WVGES, Geoscience Education in the Mountain State:
CATS Geology Telecourse, Spring 1999,
Show 5 Transcript


CATS Telecourse Broadcast
Historical Geology
April 7, 1999

Dr. Bob: Let's catch up so that you are comfortable. We've been off air for quite some time. Some of you will be seeing this on tape because spring breaks are still occurring in sort of a staggered lot across the state; some are last week, others are this week, and will be seeing this on the tape. Our sessions that we call Exploratories were held since our TV. How did yours go and where were you in that session?

Deb: I was at the Survey here in Morgantown and we had a great day. We didn't get to go outside. Most of the activities we did were very classroom, indoor orientated. I think we got through a good bit on relative and absolute dating and we did learn never use pastel-colored M&Ms for any activity that requires you to see the "m" on them. They were misleading. They rub off and they're hard to see at best. Never use Easter-colored M&Ms.

Dr. Bob: I was down in Craigsville and it was a little brisk in the morning but it turned out to be a beautiful day. If you'll recall about a couple of weeks ago we were really concerned about snow being out in the valleys and down in the deeper places. But we were outside most of the day. Recall that what we were going to do is Tom, Deb, and I will go on a carousel. Our next one is on the 24th of April. Deb and I and Tom are going to rotate. You will all go to the same location. I'll be out in St. Marys and we'll spend most of the day out there too. Hope for some great weather. It turns out that we went to some of the great places right around Craigsville and Crupperneck Bend, and some really nice topography--things that we're going to be putting into our virtual field trips for our undergraduate students as we put together a web site. So it was a precise location that I have not been to before, but it is a beautiful link with the Gauley River because we can talk about an entire river system: Cranberry Glades, the Gauley River, the dam and human intervention onto the waterway, and then the rafting down below, so we'll have to go rafting in October. Where the Gauley intersects the New River, the river changes names to the Kanawha River and it really becomes the West Virginia scene, if you will, in terminology. So I just thoroughly enjoyed myself and I learned something at every one of these locations because I had not been to your backyard! So we're looking forward, as we always do, to the upcoming Exploratories.

So far we have had three quizzes. You have received a spat of calls regarding that. What is your general impression as to the calls and the nature of the questions?

Deb: I think that mostly the participants and the students in the class have the answers. They're calling in for confirmation. They're just not quite sure--in particular, the one question about the types of weathering environments during the Archean. They know the answer, they're giving me the right answer over the phone, but they just want to make sure they're on the right track.

Dr. Bob: That's fair enough. There will be one more quiz and then there will be a take-home test. The take-home test you should have within a week. That will not be due back until Wednesday, May 5th. That's the week after the last telecast. So there will be again one more quiz and then the one take-home test due on Wednesday, May 5th. All of that will be coming, mailed to you. The only urging we have in general is that we move into historical geology. When you were in the classroom, you didn't have as much time on that, right?

Deb: And I didn't have as much knowledge either, to tell you the truth at the time. I think teachers tend to ignore historical geology because they're not comfortable with it; they really don't have a good feel for depositional environments. So there's a time factor involved and there's also a little bit of an ignorance factor.

Dr. Bob: What we're going to do now is to really emphasize West Virginia. The result of that is that there are a number of chapters that I will identify for you where you have to do a lot of reading and use the text as a resource material, and you won't find much of it in televised discussion. The reason is that we really want to focus on West Virginia. We want to make that bridge for you to take you from your strengthening understanding of physical geology and get into what historical geology means.

A simple analogy. We talk about rocks and we've identified in the fields sandstone, limestone, shale. In historical geology we're talking about sandstone but was it a beach. And was it a beach that very slowly was moving because sea level was rising onto the continent? Or was it a channel sand? Was it a single channel meandering its way across an ancient landscape?

Think of today's topography as an environment that you may have found sometime in the geologic past somewhere on Earth. It is not real likely that the incision of rivers is going to be preserved in the rock record with the preciseness of what we see rivers incising the mountains today. The reason for that is that we see that picture of time in moments, measured in seconds, minutes, days, months. Even our own lifetime, which is but a small, small portion of what geologic time is. So that given millions of years, the landscapes of today are going to become old and tired and more mature, and the diversity in local relief is going to blend into lower relief. That's why you wouldn't find a landscape like all of West Virginia suddenly buried in the rock record. That doesn't happen. If you scale that down, we will start talking to you about little river channels that were buried. An old floodplain that was cut into, and the channel sands have packed up against the older floodplain material, and that has been preserved here in Morgantown.

So getting back to the transition, sandstones: are they channel sands? Were they beach sands? Were they offshore bars in a marine environment? Were they sand dunes? Sand as a particle size is a reflection of the energy of the fluid in motion, and we start in historical geology talking about what was going on both in the weather, the climate, overall the long-term picture of what was happening along the margins of the continent and deep in the interior of the continent. So that's sandstone.

Shales: were they deep ocean shales, collected far from shore, no doubt, in deep, deep water? What color are they and why are they that color? Are they black? Is it rich in poop? Lot's of that good organic poop mixed into the mud, that was a great feeding place for all little critters. Little critters come and bigger critters come to chow down on the lower-sized critters. That's life! OK. Or was it a shale that's a floodplain and therefore part of a continental environment. If it was a floodplain, was it at a time when there were land plants? If there were land plants, do we find them in the record either buried on the floodplain or as logs or branches or as inclusions in channel sands? Today you say if a flood occurs, for example the 1985 flood, it's going to sweep clean the floodplain isn't it? Those logs got rolled in and the ones that weren't taken out are buried. They could become fossils if left alone. But more likely than not, with the steep topography we still have in West Virginia, it would be exhumed later on and disappear. We're going back and looking at what shales mean.

In limestones, the big difference there is, is it a marine limestone? Is it a marine limestone of quiet chemical precipitation? Or is it a reef where there are very obvious structures? Was it a reef that was dominated by certain animal types? Mostly invertebrates and some vertebrates later in life came along and chowed down on the invertebrates. It was a great place to meet and eat along the reef. On the other hand, is it a quiet type of continental type of pool maybe fed mostly by ground water? Yet it's a carbonate. You come up into north-central West Virginia and we look a the Pittsburgh coal seam, or I take you on a field trip to the new Mountaineer Mall and we go to the upper level of the Mountaineer Mall, I show you the Pittsburgh coal seam and it's only about six or eight feet thick there. What are the rocks right above it? Limestones, but no marine fossils. No evidence at all. They've always been called freshwater limestones. They tend to be very thin, rather local. We have to talk about the environment.

So the rock units tell us about environments now and that's that transition between physical and historical geology. That's the connection we want to do.

Now Deb, because we want to talk about connections, what are the connections? What is a quick overview, because it's been a while since we talked about the Precambrian? Essentially the Precambrian looks like a time when there was life but it was pretty innocuous. It wasn't critical except for the atmosphere. What are some of the salient features? Why don't we go over that now.

Deb: We just have a couple quick points or bullets about the Archean. First, the proto continents are extremely small. They're kind of moving around at a pretty rapid rate because the convection cells are pretty quick, and until those convection cells and the Earth start to cool down a little bit, these things aren't likely to collide. So we've got one major collision that we made a note of and that was the Wopmay Orogeny, and this is in the Canadian Shield. So, we do have one significant collision there that did occur during the Archean that is important to us in the continent of North America.

Another notable event is that we've got a lot of greenstones. Often these greenstone deposits are submarine. There are volcanic vents and openings where lava has exuded or moved out into and cooled rapidly under the ocean, and they form these things we call pillow lavas because they're kind of billowy and pillow-shaped. We have many of these being formed. The atmosphere of this primitive Earth is really caustic. Whatever comes out of a volcano is essentially what that atmosphere was going to be like: a lot of sulfur dioxides, a lot of methane, a lot of nitrogen, carbon dioxide, and a lot of water vapor. The predominant life form at this point are the cyanobacteria which then will kind of form mats to form stramatolites. And that was it pretty much in the way of life for the Archean. This extended until about 2.5 billion years ago.

Dr. Bob: One of our physical geographers was out looking at the newly-created vents on the big island of Hawaii where the volcanic material, the lava, is coming out and flowing into the ocean. He said it was quite a long hike and they had many warnings along the way because the stuff is still hot. But the interesting thing is they had to turn back because of the mist. How many of you have ever in a laboratory opened a bottle of concentrated hydrochloric acid? You can smell it immediately, right? Sometimes you even breath and you see a cloud of dead cells because you've inhaled some of that. He said the mist just reeked of hydrochloric acid because of the chlorine coming out of the vent and the hydrogen chloride. So those events are still ongoing.

The present is the key to the past. We look at today's volcanos and we test the gas. We say it is quite likely that gases that are coming out today were the gases that were coming out, maybe in different proportions, before. Now after the Archean, what do geologists look at first? The very old stuff? Not exactly, unless it had metals in it, gold and silver and other metals. The real start of modern geology was in the Paris basin where engineers were working in sedimentary rocks and fossils. In fact, fossils in that part of Europe included dinosaurs, reptiles, and modern vertebrate forms. So we have this really old-looking rock and then people saying, hey, the younger rock is really full of fossil life. But of course, what were the early geologists facing then? It wasn't all that easy to be a geologist back in those early days. You were delving into the heretical statements in talking about Earth being very, very old. So after the Archean, your Precambrian at a glance, and then talk about the Proterozoic.

Deb: At this point the micro continents begin colliding. The one that we pay attention to the most in North America is the one we call the Grenville Orogeny, which happened when the supercontinent Rodinia--is that how you pronounce it?

Dr. Bob: Yes, we'll talk about Rodinia. Somewhere between 1.2 and 1 billion years.

Deb: We acquired part of our continent through that collision and that tacked on a little bit of material on the eastern seaboard of North America. At this point, the atmosphere begins to acquire oxygen, and we know this because of what we talked about last time and that was the BIF or the banded iron formations. In order to get the banded iron formations or the rust, the red appearance, there must have been oxygen. So the oxygen must have been accumulating and then being pulled into these sinks. Once the sinks then acquired as much as free oxygen as they could handle, then the excess would have been left for the environment.

Dr. Bob: A sink simply means that the element that we're looking at specifically gets tied up in a way that its not free to be an interactive part. And the banded iron formations, that iron has been tied up for over 2.5 billion years. It has not been active until it was made into the car you're driving today. You say well, mine isn't an American model. I say, ah ha! The vast ore deposits for the creation of steel, that vast ore deposits worldwide of the source of iron are far and away Precambrian age. There are some others. There are some iron ore deposits that are part of igneous intrusion in a certain area, and the magma contained iron, and the iron scooted out and became locked up in lenticular layers in the country rock.

Then there were other iron formations of one specifically in the Silurian. You know, so much of this industry has gone. We have some of that Silurian iron ore in West Virginia but it was for mom and pop type things: making andirons, the local type of smithy, putting together horseshoes, potbellied stoves, and some of those items. Larger deposits of Silurian age are found in the state of New York. The Union ship, the Monitor, was made out of those rocks. Those type of deposits are all the way out in Wisconsin, too. Silurian age, a curious time of more iron.

The point was that the Precambrian rocks hold a wealth of metals and some nonmetallic as well as precious metals and base metals. It's not only iron and zinc and lead but also precious metals like gold and silver. So the Precambrian historically has been a very important rock unit and age of rock to look at. But the early geologists saw this as the basement. Although they didn't use the term basement, they said these were the primary rocks. They looked old and it's true. You go out and you look at Precambrian rocks, they look old. They're dark. They're not bright pastels. The iron color in the younger Precambrian rocks, it's dark red, dark colors. It's not the rich oxidized iron of maroon of some deltas or that later on. Then when they looked very closely at the contact with the overlying material, they said, you know, it stands to reason to us that this older stuff--all the grains are all squeezed together and grown together. That evolved into the discussion of igneous and/or metamorphic rock. We often talk of it jointly as being crystalline. The crystals have grown together. There's no pore spaces. The rock above was layered and it became known as the secondary rocks. It happened later and it really was the result of the development of the law of superposition. If things aren't overturned totally by some great force but things have accumulated, the ones on the top are younger then the ones below. In West Virginia, we do have basement rocks. That was one of the things we talked about down at Craigsville at my Exploratory and I'll bring to each of you. There are places in West Virginia where to get to the basement, you'd have to go down 22,000 feet or more. That's a lot of steps to take to walk down into that particular basement area. So by and large, the West Virginia history is one of burial of the basement. We'll get to the burial in a moment.

Let's start thinking about that basement and other places of the world. This is where your reading of the chapters will have to fill in. I may ask a quiz question or a test question that relates to things that you read out of the text but we don't specifically talk about because we're going to focus more on West Virginia on television. We need to have the understanding that special areas around the world have led us to very important discoveries where we're putting together the story but we don't have every page of the book. Sometimes whole chapters are missing at one location. Many of the early chapters, we only have a sentence or two if we're lucky. Mostly we have just a couple of words. How do you put that story together? Well, it turns out that geologists are great at putting a story together with very little information. Geologists often talk of the big picture. We're talking about things globally with all of these details missing now. Maybe someone in the next generation or two will find bits and pieces to help enhance the story. By and large, what we put together by the turn of this century is not a bad picture of the broad aspects. Surely plate tectonics is a young concept. The early geologists found fossils in the state of New York that seemed to be the same age as the fossils in Maine and New Hampshire. But they were different. We didn't find them intermingling. It's as if there was a giant chasm in between. So geologists had to devise an explanation and they said, well, there must have been very deep water. There was a shallow shelf here, a shallow shelf there, and very deep water in between and it was poisonous because there was no oxygen down there. We find some places where there's very little oxygen. So the critters couldn't walk down into it. If they did, feet up and they're gone! The fact that we didn't find them feet up should have been some sort of a clue, but we didn't have all that picture. We said, well, there were chasms, there were ancient barriers between even though they were close together. Now we say, this was a shelf, and this was a shelf off the screen, and then at the growth of your fingernail, one of them moved in, and as Deb said, little pieces begat larger pieces by, what the term was early used, continental accretion. You bring on all these extra pieces like little pieces of clay.

So, continental accretion was a very, very important concept as recently as the 1950s and 1960s because it was in 1950, actually '54, when we first began to use radiometric dating. Today after 25 years of very determined review of the rocks based on the concept of the theory of plate tectonics, we introduced new names, terrains. The terrains were like islands and little continents that were added on. Sometimes these terrains were all volcano genic, meaning that they were originally lava but then the lava was broken up by wave action. The lava was broken by landslides, waves pounded, rivers worked on it, and it became sediments of the volcanic rock and it all became worked together, and then whomp, it adhered to a larger-building continental mass. That's what terrains do to build it.

But lets get back to that end of the Precambrian. In the context--you and I have talked a bit about it, Deb--in the context of the development of life, how much are you able to get across in a classroom about life and development and evolution of these changes and forms?

Deb: You can present it to students and whether or not they can really fathom or comprehend what it actually means, they have a hard enough time dealing with geologic time, much less dealing with changes over those times. So to try to get them to fathom evolution is difficult at a young age. As they get older, they tend to grasp it a little bit more and then at some point, you're fighting religion in there also.

Dr. Bob: All the time. Then too, you had made up a little form and outline. Speak to us about how physical geology and historical geology might translate and correlate.

Deb: I thought it would be nice to kind of discuss the fact that the unit plans were coming in and most of them seemed to be focusing on the rock cycle and erosion and weathering. That's really physical geology. What we'd like to see and what we're going to talk about today is really a historical aspect. We're making a transition or leap from the physical to the historical geology.

For example, if you look at limestones, the concept "limestone" is a very physical geology concept. It's a type of sedimentary rock. It's an accumulation of calcium carbonates. It's part of the rock cycle. It's one of the sedimentary rocks where things are glued together. It's a biotic or a chemical type rock, a non-clastic sedimentary rock. But what we want in historical geology and what we want to see in the unit plans is now thinking of that not as a rock but as a old environment. It came from some environment. It was sediment or it was an accumulation of material before it was a rock. So in example, these are not by any means exhaustive examples, these are just a couple. You could include platforms in here. You can include freshwater environments in here for limited numbers of freshwater limestones, but a reef or a bay is a classic environment for a limestone to form in.

So when you see this limestone in historical geology, we don't necessarily want you to see the rock. We want you to see what it means in terms of what was there at that time in history. And so a limestone could be indicative of a reef or a bay, and if you think of that, you have to think of present day. Where is this happening today? How can I visualize what this would have looked like, say, in the Ordovician, or the Mississippian, or something like that? Where can this be happening? And you can look to the Florida Bay where the keys are, or the Bahama Banks. So if you can visualize this type of environment, it's a lot easier to see where this rock originated from.

Dr. Bob: It doesn't take older kids necessarily to hop onto the web site. They say, well, I've heard of Australia and the Great Barrier Reef. They'll probably be able to access a web site and get some pictures of that and bring that up and say, oh, that's what we're talking about. Then your task would be to say, well, where are these? Are these in the arctic north or are they around the Antarctic? The kids will say no. Then say why not? What is the key element? And then you start saying, well, temperature, temperature of the water. Is it critical? It really is. It's a narrow range. If it gets too cold, what happens to the critters? If it gets too hot, then there may be evaporation of the water and what happens to the saline content? It goes up. Do critters like high saline environments? Not many critters. Survivors. We'll talk about that. That's what happened to the stromatolites. Neat. Tuck that away. We'll talk about it in a few moments. What else can kill these reef critters? If you build your home on the island and you dig in the soil, and you dig in the rock and it rains, and all that soil and sediment goes down into the bay out to the reef, what happens to the reef? You bury the reef. We are destroying the island paradise of Hawaii as we speak because of siltation because of human interaction. Now it is true that climate changes have destroyed reefs throughout geologic history. But in our short human endeavors in the past 50 years, we have done more to destroy reefs then you can imagine. Ships run aground and perhaps break off thousands of years and destroy thousands of years of a reef off the coast of Florida. Shell collectors go out and scavenge these because people want to buy them to put on their tables in their living rooms for show or on their bookshelf. We have destroyed reefs.

Deb: Another example we have that's really important is our coal, West Virginia's coal. When you're looking at a lump of coal, at this point we don't want you arguing whether it's a metamorphic or sedimentary rock. We want you thinking about what environment it came from. What had to be there during the Pennsylvanian in order for this to be there? The classic environment for a coal deposit would be a large amount of organic accumulated and that would tend to happen in, say, a swamp. Swamps are really nice for this because there's a large amount of biomass, logs, and trees. Then again, in marshes, too, over long periods of time, the grasses die off and they form these mats that are buried under the sediments that wash in. So you've got an accumulation of organic matter that then is subsequently buried. These swamps or marshes are prevalent the world round and we know of coal deposits presently being formed in Borneo. At least that's what I've read.

Dr. Bob: We can also just talk about swamps in general. Are there swamps in West Virginia? Yes. Are they likely to create many feet of coal in the geologic record? The answer is highly unlikely. They're up on mountain tops, they're on river plains, they just happen to be little pockets and intuitively you suggest they are vulnerable. They may be wiped away before they're ever buried and preserved. But if some of your students have said, hey, I was out at Ocean City or Chincoteague or along the Eastern Shore, North Carolina, and whoa, I got out of that water at low tide. Boy, did that reek. Ah ha! What are those gases that are coming out? It turns out that you get those swamp gases. One of the critical ones is methane and hydrogen sulfide, gases that are important in climate change but gases that are being emitted as that organic material settles down to more pure carbon accumulation. Coal certainly is something that our youngsters know about. Everywhere in the state, save maybe the eastern panhandle. Let's go to the next one you have.

Deb: Another one of our predominant sedimentary rocks in West Virginia are siltstones or shales, and a variety of environments where these silts and clays might have settled would be a lake or a lagoon or even offshore. You get offshore from a delta where the water kind of slows down but it's still carrying a lot of fine material, and then it enters a deeper ocean environment. Eventually it's going to slow down enough so that the silts and the clays will settle out. So you'll get shales forming out there. Anywhere there is small fine particulate matter carried in water, the water slows down enough, quiet enough to allow the silt to settle out, will form a shale. Well, there's a variety of places that this can form but the classic thing is think of any farm pond. They silt in eventually. Assuming if they got buried, which is this whole classic coal discussion that we just had, they're suspect and they'll get wiped out eventually. But these are the types of environments that could potentially form a shale.

Dr. Bob: It's interesting. A special word of warning which fits in with my comment of the black shales before. If you're going to have students collect these things, and say, well hey, the river overflowed recently, or maybe you're over on the Ohio River and the river flooded. There's lots of this fine-grained mud. Maybe we'll run out and collect. I'd urge you don't do it. Even the farm ponds. There's a lot of nastiness that can accumulate in bacteria and especially along big rivers where it washed out a sanitation department and raw sewage went in. We collected some after a flood on the Ohio River a couple of years ago in January. We brought it into the lab and put it in beakers over the weekend to dry out. We came back in Monday and opened the door to that lab and oh my! And you would only want to touch that stuff with rubber gloves, heavy rubber gloves. You just don't want to handle it. You'd have to treat it with so much hydrogen peroxide to oxidize off that you just don't want to do it with kids. We felt uncomfortable as adult scientists working with it.

Deb: The last one we have is, of course, a sandstone which you can get a variety of places. Two classic ones would be a shoreline, beach area, or a river bar as we were talking earlier. You could even consider a desert in there. I just listed those two particular ones. Again, we're talking about a relatively larger particle compared to the silt or the clay. A sand grain. A classic environment for this would be the Mississippi Delta. I use this one in particular because our Pennsylvanian-age sandstones are much like this Mississippi Delta area.

Dr. Bob: Now, those are fine sands by the time it gets down there. But you might be able to go out into your local stream and see in the eddy behind a boulder a little accumulation of coarse sand. If that became cemented, there will be sandstone. You might even pour a little Elmer's into it. Collect it in place, pour Elmer's into it and glue it up, and it's a sandstone. That's an excellent portrayal. One thing that we often jump to very rapidly is that if you do get a chance in the classroom to talk about critters and fossils, you talk about the big stuff. You can see it, macro fossils. Most of it is of Paleozoic age. Most of it is common in West Virginia. So what have you put together here?

Deb: We were talking about these sedimentary environments and some of them can be confusing; for example, the sandstones you mentioned earlier. How do you know if a sandstone is from a river or from a marine type of environment? Here's where you really need some other information to help you narrow this down. In one particular case you can use fossils to help you. Not always but it can help at least narrow it down. For example, if you find brachiopods in your sandstones or your sedimentary rocks, then you know by definition that it must be either a saline or a brackish condition in which that sediment was laid down.

Dr. Bob: Now you will know this. There aren't many brachiopods left, but scientists would look at the modern brachiopods and say they are only in marine or brackish environments. The fresher the water, the fewer the brachiopods. They're filter feeders. They like to be out on the surface and still filter. But there's another group that we'll talk about later, because if you're out on the surface and filter feeding, what are you to fish? Lunch. You're real vulnerable. So what happened to the brachiopods throughout geologic history? They've been munched on. They aren't as common anymore. But all the other evidence speaks that they're only marine or near-marine environments. Also, notice in this brachiopod side view that the top and the bottom shells are different shapes and forms, but there is a symmetry. Here's a top view of a different brachiopod shell, and I am drawing the symmetry line so that the right-hand side and the lefthand side are mirror images of each other. That's the symmetry of the brachiopods. But the two shells are different. We call the upper one, or the top one, the dorsal, and bottom one the ventral.

Then you have one of the favorite fossil critters of the Paleozoic. I say the Paleozoic because they weren't here before the Paleozoic and they weren't here after the Paleozoic. As a matter of fact, they barely made it into the end of the Paleozoic. What are these little critters?

Deb: The trilobites, which were saltwater again. So if you know you have a trilobite, you've got a saltwater or marine environment, and I added there that they were bottom feeders. They really didn't have mouth parts, so they just kind of scooted around the bottom filtering or sucking debris.

Dr. Bob: They're scavengers. Sometimes we have a negative view of scavengers but they're important. The "three" that it comes from is not that there three parts to the thorax but that there is a head or cephalon, as the fancy word. That's the head, the body or thorax, and the tail or pygidium. That's the three parts of the trilobite. Many times folks think that it's the three lobes of the thorax. It's real obvious. Sometimes the pygidium's real small. It was interesting when I was down in Craigsville, one of the class members had brought along a form and they said what is it? I got it in an antique store and it was a huge fossil, trilobite. The pygidium was about the size of my fist. The head was huge.

(BREAK)

Dr. Bob: Let's call our attention to the textbook. If you have it there, you can open it to the page and if not, just write this down. Page 315 in your text is followed on page 316 and 317 by what is called by your author a visual overview. I'll refer to it as a cartoon. We're going to show it on the overhead, and it's not going to be able to pick up the differentiation. The point that we want to get across is that these cartoons are really special. I have chosen this book because these cartoons are so good. You have to be very careful, the page numbers never appear on these pages. The numbers down in the lower lefthand corner refer to the years before present. So its great when its 2.5 billion years. But when its 344 million years, that's not page 344. OK.

Let's just put something up there of the transition on the overhead to talk about it. On one side, the author has a great deal about life forms. On this particular page, it's the Proterozoic. Again, I'm not going to be able to do much more, that's the scale. But he talks about these great stromatolites in the time frame from 1.6 to 1.0 billion years before present, the greatest time when stromatolites were ruling the sea floor. Why? Nobody was there to eat them. No wonder they ruled. And what a critical situation. In all of these patterns and connections, for other forms to thrive there has to be food. Whether it's a ratio of 10 plant-eating dinosaurs to one carnivorous or a whole biomass of stromatolites to one trilobite, there has to be food. It has to be reasonably obtained. Now it turns out when we look at the analogy of lions on the plains going after zebra, there's a lot of failures out there. A lot of those hunting trips turn out not good. We happen to see them in the videos because those people have spent hours and hours and hours trying to capture a successful hunt. They never tell us totally how many miles of film they wasted because the lion lost. The animals got away. Same thing with the invertebrates. That's why this page is neat to show. On the right-hand side of the page, the banded iron formations. Two phases of them in time. There are discussions of specific elements, in this case, carbon and isotopes of carbon. We're not going to talk about that now. We will save that for individual discussion at the Exploratory sites and later on, if we have a chance to get to it. We want to paint with a broad brush. It's not that it isn't important. We know that we have some questions about the specifics on isotopes and the changes of carbon and oxygen and that. But we want to look now first, please, at the broad picture.

Then on the overhead, there's three neat global pictures. One is a word that I bet you haven't heard until you opened this book, because it isn't in your other textbooks. Rodinia is hardly a bumper sticker term like Gondwana is. Rodinia is this massive continent. Going back to the overhead, we see that there is a question here. Was there another supercontinent a little over half a billion years ago? The reason is, we talked about this early on. Rodinia was the closure about a billion years ago. Half a billion years of time is portrayed in this distance on the sheet and that's a Wilson Cycle. Remember Jay Tuso Wilson from the Toronto Museum traveling about in the 1960s starting to put together a big picture of plate tectonics? It was named in honor of him. You said, you know, when you look at this, it looks like about a half a billion years is a cycle, opening and closing, if you will, or from closure, opening, and then closure again. The reason is that there's a lot of change going to come about in the next 250 million years. The second reason is sea level changes. So the coasts are not like the coastline we know and love today.

Where was Europe? Well, in two places. There's a Baltica, which now is what we recognize as the Precambrian Shield of the Baltic states, Norway, Sweden, Finland, those areas. And then Siberia is way off; it is not yet connected. There's an interesting story here. Can you think ahead? Is there a mountain chain in Russia that is about as long as our Appalachians, about as wide as our Appalachian chain, was formed about the same time as the Appalachian chain? If you think of it with the "s" on the end, it's a five letter word. Urals. The Ural mountains are almost a mirror image except for one critical fact in the past 200 million years. What did not happen to the Ural mountains in the past 200 million years that did happen to the Appalachians? The pulling apart. It didn't pull apart. It's still welded together. North America pulled apart from Africa. Here's the Gondwanaland, so part of that Gondwanaland is Africa. And Gondwanaland is neat because it's been down there a long, long time. As a matter of fact, its a late player in all these other stories, and a late player in breaking up. It turned out that as we did more and more studying, Australia, South Africa, India, and Antarctica, we learned a lot more. Think about that in connections. Where were there the most geologists in the period from 1850 to 1900? The answer was in Europe and North America. Did they have satellite imagery? No. They didn't even have cars, for crying out loud. Some of the early geologists on horseback would listen to the horse's shoed hoof ring off the rock or the material and they'd have, they got so used to the sound, they could tell even from being on the horse what they were probably clippety-clopping over.

Now what about the critters and what was going on? On page 327, there's this term, this is pronounced "ediacaria." It's a faunal assemblage. Not just one fossil but many. Its location is down under, Australia. But the ediacaria fauna is in Australia and the absolute age was in question. When I started, we had known about this for a long, long time. There had been more finds of the really old fossils. This is in that transition period. It's Precambrian. It used to be thought that when you found fossils of invertebrates, it was Cambrian. But these invertebrates are different. They're way different.

Deb: The fellow that I listen to at NSTA has a totally different theory on where these things came from. When they initially found them, they thought they were jellyfish or that seapins may have evolved from these. He feels that this is an evolutionary line that failed because it was unable to compete with evolving mammals during the Cambrian, but that they branched off slightly differently. They didn't form a blastula or a zygote which then once fertilized, differentiated out into separate cells. He believes that these were asymmetrical because they formed from multiple cells. These three or four different cells formed different parts of the ediacoran.

Dr. Bob: Many people have come to call the Cambrian the explosion of life. Maybe it was because with all these stromatolites, the atmosphere. Maybe there was an accumulation finally of poop in the shallow marine environments. Maybe it was because just at the right time, the continents were apart, there were broad continental shelves adjacent to the continents in just the right temperatures of water at just the right time that life experiments began. So that the early explosion of life many are now saying, even into the middle Cambrian, that they were failed experiments. Those forms were bizarre. There's a fauna found in British Columbia and its called the Burgess Shale. It's middle Cambrian in age. Wolcott, the story goes, was honeymooning with his wife. They were apparently up on the mountain where landslides have brought down the material. He just couldn't speak. There were life forms he had never seen before. These fauna contain forms, and we're still finding new forms, and they didn't last long. They were geologically short experiments and the rapid extinction, if you look at the explosion of Cambrian life and then the extinction. But out of that came those sturdy few through diversification. Brachiopods, pelecypods, cephalopods, gastropods, trilobites, etc. I'm not going in any specific order. But these are the forms that were the sturdy forms that then evolved.

What did brachiopods do? I've already mentioned that brachiopods lived out on the surface of the sea floor. They're filter feeders but they're vulnerable. But if you were going to be a brachiopod in geologic time in the Cambrian into the Ordovician, how could you be a more efficient brachiopod? By eating more, getting a bigger gut, and involving oneself in more sexual activity. So you had a lot of offspring. So they became very good at eating and having babies. So the brachiopods just blossomed in this environment until the vertebrates came along.

Now the same time the brachiopods were having fun, pelecypods. But where do pelecypods go? They like to burrow into the mud. They like it down there. That's why we find lots of pelecypods in fossils, because the pelecypods went right down into the mud to be preserved. They weren't eaten, they were out of sight.

Gastropods are a neat story because they're marine forms, freshwater forms, and land forms. If there's food, gastropods will be everywhere. Well, we have set the stage and tickled your memory and said that there's going to be some other things.

Let's talk about the Silurian in West Virginia. In West Virginia in the early Silurian, there was a beach. In West Virginia that beach sandstone is known as the Tuscarora. Where in West Virginia would we go to see the Tuscarora sandstone? Seneca Rocks. Classic location, but is that Tuscarora sandstone; does it look like a beach now? Is it flat? No way. It's vertical, isn't it? It reflects events that happened long after it was made into a rock. But we in historical geology are going to take that sandstone and lay it back down and say this is a beach-type environment. There aren't many critters in this environment. There are worm tubes; they're called scolithies. And the worm tubes do not contain the worms but when the worm left the hole, sand grains came in. Worms often secrete a cement-like material and as a result, there are worm tubes that you sometimes can find. But the environment was not conducive to critters being preserved there, maybe because it was too salty, maybe there was so much action, maybe they dissolved away. Later on we'll find other beaches that have a lot of critters, but in the Silurian in West Virginia, we find more and more evidence that it was pretty saline. And the conditions just were not good for critters. This is early Silurian. If you go to New York and New Jersey, there is another sandstone of Silurian age. It's called the Shewangunk. In New Jersey, it's a tough old rock just like it is in West Virginia when it's cemented with silica. In New Jersey, it creates the highest point in the entire state. So of course, what state park did New Jersey name it? High Point State Park. That's what New Jerseyans would do. It's the high point, High Point State Park, right across the river. Here, the fossils in the Shewangunk are Silurian but they're more towards middle Silurian in age because the beach migrated and therefore, it's all Silurian. But sea level was rising onto the continent and the beach followed sea level. That makes sense; it's the environment. Where the water was deeper in West Virginia when the beach was in New York, what was happening in sedimentation in West Virginia? It was deeper water. Muds washed off the continent. Clastic materials that were finer grained were being deposited. Eventually, we got limestones. It became clear it was far enough offshore, shallower water, a type of basin, and as you go further out from those muds, you can get the carbonates.

Deb: When you say offshore, is this water coming from the east or is this water coming from the west?

Dr. Bob: Well, I didn't really say that. It could be from the south and east.

Deb: This gets a little confusing because many people think of our Atlantic Ocean, and they may be thinking that when you're saying deeper water, shallower water.

Dr. Bob: It is a continental shelf but it is the continent of Lorencia. It is not yet the continental form of North America as we know it, because the North American coast is yet to develop because in the Silurian, where are the continents? They're still apart aren't they? They have yet to come together. So the coastline isn't anything like a coastline form. I'm just using those specific geographic locations that we know of today because we can follow that. So it's more of a sea moving up from the south and east to the north and west. We can find Silurian-age rocks all through the mid-continent area, and changes in the Silurian-age rocks, clastics and so forth even into Wisconsin. It was a different type of environment in Wisconsin because whereas the Paleozoic section in West Virginia is measured in terms of 20 to 25 thousand feet of accumulation, the Paleozoic section, if it were present and much of it is eroded off, scrubbed off the top, would be orders of magnitude less--maybe 2,000, 2,500 feet rather than 22,000 or 25,000 feet. In order of magnitude, power of 10 less. Why? Because that was a broader cratonic or craton, a word we introduced last show, interior. The water was very thin up there. It never got to great depths. Furthermore, because where we are in West Virginia, great accumulations of sediments were occurring onto this shelf. What would any self-respecting shelf do as it gets loaded with more and more debris? It would sink, which opens it up for more and more debris to wash in. We come to that in the context of what is broadly happening in the Paleozoic.

Let's leave fossils now for a moment and talk about the whole Paleozoic in the terms of these continents that are apart: Lorencia, Siberia, and Baltica. They're going to start coming together, not all at one time with a uniform rate. Fits and starts of this. Closures begin. So what you need to do is you have a sheet like this that is the geologic time scale for West Virginia. Now we're going to superimpose on that from the cartoons in your textbooks some critical components. If you don't have that with you, don't worry. Just build a little bracket separately in your notes, and say Paleozoic. Just bracket the Paleozoic with Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, Permian. Then, what I want you to do is look at the book, and again this is page 343, look at the right-hand side of the page, and there's a critical term here. It's the Taconic Orogeny. It is the first defined orogeny in North America in the Paleozoic since the Grenville event. It's been a long time in coming. It is described and named for the Taconic Mountains in New York. The Taconic Mountains are right along the western margin of Vermont. The Champlain Valley is to the west, and then if you travel further west, you come into the Adirondacks. But the Taconic Mountains in that region provided early geologists with a history and a story to tell. The earlier rocks were folded. They were broken. It's hard to find the Taconic in the rock history, but notice when it occurred. If you go to the adjacent page, the Taconic, you cross it over here, is in the middle Ordovician. If mountains are going to build, what's going to happen to the eroded material. You build mountains in Vermont, New Hampshire, in that area, and they are going to be a source for sediment. Where's that sediment going to go? Out to the west and down to the south and west into West Virginia. So that there is a rock formation, if you happen to have that yellow sheet with you, that is characterized by mud. After a long long period of carbonate shelf and shelf environment with the shelf sinking under the weight, suddenly there is a dominance of clastic, couple thousand feet of clastic mud, and it's named for a town in the eastern panhandle. The formation is the Martinsburg formation. It is not now a mud. As a matter of fact, it doesn't even look like a sedimentary mudstone. It looks like it's been cooked a little bit as it has been. But it's still a shale. It is still the Martinsburg shale. It hasn't been metamorphosed.

So the Taconic Orogeny created the deposition of mud in West Virginia, but what do you think would be between the mud in West Virginia that was deposited in deeper water and the mountains in New Hampshire? What do you think you'd find somewhere in northeastern Pennsylvania, or should find? You should find a delta, and you do. You do indeed find the delta in those regions. You say, whoa, that makes sense. A delta accumulates so rapidly, what does it do to the crust? It weighs it down. Farther out to sea, the deposits take a longer time to build a foot of deposits. The deposits are thinner overall in the thicker part of the delta. That was the Ordovician. That's the first phase of the building of the Appalachians.

Turn then to the next package, and the next package you will find on page 370. That starts with the Silurian and then the Devonian, the lower Devonian. Now there's another big orogeny, the Acadian. An orogeny is a fancy word for mountain building. The Acadian Mountains--it's an old name for that part of New England. However, we also find events because of emplacements of granite and intrusion in the Carolinas. The delta that formed in New York and Pennsylvania was enormously thick. Today you'd find that in the Catskill Mountains, so the geologists called it the Catskill Delta.

Then if you move further on to page 400, you find the last major mountain building that took place in the Carboniferous and the Permian, and that's the Allegheny Orogeny, and it's kind of interesting, and that is where the West Virginia scene is.

Now we have tried to present the first overview. The first look at the Paleozoic. Next time, which is our last time, we will emphasize again West Virginia and the Paleozoic. We'll talk a bit about land plants. And we'll talk about life forms. Then we'll talk about the Mesozoic and the dinosaurs, and talk about the Cenozoic in general. More in general because we don't have it in West Virginia. Until then, take care!

WVGES Education Specialist, Tom Repine (repine@wvgs.wvnet.edu)

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