The Michigan Basin
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[00:00:00]
I am recording
Dr. Jesse Reimink: I'm recording there. , the red
light's
Chris Bolhuis: there it is. There it is.
Dr. Jesse Reimink: The red light's on. Chris, You ready to go?
Chris Bolhuis: I'm ready to go. The question is, are you, you always, you just follow my coattails?
Dr. Jesse Reimink: on, Mr. Coattails. I didn't, I [00:00:30] didn't plan this
Chris Bolhuis: are you doing? Oh no!
Yes! Hey, Where's mine? You did not plan this well at all. Where's mine? I
should have a
Dr. Jesse Reimink: not plan this well at all.
Chris Bolhuis: I should have a delivery guy at my door right now, handing off a Planet Geo hat, okay? special delivery from Dr. Jesse Reimink.
Dr. Jesse Reimink: I should. I should. So what do you, uh,
Chris Bolhuis: ha,
Dr. Jesse Reimink: what do you, if I can get this [00:01:00] thing on my head, my head is
abnormally sized. I, I have,
Chris Bolhuis: and you have a. lot of hair, so,
Dr. Jesse Reimink: I have a giant head with a lot of hair. What do you
think?
Chris Bolhuis: I love it,
Dr. Jesse Reimink: Planet, planet, geo trucker hat.
Chris Bolhuis: You got the man bun coming through the, through the little
notch in the back, that's,
Dr. Jesse Reimink: Coming off the back. Yeah, I
Chris Bolhuis: my gosh,
Dr. Jesse Reimink: can wear
it.
Chris Bolhuis: I had no idea this was coming my way. I'm really disappointed though. I should have somebody knocking on my door Right.
now.
Dr. Jesse Reimink: I know, I know you should. It turns out it was going to be expensive to have a white glove delivery service to deliver [00:01:30] you your hat. so yeah, this, uh, Chris, we got merch available. I mean, we're starting small, a hat and a t shirt and uh, but, you know, you can go to our website now, planetgeocast.
com and there's a merch link. people can order this. We'll see how, we'll see how it does. this is a cool hat though, like green trucker hat with a black Planet Geo logo. Pretty good, right?
Chris Bolhuis: I think so. And I like it too because, you know, like the patina on a hat, right?
When the, when the sun starts to fade it and the sweat gets involved, you know?
that's going to [00:02:00] show pretty well. Like I'm going to use that hat. That's going to be a working hat.
Dr. Jesse Reimink: you're gonna, yeah, you're gonna get the sweat stains on it. Yeah. Yeah.
Chris Bolhuis: Yeah,
And I, I. I'm one of those guys, like when I get sweat stains on my hat, I leave them. rarely do I like wash my hats and I don't know.
Is that gross?
Dr. Jesse Reimink: but you're bald. So you get sweat stains probably all over
the hat. Not just that, like the, at the rim, like normal
people do.
Chris Bolhuis: That's true. That's true. and it actually is. yeah, I
love it though. That'll put, that'll put a nice [00:02:30] patina on. Absolutely.
Dr. Jesse Reimink: be good, right? yeah,
Chris Bolhuis: I like the
Dr. Jesse Reimink: There's a there's like a t shirt option and a hat option at the moment, and you know, if people like them. And want some other designs, let us know. We can update them. I've been trying to convince my wife to have the black, it's a black t shirt with a planet geo logo.
And I've been trying to convince her that putting erosion happens on the sleeve would be kind of nice.
You know what you think? Good idea. Yeah. Okay. Well,
we'll, we'll see. We'll see. Anyway,
Chris Bolhuis: I was just thinking about this the other day. Actually, just yesterday, I was walking out I was going to [00:03:00] 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
Dr. Jesse Reimink: yeah,
Chris Bolhuis: and
Dr. Jesse Reimink: yeah, she got, she got this in her head and wanted to do it. So there we go. Yeah. that'd be good. Being aware of this hat. Not too bad. I, I don't, uh, usually like baseball caps. I have too much hair. I've got
too much brain in my head for them
to like really fit well.
Chris Bolhuis: You have too much brain to
contain, don't you, Yes,
Dr. Jesse Reimink: I think that's right.
That's what I've heard. Yeah,
Chris Bolhuis: Yeah, you've heard it as you're looking at yourself in the [00:03:30] mirror.
Dr. Jesse Reimink: so I don't, uh, usually wear baseball hats,
but this
one's pretty good. I
like it.
Chris Bolhuis: I
do, I wear them all the time because I'm bald and I, I have to, really be careful of getting sunburn.
So
Dr. Jesse Reimink: to protect that noggin. Well, okay, there we go. How about that for an intro, Chris?
Chris Bolhuis: I love it. I had no idea this was going on. All of a sudden, you disappeared from, I'm like, what is he doing?
Are you trying to crack your back or what do you have going on there?
Dr. Jesse Reimink: Well, I, so yeah, merch available. There we go. Head to our website. There's other ways to support us too. You can download our mobile app, buy [00:04:00] some audio books, but this is another way. So, you know, and you get some merch out of it. It's kind of cool. Chris today, this is, are you like in a relaxed mode? Are you just like really happy right now?
Cause we're going to talk about like, we're going to talk about Michigan today. And this is home turf. You, You love talking about Michigan
Chris Bolhuis: I do love to talk about Michigan and I'm sitting in Michigan.
right now and
on my Awesome property. And it is a beautiful fall day.
I I love this. Like this is perfect. so 100 percent you have
you have
Dr. Jesse Reimink: [00:04:30] happier.
Chris Bolhuis: of Chris.
Dr. Jesse Reimink: we're gonna think about the rocks, a little bit beneath your feet, all the way down to way beneath your feet. the rocks we're going to talk about are not near me right now in State College, but I'm close to it. If I get up on a ridge, I can see Similar rocks to what we're talking about.
they're over in Western Pennsylvania and then they kind of bridge up to Michigan 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 they're not the easiest to understand.
They're not the most intuitive, what we refer to as sedimentary basins. I [00:05:00] think there's reasons for that, but in part, we talk about different types of basins. In geology. And this one we're talking about sedimentary basins. We're going to focus on the Michigan basin. And this came from a listener question from John. So John, thanks for the great question here about the Michigan basin, but this is home turf. I grew up in Michigan. Chris, you live in Michigan still, you know, teach me, how much do you talk about Michigan geology? I know you do your field trip up to the upper peninsula and you talk about that, but how much, I guess, not Michigan geology, but the Michigan basin.
how much do your students. Learn about the Michigan basin specifically.
Chris Bolhuis: [00:05:30] Um, I talk a lot about it actually. I,
um, because I do. And actually, it's been a long time since you've been down in my neck of the woods on, on my campus there, and
seen my room.
Dr. Jesse Reimink: Yeah, actually Chris. I'm coming to do that. I'm gonna do that What early November
we'll be down
Chris Bolhuis: I can't wait. That's right. Whenever I get like really artistic students, I asked them to do something either take a ceiling tile down from my ceiling and paint a ceiling tile, something
geologic or, or astronomy related, whatever. [00:06:00] And I also have students that have painted murals outside down the hall, down the science hallway there. So I have like five walls. there's garden of the gods. There's a mountain climber, just really talented people that have done
these, these gigantic murals. Right. And one of those walls is of the Michigan basin.
So it's that important to me that I'm like, let's put the Michigan
basin on a wall,
Dr. Jesse Reimink: that's great. That's very cool.
Oh, awesome. Okay. Yeah. I'm excited. I'm excited. to see that in a, in a month or so. That'll be great. So, [00:06:30] the Michigan basin, this is a sedimentary basin, which is different from, it's similar to what we call a structural basin. Like we've talked about basins and domes before, especially the black Hills of South Dakota.
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
Chris Bolhuis: that's, that's right. Domes are so much more intuitive. structural domes,
Dr. Jesse Reimink: structural dumps, but then we can also have structural basins, which are just the opposite of that. You know, it also would make a ring if you tilt the [00:07:00] sediments kind of up on all sides, like a bowl.
cut through that and you, you, kind of have this circular ring shape of the sediments. And there's parts of that, that Michigan has too. 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, but we're also talking about something different.
A bit more fundamental, which is the structure. 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. They're thinner [00:07:30] 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, and as you get towards the center of Michigan, it gets thicker and it's really deep.
The sediments are kind of draped down, and this has to do with how the basin formed. It's not a structural basin, it's a sedimentological basin,
Chris Bolhuis: Ooh, did you just make up a word there? I think you just, sedimentological, is that
Dr. Jesse Reimink: why not? Petrological, sedimentological,
[00:08:00] metamorphicological.
Chris Bolhuis: I don't think it's a word, but nice. It's, it's a good go. I like it.
Dr. Jesse Reimink: Why not take a crack at it? Well, okay, Chris,
I've been blathering out. What do
you, okay. What are your students learn about the Michigan basin? or maybe high level where we're going this episode and then, and then let's get into it.
Chris Bolhuis: when I think about the Michigan Basin, I think about kind of like a self fulfilling prophecy, I guess.
Dr. Jesse Reimink: Oh, that's a nice way to frame it. Yeah. I
like that. Okay.
Chris Bolhuis: you know, it's a really complex history where you have deposition, you have some tectonics involved [00:08:30] 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.
I mean, this was, this was mostly during the paleozoic and to timestamp that it was like 540 ish million years to, about 250 million years ago. So to the tune of. about 300 million years, the basin was being developed when I frame it, I think I just frame it from that standpoint is just one thing led [00:09:00] to another, which then just self fulfilled.
Dr. Jesse Reimink: Yeah.
it's exactly right. just 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, 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.
So it kind of is centered right on the lower peninsula of Michigan. It kind of overlaps into Lake Michigan. And way that people have of Lake Michigan. So the way that we've documented this [00:09:30] is both with drill core and seismically with seismic imaging, we can see where the what's called the crystalline basement, the old rocks the core of the continent, where do those exist and on the edges, they're very near the surface.
And as you go down towards the center of Michigan right kind of in the center of the lower peninsula, it's like 16, 000 feet beneath the surface. 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, we're kind of [00:10:00] 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.
Chris Bolhuis: That's a very good point you look at Michigan from my backyard or, from a hot air balloon, even, and you look down on this, you're not going to see a basin because it's all been filled in with kind of this glacial kitty litter. 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 formed this kind of bullseye pattern around it, where the older, [00:10:30] 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.
work toward the center, so,
but you can't, readily see That,
Dr. Jesse Reimink: exactly right. 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 [00:11:00] sedimentation.
we, you know, you can talk about sea level rise and transgression, regression cycles, you get shale deposited, then limestone, then shale, et cetera. But we kind of think about that as like homogenous over distance. So it's kind of like depositing limestone in a flat blanket on top of seabed.
Um, but actually that, that very rarely ever happens because there's structure on the seabed, especially, back when continents were flooded.
Chris Bolhuis: So Jesse, let's put a pin in that. the really important thing for you. We'll come back to that because I do want to [00:11:30] talk about that further. 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. So I want to make sure that, that you explain further in terms of why that's such an important point to you, but let's instead, first, let's just work through, Because we kind of broke this down into, alright, here's how it started, and
then this is what happened.
and then this is what happened. And when, when we get to that point, then let's come back to why. It's such an important thing to understand [00:12:00] the thickening in the middle and the thinning on the edges. Like why is that geologically an important point?
Dr. Jesse Reimink: okay. So where, I mean, where do we start with this? We've got sort of the first step, the first stage, and again, you, you just have set the stage here temporally. You said Paleozoic on 500 million years to 250 million years ballpark. That's the kind of window we're talking about. What's the first, I mean, do you presumably, when you're talking about this, because you don't go through every sedimentary layer in the basin, do you, or,
Chris Bolhuis: No, no, no, no. [00:12:30] That's, to me, that's not important in term, in the scope of my job. That'd be, you know, later on, maybe a sed strat college class, something like
Dr. Jesse Reimink: Sure. All right. So how do you break it apart here?
Chris Bolhuis: how did the whole thing begin?
Because once it began, that set everything else in motion to, for, what happened in the next 300 million years. And so, we have to go back to a term that you and I talked about in an earlier episodes when we did, what is a craton?
know,
Dr. Jesse Reimink: I love great times.
Chris Bolhuis: love cratons. This is
your thing. You just write, you brightened up right there. So this [00:13:00] began, with the North American craton, Michigan was kind of at the edge of this craton, but this is a really broad, craton.
But then during the Cambrian, so right at the beginning of this, 540 ish million years ago, The region started to subside very slowly and, this created kind of a saucer pan look, and this was a tectonic subsidence,
Dr. Jesse Reimink: yeah, Chris, that, in that part right there, I think that's intimately related to [00:13:30] what, what we want to put a pin in and we'll come back to is how do basins form?
Why is this tectonically subsiding? Like what's going on there? that's kind of related to the, the basin structure again. So let's come back to that and let's move on to the, the second stage here. What is going on? we've got this Precambrian core, the old crystalline metamorphic rocks that are exposed at the surface, this basin is starting, water's involved here because we're dealing with sediments.
And so
what's the next step? Like what's happening
Chris Bolhuis: Well, once [00:14:00] you have this tectonic basin, this kind of saucer pan that's created, then you have the opportunity for water to invade. that's exactly what happened. So we're talking about shallow seas that invaded the area. This goes back to what I let out with this kind of self fulfilling prophecy.
So you have this tectonic basin that then allows for deposition or allows for shallow seas to invade, which then creates deposition, which creates Wait. And that's really kind of [00:14:30] the whole story is when you have deposition, Like we're talking 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.
So that's really kind of where we're at with that stage two, the tectonic subsidence started the whole thing. Shallow seas invaded the area. Now, Jesse, hold on a second? though. How do we know for sure that [00:15:00] this was marine deposition?
What do the rocks tell us?
Dr. Jesse Reimink: 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. So, you know, I think one of the, going to college in Michigan, uh, many field trips do not really get you into metamorphic or igneous rocks.
So we drive around and look at fossils a lot. I
remember going to, I think Alpena has a really nice
fossil outcrop, in the carbonate rocks there. So yeah, you can look at the fossils. You can tell, [00:15:30] okay, this is marine life. these are some reef environment, or this is deep sea or shallow sea or reef systems, you know, so we can really work out.
The details there by looking at both the sediment itself and the fossil record in the sediment. 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 the shallow depression, but also relative sea level was higher. The total sea level was higher, and most of the flat interiors of continents were kind of flooded, or flooding.
And we've talked about this in [00:16:00] our audiobook series, with the Grand Canyon, and the Grand Tetons. We certainly talked about these kind of western interior seaways, or these flooding of the continents, by the invading seas. And, and sea level was a couple hundred meters higher, back then. 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 and that I think leads into the next step here. Once you have sediment dumping into a basin, that's extra weight. a lot of weight. Like imagine a blanket of [00:16:30] sand huge area, the size of Michigan.
That's a lot of weight on the crust. And so I think this brings, I really love this phrase, the self fulfilling prophecy. Can you explain that? Cause I think we're at that stage now,
Chris Bolhuis: Yeah. I think I want to talk about self fulfilling prophecy, maybe in terms of, let's say the Mississippi Delta. Right.
you have this really expansive depositional plane and you think about, well, how can it just keep on depositing sediment at this one place?
Well, the weight of the sediment [00:17:00] causes the Delta to sink, which allows for more sediment to be deposited, then syncs and so on and so on and so on. That's happening. We've talked about this in prior episodes. You've used that analogy. Well, think about this except on a, Actually a much broader, bigger scale.
This is more deposition. 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 [00:17:30] deeper saucepan, which allows
for more deposition to occur.
Dr. Jesse Reimink: exactly. 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. So this is this kind of sinking and basin filling process on earth that occurs in sedimentary basins.
Chris Bolhuis: That's right. I mean, if you think about the layering of the earth, the way that earth is layered, [00:18:00] that kind of soft plasticky asthenosphere below the lithosphere, that, cold crunchy shell,
if you put tremendous weight on top of that lithosphere, it can just kind of smush and squish down into, if earth were rigid and brittle from the center to the outside.
This would be a much more difficult process to explain then.
Dr. Jesse Reimink: Yeah. No, that's Exactly. right,
Chris. Exactly. And so there's a couple of really important things that come out of this. I mean, the self fulfilling prophecy, [00:18:30] one of the relevant economically relevant things about the Michigan basin in particular is there's a lot of salt or a lot
of evaporates, a lot of gypsum deposited.
I remember going into gypsum mines. I think it was like a middle school field trip or something like that at some state. Like I remember doing it Quite young. I mean, I don't know if they
Chris Bolhuis: Oh, really? Okay. Well, I I think I might have taken you down there.
Jesse. I used to take
Dr. Jesse Reimink: you, did too. I definitely remember that too. I, I, I have some memory of going
earlier than that too.
Um, but there may, do you still do this, this
field
Chris Bolhuis: they don't [00:19:00] allow anybody down there anymore
Dr. Jesse Reimink: Oh, really?
Chris Bolhuis: they
Dr. Jesse Reimink: closed then?
Chris Bolhuis: The mines are closed. Well, kind of. They use it for storage. And, and so, things that need to be kept at constant, Temperatures, consistent temperatures. so they store things for companies down in the mines. now.
And so there was just a liability thing. You know, 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. So they completely shut it off. Even universities can't get down there [00:19:30] anymore.
Dr. Jesse Reimink: Really? Oh, that's too bad. 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.
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. Michigan has always kind of been, you know, [00:20:00] number one or two in salt producing
states, uh, because of this.
Chris Bolhuis: 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 layers of shale and then maybe dolostone and some limestone, then back to gypsum. Well, in the shale layers, you can pick out chunks of shale that are loaded with, coprolites.
which is just,
fossilized shark poop.
which
[00:20:30] again speaks to, they're fossils. And and
Dr. Jesse Reimink: The environment, yeah.
Chris Bolhuis: Yes.
Dr. Jesse Reimink: you know, what was going on here to make these 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 seafloor where more sediment is going into, it's sort of topography on the bottom of of this ocean floor, this shallow ocean floor.
If you drop sea level a little bit, then the areas around the basin will get close to the surface and will restrict [00:21:00] flow. So the Michigan basin would then be kind of, restricted or, cordoned off from the rest of the ocean, 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.
So that's why the Michigan Basin in particular is one that it got isolated quicker than other ones
so you have more
Chris Bolhuis: that's right. That's right. And let's think about that a second. why would the Michigan Basin be a ripe area to [00:21:30] form a restricted basin? We'll think about the deepening of the sauce pan, the deepening of that basin,
the more deposition that you get, the more it sinks.
right. Does that make sense, Jesse? It's kind of intuitive that that's going to isolate this whole area from the rest of the open ocean.
Dr. Jesse Reimink: 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? where are old crystalline, where's the core exposed? The core of the continent? Well, [00:22:00] up in the Canadian Shield, obviously, which in Michigan is right next door.
You go across Lake Huron and you're in it. You go across Lake Superior, you're in it. Old stuff exposed there. You also head over to the east, the Appalachians, where we are. There's old crystalline stuff exposed there too. So Michigan's kind of tucked up in this corner where there used to be mountain belts and so it was very far.
The open ocean connection was either way up in the Arctic or way down in the Gulf of Mexico. So it's kind of tucked up in these mountain ranges. It used to be tucked up into these highland [00:22:30] areas where it was easy to get restricted. As soon as you drop sea level, the little There's a little arch in between the Michigan Basin and like the Illinois Basin.
We'll talk about that in a little bit. But that arch would kind of get close to sea level and Michigan Basin would be restricted. Same with
the Appalachian Basin. So there's more salty kind of stuff there.
Chris Bolhuis: And exactly To come back to, you know, the importance of the restricted basin. Whenever you have that geologically, you have saltwater and it's restricted. That just means. You don't get fresh flow in and out anymore. It's restricted from that And that leads to [00:23:00] increase salinity of the water, which then leads to evaporate deposition, salt beds and gypsum beds and other associated deposits.
Dr. Jesse Reimink: this self fulfilling prophecy, man, I love that phrase, I'm definitely stealing that, Chris, uh, the, the self fulfilling prophecy here is continuing on, it continues on, it, you know, restricted basin, and, then it goes to more open oceans, we get different rock types, different layers, some of them are you know, are very similar to other layers in different basins nearby, but basically this happens and you deposit, as we said before, thousands [00:23:30] of feet, I mean, 16, 000 feet of sediment beneath the surface today, And that doesn't
include what's been eroded by the glaciers that went through, so is that kind of it?
I mean, what else is there to this Michigan Basin story? 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?
Chris Bolhuis: 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. And we [00:24:00] also have to come back to how did this tectonic process, the tectonic subsidence begin?
That's what we have to come back to.
I think to tie the story up, right?
Dr. Jesse Reimink: yeah, I think so, and this is why it's important to distinguish, from the outset, we kind of distinguish between the sort of structural dome and basin, like you've got a flat layer of sediments, you've got a, 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.
that's a structural dome and basin, right? That's something we've talked [00:24:30] about. that's not this, this is different. 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. What does that tell us?
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 plays out over all of the sedimentary layers. All of them look like that. I mean, it's the same layer so you have layer 1 that's thin on the edges and thick down below.
You have layer 2 that's thin on the edges and [00:25:00] thick down low. That tells us something really important, I think, Chris, that the boundary between layer 1 and 2, That's the same time. That happened, like, that change happened at the same time in Earth history. And so the fact that it's thinner up on the edges means that there was a slower deposition rate. the fact that it's thicker down the bottom means there's a faster deposition rate. And that used to be kind of more or less, right? But now, now there's like this big dip in it. Um, this is hard to describe without an [00:25:30] image. but we have This kind of draping of sediments onto each other in the thicker part.
The reason it's thicker in the middle is because there was active subsidence. This was actively dropping down while the sediments were being into the basin. Whereas the rim parts were not subsiding nearly as much.
and so it points to this active process. that's one of the
Chris Bolhuis: Okay. The heavier, the, the heavier the sediment, the more sinking you get, the more subsidence you get.
And also [00:26:00] Jesse, you know, we haven't really said the term, but it's, we've used this a lot. We're talking about isostasy.
You know, we use this all the time in mountains where tall mountains have deep, deep, deep roots. 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, 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. This is that. [00:26:30] in reverse.
Dr. Jesse Reimink: it's exactly right. It's, it's in reverse and it's on a, little bit of a smaller scale. 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. 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. There,
there are all sorts of different basins.
Chris Bolhuis: Can I interrupt you a
[00:27:00] second, Jess? Just, real quick. You know, we, in some of our audio books, the Tetons and, and Yellowstone and so on have talked about the Cretaceous interior seaway, that basin that went from Mexico all the way up into Canada was created in large part by the severe orogeny, that uplift that shed sediment off into the interior parts of North America, creating that down warping.
It's the same exact thing, made room for the Cretaceous interior seaway, that
down warping the weight of [00:27:30] the sediment made it.
Dr. Jesse Reimink: And so I want to, let's just do like a little thought exercise here, Chris, and I think this will, this will say, because there are tectonics, tectonics can control this. So you can have extension, normal faulting, and one part of the crust drops down and that creates a basin. Okay, that's, a very clear way to create that.
I think that's pretty simple to understand. The other one's a little bit more complicated that the sort of, controlled kind of tech by tectonics, but it can also be controlled by lithospheric structure. So let's imagine, Chris, we just raise sea level 500 [00:28:00] meters instantaneously,
tomorrow.
Well, what's going to happen? We're going to flood the Great Plains. the entire Great Plains. we've both driven across Iowa and Nebraska and you know, no offense to those places, but it's flat ,
right? Like it's very, very flat. So if we just flood that and put it under a couple hundred meters of, of ocean, okay, let's do that. We flooded it, this, we got this flat area, the Rockies are still going to be above sea level and eroding, and we're taking that sediment and erode it into this, [00:28:30] what is now an interior seaway sitting on the continental shelf. The sediment's going to start getting deposited flat down, but we're going to start these little feedback loops, these little self
fulfilling prophecies, some areas in the Great Plains, that's a huge swath of area that's really flat right now. 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.
It's not completely homogenous. So some places you're going to dump sediment and it's going to resist [00:29:00] Subsiding because it's just more, buoyant there. Some places you'll dump sediment and it'll start to subside because it's not actually that buoyant. There's differences in buoyancy.
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.
We kind of paint this picture of the continents as being like homogenous, continental crust, continental lithosphere, but it's really complicated. There's a lot of [00:29:30] variation as you go across the continents and that variation leads to buoyancy differences. So when you dump sediments on top of it, it'll behave differently across the
continent.
And so
Chris Bolhuis: So what's The thought experiment here?
Dr. Jesse Reimink: the thought experiment is then, okay, let's say Iowa is more buoyant than Nebraska. 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. And then eventually we're going to have [00:30:00] 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. 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.
Chris Bolhuis: and, and it does.
I, I'm sorry. I thought you were going to ask me a question and I was prepping myself for a Jesse Reimink question.
Dr. Jesse Reimink: feed me, feed me the question. What question should I [00:30:30] ask you?
Chris Bolhuis: no, I thought you were going to say, okay, Chris, well, let's, look the thought experiment. To me, like, what that implies, I'm going to ask you?
a question.
We're going to have a
thought experiment. thing. And it just never came my way, so I was disappointed, Jesse.
Like
you
just,
Dr. Jesse Reimink: with myself, really, which
Chris Bolhuis: You were, I like it though. I like it because Nebraska becomes a self fulfilling prophecy.
Nebraska is, less buoyant, and so it sinks first, and it sinks fastest. And then more deposition. That's where the deposition is [00:31:00] going to be directed is in that spot. So I get what you're saying. I'm sorry. I'm just ripping on you. Cause I can
Dr. Jesse Reimink: yeah, yeah, of course, yeah, it's because it's your right.
You've
earned the right, absolutely earned the right. And, you, uh, referred to, like, old faults and things like that, and
as soon as you kind of have these variations in pressure, like you put oceans over the continents, you can reactivate those faults, and, and I think it just highlights, like, actually how complicated continents are.
they're just not homogenous all the way across them, and so when we flood continents, You can create these variations when you flood [00:31:30] the ocean basin, you know, oceanic crust is pretty homogenous all the way along it. Continents are not the same. So flooding continents and putting sediments on continents is very different than flooding
oceans and putting sediments on oceans, I
Chris Bolhuis: So I do have a question for you then in, in, in your doctory, life, are you saying, or have you come across this, that, that Michigan for whatever reason was less buoyant than what's around it?
Dr. Jesse Reimink: I'll be honest, I don't know the difference. I don't know what, what created. [00:32:00] Let's say the arch between Michigan and Illinois basins. Like I don't know enough about the lithospheric structure or the, the tectonics to know that actually, 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. 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 and basements. And this is kind of one, one thing about
[00:32:30] you highlighted is the economic importance of these basins.
They're really important. 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
Chris Bolhuis: And not to mention, aquifers also.
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.
where these,
Dr. Jesse Reimink: Explain that Explain that more, Chris. How [00:33:00] does that, can you
Chris Bolhuis: well,
Michigan, it's the water tower effect. put a bunch of water high up on a hill in a water tower, and people turn their faucets on in their homes, and the pressure that you get, the water that comes out, is just simply due to the weight of the water.
Well, the warping of Michigan's rocks is the same thing. You have, follow a layer of sandstone, you know, it's higher up on the edge of the basin. And it gets deeper and deeper and deeper down as you go toward the center. So if you pop a well down into [00:33:30] 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.
Dr. Jesse Reimink: I think that's a really nice example Chris. 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. It's also thicker. So there's water pressure coming from the outside in that sandstone
layer.
So
Chris Bolhuis: There are
many places [00:34:00] in Michigan, Jesse, that are called. Cedar Springs or Harbor
Springs and things like this, right? And that's because we have natural springs all over the place where groundwaters just, just bubble into the surface.
And there are people in where I live here in Jamestown that that have, know, artesian wells that you don't need to pump the water to get it to the surface. It's already there. It's under pressure.
Dr. Jesse Reimink: Oh, really? Okay. So, uh, you have a well. is your well in till or the source of your water in till or in [00:34:30] bedrock?
Chris Bolhuis: My well is in the glacial aquifer. Yes.
Dr. Jesse Reimink: Okay. Which sits
Chris Bolhuis: 124 feet. Mine is.
Dr. Jesse Reimink: Okay. is that the bottom of the glacial till layer then where you are? Do you know how
Chris Bolhuis: I don't, but it better be. it
better, it better not be at the, right at the smack top of it. but
Dr. Jesse Reimink: Yeah. Yeah. Yeah. Yeah. No kidding.
Yeah. See. Yeah. so you got to go
at least that deep to get, so yeah, we have this like Till blanket laying on top of [00:35:00] Michigan, which I think, you know, is part of the reason it's super flat. It's because the glaciers came and scraped everything off there. Um, and, and did cut down into these, sedimentary basin, so Michigan does have this geological bullseye to it. Uh, if you scrape
off the till, you know, and look underneath the till, right. And it's just very cool, very classic,
sedimentary
basin. very cool.
I mean, as cool as sediments can be, really, in my opinion.
Chris Bolhuis: Well, now here you go, ripping on sediments again.
We're gonna get more emails. You
Dr. Jesse Reimink: I know, I
Chris Bolhuis: when you start ripping on [00:35:30] sediments. We got a
Dr. Jesse Reimink: I know, but it is
cool. Oh, there is, and there's good reason for it. And I don't know, Chris, have you, um, We've covered a lot of sediment stuff recently, actually.
has your love for any particular type of rock changed since doing this podcast? Gotten bigger or
Chris Bolhuis: You know, I don't know, Jesse. Um, I have to say that some of my favorite specimens are ripple marked sandstones that, that you and I've collected [00:36:00] together. that predates our podcast era, you know? So,
Dr. Jesse Reimink: a lot, yeah, a lot,
Chris Bolhuis: Yeah, I, I, I, seriously, I love, Those rocks. I, love sedimentary structures. I love
ripples and fossils and trace fossils and, they're
Dr. Jesse Reimink: what's your favorite, cause those are from out west, what's your favorite Michigan sedimentary layer?
Chris Bolhuis: my favorite
Michigan sedimentary layer?
I
mean,
Dr. Jesse Reimink: in the Michigan Basin.
Chris Bolhuis: the diversity of the gypsum that we have is really [00:36:30] amazing. I mean, we have this pencil gypsum and we've got selenite gypsum and it's,
you can get
actually beautiful crystals within pockets, So I love the gypsum. It's very, very colorful.
It's, it's kind of marble y, if you will. You know, it's got these veins of other things that, that kind of cut through it. And you, I think you must have some, maybe it's still in your parents yard. I don't know,
Dr. Jesse Reimink: I do, and you know, I think, It's one of those things, gypsum does not last long on the surface of the earth,
and so I [00:37:00] have a couple pieces inside that have lasted longer, you know, when
you leave it outside it, unless you have a monster piece like you have, it
crumbles pretty quickly, so, uh, I think when my parents moved, there was some loss of some gypsum because
it was a crumbly mess, it
Chris Bolhuis: Now the stuff I
Dr. Jesse Reimink: apart in place,
Chris Bolhuis: yeah, so so well put together that it will long outlive me in my
front yard. So yeah,
no, no
worries.
Dr. Jesse Reimink: outlive your power washing episodes,
you don't power wash that,
Chris Bolhuis: I know what I'm doing. I, you know, I'm, I
don't, go to work on that. like I do.
uh,
Dr. Jesse Reimink: [00:37:30] no rookie. Okay. Yeah. Oh, wow. Yeah. So,
of course he does. I mean, Chris knows what he's doing about everything. Just
ask him.
Right.
Chris Bolhuis: that's true. That's pretty much true. Yeah.
Dr. Jesse Reimink: Absolutely. you know, my favorite, I think Michigan sediment.
I don't know if this really counts as part of Michigan basin, but the Jacobsville sandstone,
Chris Bolhuis: Oh yeah. Yeah. I was just going to say that. Yeah. Yeah. For sure.
Dr. Jesse Reimink: pretty.
Chris Bolhuis: for everybody out there, the Jacobsville sandstone, um, [00:38:00] outcrops a lot in the upper peninsula of,
Michigan, like around Marquette area and so on on the Lake Superior side. But, yeah, Yeah. It's beautiful. 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 in the UP.
they're just beautiful. It's this kind of reddish deep red, various shades of red sandstone interbedded with white layers crisscrossing it. It's just, it's amazing. So yeah,
Dr. Jesse Reimink: Oh, it's so
pretty.
Chris Bolhuis: is amazing. [00:38:30] Yep.
Dr. Jesse Reimink: it's just so pretty. I think it's just an amazing, amazing,
story. And the story of the basins, I mean, they're complicated. 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.
I mean, it's just, basins are complicated. Everyone is kind of a little bit different. And, you know, I just want to just 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 [00:39:00] 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.
I mean, Chris, you've, you've seen all these images where people draw maps of Michigan through the entire Phanerozoic and say, here's where the extent of the sea was at this particular [00:39:30] time and create these beautiful sort of images and movies of these, and it's all coming from the rock record.
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
Chris Bolhuis: 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, you know,
Dr. Jesse Reimink: Totally. it's, just, it's just so cool. And you can yeah, you can see some of these images. They're just like, here's, here's [00:40:00] 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. 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.
Very cool, story of basin development. And I think
something that's not totally well understood, or the, how complicated it is, is not, necessarily obvious right from the outset. So it's always good to dive in the weeds a little bit. [00:40:30]
Chris Bolhuis: Absolutely.
Dr. Jesse Reimink: what do you think, Chris?
Chris Bolhuis: I think that's a wrap, Jess.
Dr. Jesse Reimink: Okay. Sounds good. Hey, there's a couple ways to support us.
Well, first merch, Planet Geo merch. We got a cat, a hat and a shirt, and maybe some more stuff coming online. Go to planetgeocast. com. There's a merch link there. you can also download our Camp Geo mobile app. It's the first link in your show notes. We really appreciate it. If you did that and left us a rating and review on your app store, we have a lot of free content.
You can. Basically all the images. I mean, I felt like Chris, this, this [00:41:00] particular episode, it's really hard to do basins without an image. I mean, a cross section of a basin would just drive home this point, but we've done stuff like that on our app because we have the ability on our app to show you images along with the audio files.
You can take basically the Intro to Geology course for free there with a bunch of audio books for sale. So head to the Camp Geo app, first link in your show notes, send us an email, planetgeocast at gmail. com. And you can follow us on all the social medias at planetgeocast.
Chris Bolhuis: Cheers. [00:41:30]
