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Transcript

The Michigan Basin · PlanetGeo: The Geology Podcast

• 0:02
  SPEAKER_01: Welcome to Planet Geo, the podcast where we talk about our amazing planet, how it works, and why it matters to you.
• 0:12
  SPEAKER_01: I'm recording.
• 0:13
  SPEAKER_01: I'm recording there.
• 0:15
  SPEAKER_01: The red lights on.
• 0:16
  SPEAKER_01: Oh, there it is.
• 0:17
  SPEAKER_01: There it is.
• 0:17
  SPEAKER_01: The red lights on, Chris.
• 0:19
  SPEAKER_01: Check.
• 0:19
  SPEAKER_00: You ready to go?
• 0:20
  SPEAKER_00: I'm ready to go.
• 0:22
  SPEAKER_00: The question is, are you?
• 0:23
  SPEAKER_00: You always you just follow my coattails.
• 0:25
  SPEAKER_00: I am hold on, Mr.
• 0:27
  SPEAKER_00: Coattails.
• 0:29
  SPEAKER_01: I didn't I didn't plan this.
• 0:31
  SPEAKER_00: What are you doing?
• 0:32
  SPEAKER_00: Oh no.
• 0:38
  SPEAKER_00: Yes.
• 0:39
  SPEAKER_00: Hey, where's mine?
• 0:40
  SPEAKER_00: You did not plan this well at all.
• 0:42
  SPEAKER_00: Where's mine?
• 0:43
  SPEAKER_00: I should have a delivery.
• 0:45
  SPEAKER_00: I should have a delivery guy at my door right now, handing off a planet Geo hat.
• 0:51
  SPEAKER_00: Okay.
• 0:52
  SPEAKER_00: And a special delivery from Dr.
• 0:54
  SPEAKER_00: Jesse Rymank.
• 0:55
  SPEAKER_01: I should.
• 0:56
  SPEAKER_01: I should.
• 0:56
  SPEAKER_01: So what do you uh what do you if I can get this thing on my head?
• 1:00
  SPEAKER_01: My head is abnormally sized.
• 1:02
  SPEAKER_00: It is, and you have a lot of hair.
• 1:04
  SPEAKER_01: So I have a giant head with a lot of hair.
• 1:06
  SPEAKER_01: What do you think?
• 1:07
  SPEAKER_01: I love it.
• 1:07
  SPEAKER_01: I'm looking at a hat.
• 1:09
  SPEAKER_00: You got the man bun coming through the little notch in the back.
• 1:12
  SPEAKER_00: That's yeah, coming off the back.
• 1:14
  SPEAKER_00: Yeah.
• 1:15
  SPEAKER_00: Oh my gosh.
• 1:16
  SPEAKER_00: You can wear it, right?
• 1:17
  SPEAKER_00: I had no idea this was coming my way.
• 1:19
  SPEAKER_00: I'm really disappointed though.
• 1:20
  SPEAKER_00: I I should have somebody knocking on my door right now.
• 1:23
  SPEAKER_01: I know, I know.
• 1:24
  SPEAKER_01: Special delivery.
• 1:25
  SPEAKER_01: Turns out it was going to be expensive to have a white glove delivery service to deliver you your hat.
• 1:31
  SPEAKER_01: So yeah, this uh Chris, we got merch.
• 1:34
  SPEAKER_01: We have merch available.
• 1:35
  SPEAKER_01: I mean, we're starting small, a hat and a t-shirt.
• 1:38
  SPEAKER_01: I love it.
• 1:39
  SPEAKER_01: And uh, but you know, you can go to our website now, planetgeocast.com, and there's a merch link.
• 1:44
  SPEAKER_01: People can order this.
• 1:45
  SPEAKER_01: We'll see how we'll see how it does.
• 1:46
  SPEAKER_01: This is a cool hat, though.
• 1:47
  SPEAKER_01: Like green trucker hat with a black Planet Geo logo.
• 1:50
  SPEAKER_01: Pretty good, right?
• 1:50
  SPEAKER_00: I think so.
• 1:51
  SPEAKER_00: And I like it too because you know, like the patina on a hat, right?
• 1:55
  SPEAKER_00: When the when the sun starts to fade it and the sweat gets involved, you know, that's gonna show pretty well.
• 2:01
  SPEAKER_00: Like I'm gonna use that hat.
• 2:02
  SPEAKER_00: That's gonna be a working hat, okay?
• 2:05
  SPEAKER_01: You're gonna yeah, you're gonna get the sweat stains on it.
• 2:07
  SPEAKER_01: Yeah, yeah, yeah.
• 2:08
  SPEAKER_01: Yeah, absolutely.
• 2:09
  SPEAKER_00: I'm one of those guys, like when I get sweat stains on my hat, I leave them.
• 2:13
  SPEAKER_00: Rarely do I like wash my hats, and I don't know if you're of course you're gross.
• 2:18
  SPEAKER_01: But you're bald, so you get sweat stains probably all over the hat, not just at like the at the rim like normal people do.
• 2:24
  SPEAKER_00: That's true.
• 2:25
  SPEAKER_00: That's true.
• 2:26
  SPEAKER_00: Yeah, it and it actually is, yeah.
• 2:27
  SPEAKER_00: I love it though.
• 2:28
  SPEAKER_01: That'll put that'll put a nice patina on.
• 2:30
  SPEAKER_01: Absolutely.
• 2:31
  SPEAKER_01: It'll be good, right?
• 2:31
  SPEAKER_01: Yeah, yeah, like totally.
• 2:32
  SPEAKER_01: There's there's a like a t-shirt option and a hat option at the moment.
• 2:35
  SPEAKER_01: And you know, if people like them and want some other designs, let us know.
• 2:39
  SPEAKER_01: We can update them.
• 2:40
  SPEAKER_01: I've been trying to convince my wife to have the the black it's a black t-shirt with a Planet Geo logo on it.
• 2:45
  SPEAKER_01: I've been trying to convince her that putting erosion happens on the sleeve would be kind of nice.
• 2:50
  SPEAKER_01: Yeah, I like it.
• 2:52
  SPEAKER_01: Good idea.
• 2:52
  SPEAKER_01: Yeah, okay.
• 2:53
  SPEAKER_01: Well we'll see, we'll see.
• 2:55
  SPEAKER_00: Anyway, yeah, I was just thinking about this the other day.
• 2:57
  SPEAKER_00: Actually, just yesterday, I was walking out, I was going to practice, and I'm thinking, wait a minute, I have not heard from Tess, you know, lately on the merch idea, because this is really her thing.
• 3:06
  SPEAKER_00: Yeah, yeah, yeah.
• 3:07
  SPEAKER_01: You got she got this in her head and wanted to do it.
• 3:09
  SPEAKER_01: So there we go.
• 3:10
  SPEAKER_01: Yeah, that'd be good.
• 3:11
  SPEAKER_01: You know, wear this hat, not too bad.
• 3:13
  SPEAKER_01: I I don't uh usually like baseball caps.
• 3:16
  SPEAKER_01: I have too much hair, I've got too much brain in my head for them to like really.
• 3:20
  SPEAKER_01: Is that what it is?
• 3:20
  SPEAKER_00: You have too much brain to contain, don't you?
• 3:24
  SPEAKER_00: Yes, okay.
• 3:24
  SPEAKER_00: I think that's right.
• 3:25
  SPEAKER_00: That's what I've heard.
• 3:26
  SPEAKER_00: Yeah.
• 3:27
  SPEAKER_00: Yeah.
• 3:27
  SPEAKER_00: You've heard it as you're looking at yourself in the mirror.
• 3:30
  SPEAKER_00: So I don't uh usually wear baseball hats, but this one's pretty good.
• 3:33
  SPEAKER_00: I like it.
• 3:33
  SPEAKER_00: I do.
• 3:34
  SPEAKER_00: I wear them all the time because I'm bald and I I have to really be careful of getting sunburned.
• 3:39
  SPEAKER_00: So gotta protect that noggin.
• 3:41
  SPEAKER_01: Well, okay, there we go.
• 3:42
  SPEAKER_01: How about that for an intro, Chris?
• 3:44
  SPEAKER_00: I love it.
• 3:44
  SPEAKER_00: I had no idea this was going on.
• 3:47
  SPEAKER_00: All of a sudden you disappeared from I'm like, what is he doing?
• 3:49
  SPEAKER_00: Are you trying to crack your back or what do you have going on there?
• 3:53
  SPEAKER_01: Well, uh, so yeah, merch available.
• 3:55
  SPEAKER_01: There we go.
• 3:56
  SPEAKER_01: Head to our website.
• 3:57
  SPEAKER_01: There's other ways to support us too.
• 3:58
  SPEAKER_01: You can uh download our mobile app, buy some audiobooks, but this is another way.
• 4:01
  SPEAKER_01: So, you know, and you get some merch out of it.
• 4:03
  SPEAKER_01: It's kind of cool, Chris.
• 4:04
  SPEAKER_01: Today, this is are you like in a relaxed mode?
• 4:08
  SPEAKER_01: Are you just like really happy right now?
• 4:10
  SPEAKER_01: Because we're gonna talk about like Mich we're gonna talk about Michigan today, really.
• 4:13
  SPEAKER_01: And this is home turf.
• 4:14
  SPEAKER_01: You love talking about Michigan.
• 4:15
  SPEAKER_00: I do love to talk about Michigan, and and I'm sitting in Michigan right now and on my awesome property, and it is a beautiful fall day.
• 4:24
  SPEAKER_00: I do I love this, like it this is perfect.
• 4:26
  SPEAKER_00: So 100%.
• 4:28
  SPEAKER_00: You have couldn't have 100% of Chris's.
• 4:31
  SPEAKER_01: We're gonna think about the rocks a little bit beneath your feet, all the way down to way beneath your feet.
• 4:35
  SPEAKER_01: The rocks we're gonna talk about are not near me right now in state college, but I'm close to it.
• 4:39
  SPEAKER_01: If I get up on a ridge, I can see similar rocks to what we're talking about.
• 4:42
  SPEAKER_01: They're over in western Pennsylvania and then they kind of bridge up to Michigan.
• 4:45
  SPEAKER_01: But we're talking about the Michigan basin, and I think one thing I would like to highlight, Chris, is basins generally, I think there's um some misconceptions.
• 4:54
  SPEAKER_01: They're not the easiest to understand, they're not the most intuitive.
• 4:57
  SPEAKER_01: What we refer to as sedimentary basins.
• 4:59
  SPEAKER_01: And I think there's reasons for that, but in part we talk about different types of basins in geology.
• 5:04
  SPEAKER_01: In this one, we're talking about sedimentary basins.
• 5:06
  SPEAKER_01: We're going to focus on the Michigan basin.
• 5:07
  SPEAKER_01: And this came from a listener question from John.
• 5:09
  SPEAKER_01: So, John, thanks for the great question here about the Michigan basin.
• 5:12
  SPEAKER_01: But this is home turf.
• 5:13
  SPEAKER_01: I grew up in Michigan, Chris, you live in Michigan, still you know, teach how much do you talk about Michigan geology?
• 5:19
  SPEAKER_01: I know you do your field trip up to the the upper peninsula and you talk about that, but how much, I guess, not Michigan geology, but the Michigan Basin.
• 5:26
  SPEAKER_01: How much do your students learn about the Michigan basin specifically?
• 5:29
  SPEAKER_00: Um, I talk a lot about it actually.
• 5:31
  SPEAKER_00: I uh really because I do.
• 5:33
  SPEAKER_00: And actually, it's been a long time since you've been down in my neck of the woods on my campus there and seen my room.
• 5:40
  SPEAKER_01: Yeah, actually, Chris, I'm coming to do that.
• 5:42
  SPEAKER_01: I'm gonna do that uh what early November.
• 5:44
  SPEAKER_01: We'll be down hanging out uh.
• 5:46
  SPEAKER_01: That's right.
• 5:46
  SPEAKER_01: Yeah.
• 5:47
  SPEAKER_00: Whenever I get like really artistic students, I ask them to do something.
• 5:51
  SPEAKER_00: Either take a ceiling tile down from my ceiling and paint a ceiling tile, something geologic or or astronomy related, whatever.
• 5:59
  SPEAKER_00: And I also have students that have painted murals outside down the hall, down the science hallway there.
• 6:05
  SPEAKER_00: So I have like five walls.
• 6:07
  SPEAKER_00: There's Garden of the Gods, there's a mountain climber, just really talented people that have done these gigantic murals, right?
• 6:15
  SPEAKER_00: And one of those walls is of the Michigan Basin.
• 6:19
  SPEAKER_00: So it's that important to me that I'm like, let's put the Michigan basin on a wall.
• 6:23
  SPEAKER_01: That's great.
• 6:23
  SPEAKER_01: That's very cool.
• 6:24
  SPEAKER_01: Oh, awesome.
• 6:25
  SPEAKER_01: Yeah, yeah.
• 6:26
  SPEAKER_01: I'm excited.
• 6:26
  SPEAKER_01: I'm excited to see that in a in a month or so.
• 6:28
  SPEAKER_01: That'll be great.
• 6:29
  SPEAKER_01: So the Michigan Basin, this is a sedimentary basin, which is different from it's similar to what we call a structural basin.
• 6:37
  SPEAKER_01: Like we've talked about basins and domes before, especially the Black Hills of South Dakota.
• 6:41
  SPEAKER_01: You kind of talk about this dome structure where you get rocks that kind of get tilted on edge, and then you can see it from the surface, this sort of basin structure.
• 6:48
  SPEAKER_01: This is different.
• 6:52
  SPEAKER_00: Structural domes.
• 6:53
  SPEAKER_01: Structural domes.
• 6:54
  SPEAKER_01: But then we can also have structural basins, which are just the opposite of that.
• 6:57
  SPEAKER_01: You know, it also would make a ring if you tilt the sediments kind of up on all sides like a bowl, you cut through that and you you kind of have this circular ring shape of the sediments.
• 7:06
  SPEAKER_01: And there's parts of that that Michigan has too.
• 7:08
  SPEAKER_01: Michigan does have, if you look at a geological map, you see this bullseye pattern to it because the rocks are sitting in a basin.
• 7:15
  SPEAKER_01: But we're also talking about something a bit more fundamental, which is the structure.
• 7:21
  SPEAKER_01: If you look at a cross section of the basin in Michigan, on the west side and the east side, you have the same sedimentary layers.
• 7:28
  SPEAKER_01: They're thinner on the edges, and in the middle they're really thick, which means that if you follow the same layer, it's close to the surface, out on the edges.
• 7:36
  SPEAKER_01: And as you get towards the center of Michigan, it gets thicker and it's really deep.
• 7:41
  SPEAKER_01: The sediments are kind of draped down, and this has to do with how the basin formed.
• 7:46
  SPEAKER_01: It's not a structural basin, it's a sedimentological basin.
• 7:49
  SPEAKER_00: Meaning it's represented by the I think you just a sedimentological.
• 7:54
  SPEAKER_00: Is that a word?
• 7:55
  SPEAKER_01: Yeah.
• 7:56
  SPEAKER_01: Why not?
• 7:57
  SPEAKER_01: Petrological, sedimentological, metamorphic.
• 8:00
  SPEAKER_00: I I don't think it's a word, but nice.
• 8:02
  SPEAKER_00: It's it's a good go.
• 8:03
  SPEAKER_00: I like it.
• 8:04
  SPEAKER_01: Uh why not?
• 8:04
  SPEAKER_01: Take a crack at it.
• 8:07
  SPEAKER_01: Well, okay, Chris.
• 8:08
  SPEAKER_01: I've been blathering out.
• 8:09
  SPEAKER_01: What do you have?
• 8:10
  SPEAKER_01: Okay, what do your students learn about the Michigan Basin?
• 8:13
  SPEAKER_01: Or maybe high level where we go in this episode, and then and then let's get into it.
• 8:16
  SPEAKER_00: When I think about the Michigan Basin, I think about kind of like a self-fulfilling prophecy, I guess.
• 8:22
  SPEAKER_01: Oh, that's a nice way to frame it.
• 8:23
  SPEAKER_01: Yeah, I like that.
• 8:24
  SPEAKER_01: Okay.
• 8:25
  SPEAKER_00: You know, it's a really complex history where you have deposition, you have some tectonics involved, and you've got subsidence, and then one leads to the other and it perpetuates this cycle, and it just went on for an incredibly long, I think, an incredibly long period of time.
• 8:40
  SPEAKER_00: I mean, this was this was mostly during the Paleozoic.
• 8:43
  SPEAKER_00: And to timestamp that, it was like 540-ish million years to about 250 million years ago.
• 8:49
  SPEAKER_00: So, to the tune of about 300 million years, the basin was being developed.
• 8:54
  SPEAKER_00: When I frame it, I think I just frame it from that standpoint as just one thing led to another, which then just self-fulfilled.
• 9:04
  SPEAKER_01: Yeah, it's exactly right.
• 9:06
  SPEAKER_01: And just to frame this, Chris, if we look on a map, what we're talking about, the Michigan Basin, if you kind of draw a ring on a map, encompasses the entire lower peninsula of Michigan, all of Lake Michigan, most of Lake Huron, and then it kind of ends at that Indiana, Ohio border down on the south.
• 9:20
  SPEAKER_01: So it kind of is is centered right on the lower peninsula of Michigan.
• 9:23
  SPEAKER_01: It kind of overlaps into Lake Michigan.
• 9:26
  SPEAKER_01: And the way that people have documented this is both with drill core and seismically, with seismic imaging, we can see where the what's called the crystalline basement, the old rocks at the core of the continent, where do those exist?
• 9:41
  SPEAKER_01: And on the edges, they're very near the surface.
• 9:44
  SPEAKER_01: And as you go down towards the center of Michigan, right kind of in the the center of the lower peninsula, it's like 16,000 feet beneath the surface.
• 9:52
  SPEAKER_01: So there's sediment, even though Michigan's very flat, you look at it, you're standing there on Chris's beautiful property, you look out, it's pretty flat.
• 9:58
  SPEAKER_01: But we're kind of talking about where's the boundary, the geological boundary between sediments that have filled in the basin and the bottom of it, the old core.
• 10:06
  SPEAKER_00: That's a very good point.
• 10:07
  SPEAKER_00: If you look at Michigan from my backyard or from a hot air balloon, even and you look down on this, you you're not going to see a basin because it's all been filled in with kind of this glacial kitty litter.
• 10:17
  SPEAKER_00: So if you scrape all that away, 200 to 500 feet of it, then you will see the different rock layers that you described earlier that form this kind of bullseye pattern around it, where the older, thinner rock layers are exposed near the edges of the state of Michigan and they get progressively younger as you work to the center, and they also get progressively thicker as you work toward the center.
• 10:41
  SPEAKER_00: So, but you can't readily see that.
• 10:44
  SPEAKER_01: That's exactly right.
• 10:45
  SPEAKER_01: And I think that last point, the fact that they get thicker towards the center, that's the key point, at least in my mind, of that speaks to the formation process because we in the intro-level basic intro-level geology stuff, we talk about sedimentation.
• 11:00
  SPEAKER_01: We, you know, you can talk about sea level rise and transgression regression cycles.
• 11:04
  SPEAKER_01: You get shale deposited, then limestone, then shale, etc.
• 11:06
  SPEAKER_01: But we kind of think about that as like homogenous over distance.
• 11:10
  SPEAKER_01: So it's kind of like depositing limestone in a flat blanket on top of the seabed.
• 11:15
  SPEAKER_01: Right.
• 11:16
  SPEAKER_01: Um, but it's actually that that very rarely ever happens because there's structure on the seabed, especially back when continents were flooded.
• 11:24
  SPEAKER_00: So, Jesse, let's put a pin in that.
• 11:26
  SPEAKER_00: The really important thing for you, we'll come back to that because I do want to talk about that further.
• 11:31
  SPEAKER_00: Why is that when we first started talking about putting this episode together, that's the first thing that you said, and you keep coming back to it.
• 11:38
  SPEAKER_00: So I want to make sure that that you explain further in terms of why that's such an important point to you.
• 11:44
  SPEAKER_00: But let's instead first, let's just work through because we kind of broke this down into all right, here's how it started, and then this is what happened, and then this is what happened.
• 11:52
  SPEAKER_00: And when when we get to that point, then let's come back to why it's such an important thing to understand the thickening in the middle and the thinning on the edges.
• 12:03
  SPEAKER_00: Like, why is that geologically an important point?
• 12:06
  SPEAKER_01: Okay, so where I mean, where do we start with this?
• 12:08
  SPEAKER_01: We've got sort of the first step, the first stage.
• 12:11
  SPEAKER_01: And again, you you just to set the stage here temporally, you said Paleozoic on 500 million years to 250 million years ballpark.
• 12:19
  SPEAKER_01: That's the kind of window we're talking about.
• 12:21
  SPEAKER_01: What's the first?
• 12:22
  SPEAKER_01: I mean, do you presumably when you you're talking about this, Chris, you don't go through every sedimentary layer in the basin, do you?
• 12:28
  SPEAKER_01: Or or do you go into that?
• 12:30
  SPEAKER_00: That's to me, that's not important in terms in the scope of my gen.
• 12:33
  SPEAKER_00: That'd be, you know, later on, maybe a sed strat college class, something like that.
• 12:37
  SPEAKER_01: Sure.
• 12:37
  SPEAKER_01: All right, so how do you break it apart here?
• 12:39
  SPEAKER_00: How did the whole thing begin?
• 12:40
  SPEAKER_00: Because once it began, that set everything else in motion to for what happened in the next 300 million years.
• 12:46
  SPEAKER_00: And so we have to go back to a term that you and I talked about in um earlier episodes when we did what is a craton?
• 12:53
  SPEAKER_00: You know, the interior.
• 12:54
  SPEAKER_00: You love cratons.
• 12:55
  SPEAKER_00: This is your thing.
• 12:56
  SPEAKER_00: How long do we have?
• 12:57
  SPEAKER_00: You brightened up right there.
• 12:58
  SPEAKER_00: So this began with the North American Kraton.
• 13:02
  SPEAKER_00: Michigan was kind of at the edge of this craton, but this is a really broad, stable platform.
• 13:09
  SPEAKER_00: But then during the Cambrian, so right at the beginning of this Paleozoic 540-ish million years ago, the region started to subside very slowly.
• 13:19
  SPEAKER_00: And and this created kind of a saucer pan look.
• 13:23
  SPEAKER_00: And this was a tectonic subsidence.
• 13:26
  SPEAKER_01: Yeah, Chris.
• 13:26
  SPEAKER_01: That in that part right there, I think that's intimately related to what what we want to put a pin in, and we'll come back to is how do basins form?
• 13:33
  SPEAKER_01: Why is this tectonically subsiding, like what's going on there?
• 13:37
  SPEAKER_01: That's kind of related to the the basin structure again.
• 13:39
  SPEAKER_01: So let's come back to that and let's move on to the the second stage here.
• 13:44
  SPEAKER_01: What is going on?
• 13:45
  SPEAKER_01: We've got this Precambrian core, the old crystalline metamorphic rocks that are exposed at the surface.
• 13:52
  SPEAKER_01: This basin is starting, water's involved here because we're dealing with sediments.
• 13:56
  SPEAKER_01: And so, what's the next step?
• 13:58
  SPEAKER_01: Like what's happening next?
• 13:59
  SPEAKER_00: Well, once you have this tectonic basin, this kind of saucer pan that's created, then you have the opportunity for water to invade.
• 14:07
  SPEAKER_00: And that's exactly what happened.
• 14:09
  SPEAKER_00: So we're talking about shallow seas that invaded the area.
• 14:12
  SPEAKER_00: This goes back to what I led out with this kind of self-fulfilling prophecy.
• 14:16
  SPEAKER_00: So you have this tectonic basin that then allows for deposition or allows for shallow seas to invade, which then creates deposition, which creates weight.
• 14:28
  SPEAKER_00: And that's really the kind of the whole story is when you have deposition like we're talking about substantial deposition, that weight of the sediment causes it to subside and sink, which then exacerbates the subsidence, which allows for more deposition, which causes for more subsidence and so on and so on and so on.
• 14:47
  SPEAKER_00: So that's really kind of where we're at with that stage two.
• 14:49
  SPEAKER_00: The tectonic subsidence started the whole thing, shallow seas invaded the area.
• 14:54
  SPEAKER_00: Now, Jesse, hold on a second, though.
• 14:56
  SPEAKER_00: How do we know for sure that this was marine deposition?
• 15:01
  SPEAKER_00: What do the rocks tell us?
• 15:03
  SPEAKER_01: Yeah, I mean, you can look at the rocks, first of all, like carbonates are typically a marine deposition, shales, but you can also look at the fossil record in these things.
• 15:12
  SPEAKER_01: So, you know, I think one of the going to college in Michigan, uh, many field trips do not really get you into metamorphic Arignous rocks.
• 15:20
  SPEAKER_01: So we drive around and look at fossils a lot.
• 15:22
  SPEAKER_01: I remember going to, I think Alpina has a really nice fossil outcrop in the carbonate rocks there.
• 15:28
  SPEAKER_01: So yeah, you can look at the fossils, you can tell, okay, this is marine life, these are some reef environment, or this is deep sea or shallow sea or reef systems, you know.
• 15:36
  SPEAKER_01: So we can really work out the details there by looking at both the sediment itself and the fossil record in the sediment.
• 15:42
  SPEAKER_01: But Chris, I want to make one other point here is that this was back in a time when both the basin was forming, so we make this shallow depression, but also relative sea level was higher.
• 15:53
  SPEAKER_01: The total sea level was higher, and most of the flat interiors of continents were kind of flooded or flooding.
• 15:58
  SPEAKER_01: And we've talked about this in our audiobook series with the Grand Canyon and the Grand Tetons.
• 16:04
  SPEAKER_01: We certainly talked about these kind of western interior seaways or these flooding of the continents by the invading seas, and sea level was a couple hundred meters higher back then.
• 16:13
  SPEAKER_01: So we're dealing with two things both sea level higher, and we're forming these depressions, which then once you have a depression, you start to fill it up with sediment.
• 16:20
  SPEAKER_01: And that I think leads into the next step here.
• 16:22
  SPEAKER_01: Once you have sediment dumping into a basin, that's extra weight.
• 16:26
  SPEAKER_01: That's a lot of weight.
• 16:27
  SPEAKER_01: Like imagine a blanket of sand, a huge area the size of Michigan.
• 16:31
  SPEAKER_01: That's a lot of weight on the crust.
• 16:33
  SPEAKER_01: And so I think this brings I really love this phrase, this self-fulfilling prophecy.
• 16:38
  SPEAKER_01: Can you explain that?
• 16:39
  SPEAKER_01: Because I think we're at that stage now, right?
• 16:42
  SPEAKER_00: Yeah, I I think I want to talk about that self-fulfilling prophecy maybe in terms of let's say the Mississippi Delta.
• 16:47
  SPEAKER_00: Right.
• 16:48
  SPEAKER_00: Right?
• 16:48
  SPEAKER_00: You have this really expansive depositional plane, and you think about well, how can it just keep on depositing sediment at this one place?
• 16:58
  SPEAKER_00: Well, the weight of the sediment causes the delta to sink, which allows for more sediment to be deposited, which then sinks and so on and so on and so on.
• 17:07
  SPEAKER_00: But that's happening.
• 17:08
  SPEAKER_00: We've talked about this in prior episodes.
• 17:10
  SPEAKER_00: You've used that analogy.
• 17:12
  SPEAKER_00: Well, think about this, but except on a actually a much broader, bigger scale.
• 17:18
  SPEAKER_00: This is more deposition.
• 17:19
  SPEAKER_00: I mean, it's the self-fulfilling prophecy is the basin's created, shallow sea invades, deposition happens, and that causes the basin to sink further into a deeper saucepan, which allows for more deposition to occur.
• 17:34
  SPEAKER_01: Exactly.
• 17:34
  SPEAKER_01: That last point is such a cool phenomenon that you dump sediment somewhere, it weighs down the crust, it causes the crust to sink down, which then gives you more space to dump more sediment.
• 17:46
  SPEAKER_01: So this is this kind of sinking and basin-filling process on Earth that occurs in sedimentary basins.
• 17:54
  SPEAKER_00: That's right.
• 17:55
  SPEAKER_00: I mean, if you think about the layering of the earth, the way that we earth is layered, that kind of soft, plasticky asthenosphere below the lithosphere, that cold, crunchy shell.
• 18:06
  SPEAKER_00: If you put tremendous weight on top of that lithosphere, it can just kind of smush and squish down into.
• 18:14
  SPEAKER_00: If Earth were rigid and brittle from the center to the outside, this would be a much more difficult process to explain then.
• 18:21
  SPEAKER_01: Yeah.
• 18:21
  SPEAKER_01: No, that's exactly right, Chris.
• 18:23
  SPEAKER_01: Exactly.
• 18:23
  SPEAKER_01: And so there's a couple of really important things that come out of this.
• 18:27
  SPEAKER_01: I mean, the self-fulfilling prophecy.
• 18:29
  SPEAKER_01: One of the relevant economically relevant things about the Michigan basin in particular is there's a lot of salt or a lot of evaporites, a lot of gypsum deposited.
• 18:37
  SPEAKER_01: I remember going into gypsum mines, I think it was like a middle school field trip or something like that at some state.
• 18:44
  SPEAKER_01: Like I remember doing it quite young.
• 18:46
  SPEAKER_01: I mean, I don't know if they still do this here.
• 18:48
  SPEAKER_00: Okay, well, I I think I might have taken you down there, Jesse.
• 18:51
  SPEAKER_01: I used to take you did too.
• 18:52
  SPEAKER_01: I I definitely remember that too.
• 18:54
  SPEAKER_01: I I I I have some memory of going earlier than that too.
• 18:57
  SPEAKER_01: Um, but they're a made do you still do this this year?
• 18:59
  SPEAKER_00: No, they don't allow anybody down there anymore.
• 19:01
  SPEAKER_00: Um, really?
• 19:02
  SPEAKER_01: Are the mines closed then?
• 19:03
  SPEAKER_00: Or the mines are closed.
• 19:05
  SPEAKER_00: Well, kind of.
• 19:06
  SPEAKER_00: Uh they use it for storage.
• 19:07
  SPEAKER_00: Oh and so things that need to be kept at constant temperatures, consistent temperatures, so they store things for companies down in the mines now.
• 19:16
  SPEAKER_00: And so there was just a liability thing, you know.
• 19:18
  SPEAKER_00: If you've got obviously students walking in and around all these rooms, there's opportunities for theft and security issues and things like that.
• 19:26
  SPEAKER_00: So they completely shut it off.
• 19:28
  SPEAKER_00: Even universities can't get down there anymore.
• 19:30
  SPEAKER_01: Really?
• 19:30
  SPEAKER_01: Oh, that's too bad.
• 19:31
  SPEAKER_01: I mean, so there's these evaporite deposits in the Michigan Basin, and actually they they extend all the way over into the Appalachian Basin, which is a very similar kind of environment towards where I'm in western Pennsylvania, or I'm in central Pennsylvania.
• 19:43
  SPEAKER_01: So the salts and the evaporates don't quite make it to central PA, but in Western PA, there's there's a huge salt and an evaporite and gypsum blanket in the layering, um, you know, in the sedimentary sequence that's really economically been very important for a long time.
• 19:58
  SPEAKER_01: Michigan has always kind of been, you know, number one or two in salt producing states uh because of this.
• 20:04
  SPEAKER_00: Yeah, I mean, down in the gypsum mines, um, I remember going down there because you have this interbedded gypsum, massive layers of it, 15 feet thick layers of gypsum, and then on top of that will be these discontinuous layers of shale, and then maybe dolostone and some limestone, then back to gypsum.
• 20:20
  SPEAKER_00: Well, in the shale layers, you can pick out these chunks of shale that are loaded with coprolites, which is just fossilized shark poop, which again speaks to their fossils and and so the environment, yeah.
• 20:33
  SPEAKER_01: Exactly.
• 20:34
  SPEAKER_01: Yes.
• 20:34
  SPEAKER_01: And so, you know, what was going on here to make this changes is the basin, we've got this basin, and you can think of if ocean levels really high, then the basin is just a shallow depression on the bottom of the sea floor where more sediment is going into its sort of topography on the bottom of this ocean floor, this shallow ocean floor.
• 20:52
  SPEAKER_01: If you drop sea level a little bit, then the areas around the basin will get close to the surface and will restrict flow.
• 21:00
  SPEAKER_01: So the Michigan basin would then be kind of restricted or cordoned off from the rest of the ocean.
• 21:07
  SPEAKER_01: And so therefore it becomes this restricted basin where you have a lot of evaporation, and the only way for water to get out is to evaporate, and so then you build up the salts such that they deposit at the bottom of it.
• 21:17
  SPEAKER_01: So that's why the Michigan basin in particular is one that it got isolated quicker than other ones, so you have more salt formation here.
• 21:24
  SPEAKER_00: That's right.
• 21:24
  SPEAKER_00: And let's think about that a second.
• 21:26
  SPEAKER_00: Why would the Michigan basin be a ripe area to form a restricted basin?
• 21:31
  SPEAKER_00: Well, think about the deepening of the saucepan, the deepening of that basin.
• 21:36
  SPEAKER_00: The more deposition that you get, the more it sinks, right?
• 21:39
  SPEAKER_00: Does that make sense, Jesse?
• 21:40
  SPEAKER_00: It's kind of intuitive that that's going to isolate this whole area from the rest of the open ocean.
• 21:46
  SPEAKER_01: We can kind of envision this too by looking at the distribution of on the map view of North America, where are old rocks exposed, right?
• 21:55
  SPEAKER_01: Where are old crystalline, where's the core exposed, the core of the continent?
• 21:59
  SPEAKER_01: Well, uh Up in the Canadian Shield, obviously, which in Michigan is right next door.
• 22:03
  SPEAKER_01: You go across Lake Huron and you're in it.
• 22:05
  SPEAKER_01: You go across Lake Superior, you're in it.
• 22:06
  SPEAKER_01: Old stuff exposed there.
• 22:08
  SPEAKER_01: You also head over to the east, the Appalachians, where we are, there's old crystalline stuff exposed there too.
• 22:14
  SPEAKER_01: So Michigan's kind of tucked up in this corner where there used to be mountain belts.
• 22:18
  SPEAKER_01: And so it was very far.
• 22:20
  SPEAKER_01: The open ocean connection was either way up in the Arctic or way down in the Gulf of Mexico.
• 22:24
  SPEAKER_01: So it's kind of tucked up in these mountain ranges.
• 22:27
  SPEAKER_01: It used to be tucked up into these highland areas where it was easy to get restricted.
• 22:32
  SPEAKER_01: As soon as you drop sea level, the little there's a little arch in between the Michigan Basin and like the Illinois Basin.
• 22:37
  SPEAKER_01: We'll talk about that in a little bit.
• 22:38
  SPEAKER_01: But that arch would kind of get close to sea level, and Michigan Basin would be restricted.
• 22:42
  SPEAKER_01: Same with the Appalachian Basin.
• 22:43
  SPEAKER_01: So there's more salty kind of stuff there.
• 22:45
  SPEAKER_00: And exactly to come back to you know the importance of the restricted basin, whenever you have that geologically, you have salt water and it's restricted.
• 22:53
  SPEAKER_00: That just means you don't get fresh flow in and out anymore.
• 22:56
  SPEAKER_00: It's restricted from that.
• 22:58
  SPEAKER_00: And that leads to increased salinity of the water, which then leads to evaporate deposition, salt beds and gypsum beds and other associated deposits.
• 23:07
  SPEAKER_01: This self-fulfilling prophecy, man, I love that phrase.
• 23:09
  SPEAKER_01: I'm definitely stealing that, Chris.
• 23:11
  SPEAKER_01: Uh, the the self-fulfilling prophecy here is continuing on.
• 23:15
  SPEAKER_01: It continues on at your restricted basin, and then it goes to more open oceans.
• 23:19
  SPEAKER_01: We get different rock types, different layers.
• 23:21
  SPEAKER_01: Some of them are very similar to other layers in different basins nearby.
• 23:26
  SPEAKER_01: But basically, this happens and you deposit, as we said before, thousands of feet.
• 23:30
  SPEAKER_01: I mean 16,000 feet of sediment beneath the surface today.
• 23:34
  SPEAKER_01: And that doesn't include what's been eroded by the glaciers that went through.
• 23:38
  SPEAKER_01: So is that kind of it?
• 23:40
  SPEAKER_01: I mean, what else is there to this Michigan basin story?
• 23:43
  SPEAKER_01: We have this thing filling up with sediment, and the layers are thicker in the middle and thinner on the edges, and and and that's it.
• 23:48
  SPEAKER_00: Well, no, I think we have to come back to what we originally said, let's put a pin in it, is why is it important to you that it's thicker in the in the middle and thinner on the edges?
• 23:59
  SPEAKER_00: And we also have to come back to how did this tectonic process, the tectonic subsidence, begin?
• 24:06
  SPEAKER_00: That's what we have to come back to, I think, to tie the story up, right?
• 24:09
  SPEAKER_01: Yeah, I think so.
• 24:10
  SPEAKER_01: And this is why it's important to distinguish from the outset.
• 24:14
  SPEAKER_01: We kind of distinguished between the sort of structural dome and basin, like you've got a flat layer of sediments, you've got a uh a stack of paper, and it's flat and it's homogenous all the way across, and then you bend it, and then you get a dome and basin.
• 24:26
  SPEAKER_01: That's a structural dome and basin, right?
• 24:28
  SPEAKER_01: That's something we've talked about.
• 24:30
  SPEAKER_01: That's not this, this is different.
• 24:32
  SPEAKER_01: And the reason it's different is because the sediments are not homogenous all the way across, they're thinner on the edges and thicker in the middle.
• 24:38
  SPEAKER_01: What does that tell us?
• 24:39
  SPEAKER_01: Well, if you have one layer on the edge that's very thin, and in the middle, it's super thick and it's 16,000 feet beneath our feet, and that that plays out over all of the sedimentary layers.
• 24:51
  SPEAKER_01: All of them look like that.
• 24:53
  SPEAKER_01: I mean, it's the same layer.
• 24:54
  SPEAKER_01: So you have layer one that's thin on the edges and thick down below.
• 24:57
  SPEAKER_01: You have layer two that's thin on the edges and thick down low.
• 25:01
  SPEAKER_01: That tells us something really important, I think, Chris, that the boundary between layer one and two, that's the same time.
• 25:07
  SPEAKER_01: That happened, like that change happened at the same time in Earth history.
• 25:12
  SPEAKER_01: And so the fact that it's thinner up on the edges means that there was a slower deposition rate.
• 25:17
  SPEAKER_01: The fact that it's thicker down the bottom means there's a faster deposition rate.
• 25:21
  SPEAKER_01: And that used to be kind of flat, more or less, right?
• 25:25
  SPEAKER_01: But now there's like this big dip in it.
• 25:27
  SPEAKER_01: Um, this is hard to describe without an image, but we have this kind of draping of sediments onto each other, and the thicker part, the reason it's thicker in the middle is because there was active subsidence.
• 25:39
  SPEAKER_01: This was actively dropping down while the sediments were being dumped into the basin, whereas the rim parts were not subsiding nearly as much.
• 25:49
  SPEAKER_01: And so it points to this active process.
• 25:52
  SPEAKER_01: That's one of the main that's part one, I think.
• 25:54
  SPEAKER_00: The heavier the the heavier the sediment, the more sinking you get, the more subsidence you get.
• 25:58
  SPEAKER_00: And uh also, Jesse, you know, we haven't really said the term, but it's we've used this a lot.
• 26:02
  SPEAKER_00: We're talking about isostasy.
• 26:04
  SPEAKER_00: You know, we use this all the time in mountains where tall mountains have deep, deep, deep roots.
• 26:11
  SPEAKER_00: That's how these like really old basement rocks eventually get exposed in the core of the mountains, is by swiping away the top, and you know, the Earth's mantle responds by pushing up, and these these really deep-seated rocks get closer and closer and closer to the surface.
• 26:28
  SPEAKER_00: This is that in reverse.
• 26:31
  SPEAKER_01: It's exactly right.
• 26:32
  SPEAKER_01: It's it's in reverse and it's on a little bit of a smaller scale.
• 26:35
  SPEAKER_01: And I think I want to use a thought exercise to describe this because if you look at a map, if you just Google sedimentary basins in North America, it'll show you there's a ton of basins.
• 26:47
  SPEAKER_01: There's the Michigan basin, which we're talking about, there's the Appalachian Basin, which kind of runs on the west side of the Appalachians, there's the Illinois basin, there's all sorts of basins out west, lots of little ones distributed around.
• 26:57
  SPEAKER_01: There are all sorts of different basins.
• 26:59
  SPEAKER_00: Can I interrupt you a second, Jess?
• 27:00
  SPEAKER_00: Just real quick.
• 27:01
  SPEAKER_00: You know, we in some of our audio books, the Tetons and Yellowstone and so on, have talked about the Cretaceous Interior Seaway.
• 27:09
  SPEAKER_00: That basin that went from Mexico all the way up into Canada was created in large part by the severe erogeny, that uplift that shed sediment off into the interior parts of North America, creating that down warping.
• 27:24
  SPEAKER_00: It's the same exact thing, which made room for the Cretaceous Interior Seaway.
• 27:28
  SPEAKER_00: That down warping, the weight of the sediment made it.
• 27:31
  SPEAKER_01: And so I I I want to let's just do like a little thought exercise here, Chris.
• 27:34
  SPEAKER_01: And I think this'll this will say because there are tectonics.
• 27:37
  SPEAKER_01: Tectonics can control this.
• 27:38
  SPEAKER_01: So you can have extension, normal faulting, and one part of the crust drops down and that creates a basin.
• 27:44
  SPEAKER_01: Okay, that's a very clear way to create that.
• 27:47
  SPEAKER_01: I think that's pretty simple to understand.
• 27:49
  SPEAKER_01: The other one's a little bit more complicated.
• 27:50
  SPEAKER_01: That the sort of controlled kind of tech by tectonics, but it can also be controlled by lithospheric structure.
• 27:56
  SPEAKER_01: So let's imagine, Chris, we just raise sea level 500 meters instantaneously tomorrow.
• 28:02
  SPEAKER_01: Well, what's gonna happen?
• 28:03
  SPEAKER_01: We're gonna flood the Great Plains, the entire Great Plains.
• 28:06
  SPEAKER_01: We've both driven across Iowa and Nebraska, and you know, no offense to those places, but it's flat, right?
• 28:13
  SPEAKER_01: Like it's very, very flat.
• 28:15
  SPEAKER_01: So if we just flood that and put it under a couple hundred meters of ocean, okay, let's do that.
• 28:20
  SPEAKER_01: We've flooded it.
• 28:21
  SPEAKER_01: This we got this flat area.
• 28:23
  SPEAKER_01: The Rockies are still gonna be above sea level and eroding, and we're taking that sediment and erode it into this, what is now an interior seaway sitting on the continental shelf.
• 28:33
  SPEAKER_01: The sediment's gonna start getting deposited flat down, but we're gonna start these little feedback loops, these little self-fulfilling prophecies.
• 28:40
  SPEAKER_01: Some areas in the Great Plains, that's a huge swath of area that's really flat right now.
• 28:44
  SPEAKER_01: But as you go down in the crust, there's a lot of structures in the crust and a lot of differences in the lithospheric thickness or how buoyant the lithosphere is.
• 28:53
  SPEAKER_01: It's not completely homogenous.
• 28:55
  SPEAKER_01: So some places you're gonna dump sediment and it's gonna resist subsiding because it's just more buoyant there.
• 29:02
  SPEAKER_01: Some places you'll dump sediment and it'll start to subside because it's not actually that buoyant.
• 29:06
  SPEAKER_01: There's differences in buoyancy.
• 29:07
  SPEAKER_01: So some places will start to subside a little bit, which means there's more accommodation space, which means you can put more sediment in there, and then you start this feedback process where you have a basin forming because one part of the continent, the size of like let's say the state of Michigan, might start sinking down a little bit.
• 29:23
  SPEAKER_01: We kind of paint this picture of the continents as being like homogenous, continental across continental lithosphere, but it's really complicated.
• 29:29
  SPEAKER_01: There's a lot of variation as you go across the continents, and that variation leads to buoyancy differences.
• 29:35
  SPEAKER_01: So when you dump sediments on top of it, it'll behave differently across the continent.
• 29:39
  SPEAKER_01: Yes.
• 29:40
  SPEAKER_00: That's a good point.
• 29:41
  SPEAKER_00: So what's the thought experiment here?
• 29:43
  SPEAKER_01: The thought experiment is then, okay, let's say Iowa is more buoyant than Nebraska.
• 29:48
  SPEAKER_01: Well, Nebraska will start to sink down a little bit, which means more sediment will get deposited in that Nebraska area, which will cause it to sink down a little bit more, which will sink down a little bit more.
• 29:58
  SPEAKER_01: And then eventually we're going to have Nebraska covered by a thicker layer of sediment than Iowa is because they're both underwater, both getting sediment, but one of them's in a deeper, a deeper basin now, and is kind of this feedback loop can continue.
• 30:11
  SPEAKER_01: If you do this over and over and over over hundreds of millions of years, you'll end up with a new Nebraska sedimentary basin there, and Iowa will be kind of on the edges with a thinner layer.
• 30:21
  SPEAKER_00: And and it does.
• 30:22
  SPEAKER_00: I I'm sorry, I thought you were gonna ask me a question, and I was prepping myself for a Jesse Remnant question.
• 30:27
  SPEAKER_01: Okay, feed me, feed me the question.
• 30:29
  SPEAKER_01: What question should I ask you?
• 30:30
  SPEAKER_00: Well, no, I thought you were gonna say, okay, Chris, well, let's the the thought experiment.
• 30:34
  SPEAKER_00: To me, like what that implies, I'm gonna ask you a question.
• 30:37
  SPEAKER_00: We're gonna have a thought experiment thing, and it just never came my way, so I was disappointed, Jesse.
• 30:42
  SPEAKER_01: Like, well, I was having a conversation with myself, really, which is more interesting than I like it though.
• 30:47
  SPEAKER_00: I like it because Nebraska becomes a self-fulfilling prophecy.
• 30:51
  SPEAKER_00: Nebraska is less buoyant, and so it sinks first and it sinks fastest, and then more deposition, that's where the deposition's going to be directed, is in that spot.
• 31:02
  SPEAKER_00: So I get what you're saying.
• 31:03
  SPEAKER_00: I'm sorry, I'm just ripping on you because I can.
• 31:04
  SPEAKER_00: Yeah, yeah, yeah.
• 31:06
  SPEAKER_01: You've earned the right absolutely earned the right.
• 31:09
  SPEAKER_01: And you uh referred to like old faults and things like that.
• 31:12
  SPEAKER_01: And as soon as you kind of have these variations in pressure, like you put oceans over the continents, you can reactivate those faults.
• 31:18
  SPEAKER_01: And and I think it just highlights like actually how complicated continents are, they're just not homogenous all the way across them.
• 31:25
  SPEAKER_01: And so when we flood continents, you can create these variations.
• 31:29
  SPEAKER_01: When you flood the ocean basin, you know, oceanic crust is pretty homogeneous all the way along it.
• 31:34
  SPEAKER_01: Continents are not the same.
• 31:35
  SPEAKER_01: So flooding continents and putting sediments on continents is very different than flooding oceans and putting sediments on oceans, I guess.
• 31:41
  SPEAKER_00: So I do have a question for you then.
• 31:43
  SPEAKER_00: In your doctory life, are you saying or have you come across this that Michigan, for whatever reason, was less buoyant than what's around it?
• 31:55
  SPEAKER_01: I'll be honest, I don't know the difference.
• 31:57
  SPEAKER_01: I don't know what what created, let's say, the arch between Michigan and Illinois basins.
• 32:03
  SPEAKER_01: Like I don't know enough about the lithospheric structure or the the tectonics to know that actually.
• 32:10
  SPEAKER_01: I mean, I'm sure there's probably some probably some of our listeners know better than I do about the detailed sort of sedimentary geology of North America, for instance.
• 32:18
  SPEAKER_01: I mean, this is something that this type of knowledge is deeply entrenched in people who work in oil and gas, they worry about this stuff all the time because they're looking for arches in basements.
• 32:27
  SPEAKER_01: And this is kind of one one thing about you highlighted is the economic importance of these basins.
• 32:33
  SPEAKER_01: They're really important.
• 32:34
  SPEAKER_01: There's oil and gas, there's salts, there's all these very important features that we look for and need as society down in these basins.
• 32:42
  SPEAKER_00: And not to mention aquifers also.
• 32:44
  SPEAKER_00: Oh, yeah, are aquifers, and they're really actually ideal aquifers because of the structure of the rocks, that the warping of them, if you will, it creates the mechanism for artesian aquifers.
• 32:57
  SPEAKER_00: Oh, yeah, okay.
• 32:58
  SPEAKER_01: Explain that.
• 32:58
  SPEAKER_01: Explain that more, Chris.
• 32:59
  SPEAKER_01: How does that can you explain how that works a little more?
• 33:02
  SPEAKER_00: It's the water tower effect.
• 33:03
  SPEAKER_00: You put a bunch of water high up on a hill in a water tower, and people turn their faucets on in their homes, and and the the pressure that you get, the water that comes out, is just simply due to the weight of the water.
• 33:15
  SPEAKER_00: Well, the warping of Michigan's rocks is the same thing.
• 33:18
  SPEAKER_00: You have follow a layer of sandstone, you know, it's it's higher up on the edge of the basin, and it it gets deeper and deeper and deeper down as you go toward the center.
• 33:28
  SPEAKER_00: So if you pop a well down into that sandstone layer that's not near the edge of Michigan, you know, somewhat near the middle of it, let's say, that water in that sandstone is under pressure and it rises up, and that's what the definition of an artesian aquifer is, or an artesian well.
• 33:44
  SPEAKER_01: I think that's a really nice example, Chris.
• 33:46
  SPEAKER_01: So you're saying that water is going in one sandstone layer on the edges, it's getting in, and then that sandstone layer is deeper down in the center of the basin.
• 33:54
  SPEAKER_01: It's also thicker, so there's water pressure coming from the outside in that sandstone layer.
• 33:58
  SPEAKER_00: So There are many places in Michigan, Jesse, that are called cedar springs or harbor springs and things like this, right?
• 34:05
  SPEAKER_00: And that's because we have natural springs all over the place where groundwater is just just bubbling to the surface.
• 34:12
  SPEAKER_00: And uh, there are people in where I live here in Jamestown that that have you know artesian wells that you don't need to pump the water to get it to the surface.
• 34:20
  SPEAKER_00: It's already there, it's under pressure.
• 34:21
  SPEAKER_00: Oh, really?
• 34:23
  SPEAKER_01: So uh you have a well.
• 34:25
  SPEAKER_01: Is your well in till or the source of your water in till or in bedrock?
• 34:30
  SPEAKER_01: My well is in the glacial aquifer, yes.
• 34:33
  SPEAKER_00: Okay, which 124 124 feet mine is.
• 34:38
  SPEAKER_01: Okay.
• 34:38
  SPEAKER_01: Is that the bottom of the glacial till layer then where you are?
• 34:42
  SPEAKER_01: Do you know how deep?
• 34:43
  SPEAKER_01: I don't know, but it better be.
• 34:45
  SPEAKER_01: Okay.
• 34:47
  SPEAKER_00: It better not be at the right at the smack top of it.
• 34:50
  SPEAKER_00: It better it better be at the bottom.
• 34:52
  SPEAKER_01: Yeah, yeah, no kidding.
• 34:52
  SPEAKER_01: Otherwise, I have problems.
• 34:54
  SPEAKER_01: Yeah, so you gotta go at least that deep to get so we uh we have this like till blanket laying on top of Michigan, which I think you know is part of the reason it's super flat, is because the glaciers came and scraped everything off there.
• 35:04
  SPEAKER_01: Um, and and did cut down into these sedimentary basin.
• 35:09
  SPEAKER_01: So Michigan does have this geological bullseye to it uh if you scrape off the till, you know, and look underneath the till, right?
• 35:16
  SPEAKER_01: And it's just very cool, very classic sedimentary basin.
• 35:19
  SPEAKER_01: Very cool.
• 35:20
  SPEAKER_01: I mean, as cool as sediments can be, really, uh in my opinion.
• 35:24
  SPEAKER_00: Well, now here you go, ripping on sediments again.
• 35:26
  SPEAKER_00: We're gonna get more emails.
• 35:27
  SPEAKER_00: You really tick off a lot of people when you start ripping on sediments.
• 35:30
  SPEAKER_00: You've got a lot of soft rock fans out there, Jesse.
• 35:32
  SPEAKER_01: You gotta Oh, there is a good reason for it.
• 35:34
  SPEAKER_01: Um I I don't know, Chris.
• 35:36
  SPEAKER_01: Have you um we've covered a lot of sediment stuff recently, actually.
• 35:40
  SPEAKER_01: Has your love for any particular type of rock changed uh since doing this podcast, gotten bigger or smaller?
• 35:49
  SPEAKER_00: You know, I don't know, Jesse.
• 35:50
  SPEAKER_00: Um I have to say that some of my favorite specimens are ripple marked sandstones that that you and I've collected together.
• 35:59
  SPEAKER_00: That predates our podcast era, you know.
• 36:02
  SPEAKER_00: So a wall, yeah, a lot.
• 36:04
  SPEAKER_00: Yeah, I that's true.
• 36:05
  SPEAKER_00: I I seriously, I love those rocks.
• 36:08
  SPEAKER_00: I love sedimentary structures.
• 36:10
  SPEAKER_00: I love ripples and fossils and trace fossils, and they're just what's your favorite because those are from out west.
• 36:17
  SPEAKER_01: What's your favorite Michigan sedimentary layer?
• 36:20
  SPEAKER_00: My favorite Michigan sedimentary layer.
• 36:23
  SPEAKER_00: I mean layer in the Michigan basin.
• 36:24
  SPEAKER_00: I the diversity of the gypsum that we have is really amazing.
• 36:30
  SPEAKER_00: I mean, we have this pencil gypsum and we've got selenite gypsum, and it's you can get actually beautiful crystals within pockets.
• 36:38
  SPEAKER_00: So I I love the gypsum.
• 36:40
  SPEAKER_00: It's very, very colorful.
• 36:42
  SPEAKER_00: It's it's kind of marbly, if you will.
• 36:44
  SPEAKER_00: You know, it's got these veins of other things that that kind of cut through it.
• 36:48
  SPEAKER_00: And you I think you must have some.
• 36:50
  SPEAKER_00: Maybe it's still in your parents' yard.
• 36:51
  SPEAKER_00: I don't know if I can do a pencil.
• 36:53
  SPEAKER_01: And you know, I think it's one of those things, gypsum does not last long on the surface of the earth.
• 36:58
  SPEAKER_01: And so I have a couple pieces inside that have lasted longer.
• 37:03
  SPEAKER_01: You know, when you leave it outside, it unless you have a monster piece, like you have it crumbles pretty quickly.
• 37:07
  SPEAKER_01: So uh I think when my parents moved, there was some loss of some gypsum because it was a crumbly mess.
• 37:13
  SPEAKER_01: It had sort of just broken apart in place.
• 37:15
  SPEAKER_00: Yeah, so so well put together that it will long outlive me in my yeah.
• 37:21
  SPEAKER_00: I mean, even out it'll outlive your power washing episodes if you don't power wash.
• 37:25
  SPEAKER_00: Yeah, I'm I know what I'm doing.
• 37:27
  SPEAKER_00: I uh you know, I'm I don't go to work on that like I do a you're no rookie.
• 37:30
  SPEAKER_00: Okay.
• 37:31
  SPEAKER_00: Yeah.
• 37:31
  SPEAKER_00: No.
• 37:32
  SPEAKER_00: No Chris's power washing service knows what he's doing.
• 37:36
  SPEAKER_01: So yeah, so of course he does.
• 37:38
  SPEAKER_01: I mean, Chris knows what he's doing about everything.
• 37:40
  SPEAKER_01: Just ask him.
• 37:41
  SPEAKER_01: Yeah, right.
• 37:41
  SPEAKER_00: That's that's true.
• 37:42
  SPEAKER_00: That's pretty much true.
• 37:43
  SPEAKER_00: Yeah.
• 37:44
  SPEAKER_01: Absolutely.
• 37:45
  SPEAKER_01: You know, my favorite, I think, Michigan sediment.
• 37:48
  SPEAKER_01: I don't know if this really counts as part of the Michigan basin, but the the Jacobsville sandstone.
• 37:53
  SPEAKER_01: Oh, yeah, yeah.
• 37:54
  SPEAKER_01: I was just gonna say yeah, yeah, for sure.
• 37:56
  SPEAKER_01: It's so pretty.
• 37:57
  SPEAKER_00: For everybody out there, the Jacobsville sandstone uh um outcrops a lot in the upper peninsula of Michigan, like around Marquette area and so on on the Lake Superior side.
• 38:06
  SPEAKER_00: It's beautiful.
• 38:07
  SPEAKER_00: It it's used as a um as a building block stone, if you will, for like some old buildings in downtown Grand Rapids, and a lot of the the buildings up in Marquette uh in the UP, they're just beautiful.
• 38:18
  SPEAKER_00: It's a this kind of reddish, deep red, various shades of red, sandstone, interbedded with white layers, crisscrossing it.
• 38:26
  SPEAKER_00: It's just it's amazing.
• 38:27
  SPEAKER_00: So yeah, the Jacobsville is amazing.
• 38:29
  SPEAKER_01: Yep, it's just so pretty.
• 38:32
  SPEAKER_01: I I think it's just an amazing, amazing story.
• 38:35
  SPEAKER_01: And the story of the basins, I mean, they're complicated.
• 38:38
  SPEAKER_01: There's tectonics, there's subsidence, there's the combination of the two, there's this feedback loop, and there's self-fulfilling prophecy that you used.
• 38:45
  SPEAKER_01: I mean, it's just basins are complicated.
• 38:48
  SPEAKER_01: Everyone is kind of a little bit different, and you know, I just want to sort of highlight that we're talking about the Michigan basin here, and some of those rules and principles apply to other basins, and some of them don't necessarily, but it gets really complicated, and this is the value of sedimentologists, people who go through it's really an amazing geological story that people go through, look at drill core, look at the rock record, and map it out, and can piece together this story of this really complicated history.
• 39:18
  SPEAKER_01: I mean, Chris, you've you've seen all these images where people draw maps of Michigan through the entire Venerozoic and say, here's where the extent of the sea was at this particular time, and create these beautiful sort of images and movies of these, and it's all coming from the rock record.
• 39:35
  SPEAKER_01: It's kind of amazing that we can piece this stuff together, that you know, sequence stratigraphy can do this work for us and paint this really detailed direction.
• 39:44
  SPEAKER_00: It's amazing to think about how the drilling of wells has broadened our knowledge of what's below, what's beneath our feet, geology underfoot.
• 39:52
  SPEAKER_01: You know, it's so totally it's just it's just so cool.
• 39:55
  SPEAKER_01: And you you can yeah, you can see some of these images.
• 39:58
  SPEAKER_01: They're just like, here's here's how the basin developed, here's where the how deep the depression was back then, and here's how the the basin, the the depression developed through time in a really, really detailed way because drill down in these things and drill wells and drill for oil wells and look for salt layers and things like that.
• 40:16
  SPEAKER_01: Very cool story of basin development.
• 40:19
  SPEAKER_01: And I think something that's not totally well understood, or the how complicated it is is not necessarily obvious right from the outset.
• 40:28
  SPEAKER_01: So it's always good to dive in the weeds a little bit.
• 40:30
  SPEAKER_00: Absolutely.
• 40:31
  SPEAKER_00: Yeah, yeah.
• 40:32
  SPEAKER_01: What do you think, Chris?
• 40:33
  SPEAKER_01: I think that's a wrap, Jess.
• 40:34
  SPEAKER_01: Okay, sounds good.
• 40:35
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• 40:56
  SPEAKER_01: You can basically all the images.
• 40:58
  SPEAKER_01: I mean, I felt like Chris, this this particular episode, it's really hard to do basins without an image.
• 41:03
  SPEAKER_01: I mean, a cross section of a basin would just drive home this point.
• 41:06
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• 41:13
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• 41:19
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