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The stream at the top of Kaaterskill Falls 2-9-17

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Top of the falls, bottom of the river

Windows through time

Robert Titus

 

Kaaterskill Falls is one of the scenic centerpieces of the Catskills. To stand atop these falls and to gaze out at the gorge below is a grand Catskills experience. The stream which makes the falls can, at times, be a powerful flow. This is the creek that drains North and South Lakes so it witnesses a lot of water flowing by. Sometimes it is a thunderous and very loud flow that tumbles over the falls. That adds to the experience. People have been coming here for almost two centuries now. Many have left the names or initials carved in the rocks here. The oldest inscription in the rocks that I have seen carries the date of 1810. Thomas Cole did some of his early work here.

But I am a geologist and when I am at the top of the falls, which is often, I see inscriptions that Nature herself has left here. And these are a lot older, hundreds of millions of years older. I know how to read those inscriptions even though they are not in English.  And when I read the rocks I see into them. I see not just one stream here but two. And both of those streams are flowing in the same direction and their two channels are almost identical in size. Left banks match left banks; right banks match right banks. But that second stream is as old as the rocks themselves, perhaps 375 million years old. You might dismiss my observations as tainted by hallucinations but I am quite literal in what I report to you. There are two streams there. Let me explain.

If you visit the top of Kaaterskill Falls please notice the rock ledge that rises above the modern flow of water. Notice the stratification within those rocks. Beds of sandstone lay there, all of them inclined in the direction of the falls. These sandstone beds and their patterns of stratification make what is called planar cross bedding. That is a sedimentary feature which we associate with the channels of rivers. Essentially, these strata were part of a sand dune which formed within the channel of the old stream and grew with time as it also migrated down the stream.

Aha! Now you too can see my second stream; it is composed of rock. Planar cross stratification occurs when powerful river currents are sweeping sand along in a downstream direction. As long as the current stays strong the sand will continue on its journey. But, just as the current is starting to slow down which has to occur eventually, then deposition begins. The sand slows down too and that dune begins to form and then it grows one stratum at a time. That growth continues the dunes migration as it is now growing in a downstream direction. Look carefully and that is what you can see here. Those strata of rock are inclined to the right which is roughly to the southwest. That’s the direction that the old stream was flowing. And, it is also roughly the direction that the modern stream is flowing.

What happened to that sand and its dune is that it finally stopped advancing downstream and never moved again. The stream was probably diverted to a new path, rivers do that. Then, with time, the sands came to be buried under so much more sediment that they were hardened into rocks. This became a petrified dune in a petrified streambed.

And so it is that I really do see two streams here. One is modern, the other is very ancient. Both display the same direction of flow, to the southwest. It is so odd to see two streams, so similar to each other but separately by hundreds of millions of years. But it is the nature of my science of geology to discover such things.

   Kaaterskill Falls is a wondrous place, but it can be a dangerous place too; a number of people have fallen to their deaths at Kaaterskill Falls, you must be careful there. Wait for dry and warm times before you visit. Contact the author at titusr@hartwick.edu  or visit the facebook page “The Catskill Geologist.”

Tilted strata 2-2-17

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Tilted Strata

Windows Through Time

Robert Titus

 

This column is focused on allowing you to see things that have always been right there in front of you. That’s something we geologists are good at. We travel to outcroppings of rock and look into them and see things that we never saw before. We survey landscapes and find meanings in them that we could never before have perceived. That is the nature of a geologist’s life; we are always looking through those windows through time and we are always seeing such wondrous visions, visions of the past.

Let’s take a drive down Rte. 23 near Leeds and see what we can see. Where Rte. 23B enters onto Rte. 23 there is a very fine outcrop. The strata here are of the Helderberg Limestone. This is pretty much the same rock sequence that makes up the cliff at John Boyd Thacher State Park. It is limestone and that means it formed at the bottom of a very shallow tropical sea. I can’t drive past these rocks without seeing images of the Bahamas. I find myself snorkeling in that beautiful sea.

                 Tilted strata along Rte. 23 near Leeds.

   But there is something else, and you have to look twice and think about it before you take notice. All those strata are tilted.  Take a look at my picture. Those strata tilt steeply to the right. That’s just exactly the sort of thing that people don’t normally notice. You do have to think about it to appreciate it. Strata form, originally, on the flat bottoms of the ocean. The seafloor never dips on one direction steeply as we see here. Something must have happened to these rocks.

Geologists recognize a concept called the “principle of original horizontality.” Simply stated that means that seafloors are flat and, because of that, strata accumulating upon them must also be flat. But what if they aren’t? Then we have to figure out what happened to them. Tilting is a good word, a verb which implies that the once flat strata have come to be tilted from the horizontal. But how on earth could that have happened?  Stop and think about it. Those rocks are heavy, very heavy. How could they have ever have become tilted. One end of the outcrop must have been lifted, and how on earth can such a thing happen?

Now you see what is happening. We have stopped and actually looked at an outcrop and all of a sudden we have a lot of very interesting questions. It was about 300 years ago that early geologists first paid attention to this sort of thing and you can just imagine how perplexed they must have been. What could have caused such phenomena? Back then, they could not even guess.

Today, it’s different. We have scientific theories to explain such things. Today we understand a lot about what is called mountain building. We can look to the east and we recognize that once, long ago, something collided with North America. That collision squeezed the rocks throughout what we call the Appalachian realm. The compressed rocks acted like the folds of an accordion; they were squeezed and deformed just as an accordion is.  A lot of that deformation consisted of simple tilting of the sort we see here.

That something that collided with North America was essentially a very large portion of Europe. Just as India is, today, colliding with Asia, once Europe collided with North America. When you stop and think about that, then you can appreciate that this sort of thing is capable of lifting and tilting such enormous masses of rock. This is big time geology. This is mountain building and that makes it important.

But, you might ask, where are those mountains? The answer to that question makes this outcrop still more interesting. Look up into the air above it – thousands of feet up – actually a mile or so. There used to be mountains up there; they have all eroded away.

Now it is fitting to take a few steps back and look, now more deeply, into this outcropping. Using your mind’s eye you can see the aqua colored waters of an ancient tropical sea. Then you watch as thousands of feet of sediment pile up upon this site. Slowly those sediments petrify; they become brittle masses of rock. Then, the ground starts lurching and rising to form a great range of mountains. The old ocean quickly drains away. Those mountains reach great elevations and tower above the horizon. Now wrenching motions are contorting the strata within; this is the chapter which witnesses the tilting we first came here to ponder.

Then all becomes silent; the mountain building is over. For millions upon millions of years the old mountains slowly decompose; they weather and erode away. Eventually, they build a highway here.

Contact the author at titusr@hartwick.edu or find visit his facebook page “The Catskill Geologist.”

 

Seeing a lake that is not there. 1-26-17

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Lake Front Property

Windows Through Time

Robert Titus

June 24, 2010

 

 

Intersection of Rtes. 32 and 23A

When you have been a geologist for a long time you develop a real sense for the landscape; you gain insight and you just plain notice things that others don’t. With age and experience, you become an increasingly effective observer in the field. In many sciences it is the very young who do the best work. In my science, however, the most seasoned eye often sees the most and the best.

There is one thing, however, that even the most experienced eye finds difficult, and that is seeing what is not there. That happens when Nature has painted a landscape but left something out. If you can notice the absence, you may be awakened to some wonderful moment in the geological past. But, just how do you see what is not there? Well, as I said, it comes with age and experience. And for you that starts right now; give me just a few minutes.

Let’s go to the intersection of State Routes 32 and 23A, just east of Palenville. Look to the northeast and see what you don’t see. There is a fine agricultural field, but what else can you see? The answer is not much. There are no canyons, rivers, no hills nor dales. In fact, there is just about nothing there. I have been by there many a time and I have long noticed that I wasn’t noticing much in the way of real landscape, just a lot of flatness. Well, all along, I did have some interesting ideas. I finally looked it all up in the geological literature and confirmed what I had suspected all along.

This broad flat landscape, so well suited for the farmer’s plow, is sometimes known as the “Kiskatom Flats.” As I expected, the flats mark the floor of an Ice Age lake. The story of this lake takes us back to about 13,000 years ago when warming climates were bringing the late Ice Age to a fitful end. At that moment the Kiskatom flats were something you might call a glacial battlefield. The ice had, earlier, retreated halfway to Albany. Then the climate cooled briefly and the ice re-advanced to the southern end of these flats. That readvance was temporary, and the ice was once again melting away, this time for good.

As the ice left the area, a landscape depression was left behind. With all the meltwater that is produced by retreating ice, this depression filled up quickly and hence the origin of Glacial Lake Kiskatom. The lake waters rose to an elevation of about 360 feet, and my guess is that it was four miles long, north to south, and one mile wide, east to west.

It must have been quite a sight. On its northern shore there was still a great glacier, rising perhaps a few hundred feet above the lake waters. All along the eastern shore there was likely an equally thick glacier. This was the end of the Ice Age and the temperatures were quite warm. All of the ice was actively melting and vast volumes of meltwater were pouring out of the valley glacier. Imagine thundering cascades of raging foaming white water plunging into the lake.

These glaciers were not melting so much as they were disintegrating. From time to time, enormous masses of ice would have detached and crashed down into the lake, breaking into numerous small icebergs. Believe it or not, huge tidal waves would soon have rippled back and forth across the little lake; such things do occur in small lakes.

But what about that flat landscape? These are common throughout the Hudson Valley and into the valleys of the Catskills. As a veteran geologist, I am always on the lookout for them. It has been my experience that these almost always mark the locations of other old glacial lakes. What happens is that the meltwater is dirty with sediment which quickly accumulates as flat stratified sheets on the floor of the lake. Much later, after all of the water has drained away, the flat lake bottom becomes a wetland which slowly dries out into a flat field. The northeast corner of Kiskatom Flats is still a wetland.

There are similar flats along the eastern banks of the Hudson River, that’s Glacial Lake Albany. There is another large flat area in the Schoharie Creek Valley, that’s Glacial Lake Schoharie. And there are more; you can start watching for them. Having just spent five minutes reading this article, you are more experienced and have a better trained eye. It’s time for you to start noticing such things. Go to Kiskatom Flats and see the lake with its bergs, look at the glaciers to the north and east and watch the raging cascades of water. You are seeing what is not there!

Reach the author at titusr@hartwick.edu or find his facebook page “The Catskill Geologist.”

Kaaterskill Clove from the air 1-19-17

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Kaaterskill Clove by air

Windows Through Time

Robert Titus

Columbia-Greene Media, Dec. 31, 2009

 

Recently this blog visited Hyde Park and found that the whole town is a heap of ice age sediment which was deposited as two deltas within Glacial Lake Albany by an ancient version of Crum Elbow Creek, the stream that flows right through the Vanderbilt Estate in the middle of town. This week, let’s visit something very much akin to this on the other side of the Hudson Valley.

Let’s visit the town of Palenville, which is found at the very base of Kaaterskill Clove. Recently, I had the chance to do it by air. My wife and I live next to the Freehold Airport operated, by the Nutmeg Soaring Association, a glider club. I managed to bum a ride into the Catskills. You can see a lot up there and much of it is invisible from the ground.

Kaaterskill Clove with Palenville alluvial fan  below it.

 

Palenville is one of those Catskill towns with an extensive historical heritage. It has been a place where visitors have long begun their ascent into scenic Kaaterskill Clove. Originally a tough trek, nowadays there is a modern highway so the journey is easy. In the 19th Century Palenville became an artist’s colony. Artists of the famed Hudson Valley School of art commonly spent their summers there and devoted themselves to sketching and painting the area’s scenic landscape.  A lot of very good work was done in the vicinity of the clove. Palenville has always seen a great number of tourists passing through on their ways to the mountains. Today hikers frequent the town.

Geologists have long been drawn to Kaaterskill clove to view its landscape with a more scientific eye. That’s where I fit in to the story.  I love to hike the clove and the mountains north and south of it. There is an awful lot of very good geology to be seen here. So, when I got the chance to fly over it, I welcomed the opportunity. I had a pretty good idea of what I would see and I looked forward to it. Kaaterskill Clove is a great gash in the Catskill Front. Most of it was carved during the Ice Age, especially during the closing phases of that time. Melting glaciers provided enormous amounts of water that cascaded down the canyon, eroding it. Think of it as an oversized gulley!

Kaaterskill Clove had been there before our most recent ice age. It probably began eroding at the end of a previous ice age chapter. But about 13,000 or 14,000 thousand years ago there was another time of melting . . . and another time of erosion. You have to visit the clove and imagine it with deafening masses of raging, foaming, pounding whitewater thundering down its canyon. Erosion would have been going on at an alarming rate.

Where there is erosion, the destruction of rock, then there must also be the production of equally large masses of sediment.  Rock is converted into sediment on a nearly one-to-one basis. The newly formed sediment must be deposited somewhere. That is exactly what I was going to see.

Palenville has long been recognized as something that is called an “alluvial fan.” That is a large, fan-shaped heap of earth. The earth of an alluvial fan spreads out across a dry valley floor at the bottom of the sediment’s source. In this case, large amounts of sediment traveled down an eroding Kaaterskill Clove and then spread out into a fan shape heap at the bottom of that clove.  There was no ice age lake in Palenville so no delta formed here as did at Hyde Park and that is why an alluvial fan is different. It has no flat top as does a delta; it is all slow, gentle slopes.

Map of Palenville alluvial fan.

A trained geologist can recognize such a feature on any good topographical map, and I did this a long time ago. But now, I was up in a plane, and there it was.  As we flew by I gazed into the great wide yawning clove. And spread out before it was the alluvial fan.  I could recognize three roads that I knew. These were Bogart Road, Rt. 23A, and Rt. 32A. The three of them radiated out from the bottom of the canyon and spread out across the top of the fan. Nobody knew it at the time but as laid out those roads all descend the gentle slopes of the alluvial fan.

So, in recent months we have visited two piles of sand, both deposited at the end of the Ice Age. Each fostered the appearance of a town. It is strange how often we humans live upon ice age sediments. It happened so long ago, but it reaches forward through time to affect us. Reach the author at titusr@hartwick.edu and see more at our facebook page “The Catskill Geologist”

 

 

 

 

A visit to a drumlin field 1-12-17

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Drumlins: pretty little hills

Windows Through Time

Robert Titus

Sept. 10, 2010 in Columbia Greene Media

 

I would like to introduce you to a new geological topic today, one which is very important throughout the Hudson Valley. That is the drumlin. Drumlin is a Gaelic work for hill, but these are very special hills with very special origins. Hills come in all shapes and sizes; they are found everywhere. What makes a drumlin different is its particular shape and the particular type of place where it is found.

A drumlin is said to have the shape of an upside down spoon bowl, so we can start by having you take out a typical spoon, turning it over, and looking at it from what would normally be below. You will see a very nice symmetrical oval shape to the spoon bowl. It is wider at the handle end and tapers to a narrow front. Now turn your spoon sideways, but still upside down and look at it from this angle. The handle end is steep but the angle, again, tapers towards the front.

       A teaspoon bowl, shaped like an upside down drumlin.

   These are exactly the forms we see in a drumlin; you just have to scale it all up in size  . . . a lot. Drumlins can be a mile long, up to 150 feet in height and they can be more than 1,500 feet wide. Most are a good bit smaller, but they are large. They are like potato chips; you can’t just have one. It is very unusual to just see one of them; typically they occur in drumlin fields where they can number in the scores and sometimes many more. And those drumlins fields are, as I said, only found in particular landscapes: areas that had been glaciated.

 

                                                                    A drumlin field, arrows show direction of glacial movement.

Drumlins display compass directions and those directions speak to us of their origins. Typically drumlins are parallel to each other, and parallel to the long ago flow of the glaciers that formed them. In the Hudson Valley they are commonly oriented north to south.

But how, exactly, did the glaciers form them? Late at night, in geology bars, that issue has been debated for decades. It is not easy to describe the origins of drumlins without using the word sculpting. It would seem that glaciers pass across large masses of coarse glacial sediment and sculpt those materials into the forms we see, but more explanation is needed. The big problem is that nobody has ever been to the bottom of a glacier that was sculpting a drumlin so we can’t go and observe the process.

It may be that drumlins formed late in the Ice Age, when the climate had been warming up. Water would melt out of the glacier and soak into the sediments below. That would make them soft and very pliable and speed up the sculpting process. But, again, nobody has been there to see this happen.

But, for our purposes, something that is very important is that drumlins are scenic and make for very nice landscape. Recognizing them is important to appreciating our Hudson Valley landscapes. You need to see one.

We will, in the future, visit a lot of drumlins and a number of drumlin fields, but today I would like to just recommend a visit to just one, a good one. That would be in the Hudson Valley Hamlet of Viewmonte, along the northern edge of Clermont. Take Rte. 9G south from the Rip Van Winkle Bridge about five miles. Watch on the left (east) for Cemetery Road. Take that left and, less than a mile down the road, you will see a cemetery on the right. If you are not careful you will pass by its inconspicuous entrance so watch it. Drive up that narrow driveway. You have not only entered a cemetery, but you have entered onto a drumlin and a very good one. You are driving up the north end of the hill and this is the steep side. When you reach the top, you will appreciate just how symmetrical a drumlin can be, Steep, but very smooth slopes, form the two, east and west, sides of the drumlin. At the back of the cemetery the driveway forms a turnaround and there you have reached the tapered downstream end of the hill.

                                                                          The top of the cemetery drumlin at Viewmonte

This is a very good drumlin; it has all the morphology that you would expect to see. Being a graveyard, the landscape has been kept open; there are few trees or shrubs to block the view. So this is a very good “introductory” drumlin. We will, in the future, see many more and we will learn about drumlin fields and see what they have to tell us about the ice age history of our region. They, if fact, have much to say.

Contact the author at titusr@hartwick.edu or visit his facebook page ’The Catskill Geologist.”

A moment on the bottom of an ancient sea floor. 1-5-17

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A few moments in time

Windows Through Time

Robert Titus

 

Like many paleontologists, I can well remember the first time I visited a dinosaur. My parents took me to the American Museum of Natural History in New York. There was the magnificent full skeleton of a Brontosaurus. I can remember looking up at it. I was about seven, so that beast looked pretty big to me. So too did a nearby Tyrannosaurus. It’s an experience that helped lead me, like many other youngsters, to a career in the study of fossils.

 

Every child should have a moment like this. But as an adult, I am often more impressed by things other than size. I am more philosophical now. Time means more to me now than back then; after all, I have known so much more of it. And one type of fossil that impresses me the most is called the trace fossil. That’s something you might well not be familiar with so let me explain. Most fossils, such as those towering dinosaur skeletons, are body fossils; they preserve parts of the original creatures. They are bones, shells or teeth and have lasted so long because they are composed of resilient materials. They are great fossils, but not the only kinds we see.

Trace fossils are different; these preserve the activities of ancient organisms. You can be forgiven if you ask how activities can be preserved in rocks. It does not seem intuitive, does it? But let’s begin with the best known of the trace fossils: the dinosaur footprints. They illustrate what I have in mind. The sizable three toed footprints of dinosaurs are actually quite common. The old monsters walked around in mud and left footprints which eventually petrified to make the most wonderful fossils. Walking is an activity and so these are trace fossils. There are quite a few locations where these can be seen in the Connecticut River Valley of Connecticut and Massachusetts. Someday I will describe one of them for you to go visit.

Dinosaur footprints from the Connecticut River Valley

 

But, what I have in mind are the traces of creatures that are a lot more modest. These fossils are so humble that they don’t even have a proper name. These are the traces of animals that burrowed across marine sediments almost 400 million years ago when our region was beneath the waves of the ancient Catskill Sea.

Take a look at my illustration and see what I am talking about. This is a slab of local sandstone. It is from near the top of an outcrop that lies along Rte. 23, just east of Five Mile Woods Road, just east of the town of Cairo. That outcrop was overrun by a glacier back during the Ice Age, and that glacier polished this surface, bringing those traces into sharp detail. This sandstone was once lying upon the bottom of the sea and that seafloor was alive with living creatures. Often I see the shells of ancient invertebrates on such sandstones, and a number of such fossils have been found at this outcrop.

            The burrows on Rte. 23

Notice the back and forth motion displayed with these traces. Some sort of creature was moving in this fashion, probably right on the floor of the old sea. There is a series of small “wiggles” inside of the larger ones (the third photo). This is pretty complex behavior from what must have been small and simple animals. These lines are the traces. Once, long ago, some sort of a simple invertebrate animal was mucking about across the sediment at the bottom of that sea. Today, lot’s of animals live in this sort of habitat. They dig across the mud. They actually travel, and in so doing, they leave their burrow traces behind.

Close up of same burrows

What kind of animal was it? I don’t know. If you force me to answer the question I would first guess that it was some sort of a worm, but I really don’t know. Some of our readers have observed snails producing these sort of movements. Where was this creature going? Here I can only guess that it was just wandering and it did not know itself where it was going. Worms and snails don’t carry maps you know; they have no idea where they are going.

What was this creature doing? Here I can come up with a reasonable answer: it was very likely looking for food. That’s the motivation for a lot of animal activity. It is even possible that, if it was a worm, then it was eating the very mud it was digging through. Modern earthworms do that and there is no reason to suppose and ancient worms did not. Snails make these motions as they scrape algae off of the sea floor.

In the end, however, what is so remarkable about this fossil is how ordinary it is. This is not the skeleton of a towering dinosaur; it only records the very existence of a humble invertebrate animal; there was nothing remarkable about what that creature was doing. It was simply going about its daily routine on the floor of an ancient sea. It is the extraordinarily everyday nature of this that makes it of note. When we look at this fossil we are sharing a few minutes or so in the life of an invertebrate animal. I find that astonishing. Contact the author at titusr@hartwick.edu or find more at the facebook page “The Catskill Geologist.”

 

A deep sea landslide along the Mohawk River 12-29-16

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Our reader’s rocks: the submarine avalanche

Windows Through Time

Robert Titus

 

   Dear Professor Titus: I found this peculiar looking rock at my son’s new home. This rock came from an outcropping along the Mohawk River near the Twin Bridges of the Northway. What are the markings on the surface? What can you tell me about them? Mrs. Deborah Teator, Greenville.

Dear Mrs. Teator: Yes, this is a very interesting rock and I can tell you a great deal about it. The state geological map indicates that your rock is from the Normanskill Formation and that is a unit that I have been meaning to write about anyway so I am glad that you asked about it. The Normanskill makes up much of the bedrock in the Hudson Valley and it is a very important unit of rock in that region. It has quite a story to tell, when you look through a window of time.

The rock is a very dark type of sandstone which is called graywacke. We geologists sometimes call it “dirty sandstone.” The “dirt” is a large amount of silt and clay which is mixed with the sand. Graywacke is a special type of sandstone which generally forms in a special type of environment. That is the bottom of a great marine trench.

If you know your way around the bottom of the Pacific then you will know what a marine trench is. If not, take a look at most any globe and find the dark blue stretches out there in the middle of the Pacific. The best one is the Marianas Trench, adjacent to the Marianas Islands. A trench is just what it sounds like; it is a long deep crease in the floor of the ocean. I am not kidding about the deep part; the Marianas Trench is about 36,000 feet deep, deeper than Mt. Everest is tall!

The slopes of a trench are, not surprisingly, very steep. Because of that, the soft sediments that accumulate on those slopes are very unstable. If anything jars those slopes, then it triggers a submarine avalanche. Great masses of sediment are kicked up into big smoky looking plumes of dirty water.  These sediment laden plumes are denser than surrounding seawater and thus they, slowly at first, start moving downhill into the depths. These “density currents’ soon pick up a lot of speed and they become submarine avalanches. These are, like their snowy counterparts on land, very dramatic events and they reach speeds of 30 to 50 miles an hour.

They can be destructive events as well, just like the ones on land. These fast moving masses of dirty water are very erosive. They sweep across the muddy deepwater slopes and pick up more sediment and carry it away. That makes the current bigger, heavier and even more powerful. Eventually these avalanches reach the bottom of the trench and the slope flattens out. That’s when the currents slow down and, with time, come to a rest. That is also when the sediment is deposited. The event has a technical term; it is called turbidity current. The resulting sedimentary deposit is called a turbidite.

Toward the end, when the masses of dirty water are slowing down, they press into the soft sticky mud below, and they create some very recognizable features. These are called sole marks and it is sole marks that adorn the surface of Deborah Teator’s rock. What I am saying is that this is a “petrified avalanche!” That might, at first, seem impossible, but my description is of something that marine geologists have observed in the modern Atlantic Ocean. We simply know that these things happen.

So, all this speaks volumes about the Twin Bridges vicinity. Back in time, during the Ordovician Period, about 450 million years ago, this was a very different place. This was a deep marine trench. How deep? I don’t know but 20,000 feet seems reasonable. It was a very quiet, very dark seafloor. But, every once in a while, an awful catastrophic submarine avalanche swept by. After it was over, things quieted down again. The next time you are crossing the Twin Bridges, please remember to think about all this. It really rearranges your sense of reality. Doesn’t it?

Do you have an interesting rock, an interesting outcrop or some puzzling landscape feature? Then e-mail the author at titusr@hartwick.edu or write him at Dept. Geology, Hartwick College, Oneonta, NY, 13820. Send photos if you can.

A sinking Catskill Delta 12-22-16

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Time in Winter, part three

Windows Through Time

Robert Titus

 

The outcrop on Rte. 23. Dark stratum in middle marks boundary between 2nd and 3rd cycles.

 

We have been philosophers, contemplating time itself these past few weeks. We’ve been gazing up at the Catskill Front. There, before us, were millions of years of history: petrified into the strata of the Catskills. Rip Van Winkle spent 20 years sleeping up there, but those rocks have slept for nearly 400 million. I’d like to take you up there to see those venerable lithologies, but it’s winter and not a very good time to climb up into the mountains. Fortunately, we won’t have to wait for spring; there is a better strategy.

The Catskill sequence, happily for us, begins in the Hudson Valley. You can go and see its strata, up close and right along the highway. No climbing is needed. Find your way to the intersection of Routes 32 and 23 near Cairo. Then travel just the shortest distance east on Rte. 23. There, alongside the west bound lane, is a fine outcropping of strata. These are mostly sandstones, but there is some shale as well. This is the Catskill sequence up close. These are virtually the same rocks that make up all of the Catskill Front. We have been gazing up at them, but here we can look them right in the eye.

And maybe it is time to stop being philosophers and start, once again, being geologists. Pause and survey the whole outcrop. You will, I hope, be able to see that it is broken up into three separate horizons of stratified rock. In other words there seem to be three “packages” of strata here, laid out, one atop the other, in a vertical sequence. As geologists, we always start at the oldest layers of rock and those are the ones at the bottom of the outcrop at its western end. That first package of strata is the least well exposed but let’s start there. You will see a sequence of thickly bedded, light colored sandstones. Above them the stratigraphy grades into finer grained, thinner bedded material. This has a greenish gray to brick red color.

 

Red strata at very bottom are overbank floodplain sediment. Gray sandstones, above, are river deposits. Notice some river strata dip to the right. These are typical river cross beds.

 

This stratigraphy is repeated in the next package and in the third. In other words we are looking at cyclical events in a cyclical stratigraphy. In the second package you can see that many of the thick sandstone strata are inclined to the west (left). This is typical of river channel sediments. Each of the three cycles begins with this sort of river channel sandstone. The overlying, finer grained materials are petrified soil profiles, literally fossil soils. So, if you follow all this, each cycle represents the presence of a Devonian age Catskill Delta river channel, overlain by a floodplain soil. And it happened three times.

So, what was going on here and how does it relate to an ancient delta? There were two sedimentary dynamics back in Catskill Delta days. First those ancient rivers were what we call meandering streams. They formed beautiful, sinuous channels that literally snaked back and forth across their delta floodplains. This process, called river meandering, is a very slow one but it is effective over time and it can still be seen in many modern rivers. But it is slow and that gets us to the second dynamic.

Remember, from those earlier columns, how the sediments of the Mississippi Delta are sinking and that the sinking is slow? Well, our Catskill Delta was sinking slowly too. Gradual river meandering was matched with slow crustal subsidence. The rivers had a back and forth motion. First the river would meander one way for quite a long time and then it would return. Meandering “back” was easy, but, by the time a river meandered “forth” the crust has already sunk quite a good bit. A new river channel/ floodplain “forth” sequence would be laid down on top of the old “back” one. If meandering continued, and it would, then a third horizon (cycle) would be deposited on the same subsiding delta.

That’s what deposited the three cycles we see on Rt. 23. Did one meandering river deposit all three cycles? I don’t know. Did one or several rivers meander across this site? I don’t know, but it doesn’t much matter. The important thing is that we can look into one outcrop and recognize very typical chapters in the history of the whole Catskill Delta. It was subsiding, its streams were meandering, and all of it behaved very much like the Mississippi Delta of today. The Devonian Catskill Delta was the virtual twin of today’s Louisiana; only time has changed. Now: look at the outcrop and then up at the mountains again and appreciate that these were the kinds of processes that formed all the rocks of all the Catskill Front.

Reach the author at titusr@hartwick.edu and find more at the facebook page “The Catskill Geologist.”

 

 

 

The Catskill Front in winter – Part two 12-15-16

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Time in winter, part II

Windows Through Time

Robert Titus

Feb. 11, 2010

 

Catskill Front in winter

 

Last week we drove along Rt. 32, pulled over to the side of the road and gazed up at the Catskill Front. We found that, at this time of the year, we could look through the leafless forests and see the rocks so clearly. We became philosophers as we contemplated the millions of years of geological history rising before us.

Let’s look into all this again, and this time let’s understand some of the mechanics of this passage of time. Our key to understanding the rocks comes from understanding the City of New Orleans! Does that surprise you? Read on.

Many of us learned a lot of geology when Hurricane Katrina struck. One of the most remarkable things was that most of New Orleans currently lies below sea level. How could that be? Were people idiots when the city was first founded? Of course not! Three centuries ago, when New Orleans was settled, it lay above sea level. During those centuries it has slowly sunk until now most of it is below sea level. It would have been flooded decades ago except for the construction of manmade levees.

Ironically, the levees may have caused more damage than they were worth. Obviously they weren’t up to the job when the hurricane struck; the city flooded anyway. But there was something else equally important. Floods bring sand down the river and deposit it, spread out across the delta top. That can’t happen if levees get in the way. New Orleans, being surrounded by levees, did not frequently experience flooding, but the city never received the sand that floods would have brought. The city continued to subside, but the sand, which would have kept it above sea level, never got there. That’s an irony!

My point here is that great deltas slowly subside under the weight of their own sediments. As thousands and then millions of years pass by, enormous thicknesses of sand and mud accumulate on them: first hundreds of feet and then thousands. That’s what we are looking at when we gaze up at the Catskill Front. Had there been a city of “Old Orleans” on the Catskill Delta, back during the Devonian time period, then this fossil city would still be up there – somewhere along the Catskill Front.  And it would likely be buried beneath many feet of sedimentary rock. What a strange thought!

But, this is science, and that is where the evidence leads us. When I look up there and see all those ledges of sand, I realize that these are the deposits of great flooding rivers. I see countless cities of Old Orleans and I see countless Hurricane Katrina’s. I go back into time and watch as the old Catskill Delta slowly subsides, and I see all that sediment piling up. Eventually all of these strata sink into the depths. Thousands of feet of new sediments bury the old. The weight of all this is stupendous. And given still more time, and a lot of it, these sediments begin to harden into rock.

Eons of time are now flying by in my mind’s eye and I am nowhere near the end of it. I still have to contemplate the erosion of the Catskill Front to create the wall of rock we see here. Only Nature can do that through the weathering of rock, turning it back into sediment and then the erosion of that sediment. Nature must be very patient. But for a person to stand along the side of the road, to look at the strata above, and see all this is a marvel. These are awesome notions; no wonder a geologist becomes philosophical.

But where did all that sand and mud come from? Now I must stop looking west at that ancient delta and I turn around to look to the eastern horizon. There, in front of me, is the ghostly silhouette of a long lost mountain range. It rises above today’s Taconic Mountains and it dwarfs those puny peaks. The sediments and the sedimentary rocks of the Catskills came from the weathering and erosion of that towering range of mountains, called the Acadians. These may have risen to elevations of about 30,000 feet. I instinctively look up, but they are not there . . . anymore.

 

   Profile of Acadian Mountains against profile of modern Catskills, Hudson Valley and Taconics

   I look east to west, then west to east. I see 30,000 feet of old mountains (east) having been converted into about 9,000 feet of modern Catskills (west). Old mountains were turned into new mountains. And Nature presents us with a cycle here. That conversion of old mountains to younger mountains will all probably happen again – and then again. It was the English naturalist James Hutton who first understood things such as this. He marveled about time, saying “We see no vestige of a beginning, no prospect of an end.” With his thoughts geology became a philosophical science. Reach the author at titusr@hartwick.edu  Find more at the facebook page “The Catskill Geologist.”

 

The Catskill Front in Winter – Part One – 12-8-16

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Looking at Time in Winter: Part One

Windows Through Time

Robert Titus

 

 

Winter is not always the best season to be a geologist. We do greatly prefer the warm months when we are better able to get out and explore. But there are some compensations. This is the season when, with all the leaves down, we can see so much that will be hidden come next summer. I have in mind a good look at the great Wall of Manitou, the Catskill Front. From numerous sites down in the Hudson Valley you can gaze up at this massive wall of sandstone and shale and see details that are usually hidden.

I stopped along the road down in Palenville and did exactly that, and I was soon able to wax poetic about one of my favorite topics in geology. That would be the enormous lengths of time that we see recorded in the strata. We geologists routinely travel back hundreds of millions years into “deep time.” Much of my own work involves Devonian age rocks which are mostly a bit less than 400 million years old. Much of the rest of my work takes me to ice age deposits which are a mere 15 to 20 thousand years old. We geologists get to be a little jaded with all this. What’s a couple of hundred million years in a universe that is more than 14 billion years old? Still, sometimes it is nice just to go and “look” at all that time. That’s what I did in Palenville.

If you get the chance, please do the same. Follow Rt. 32 and pull over someplace where you can get a good view of the Catskill Front. I picked just south of the intersection with Rt. 32B. Gaze up at wall of rock and really appreciate what is before you. There are about 2,000 feet of stratified rock up there and all of it was, originally, sediment. The strata that you can see clearly are layers of sandstone; they make up those many horizontal strata. That’s sturdy stuff and it has held up well in the face of eons of weathering and erosion.

What you can’t see is what lies in between the sandstone ledges. That would be mostly red shale. Shale was mud to begin with and that makes it pretty soft stuff. Nature has little trouble with shale; she likes to erode it away and she is good at that, turning it into soil. So you rarely get to see shale in steep slopes like this. They are there, but they are buried in their own soils.

So, we have a pattern here. There appear to be countless horizons of sandstone, interbedded with equally countless horizons of shale. All were once soft sediments. Layers of sand alternated with layers of mud. And there before us are about 2,000 feet of all this, all deposited one stratum at a time. How long did it take? Well, that’s my main point today: it took a very long length of time!

Geologists estimate that the Devonian time period stretched from 419 to 359 million years ago. What we are looking at here is perhaps about a fifth of the whole. That suggests that what we are looking at are about 11 million years. My estimate is very rough so I will ask you pay it little heed. But we are certainly dealing with millions of years of time, and in Palenville you are looking at all of them.

For all of those millions of years our region witnessed the steady accumulation of layers of sand and layers of mud. Many of these sediments are red and that indicates that they were terrestrial in origin. The red is the mineral hematite and that forms only on land. The sands accumulated in stream channels; the mud of the shale formed on floodplains. This was a great delta, called the Catskill Delta.

You stand along the road, you gaze up, and you are looking at the cross section of something akin to the Mississippi Delta. Imagine if some enormous creature could slice 2,000 feet into the southern reaches of the Mississippi delta. If that giant then peeled away the earth, it would expose a cross section of the sediments of that delta. Those sediments are probably all still soft; they have not yet hardened into rock. But, in every other respect, our slice of Louisiana would look exactly like what we see here.

I spoke of waxing poetic before, and I guess that a person can actually get that way when he contemplates such thoughts. I could have spoken of waxing philosophical and that might be appropriate. We geologists do find all of this very spiritual and maybe that is the best word of all. Reach the author at titusr@hartwick.edu  or at http://thecatskillgeologist.com

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