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GEOL7330 Potential Field Methods - Day4 01-28-2023 AM
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00:00 Can everyone see my, did everyone my screen? Great. I guess
00:13 uh any questions about yesterday that you saying that some of that three
00:20 modeling stuff was a little heavy. yet, I haven't had a chance
00:25 really go through it um deeply. hopefully this week I'll email you some
00:31 if I have any if you do then of course if you if you
00:36 to look at some of the literature I think I cite everything that I
00:40 about um at least anything that I a side of figure out. I
00:46 that. So you know you can at the you can ask me of
00:51 and then if you're interested you can read about that stuff so it's up
00:58 you. I don't really test test those methods though so I might,
01:06 anything I test you on will be the notes so probably you know to
01:13 for the exam I guess that will friday right? That will be
01:18 Um Over the first four lectures. everything through yesterday um which is basically
01:27 the all the background material, the , instrumentation, acquisition, processing and
01:37 you know interpretation tools like not only and depth to source estimation um And
01:48 and modeling um Yeah so all that will be in friday's and I won't
01:55 you anything that I didn't lecture on not in the notes or that I
02:00 talk about but I think I pretty speak. I don't I don't get
02:07 on tangents too much I don't But um so like to prepare,
02:13 mean one of the things you could , you could just like outline those
02:16 . So because it's gonna be, gonna let you use your notes,
02:20 take the test. So the test be whatever, it's supposed to be
02:24 hours, right? That's what they looked at. The time for Wednesday
02:29 like 7-9. I mean 6-9, like that. So it's like three
02:35 . So I thought well the first would be the same if that makes
02:41 . So you're allowed to use your for that. And so if you
02:47 have a nice outline of them, know, slide blah blah slide whatever
02:52 whatever I talked about this and um know, maybe maybe if there's an
03:00 in that group, maybe the citation that, you know, just the
03:05 reference to it and that way you'll able to zip through your notes
03:11 Um And it will be useful for . So yeah, but I'm not
03:17 like, you know, I mean might I might ask you a question
03:22 to make you think though. So anyways, yeah, don't freak
03:29 though. I'm not a I'm not tough greater so in any case.
03:36 , so no questions about any of stuff, right? You you're
03:40 you know all of that stuff inside out, right? Hopefully by
03:48 Well um but the exam isn't until . No, I feel like I
03:56 like everything's pretty legible. So I have to go through it just one
04:00 time slowly. And if I have questions, I'll let you know.
04:05 then. So that's the first half the class. That's all the background
04:11 , the stuff you need to sort have a feel for, to start
04:18 at data. And even though I , you know, Sprinkle in a
04:24 of examples specifically, you know, regard like potential and, and kaos
04:30 all that sort of, all the stuff. I like to try to
04:33 that to show, you know, these ideas are applied, how they
04:40 been applied. Um, I really that you need to look at lots
04:45 data to really get a feel for . And, and so I think
04:51 sometimes folks that teach potential fields, kind of focus on, you
04:59 theoretical parts and not as much, show, just looking at lots of
05:06 . So with that idea is well, okay, lots of
05:10 How do we look at. And this is where I talk about,
05:15 gonna look at different kinds of we're gonna look at today, this
05:20 , gonna get platform based. And afternoon we're gonna look at rift basins
05:25 passive margins and ocean basins. And we're gonna do the exercise. Next
05:32 morning, So next saturday afternoon we're look at basins that form along convergent
05:42 boundaries. And then um as well what I'm calling complex bases or bases
05:51 complex histories. So we're basically going like the Wilson cycle, the supercontinent
05:58 uh this afternoon will be like the apart of of super continents. And
06:09 saturday we'll be looking at convergence of Creek tonic blacks to form big continental
06:18 to form super continents. And and , you know, the complex
06:25 there's like other things that can happen that we need to think about
06:31 And then the final action will be week, a week from friday.
06:36 then we're gonna look at, it's of a specialized lecture. We're gonna
06:39 about gravity grade geometry and heat He he flow is a potential
06:48 And so we're gonna talk about that thermal properties. So, okay,
06:53 we're gonna look at, we're gonna today with super continents and plate
06:57 And then we're gonna look at basin schemes. Uh interpretation rules of
07:05 you just some ideas that you should have in your head. And you're
07:09 at gravity magnetic anomaly maps. And earlier when we were looking at processing
07:16 , I said, you know, crossed through ISIS static correction and I
07:23 , well talk pick that up later I have a few slides to explain
07:26 I meant by that. And I'm it in here in sort of like
07:32 sliding it in between like uh you , interpretation rules of thumb and you
07:39 , plate tectonics and all this geological . Um And then before we start
07:45 looking at all these different kinds of and putting it in here because I
07:49 it is kind of an interpretive uh of gravity magnetic specifically gravity interpretation and
08:02 is not a processing step. And will understand why I want to explain
08:06 . And then we look at our look at platform basins which are photonic
08:12 . They don't I mean they they're really they're separate from basins that form
08:19 response to plate tectonics. They have , they live for longer. Um
08:25 there they form on what would would quote stable crit tonic platforms. So
08:33 why this name platform, but sometimes called crustal sags or cra tonic
08:40 But basically they're just shallow regions on a stable plant, stable cretins,
08:51 just collect sediment. And anyways, start with those, Get those out
08:56 way, then we'll jump into the kind of soccer ones. Okay,
08:59 alright, so a lot of introductory , so here's here's my basic thesis
09:05 looking at organizing this this material in way and I think that a person
09:15 interpret gravity magnetic data over any sedimentary without a priority information provided that the
09:23 of basin is known in other all you know, is that it's
09:26 four land based and you have gravity anomalies over you. You can actually
09:33 at those data and you can in geology just because you know what kind
09:40 a basin it is. That's the . That's my idea. So,
09:47 know, as I say here, know, you can, you
09:51 you can you can estimate things like depth. Right? Remember we thought
09:56 did depth estimation. You know, basically, you know, the wavelength
10:02 effectively, or essentially four times the depth. And then you can infer
10:08 , jeez, you know, maybe sor salt or carbons, things like
10:12 . So, remember we looked at some intrusive intrusive analysis produced by intrusive
10:21 like that. So that's the idea with with the basic understanding of regional
10:30 and how these basins, what their is, how they form those sort
10:36 , you know, the processes that them. Then you'll be able to
10:42 any kind of gravity magnetic anomaly map say something that will impress your
10:48 Absolutely. That's the idea. That's goal. Okay, so let's start
10:53 plate tectonics and supercontinent. A lot the stuff is the review but I'm
10:58 take a grab meg centric viewpoint. , so we start and we look
11:04 this famous map. This is this is a reproduction for moore's and
11:09 their textbook. But these surveys were in the late fifties. Uh and
11:14 papers were written by mason and rafe were pioneering and what you're looking at
11:21 sea floor spreading anomalies. Now mesa and twists from this textbook. They've
11:30 touted them up in terms of how they are um in this in this
11:38 and these would be these would be floor spreading anomalies and this would be
11:46 age correlation. So you know, going back to Whatever over 10 looks
11:54 about 11 million years. And and this, here's the spreading center right
12:00 , the wanda Fuca spreading center. as you can see, everything is
12:04 of mirrored, right? Everything is know this gray is this gray,
12:09 like this is this light. It's little bit of an offset here because
12:14 transform. Right? So this this really sort of, he was like
12:23 of nails in the coffin for those rejected plate tectonic theory at the
12:30 Late late 50s, early 60s. what really hammered it home was there
12:37 a there was a special issue of . G. R. In
12:41 They had a bunch of papers in . Uh jim her clothes paper was
12:46 of those paper night uh where they ocean magnetic anomalies around the world.
12:55 , now gravity data especially more recently really just been incredible for identifying uh
13:06 basin structures, particularly fracture zones. transforms as you probably know, they
13:13 spreading segments in the ocean basin. the off axis trace of those transforms
13:19 preserved and those are called fracture They're not active. There's no they're
13:25 like strikes the thoughts like I mentioned but they do record the relative motion
13:33 the two plates. So like if curves in one direction and the other
13:37 it will curve in the other. will it will have like an inverse
13:42 to it to sort of mirror that . So you can actually you know
13:48 can what you do, what we in practice is we map the pole
13:51 for each of those little segments called poles. Okay, so This is
13:59 Hertz or 68. And this is this is just really incredible work because
14:05 we have what you're looking at is models of the geomagnetic polarity reversal
14:14 That's the strip of black and white where black is normal polarity present day
14:23 white would be reverse polarity and it's same stretch but at different spreading
14:28 Right? So you know the ocean open at different spreading rates. But
14:33 the same the same correlation. And what her killer and these other guys
14:39 . They took this and then and and then just above that that model
14:48 polarity reversals is the forward calculated response it right? Like as in forward
14:55 . So the profile directly above it the is the model profile for all
15:00 these. And then what they did they took real data and and and
15:06 compared it and you can see that can see what they're comparing. They're
15:12 one for one. But the way look at these things we look at
15:15 of anomalies right? So there's two in the southern indian ocean this one
15:20 the south atlantic and with different spreading and then in the in the pacific
15:27 two profiles here and what they demonstrated that the same geomagnetic polarity reversal scale
15:39 its forward model can use the used correlate real world data over all these
15:45 basins and what what how can you that unless there's something like plate tectonics
15:52 on. So this was really just really really important work that I mean
15:58 data and gravity data really contributed And to contribute towards plate tectonic theory.
16:05 it really advanced it with this work . Now. The famous paper I
16:10 it's vinyl Matthews which was 1966 I which they really postulated a lot of
16:17 ideas. There was plenty of there evidence but this special issue of
16:22 G. R. 68 was just I say nails in the coffin of
16:27 sync lie in theory. So it's important stuff now here's here is gravity
16:35 over the world. And um the areas are covered by satellite derived free
16:42 gravity. Uh The latest version were the latest but One of the
16:49 most recent versions was just released in by David Sandwell. And you can
16:56 all the fracture zones. So like the off axis traces, right?
17:01 not active, right? This is african plate. And these are not
17:05 a bunch of little strike slip I'll explain that very clearly when we
17:08 to ocean basins um this afternoon. and then you can see, you
17:17 , you can see the Hawaiian Emperor chain. There's all these other seamount
17:21 which are kind of like sub parallel , you know, this shape here
17:26 that shape there, that shape you know, this kind of bends
17:29 here, The Louisville going into the Tonga trench here. Uh And then
17:36 floor spreading in the southern ocean and the indian ocean of course central atlantic
17:43 the East pacific rise is really, goes up through here. It's not
17:48 well defined. And the reason is it's just a faster spreading center.
17:52 morphological e there, they look different like the slow spreading centers of the
17:58 atlantic and indian ocean and the southern ocean is a bit faster. That's
18:03 it's a little bit smoother as well . So remember these marine areas satellite
18:10 is derived by the satellite not having gravity meter in it, but it's
18:16 the height of the ocean's surface the surface and over. Lots of lots
18:21 lots of missions and stacking that data . This is what they come up
18:26 . So it's very beautiful. you know, I mean, you
18:29 definitely see the tectonic processes going on the onshore areas. Okay, you
18:35 do those with satellite. I you could but it wouldn't be useful
18:39 , you know, the the topography not coincide with the GE OID and
18:47 what these are are actually there are OID measurements in here and then that's
18:55 with some earth to modeling by the one is Earth gravity model 2008 Palace
19:04 others 2012. So this is free marine in bouquet uh over land
19:13 And of course you can see in land, you can see that the
19:16 ranges, how they're rooted right offset into the they're off, they're
19:21 setting deep mantle as well. Now low anomaly, that's not from a
19:28 . Well, I guess there's there's mountains there, but it's also
19:31 you know, there's a mantle plume which is really hot and it's going
19:34 be low density. So that's kind a complicated area. But the Himalayas
19:39 deeply rooted and other mountainous areas. can see and then where the mantel's
19:44 up our big broad hotspots, broad hot spots. They're big,
19:50 , high, high amplitude of gravity areas. Okay. So we can
19:56 at this with the plate boundaries in and this is not me. This
20:01 peter bird, he's the famous I'm not the famous one. Um
20:08 the gravity down these are gray And then and then there's a kind
20:13 a yellow shade on top of that the continental areas. So this just
20:17 you all the plate boundaries, you ? So this is the this is
20:22 south american plate right here. It the continent and it's part of the
20:28 atlantic ocean. The african plate includes this stuff. Right? So in
20:35 in the, I guess where the plate, the antarctic plate down here
20:40 the pacific plate out here. This the Nazca plate, This is the
20:44 plate. The juan de Fuca Is this little tiny one up
20:49 Um Yeah. And then there's a of, there's a bunch of the
20:54 sea plate here, there's a bunch them over here. It's just a
20:58 a real mess over there. well, you can also, I
21:03 , you can download all these shape from here, but here's just color
21:08 the plate. Different plates here. you can see from gravity and then
21:14 color filled. So what is a plate? Tectonic plate includes the crust
21:23 lift this fear or the upper mantle we say. Um And the little
21:30 Tennessee, they have 70 kilometers That's okay, I guess. But
21:34 little sphere tends to be about 80 or minus 10, I reckon kilometers
21:41 beneath ocean basins. And it can it ranges from 100 250 even over
21:48 kilometers thick beneath continents. So those little spherical plates. Sometimes folks
21:56 get a little confused or they forget they start thinking it's just a
22:02 just just the uh just the crystal crust that is what's breaking apart and
22:10 around and abducting stuff. No, the crust and the upper mantle.
22:16 it's very important to understand that because that's what plate tectonic theory is.
22:21 says that the earth is capped by sphere plates that are in relative motion
22:28 each other and that those plates are along their boundaries and longer boundaries is
22:38 of a term of art, I . I mean basically the deformation can
22:45 typically arranges for hundreds of kilometers. can be more, but you
22:51 not like more than whatever, 600 something like that. Well, if
22:57 count both sides, it can be of yeah, maybe 800, maybe
23:04 if you include both plates. Right, so that's how it
23:10 That's how plate tectonics works. So is, here is um there's three
23:16 of boundaries of course there's divergent there's convergent boundaries and then there's translational
23:22 , right? So here's an example a divergent boundary. Here's the status
23:28 , here's the litmus fair, there's crust and lower crust and this is
23:32 , this is a this is a of sea floor spreading center. They're
23:38 always ridges. I typically like to , spreading center because sometimes their depression
23:44 in this example, sometimes they are and their higher. But you
23:49 so you have in this little rift . In fact this is this is
23:54 I'm sorry, this is not this is a continent. But but
23:58 any case, the idea is that you break a content apart, you
24:02 , you cause a rift basin and mantle up wells and you you
24:08 you know, lower crust upper I'm sorry, this is a mid
24:15 . My bad. I just I read my I should have made my
24:20 . Yeah, so this is so is layer two which are basalt,
24:25 dykes. And layer three we typically are the gap grows and go
24:31 rocks are in lower crust beneath the and oceans. And then they have
24:37 pillow lava in here that they put were which were produced which were created
24:43 the the salt first erupted it and into contact with the ocean, ocean
24:50 , sea water. And then the sphere gets pretty thin by the time
24:54 get to a sea floor spreading But at the spreading center, the
25:01 is that once you start producing ocean , as I said earlier, rifting
25:07 and at the spreading center as the basin opens. The little sphere
25:13 you know, supposed to be zero , the crust and atmosphere are
25:17 Think. Okay, so we can at an example of diversion boundary at
25:27 at an incipient diversion boundary. So this is the east african rift,
25:32 is it's still a rift. It's a plate boundary, but it's very
25:38 . You can see that there are rifts strings, if you like that
25:45 off of this. It's just this zone here. This whole zone here
25:50 a rift zone and you can see probably on the order of 1000 kilometers
25:55 , but it's to both sides of plate boundary. Okay, so we're
25:59 down here at this very um this of this rich strand that extends out
26:05 in the Okavango rift and here's a image of it. And you can
26:10 it's kind of like it looks like kind of asymmetric with a steep side
26:15 and kind of a shallow side And there's some really beautiful magnetic data
26:25 this over this rift area. So is the first vertical derivative. So
26:30 what does that do? It kind just squeezes anomalies. It just makes
26:34 sharper. Right. And what's C. B. I mean,
26:40 is the first one is also the vertical derivative. Okay, and you
26:45 several cross sections here, but but at the data. Okay, what
26:49 you noticing in the data first of , you see that there's a bunch
26:53 features that kind of track along these boundaries. And especially down here.
26:58 we're going to show a map of and what these are. These are
27:02 folds of the rocks. And in , this is this figure to the
27:08 . You can zoom in. And course you have these these cross cutting
27:13 here. Well, these are dikes are actually older than the present day
27:19 . And if you look closely at map here, you can see
27:23 You can see it in here. the rift is down. How do
27:27 know that? We'll look at these . They're very short sharp wavelengths and
27:32 of a sudden things kind of smooth in this zone here. Right?
27:37 then these are actually, I think estimates to the base. I think
27:42 I think that's what these are. haven't, I haven't had my
27:51 Um Oh yeah. It says the showed the depth and meters to the
28:01 of the dikes obtained from the three . Euler. Right? Yeah,
28:05 you. Thank you. Yeah. these are depth estimates. So it's
28:09 it's down about 400 m on that to well, 200 to 600
28:16 about a couple 100 m. It's down. But you can see it
28:20 the data. It's smoother. You . Can you see what I'm talking
28:24 here? Yes. Mm hmm. that's that's a very beautiful man.
28:30 if we look at this other area here, these are the folds that
28:35 was talking about that. I I mean, it's just beautiful.
28:41 show the the, you know, they're sort of plunging and then the
28:45 of where they have some fault geometries here as well. Too much the
28:49 basement taxes, what did they look ? Phones And then there's a they
28:54 there's a fault that goes through here then on the right here,
29:01 this is let's see a to a . So that's up here. So
29:05 we're gonna look up here at this section and that's a that's also got
29:10 data. That's what you're looking at . So this is the miller
29:14 And you can see that the basin pretty shallow basin, but it has
29:22 high that's running right straight through it . What does that look like up
29:26 ? Um, there's the correlating magnetic as well. So, you have
29:36 hi that's produced by, that produces gravity anomaly as well as a magnetic
29:43 . So, I think this this probably a reasonable idea. It's a
29:48 basin. So you have the broad of the basin here. And what
29:54 this remind you of? I showed of something else. What does this
29:57 remind you of for gravity. I remember, but I don't remember
30:09 it was, where the top the dome is uh is above the crossover
30:18 where it's more dense than the sediments it that same shape. But in
30:24 case, because this is all this a rift basin and it's all crystal
30:29 down here. You have to assume there's some higher density feature. And
30:35 saying it's a it's a it's basically composition thing. And I tend to
30:41 . And the reason is because it's a gravity anomaly and a magnetic
30:48 Does that make sense? Yes. here's a little, just a little
30:55 of a rift basin and some really magnetic data, gravity data is
31:02 I guess. Um uh that's something write home about. I mean,
31:06 probably better than open file. This real data. It looks like real
31:10 . Um So yeah, okay, convergent markets, another, you
31:17 another kind of plate tectonic boundary. of course, you know, convergent
31:25 are a bit more messy. I mean, the thing about riffs
31:30 ocean spreading centers is, is um, is that it's kind of
31:36 everything's opened up and laid bare for to examine, right? Whereas in
31:41 margins you got stuff just piled up top of everything. So everything is
31:45 up together. They're really more but there, I mean, passing
31:50 and foreland basins are the biggest producing on the planet. So they are
31:55 basins. But for me what you , of course, if you have
32:00 in this case it's an ocean ocean zone. When you hear people say
32:10 , they're talking about continent, continent , oceans don't collide, they just
32:16 ducked beneath them. So that's kind a yeah. So anyways, the
32:22 litmus fears, you know, plunging this edge of this continental crust up
32:28 in with this fear. And of it, you know, it starts
32:33 melt and there's decompression melting and you a bunch of magnets probably will create
32:39 sort of magmatic arc. Now this ocean ocean, it would be like
32:43 island art, but in this case would be, you know, like
32:47 like the sierra Nevada or the or , you know, the Dean,
32:58 like statistics taking me out. But but you know, from Mount Adams
33:06 rainier and uh hood and uh um those those that mountain range in northwestern
33:17 and and into the Canadian rockies in case. Right? So these are
33:24 mountain range. And then just um of that are foreland basins.
33:29 So they form their typically asymmetric with deepest part, right, right near
33:34 foothills. And then outboard is typically we call four arc basins for land
33:41 arc. And then and then of between them and actually ocean florida is
33:47 often a trench and that might be with sentiments called discretionary with wedge.
33:54 yeah, that's that's the sort of tectonics of it and here's here's a
34:01 example of that. So this is the in the Andes in um Chilean
34:07 they call them. And The contours the Chilean Pompeian flat slab. So
34:16 subduction slab is okay, here's where trenches and it's supposed to be 7500
34:23 to 110, km deep. It's to sort of flatten out right
34:30 That's what these guys are talking about . And then there's a two D
34:34 model between these red tick marks and of course there's some map structures
34:39 some some thrust right so the thrust plunging or dipping to the west beneath
34:48 these other ranges. Now the Precor ra it's also called the korean
34:55 Um This is actually some terrain that with with where we're sitting right now
35:05 uh part of Southern Lawrence to part north America beneath um between us and
35:19 , you know florida or Mississippi and . This is a bit and it's
35:26 well studied. This actually came from . You'll see what I'm talking about
35:29 a minute. Okay so we can at that profile, it's fairly
35:35 So here's the koinonia, the Precor as I said and then there's this
35:39 Pompeo now the subduction along the western of south America has been going on
35:49 a very very long time. Um think the the campaign or a jini
35:59 is it in here was, yeah it was carbon difference. And then
36:11 is that right? And no no that's not right. It was older
36:14 that. But in any case you see that there have been successive or
36:20 events and pre cordelia. That was when chile and uh was was basically
36:32 up along the southern coast of north . Okay. And then later during
36:39 guns want and and when like Patagonia in the south America. That's when
36:47 this stuff happened. So yeah. anyways they have interpreted they took some
36:53 but you know there's I guess there's guess there's some earthquake activity here.
36:57 what this stuff is. And um see what they did with that.
37:03 the bottom profile is gravity as well so much the other models, we've
37:10 looking at the tapas, Magnetics, lines are observed data which is the
37:17 sometimes you see it the other way but it's typically dotted lines and the
37:21 is that they're supposed to represent stations ? And then the model response,
37:26 gravity and Magnetics and um the thing bugs me. Okay they have put
37:34 some densities here but not all of . Um But yeah they have put
37:42 some densities. The queenie is lower compared to the other ones. And
37:46 what's producing this low through here. have a little base in here and
37:53 a lot of these things seem to topographic though. But now this is
37:59 . So this is definitely this has be bouquet I think I land and
38:04 here's yeah there they have been you they've got to be putting in a
38:10 of different sort of magnetization. But it looks okay. Now if you
38:15 at those on the maps on the is magnetic data. And that's really
38:19 magnetic data on the right is gravity but it says vertical gradient but I'm
38:26 sure what the source is. It a little suspicious to me. But
38:30 any case you can see those structures they map on the first map.
38:34 can see those in here and you see that there are correlations little bit
38:40 on the gravity side. But that's a pretty interesting stuff. Um
38:47 let's talk about transform boundaries and we're familiar with the oceanic transform boundaries right
38:54 you're connecting to spreading centers. So is the transform the active part in
38:59 off axis. As I said the fracture zones, they are not
39:03 , right? But some transform boundaries penetrate through continental crust. There aren't
39:11 lot of them. Um Most transformed bonder Zarin spread our ocean basins that
39:19 spreading centers but there are a The san Andreas is one of the
39:23 ones. There's also the Anatolian the Anatolian fault which which basically traverses all
39:30 northern Turkey and uh and through Greece it still is still forming, it's
39:40 connect, you know, it's going connect into the mediterranean, there's a
39:46 south Anatolian segment south of Turkey and connects up with the dead sea fault
39:52 is another transform. And then the really famous one is the alpine fault
39:57 goes through the northern and southern islands New Zealand. And that actually connects
40:03 subduction zones of opposite polarity. So pretty hairy what's going on down
40:08 But we're gonna look at that, gonna look at this area here in
40:13 . The northern part of the san . Um SAn Andreas comes up here
40:18 then there's all these other faults that off these. Remember the edges,
40:24 of the plates are deformed and it out they're even deformed under,
40:28 Quite often, you'll see people draw boundaries through continents as a single line
40:35 that's just not the way it These transform plate boundary, all the
40:39 I mentioned, There's a handful of ones but they all produce broad zones
40:45 discrimination. I mean think about this the atmosphere here is over 100
40:50 thick. So and that's like two going past each other. So you
40:55 the deformation what's going on. There to be really crazy to offset 200
41:03 or 110 km or whatever it is of. Let this fear. So
41:09 are all related to the san. boundary transform boundary but they are in
41:15 deformation zone. Right? So let's at those. So here is the
41:19 map and they're basically draping these colors top of the topography just to show
41:25 there's a lot of interesting features So there are the white dots are
41:32 thoughts from gravity data inferred faults and I guess this famous Petaluma fault which
41:40 this gray fault right here and then and there's a bunch of exploration wells
41:46 are you see these circles that I'm it there appear there there are more
41:52 more. There's gotta be more. can't see them all. Yeah here's
41:57 here's 1 is 3341234. Probably find of hysteria. Well let's look at
42:06 let's look at the gravity. This static gravity contoured at 2.5 million
42:13 So this is pretty I mean it's good data to contour that that
42:18 But I mean you know it's a , I'm not sure what that
42:22 I mean it means that it means took out some regional that correlated with
42:29 . That's what that means. But really don't know much more about it
42:32 that. And I guess there's details the in the paper. Um Right
42:39 this is why they're inferring these faults these data line because it's all these
42:43 gradients in this data. So I disagree with that at all. Um
42:49 like there's some other things going on in general you have this broad high
42:56 but then there's like this this kind a low region so there may be
43:01 component of dip along with this this sort of defamation. And remember I
43:06 the SAn Andreas is out here. so let's look at the MAG data
43:14 the mandated. Um So one thing might notice when you compare gravitated to
43:20 data, gravity data always looks like a little smoother than magnetic data.
43:25 the reason for that is because the data are mono polar gravity All put
43:32 gravity points to the center of the wherever you're at. Whereas magnetic data
43:37 die polar. So remember our anomaly that from in the northern hemisphere southern
43:44 there where the where that phase shift from a peak at the pole to
43:50 low with the equator in between. have a pair of anomalies. That
43:55 of means you have two anomalies for you might have one another gravity.
44:02 that's why magnetic data typically looks like just got more more detail is because
44:09 got two for one you got you you got high low pairs in
44:14 Now I don't know I think this be our T. P. I
44:18 I imagine it is but here they those gravity falls black dots instead of
44:25 dots But again everything else is the san Andreas is down here and there's
44:31 lot of correlation. I mean you you know I mean there's there's a
44:34 of detail here that they're you know mean it's one of those things like
44:39 said you could spend a lifetime looking this data but it's really nice because
44:44 see that this shape here from the this bit here really can be you
44:52 looks a lot like this area here this is another area where it's low
44:56 yellow. And so that's interesting. let's look at these wavelengths. I
45:01 you have a broad low here but you have some stuff superimposed on
45:06 So there may be some shell What does the gravity look like?
45:11 uh I don't know I mean there two things that I think of when
45:15 look at this I think that. it smooth because it's just deep or
45:20 it smooth because there's just no And my sense is that there's no
45:25 . It's just just it just gives that feel maybe. I know but
45:31 sure looks. It sure looks suspiciously . And same with the mag.
45:39 they probably just don't have data over but there are some very short wavelengths
45:46 here so that stuff is really shallow then you have you know you have
45:51 longer wavelengths like down in here um here things are smoothing out this is
45:57 low low longer wavelength. A little . So this down and then down
46:02 as well so it looks like basement are going up and down up and
46:08 . Um There's sort of in the of these inferred faults look like you're
46:15 gonna have some transgression, right? tension. So it's very fascinating
46:24 What's next year? Okay. So is there any questions about any
46:28 these uh my my little sort of bag centric view of plate tectonic
46:39 No, not yet. I like . Okay. You are you do
46:43 like you enjoy this material? I do. I was like like once
46:47 figured out what this class was I was excited. Oh really?
46:52 good. Alright so we looked at tectonics but there's a bigger story and
47:03 and it's uh the supercontinent cycle, does this stuff work? Okay.
47:07 mean think about it if we accept idea that the earth is kept by
47:14 Pittsburgh places that are moving around? sort of begs the question, when
47:18 this stuff start? I mean, know I mean Earth was created 4.5
47:22 years ago. Did the plate tectonics right then? Or was it later
47:27 ? People think plates plates started I was talking to some guys at
47:33 A. G. U. Um last month. In in in
47:43 And one guy, one guy said he thought plates started. They found
47:50 what did they say? They found material. The first continents formed Like
47:58 Wanna say 4.2 just You know not 300 million years after the Earth
48:08 Which is amazing to me. But people think the consensus of the you
48:14 the folks who worry about this they think that plate tectonics started about
48:20 gigi years. So so having continental forming, you know, half a
48:28 years. I mean I mean after earth form, you know for four
48:39 4.2 or whatever it is. I That sort of works because I mean
48:45 if plate tectonics started 3.2 you had have the plates, plates had to
48:49 there first before they can start moving . So that sort of makes
48:54 That's pretty fascinating stuff. Um Yeah J. 2's O. Wilson,
49:02 Canadian geologist, he was actually anti tectonics initially. But once he once
49:10 was given enough data he accepted it bore. He was on, you
49:17 , he was on the train and was the first one of the first
49:21 to suggest this idea that that the know that there are these continental cycles
49:29 you know the continental fragments crustal you , they collide and produce these big
49:37 continents, then they break up and was called the Wilson cycle. And
49:45 there's a group of folks that they like that, that moniker they want
49:50 call it super kind of site. not really have a dog in that
49:54 . I mean some of those they claim that Wilson wasn't really talking
49:58 supercontinent cycles. He was talking about the central atlantic. That's actually not
50:03 if you read his papers. But , it doesn't matter. I call
50:08 super kind of cycles mostly because it's descriptive of the process. Okay.
50:15 we'll talk to the cycles sometimes. will use them interchangeably sometimes, but
50:19 really I think of them super kind cycle is probably more precise. So
50:24 there's the opening phase and the closing . Right? So the opening is
50:29 you have riffs and passive marks, ocean basins, which is what we're
50:33 to talk about this afternoon. And next saturday we're gonna talk about convergent
50:40 , which is the closing phase. that's kind of like how it
50:44 And this and this little circle here the same thing. You have
50:48 you know, you have a right? You have a collision and
50:52 um you know, it's kind of , it's smoothed over, it's eroded
50:57 it's just quote stable creatine and you rifting and it produces these passive
51:03 you have an ocean basin. And one of these ocean basins might start
51:08 get consumed by some plate reorganization. then as those as this ocean
51:16 you know, it gets smaller and , you have another inclusion but being
51:21 cycle starts over. So that's the . Um Right more more more pictures
51:28 the internet they showed. But these really nice pictures. So that's why
51:33 don't even know if this this website active anymore. But yeah, stable
51:41 , rift, rift, rift, margin ocean basin basin gets consumed.
51:48 here in this case there's an arc collides first. So this would be
51:51 an island arcs ocean basin, their basin there. And this is an
51:56 arctic that collides does collide. it does, I guess. But
52:02 then then Then you have a continent collision. So in this case
52:07 have two little slabs down here, beneath the created arc, the one
52:14 beneath the the created continental fragment So that's the idea. And then
52:21 we can zoom in on that last . You can see this is my
52:25 . It's a really complicated because it's a melange of, you know,
52:31 that are, you know, four years old. Now, what's regard
52:38 that dating? The oldest, So there's four eons through geologic time,
52:45 oldest ones Haiti in and then K. And then produce work and
52:49 the present day one fan fan goes , you know, to the beginning
52:54 the Cambrian time, Which is 5:35 30 to the present day.
53:00 M. A. Protozoa Eon includes neo protozoa era. Okay, santa's
53:09 is an error is an error. an error. The protozoa eon includes
53:15 new protozoa era. The meso protozoa and the patio protozoa error And it
53:23 from 5:30 to M. A. to 2 1/2 digging. So it's
53:32 two billion. The protozoa Ian is times the, the tenure or the
53:41 span for fans of IAN and the Goes from 2500 million years,
53:50 4 billion gigi years. So that's little bit shorter than protozoa by half
53:57 billion years. And then The boundary Haiti in and arche in that moves
54:05 a little bit. It used to 3.85. Now it's four. And
54:10 moves it around is is the rocks the only evidence of rocks we have
54:17 Haiti in time, we are allowed have in Haiti time are just
54:23 you know uh that they find in rocks. Zircons if you don't
54:29 are just this really indestructible mineral That can find that lasts forever. And
54:37 and it can be imprinted, you with its you know, whatever its
54:44 going back into, I don't I think they found some archives that
54:49 like 4.4 which is really remarkable, in any case They see 3.85 were
55:00 oldest rocks they found, I rocks not just minerals and those were
55:06 Greenland, I believe, maybe in Canada. But then, uh but
55:13 the had Ian, but then they some rocks that were four billion.
55:18 then they moved to Haiti in boundary four because that's the age of the
55:23 rocks. That's the idea. So in goes from four billion to
55:28 44.5. So in any case the crush, it's just Milan's just sort
55:35 complicated uh crust that's floating around that bits of crust going back to four
55:43 years old. So it's very And here's here's here's a map that
55:50 created by paul, Hoffman, another Canadian geologist for north America. And
55:59 has our key and rocks in All these Wyoming superior slave ray Harn
56:05 the trans Hudson or genic belt through , uh toss them. These are
56:11 our key and rocks and then all here are a bunch of proto resort
56:18 terrain, the Iava pie. The called granite rye lights in here at
56:23 Grenville. And these these are all rocks juvenile in the in the world
56:32 this stuff. Um juvenile litmus juvenile crust is crust that was created
56:40 mantle plumes like large in these provinces crust that was or island arcs in
56:49 words that were produced over ocean ocean . So in other words, juvenile
56:57 doesn't have any, is not so to speak, by any continental
57:04 . So in other words, you're gonna find juvenile crossed with our key
57:08 rocks in because well, you might might maybe parts of the charleston,
57:15 in any case it's a compositional thing it means that there there aren't any
57:21 rocks in there. It's all But now all of these protozoa trains
57:28 intruded by tons and tons and lots lots of granite. But you can
57:33 granted this is going back to your geology days, but you can get
57:38 out of a mythic melt. Bowen's steers, right? So that's how
57:43 works. But this is really complicated . And it's really I mean,
57:47 just really interesting to me this So here's a geologic map of Canada
57:54 it shows the trans Hudson or tho Hudson and it shows, you
58:01 superior crate in the slave, what just looking at. And I can't
58:06 can't get this thing, I can't out what its coordinate system is because
58:10 wanted to stretch it on top of data. I can't do it.
58:13 can't make it look very good. we just have to let eyeball in
58:17 . But here's here is um gravity . Tell me what kind of gravity
58:25 this is. Is it free Is it bouquet. But wait,
58:32 says it right down here, I'm , I should take that up before
58:35 ask a question anyways, is there anomalies. Okay, let me ask
58:40 this thing if these are, How I know that? I mean,
58:44 know just by looking at it, what tells me that these are ones
58:51 did this yesterday isn't it was like topography you're saying because it looks like
59:00 , not a lot of topography going . No that's not it. Got
59:06 backwards. Free air is dominated by . Right, because topography is the
59:13 density contrast. That's the second biggest contrast bingo. Well done. So
59:22 at this, you have ocean floor in the labrador sea and you have
59:26 Canadian rockies and you know, going into the U. S. Rockies
59:32 here. So these are mountains which going to be routed in the upper
59:38 . There's some Appalachians over here and this is where there's an ocean
59:42 The mantle is coming up and up here into baffin bay. So what's
59:51 , you have the mojo, the is thin here. Across the stick
59:56 , cross the sticker here. So map is dominated by the base of
60:02 crust. You can see it's just the crust is thinner. You
60:08 the long wavelength component of anomalies boogie is a proxy for crustal thickness you
60:20 that? Yes. Okay, So let's let's look here, we
60:30 certainly see some of the features on . Right. We can certainly see
60:36 of these features. Uh these train in here. But this kind of
60:41 by this by this we need to a residual of that. So here's
60:46 20 km over continuation of the blue . And now we're a lot of
60:52 are really much better defined. Lots nice features in here. Uh anomalies
61:01 are probably tracking little terrain boundaries. are probably structural. Some are,
61:07 might not be the only way you do that. How would you figure
61:10 out? How would you figure out something in here was these anomalies were
61:14 by structure or compositional change? What you do? What would you would
61:24 your approach to try to sort that ? Um it would strengthen his compositional
61:37 has something to do with the anomalies . Um What you would do is
61:45 would model it up, you would your control any control, you have
61:51 , you have reflection data or refraction or well controlled or outcrop data.
61:57 someone, you know, maybe there's in the literature with some maps and
62:01 some, you know, some geologic section or whatever. You get all
62:05 stuff together in a big pile and sort through that and then you would
62:10 some models to test some of those and you would think and you
62:14 you know, you would be able sort out what you think are
62:20 which you think are compositional and those you don't know right? You also
62:24 the control, you don't have you know um But that's what you
62:29 do. You would you would model up, you could you and then
62:33 those models you might make a couple cross sections, then you might look
62:37 a map, you might make some of it, some residuals, some
62:41 or whatever. And you might try connect features from one cross section together
62:47 . And you would begin to sort develop a story or or your own
62:55 of how the thing what what all distributions of uh compositional changes the distribution
63:03 structures. And then once you do then you can start to infer the
63:09 , How did this thing happen? you know, how did it
63:12 What's what's going on here? So mean you might you're gonna have walking
63:17 it, you're going to have an like right over here it's a Western
63:19 basin. So you know, it's four land basin. So you know
63:23 you know the sort of the processes underpin that that basic formation and then
63:30 like I said you collect some control and whatever, you can if you
63:36 none, you have none. You still make a model but it's just
63:38 as well defined, but you can make a model, you can still
63:41 some some influences from that. so alright now here's the mag and
63:49 mag again look, it looks like twice as many anomalies because there is
63:55 is total field. It's not residual don't like to really residual eyes magnetic
64:00 but sometimes it's useful. So here's here's the Canadian rockies. Look at
64:07 short wavelength anomalies and look at how magnetic anomalies here sort of get broader
64:13 you go into there. So it's into the basin. Here's some sea
64:17 spreading anomalies over the labrador sea. you can definitely see a bunch of
64:24 boundaries in here. Remember remember I you that pitfall about in the gulf
64:30 Mexico where where we looked at and saw that uh you know that big
64:38 up food manic anomalies couldn't be structured they would just have throws. It
64:43 be unreasonable. Same thing here, got really high aptitude magnetic anomalies and
64:52 must be compositional. So these are related to all sorts of terrain not
64:58 on this map but also in other . But look at it like this
65:02 feature right here. This purple It's right here. It's just blue
65:07 blue just means what it just It's reverse lee polarized doesn't mean it's
65:12 low and then you have this that's slave Cragin. It's right there.
65:17 mean that's like bang, it's easy see that, you know, and
65:23 this wraps around the superior crate You can see how all these shapes
65:28 . So you see this shape for . That's that's this shape right in
65:35 . You see that? I wish could have I can't figure I want
65:42 cotton picking projection of that map I like it but I might have
65:48 do something else. Okay so let's down further south and in uh whatever
66:00 is Georgia and um most mostly Georgia Alabama as well. And into this
66:14 is the this is terrain this is we're part of the Appalachian collision.
66:20 ? So there's the piedmont here and there's the pine mountain that's where there's
66:25 basement. So that's um uh pretty studied area. And then of course
66:31 is the tough terrain. And then fault here called the liga liga fault
66:39 goes through here. Well we could can stretch that map over some uh
66:48 anomalies in particular. Our old friend tilt derivative. Remember this is kind
66:53 like an A. G. Everything's got the same amplitude and you
66:57 see how uh these terrain boundaries actually up pretty nice. There's a lot
67:03 things going on in here and in looking at this this derivative, this
67:12 is really rich. I mean it's so much detail and the pine mountain
67:17 see it's just low just sits down . I don't know. Um
67:27 Anyways yeah maybe it's this little sliver here but it certainly looks like there's
67:36 offset that looks the same or it similar to it. This is the
67:43 terrain. All of this is, any case this is kind of a
67:49 , a fun exercise, a fun of looking at these anomalies and how
67:54 can map terrain with them. so um let's just go back in
68:02 . We'll start with Pangea. So reconstruct that and here's kind of a
68:07 of it Madagascar and the Seychelles. go right in here and here's the
68:13 history. So north America was the to break up right here and it
68:20 the camp plume. There was a plume called Camp central atlantic magmatic
68:26 We don't really know where it I think the Bahamas are sitting on
68:31 of it, but that was the one and then it was shortly followed
68:35 um uh karoo which erupted down here south africa and that and that led
68:43 the break up of eastern Gondwana. eastern Gondwana is India Antarctica and Australia
68:51 Seychelles. This bit here, that's Gondwana. Western Gondwana is just africa
68:56 south America. So north America broke 1st 1 80 then eastern, then
69:04 Gondwana here broke it 1 70 then broke away from eastern Gondwana and it
69:14 sort of like left behind at 1 almost at the same time. South
69:19 began to break up. In fact already eruptions at about 1 35 of
69:25 da cunha which produced big flood basalt south America and africa right here and
69:33 about 100 million years and 100 million . M. A. Um Australia
69:39 apart from eastern from from eastern Then at 80 India and Seychelles broke
69:53 from Antarctica and jetted up, jetted to the north. Seychelles filed 20
70:00 years after that and then Greenland, broke apart and produced the Labrador Sea
70:06 53 and At 30 Arabia's. So don't have the North Atlantic in
70:15 I think the North Atlantic has got be. I should know that.
70:20 think it's I think it's in here or 100 I think I should know
70:30 . Oh wait a second. There's M. S. Up there.
70:36 yeah I should look at it. gonna make a note, make a
70:41 . Um Let's see one. I'll figure that out. I'll let
71:10 go. All right. Um Well can go back to Rhodesia Rhodesia was
71:20 supercontinent that uh preceded Lorenza. I that preceded. Okay and um so
71:34 see where this is early to right so this is rodeo nia here
71:41 you can see this is where chile chile was, right, this is
71:44 this is Hudson bay India. I south America was right here because this
71:51 western Gondwana and red eastern Gondwana and kind of turquoise color or just light
71:59 color and then Baltika which is europe was was right here. So don't
72:09 attention to this yellow thing. That's don't think that's right. And then
72:12 can go back a little bit further you can see how. Okay so
72:16 the la plata Amazonia Sao Francisco, cretins. These are all the Kalahari
72:24 , those are all right here and kind of outline south America but this
72:28 going back just before the collision to um claudia and the Siberia is over
72:36 is Siberia creighton. So this is back and just ignore that yellow
72:44 This is going back to early to neo proto resort and this is the
72:49 , this is right just before the time. And yeah I mean these
72:55 the the Oklahoma blockage and let me here do I have a map of
73:00 , I'll go back, let me go back here. So the Oklahoma
73:05 in sits right here and the Mississippi basement or real foot rift. It's
73:15 to the rough creek grabbing and then Rome trough. I'll sit here and
73:21 are all those are all Cambrian um are all Cambrian riffs. So right
73:31 the right after here these all these occurred in north America that we we
73:37 pretty, we really have a good so that the supercontinent that preceded Rhodesia
73:45 called nuna also called Columbia. It's also called other names as well.
73:51 and of course as you go back time, these things are less well
73:56 . And the, the folks that and worry about these things, you
73:59 , the debates are furious. Supercontinent Has really not been accepted until the
74:09 . So just 20 years ago. it's stuff we're still learning about.
74:14 really fascinating stuff. Um, but , here you have, let's
74:20 Let's see if we can find something looks familiar. So this says West
74:24 . It's Amazonia. Remember, here's superior crate town. So this
74:31 , this is Hudson Bay, right . That's superior. Here's Wyoming.
74:36 ends up ends up down here. our Iava pie. Oh,
74:40 never mind. This is correct. is on its side. So here's
74:44 Superior. There's the trans Hudson. ? So this is on its
74:48 you have a pie. My cell . Right? These were already already
74:54 to each other at this at this . So yeah. Um,
75:08 let me just, yeah. and then, um, This is
75:16 this is 1270. So that's It 1270. That's, that's still
75:26 I think it's still, I think still neo protozoa because I think it
75:31 back to 1600 I think. Got , hold on, let me look
75:50 . Oh, New Products are Yeah. Near Protocol goes back to
76:09 missile. Missile goes to 1600. this is in the medical protocol.
76:16 protest. Okay. So how do things, what's how does this
76:22 How does this stuff work? here's a nice table by Bradley or
76:26 nice chart rather. And it shows the super kind of, so even
76:31 luna or Columbia, depending on what like. There's also some people have
76:38 supercontinent called slavia or superior also uh . And um you know, and
76:46 here's the beginning of plate tectonics. what Bradley did he just correlated using
76:54 to try those zircons? He you know, their abundance as a
77:02 of time here. And you can there's peaks between the supercontinent. That
77:07 of makes sense because if it when broken apart, you're just gonna have
77:11 erosion. You're gonna have more passive because when they're all together there's
77:16 you know, you know, less for erosion. So yeah, so
77:21 have peaks between them due to more . And then you also have correlations
77:30 gran, it's as well as um are lower crustal, in other
77:35 there's there's more exposed lower crust because been drifted, right? There's a
77:42 of rifting going up. But what's idea? How does this stuff
77:47 Let me see what I got Yeah. What what they think.
77:52 not gonna test you on this. , I'll just tell you though what
77:55 think is that when the when the coalesce that super kinda it forms a
78:02 lid. Right. And then it heats up the mantle beneath it and
78:09 the mantle heats up beneath it. and and also the there's plates,
78:15 know, there's ocean oceanic plates abducting around it, right? So it's
78:21 it's a thermal lid but also there's pile of subduction of slabs beneath
78:29 And they use words like slab avalanche those slabs collect at the base of
78:35 of the mantle, you know, the top of the outer core.
78:40 they call that a slab graveyard. so so that they think that material
78:48 the fuel, it gets heated because the lid and it's the fuel that
78:54 a bunch of man up close, close if you will. And they
79:00 that those come up and those are break up the continents and then when
79:04 contents are all broken apart and everything's around, well everything cools down and
79:11 makes these, you know, and means that these fragments are going to
79:16 and crash into each other again and another supercontinent, which forms another mental
79:22 so that's the cycle. That's the what people say is the mechanism of
79:26 cycle, which is really very Okay. Any questions about plate tectonics
79:34 supercontinent cycles? Um No, I think so. Not yet.
79:47 so I've been Yeah, Marianne for an hour, why don't we take
79:51 little break and then reconvene um in 10 minutes or so something like
79:58 Okay. And I guess that means tell us here as well as
80:07 Okay, so no questions about plate or supercontinent cycles. You got that
80:13 ? 100%. I actually do have question. Right? Um So if
80:19 could go back to slide like 29 area um it made sense to me
80:28 other day, but for some reason I don't understand it today. Can
80:32 explain what you mean by like how can tell whether or not it's a
80:35 wavelength versus like a short wavelength because for me in my head it automatically
80:41 to like a crest and trough So I'm like having a problem like
80:46 that to like what I'm looking at far as like wavelengths are concerned.
80:50 that makes sense. Sure. okay, let's just look at this
80:56 bouquet in alleys. These these things tracing here, these are shorter wavelength
81:02 this broad low here. Right? . So that broad mold is a
81:10 . I mean if you can imagine profile across here, you got to
81:13 going from the high down to a and then back up again.
81:19 So that is a broad wavelength This is a broadway. This high
81:25 here, you can imagine a profile through here. It would go from
81:28 low to a high, right? when I say this broadway you're going
81:35 a high and then there's a low and then there's kind of a middle
81:41 , then a low here and then low here. These are these broad
81:45 of highs and lows are broad Just kind of envision a cross section
81:52 here profile that goes transect. This that make sense? So then when
82:00 check out those long wavelengths, all features they're here, they're just superimposed
82:08 top of this broad high and low . Which are just swamping the data
82:12 . So once we take out this low, just broad wavelength field,
82:18 flattens the data. As we basically all these features are on that
82:24 , they're just superimposed on that high low. Uh that broad wavelength
82:30 Does that make sense? Mhm. here has the long wavelength. Once
82:37 remove those, we end up, I said, we say flattening the
82:43 , you can flatten And even more you want to find five comin up
82:47 continuation, you wouldn't see like this through here. I mean it would
82:53 make it look, you know, would make it look like this mag
82:56 Almost just almost, you know, a bunch of short wavelengths on a
83:01 know. Okay, does that help doesn't help? So in a
83:08 So the colors are basically just referencing where the wavelengths are like hitting on
83:14 spectrum. Pretty much. Yeah. . Because I guess in my head
83:21 what I picture when you say like wavelength is like I'm actually picturing like
83:25 really long like wave, you just like a big old hump.
83:30 I'm just like I'm trying to break from that if that makes sense.
83:34 it makes sense. So I mean I I am very purposeful about the
83:41 I talk about these data because a of potential field, they always they
83:47 low, they say low frequency, ? Or high frequency, say what's
83:54 these features here. These are high analysis. This is a low frequency
84:00 I I prefer wavelength because these are data. They're not they're not a
84:06 series. They're not acquired in the domain. Right? So their spatial
84:13 , seismic data is is temporal It's a time series. Right?
84:21 I mean you can transform spatial anomalies the frequency domain of course and then
84:29 appropriate to talk about frequencies, but think it's I think too often and
84:37 , you know, you'll hear people high frequency now and they're not high
84:41 anomalies. There's short wavelength anomalous because not looking at a time series.
84:46 looking at a map in X and or lat and long. And so
84:54 that's what's throwing you off mike when keep calling it long wavelength. So
85:00 talking about spatial data. Not frequency . So. So what was
85:06 I showed that profile back here. was that at? What we should
85:11 at these? Look at this, mean this is look at this MAG
85:15 for example this MAG data has long components. There's a broad high
85:21 There's a broad load here. Another high down here. The broad low
85:26 here. Now superimposed on those broad and lows are shorter wavelength anomalies,
85:33 . Some very very short wave. mean super short wavelength anomalies in
85:39 And even like these linear features Right. But there's a there is
85:44 this map you can see that there broad highs and lows and then there
85:48 soups superimposed on those shorter wavelength Do you see that? Yes.
85:54 . Yeah, it's making it you're clarifying it very well.
85:58 So if you were to take a like going through here, you would
86:02 a broad high and abroad low. then you'd have all these other features
86:06 on top of that, on top that profile. So it would
86:11 so your your lobe your you go low to high to low. There's
86:16 there's your sort of gauzy in, know, your minimum curvature. I
86:20 you're not curvature, you're zero Phase . Right? It would be this
86:27 to high to low. Does that sense? And then and then maybe
86:36 that you know then anyways. So that's what I'm talking about that
86:41 have these broad wavelengths which are this I'm showing you here? Broad high
86:46 then superimposed on that you have these amounts and that's a really important
86:53 I'm really glad you asked me because is something that you really need to
86:57 when you look at these maps. remember as I said, long wavelengths
87:02 deep sources. Short wavelengths are shallow . Just like all geophysics or low
87:08 are deep sources. Because you don't seismic data is because the energy,
87:15 know, the high frequency energy is in the shallow part of the of
87:19 section. And then you just left like 30 hertz or longer or
87:25 But in this case its wavelengths and like this. So you have a
87:32 low high low you have all these broad undulations that are that are beneath
87:38 . Now you could make a you could do it in the frequency
87:41 , you could do a continuation and can flatten all this and all this
87:45 frequency stuff will just pop out because could you could take out all these
87:51 , high and low undulations in this . Can you visualize that?
87:58 good, good. Good. Good . That's really important to sort of
88:03 your head around um looking at magnetic maps is looking at it in terms
88:08 wavelength and um uh you know getting sort of a sense of where these
88:20 are sourced from, how deep they're from. So did you have any
88:25 questions about that material? No, was the only one that I was
88:30 , I don't really. Okay, . So. Alright, alright.
88:36 let's talk about basic classification And I'm start off with this. This figure
88:43 like this figures from Nyberg and Howl . And this is like um this
88:49 this is a Robinson projection by the . And it's just showing the spatial
88:56 of sedimentary basins by structural regime with charts to demonstrate based and surface area
89:04 of terrestrial here. This is just based basins. And then over here
89:10 the right, it's continental list is . So that includes marine areas,
89:16 where the continental crust is just beneath . That is passive marriages. Um
89:24 . So if we look at terrestrial , uplands, that just means there's
89:31 basin and I guess that's all these areas. No, it can't
89:38 Maybe it is. See I think missing a lot of bases here.
89:45 , in inter crew tonic, it's gold color. But there's michigan basin
89:52 Williston. There's Illinois. You there's a parent that's not, it's
89:57 parent, but the parent. So rift basin extension? Read? They
90:03 have this, they don't have the Siberia basin. So this is this
90:08 this is a good effort, but incomplete. I would say it would
90:11 my, my honest opinion. But say that the terrestrial basins, our
90:22 You know, uh make up 16% the land area and dividing that
90:30 Um Almost half of that are interpret and that's all these gold areas.
90:39 now they're using inter catatonic kind of . Well, they talk about,
90:45 know, I don't understand this, know, I think some of their
90:48 anyways, we'll just go with what got here. I think I think
90:51 would take issue with a lot of classes for land because of the western
90:55 bases of four land is a bunch four land bases here. These are
90:59 lands. So they've got those signified . But yeah, I think there's
91:07 things that are incorrect. These guys be from europe or something like
91:11 But yeah, and then the red extension allow rift basins and the purple
91:19 strike slip. So like trans intentional professional basins. So that's the distribution
91:26 basins according to neighbor and how and regard to continental atmosphere. Now,
91:35 have to include passive margins which are these bright yellow areas and those make
91:41 46% um basins um On the And of course of all bases
91:51 you know, whatever what continental, ocean basin. And once you include
91:56 viruses, you go from 16% to of the continental territory, the continental
92:03 the sphere. And um titanic sinks . Uh it's now 18 4 lands
92:11 10 back arcs are. Yeah, mean that's a really loose. I
92:18 think of these back arc basins at here. So, yeah, maybe
92:23 gonna change my my preference for this in any case they say this
92:30 Um It's interesting to think about this . Um It to be, to
92:39 honest, you could probably ask 10 that think about these things. Um
92:46 you would get maybe, you 15 answers. So. So
92:55 moron, you moron. Basic So, here's a really good paper
93:02 Alain at all in this um in journal. The citation is the
93:11 Well, the references included in the . And this is a kind of
93:15 summary of of Dickinson Reading and Well, Kingston and all this was
93:25 group from Exxon and how they classify basins. So, Dickinson, um
93:35 know, they they they they decide the substrate, is it oceanic or
93:42 ? Or they use this word I don't like that word in talking
93:46 crust, but you see it a . Usually what they mean when people
93:52 transitional, what they usually mean is it's it's thin the continental crust and
93:59 transitional part is just thickness from continent ocean. That's what they typically mean
94:05 that. And Dickinson then. Uh think he just passed away a year
94:12 two ago. But they also talked within proximity to the plate margin,
94:17 it interior or is it uh Or it? You know, along near
94:22 plate margin? And what kind of boundary is it divergent covers that are
94:28 . Now, reading did something quite . Ocean basins, rifting margins,
94:34 continental margins are trench suture belts. would be where two continents collided.
94:42 . This would be the interior basis strike slip. So you can see
94:47 is a transform boundary. This fits two kind of are related to the
94:55 . Um And these could be type if you wanted to sort of,
95:02 know, kind of connect the dots these. And then Kingston and other
95:08 two papers in 83. And they actually devised a special nomenclature for all
95:17 things, but they have, what they have? 1235. Is there
95:22 here? And there's nine here. was continental and oceanic. Right?
95:29 they're dividing it by sub strata and they're talking about interior. So there's
95:36 interior parts interior fresher. That's a continental margins side, that's an internal
95:44 , March. So that's what like , that would be, where would
95:49 be continental. It would be inter would be this one for that.
95:54 up to rent. So that's that's strike slip early. That would be
95:58 long and transform and or transfer sometimes say. And then Trent. So
96:04 is a this is um an ocean uh uh plate margin basis. And
96:14 ocean basis. Right, So oceanic , continental, trans ocean trans oceanic
96:22 continental wrench oceanic fractures. Oceanic So um Creighton ization is a really
96:32 word. Um but base informing deposition sequences and basin modifying. So
96:40 are important concepts to think about when thinking about basins and how they
96:46 And we also, you also have think of them in the context of
96:49 tectonics, which also what makes you about supercontinent cycles and how all that
96:55 fits together. So the idea is the basins, you know, they
97:00 form in response to plate motions and that stuff. And um of course
97:07 and lots of other things. So a lot of things to consider.
97:14 now this is their review of Bali Snelson, which was an important
97:18 I think it's 1980s 1988. And Nelson divided bases into three main
97:26 They called rigid with a stable atmosphere with sphere outside of a contractual mega
97:34 , which means parachutes, jewel and megacities, which is episode. So
97:39 look at these. So the first , uh there's two types within two
97:47 , those related to the formation of crust and those related on pre Mesozoic
97:54 literacy basically they're talking about paleozoic crustal and they're saying that most crustal stags
98:00 paleozoic. It's actually not necessarily That is absolutely, it's absolutely factually
98:09 . So um yeah. Okay. the other one is, let me
98:18 write riffs, oceanic transform falls oceanic so atlantic type passive margins. So
98:29 is this is they're saying it's stable it's and that's related to the word
98:37 , passive margins are passive because there's plate boundary there. It's just the
98:43 is as it says here, it's it's the boundary between oceanic and continental
98:49 which is not a plate boundary. just a change in the composition of
98:53 crust. That's where the oceanic crust indeed a created at the spreading center
99:02 the divergent margin. But the butt axis as the ocean floor, you
99:08 as the ocean basin opens up and that boundary between the continent, the
99:14 , it's no longer a plate boundary I was describing earlier when I when
99:20 were looking at those global maps of , magnetic gravity data and the and
99:26 tectonic plate data. So so So um yeah I guess in that
99:34 it's stable and and even rigid. now the second one rigid with a
99:40 outside. So deep sea trenches, deep uh kind of okay uh rab
99:50 , this is a weird character but just talking about the oceanic trenches so
99:56 subduction zones, four deeps forties buried grab and no blocks dominate but
100:05 type. Uh I'm not exactly Let's talk about this man. I
100:11 work it out from Benny a social for art. So this is like
100:17 continent subduction. We have four. , all the circum pacific on the
100:24 the western margin along the pacific, all those back art ocean basins like
100:29 in board of Japan is the sea japan. That's a back arc
100:35 And there's a whole bunch of those of basins along that margin. So
100:43 backyard basis, the continental collision, , Western care, a western.
100:49 ? So so the when africa collided now Africa is moving north into europe
101:00 it's closing what was once the ocean the only remainder is the mediterranean.
101:08 that's episode Natural. Oh I So these are basin margin basis related
101:17 absolutely great. Right. X. , okay. Now I know what
101:22 are. So episodes are these are are located near plate boundaries, near
101:28 margins. So in the case of ocean continent, they're like little back
101:33 in between continent continent collisions. It's africa colliding with europe and the caucuses
101:42 the Alpine's um that sort of defamation um even extension. All the great
101:50 California stuff. That's all related to subduction. So that's what that's
101:55 So these must be intra inter So deep sea trench. Oh on
102:04 floor. Okay. Yeah this is weird stuff. Anyways, let's just
102:09 on. So here is a review Pinkston. This is the Exxon group
102:15 this is a very nice chart. a remake. I'm going to show
102:18 the original one. It's okay so go type of substrate, then you
102:22 continent, ocean and then when you to then it's divided by type of
102:26 , type of motion diversion, trance conversion, same thing. And then
102:32 relative to the plate boundary is an , external interior or external and there
102:37 hope interior margin, interior margin. . And then you can break it
102:41 different kinds of basis, Protonix failed rift, continental rift and then
102:46 all these little kinds of basins in . But it all sort of makes
102:51 . And you divide it by the of crust. Then you divide it
102:54 the kind of boundary and then you you put where its position is with
103:01 to that boundary. Okay now ingersoll Busby have a really nice book called
103:10 called sedimentary plate tectonics and sedimentary basins something like that. But then there's
103:17 actually give a lot of examples of examples of modern examples, which is
103:22 cool. Alright. So they have diversion settings to inter plate settings,
103:27 convergence settings. And they have some , you know, abc and they
103:33 that down and they have examples. what they think he might disagree but
103:38 matter, I mean which is But this is what they think.
103:42 they have modern day examples and you ancient, you know fossil basins if
103:47 like. Um And that goes There's 1/4 transform settings and hybrid.
103:54 is similar to what I'm talking about I say complex settings. Right?
103:58 again, so this is really kind fun. You can examine these and
104:04 a have a have a look at . We might bounce back here after
104:08 down here a little further. Um they made this little chart which is
104:13 interesting. So along the left they it into our favorite divergent basis related
104:22 divergent plate motion, basically the convergent motion and then transverse, right.
104:28 current plate motion. And here's all basic types continental rift, oceanic rift
104:33 ridge proto oceanic down here, oceanic for our backyard. Um Trans intentional
104:41 trans rotational. Very nice. now then what they've done is they've
104:46 all of these according to how they're the mechanism the dominant important and
104:54 So crustal thinning, is that Little spherical uh mantle uh thickening,
105:02 sentiment, ology, sedimentation, century loading tectonic, super crustal loading,
105:10 crustal loading in face stress. And and then of course the color color
105:15 . So there you have it. that's amazing. I mean it's
105:19 And then and then if you look , they have um their their generic
105:27 for classification. So they have mantle . Uh dynamic topography. Now they're
105:35 a little bit of geodynamic. So atmosphere stretching and cooling and with a
105:41 if lecture. Alright, so think that. This is like atmosphere temperature
105:48 thinning and thickening versus structure bending. . And then so there's those that
105:55 on continental atmosphere and those that are oceanic atmosphere. And here you have
106:00 these same sort of basins that we are in the other classification systems.
106:06 I guess you could make a master of some kind of weird four dimensional
106:13 then diagram sort of thing to figure where all these things, but I
106:19 know how important it is. so here we have left the sphere
106:24 and cooling again. Coming down to . Here's mantle circulation popping down here
106:29 here's flex your due to loading. , continental atmosphere, oceanic atmosphere.
106:34 there's some that are closely related. of course there are these are all
106:38 by sediment loading, uh diminishing from to bottom, here on the
106:46 So, once again, there's all labels, all these different kinds of
106:49 . You can kind of like what say, connect the dots between
106:53 I think there's one more even more diagram, but it's really fascinating.
107:00 , this is actually two diagrams and there's this one here on the
107:04 the box, but let's look at one on the right, which which
107:08 which kind of surrounds it. from the top, it's it's the
107:13 cycle. So this is a nominal span of supercontinent cycle. They have
107:18 million years. That's pretty good. mean, I would say whatever,
107:24 to 600 million years would be like nominal supercontinent cycle. So they're saying
107:30 time zero of the cycle coming up like I guess 1 70 something like
107:35 , we have a continental rift proto . And then, and then you
107:41 an ocean basin form here, passive where these failed rift now failed rift
107:47 means the rift form, but it produce an ocean basin. Okay.
107:52 then you have intercourse tonic basins which ever, which are remember these are
107:59 claim that they are not Related to tectonics and by their duration here,
108:06 at this, it goes 200 million . And uh I can tell you
108:11 there's a cra tonic sag in India lived it collected sediments from 7800 million
108:19 ago to 700 million years ago. other words, in the mid protozoa
108:26 too. Late Kallio, late It collected sediments for a billion
108:37 So yeah, they they just they not connected to the super kind of
108:44 . And then the length of the of passive margins and then uh have
108:51 . These are sticking out here. , I guess at the end of
108:54 , you have these continental strike slip , I guess ocean basic kind of
108:58 and down here, you have arc oceanic crust. So those form towards
109:03 end when you're braking when um you , you're you're creating the last bits
109:09 the last fragments of art train, guess, to the edge of the
109:15 of the super of the supercontinent. those produced these kinds of bases
109:21 So from the bottom, you can inter inter uh incubation, continental inflation
109:28 , starts to grow in the Then there's rifting and breakup. And
109:32 is how it breaks apart subduction and . So that's a supercontinent cycle.
109:40 you can see the platonic basis lives all this stuff. So, on
109:44 right again, our time span now from, I guess it's a log
109:50 in time from .1 to 1000 million , a billion years. And you
109:56 see, so they have platonic just . It lasts from You know,
110:02 saying from whatever, 300 million to whatever, 600 million, I guess
110:07 , I guess. Where would it's log anyways. Um the rift basins
110:12 live as long passive margins and ocean have about the same. These are
110:17 to the cycle. And that's for for conversion, uh trenches Live maybe
110:27 million years trench slow, you up to 10 million for our inter
110:33 . You can see how long these live. And then, so these
110:37 sort of their idea. So, is a lot of work, I
110:40 , you know, there's a lot stuff going on here. Here's here's
110:45 original chart. Again, these are guys from Exxon. And so they
110:49 some identification parameters. There's a kind oceanic the tide. Right? And
110:55 over here the type of past plate . So they're trying to trying to
111:00 , you know, some historical uh into it. Right. And then
111:06 a basin cycle. Okay, so again continent ocean basins completely formed on
111:14 across basically continental. And then you is it uh is it divergent or
111:21 the same thing? Um And then margin. Interior margin. So this
111:26 all summarized by Alan and Alan. then this is where Alan stops with
111:30 these different names and everything. But here's what Kingston also did. They
111:37 to these theoretical model basin types. then they just come up this
111:43 So I. S. Is an crustal sag I. F. Interior
111:47 , MSs margin sag cet et Right. So they come up this
111:53 normal because they're going to build a and it's also based on the
111:59 So they're talking about um transgression So you have their basic three stage
112:07 from transgression regression. Transgression. So if it's if it's a sag it's
112:15 internal sag. Yes for example I is an interior it's a continental
112:20 Platonic basin. You could have you a would be I. A.
112:26 would be I. S. It's a regression to regression. And
112:32 be this part here would be S. 3 to 1. And
112:37 it would be I. S. . Right. And then if it's
112:41 . And then if you're on the on that it's tilted as nonconformity.
112:45 might have something like that. Okay this this stage formulation is combined with
112:53 nomenclature uh into like something like this like uh through the gulf of Mexico
113:01 you have, you know, you to enter your fractures, you've solved
113:06 your sag. And then MSC margin margins because it's an ocean margin after
113:11 ocean after the gulf of Mexico opens . So it's a rift then of
113:15 a sag. And right okay and kind of basin is called. And
113:21 . S. Dash 22 1 dash . C. Dash. I mean
113:26 S. Dash 321 slash L. . Slash I. S. Dash
113:30 slash I. F. Dash And everybody knows what kind of a
113:35 that is. You're starting to get hint for like contempt for these sort
113:42 things. I mean it's just like got way too much time on your
113:46 . Um Not to be outdone the sick. This woman, her name
113:52 Miller on this problem and she decided do some Ai work. This is
113:57 1993. So this is really early of artificial intelligence and of course you
114:04 you have the same thing, you a knowledge base and you and you
114:07 your data into the training set and control set. I mean the training
114:13 and the testing set and you have ways to tone that and you know
114:19 whatever. You have your knowledge database you generate you generate that and you
114:25 into some this is part of your , your your your own categorization and
114:30 did quite similar but she broke it strategic graffiti and tectonics. So structure
114:37 sedimentation into the basin type. So photography, you know major units,
114:45 and then deposition and unconfirmed is fed a structure the structure of the tectonic
114:53 events and then you know, localized events and then age with a logic
114:58 . And then of course basic rock and then basic structures and incline incline
115:05 that. Those are super class class and attributes. Alright, so you
115:11 all that into your into your engine it goes down here and makes a
115:16 of decisions and it finds an answer says bingo, this is it
115:21 this is the answer. So that that idea. Um And there's even
115:27 classification systems. This is nota actually him this summer last summer and He's
115:35 four art basins which are which form the edge of subduction zones.
115:41 And they're really interesting because you could uh you can have compression right where
115:50 compression but you can actually have extension what happens is if the slab,
115:54 the sub ducting slab it can become , it can be, you
115:59 it's it's in it's in the in mantle. Well, if the plates
116:07 above that, the overriding plage can pull away And that can cause extension
116:15 the four art. So he's decided there are you can have different types
116:22 the two. The two variables are amount of loading. If there's a
116:28 bunch of sentiment punching, pulling then you can have a bunch of
116:33 in a convergent or a bunch of and extension or you can have,
116:38 know, be neutral where the loading extension are sort of our sort of
116:45 . But in any case you can that. Right? So there's the
116:50 classification stuff can get pretty crazy. , so let's talk about interpretation.
116:58 here here is how I look at basin classifications stuff I think of it
117:05 terms of there are there are the elements of based in forming elements.
117:13 the forces involved. Whether it's extension are the substrate, the type of
117:19 , whether it's continental or oceanic or transition. This mobile zone. This
117:26 the zone of you know where the occurs when plates collide or plates,
117:33 know are breaking apart that sort of bondage deformation zone. It's continental
117:42 And then um is it is the just one off or is it multi
117:49 ? Is there many of them. then with these ideas, these three
117:55 in forming elements. you can say you can you can actually come up
118:00 three groups. You can say six in three groups. And you can
118:06 continental extension, continent compression. Mobile extension, mobile compression, oceanic
118:12 oceanic compression. And then you know can stack on top of that whether
118:17 single or multi faith. So Right and then trans dimensional transgression they
118:27 you can just borrow elements from these fill that in so they still fit
118:32 here. So this is the way look at that. Let me see
118:35 . Um Any questions about that. one basic classification and two. My
118:45 here what I think are the things we should really especially with regard to
118:50 Magnetics. This is the way we be looking at these things.
118:55 No questions yet. Okay okay. as I said with with regard to
119:07 magnetic data um What what what do um um What are the things that
119:18 can see with them? What do tell us? Well with magnetic data
119:24 can you can interpret basement now it be super basement elements, inter basement
119:32 and sea floor spreading anomalies. You also interpret volcanic in the sedimentary section
119:39 in some cases very shallow salt because salt is dying magnetic sentiments do have
119:46 mag magnetism. And so the contrast that can produce some subtle anomalies sometimes
119:53 but um tell me the difference between basement and intra basement. I'm assuming
120:09 is over the other. I'm actually sure. Super basement is structural a
120:19 or a black or a fault block something is up and something is down
120:26 basement is compositional. It's a rock changing rock type. It may be
120:32 , but the composition changes such that produces an anomaly. So remember that
120:39 profile I showed you uh would have last yesterday in the evening where I
120:45 you that magnetic profile over that a simple cross section where I had an
120:50 basement uh magnetic change that produced a high amplitude anomaly. And then they
120:56 the two structural things that produced a amplitude anomaly. Those two little structural
121:02 are super basement. And then one that produced a big anti anomaly that's
121:09 basement as well as the change in crystal type. On the right hand
121:15 of that model, that was inter as well. Okay, that makes
121:20 . Intra composite. Okay. Interest super. So with gravity
121:26 you can do the same thing inter versus super basement. Now, gravity
121:32 has some special things going on. are some densities and cemetery rocks that
121:36 really notable one salt as we discussed , carbonates can be pretty high density
121:42 then hydrate and hydrates are like They're very dense. And as we've
121:48 discussing very long wavelengths can be You can matt crustal crustal variations in
121:56 . Right? Because remember the blue data is dominated by the contrast at
122:01 base of the crust. So it's long gravity anomaly. Very long way
122:05 gravity anomalies can be related to crustal variations. And this is it.
122:13 is pretty much I mean there are specialized things with some specialized data but
122:18 gravity and magnetic data, these are things you can find and you can
122:21 for. So if someone says can map you know, can I map
122:27 know on lap of these classic this uh a sequence on you know on
122:36 of this other classic sequence. The is no sorry I wish I could
122:42 I can't you know. So there's are really what we use the data
122:50 Now. I'm gonna talk about this called nine uniqueness which you see all
122:55 time. Especially with regard to gravity magnetic data. First of all,
123:01 not the data that's not unique. data is just a passive measure.
123:06 can't be it can't be 198. just just a passive measures. Just
123:11 . The 19 is with regard to interpretation of gravity, magnetic data.
123:18 in fact this is true for all , even wire line data. You
123:22 , I mean you could ask five interpreters you know that spend their days
123:29 logs past each other to find, know correlating wells And you'll get,
123:35 know, 10 opinions on different different you know, resistive. Itty curves
123:42 example. But this is the classic is from Nettleton and it's the one
123:49 I really have to take issue And I and I get in an
123:53 with my colleagues. So I mean I'm sort of fighting city hall
123:57 But but this is the classic 19 says that these sources can all produce
124:05 anomaly. And that is absolutely true homogeneous sources, but that's not
124:11 I mean the world is not like , right? In reality In the
124:17 and there will be little in homage 80s in this, in this this
124:23 sheet here and those in homage in will produce short wavelength anomalies that will
124:28 superimposed on this broad feature. And those anomalies that tells you the source
124:34 shell. Likewise. Or similarly this lens We'll have in homage in 80s
124:43 that. And those in Hama genetics produce these intermediate wave economics that will
124:48 superimposed on top of this broad So so that's why I say,
124:56 know, um this this idea that which which which is it just kills
125:04 because there are people who who are about their gravity and magnetic data
125:11 And in the abstract they will well the gate is not unique.
125:14 I mean, you know, um don't you just say don't read my
125:19 because it's a waste of your Um you never see someone who interprets
125:24 data and say well our interpretation is unique. They never say that you
125:30 they state with with you know with that you know were these download these
125:36 ? Lapping sections are you know, you know, a regression in the
125:45 blah blah blah. So so You obviously I feel strongly about this but
125:51 in mind lots of people would just care about this. But to me
125:56 really unfair that this this label of Eakins gets hung around the you
126:02 hung around the necks of people who these data and they do it to
126:07 as well. It's which says something not sure any case. Alright,
126:13 now we're at the critical slide. is really important. If there's nothing
126:16 take away from all these hours that sit here talking about this stuff.
126:21 is the stuff that you should really remember. And this goes and
126:25 ties back to to this slide as . What you can what you what
126:30 can actually interpret. These are two important slides but this is really this
126:34 is very important and here's here's the you should look at these data.
126:39 with regard to gravity it is generally in other words, structural highs are
126:46 produced anomaly highs and structural lows are related to anomaly lows but remember except
126:55 very long wavelengths, except for very wavelengths, that's pretty much true with
127:02 data. Um with magnetic data, , you want to look at it
127:08 terms of wavelength, As I've been , long wavelengths are produced by deep
127:14 . Short wavelengths are produced by shallow . Now with regard to wavelength um
127:21 typically proportional to source depth. so long wave, as I
127:26 long ways, short wavelength shall um wavelengths greater than 800 kilometers in general
127:34 be related to mojo topography or basically changes in the crust. Okay,
127:44 with wavelengths less than that, you begin as a rule of thumb,
127:49 to infer that those are produced by and then of course this this relation
127:57 is something you should always remember, is about four times a source
128:02 Okay. That that you should know with regard to amplitude, so
128:09 that's that's those are produced by the in the density or the magnetic
128:15 they're produced by the rock property not structure, although they can be
128:23 to that, but they're generally related amplitude. Yeah, they are related
128:27 the rock property. So, with to gravity anomalies, If it's less
128:36 , say 50 mg. Um if if it's um I'm sorry, if
128:44 greater than 50 million gallons, it's produced by with ology by density contrast
128:51 the rocks or mobile topography. Um if it ranges from 10 to
128:59 and these are the ones we These are the ones that are produced
129:02 structure. So 10 to 50 million . You're in the range of interpreting
129:07 structures unless you know otherwise, I'm to show you an example later where
129:12 is the case where there are anomalies big but they're not structural and then
129:18 anomalies. I mean if you if date is really good and remember we
129:23 at some data that was very good those cars topography ease in in England
129:30 the Bahamas. But those are produced small structures and density contrast. Um
129:37 you need to have really good data good sampling to interpret those the same
129:41 with those small anomalies for magnetic with amplitude. Again, hundreds to thousands
129:47 nana testers. Those are gonna be a logic boundaries. This is that
129:51 I mentioned tens of nano Teslas or are produced by basement structures. So
129:58 of gammas or nana. Tesla's tens millennials. Those are the anomalies that
130:04 like, the ones we want to because those are those are helping us
130:08 structure. Okay. We like the ones too because they show us,
130:12 know, uh you know, compositional and sometimes, you know, crustal
130:17 changed, but this is the breakdown amplitude. So wavelength tells you how
130:25 amplitude tells you uh what type I . So this is uh any questions
130:34 this? Not not yet, I mean, I'll have to read
130:40 it again, but like right now seems confusing. You gotta get your
130:43 around this. This is really I mean, it really really,
130:46 is important. Um Let's see, me do this. I start to
130:53 and we'll see where we're at. I take like a three minute break
130:56 quick? Oh yeah, we'll take break. Let's take five.
131:00 I'll be right back. Hey, Alright, so let's let's talk about
131:07 a sissy and this you might remember had this slide up when we're talking
131:11 gravity processing, grabbing corrections, latitude free bouquet correction. But then I
131:20 out as a static and ecstatic And because I think it's I don't
131:29 , well I think a lot of , but I don't think it's really
131:33 nice or static correction. Let me why. Okay, of course you
131:39 are familiar with the idea that, know, the crap model where he
131:43 says the crust is uniform and it changes in density versus the area model
131:51 it says that, you know, crust is uniform density and it just
131:57 just changes um in thickness based you know, this kind of like
132:03 our communities principle of, you buoyancy, right? Um And in
132:10 they're both probably right. I mean crust is a dense is a little
132:15 more dense than continental crust, but , you know, it's pretty,
132:21 know, we all know that continents rooted etcetera etcetera. So, so
132:25 , you know, that's the there's lot of words here, but that's
132:30 just what I'm saying. This is All right now, let's look at
132:35 gulf of Mexico. Again, we at gravity data before these are boog
132:39 gravity anomalies. So they've been you know, they the correction,
132:44 know, attempts to minimize the effect um topography. Now there's there's these
132:53 in the gulf coast um that are the order of 80 to 100 kilometers
133:00 . There are also some big structures there. Right? This is the
133:03 texas basin, this is the Mississippi basin, this is the Sabine
133:09 this is the Wiggins arch. So updated RTR structural highs and the bases
133:16 of course structural loans. Right? But look at this, the east
133:22 basin produces a gravity low, which would expect. I mean that's very
133:26 . A basin produces a low but Mississippi salt basin produces big gravity high
133:33 setting up let producers gravity high, is intuitive structural anomaly. But the
133:40 arts produces this gravity law. What heck is going on here? They're
133:44 right next to each other. What's here is that the crust up here
133:53 of follow if you follow my Um a cursor, the cross north
133:58 this sort of region is thicker and stronger and it can support these
134:07 It's strong enough and thick enough to these basin and uplifted structures. But
134:14 crust down here close to the the continental margin actually, which extends
134:20 out border here, but the crust here is thinner and it can't support
134:27 structures. So these structures are compensated in other words, the arches rooted
134:39 the upper mantle. So it's its its buoyancy, it's the
134:45 And the upper mantle, the mantle up beneath the Mississippi salt basin,
134:51 is what's producing this high. The density upper mantle of 3.22 lower crust
135:00 is is really swamping the signal here up here, the cross is sticking
135:07 . So the basin is producing a loan structure needs to signing up gravity
135:15 . So, if I were to across the ice, a static anomaly
135:21 this. Okay, so in the , by the way, gently dips
135:26 the top of this From 300 m the coast. Right, and ice
135:32 static anomalies are calculated from topography A function of topography. Right?
135:39 you say that, you know, elevated topography is going to produce a
135:44 in the mantle is gonna, you , that's the idea. So you
135:48 that to its logical conclusion over all over all topographic wavelengths, then,
135:57 know, for an area as big this where it's all pretty flat.
136:03 not gonna change anything. The ice static anatomy will look a lot like
136:07 yet. This is compensated. This not a society has not been corrected
136:14 , right? This this it's not done here. That's why I think
136:21 someone does it, you don't really what you're getting because you don't know
136:27 you don't know what they're unless they you the D. E.
136:32 And they show you the regional Whenever I see, I want to
136:37 what they did what they took What was the regional component?
136:41 so that's why I'm not crazy about correction. It's just they just a
136:48 , you know, but the process do a kind of thing because I
136:52 think you're really correcting for. There too many, you know, dynamic
136:57 associated with the crust and basin formation um I think it might even,
137:08 think it's more honest to do like a continuation filter or residual than or
137:15 limited data or whatever. But this aesthetic correction. One, it's not
137:21 correction and two, you don't know the heck they did. I mean
137:24 says that The topography is gonna I mean sure we correct for topography
137:29 who says the topography is related to structures in the subsurface that you want
137:33 learn about. You know why why that data into your into your gravity
137:40 anyway. That's my soapbox about that . Okay, so we're gonna talk
137:48 crustal sags and they're separate, remember separate from supercontinent cycles. There sort
137:55 a tectonic, if you like. And They're, yeah, they're called
138:02 things and they're typically on the order 300 km wide and there circular and
138:09 in many cases And they're pretty shallow general, like three km and
138:16 you know, they're just just just , you know, down warps in
138:21 crust that collects sentiments. But no knows how these things form, which
138:26 pretty interesting, isn't it? That way it always works? The simplest
138:30 geometrically is something that no one knows far there are actually like 11 different
138:36 for how these basins. For a named George Klein published a paper back
138:41 80 78, something like that where reviewed 11, 11 different theories for
138:47 these basins were in general. You group them into like, is this
138:51 a thermal, is there some heat beneath it? Or is there a
138:56 in the rocks that produced that Or is there some sort of,
139:03 know, um listen, is tina density variations into it or the old
139:10 magmatic under plating and cooling of And pulling it down. My favorite
139:16 is thermal. I think it's just be related to heat. That's
139:20 that's just where I'm going on this just because the other ones just seem
139:24 little too exotic to me, you ? Um I mean, there are
139:29 anomalies everywhere. So I kind of that. Alright, so here's the
139:36 basin which is a crustal sag and shaped shaped like this um this little
139:42 , that's where I grew up in . And then here's some fizzy a
139:48 elements. So there's the, what's here on dome. This is the
139:54 dome, the uh, I guess something, something park dome, there's
140:01 an old bridge, definitely the arch in the cases physiognomy and this is
140:07 on top of it. Here's uh gravity anomalies. So, um these
140:18 are not really helping us and understanding base in january. They are.
140:23 mean, there are some smooth anomalies here and there's some shorter wavelength anomalies
140:28 around over here and in here, shorter wavelengths. So, you do
140:33 the sense that, you know shorter here, but you do get the
140:36 that it is a little bit Just looking at gravity data alone.
140:42 magnetic data, that's a better help data is usually better about this.
140:47 all rocks have mass, but not rocks have magnetic susceptibility. Not all
140:54 are magnetized in a way that, know, that makes them whatever closely
141:02 . But here, you can see definitely getting longer wavelengths in the center
141:05 the basin here and some really short chatter around here. But then kind
141:11 intermediate wavelengths through here. So long , intermediate wavelengths. Short wavelengths.
141:18 you see those? Yes, So, Magnetics is the tool for
141:28 . It's a tool for mapping terrain it's a tool for estimating basement depths
141:34 and thicknesses. Okay, here's the geology. So the colors are these
141:41 and brownish colors. These are all pre Cambrian, rather pre Cambrian rocks
141:50 key in and protozoa and then the to purples are paleozoic green is
141:58 And then I don't think there's any era rocks. So these are eras
142:05 these are aliens by the way. pre Cambrian is not an error or
142:10 ian. It's just just what people . All right. And you can
142:16 us a basin because you're getting into you're getting into younger rocks from the
142:23 in, right? I'm sorry, rocks from the inside out.
142:28 younger rocks. Yeah, I said . Right. Yeah. So these
142:31 younger rocks and then as the base shaped like a bull. So that
142:36 the if you're gonna flatten flatten a like layers, half of an
142:42 then the outside ones are gonna be older ones and they're gonna be rimming
142:45 . So this is shaped like a and here's some structural contours on the
142:52 of this artificial limestone called the Trenton the michigan Illinois. And the
143:00 So the Appalachians. The foreland michigan and Illinois basin are crystal sags
143:06 based. And these are in feet sure. So that's 10,000 ft
143:12 2500 ft and so on. The dome, Cincinnati dome friendly arch,
143:22 are all connected. The Kankakee we looked at the algonquin arch and
143:28 we looked at um and there's the all these features here, all these
143:35 graphic elements. Alright, we can can lay that on top of the
143:40 and we're not gonna get a lot joy out of that doesn't only show
143:43 a whole lot of stuff. Um can land types of gravity.
143:49 the gravity is sort of useful but not really, you're really gonna
143:54 you're really gonna have to model this up with gravity. You really want
143:58 learn something about the subsurface here with to gravity data. But with magnetic
144:05 , that's pretty good actually because you see the Whelan's getting deeper into the
144:11 into the michigan basin. You getting broader into the, into the
144:17 basin here and then you know, wavelengths getting smaller sort of intermediate lee
144:27 then where those domes are and it's just outcropping just just high,
144:34 know, short wavelength chatter. Now , this, this stuff up here
144:39 just flat because there's no data because is pretty ugly out there. Well
144:46 look at the basement terrain. so there's the basement structure. But
144:51 there's the terrain of that structure. , remember these are like this is
144:57 Grenville front that came in a billion ago. These other terrain, the
145:01 rye light um that's, you older, 1.3 billion years ago.
145:09 then Superior. Remember that's our So that's very old. So you
145:14 photos are created and then, you , the Grenville was at the,
145:18 know, about a billion years And then here's how that looks at
145:24 of the gravity. That's nice. at that, that big anomaly going
145:28 the summer here. That's that's uh completely different. That's actually part of
145:35 mid continent rift, which comes up , wraps around and ends up going
145:40 through through the mid continent, you see how it does it here
145:46 And then the different other terrain is they that are that are here.
145:55 then looking at it with the So, the magazine a bit more
145:58 , you can still see this, , you know, the mid continent
146:02 in here, but it's not as not as well defined as with
146:05 So, it has a definite density to it. And then the
146:10 Um you know, the gravity data really helping us as much. You
146:17 see these these speeches in here. mean, you do see this thing
146:20 you once, once you learn where is, you go, I see
146:24 a you can kind of trace it here. You know, you can
146:28 of trace the boundary of this high here with this this year. So
146:32 can't see it once you sort of into its general location. All
146:38 Uh So this is a Cambrian through currencies substance history of the michigan
146:48 Right. Um So michigan basin paleo . So this is about paleo
146:57 Um And according to them, the magnetic pole is at 52 degrees
147:04 111 east. So where we Do I have any coordinates here?
147:09 the pole is is west of here just slightly north of here. The
147:19 paleo Mag pole. It is similar those recognized for the carbonates in Ontario
147:25 york state, suggesting that the michigan were re magnetized in the late paleo
147:31 . Rock magnetic characterizations suggests that the magnetization is carried by a single pseudo
147:41 domain mega type. What do they , art calculated from? Okay,
147:47 they're saying the paleo Mag magnetic paleo are similar to the paleo magnetic directions
147:54 in the ordination threatened carbonates from the basin. So let's see this is
148:04 the evolution of the basin. So saying it was a trough shaped open
148:09 the south. Then it was a basin where the center base and then
148:16 to think the basin tilted to the . Then it was that a broad
148:22 that abroad centered basin, narrow I guess that just means it's kind
148:26 like level but there's this basin center broad, narrow basis center is narrow
148:33 center abroad and then it tilted again the east again. So this is
148:38 these guys are saying based on paleo data. All right now. Uh
148:46 this is some from your uh this highs and basement trains. Yeah,
148:55 , so this is in southern southern . So they sampled the lime stones
149:02 um uh you're saying as again as said late re magnetization at around 3
149:11 to 3 to 2 92 M. . So that's that's or division.
149:18 let's see. So they did that and these folks did it in Ontario
149:28 they want to use what are we ? So this is the reconstruction of
149:37 . Okay, I need to I to look at these. Um
149:42 Okay let me let me get back you on that failure may suffer.
149:48 , so here's the different terrain from and others and so there's granite.
149:53 sick exclusive rocks, Medicine, Cherie Messick intrusive. Remember this is where
149:58 a rift, this is an old area. So you have, you
150:03 uh nice granule. It's there's also structure here. There's a little structure
150:12 . Okay, so here it is top of the gravity again, zooming
150:16 and and I guess what, he's at this linear here and say okay
150:22 could be a train, this is maybe possibly a change in the composition
150:29 thing down here. And he's alright, he's looking at these anomalies
150:34 he's interpreting a different terrain here. does it look kind of magnetic?
150:40 ? I think it makes a little more sense into my medic data.
150:43 definitely a boundary here, definitely a here. You know, you can
150:48 see, even though it goes from high to a load, it's still
150:53 . And then um so basically this using magnetic data. Remember we can
151:01 it for sourcing for estimating source depth wavelength, but we can also use
151:07 to map terrain. Remember high aptitude , hundreds to thousands of nana
151:14 Those are indicating with a logic In other words, rock composition
151:21 So you can draw a line here you can say ah this is a
151:26 in composition, this is a different type. Maybe this is an old
151:31 , who knows? But it certainly like it's a difference in rock
151:35 J. Also, you can see wavelengths are really getting smaller going up
151:43 versus the wavelengths over here where they're of broad. This is kind of
151:47 center of the base, same thing . All of a sudden you have
151:51 big high amplitude anomalies. This is change in rock type. So this
151:54 a train boundary. And also you also just talk about the data character
152:01 general, right? I mean you definitely see a difference from here to
152:07 to here. This area looks quite and the same thing down here.
152:12 area, right? Looks quite different uh other places. So that's what
152:20 that's how you can you know, interpret, using interpret to reigns using
152:28 data. Magnetic data is good for steps and terrain. Okay, so
152:35 some contours and it's based on this well penetrations, these diamonds, there's
152:43 magnetic estimates like Warner or what have ? Probably slope. This is
152:49 So these points are probably basically that's slope. And then uh basement magnet
152:59 contour. Okay, I just don't about that. So. Right.
153:02 this is the general this is contoured uh thousands of feet. So it's
153:09 to 13 over 15,000 ft deep here 5000 ft to the basement around the
153:16 of it here. What does that like under gravity data? Well,
153:21 kind of interesting. I mean, of all this anomaly here looks like
153:25 is a structural component but the rift over kind of files these contours.
153:32 that's really interesting. And but in um I guess if you kind of
153:39 your eyes and turn your head you might you might see how this
153:43 in there. Let's see what it like the magnetic data. And
153:48 this is this is I think this really looks pretty good actually. I
153:53 um there's an anomaly. So this is not just compositional and structural as
153:59 . Which is possible. But you really you know unless you unless you
154:02 data that helps you with that then know that's not a good idea.
154:08 they've got they've got whatever for well down here. They got some death
154:13 . So that's pretty good. All Now let's get back to this.
154:25 . Can we go back to slide three and 84? Can you explain
154:32 ? Like to me the the gravity better. So can you explain why
154:38 magnetic looks better as compared to the ? You mean in terms of the
154:44 ? Yes. Because you you said you like the way the magnetic looks
154:48 lot better. And and I guess just like focusing on the middle part
154:52 to like to me it looks a better. So yeah. So you
154:59 see the wavelengths here are broader and . Do you see that than around
155:04 here and over here. Do you that? So this is where that
155:15 Archie Algonquin arch comes through. This is the the edge of the
155:20 dome and some other, I can't the name of that dome up
155:24 But there's another, you know, basement up here. And so these
155:29 wavelengths, it's just this chatter, almost looks like it's noise.
155:34 There's so many anomalies and that's because basement is very, very shallow.
155:40 then as you get deeper into the , these wavelengths tend to start to
155:45 out because it's just getting deeper. when we look at gravity, you
155:51 really get that sense. You do of I mean, there's some short
155:54 like anomalies out here, you But but really the gravity looks a
156:02 bit more monotonous. I mean, certainly does. I mean, regarding
156:06 rift that's booming. That's that's just out. You can see that really
156:11 . But aside from that, you , do we have a basically a
156:15 basin here? And you would expect see short wavelengths on the rim.
156:21 wavelengths in the center. And you be able to talk yourself into that
156:26 this. But it's I mean, not at all that obvious. You
156:30 what? Whereas but with the I mean, to me, it
156:36 sticks out. You have all these long wavelengths surrounded by these short
156:41 There's a basin in there. You , maybe it's complicated because, you
156:47 , you have some intermediate wavelengths sneaking here. So maybe there's some structural
156:51 going on here. But overall this a big basin and is surrounded
156:57 you know, base I mean shallow . And yeah, there's some complexity
157:02 here. There's definitely, you the stuff you can sink your teeth
157:05 it really investigate this and model it and do whatever, Right? I
157:10 it's lots of fun stuff you can with this but in terms of just
157:14 at it. It's just first Yeah, I can see this basically
157:18 data. I hope that you can know that makes sense I guess to
157:22 like it looked worse but it's good it looks worse because then you can
157:27 a lot more that's going on. that makes sense now. Right?
157:32 . Exactly. These these this I I'm sure there is noise in here
157:36 but but this a lot of this just it's really this is just very
157:41 basement and once you zoom. I , you know this is why land
157:45 data. It's not very good because get so close to these sources.
157:49 just got it's just swamped by the . Okay, thank you. So
157:55 the here's the Magnetics again. And . So you see in this country
158:02 mapping a little structure. There's some here. Right? So it's going
158:05 . So yes, so this is little structural high. It's not
158:10 you know, 500 ft. So it sits right on top of
158:15 , gravity not only which also sits top of this magnetic anomaly. So
158:19 is this is a case we have big anomaly that also has a structural
158:25 to it but that's the exception. I have rules of thumb. It
158:31 mean it's always like that but it there are guides of ways to think
158:36 the data, okay, now this going back to our paleo mag stuff
158:45 let's see there's a model, here's two D. Model over southwest michigan
158:52 They called the southwest michigan geophysical Smg a Singa may also be produced
158:59 a rift related to this. so they're saying that there's an anomaly
159:03 here, right, where's that That's down here. They're saying there's
159:07 anomaly down here that's related to this . Where is it? Yeah,
159:15 an army down here, it's related to that and here's a little cross
159:22 they made to it. So this through the mmr the mid michigan,
159:27 is the rift that we're looking See all the contours. I'm saying
159:31 one is right down here and you're it's producing an anomaly. 2.9 density
159:38 .7. So that's not a bad . Let's look at the gravity,
159:43 this anomaly here, I'm sorry, this anomaly. So they're saying even
159:48 there's some the contour is in there they're saying this anomaly is related to
159:53 . So there the rift may have complex, right? So even though
159:58 looks like it bends here, there be a bit of a component
160:01 I don't have a problem with that's fine. Um Yeah it is
160:07 big anomaly. Well it's the seats mg, that's a pretty good
160:11 But this one here this is $60 . That's just a big anomaly
160:20 Um Right and they actually shot a court line across. Um It's the
160:25 think it's like the very first co line. You know what co corp
160:30 ? No so core korps was the was the U. S. Whatever
160:37 program carried out in the 70s and I think. Where they shot these
160:42 long offset long time sections all around country. South Georgia riff that this
160:52 other areas Anadarko basin um In uh think in the east Texas bass.
161:00 they shot one and Yeah an East one through east Texas. And and
161:07 anyways They also shot this line through , well the McClure 1-8 sparks and
161:16 McClure one dash hey Sparks drilled this , they drill down in through the
161:22 the way through the basin and into into that rift segment. Those matric
161:29 . Okay. Um And they actually a borehole gravity survey of it which
161:37 very cool. So they drilled five . They drove through almost a kilometer
161:45 , wait a second how much? Cambrian they drilled through looks like 500
161:52 500 m of of that rock. um So they drilled through 1600 m
162:02 classic and uh read classics. Heavy , especially with English rocks near the
162:11 michigan whatever near Ithaca michigan. And Borehole density survey indicated 2.77. This
162:21 2.77 Uh plus or -105 for the beds. And then according to Vander
162:30 and Watts, this would be the famous rob Van de Vue and the
162:34 more famous Tony Watts that his body the base of the borehole, maybe
162:40 altered lava flow. And its mechanization likely to to be entirely secondary.
162:46 they don't think it's uh during the the Cambrian time. So they think
162:53 it was re magnetized after after the continent rift form. Alright, so
163:03 that's all good and fun. So here's our bouquet gravity and here's some
163:07 lines and cross sections that I did here. And I actually have two
163:13 . Models through each for each of . And I'm gonna show you,
163:17 think I'm going to show you And B. Because I have actually
163:23 . So here's Model B, two . Pride. So this goes,
163:28 you have, okay, I have stations, those are these inverted
163:33 And there's two numbers, there are I believe. So the first number
163:40 depth to crystalline basement. Second number to the mojo. So it's 1.2237
163:46 two. And when there's just one , that's just basement. Right?
163:50 they all intersect here at this basement station where the basement is 2.83 kilometers
164:00 Questions. The basic gets deeper up . 4.5 - 41.1. And we
164:08 have two mojo re fractures in in . So we also look at B
164:13 B. Primed A. And everything here. So here's my real simple
164:20 model. B. Two B. . Uh There's a there's a mojo
164:25 down here, basement here and then here. And then this is the
164:31 of lines A. And D. C. Alright, so let me
164:38 let me just quickly I have this open. Let me see. I
164:42 so now I don't know if you able to down but were you able
164:45 download this stuff yet? Not My husband, he actually has a
164:50 computer. So he's gonna download I'm really happy about that. That's
164:58 . I have the in the instructions I sent you. I said you
165:01 to settings, uh manage menu and will pop up this little thing and
165:09 do this extension and you'll click on one here and then. And that
165:14 load. Did I just unload Oh man. No, I
165:24 Okay. All right. And that load this menu. Gm says profile
165:29 . And I always go new And I always got a new model
165:33 I go down here to run GMC . So I run it. I
165:38 the modeling software outside of this main . And this is all we're gonna
165:42 . We're not going to use the program that has a bunch of maps
165:46 databases and stuff in it. Um worry about that, don't ever click
165:52 , don't do that. Um And here's here's this, here's the GMC
166:01 program. So I'm gonna open up that model, it's in michigan.
166:13 , I'm Gonna Open Up B two Prime. I'm Gonna Open Up This
166:20 . Let me open up this Uh Let me see. Maybe I
166:24 this one and we'll see what Okay um yikes that's Oh I
166:33 let me close this, let me it to the other one. I'm
166:40 Open up the other one. It be exactly what you have there.
166:46 not dog on it. Look at , there's the gravity profile. I
167:02 I have the mag profile there So like all the other ones gravity
167:05 the bottom bags on top. I've gravity profiles, maroon. This is
167:11 bunch of dots. They're just real together. Same thing with the
167:15 So I have this color different. don't really like the color patterns but
167:20 is um this is uh can right here in auto scale what we're gonna
167:29 looking at. And just to show can this little hand says move move
167:35 point, you can move a point you want, you can grab this
167:42 , you move a point and this sort of like I always when I
167:47 I work with clients, I like do these modeling on the fly in
167:52 because it's like so manager friendly so can grab this one here and move
167:58 model there and that can also create point here and kind of do that
168:05 that business greater point here. so now I'm kind of right now
168:11 have a bunch of misfits over I can actually zoom in on
168:16 I'm just giving you a little demo the software if you don't if you
168:20 you're okay with that, look at , that that's not nice. Um
168:27 , so all right, and you you can then um you know,
168:36 can add points. I'm gonna add point. You can add a moon
168:40 the same time too. So you , you know um Then I can
168:52 you just and you just move them adding Okay enough of that and then
169:12 you've got the view. So you also do things like change the density
169:22 the fly. So let me so for example this this this eyeball
169:26 the examined button and you can click a source and it will tell you
169:31 about it, it will tell you you know the colors will tell you
169:35 density, it will tell you the , right? Susceptibility and then if
169:42 turn on this two or three quarter it will tell you, you know
169:47 far in and out of the plane goes and what the density in and
169:51 of the plane is. Um uh can also do things like hit this
169:58 . C. Thing and that will up another little window and um You
170:06 and it has a slide bar and can set the limit on the slide
170:10 and make this 3.3.3 for example. then you can grab that slide bar
170:17 in real time you can adjust the to make it fit in real
170:22 So that's kind of fun. That of blows people away. So
170:28 I just thought I'd give you a preview of of the software before we
170:35 for lunch and we can go back the presentation if you like. I
170:42 we're wait, that's this afternoon. just what I just did.
170:48 Um Oh I have one more study we can of the congo basin.
170:55 another, it's another crustal sag. can just do that very quickly and
171:00 we'll break for lunch. But I want to show you. I just
171:04 to show you like a little bit the software to kinda kinda get you
171:07 you excited about if that's possible. I get you excited about the modeling
171:13 any case. Um Congo basin is younger one is formed in the late
171:18 and into the Triassic. This is I'm saying that they're not just pre
171:23 basis because of this one here. They have yeah, they have into
171:32 cretaceous even. Um Right. And is a study. This is uh
171:37 is actually kind of like goes into these basins for um They estimated density
171:43 from sediment. Then they subtract that a process we call gravity stripping or
171:49 stripping. It can be perilous because just you can end up producing analogies
171:55 that. And then they decided that um that that there was crustal necking
172:05 thinning of the crust beneath this So they're saying that there's structural things
172:10 on to this base in formation. , so on the left are the
172:16 air. Now remember that has that topography in it. And so but
172:22 area is pretty flat actually. Um think right. What we're looking
172:28 we're looking at this is a geologic but there's no there's no what are
172:35 contours? These contours are the base thickness I think. Okay,
172:40 alright, so and then and then the right is there um uh calculated
172:48 from the basin from the sedimentary So they subtracted that what the residual
172:58 subtracting that is is well, I'm , the calculated gravity attraction of the
173:07 is on the right, Okay. the residual gravity is calculated by subtracting
173:13 from the sentiments um is what it like on the left. That's the
173:19 And so they're saying um subtracting Yeah that's the same right? The
173:26 on the right is the same. subtracting from the right from the free
173:31 , you get this one this one's the left and you have this big
173:36 anatomy in the center. And then did a model cross section, a
173:40 D. Cross section. So let just make sure I'm not confusing.
173:44 this is a surface geology map and showing young rocks towards the center as
173:50 would expect for for a basin With the older pre Cambrian rocks reminiscent
173:57 like the michigan basin. Then on left are the free air anomalies and
174:03 the right is the gravity response of basin rock. So I don't have
174:09 map of the sedimentary rocks. I they're quite like this map here.
174:14 then this would that thickness of sediments produce this gravity response Which is very
174:23 . It's let's see it's maybe 20 gallons on that order. This is
174:28 interval Is 10. It's 30 bucks mg I guess. And so they
174:37 that the map on the right from map on the left and that
174:43 this map on the left. so that ranges, that whole range
174:48 customized. 40 mg roughly. Okay then they took a cross section through
174:56 this line here and they did a D. Model on that and that's
175:01 you're looking at here. This is of complicated. What they did was
175:04 tested they tested the contribution from of combinations of necking. In other words
175:14 thinning here uh versus equivalent elastic thickness . Okay so basically elastic thickness calculations
175:26 on the the whatever the topographic the steering model. So the observed data
175:37 the black line And from the equivalent thickness calculations going from 10 to 100
175:49 on the left and death of That's how in other words thinning of
175:56 crust. They did 5 30 10 30 10. So the two reps
176:04 5 30 10 on 10 and 100 last evening. So they had to
176:10 depths of E. T. And each of each one of those two
176:16 did three flavors of necking and they The necking of 10. So that's
176:26 top one the red one for both these and E. T. Equivalent
176:32 thickness of the little sphere um of . The red is the best combination
176:41 that's this red one here. And from that this is the shape of
176:46 basis. So there's supposed to be structural high in the middle of the
176:51 that they have modeled. I guess strikes to the northeast northwest rather.
176:56 that you have two basic depot centers what you're saying. Uh this is
177:02 geodynamic work. And again so this the structural high they have this this
177:09 the anomaly that they're trying to And I think we can look back
177:18 going through here. Yeah. I know maybe maybe maybe I'd confused you
177:25 this. But this was this was paper like I said what they were
177:30 was trying to estimate the process how basins formed. And they figured well
177:37 they remove the sediment layer then they'll have the crustal layer and they can
177:41 the crustal layer. And there's two of doing that geo dynamically. You
177:46 estimate the equivalent elastic thickness. Um just calculating fletcher. And then you
178:00 and then they did the model was testing the response from necking. And
178:07 just did that by I guess adjusting horizons here in a forward sense.
178:14 they have the ah yeah yeah yeah . Where's the other one of these
178:17 where's the where's the E. O. Red light? Oh look
178:23 that. You see this one you the thin lines. Oh yeah okay
178:32 is really interesting. So the necking thin a thin neck and a thick
178:42 thickness prisoners big this big blue thick one at the other end. Okay
178:55 thick neck. 30. And they um E E. G. Produces
179:03 one the stine blue one. So both with a a thick neck.
179:13 sorry wait a second. No it's . Right think right. That's both
179:20 five uh kilometers necking. So a thin neck. five km of
179:27 Thin necking. Was it thin or elasticity? That's just blue. And
179:36 the thick neck 30 is green thick and and thick elastic thickness. It
179:46 produces this just this depression here which you know like the other but thick
179:58 and thin E. E. Produces this one. So the elastic
180:06 it really has. Um It basically enhances everything, doesn't it? But
180:13 totally inverts for red. The intermediate medium necking, the intermediate necking compared
180:22 the then and thick elastic. The lines goes from producing a low high
180:33 to a high low high. I don't know. I don't know
180:37 this is proven. And then here just the response to all those things
180:42 here again. What is this one here? I'm not sure what this
180:50 not here. Alright, so I'm gonna test you on this one if
180:57 want. I can send you the . It's kind of interesting but it's
180:59 lot of geo dynamics. Um yeah in any case it's 1142. Um
181:08 we reconvene at 12:30. Okay, sounds good to me. All
181:14
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