channels, channelized lobes, lobe until such time as we can use
12:24 for the combination rather of all three develop a reservoir model. So that's
12:30 goal is to give you the basic so that you can interpret and ultimately
12:40 reservoir walks. Now, the good is that a lot of the deep
12:49 systems have a lot of similarities and of the examples we kind of start
13:01 a shelf in size valley or or , which is the funnels sediment from
13:10 shelf past at least part of the . The thing goes into a slope
13:17 levee complex which is on the slope then diverges and expands into basin floor
13:31 or slope lobes which can be on lower slope or actually out in the
13:37 is out in the Abyssal plain And the other similarity is that we
13:42 to have a similar, similar sequence events. We often have a slope
13:54 , creating the canyon some kind of massive slump or slide. We talked
14:01 that a little bit when we talked the examples in the oh South Texas
14:12 where we looked at slumps and then filled with the retrograde slumping uh began
14:21 work its way across the shelf. saw some Norwegian uh examples in
14:27 OK. As those slumps begin to towards land at some point, they
14:36 a source of settle, that sediment be high stand sediments. If the
14:46 goes all the way across the shelf it could be low stand sediments to
14:52 those shelf slops. At that you can bypass the sediment to form
15:03 slope lobes or basin floor fans. at some point, we've got
15:15 the abandonment of that sediment system and back filling of those channels and a
15:25 of the fans with a series of levy complexes draped with hemiplegic. So
15:34 gonna talk about that sequence, not , but uh when we cap this
15:42 on Friday, uh we're gonna see repeated time and time again.
15:50 let me talk a little bit about events that get the sediment in
15:59 Um And we can talk about ignited and non ignited flows and it ignited
16:10 are ignited by a singular event it's over a short period of time.
16:19 For example, uh earthquake generated maybe rapids sedimentation and over steepening,
16:32 a change in pore pressure. It be relatively short lived like uh storms
16:43 longer live, like go. We maybe gas hydrates might uh have a
16:53 discharged. A non initative flow. is one that occurs over a long
17:02 of time. It doesn't have a event we talked about that. We
17:07 about hypericum flow due to high concentrations out during river discharge. OK.
17:14 We also think some fine grained underflow with oceanic currents are forming maybe contour
17:25 or other examples. So where do , how are these various types of
17:33 ? Where do they deposit set? that, that means that we need
17:38 understand the deep sea fishes, deep fishes, we have channels and channel
17:47 . OK? And that channel fill include not only the channels but associated
17:53 and over bank fas sounds a lot a flu. We have down dip
18:02 lobes that can ultimately form amalgamated sheet deposits. This is kind of like
18:11 delta but we also have mass transport . M T CS or M T
18:20 if it's a deposit. And these basically land slops That can cover thousands
18:27 12 associated with these ignited events. have low density turbo fill and
18:38 These actually are types of deposits that aggregate may be filling the distal parts
18:48 the depositional lobes or the lateral parts the levees and over back deposits.
18:57 these aren't completely discrete features. Uh turbin fill can be part of channel
19:04 or depositional lopes. We have contra drifts and contra deposits we'll talk
19:12 Hopefully we'll get to today. And , there's just that hemiplegic ooze that's
19:19 uh raping of beam Mery deep bemet formed under other conditions. Now,
19:37 , there's a lot of different kinds deposits formed by several kinds of processes
19:46 the deep water. Um I'm gonna this a little bit but this is
19:54 good start. Um We could have . Yeah. Right. I'm gonna
19:59 all these later on high density to to low density turbos conite in traction
20:08 . I need to go back and what Galloway was referring to. That's
20:13 term we don't use it. And talking about slumps first, basically
20:20 is the failure or rather that is material that was slum that was deposited
20:27 a typically deformed manner, give it a uns submarine uh landslide. It
20:34 be small, it could be These can include these mass transport deposits
20:45 complexes which may be covered like I thousands of square kilometers and be hundreds
20:54 meters thick. Now, we can them in core and see some
21:02 Uh These are fairly small, little bos rich contorted areas. Uh These
21:10 probably slump, local slumps, not failure that we talked about when the
21:17 edge collapsed. But they can extend those big slumps where we, we
21:23 creating in some cases, the holes are the precursors to the canyons that
21:31 the funnels for sediment to get past shelves. And one of the things
21:37 uh we've realized for some time is when that failure occurs, it is
21:49 downhill. It could have maybe initially as a slab slide, but eventually
21:56 and more water gets involved and it a plastic deformation with a lot of
22:04 . And as more water gets we got a debris flow that could
22:09 be transformed into a turbidity current. we're gonna look at this transformation here
22:17 a lot more detail. But the here is that a single year
22:21 an ignited event can be preserved or of that event uh can be preserved
22:31 a lot of different types of some of which grade laterally into another
22:37 some of which become disconnected from one . OK. And that just talks
22:45 the idea that as, as seawater entrained, you go uh from a
22:52 to a more dilute flow. But are other cases where the water is
22:59 this flow is dewas. So we actually create transformations where it goes from
23:06 dense to more dense flows. And is kind of a a of a
23:16 sketch of what happens when the slump the slide occurs. And you could
23:23 liquefaction that gives you a debris flow you can get turbulence include, you
23:31 also have a river come in and can generate either a low concentration or
23:39 concentration flows. And we get different of processes. We get grain to
23:45 interaction, fluid traction flow do and where we have low concentration, a
23:55 of mud, low concentration total settlement we can get long distance transports.
24:05 what this diagram basically is focusing on how we can get the spectrum of
24:17 of deposits. Now, in God scribbles it up. Um this
24:26 useful to think about how many different these and results and show up,
24:40 it's way more complicated than that. so we're gonna to, to get
24:45 to where we can understand it. gonna focus on some little scenarios and
24:50 every possible combination. And one of simplifications is to, first of all
25:02 that for the most part, we've talking about fluid gravity floats in this
25:11 where the sediment is set in motion the motion of fluid water in motion
25:20 train set. But we've, we've touching on a few examples of settings
25:29 we had sediment through gravity flows. entrained sediment sets the fluid in
25:43 the hyper py nights, some of debris flows on alluvial fans. So
25:54 focus on sediment. Your gravity flows the deep setting and look at what
26:01 the sediment entrained and morbidity. Currents have turbulence. Hence the name and
26:14 sediment is maintained in suspension by But we can also increase the sediment
26:27 . And when we do that, begin to have other processes like
26:34 set dispersive pressure and finally, matrix affecting how those sediments are being
26:46 So let's kind of look at it for a second fluid transport turbulence
26:55 But as you get more and more , you get hindered settling. And
26:59 that means is that as it's trying settle there, it's expelling water from
27:06 underlying pore pressures and that water is upwards hiding hindering the set. It's
27:14 phenomenon in part associated with liquefaction. got dispersive pressure. We actually alluded
27:22 dispersive pressure when we talked about inverse and grade flows where you've got so
27:28 sediment concentrated that there's it's all grain grain contact and that grain to grain
27:35 is causing a pressure that is directed the free surface. And so there's
27:46 , it it's hard to get sedimentary per se, certainly as opposed to
27:54 turbulence. And finally, there's matrix and especially if there's fine grains
28:04 we have a lot of cohesion and we can literally get gravel floating in
28:11 . We saw that with the matrix debris flips. Now, we also
28:19 about the idea of fluid strength when talked about the difference between say a
28:28 fluid and uh Bingham plastic, a fluid is basically a, a fluid
28:40 has constant viscosity and zero shear There's no strength, apply a little
28:48 of sheer stress and it's, it's , it's moving. On the other
28:52 , you might, you have thick if you like uh that have a
28:57 strength and so you have to exceed critical applied sheer stress before they
29:04 That's the sheer strength that's or the strength. So this might be a
29:13 Newtonian Bigham plastic forming a cohesive Here is a Newtonian fluid form of
29:23 there are some funny cases where the changes with time that we're not gonna
29:31 getting into. No. When I started teaching, this course seems like
29:39 years ago. Um It was pretty because there were four types of
29:48 your gravity floats, turbos, uh flow deposits, grain flow deposits,
29:56 debris flow deposits. Uh We changed a little bit, certainly turbidity,
30:02 deposits or turps. Then we have cohesive, sandy debris and non
30:11 sandy debris. And what's happened is , we begun to see how these
30:18 similar and then we have cohesive which are the classic debris flow.
30:28 . That's too bad in a way it was easier for me to describe
30:31 when I had four things and they discrete and I could ask a test
30:37 a test and it was easy to . Well, that's not what things
30:45 . First of all, we're arguing what we mean by turbo. Uh
30:54 they just things deposed by turbidity currents are they all part of all sandy
31:05 san uh sedimentary gravity flows, including as flows? Tori flows and grain
31:12 ? Um I'm going this, we on describing that but I'm gonna,
31:23 gonna say I don't, I will these, but I'm gonna talk about
31:33 and low concentration turbidity currents which will some elements here. So for the
31:41 being, if you're not sure, a sediment, your gravity club.
31:47 you know it's it was deposited by , call it turbine. If
31:56 we'll talk about it and we'll start it in more detail later.
32:02 this is what I was talking about . Uh strength of matrix um dispersive
32:11 , hindered settling turtles. The current flow, brain flow blood flow.
32:20 . Now, if we talk about and we talk about sediment concentration,
32:29 Newtonian fluid, low viscosity, non fluids, high viscosity, where,
32:39 does that occur? Well, it's a little unclear because look at
32:47 overlap here. We, we've got deposited by turbulences. Now there's an
32:58 with cohesive pressure and then an overlap dispersive pressure and as far as flow
33:07 . Well, now we've got a density turbo which overlaps with a high
33:13 turbo which overlaps with hyper concentrated flows debris flows, muddy debris flows,
33:23 and maybe grain flows. So we're need to simplify this if we're gonna
33:33 what the terms are. But the news is we've understood turbidity currents that
33:40 density currents formed by high sediment concentration a long time. Uh So we've
33:46 them in flumes and now we're beginning measure them in, in the
33:51 Um And they morphologically, they have fine gray tail, they have a
33:56 body and then they have this area where there's potentially some scour uplift and
34:03 and a lot of stuff. And we've also known for a long
34:10 that there's a low density and a density turbidity current. The problem is
34:18 , we hadn't agreed on what is sediment concentration to separate those two,
34:27 , 10, 20%. It's kind what we saw here. Um Here's
34:34 uh separation, I'm sorry over here uh oh let's see. Oh uh
34:46 . Low density going to 20%. density starting at 6%. Um hyper
34:55 is something else. So there's a of overlap. Yeah. Part of
35:06 confusion is there's a variation in concentration the singular turbidity flow when we look
35:19 those quote high density flows, whatever choose to call uh call that
35:28 But we've got a basal zone that's turban and we've got an upper zone
35:40 is turbulent and stratified. Now it out that even within that turbulent zone
35:53 in here, we have a stratification or a concentration of sentiment, the
36:03 bottom You might have 50% set. a debris, look, it's so
36:12 that the support mechanisms are grain to contact and matrix support. In
36:21 we have what is in essence a density flow that we typically call high
36:29 or turbid occur. And then as concentration gets less and less as we
36:34 towards the top, it grades into low density flow or low density or
36:42 concentration turbidity current. OK. So is what's called the tripartite gravity current
36:50 we often will see this basal dead or density current that's gonna give us
37:02 de light overlaying by a high concentration current and then a low concentration to
37:14 . Now, as you might expect this thing is flowing down, that
37:22 high concentration debri is gonna slow move slower than the less concentrated higher
37:31 viscosity turbidity currents. So the first pinch out will probably be this gravity
37:41 that debris flow and then the high and then the low density. So
37:47 can we see the beginning already of lateral transformation from a debris flow.
37:56 low density tt uh we see it as well with this pinching out and
38:07 here's that high density and low density . And now I this particular example
38:24 this whole thing a turbidity current, choosing not to do that and actually
38:36 often done as well. Um The is these are two very different flows
38:43 said that they are moving in they're part of the same event.
38:49 it's really a sedimentary gravity flow, a turbidity turbulence is really only a
38:57 up here. Yeah. So we've a low density turbo and a high
39:06 turbo. That's basically the two parts . And they have different types of
39:17 sequences. And we're gonna focus on in discussing turbidity currents. And we
39:25 gonna ignore for a second that the , the debris flows. Ok.
39:34 , we're now to the point where no longer restricted to looking at THD
39:39 and flute, We can actually drop sensors and put them in a submarine
39:46 5000 ft below the surface in the Canyon. And we can look at
39:54 passage of a turbidity current and this the front and the concentrations or high
40:04 in red, then lower concentration in and the lowest concentration in life.
40:11 , keep in mind this is a measure of concentration, but it can
40:18 transformed into what looks like a down concentration. And it certainly shows the
40:32 in the this tripartite gravity flow. these things are occurring. Oh,
40:46 . Even during the high stand. the reason for that is that the
40:50 submarine fan actually goes into the mouth the Congo River. So, although
40:55 typically think about the fans being shut during high stands, it all depends
41:03 where the source is. And if source is right at the mouth of
41:07 river, then you got a lot fans, a lot of turbos and
41:11 fan deposition many during a year. . Uh Both thickness range from 16
41:22 75 m. Velocity is up to m. Uh These are big thick
41:31 globes and they're occurring many times a . OK. Now, this particular
41:45 distinguishes between cohesive and non cohesive flows it distinguishes between turbos and density
42:03 The debris flows little different than I've about. But uh this is pretty
42:13 to low density, high density, turbidity currents, high density, low
42:27 , by the time we're up we're into the debris flow Deos.
42:34 . So recognize this transition is, actually pretty realistic. People just use
42:44 terms. But what is most useful this paper is the idea of the
42:54 change in process and product. So low velocity starts off slow and
43:05 . Why should it accelerate? It because it's getting less viscous and it's
43:12 less viscous because it's incorporating water, going from that slump so that debris
43:24 . Yeah. So speeding up and the sediment concentration, it's decreasing as
43:35 speeding up because the concentration is getting and therefore viscosity is decreasing velocity
43:47 But something else must be going And so let's look at the support
43:52 . Matrix support is high as long it's hasn't been uh deluded too
44:03 But then matrix support decreases as you to add water and therefore grain to
44:13 interactions become more important. But at point, we, our sediment concentrations
44:22 decreased as we keep adding water, that we're beginning to get fluid turbulence
44:29 that begins to dampen grain grain So this decrease is basically the decrease
44:40 matrix support and increase of fluid turbulence we get into what is loosely called
44:52 turbidity flow. OK. Now notice says uh loose sense and strict
44:59 strictly speaking, they're arguing a true flow is only supported by, by
45:13 in a broader sense. It's the importance of turbulence versus grain to grain
45:22 . OK. This translation is easy visualize and explains a lot about the
45:34 of these slopes and the resulting change products and ultimately their reservoir characteristics exactly
45:44 you call the splits. Well, know, we'll try to agree on
45:48 but uh recognize that it's, we're arguing over it. The term low
45:57 turbo, I'm sorry, high density and low density turbo is pretty much
46:05 agreement. But with the understanding that low density turbo is pretty much only
46:15 turbulences, the high density turbo, turbulence has been dampened by the higher
46:25 sediment concentration, a muddy turb uh herd is mainly, um, associated
46:43 fluid turbulence unless you get so much that it becomes like a fluid
46:52 Ok. I'm gonna kind of ignore fluid buds. Therefore, I'm gonna
46:56 this part of the curve and we're see low density herds going all the
47:05 down to here and we might even in something in there. But I'm
47:09 , I'm gonna subdivide Herbs into three and they're gonna be right in
47:19 Now, we got uh debris flows well. We have cohesive debris
47:28 orally, cohesive and non cohesive. non cohesive are pretty important because they're
47:36 clean and they are major reservoirs, debris that are clean but poorly cohesive
47:46 clean but not as clean. They're reservoirs but not necessarily as good muddy
47:52 . Forget it. There's gonna be seals. Ok. So we've,
47:59 got fine grained, low density, , high density, sandy Turbos.
48:12 gonna ignore hyper pi nights for the being, but they would fall in
48:17 and we've got non cohesive and cohesive flows and those are gonna be,
48:23 got hybrid events best. They didn't for the first 30 years I taught
48:34 course. Now it turns out the existed. We never could figure out
48:41 they were. We'll talk about these and we're gonna begin right in here
48:47 Canada, a deposit or a low or, or supposedly a deposit of
48:56 low density thur bid current. This the classic BMA sequence Arnold Obama did
49:06 dissertation in the Alps. And he , he needed a shorthand to describe
49:15 of bits of sand or sand, cutlets. And so he came up
49:23 a sequence T A from acid TB plain bed T C for ripple to
49:34 sand and silt D for parallel laminated . And then he, he broke
49:44 into two types with all mud uh from the turbidity current and pelagic
49:52 So here's an example of that T T BT CD E. Yeah.
50:06 it turns out it's very rare to a complete sequence. And what bema
50:13 is to describe a composite sequence, typically didn't find it all be at
50:21 , but whenever you found them, always occurred in the order of his
50:27 . C was always under the and A B. Yeah. Now when
50:37 started looking at the BMA sequence published the early sixties, remember in about
50:45 mid sixties, we start thinking about regime. And so it seemed like
50:51 reasonable thing to do to interpret the sequence in terms of changing flow
50:58 just like we do with the flood going from high velocity to low
51:03 Uh We went from something in here super critical or upper flow regime,
51:12 massive to upper cleaner, to rippled plain deposition, something like that.
51:27 are the dudes? Well, I know Yeah, but we got ripples
51:32 the problem is these really aren't up flow REGI and as we'll come back
51:41 , this is something completely different. actually part of that higher density turbidity
51:51 . They all packaged in those OK. But we'll ignore them for
52:02 ? And so here are some of ways that they were found, they
52:07 hop truncated. I'm sorry, they truncated here. The base progress
52:21 here. The base could be Uh Here, they're truncated. So
52:36 get a A B ABC, et . Here we start with BBC C
52:45 a variety of ways of truncating. we tend to describe a bit based
52:53 call it A capital T A Now notice here it says e question
53:02 because I don't know for sure because wasn't thinking when I took the
53:08 this may actually be uh D E there's such an abrupt change here and
53:16 suspect this is the turbo is OK. So I think it's pretty
53:24 this. Now, here's a T C. That's the question. So
53:31 T BC. And what bema suggested that there is a proximal to distant
53:44 of turbidity currents giving you differences in kinds of turbos. Here's his master
53:53 . And right here he suggested, , we probably get the whole
54:00 but as we go farther away, we get a, then we get
54:09 ce D E by uh and what are, are base cutouts. They
54:19 , what we're looking at. here. So here we've got him
54:40 and notice the base is cut out and then this was cut out,
54:45 is cut out, this is cut . OK. And we've also got
54:52 possibility here of some cut out up . So the model really didn't fit
55:13 well. So instead, we're gonna at yes deposition of T A deposition
55:22 TB, maybe there was more, it's been eroded away, deposition of
55:29 D and E. OK. This a useful way of describing the downstream
55:39 and a current resulting in the downstream and the vertical sequence and of the
55:47 structures and grains. OK. So getting muds here grading into sand to
55:56 and eventually we're losing this. And this turns out to be more of
56:04 high density, then we're talking about high density to low density transformation with
56:12 . OK. Now, lo came and load and he was working in
56:21 , remember uh Bama was working in Alps and that tended to be a
56:28 system and it was relatively fine. . San you didn't get here,
56:37 in a coarse grain tectonic active setting you're getting coarse grain deposits and you're
56:45 what he described or what later was as high density turbos. And part
56:53 it was he had to figure out do the gravels fit into the BBA
56:58 . OK. So what he had a sequence of gravels and sand and
57:05 gravels were deposited initially by traction load then by suspension. OK. And
57:15 saw that repeated and like BMA, he saw the sequences consistent but they
57:25 all the same sequence. Now, , what he suggested is that we're
57:36 add on to this, that's that density portion of the turbo stop right
57:50 . Once it got into this it was a low density. And
57:55 , the full regime concept at least because that sediment transported by turbulence.
58:03 we'll talk more about that later. what he suggested and what now there's
58:10 on is that BMA A is actually composite, the uppermost part of a
58:20 concentration turbid turbidity current and then a concentration of turbidity current. And so
58:28 we go back to this, see that pinches out from this point
58:34 we're looking at the low density to here, let's say from here,
58:45 just high density in between its It's a transformation from high to low
58:56 associated with from high concentration to low . Yes. So he proposed something
59:04 like this, the high concentration versus concentration. And I've suggested that that's
59:13 what we're looking at here. So low and B we've covered most of
59:22 things we would expect from the deposition turbidity current, recognizing how they're gonna
59:29 with distance. Now R stands for or gravel. Uh And these are
59:48 and these are true, low density . Let's look at how that might
59:55 in a single event. Something happens we have high velocity motion of a
60:08 system. It's mainly erosion, but , there's gonna be the potential for
60:19 deposition of the Corus material at the above the erosion base. And that's
60:29 zone of gravels. So we've got the stupid part of the channel,
60:39 fastest erosion, we've got depth erosion then grabs mainly erosion and bypass a
60:50 bit of deposition. And then as slows down, erosion gets less and
60:57 and stops and deposition gets more and . So now we're gonna look for
61:05 kinds of deposits that we might get way down here, we're just getting
61:15 ABC that would be analogous to maybe here and farther down, we might
61:25 even more. But um as we from erosion to deposition, we're going
61:36 erosion to deposition here. And the initially is gonna be from the high
61:49 turbidity current the in the middle Yeah. Ignore what I said here
62:01 . It's gonna be the BMA sequence about. There we go from
62:11 high density to the brown sequence. B through E as we go farther
62:21 , we get actually this one Uh We get maybe DC uh CD
62:31 right here. OK. So we that bottom cutout which we saw here
62:42 of these is a her, her deposit. Who knows when we get
62:55 down to here. All we have gravel. Then we have what Lowe
63:02 here and here. So when you at this from gravel, The
63:13 which is, that's gonna be, , probably about here. You have
63:20 imagine this gravel coming out a little here. Ok. When you get
63:25 BMA sequence here, you're getting Yeah. OK. So the Baba
63:41 is just the down stream equivalent of high density tripartite that make your gravity
63:53 . And this is how it might like schematically. This again, this
63:58 just another example of how we see uh that bottom cut out here,
64:05 top uh cut out up here. we see the horse grain turbos classic
64:17 , fine grain turbos, low density currents, high density turbidity current.
64:28 is a diagram worth knowing because it a lot of information in an easy
64:36 understand shorthand. So when you see diagram think then about how this downstream
64:51 results in this sequence. And if do that, then I think you're
64:58 good shape for really understanding turbidity currents turbos. And you're ready to start
65:08 them in a larger packages which we'll , we'll try uh very briefly the
65:15 grain muddy turbo. Um They're broken into a sequence as well. These
65:23 um described mainly by, by Stowe others mainly grated muds to mix
65:33 Um, some convolute bedding down muds to silt. Mainly we're beginning
65:42 realize that dunes occur and turbidity crus not a surprise. Their size dependent
66:00 didn't see him because he was only at relatively fine grain sand. Does
66:06 sound familiar? We talked about similar in other settings having said that they
66:14 pretty high velocities higher than lower than plane, be higher than rippled bits
66:30 here. Now, in fact, found now cyclic steps forming in five
66:42 currents, upper, lower jeep. the reason why we didn't notice them
66:51 a long time is they, they're very restricted settings. Ok. And
66:56 I'm gonna talk about the settings in these occur. Let me just focus
67:01 on super critical flow deposits in channels notice the channel is going from the
67:11 to the base of slopes. We about how that can result in a
67:24 jump and within those channels. we've, we've seen very large
67:33 well, large transverse features and we've them long enough to know that they
67:45 eroding on the down wave site and on the up wave side. So
67:59 are those that forms and they're Yeah, let me rephrase it.
68:12 me uh I'll show it over Um They are scouring here eroding back
68:19 depositing here growing fork scour deposition, deposition, scour deposition. Let's
68:29 So now we've got those scour and cyclic steps within core divi charts.
68:46 . So, going back here, crescentic bed forms are typical of
68:56 They dip up streams and they are result of hydraulic giant. Ok.
69:11 this is where they're occurring. Why we not see that before?
69:15 we've never been looking in that much before and now we see them in
69:21 , in the subsurface. Well, mean, the ex uh surface as
69:26 , surface exposures. And this again just a an example I gave it
69:32 . But I want you to look these three slides in your notes more
69:38 they're really the the the best diagrams envisioning these um upper flow regime,
69:50 scale features, these cyclic steps. . Now we talked about high density
70:01 low density turbidity currents, but moody talks about high and low efficiency
70:15 And this is a confusing way to it because a low efficiency is a
70:26 concentration turbidity current and a high efficiency tracked is a low concentration permitted to
70:42 . Let's see what is going on with a high efficiency. I'm
70:50 Um With low efficiency here we do . Yeah. Uh with low efficiency
71:04 , it's got a lot of coarse setup, but very little fine rate
71:11 , OK. So when it stops , there's a hydraulic jump, oops
71:23 to have lost it. It's still . So let me try to get
71:30 to it. Mhm. Ok. we are. Um, we've
71:49 stop that a second. Yeah. . Let me see what I,
72:06 . Um, I'm just kind of this work on it. This,
72:16 , ok, here's, here's the jump supercritical flow again. And here
72:26 the cyclic steps in that channel. is right at the break of slope
72:37 that sand just dumps, doesn't really . But I mean, it does
72:42 transport very far because it doesn't have low viscosity that the entrained mud would
72:57 . So if you look at a viscosity, there's a much lower.
73:04 the high efficiency has a low viscosity can travel farther and the lobe itself
73:13 actually detached, it's got more See on the bottom, here's the
73:22 and we have a the tax zone then we begin to have the deposition
73:30 the Yeah, they transition from slump Deb right to a coarse grain
73:51 medium grain turd, fine grained shown is something that you should be able
73:58 envision especially with high efficiency flows. we don't see here though is what's
74:11 on in that sco zone at the and slope. So we're gonna go
74:18 for that. But before I I realized I still really haven't described
74:29 debris flow into things. That's the lowest part where it's laminar inertial
74:39 I've said earlier that laminar flow is nonexistent in nature with fluid flow.
74:48 this is not a fluid flow, is a gravity flow and the viscosity
74:52 so high that the rentals number is low that it's lamber. And so
74:58 can have things like floating peppers. so just to recap, when we
75:06 about debris deposits from debris flows, either cohesive if they're muddy or non
75:14 , if they're sandy or maybe something between. But I'll mainly talk about
75:19 Deb rights and muddy Deb rights for . Just recognize this. It's
75:27 Now, a non cohesive or sandy can include structures that we used to
75:33 liquefied flow deposits. Now I can con betting it can have pillars that
75:43 the result of I can't draw on uh pillars. Yeah. Yeah,
75:56 are water coming out by uh fluid . We have these dish structures which
76:03 little lamination that were broken up by upward flow and we see it.
76:14 see him here. Uh-huh Little features . These are all fish books and
76:31 we've got what is called, you him over there. So it's kind
76:38 easy to visualize on the very You may have had black nominations.
76:46 as it begins to dewater both lamination broken up. It's a little almost
76:51 mud chips. And then finally, water forms these little pillars of
77:02 So when things were real simple, could describe a cohesive de right,
77:06 this. And then on the the ideal now, we know there's
77:17 lot more variation in that cohesive. sorry that that cohesive uh muddy turbo
77:30 those other features that we saw the , basically the fluid eyes and liquefied
77:38 . So what we used to call separate type of flow uh is now
77:46 to be a non cohesive de Cohesive, dead rights remain pretty
77:51 They're basically floating mud matrix, that's cohesive matrix, supportive conglomerate form,
77:58 it's also a cohesive dead, Uh It can change vertically. There
78:06 a lot of complications potentially in None of which I'm going to
78:13 Um We can see some of those again, I'm not going to discuss
78:20 except to remind you that at the bottom you may have uh or rather
78:30 at the base. You see a that's typical. You can have a
78:35 inverse to normal grating. That's Then you can have rippled at the
78:41 and then no uh turbos or rather non. Uh yeah. So there
78:49 some vertical uh change that can be . I'm not gonna expect you to
78:55 any of them. There's a muddy , right? Sandy, uh more
79:01 de, right, muddy de things think about. Uh the massive clean
79:16 can be deposited by dense liquefied but more typically in high density turbos
79:25 a small change in the amount of as a profound difference on the nature
79:32 the deposit. And departures from the models of BMA and low are
79:44 Now, having said all that de , high density, classic, low
79:53 under different names, I've told you you need to know. I've told
79:57 more than you need to know, that is a package. They
80:06 all, every one of those could fact be the result of a single
80:11 with down flow changes. We still cons and I've inserted now, something
80:18 we didn't even know about when Galloway working. And that's a an A
80:24 B A hybrid event. Bet these sedimentary gravity flows that were emplaced by
80:36 combination of turbidity currents, transitional debris flows all part of the same
80:42 but mixed up. Not necessarily in nice sequence that we talked about.
80:51 can vary from poorly cohesive and essentially to increasingly cohesive and turbulent suppressed.
81:04 the flow transformation is driven by the corporation of clay or so. In
81:11 sense, this is similar to what talked about earlier except earlier, we
81:17 talking more about the change in viscosity to the incorporation of water.
81:24 we're changing the flow from mud cohesive non cohesive and back by modifications of
81:33 amount of clay in mud class. these are just some examples of how
81:41 could change down and notice going from density turbo as we begin to incorporate
81:54 lot of mud due this scouring, got this H E V. So
82:02 density turbinates can be transformed into H V s by incorporating different amounts of
82:14 . And there's a fairly consistent sequence a low clean the to and there's
82:27 lot of details that we go, describe them slightly differently. Just pick
82:34 of these, look at the division look at the interpretation and you'll be
82:41 . Now as far as looking at , um the lower part here
82:47 is a turbo, then it goes a Deb right, as opposed to
82:56 left, which is a turbo debri debri. Here it went turbo debri
83:06 in ours. You're getting changes in amount of play as well as water
83:12 it turns out giving you an unpredictable for rather a uh more complex
83:21 So here we have the flow transformation concentration uh decreasing the flow run
83:30 That's the typical Debri tour. Here's hybrid of that, the concentration is
83:39 increasing because of the increased mudd. downstream, decrease in concentration, the
83:49 current downstream increase in concentration, hybrid . And these are just some of
83:55 same things. And I, I'm let you look at those, but
84:01 , I'm, I'm gonna pause. I'm gonna quit here where we look
84:08 . Yeah, reservoir characteristics of these types. Uh We've got debris
84:18 hybrid flows, high density TBI currents and low density. Look at
84:28 different ferocity and perm and permeability your permeability sitting up here is a high
84:40 turbo because it's clean sand, the gone away and their course are
84:53 The low density turbo is finer grain , but the lower part at least
85:01 in fact well sorted and relatively The mud is sitting there with the
85:08 . The hybrid events near the source is approximate up current areas have a
85:17 amount of sand, but they do incorporated mud. The upper part,
85:23 farther you get down flow, the mud is incorporated. Until finally,
85:27 get to the Deb, right, is the floating pebble matrix.
85:34 Um Oh Not necessarily family but as . So what we see is the
85:46 porosity and permeability is your high density . And then as the grain size
85:52 and the clay content increases, we lower porosity and permeability. Now,
85:58 is ignoring digenetic changes. Turbos are any other sandstone depending on the composition
86:06 the sand, which ultimately reflects the of the sand. The digenetic histories
86:12 affect the porosity permeability. We've seen in neo deposits, fluvial deposits,
86:20 deposits. Uh We'll probably look at later with turbo. Um So this
86:28 just uh a different way of looking the uh sequence except now we've added
86:38 other type of turbo a reworked In other words, after that,
86:47 that high density and to a lesser , low density turbidity current is reworked
86:56 All right. It doesn't necessarily change size, but it increases its sort
87:05 the finer grains can be winnowed And so reworked. Turbos are those
87:12 that have been winnowed by some typically bottom currents. Ok. So
87:22 gonna be the very best to be and they're gonna have the highest porosity
87:27 permeability. Uh And that diagram is shown that diagram is kind of complex
87:37 visualize because you're, you're super imposing . Uh And um We've got up
87:51 40 Down to 20% from $5 million million dollars seats, horse grain,
88:04 , sort of fine grain or now last quote turbo is really not a
88:16 . It's sometimes called a mega It's essentially a slump that maybe has
88:22 that maybe has find up because these big events, these are infrequent
88:28 These are events that are m to m high fit uh and may extend
88:38 an entire basin. You go to Delaware Basin, you get this,
88:42 radar uh conglomerate. These are big of limestone, premium, shellfish,
88:51 that fails. And as the shelf , it was distributed this quote mega
89:01 uh across the entire basin. It's a mass transport complex. Yeah.
89:09 There's one more hyper pic nine, you what I'm gonna stop here.
89:16 just crapped out. Uh I'm gonna about hyper pic nights and contour rights
89:23 the last examples of types of And then we're gonna start on
89:29 I haven't posted yet looking at the of deposition, where do these events
89:37 ? How do they relate to them time and space? And that,
89:42 then we in doing that, we'll into reservoir examples, field examples.
89:49 . So I'm gonna stop here. can stop
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