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Regression to a Mean 1-14-21

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Regression to the Mean

On the Rocks –

The Woodstock Times, June 17, 1999

Updated by Robert and Johanna Titus 

 

We live in a world where we are used to the idea of rising sea levels. During hurricane seasons, we expect to see the rising of the ocean’s waters and the flooding of coastal landscapes. We may not be comfortable with the idea of coastal erosion, but we do see it as the “norm.”

Few of us would recognize it, but this is a bias. We are comfortable with the notion of rising sea levels not because that actually is the norm but because we live in a world where the climate has been warming up ever since the end of the ice age. As the climate has warmed glaciers have melted, and meltwater has poured into the seas raising their levels worldwide.

There is, however, nothing actually inevitable about rising sea levels; it could be the other way around. Suppose that the climate was cooling down. Then ice would be forming, water would be withdrawn from the sea to make the ice and the sea levels of the world would be dropping. Throughout the length of Earth history, it must be that there have been as many times of dropping sea level as there were risings. Neither is favored over the long term.

A rising sea level is often called a transgression while a falling sea level is called a regression. Transgressing seas do leave coastal regions susceptible to storm flooding and damage. Such coasts are prone to erosion and, in fact, do erode away.

Regressive coasts are quite different; as the sea levels drop rivers bring sand and mud into the seas and pile them up. The coasts advance seaward. We call that progradation.

You and I are not likely to ever see a good regression, not unless there is a dramatic shift in the climate. So, we will never see a whole coastline prograding. But we can go back in time to eras when the seas were retreating and see the results in the rocks. From Woodstock, travel east on the Glasco Pike to Mt. Marion. There, where Plattekill Creek crosses the road, you will see a towering outcrop. It is mostly black shale. The rock was once black mud deposited in relatively deep waters of the Devonian seas, a little less than 400 million years ago.

The black shale is a fine-grained deposit of mud. Mud accumulates in very thin sheets at the bottom of a quiet sea. The sea was quiet because of the great depths. There were no currents, or tides or waves in the deep water. But look upwards; at the top of the exposure, you will see a number of thick-bedded strata. If you could get up there you would find that these are sandstones. Overall, the outcrop grades from shale to sandstone, from mud to sand. That’s the regressive sequence.

What was happening? At this time the Acadian Mountains, located where the Berkshires are today, were actively rising in a dramatic and important mountain building event called the Acadian Orogeny. As these mountains uplifted, they began to weather and erode. Large masses of rock were converted into even larger volumes of mud, sand and gravel. That’s the fate of weathering rock. Mountain streams transported all of this material as sediment into the adjacent sea. That’s us right here, Woodstock and the whole Hudson Valley region were under water. Marine currents sorted out all of the fine-grained muds and carried them far out to sea where they settled to the bottom as the black muds that hardened into our black shales.

But as mountain building continued gluts of coarse-grained sediment overwhelmed the muds and layers of sand began to pile up Thus, when this sediment hardened, we ended up with the shale to sandstone sequence. That’s a regression.

Go back westward on the Glasco Pike. You will soon encounter other outcrops. These are mostly more sandstones. At the top of the hill, you will even see the cross section of an old river channel. The regression had succeeded, it had transformed a sea into a land area. There should be one of those New York State historical markers up there. It should say “Here the Woodstock area rose out of the sea.” After all, that was an historical event.

Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.”

Glaciers of Echo Lake

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A visit to Echo Lake

On the Rocks – The Woodstock Times

June 10, 1999

Updated by Robert and Johanna Titus

 

The Catskills are rightfully known for their wonderful scenery. Our mountains abound in hidden green cloves with brown and red ledges towering above. Our hiking trails bring us into these secluded natural settings. They have an air of primeval mystery and our park system keeps them that way. Elsewhere around the globe, there are many very different types of mountain landscapes. About as different as you can get are the Alps: there is nothing hidden or secluded about those great peaks. They stand right in the center of Europe with their white mountaintops soaring above the surrounding lands with an in-your-face dominance of the horizons. No one would ever get the Alps mixed up with the Catskills; no one, that is, except a geologist.

Our image of the Catskills of 14,000 years ago has a great deal in common with what we see in the Alps of today. The emblem of today’s Swiss landscape is the Alpine glacier, often called a niche glacier or commonly as a cirque glacier. These form in bowl-shaped mountain depressions, called niches, where snow accumulates, piling up to great depths and hardening into the ice that then begins its flow downhill as a frozen stream. During times of cold climate Alpine glaciers advance into the valleys below; during warmer times they melt back and sometimes even disappear. Not surprisingly, they are very erosive phenomena and have done a lot to shape the Swiss terrains. In fact, we have a word for these special landscapes; we call them “Alpine” landscapes. Similarly, the local glaciers of our ice age did a great deal to form the Catskills as we know them today. If you want to truly understand your Catskill landscapes, you must know something of the Alps!

And that includes, right here in the Woodstock vicinity. Take the red trail almost to the top of Overlook Mountain and then turn north on the blue trail. In about another mile take the yellow trail off to the west. You will soon find yourself descending into one of those mysterious hidden Catskill cloves. At the bottom is a beautiful little pond called Echo Lake. That’s not one of those silly romantic sounding names picked by a housing developer, the lake is very aptly named. Clap your hands or shout abruptly and you will find out why.

 

 

Look around you and you will see that Echo Lake is nestled at the bottom of a grand natural amphitheater. Steep slopes rise above on three sides. The only gap is to the southwest, there the lake waters make their escape and flow into the upper Saw Kill. This type of amphitheater is known to geologists as an Alpine niche, a place where once a glacier got organized. We also call such a feature a cirque and it was within the Echo Lake cirque that the Saw Kill glacier accumulated and then began its slow downhill flow. Beyond Echo Lake the Saw Kill glacier flowed at least as far as Cooper Lake and probably much farther.

Cirques are common Alpine landscape features. The steep walls behind the ice are called the headwalls; They were eroded by the ice that was once present. As the ice began its downhill motion, it plucked blocks of rock loose and thus shaped the steep walls. Similarly, the passing ice scoured out the basins of the lakes; in Switzerland such basins are called tarn lakes. Echo Lake is perfectly typical of an Alpine cirque and that is what makes it such a remarkably attractive Alpine landscape feature.

Cirques are common phenomena throughout the Catskills, but we don’t know of any others as well developed as this one. How many others are here and where are they located? That has been a heatedly debated issue ever since the early part of the 20th Century when they were first recognized. Some geologists have argued that there are very many of them, perhaps scores. Others have argued that there are only a handful and that all the other supposed cirques are nothing more that stream erosion in the upper reaches of our mountains. We think that the Echo Lake cirque is a safe bet. It’s at the top of the Saw Kill glacier which is one of the best known and most widely recognized Alpine glaciers of the Catskills.

It’s a wonderful time of the year to visit Echo Lake, and when you go there please do enjoy our summer scenery. But also pause for a moment and try to imagine the snowy high peaks of Switzerland, for that is exactly what you are seeing here.

   Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.”

Puddingstone at North Lake 12-31-20

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Rock Pudding

On the Rocks – The Woodstock Timed

Aug 12, 1999

Updated by Robert and Johanna Titus 

 

As geologists we are, of course, very fond of rocks. We find the study of bedrock always interesting, often fascinating and occasionally even engrossing. But there are limits; they are, after all, just rocks, and rock is pretty commonplace stuff. But, occasionally, you will round a bend in the trail and be startled by some remarkable bedrock exposure. There are a couple of these on either side of Kaaterskill Clove. When we visit with groups of people, there is almost always someone who cries “whoa” in complete surprise. This remarkable rock is locally called puddingstone.

Go to North Lake State Park and take the blue trail north. That’s the escarpment trail and it is always worth the hike. As you head up the trail you will pass over the ledge at Artist Rock and then cut uphill and away from the escarpment for a bit. Eventually, you will pass left of, and then under a knob of rock called Sunset Rock. It is right there that you first encounter the puddingstone. The puddingstone ledge is up to 20 feet thick. It rises vertically above the trail, so it is quite imposing. But it is the composition of the rock that generates the excitement.

Puddingstone is known, formally, to geologists as conglomerate. That’s a rock composed almost entirely of pebbles. The pebbles are all cemented together, and the effect is to produce a visually stunning lithology. In this case there are a great number of cobbles mixed in with the pebbles so that enhances the visual impact.

But what exactly is a conglomerate? That is, how did this peculiar rock come into existence? The answer to those questions comes slowly with a close examination of the rock. First, notice that most all of these pebbles are nicely rounded. We say that they have been stream washed and rounded by abrasion during a time when they were carried down a river. But where did the stream come from?

 

Look carefully at the pebbles and cobbles and you will find that they are of all sorts of different types. The largest number are white pebbles of quartz. As you look carefully, you will find a number of other lithologies. Let’s skip a detailed analysis, but it is safe to say that the pebbles are heterogeneous, and they must have come from a place where the bedrock was equally heterogeneous. That was an old mountain range.

The unit of rock is called the Twilight Park Conglomerate. It’s named for a community, across Kaaterskill Clove, where some more nice exposures can be seen. The Twilight Park Conglomerate is part of the Catskill sequence. That’s sediment which washed out of the ancient Acadian Mountains during the Devonian time period. To the east those mountains once towered, perhaps as high as the Andes of today. Like all mountains, they suffered from weathering and erosion and slowly crumbled. During their destruction there were times when unusually large amounts of very coarse-grained material washed out of the mountains, traveling down steep mountain streams, and washing out onto the flat lands below. That’s what happened here.

Look east from Sunset Rock. Imagine blue and purple mountains rising before you. They are white at their peaks. Enormous heaps of brick red coarse sediment lap up onto the flanks of those mountains. Great pounding, roaring, white water mountain streams are cascading out of the mountains and their raging flows continue across those red sediments. The streams flow out onto a large flat delta plain and they slow down as they lose their slopes. It’s then that they lose their ability to transport gravel and they deposit the thick layers of pebbles. These streams wash back and forth and spread the gravel out in thick deposits. Tens of millions of years pass by and the gravels are slowly buried by a thick sequence of more sediment, mostly sand. It all gradually hardens into today’s Catskill sequence.

Those old mountains eroded away entirely, hundreds of millions of years ago. These puddingstones and their pebbles are part of what is left. That, we think, is fascinating.

Contact the authors at randjtitus@prodigy.net Join their facebook page “The Catskill Geologist.

Monsters in the Closet Dec. 24, 2020

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Monsters in the Closet

Stories in Stone -The Columbia County Independent

Feb. 2004

Updated by Robert and Johanna Titus

 

We don’t know what it is about this time of the year, but we seem to start finding silverfish around the house, especially in our closets. What attracts them? We don’t know; they are just bugs, who can explain them.

Well, in fact, they are not just bugs. If you have a problem with silverfish do what we did. Stop for a moment and take a good look at them. They are, in fact, something quite special. If you can, get one to slow down long enough to look at carefully, you will see something very interesting. That’s a tough thing to do as they love to scurry around very quickly and don’t like to stop to be looked at. We recommend some bug spray, after all, it is the interest of science (and a bug-free home). Anyway, once you get one to stop moving you will quickly see that they are not like other insects. They do have six legs as all good insects should, but that is about it. Silverfish do not have wings and most insects do have wings. That’s a very primitive trait among insects.

Once you get one to stop moving you can see what they look like. They might remind you of little scorpions, but that is superficial. They have a series of silver-colored scales running the length of their backs, hence the name silverfish. There are two bristly antennae up front and what looks like three more behind. That’s why they are sometimes called bristletails. They do have six legs as do all proper insects., but that’s about it. All in all, you don’t have to know much invertebrate zoology to tell that silverfish are very primitive insects, they just look it, and that’s why they are so special.

You see, silverfish belong to a very ancient and primitive group of insects. Most insects have wings, four of them in fact, but the silverfish have none at all. Nor do any of their ancestors; the lineage extends back to before insects evolved wings. And when we say extends back, we mean a long, long time. Silverfish date back to the Devonian time period. Around here that’s important as all of our local bedrock is Devonian in age. As luck would have it, most of our sedimentary rocks were deposited in a terrestrial setting, one where insects abounded. This was the Gilboa Forest of the Catskill Delta complex.

The land of Gilboa was, like any great delta, a morass of forests, lakes, ponds, swamps and rivers. It was tropical in climate and it must have been a lush environment, perfect for insects. And it is rich in fossils, including insects, not terribly different from silverfish.

Creatures like silverfish have a special place in the hearts of paleontologists. We call them “living fossils” and that’s a good term. They have evolved so slowly and so very little that they remain virtually unchanged from their ancient ancestors of nearly 400 million years ago.

Living fossils are like keyholes into the past. We can look at them and see creatures as existed in the ancient past. In this case silverfish speak to us of the early ancestry of insects. These are the insects that first lived on the lands of the distant past, long before they evolved an ability to fly, chirp, sting, ruin picnics, and all the other things that modern insects do. We paleontologists love to see living fossils; they give us a firsthand look at the past.

Some people are proud to be able to trace their ancestry back to the Mayflower. That gives their families a 400-year history in America. We guess that is nothing to sneer at, but silverfish can trace their American ancestry back 400 million years. It may be humbling to see in these bugs, and primitive bugs at that, such a blue-blooded heritage.

So why are these monsters of the past so common in our closets. Well, it happens to be that they love eating the starch that is found in paper. We took another look back into our closets and found old copies of the Independent. It would seem that our newspaper is not just food for the mind.

Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.”

A jawless fish 12-17-20

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Fishing Season

On the Rocks – the Woodstock Times

Apr. 1, 1999

Updated by Robert and Johanna Titus

 

Wave your arm around in a wide arc. It is passing through air, but it is passing through history as well. Wherever you are, so many things have gone before. Your arm is passing through space that was once occupied by the core of a mountain range, the depths of a sea, dense jungles, a sandy beach and many other things. In the future the space your arm passed through will similarly have many more, equally different manifestations. The seas will return and also mountains will rise here again. Time passes, and times change, and the Earth evolves. You just have to wait long enough, and these things happen.

It’s the same with plants and animals. Wave your arm and it passes through space once occupied by dinosaurs and trilobites and saber-tooth tigers. We share space with these creatures; we just don’t share their time. Each creature, humble or proud, gets its moment in time, passes this way and then fades away, only to be replaced at another moment by another creature.

All this is, of course, an introduction to this week’s topic. It’s, once again, fishing season. If you enjoy fishing in the Catskills, maybe you would like to know about some of the forms that were here long ago. Wave your arm through the air; it is passing through space once occupied by some of those primitive fish. The Catskill region has yielded a very large number of fossil fish from a critical time in fish evolution. Let’s talk about one of them: Its name is Cephalaspis. When we say primitive we are not kidding. It belongs to a group of fish among the oldest and least evolved of all the fossil fish. These are referred to as the jawless fish. As we are sure that you can guess, jawless fish lacked a lower jaw. They had very simple mouths but no teeth. In a fish-eat-fish world the lack of jaws and teeth is a real disadvantage but that’s the way it was back when they first appeared. The jawless fish were rather un-endowed in other categories as well. They had only the most rudimentary of fins, just one set located towards the front. Modern fish have two sets of paired fins and others located bottom and top. Thanks to all these fins modern fish have a lot of control over their swimming. But poor Cephalaspis couldn’t have been a very effective swimmer.

So how did Cephalaspis get along if it couldn’t swim well and had little or no bite? It was certainly not a predator. More likely these creatures were scavengers. They would have swum the ponds and sluggish rivers of the old Catskill delta complex in search of food that was already dead.

Cephalaspis was not without any skills. These fish had large and sturdy head shields. Those were broad bones that covered the top of their skulls, giving the animal some pretty good defenses. Within these head shields are the sockets of eyes and these fish must have had reasonably good vision. There was also a third opening called a pineal opening which was also light sensitive although its exact function is unknown. Then there are strange areas of the head shield which are interpreted as “fields” of sensory functions. Again, the exact functions are unknown.

Cephalaspis is a very rare fossil in our area. Some specimens have been reported from local marine sandstones, probably between the villages of Veteran and Unionville. It is not uncommon elsewhere, nor is it unimportant. Bones are far more common in Europe and in Canada. There, the skulls are often very well preserved, and we have learned quite a bit about early fish from the studies of these. But you will not catch one of these this spring. Cephalaspis has been extinct for more than 300 million years.

Contact the authors at randjtitus@prodigy.net. Join their facebookpage “The Catskill Geologist.” 

Late lakes Dec. 10, 2020

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Late Lakes

The WoodstockTimes

ON THE ROCKS Updated by Robert and Johanna Titus

 

It’s always so important to use just the right words. For example, there are all sorts of terms for small bodies of fresh water. One is a puddle. Puddles aren’t very big nor are they very deep. A pool is both bigger and deeper. But pools are smaller than ponds, and ponds are smaller than lakes and so on. Nobody knows exactly where to draw the lines, but there are differences, and you must always use the right words.

In the end, however, it is a somber fact that all these bodies of fresh water, big and small, are doomed. None of them will survive. Lakes become ponds, ponds become pools and pools become puddles. Eventually puddles disappear altogether. Again, nobody can draw sharp lines and you can never watch as a pond becomes a pool. The process is geologic and, thus always, too slow to see.

But there is one time of the year when the process speeds up enough so that we can go out and watch the destruction of a pond and this is that time. Late August is a time of dramatic growth of pond plants. Find a small pond in your area and give it a look. Quite likely, all around the edge, you will see a thick scum of algae. There’s quite a lot of biology going on in there right now especially among the algae. All summer long, algae population curves have been steadily and slowly rising. But in late August the population growth curve steepens – dramatically. Algae populations skyrocket, frighteningly. Not surprisingly, populations exceed what’s called the “carrying capacity” of the environment. Probably such materials as nitrogen, potassium and phosphorous run out. Then populations crash catastrophically. A population crash should be an awful event, but algae don’t care. Come next year their populations will resume the cycle and start rising again. All will be repeated next season.

It’s not just algae, there are plenty of pond plants rooted in the shallow waters. They are growing rapidly as well. All in all, the edge of a small pond is right now a fine place for plants and plant debris to accumulate. And a little later in the season, tree leaves will fall into the ponds and wind will blow them into the shore zone as well. Over the winter, the remains of dead vegetation sink to the bottom and become part of the sediment down there. That makes the sediment around the edge of a pond all the more fertile, more nitrogen, potassium and phosphorous. Next year more and more plants will participate in this seemingly endless cycle.

It is the nature of things for a floating mat of plant debris to develop around the edge of the pond and, with time, this mat expands outward toward the middle of the pond. Meanwhile the remaining clear waters, out there in the middle of the pond are becoming more fertile themselves, still more nitrogen, potassium and phosphorous. A feedback process may well occur. The fertility of the water encourages plant growth and plant growth contributes to the fertility of the water.

The foliage around the edge of a lake serves as a trap for wind-blown sediment, mostly silt and clay. Grains blow into the water and settle, as sediment, into the space between the plant roots. With time, an impressive accumulation of organic-rich sediment develops around the edge of the pond. As the sediment fills in the pond shrinks.

As time passes, advancing mats of plant debris will form a material called peat and it is peat, along with the sediment, that will eventually fill in the entire basin. In the end the pond is doomed. It will fill in with peat and a mixture of silt and clay. As things continue to change you have to keep finding the right words. The pond will evolve into swamp, the swamp will become a marsh, and the marsh will transform into a bog. These are often called “wetlands,” and people protect wetlands. But even protected wetlands are doomed. Wind will bring more silt and clay and fill in the space where water once was. The wetlands thus dry out and disappear altogether. That’s the nature of things geological; nothing lasts forever.

Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.” Read their blogs at “thecatskillgeologist.com,”

A snowstorm Dec 3, 2020

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A winter’s snow

Windows Through Time

Updated by Robert and Johanna Titus

 

As you might have already guessed, we spend a lot of time writing. We do these columns and many more for other newspapers and magazines. Sometimes, it would seem deserved, that we might get a little time off. Today is one of them. Today we are watching one of those occasional grand snowstorms developing. There is, coming from the far west, a lines of storms, called a “clipper.” That’s a typical event this time of the year. Most of our weather comes west to east across the continent. What makes today special is that there is a coastal storm front coming up from the south. This is air that got its start in the Gulf of Mexico. It was warm and humid when it began its journey towards us. Now it is cooling off rapidly. Air can hold a lot of humidity when it is warm, but not when it is cooling down. That humidity is turning into snow, right now and right in front of we.

There are thus two storms out there and, as we write, they are headed for a collision. In the parlance of our times, that is called a “perfect storm” after the title of a book that came out about years ago.  Perfect or imperfect, we are about to get clobbered. Scientists have studied such storms for generations; they seek to understand the physics of them, with the goal of being able to make sense of their seemingly erratic behavior.  Nature writers have written about them too; seeking to express their feelings as such storms pass. They are artists, seeking to paint with words the passage of a winter storm.

As it turns out, we possess both scientific and nature writer personalities, so we suppose we bear an extra burden if we choose to write about what it being called a “winter storm Nemo” We decided to take both the nature writer and the scientist out today and into the forest that makes up most of our property in Freehold. The four of us walked down the trail we have put together and took in the early hours of the storm.

The scientists got the better of it, we think, at least at first. They looked at the flakes coming down and marveled about how snowflakes are composed of a mineral called ice. Ice, indeed, is just as much a mineral as is quartz. But quartz never falls out of the sky; ice does. The scientists went on to note that ice is the only mineral that falls out of the sky. That threatened to take all the beauty and wonder out of what was happening all around us.

The nature writers motioned us to pause and listen. The woods all around us had become still, absolutely silent. All of the birds were hunkering down somewhere, hidden from view. There were, of course, no insects either. The snowfall was a quiet one, so no winds or even breezes could create any rustling sounds. But this was not an absolute silence that we experienced. In the far distance we could hear the flowing of Catskill Creek. The sounds of its rushing waters were normally muffled by a nearby din, but not on this type of day.

All four of us took note of the colors in the woods. There were only two of them. One was easy for me to describe; it was “snow white” and there was a lot of that all about us. But the other color was tough to put into words. Even the nature writers struggled. “It is an off gray” they said. “What on earth is an off gray“the other two of us laughed. “Well, okay, it is a gray with just a little of brown and a little less green in it” was the best the nature writers could do. The scientists struggled equally. “On a cloudy day only limited spectra of visible light reach the ground and only two colors are reflected back off a landscape. There is the white here and that peculiar gray.” It all sounded so erudite, but it smelled fishy, very fishy.

We continued our trek and soon encountered footprints in the snow. Deer were common, but there was something else that might have been a coyote. We debated that but had found something equally appealing to the four of us. It was fast getting dark and we hurried our pace heading back to home. We each had seen the snowstorm in a different way; it was a decidedly different experience for each of us. But all four of us had the good sense to appreciate it for what it was; a wondrous and beautiful natural event.

Reach all three authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.”

 

Journey to the Center of the Earth – 11-27-20

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Journey to the Center of the Earth, Pt 2

On the Rocks, the Woodstock Times

Nov 12, 1998

Updated by Robert and Johanna Titus

 

Last week we began a rather remarkable journey into the Earth’s interior. We traveled to the town of Catskill and visited a site that was once possibly miles beneath the surface. We saw beds of stratified rocks there that had been extensively folded by the intense pressures that occur at such depths. But, if a few miles may seem a lot to us, it’s not terribly deep by the standards of the planet. You would have to travel 4,000 miles to get to its center, a mere two or three is hardly anything. So, let’s try to do better this week.

From Woodstock travel across the Kingston-Rhinecliff Bridge. Head east to Rte. 9 and follow it north to Upper Red Hook. County Rte. 56 takes you east to County. Rte. 55 and that runs along the western shore of Spring Lake. We did some exploring at the north end of the lake and we found some fine outcroppings of a rock type we had not seen before in the Catskill-Hudson Valley region.

The roadside outcrops are excellent with very good exposures. As you approach these rocks you will observe that they really are unlike anything else in the area. If you have been visiting the sites we have described in our columns, you will have seen nothing like them. Virtually all of the bedrock in the region is stratified sedimentary rock; the beds are bedded sandstones, shales and limestones for the most part. They were once sediment, deposited in sheets that hardened into strata. But at Spring Lake the rocks are not bedded at all. Instead they are composed of shiny, crenulated masses of very dark rock.

The rock is called phyllite. It belongs to a broader category, commonly called metamorphic rock, and it has had a very long and hard history, even by the tough standards set by rocks. The phyllite here didn’t always look like this. A metamorphic rock, as the name implies, has been metamorphosed, changed in its appearance. It was formed originally as something quite different. It may well have been a sandstone or a shale in the very distant past, but it came to be altered. It was buried under very thick sequences of other sedimentary rock, many thousands of feet or even miles of other rock. Then it was caught up in a great mountain building event.

  Phyllite

Metamorphism occurs under such circumstances. The rocks are first subjected to the great pressures that are associated with deep burial. Then too, having sunk to great depths within the Earth’s crust, the rocks enter very hot realms and become, quite literally, baked. Combine the effects of high temperature with high pressure and you get metamorphism. The rocks become contorted and crenulated with the pressure. They become shiny as mica minerals begin to grow within them. That new rock is phyllite.

Surprisingly, phyllite is what is called a very low-grade metamorphic rock. That means things could have been much worse. In the deep interior of this enormous planet, even higher temperatures and pressures are encountered and higher grades of metamorphism are found.

If you look at these outcroppings, you will find a number of seams of course, white crystalline minerals. This is quartz and it probably formed here late in the metamorphic history of the rock. The quartz is interesting but not central to our story.

When did all this happen? The answer is probably during the Devonian time period, during what is called the Acadian Mountain building event. That was one of the three big uplifts that led to the creation of what we call the Appalachian Mountain chain. In effect, then, as we travel to Spring Lake, we enter into the deepest interior of the old Appalachians. No, we have not traveled to the center of the Earth, but we have made quite a very good try at it.

Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.”

Tafoni at Pratt’s Rock – Nov 19, 2020

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A real geological mystery, and at Pratt’s Rock

The Catskill Geologists

Robert and Johanna Titus

 

We were invited to speak at the Pratt Museum recently. Our topic was the glacial geology of the Schoharie Creek Valley. After that, a group of us went to Pratt Rock and climbed up the trail there. We took a look at Colonel Pratt’s carvings and continued on to see some nice ice age features. But, along the way, we ran across one of those mysteries we have long struggled with.

We were first alerted to this particular mystery by Paul Misko, a veteran Catskills hiker. Paul told us of some “very strange structures he had found in Phoenicia. Paul has a real eye for unusual geology, so we paid attention to his “very strange” claim. We saw his Phoenician structures and now we have found more of them at Pratt’s Rock. Take a look at our photo and then climb up the steep incline at Pratts Rock and keep an eye out. Towards the top you will find sizable ledges of sandstone. This is rather commonplace stuff: very typical Catskills bluestone ledges. These ledges are, in essence, the cross sections of a very old streams. It’s, like all rocks in the Catskills, Devonian in age, something a bit less than 400 million years old.

None of this surprised us in the least but that’s where we encountered that mystery. Take another look at our photo and see what you think. See the cluster of closely spaced and very strange cavities just above the hand. Their shapes vary considerably, but they all show a sort of boxy nature and they seem to form an interlocking network. We would like to use the term honeycomb here, but honeycombs show a consistent hexagonal shape; we don’t see that with these. The rock remaining in between these cavities is narrow. The cavities do not penetrate too far into the rock, just a few inches. And there is no reason to think that there is another horizon of these cavities under the ones that are visible. Thus, they appear to be surficial features. Many of these cavities are spaced so close together that they comprise a bigger compound cavity. Whatever it was that formed them was focused.

All in all, this is one of the most puzzling phenomena that we have seen in the Catskills. There is no trouble putting a name on what is here; these structures are called “tafoni.” Each individual cavity is a tafone; lots of them are tafoni. And the terminology keeps getting better; when tafoni occur on cliff faces, as here, then it is called lateral or sidewall tafoni. But, putting a name on something is not the same as understanding it.

What are these features? They seem to be chemical weathering phenomena. Somehow, they appeared on the rock surface and grew slowly into their observed shapes, but exactly how? And, also, how is it that they grow in size until they abut each other but do not grow into each other? How do they grow in size without intersecting? Those are very puzzling questions and just naming these things does not provide answers.

Tafoni have been weakly associated with poorly defined stratification on the sides of cliffs and that is the case here: sort of. But that still leaves a lot unsaid. Why does this “association” occur? What are the specifics? Salt is commonly cited as an agent in tafoni development. They are sometimes found on coastal outcroppings, splashed by ocean waves. But there is certainly no source of salt here on a sandstone cliff in Prattsville, and certainly no waves. And, why do only a few Catskill Cliffs display these? That begs the question: what exactly is different about his cliff? Why don’t all cliffs have tafoni? Why isn’t it that none of them do? There must be something here, right in front of our eyes, which we have missed. This is the sort of thing that makes science so much fun.

   Do you have any ideas or questions? Have you seen tafoni somewhere? Contact the authors at randjtitus@prodigy.net. Join their Facebook page “The Catskill Geologist.” Read their blogs at “thecatskillgeologist.com.”

The Austin Glen Formation 11-12-20

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The Austin Glen Formation.

On the Rocks – The Woodstock Times 1998

Updated by Robert and Johanna Titus

 

The east side of the Hudson River has some very different rocks from those we see around Woodstock. They’re older too and so, of course, they must have different stories to tell. Cross over the Kingston-Rhinecliff Bridge and you won’t have to go far before you see some of these strata. On the north side of the highway (Rt. 199) We found a nice road cut. It was a sequence of dark, thin-bedded shales interbedded with many thick strata of brown and gray sandstone. You are likely to have passed this outcrop many times without taking note of it and we don’t blame you. The unit of rock here is called the Austin Glen Formation and it is certainly not much to look at, gray sandstone alternating with dark shale is hardly picturesque. But to appreciate a unit of rock you have to really understand it and, dull as it looks, the Austin Glen is a most remarkable sequence of strata.

Austin Glen to the right.

There are problems with the unit which, when solved, lead to a fine story. Let’s see. The black shales of the Austin Glen pose little trouble in understanding, or so it would seem. Black shales were once black mud. Such mud accumulated on the quiet floor of a deep ocean and I mean really deep, maybe tens of thousands of feet, a real abyss. So that’s that; the Austin Glen must have formed in the depths of one of the earth’s deepest oceans, or so the shales say. But the sandstones tell a different tale. The sandstones were deposited by fast-flowing currents. we looked and found laminations that are typical of such conditions. And there were also ripple marks preserved in the sands, these are the sculptures of powerful currents. Such currents are most often found in shallow waters. So, the Austin Glen must have formed in a shallow sea, or so the sands say.

So, which is it? Are the shales correct in their tale of deep, quiet waters or are the sandstones closer to the mark? Who’s telling the truth and who is trying to fool us? This is the sort of problem geologists frequently face. Fortunately, this problem had already been solved. Our interpretation of the shales was probably okay, but we must confess that we did get the sands all wrong, at least at first telling.

The sandstone beds of the Austin Glen weren’t deposited by shallow water currents; they were gravity deposits, essentially submarine avalanches. The Austin Glen did indeed, as the shales said, accumulate in very deep, quiet seas. At least they were usually quiet and most of the time the soft muds settled to the bottom of this oceanic basin. But this sea floor was at the bottom of a steep and very deep marine slope. From time to time earthquakes occurred and these triggered the sudden downslope displacement of large amounts of sand, submarine avalanches. We call these “turbidity currents,” and their sandy deposits are called turbidites. Their rapid downward rush slowed near the bottom of the slope and then deposited the laminated and

sometimes rippled sands that we see today.

After each avalanche the sea returned to the slow piling up of more mud. Hence thicknesses of black shale were commonly punctuated by layers of sandstone. In the end the typical Austin Glen strata formed. All this took a very long time and a total of more than 500 feet of Austin Glen strata piled up.

That outcrop, east of the Rhinecliff Bridge, is thus a history, written in rock, of the hit and miss crustal activities of long ago. As we walked along the outcrop we sometimes saw thick sequences of shales; those were the long quiet periods between earthquakes and turbidity currents, when only muds accumulated. There were also a number of thin sandstones, they were turbidites of lessor magnitudes. But then there were also sequences of very thick turbidites laid down in quick succession. We thought about those times; they must have been difficult chapters in our local history, times when powerful earthquakes may have rocked the area, sending great turbidity currents plummeting into the abyss. These were remarkable times, but they would have been forgotten except that they were preserved in the roadside rocks.

Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.

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