9UNP0768SD_Norlene_Emerson_WordPress 
Norlene Emerson Wisconsin 
Under the Sea 
September 18, 2012 

- Good evening, everyone. I would like to welcome you to UW Richland's Love of Learning Lecture, "Wisconsin Under the Sea: Life in Wisconsin During the Early Paleozoic." Dr. Norlene Emerson is a native of Richland Center and alum of UW Richland. She received her PhD from UW Madison in the field of sedimentary geology. Norlene joined the staff at UW Richland in 2002 where she teaches a variety of introductory to geology courses. Norlene's research interests involve pursuing a better understanding of environmental conditions within the upper Mississippi Valley during the late Ordovician period, which was a time of rapid climate change and the earliest mass extinction on Earth. Please join me in welcoming Dr. Emerson. 
[APPLAUSE]
 
- Thank you, Jessica. And it's great to see so many out tonight. This is a lot of fun for me. So I'm going to talk about what Wisconsin was like a long time ago. 

Much different from what it looks like today. To begin my topic and my lecture, I decided to put that picture, the image of the ocean there because if we could go back to the Ordovician, the early Paleozoic of Wisconsin, that's what we'd see. It was covered with water. It was a very watery world back then. So let me start by explaining a little bit what I mean by the early Paleozoic for those of you who are not geology minded and recognize that. Early Paleozoic, or the Paleozoic, is a unit of geologic time. So, I just have a very simple basic diagram there that shows you the different names of the geologic times. And so Paleozoic lasted from about 500 million years to about 250 million years, to give you some idea The Earth is much older than that, and we have rocks in Wisconsin that are much older than that. We have rocks in Wisconsin that go back to about 2.5 billion years and a little beyond that. So I'm not going back to the earliest rocks in our state but a time that interests me a lot because there's a lot of changes going on on Earth at that time. 

A lot of changes in life forms and the physical world as well. Okay, so the early Paleozoic is the Cambrian and Ordovician time periods. So the Paleozoic we can kind of divide up into the early, middle, and late, and I'm going to talk about the early. I'm not going to talk a lot about the Cambrian because I'm focusing on the life that's preserved as fossils in the rock record, and in Wisconsin during the Cambrian, the water level was so shallow for most of the time or Wisconsin was above the sea level, there's not a lot of great fossils in the Cambrian aged rocks. So I'll talk a little bit about the Cambrian but really going to focus on the Ordovician which holds a lot more fossils. So, let's take a look at the world today, the position of the continents and what we're used to seeing, what looks familiar to us, the shape of North America and where the oceans are, and because of plate tectonics and we live on a very active planet, the continents had not always had that shape or been in the position. So if we go back to the early Paleozoic, the Cambrian and the Ordovician, it's a different world. You don't recognize the same shapes that we see for the continents now. There was a very large land mass that was centered over the South Pole, and you can see in this view it looks a little bigger than it actually was because of the distortion of the map. But the southern continents, Antarctica, South America, Africa, were joined together for one large continent called Gondwana. 

And then in the middle of the map there you've got some smaller continents, and, for the most part, most of the land mass was south of the equator. So I'm putting that red line up there as a reference for the equator. These small land masses, Laurentia, Siberia, Baltica, Siberia you recognize, Baltica is mostly northern Europe now, and Laurentia is what will become North America. So Wisconsin and the rest of North America was in the southern hemisphere during the late Cambrian. If I bring the movie forward a little bit and look at the Ordovician, things are drifting a little bit north, North America, Baltica, and Siberia are drifting a little bit north, but we're still kind of straddling the equator there. Where's Wisconsin in all of that? This red star is marking where Wisconsin was at that time. So we were in tropical conditions. Nice, warm temperatures all the time. We didn't have to shovel snow back then. If we zero in on Laurentia or what will become North America and Wisconsin here for reference, some of that continent was above sea level, but you'll see that a lot of it was flooded. 

Sea level was higher. Climate was a lot different then than it is now. We kind of talk about Earth as going in and out of icehouse conditions and greenhouse conditions, meaning when it's an icehouse condition, there is permanent ice on Earth somewhere, and during greenhouse conditions, there's not permanent ice anywhere. It's warm enough that there are no big glaciers anywhere. So back in the early Paleozoic, this was a time of greenhouse. So, melted glaciers and due to the tectonic activity at the time, sea level was much higher than it is now. And so a lot of North America was flooded, as you can see. I'm going to go through a few more cartoons here and go forward in time. So the late Cambrian there about 500 million years ago. 485 million years ago things are changing a little bit. 

You'll see some land mass on what will be our east coast drifting a little bit closer to Laurentia and will make contact with Laurentia. So the middle Ordovician, the late Ordovician. So Wisconsin, for the most part, remained flooded. But the sea is very shallow. It's not very deep. We'll talk more about that in a little bit. So, the shallow sea flooding North America, sediment was being deposited on that sea floor, and it's preserved in our rock record so we can take a look at the bedrock in our state and interpret those rocks to get a better understanding of what that ocean was like at that time, what the life was like by the fossils that are in those rock layers. So here's a bedrock map of our state of Wisconsin, and in the northern part of the state where the colors are a little bit more vibrant, those are the Precambrian age rocks. Much, much older rocks. And that part of Wisconsin during the early Paleozoic probably remained most of the time above sea level. 

It was dry land. The more subdued colors toward the southern part of the state and where we are in the southwest part, those are all layers of sedimentary rock, sandstones, shales, carbonates, that were deposited on top of that Precambrian rock which is mostly igneous metamorphic rock. And those sedimentary rocks are what I'm interested in, what I take a look at. So, if I look at a road cut or a quarry around here, these are the rocks that I spend time with. So these are sandstones, shales, and carbonates, or, if you're not familiar with carbonates, I'm talking about limestones, dolostones, those kinds of rocks. So you can see in this outcrop toward the bottom of the picture, the rocks are darker in color and they're more shale-rich clay sized particles. As we go up, kind of the middle layers there, it's kind of a combination of carbonate and shale. And toward the top it's more carbonate rich. Well, what that tells me is it tells me something about the water depth and the water clarity and where the shoreline might have been at the time of the sediment being deposited. So I look at those rock layers, I measure those rock layers, I collect samples from those rock layers, and then look at the fossils in those rock layers to get a better understanding of life here back in the Paleozoic. 

If we could go back then and be in Wisconsin, we might have a view something like this. So this is a modern picture that I took during the summer of the California coast, but the sea, as I hope you can see in this picture, is very shallow. You have to walk out into that water for a long way before it reaches your kneecaps or gets any deeper. Standing where I am taking this picture, you see a lot of sand. Back in the Paleozoic, this is what we would have been seeing if we had been standing in Wisconsin and looking, at that time, to the west looking at a sunset, but what now would be to our south which would be looking at Illinois. So from Wisconsin looking down toward Illinois. So all of the life, most of the life and activity is happening in the ocean, not on land. There were some land plants, but they were not very diverse and not very widespread and really small. So if we would turn around from that picture and look at the dry land in Wisconsin, we'd see a little bit of vegetation but not much. Short little one-inch tall, two-inch tall non-vascular plants, all reproducing by spores. 

So no leaves yet, no flowers. Very little happening on land. Occasionally, we'll get a fossil that's evidence of something crawling out of the water and getting out of the water for a while, but most of the activity, most of the life is in the water. So, let's focus on what's going on in the water. The sea that covered Wisconsin was very shallow. And that's kind of a general way of describing it. What do I mean by shallow and very shallow? That's a really good question, and I wish I could quantify that a little bit better and give you some definite numbers, and I can't. It's difficult to know the exact water depth. Because of the abundance of fossils that we find of animals that lived on the sea floor, it had to be shallow enough to be in the photic zone or shallow enough for the light to penetrate all the way to the sea floor. If we look at that cartoon, to the left is looking north, and south is to the right. 

So the sea level, the shoreline would be somewhere out of that little cartoon. So we go from a water depth of zero to maybe, on the right-hand side of that diagram, maybe a water depth of the greatest of a few hundred feet. So we're not talking about the deep ocean. Very shallow. Close to the shoreline we're getting a lot of sediment that's being brought to the ocean by rivers that are flowing down to the ocean. So the types of rocks that we get from that sediment are coarser in texture. Sandstones and some shales breaking down the minerals into clay particles. If we get away from that shoreline and move farther offshore, that's where we're going to find more fossils. A lot of the organisms that live in the water cannot take a lot of sediment in the water. It clogs their digestive system, their respiratory system, and so they live farther offshore. 

So the carbonates, the limestones, the dolostones that we find, we typically interpret those as being created in deeper water a little bit farther away from the shoreline. And rocks that contain a lot more sand and shales are closer to the shoreline where rivers are bringing that sediment down. Okay, so back to this bigger view of Wisconsin and North America, and I've tilted it back into the orientation that it would have had in the late Ordovician where Wisconsin is kind of turned 90 degrees from what we're used to seeing today. So shallow ocean covering most of Wisconsin most of the time. Northern Wisconsin sometimes above sea level. And in this cartoon here, if you look to the south side of Laurentia there, you see a lot of small islands. Well, that's a small continent that was moving northward and collided with Laurentia. So during the Ordovician it had made contact and colliding with North America, and we had a lot of volcanoes erupting. So lots of volcanoes erupting there. Because we were located in the southern hemisphere, kind of in the trade wind's belt, the major wind pattern would have taken the ash that was coming out of those volcanoes, it would have drifted that ash north toward Wisconsin. 

So we're lucky that we have some of those ash deposits from the volcanoes that I have circled there in the rocks in Wisconsin and Illinois and Minnesota and the Midwest here. And that's great in a lot of ways for me because a volcano erupting on a geologic time scale, that's an instant. That's something that happens very quickly. So we can use those ash layers, we can date those ash layers, and get some idea of the timing of the deposits of the rest of the sediment that are underneath and above those ash layers. So during the Ordovician when those volcanoes were erupting, and these were some major eruptions, what we have learned by looking at these ash layers, we probably had some magnitude 9, 8, sized eruptions that are what Discovery Channel and National Geographic may call super volcanoes, like Yellowstone. We probably had eruptions of that size on the order of maybe nine or a little over nine per million year. Nine of those major eruptions within a million years time. Well, what does that mean? If we look at more recent time, the Cenozoic, the super volcano eruptions of Yellowstone and other super volcanoes like that were have eruptions more on the order of 1.4 eruptions per million years. So it was a lot more activity than we have seen in any kind of recent time or more recent time. So what I have on this map colored in the light tan is where we find those ash layers. 

So the volcanoes were erupting kind of where the Carolinas are now. The ash was spreading across the Midwest and the mid-continent and get preserved in the rock layers. Okay, so what am I focusing on? I'm focusing on the area there that's within the red box along that black line that extends from southwest Wisconsin into Minnesota and Iowa. And the reason I chose that stretch is because we see a change in the rock record where the blue kind of design that I have there in the brick pattern, those are carbonate rocks a little bit farther offshore. The green area with the dashes is more shale-rich rocks, and that shale is coming from rivers that are washing off of what is labeled there the Transcontinental Arch or land that is above sea level at the time. So we see a change in the rocks as we go from the blue pattern there to the green pattern, and I'm interested in what organisms are alive at that time and how they're dealing with this change in environment. And so, as far as rock layers go, I'm dealing very specifically with a rock formation called the Decorah formation, and it includes four of those ash layers. Now, those ash layers have changed. They're no longer considered volcanic ash. They've been chemically weathering for hundreds of millions of years, so they're clay layers now. 

But they still contain some crystals of minerals that were in that ash when it erupted, and they're really durable minerals that have not changed for all these millions of years. We think about diamonds being forever. Well, zircons are really forever. 
[LAUGHTER]
 Zircons are a little more durable. So we'll take those zircon mineral grains out of those clay layers, and we can age date those zircons to get some idea of when those volcanoes were erupting. So, I'm lucky that we have some of those ash layers and those zircons available in the rocks that I'm studying. So here's just one example of the shale rich rock that I'm working with in Iowa. Some thin layers of carbonates there interbedded with the shales. There are fossils within some of those shale layers and those carbonate layers, but as I'm digging through all of that material, once in a while I'll find one of those ash layers as that light orange color, pale orange color at the bottom. If I just zoom in a little closer so it's easier for you to see. 

There it is. So it's the sticky clay now, but we can process that and pull out some of those crystals that contain radioisotopes and we can age date those clays. Here is a different location a little bit south of where the last picture was taken near Dickeyville, Wisconsin. We had some major road construction in Wisconsin a few years ago. It exposed some great road cuts. So here we see more carbonate rich rocks. Not quite as shaley. If we zoom in a little bit closer there for a picture of that road cut, those rocks, lots of limestone there but still some amount of shale as well. And those layers contain a lot of fossils. At this particular location we have four of those bentonites or altered volcanic ash layers there, which is great because they're all there at this one location so there's no doubt or question about which ash layer is which. 

And a colleague of mine has age dated those ash layers, so it's wonderful. So here's the result of the age dating of those ash layers or bentonites by a colleague, Brian Sell, and so those numbers, 453.1, 453.33, those are millions of years ago. So we've got some really nice precise dates, and these are new dates. They have just been worked out in the last couple of years here. So we're really excited to have this information. So it's really helpful for me, then, to get some idea of how quickly the animals evolved during that time, the changes that happened in the sea water during that time. We've got some real nice time constraints on those rocks. So, I can use those ash layers to help me interpret what's going on with the life. So here's a diorama that depicts the typical sea floor back in the Ordovician. You'll notice if you look at those organisms, some look a little more familiar than others, and we're lacking fish. 

Fish had evolved by that time, but they're pretty small and clunky and we don't have many fossils of fish. So fish are not very abundant in the sea at that time. So let's look at some of the fossils that get preserved, and as you probably can guess or know that not everything that was alive is going to be fossilized and not everything that becomes a fossil is going to be discovered. And so we just have a little snapshot or glimpse of what the sea floor was like. There were probably a lot more soft-bodied organisms there that just did not get preserved. So the diversity of life back in the Ordovician was probably even greater than we can see in the fossil record. So let's look at some of the examples of that life. If we look in the sediment on the sea floor, we see these kinds of fossils. The little bumps there, nodules and longer tube shapes there are burrows from soft-bodied organisms that were crawling through the mud. Have no idea what the organism looked like, but we have their trail left behind or their burrow. 

Their feeding burrow or maybe their living chamber in the sediment. There are lots of tiny little microscopic organisms, too, that are floating in the water, plankton that will die and settle to the bottom of the water, and they can give us a lot of information about the seawater at that time as well. And here's a good example: graptolites. Very abundant in the early Paleozoic. The picture, the image there on the right is of a colony of graptolites. So these are very small microscopic organisms. An individual would live in each one of those little tubes. And so they lived as a colony floating in the seawater. They would die, the colony would fall to the sea floor, and we get lucky and they get preserved sometimes. So I have a picture of a rock slab there on the left, pencil for scale, and you can see those little black marks are the carbon remains of those graptolites. 

Graptolites were very abundant. They evolved very quickly, lots of different forms, so they're great index fossils so they can help tell us what rock layers we're looking at at different snapshots of time. One more example of a tiny fossil, microfossil, are the conodonts. What you're looking at there are elements of the only hard parts that we think that organism had. It's a soft-bodied organism. The little cartoon there on the bottom, an eel-shaped body and no jaw, but within its throat were these elements that were hard parts and kind of like teeth and jaw parts that would help break up the food as it digested. The length of that little cartoon conodonts, we do have some fossils of whole conodonts, but they are small. The whole organism would be anywhere from maybe a centimeter long to we have some gigantic conodonts that are up to about 15 centimeters long, or maybe about 7-8 inches long. So they're fairly small. But they're great, because just like the graptolites evolved into a lot of different ones very quickly, and we have lots of their jaw-like elements left to identify and they can help us pinpoint what rock layers we're looking at. 

So those were interesting and they can tell me a lot of information, but I'm more interested in the bigger fauna. So I'm going to focus now on some of the larger animals that were alive on the sea floor. So, if we look at the fossils, some that are going to be familiar and some less familiar. So we have snails or gastropods, which are a group of mollusks. So we've got, on the right there is a picture of fossils that are in the rock slab, and those are not of the shell itself. The shell has been decomposed and not left. But you're looking at the sediment that filled the snail shell. So we have snail fossils. We have some clam fossils. Again, not the clam shell itself, but you're looking at the sediment that filled up that clam shell after the organism was dead. 

And, again, pencil for scale. So we're not talking about real large clams. Not a lot of good eating there if we were back in that time. Cephalopods, shelled cephalopods. Cephalopods include octopus and squid and cuttlefish, and there's one variety of cephalopod that's still alive today that has a shell, a nautilus, and back in the Ordovician we had a lot more of the shelled cephalopods around. So you're looking at a couple of fossils of the cone-shaped shell. The nautilus that's alive today, its shell is coiled, but these are more straight-shelled variety. And you can see by the scale there, we're talking about a shell that was the length of a couple of inches maybe. Some got much larger and longer. But cephalopods had eyes. 

They had tentacles. They had a strong beak. So they would be munching on the clams and the snails and some of the other sea life. So these were the predators, major predators back in the Ordovician at the time. Here's an example of a much larger cephalopod. So those two earlier fossils that I showed you, now compare that to a section of a much larger cone. So some of these cephalopods got very big. The diameter of that fossil, you're looking at about six to eight inches. Some the length of the whole cone. UW Madison in the geology museum has a beautiful example of one that's over 15 feet long. 

So those would have been some pretty big predators in the ocean at that time. Some other examples of the life, we have corals on the sea floor starting to make the reefs. Different kinds of corals than we have alive today, though. Tabulate corals are all extinct. There's not tabulate corals alive today. These are all colonial, so the organisms lived together in colonies and secreted a calcareous skeleton. So individuals would live in each one of those chambers. We've got the commonly called honeycomb coral because it sort of looks like a honeybee cone. Or the chain coral there. A couple varieties of the corals that were around. 

Another unusual coral, the horn coral. So an individual lived in each one of those. Like the cartoon depicts there in the upper left-hand corner, the narrower end would be attached to the sea floor, and an individual would live in there and would gather its food by whatever fell into its mouth drifting down, settling down through the water, or maybe swimming a little bit too close. So we've got corals. We've got trilobites, which we've decided to have as our state fossil. So trilobites are an arthropod, a relative of crabs and lobster and shrimp. So we're looking at an organism that had an exoskeleton. We can see the head end on the lower right. You're looking at its back. Trilobed shape there. 

So it had eyes. Underneath on the belly side or underside it would have lots of jointed legs like shrimp. It would scurry along the sea floor. Also eating some of the small critters that were in the sediment at the time. So the trilobites, bryozoa. We have bryozoa still alive today but none that look like this. These are colonies. Like the coral, many of the bryozoa lived in colonies. Little gumdrop shapes or twig shapes. Sort of an arrangement like a coral but not a close relative of corals at all. 

Much smaller organisms. If we look at that twig shape on the left there, and then we just look at it a little closer, hopefully you can see the small little holes. So individuals would live in each one of those little holes. Much smaller than coral. So we have bryozoa and bryozoa were very prolific. Lots and lots of bryozoa on the sea floor. So here's one rock slab that's got lots of those twigs that have been broken off and collected there on that rock surface. Here's an interesting find that I find interesting A piece of rock that kind of looks at the ecology or how different organisms were relating to each other at the time. We've got a cone-shaped cephalopod there. You can see the end of the cone on the left. 

Cephalopod shell, the cephalopod died, settled to the sea floor. The shell is laying there on the sea floor, and bryozoa encrusted right over top. So they attached right on to that cephalopod and grew as a mass layer right over top of that cephalopod or anything else that happened to be on that sea floor at that time. All of those organisms are very interesting to me, but I'm focusing on one of the other members of the ecosystem back then: the brachiopods. And brachiopods are still alive today. Probably most of you have not heard of them because they're not real abundant. Not good eating. They're bitter. We wouldn't want to eat them. The clams kind of pushed brachiopods out of the way over the history of the Earth. 

And clams and the other mollusks evolved into many more types and more abundant, and the brachiopods were kind of pushed out of their niche into deeper, fouler water. And so we don't see a lot of brachiopods today. Similar in shape to a clam in that they have two shells. The shell arrangement is slightly different than a clam if you look at the symmetry. With a clam, one shell is a mirror image of the other shell. Whereas as brachiopod, the two shells are different, but the line of symmetry cuts the shell in half. So the left half looks like the right half. Brachiopods were attached to the sea floor, solid rock or a shell fragment, anything that's lying on the sea floor, by a stalk, a fleshy stalk called a pedicle. And they would be attached to the sea floor with the shells gaping open. Their soft tissue extended out gathering food out of the water column. 

So they're suspension feeders. Like I said, brachiopods are still alive today, and here's an example of one that's alive so you can see that fleshy stalk. So the shell there on the left, the fleshy stalk and attached to the sediment. Not in life position. It would have been standing up in life position. So that's a brachiopod. I see brachiopod fossils that attach to the bryozoa. So you can see the very small little brachiopods here attached to bryozoa. So they'll attach to whatever is standing still long enough for them to attach to. It can be a rock, it can be another brachiopod, or the shell of any kind of organism that was alive at that time. 

So I have focused a lot of my research on the brachiopods. They were the most abundant organisms on the sea floor back in the Ordovician. Lots and lots of them. Lots of different kinds. So I can look at the diversity of the brachiopods. I can look at the evolution of different groups of brachiopods, how quickly they evolved, how diverse they were, and they can tell us a lot about the sea. They can tell us about the water quality, the water depth. So we get a lot of information about the brachiopods. So I will go to the rock outcrops and where there's shale and the brachiopods are a little bit easier to gather. I will scoop up shovelfuls of the shale. 

If you ask my husband what I'm doing, he'll always say, oh, she's out bagging dirt again. Well, not quite but he's a musician so you know. To him I'm bagging dirt. So I'm gathering shale and separating the brachiopods and identifying the brachiopods. In other places they are embedded in carbonates, in the limestones, and I can't take them out of the carbonates because the limestone is made chemically of the same material as the brachiopod shell. So if I use acids to dissolve away the limestone, I'm also going to dissolve away the brachiopod shell. So it's a little tougher to identify the brachiopods. So here are a bunch of brachiopods embedded in carbonate. Lots and lots of them. So what this tells me is it's a time that we probably had a storm move through. 

So a storm moved through, the waves are more energetic, the finer clay has drifter more into the deeper water, and what's left is a pavement of the brachiopod shells. So the shells are there, and they're kind of oriented all in the same kind of position, the most hydrodynamically stable position which is convex up. So the water energy was high enough to remove the fine material, or a lot of the fine material, but not so much energy that the shells are getting broken up, crushed, like they would if the water was very shallow like close to the shore. So it tells me a lot about the water depth and how much energy is there. And we don't see a lot of the brachiopods broken and crushed, which would also indicate that maybe organisms were crawling around the brachiopods, through the brachiopods, overturning them. So there wasn't a lot of activity in the sediment when these were deposited as well. A lot of different kinds. So I identified those different kinds, and I look at the quality of those shells. Are they broken? Are they whole? Are both valves together? Are the valves separate? So all of those things can tell us a little bit about what the Earth was like back in the Ordovician at that time. So here's one chart that I've compiled from my study of the brachiopods. 

This is some work that I did over a couple of years time looking at the brachiopods, trying to identify them down to the species level, which requires being able to see the inside and outside of the shells. So in order to give them a species name, for every brachiopod I could name, I probably had to look at a hundred other ones that I couldn't name because there wasn't enough of the shell material to identify it to the species level. So out of, I don't know how many thousands I looked at over a couple year's time, I was able to identify to the species level a little over 7,000. And so you're looking at an arrangement there of the life span of those different species. Not individuals but when a species appears and when it disappears. So each one of those bars represents an individual, or not an individual, I'm sorry, a species of brachiopod. So this is within the Decorah formation, which at the bottom is very shaley, and lots of indication that the water was very anoxic or close to anoxic. Low oxygen. Not great for a lot of life to be bountiful. But yet, some of the brachiopods and other organisms were able to survive in those waters that were not real hospitable to life. 

That dashed black line toward the bottom there is marking a change in environment where the ocean water became more oxygenated. And we see a lot more diversity of the brachiopods and all the different fossils in the rock record. And we see more of the fossils being crushed and beaten up and a little bit more braided by the activity of the water. So what I have found by looking at those 7,000-some brachiopods is I can kind of break them up into groups. So that's what the color coding is showing you. The red were brachiopods that I only found in the bottom shale layers. So they appeared and they went extinct within the bottom shale layers. And along that little sketch of a rock column there on the left, you can see the E, M, and D. Those are marking those ash layers that we have age dates for. So I can see how quickly those brachiopods evolved and went extinct. 

And in the green there, so the middle section, the green, those include brachiopods that evolved, and I find them in the rock record in the lower shale layers, but they existed up into the higher part of the formation that's more oxygenated and more carbonate-rich. And then the blue, on the right, are fossils that show us the brachiopods that only appear within the carbonates when the water was more oxygenated. To give you some idea of what these look like, here are a couple examples of the brachiopods that are in the red. So, not a lot of diversity. Pionodema and Doleroides there are two different genera of brachiopods. They look very similar in a lot of different ways, but they are two different genera. And those were the dominate kinds of brachiopods in the shales, in the lower shales. In the green, those lines are really narrow to indicate not a lot of specimens. Pretty rare. I had a couple that were more abundant. 

So those fat or green lines are a couple of species that are more abundant. This is one of those. Strophomena, a little bit bigger. You can see that scale bar there. It's a fairly big size brachiopod. So it existed in the shale layer and in the carbonates up above. But the rest of those brachiopods that make it through from the shale to the carbonates are rare, not as abundant, and a lot of them are very small. So here, for example, are some of the brachiopods that are colored green in that diagram. So a lot smaller in size, just millimeters across in size. And then the blue ones there that I have colored blue, there were some that were very abundant and found in many of the rock layers I investigated. 

And they're a little bit bigger in size than the majority of the ones I had colored in green. And the shells are thicker. The ribbing that you can see on the outside of their shells is a little more durable. So these are the types of brachiopods that could have endured a little bit more energy in the water. Maybe shallower water environment. So that's what I've been spending some of my free time at is looking at these brachiopods when I'm not teaching and interpreting what they are telling us about the Ordovician, the early Paleozoic. The climate was much warmer back in the Ordovician. We had probably no ice anywhere. We saw in the cartoons that sea level was much higher. Carbon dioxide is a greenhouse gas, and we're concerned about the rise in carbon dioxide in our atmosphere today. 

And we can look, then, at what was happening in the Ordovician with these high carbon dioxide levels, how did life respond to the change of the differences in the oxygen levels and the carbon dioxide levels and look at how it affected the life in the sea at the time, again, not much life on land. So there's certain relevance to looking at the geologic past, interpreting the environment, and trying to make some educated guesses at what might happen to us in the future here with our rapid climate change. What might we be faced with here in our future. So, kind of your take-home points here, a very different Wisconsin than we know today. A watery world. Lots of diversity in the ocean, very little on land. High CO2 levels. High oxygen levels as well in the atmosphere. About 68% oxygen in the atmosphere as opposed to 21% oxygen in our atmosphere today. So higher oxygen. 

Higher carbon dioxide. Warmer environment. Lots of rapid change. The end of the Ordovician we see a huge temperature change, and we see a glacial event. So we have an ice age at the end of the Ordovician, and we tie a lot of the extinction that we see with the organisms probably to that glacial event, the cooling down of the globe. And many of the organisms that lived in the ocean could not tolerate that big change in temperature, and so go extinct at the end of the Ordovician. And I'm very happy that we have these new uranium-lead age dates for those ash layers because we can be more precise when we're talking about these changes when they occurred. So my future work is to continue looking at brachiopods and identifying brachiopods, extending to different areas, comparing what I see here in the Midwest to other parts of North America and even across into Europe. So making larger global comparisons to what I see here. But that's kind of what I've been doing and what I've been spending some of my time on when I'm not teaching. 

So, thank you very much. 
[APPLAUSE]