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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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