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A Gelogical Tourist Trap Dec. 5, 2019

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Flocks of geologists
Windows Through Time, The Register Star
June 4, 2009
Updated by Robert and Johanna Titus

Dear Robert and Johanna – I have been enjoying your columns in the Hudson-Catskill newspapers. I have a question. I wonder what so many college groups have been studying at the Leeds exit along Rte. 23? – WJM – Athens

WJM: Thanks for the good question. Over the years we have heard this one from a lot of people. Anybody who frequently drives this stretch of the road in the autumn or the spring will have seen sometimes large groups of college students climbing over the rocks at this site. You will be interested to know that this is one of the great “geological tourist traps” of the American northeast. Any eastern geologist who is anybody in geology has been to this location. I wonder if we even know any geologist who has not been here. So, what is the big draw?
The answer is that this outcropping displays something called an “angular unconformity,” and this one is a very historic structure. Read on and learn about this peculiar feature. If you are going by it sometime soon, you might want to stop and see for yourself that which captivates so many young geologists. If you do, you will see some interesting geology.

The right (east) side of the outcrop displays what are called stratified sedimentary rocks. These are thick horizons of alternating gray sandstone and black shale. Each layer of rock was once deposited as sediment at the bottom of the sea. Back then, these were horizons of sand and mud. That’s a most surprising observation. Look around. Do you see and saltwater here? This does not look like the bottom of an ocean, but it once was. That’s incredible but true.
We see these rocks; we look into their distant past and see the ocean that was once here. It has been a very long time since the earliest geologists figured this out. So long that we have forgotten who first made this amazing deduction. The first person to write these thoughts down was Scottish geologist James Hutton in the 1790’s. This was not only one of the most important discoveries in the history of geology but of science itself. Look around and think about it. You are standing at what really was the bottom of a sea. These strata of sand and mud formed on that long-ago seafloor. Turn a full 360 degrees; hold up your hands and feel the saltwater that was once here. Times have changed!
But there is something else here and it is also important. Notice that the sandstone and shale strata are tilted, they are nearly vertical. When sediments are deposited on the floor of an ocean they are laid down in horizontal sheets. These strata should have stayed that way, but that is not the case here. Again, they are nearly vertical. They must have come to be tilted and that’s where the story gets even more interesting. Think about how heavy these rocks are and how much energy it would take to tilt them. The only processes that can lift and tilt such rocks are those of mountain building events.
These rocks are from something called the Ordovician time period; they are about 450 million years old. That’s when North American was enduring a great collision with an eastern landmass much the size of today’s Japan. You would call it Europe or – better – “proto-Europe.” Collisions, of this sort, initiate chapters of downwarping. The crust folds downward and the seas flood the region. Those seas accumulated the sand and mud that hardened into today’s rocks. Then continued collision came to reverse the whole process and caused a massive mountain building uplift. All this is how those rocks formed, and how they were tilted and raised to above sea level. But, of course, there is still more.
The rocks on the left (west) side of the outcrop are limestones. They formed during a time that is called the Devonian Period and they are only about 420 million years old. They formed in a shallow tropical sea and the rocks are sometimes rich in marine fossils. If you stop here, perhaps you can find a few. This was the bottom of a second ocean!
These too are stratified, but these strata dip to the left. Once again, North America was enduring a collision with another Japan-sized land mass. It was “déjà vu all over again!” Once again, the crust was folded downwards and that is when the limestone formed – in a shallow tropical sea. That downwarping would eventually be followed by another uplift. That’s when the second tilting occurred.
The boundary between these two units of rock is what we call an angular unconformity. The word angular refers to the angle between the strata of the two rock units. The word unconformity refers to the period of period of erosion that followed the first mountain building event and preceded the second.
And that is the centerpiece of what we, and all those college students, are looking at. This is a petrified record of two mountain building events. There is a lot of history here and young geologists come from all over to see it. You can too.

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

Name Your Poisen Nov. 28, 2019

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Name Your Poison
On the Rocks; The Woodstock Times
Updated by Robert and Johanna Titus
June 18, 1998

Black sedimentary rocks are occasionally seen in the Hudson Valley. Recently [1998], we described some along Rt. 209, south of Sawkill. The dark appearance of these strata makes them remarkably eye-catching and, when they make up tall cliffs, they loom, dark and menacing, over the landscapes.
It’s the shiny, jet-black shales that we are talking about. They are often rich in undecayed organic matter; it’s the carbon that makes these rocks black. This generally suggests to the geologist that there were low-oxygen conditions in the sea waters at the time of deposition. Without oxygen, most decay bacteria cannot function; they die before they can completely destroy the organic matter. But why low oxygen? That takes us back in time.

Back in the early Devonian Period, these shales were accumulating in a deep sea, immediately adjacent to the rising Acadian Mountains of western New England. Thick soils formed on the rapidly weathering mountainsides. The soils were easily and rapidly eroded and provided sediments that were eventually transported into the nearby Catskill Sea. This material was rich in dissolved nutrients, such as nitrates and phosphates. They fertilized the water and that led to the next step in what was to be a complex chain of events.
The fertilized waters were ideal for algae; they experienced algal blooms, great population explosions in the surface waters of the Catskill Sea. A whole ecology became established as dense mats of floating, or planktonic, plants and animals grew, somewhat similar to that of today’s Sargasso Sea. While all this was great for the plankton it was deadly for just about every other category of marine organisms. As the plankton died, they were attacked by decay bacteria; the algae bloom led to a bacteria bloom. But the decay process consumed so much oxygen that the seas soon became oxygen depleted. The hapless bacteria had, in effect, poisoned their own habitat, because they needed oxygen too. Their numbers quickly plummeted and very soon, all types of animals suffered as well, suffocated in the oxygen depleted sea. But the algae just kept on proliferating in the surface waters where there was plenty of oxygen, diffusing in from the air above. Soon, large masses of undecayed biological material were sinking to the floor of the ocean. The climate was tropical, and the nearby coastal lowlands provided lots of vegetation, much of which drifted into the basin, adding more organic matter to the black shales. Almost all of these organics accumulated as thinly laminated, shiny black shales.
Back then, the Catskill Sea was largely isolated from other deep bodies of water; it was nearly surrounded by land or very shallow water. To its east, land blocked weather patterns and shielded the basin from most storm activity. All of these conditions promoted what are called stagnant, thermally stratified waters. The sunbaked surface layer was hot, while deeper water remained cool. Depth stratification and a dense planktonic mat combined to prevent agitation and mixing of the waters, causing stagnant sea floor conditions to develop. Virtually nothing could live in this sea, except at the surface where there was always plenty of oxygen. This was truly the poison sea.
Many of the earliest Catskill shales are jet black, and they form the Bakoven Shale at the base of what is called the lower Marcellus Group. As we have seen, they are the record of the Catskill poison seas. The upper beds of the Marcellus Group are similar looking but very different deposits. These are fossiliferous black shales and dark gray sandstones. They sometimes have rich assemblages of brachiopods, clams and even corals. These were still mud-bottomed seas, but they were deposited at times when there was a fairly large amount of oxygen in the water, at least enough to allow marine shellfish to survive and even flourish. These can be fun rocks to poke through as they are occasionally richly fossiliferous, and the preservation of those fossils can be very good.
See the Bakoven Shale on Rte. 23A where it crosses Kaaterskill Creek east of Kiskatom. Go visit that large outcrop along Rte. 209, between Kingston and Sawkill. The far south end is the real poison sea; as you travel upwards and north from those beds you are looking at shallower waters which had more oxygen.

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

Gaps in our knowledge Nov. 21, 2019

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Gaps in our Knowledge
On the Rocks/ The Woodstock Times
Jan. 22, 1998
Updated by Robert and Johanna Titus

Take Rte. 28 west from Woodstock, turn right at Dancing Rock Road (it’s two miles east of Boiceville) and go up one mile to the end of the paved road. Look south and, there below, is the Ashokan Reservoir. Above it, on the horizon, is High Point Mountain. The mountain profile is nothing particularly unusual except for one feature. There is a notch cut into the top of the mountain. It is the sort of landscape feature that you pay little heed to; it doesn’t seem all that strange until you look at it carefully and ask a simple question. How did it get there?
The notch has a name: it’s Wagon Wheel Gap. we suspect that the name came from the deep ruts that old fashioned wagon wheels carved into roads before the auto age. The gap is at least 200 feet deep and steep on both sides. It seems to be something cut into the mountain. It was. Not surprisingly this odd landscape feature does have a story to tell and it is a surprising one.
Wagon Wheel Gap is a glacial feature, but different from most. Glaciers are very good at eroding landscapes and they can carve notches into the landscape. But that kind of glacial erosion produces a nice, smooth, U-shaped gap. West Kill Valley is a good example. It’s relatively wide and rounded at the bottom. Stony Clove is narrow like Wagon Wheel Notch but it has been cut right down to the level of the valley. Wagon Wheel Gap is altogether different. There’s nothing broad and round about it. It’s a sharp slash, like something cut by a knife. The bottom of the gap lays well above the level of the nearest valley, in fact 700 feet above. Wagon Wheel Gap seems something quickly and violently cut into the High Point mountain.

The story of Wagon Wheel Gap takes us back about 17,000 years. At that time a large glacier was pushing up the Esopus Creek valley. It passed the present site of the Ashokan Reservoir and pushed on; we are not sure how much farther. This ice did reach a still-stand and then, with warming climate, it began a slow retreat. The warming halted briefly, and the glacier reached another still-stand, just exactly abutting against the present-day gap.
The ice acted as a dam and so it blocked the whole upper Esopus Creek which then filled with a reservoir of cold water. The water had to drain off somewhere and it made its way across the slopes of High Point and drained off to the south. In what had to be a very short period of time, that flow of water cut into the mountain and carved the gap we see today. It’s quite something to imagine. There would have been an enormous amount of water pouring through the gap back then. There would have been all of the normal flow of the Esopus Creek plus all the water provided by the region’s melting glaciers. That’s a lot.
The flow must have positively raged through the Wagon Wheel, perhaps the mother of all whitewater flows. And loud too, a thunderous, pounding cacophony. It must have torn into the mountain with an effect something akin to a buzz saw. At any rate, the flow must have continued while the Esopus glacier retreated down the valley. Eventually the flow of water must have found other ways out of the valley and Wagon Wheel Gap would have been very abruptly abandoned. The whitewater flow would have dried up overnight.
And there it lies today, an abandoned notch, lying there silently in the mountain. It’s a landscape oddity with a colorful past. But how many people know even to notice such a thing. It’s, to most, just a notch in the mountain, nothing of note. What a marvel it is that glacial geologists can come along and understand these things.

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

Voyage to the bottom of the sea – Nov. 14, 2019

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Journey to the bottom of the Sea
On the Rocks; the Woodstock Times
April 30, 1998
Updated by Robert and Johanna Titus

We geologists, over and over, are used to seeing vivid moments from the past, recorded in the rocks. We never become blasé’ about this, and we shouldn’t; we are privileged to have these visions. We were reminded of this recently when we encountered an especially fine outcrop along Rte. 9W, at Glenerie Falls about a mile and a half south from its intersection with the Glasco Turnpike. It’s the Glasco Limestone which is commonly seen along the highway hereabouts. There was one very broad surface which caught our attention. It’s a bed of rock so steep that we found it difficult to climb, but that mattered little as the bed slanted down to the level of the road. The strata, dipping to the west, are typical of this vicinity. These rocks got caught up and tilted in the deformation associated with ancient mountain building in New England.

What makes this such a fine exposure is that there is one particular stratum which is expansively exposed. That’s unusual. We geologists spend a lot of time looking at strata in cross section, but we rarely get to see a broad surface like this. Once again, we had become time-travelers; this bit of geology had taken us back in time to the Late Silurian time period. We don’t mean that figuratively, but quite literally; this stratum of sedimentary rock was deposited on the floor of a sunlit shallow sea perhaps 425 million years ago. For a time, it actually was the sea floor and, upon it, grew the seaweeds and crawled the shellfish of the old Silurian age sea.
But time is fleeting, even geological time. Sooner or later (and in geology it really can be later) a sea floor is condemned to be buried. Storms blow up and the winds generate currents which bring new masses of sediment to be spread about. Many of the plants and animals that populated the old sea floor remain, but only as fossils. Layer after layer of sediment piles up and the sea floors of old harden into strata of rock lost in time. That’s what geologists see in cross section when they study layered road outcrops such as most of those on Rte. 9W.
But not all of the strata here have shared that inglorious fate. There is, for example, this one fine stratum. It’s an example of something unusual, an exhumed sea floor. Nature (helped a lot by the highway department) has stripped the overburden off of this old sea floor and exposed it for us to see.
You have, quite likely, been on a boat that cruised above the floor of a shallow sea. It’s a lot of fun; you can look down and observe the marine life going by below. Glass-bottom boats are specifically designed for this. In Florida or the Bahamas, you can’t beat it for a fascinating afternoon. It’s nice that we can do the same thing right here in Ulster County.
Our stratum, along Rte. 9W, can’t quite compete with a glass-bottom boat in the Bahamas. All of the old seaweeds are gone, so too are most of the animals. All those creatures without skeletons or with only delicate skeletons are lost to time. Only those shellfish that had sturdy shells remain, but there are plenty of them. We found quite a few brachiopods, those bivalve shellfish that remind us of clams. They occurred in clusters of specimens, all about the same size. We think that these were what biologists call “spatfalls,” clusters of larval brachiopods that settled here and grew up together. These are “families” of shellfish, if you can imagine such a thing. We found a few clams here as well, but they weren’t common. Finally, we found the weathered and forlorn tail of a trilobite, all that remained of a once fine-looking animal. All in all, what we were looking at was a snapshot of the old Silurian sea floor, just a moment in time, nothing special and maybe that’s why it is special.
Because of its steepness, this old sea floor is difficult to climb around on. If you visit the site, be very careful. One slip and down you go. The fact is, however, that there is no real need to climb up the exposure at all, most all the good things you can see are found at the base of the outcrop. There’s no real need to climb any higher. So do go and see this little natural wonder. You don’t get many opportunities to explore a sea floor, especially one that existed 400 million years ago.
Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.”

Floods on Overlook Mountain 11- 6 – 19

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On the Rocks
The Woodstock Times, Oct. 1996
Updated by Robert and Johanna Titus

It’s autumn and it’s a time when we in the Catskills are given some of the best weather there is to enjoy the outdoors. There are few places better suited to the mood of the season than the Overlook Mountain trail. The word trail is a bit of misnomer. This was once a highway of some significance, but those days are over; it’s just a hiking path now.
The trail takes you past Echo Lake and onward toward Plattekill Clove. There are the subtle signs of a history along the way. You can see where quarry stone was used to reinforce the road for heavy traffic. It was needed; the Overlook Road once carried wagon loads of heavy Catskill bluestone. There were a lot of active quarries up there once, especially at the north end of the one-time highway. Look for a fork in the trail there, where the Blue, Red and Green Trails intersect. Within a few hundred yards of that spot are quite a few of the old quarries.
Some quarries are overgrown, but most are very much as they were on the day that operations halted. Quarrymen sought after flat-lying stratified sandstone, sometimes called flagstone, but mostly called bluestone. The rock easily split along its strata into stone useful for sidewalks and as various types of building stone. If the rock wasn’t made of flat-lying strata they left it be; it was of no monetary value and therefore of no interest. But it’s that odd stone that is of the greatest interest to a geologist; the non-flat lying strata tell the best stories.
Much of the rock which ended up left behind is what we call cross-bedded sandstone. These are very nicely defined strata which occur in sets that are never horizontal but intersect each other at all sorts of angles. The pattern is eye-catching; the rock seems to possess a written record of its own history, a hieroglyphic if you could only read it. It does and you can.

Most bluestone was once sand that was deposited in ancient stream channels. That was about 380 million years ago during the Devonian time period. Cross-bedded sands of this sort form in the deepest, most rapid flowing part of stream channels, a churning, swirling time in the history of those ancient rivers. Rapid and strong currents scoured out troughs on the stream bed. Later, when the currents slowed down, sand was deposited, and it filled in the original troughs. Over and over the process was repeated and eventually the cross-bedded sands formed. Streams of this sort tend to shift their channels as they meander across the flood plain, and the sands were left behind under a thickening accumulation of flood plain deposits. When thick enough the pressure began to harden the sediment into the sandstone we see today.

These deposits accumulated at times of maximum flow and these are likely to have been floods. Floods to humans are awful events, powerful and destructive episodes when stream banks collapse and plants and animals are killed. Nowadays when floods happen, newspaper headlines scream of the damage. Remember last January [1995] in the central Catskills.
But these were events which occurred long before people. All the terrible events that we associate with modern floods occurred here; surely many primitive animals died, and perhaps whole forests were washed away. But no one was there to mourn the losses, nobody cleaned up or repaired the damage. No newspapers or history books recorded these awful events and life just went on. Only the rocks carry the “hieroglyphs” of these terrible moments in the deep-time history of our region and only geologists can read them.
If you get a chance, pick one of those beautiful, clear, dry, warm fall days and go hike the Overlook trail. Find some of these cross-bedded strata. These were awful moments that Nature prefers to forget. There is violence and power here, there is noise and turmoil, there is the struggle for, and giving up of life. Take a good look at these strata and appreciate the history they record. Such things can give you a whole different point of view on rocks.

Contact the authors at randjtitus@prodigy.net. Join their facebook page “thecatskillgeologist.com.”

Some fine boulders in Cooperstown 10-31-19

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On the waterfront
The Cooperstown Geologist
Feb. 2007
Updated by Robert and Johanna Titus

When you are a geologist you have to get used to the idea that you are always (pardon this!) a stone’s throw away from a journey into the distant past. We had such an experience recently at Lakefront Park in Cooperstown. There, at the end of the Pioneer Street, are eight sizable boulders. We imagine they are there to keep people from driving into the lake. But they helped us to “drive” into the early Devonian time period. That’s a journey back in time of about 400 million years.

These boulders aren’t from the area; they were quarried somewhere else, but we recognized them immediately. They are from something that geologists call the Helderberg Limestone. They may well be from the Helderberg Mountains near Albany.
Limestones are special rocks for geologists. They carry us off to tropical places, and we mean that quite literally. The material of limestone is called calcium carbonate, stuff that mostly forms in shallow tropical seas. Have you walked the pink sandy beaches of Florida or the Bahamas? Then you have walked on carbonates. Petrify one of those beaches and, presto: sediment becomes rock, and the rock is limestone.
These boulders, however, did not form on some ancient beach. If you get a chance, take a good look at them. They are stratified, that is to say that the rock is layered. Each horizon represents a Devonian sea floor. We found some sandy sea floors and some muddy ones too. This was a mixed marine ecology.
There were plenty of creatures living on these sea bottoms. The boulders are all fossiliferous; look them over, and it won’t take very long for you to find some of these fossils. A visit here is a very colorful journey to the bottom of the sea.
It was the corals that most caught our eyes. Yes, we said corals, and right here in upstate New York! Take a look at the fifth boulder from the right (east) side, especially on the right side of the rock, about two feet from it’s top. Our field notes tell us that there are two types of corals to be seen here. The first is called the honeycomb coral (C on second illustration) and that’s a good choice in terms. It looks like petrified bee’s wax. The second is the horn coral (A on second illustration). It’s called that because it looks like a cow’s horn, wide and round at the top and tapering to a point. You will see something that looks like the cross section of a cut orange. Horn corals have compartments that remind me of the segments of an orange.

There are enough corals here so that we have to wonder if these rocks did not come from a reef ecology. That could be, as the Devonian was a time of many large reefs and there are many Helderberg coral reefs known in New York State.
The story gets better when you learn more about Helderberg stratigraphy. As we said earlier, these limestones are exposed in the Helderberg Mountains. But the limestone strata are known to plunge underground as you head west towards Cooperstown. That means that some of the Helderberg lies buried deep beneath Cooperstown. Hundreds of feet beneath Lakefront Park is a great thickness of Helderberg Limestone and a good bit of it is probably fossil reef.
That means (and this is astonishing) that Cooperstown was certainly once the site of a beautiful shallow Bahamas-like tropical sea. Look around you and imagine the pink sands and green seaweeds that were once right here. Look up and see aqua colored waters above you. Imagine the primitive fish that once swam here.
And it only gets better, the more you think about it. Cooperstown is also very likely to have been the site of a Devonian coral reef. This is a pretty area, especially in the autumn, but have you ever, in your wildest imagination, envisioned coral reefs and all their beauty . . . right here?
Geology changes your perspective on things, doesn’t it?

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

Erratic behavior – Alligator Rock 10-24-9

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Erratic Behavior
On the Rocks
The Woodstock Times, 1997
Updated by Robert and Johanna Titus

North Lake Campground has always been a wonderful place to visit at any time of the year, but autumn is a special time. We never need too many excuses to make the trip. We almost always start out at the parking lot at North Lake itself, then we take the trail south along the shore of the lake. The trail will take you out to the point of rock that separates North and South Lakes. Travel around the point and in another quarter mile or so you will encounter a most remarkable boulder. It is enormous, it must be twenty-five feet or more across and perhaps eight feet high. That’s a lot of rock, but that’s not all.

A rock that big deserves a name and this one is called “Alligator rock.” We are not convinced that was a good choice, how about dinosaur rock? Nope, that name has already been taken for an equally large boulder about 50 yards away. But we don’t get to change names anyway: Alligator rock it is.

A person is entitled to ask where a boulder this large came from. It’s a good question and there is an answer. Boulder rock is what geologists called a glacial erratic. About 15,000 years ago all of North Lake was buried under a large glacier, a sheet of ice that was flowing southward down the Hudson Valley.
Moving ice is good at two special things. First it is very good at ripping up large blocks of rock and second it is even better at carrying those blocks of rock away. You have to use your imagination to get a fix on all this. Travel back to the Catskill Mountain House ledge and gaze at the horizon to the north. You have to be able to see ice coming down the valley and slowly filling the Hudson. Then it rises up the highest slopes of the valley wall right beneath us. Soon ice is coming over the ledge just to the north. The ledge is soon overwhelmed by the moving ice. As the glacier shears across those barriers of rock it adheres to the rock and plucks loose many large boulders.
Nobody can actually see such a thing. You really do need a good imagination to imagine all this. In real ice age life such events go on in the darkness at the bottom of a glacier. But we understand that the bottom of every moving glacier is replete with many such boulders. Some of them are a lot bigger than Boulder rock. Some are truly the size of houses. Neither Alligator nor Dinosaur Rocks are that large, but they are big enough.

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

Boulders at Mink Hollow 10-17-19

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Boulders of Mink Hollow
On the Rocks\
The Woodstock Times
Updated by Robert and Johanna Titus

If you live in Woodstock, then one of the most accessible of the Catskill hiking trails is the one at Mink Hollow. Head west on Rte. 212 and then, just past Cooper Lake, turn north on Mink Hollow Road. At the end of the road you will find parking and the trail head. Soon you can begin your hike on the Blue Trail. The hike will take you up what was once actually a highway of some importance. Vehicles, loaded with people and goods from as far away as Prattsville, traveled on it with destinations in Woodstock and beyond. There are still paved Mink Hollow Roads both north and south, but here in between, the trail stopped being a public road long ago. Today the path takes you up to Mink Hollow itself. That’s a deep, narrow gap in the mountains, mostly cut during the Ice Age. Beyond Mink Hollow the trail veers off to the northeast and takes you along Roaring Kill to another trail head on Elka Park Road. It’s an easy walk through the woods, and that’s especially nice in the summer. It stops being easy if you want to climb Sugarloaf or Plateau Mountains. Those are tough climbs, but well worth the effort. They are, however, another story for another day.
There is one very nice geological feature to see here, however, and that is our subject for today. In Mink Hollow itself there is a lean-to, built to give hikers a place to spend the night. Just south of this lean-to there is a wonderful example of what glacial geologists call pedestal rocks. You can’t miss them. They are immediately east of the trail, just about 100 yards short of the lean-to. They make a most striking feature. There are three good-sized boulders. Two of them are next to each at the bottom of the heap, while the third is a cross bar, lying atop the others and bridging the two.

Just how on earth could such natural Stonehenge happen? First of all, nobody stacked them here; there were never any Druids in the Catskills and the boulders are far too large and isolated for any other people to have bothered with them. There are some who think that such things were human in origin. But we think there is a natural explanation. Nature did this, and geologists long ago figured out how. Our story takes us back to the end of the Ice Age. At that time, probably about 16,000 years ago, there was a large glacier, filling all of the Schoharie Creek Valley to the north. A large tongue of that glacier poked through Mink Hollow and pushed on a short distance to the south.
This was a dynamic tongue of ice and it was actively advancing through Mink Hollow. If the leaves are not too thick, you can look upward from the lean-to and see a number of rough ledges on the western slope of Sugarloaf Mountain. These formed when large masses of rock were plucked from the mountain by the moving ice. And that gets us to the heart of our story.
That huge tongue of ice passing through Mink Hollow had a great number of boulders in it. These were routinely being broken loose from the ledges above and carried through the hollow. Most were dragged off to the south by the currents of moving ice and deposited at the south end of the glacier.
But eventually the climate warmed and the glaciers began melting. At that time blocks of rock would have been lowered through the melting ice until they made a soft “landing.” As luck would have it, some boulders would land next to each other, while on much rarer occasions, a boulder would end up lowered onto one or two others, forming a pedestal. That’s what happened along the Mink Hollow Trail.
Pause here for a moment and imagine Mink Hollow filled with ice. Look around and you will see all the boulders that are here. Each one was once the baggage of a glacier. It’s a nice story and just one of those many interesting phenomena that remind us of the influence glaciers have had on our landscape. And it is nice not only to appreciate the beauty of a landscape, but to understand it as well.

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

The Old Mountain Turnpike 10-10-19

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The Old Mountain Turnpike
The Greenville Press
Sep. 4, 2007
Updated by Robert and Johanna Titus

One of our region’s most historic roads is also one of its least known. It’s the Old Mountain Turnpike. Long ago, the road was the gateway to the Catskills. As far back as the 1820’s guests of the famed Catskill Mountain House Hotel rode carriages up the road to get to the hotel. As the Mountain House prospered, so did the road. When the hotel got too successful it built the Otis Elevated Railway right up the Catskill Front and the turnpike fell into disuse. Today the old road is just a horse and hiking trail, but it still has much of its 19th Century atmosphere. It makes a nice walk in the woods and, of course, along the way there are many rocks.
To get to the old turnpike take Rte. 32 south to the turn at Game Farm Road. Soon you must turn left onto Boggart Road and head south to a right on Mountain Turnpike Road. The trail head is at the end of the road. You can hike all the way up to North Lake State Park if you like, or any part of the trip.
You don’t have to go far before you are in the thick of the geology. The road makes a bend to the right and alongside is an outcropping of red rock. The rocks are floodplain deposits of the Devonian age Catskill Delta. Red strata are old flood deposits, silts and clays deposited by very long-ago floods and hardened into red shale. The darker deposits are the old muds of back swamps. Away from the river channels swamps formed in low-lying areas and dark muds accumulated. Watch for fossil plant fragments in all of this.
As you continue up the road you will encounter, at frequent intervals, a number of sandstone ledges. These are first seen in the slopes above the road, and, as the road rises, the ledges descend to its level. The sandstones are old river channel deposits. They are composed mostly of sandy strata that dip one way or another. These are called cross beds and they are the product of river currents. The currents drove masses of sand into large “dunes” which migrated downstream. Most of those cross beds dip to the northwest as that was the direction that the rivers flowed. In between the sandstone ledges the road tends to be pink or red. These are hidden floodplain deposits. The pattern is clear: River sands are followed by red floodplain shales and then more river sands and so on. The Catskill Front is made up of sandstone and shale “stories” of stone, like a great, tall building. When we make such a hike, we almost always count the stories.
The second story had some prominent ripple marks in a layer of red shale that crossed the road. This recorded Devonian breezes that blew across a shallow floodplain pond and generated currents that, in turn, created the ripples. Those ripples were a recording of a breeze of about 375 million years ago. It is incredible to think of.

At the fourth story we found a vertical ledge of sandstone that had been scoured and striated by a passing glacier. This event had occurred a mere 14,000 years ago, a twinkling of time compared to the age of the rocks themselves.
The 14th story was particularly massive sandstone. This must have been a very large river. These rivers were what are called distributaries. In a large delta complex the trunk stream breaks up into many such distributaries. Each one flows into the ocean. Look at a map of the Mississippi Delta and you will see good examples of distributaries. Better still, look at a map of the Ganges River Delta of Bangladesh and you will see a better example.

The road ascended into a hollow and made a sharp bend. Here had once stood the Rip Van Winkle House; it had been the halfway stop for carriages headed up to the hotel. The hollow was naturally air conditioned with cool heavy mountain breezes descending through it. It must have been a nice place to stop.

Just ahead was one of the largest, thickest stories of the hike. We thought that this must have been one of the greatest rivers of the Catskill Delta. These distributaries meander back and forth across a delta plain. A river that is here today, may be gone tomorrow, replaced by a floodplain. That’s why these rivers sandstones alternate with red floodplain shales. The geology here is actually very easy; the sandstones are river deposits and all the rest is floodplain. Everything is Devonian and none of it is less the 350 million years old.
The 24th story brought us to a great overlook. The trees have been cleared away here and a picnic table set up. We interrupted our journey and sat and gazed out at the Hudson Valley. We had seen a lot of geological history already. We had watched as 24 times rivers had crossed this location back in the days of the Catskill Delta. Much of this had been sandstone and sandstone is made of sand. But where had all that sand come from? The only place such large amounts of sand can come from is the erosion of a great mountain range. From our picnic table seat, we gazed across the Hudson Valley and saw the profile of a great mountain range rising above the Berkshires. These were the Devonian age Acadian Mountains. They may once have rivaled the Himalayas, but now they have been eroded away. All that is left are those picturesque hills of western New England. Now we really had seen a lot of history, but there was so much more.

The old trail and we continued up the mountain in a zigzagging pattern. Sometimes the way was very steep, and we thought of how the horses must have struggled here in the 19th century. The sandstones came to be much thicker and prominent. Very large ledges lay left and right of the old path. The road cut right through some of them in several locations. Now we understood what they represented. These sandstones were a record of the destruction of the Acadians. As the old mountains came to be weathered and eroded, they shed their sands into New York State and made the sediments that would eventually become the Catskills. And the Old Mountain Turnpike was a history of all this.
Close to the top of the Catskill Front the old highway levels out. The horses must have been relieved, they had had a very hard haul up the mountain and now they had a little rest. But there was one more sharp turn. In the 19th century, that turn had brought travelers to within a short distance of the Catskill Mountain House hotel, but then it took them away. The highway had to climb one more great ledge and it zigzagged in order to manage that. That last ledge is the thick one that makes up the crest of the Catskill Front. It is the grand ledge that the old hotel stood on itself.

When we finally reached the top, we visited the hotel site and sat and gazed into the Hudson Valley. It had been quite a hike and we had passed through a lot of history. Before us was that ghost image of the old Acadian Mountains. As we pondered it all we realized that there was some pretty strange geology here. We were sitting upon the sandstones of the Catskills that, themselves, were made of sands from the Acadians. The death of one mountain range had given birth to another. Nature does wondrous things.

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

The Ghost Mountains – Devonian Pt. 14 – 10-3-19

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Ghost Mountains
The Devonian Part 14
The Greenville Press
Oct. 26, 2006

We have made a long journey through time. Last summer [2005] we started out along the highway in Leeds and visited the Helderberg Limestone there. Through 13 chapters we have traveled through a thick sequence of thousands of feet of Devonian age strata. Most of those are exposed along Rte. 23 and most of those are sandstones. All of these rocks were once sediments, mixtures of sand, silt and clay. Geologists have long recognized that thick sequences of sediment must have taken very long periods of time to accumulate. Our sedimentary sequence is estimated to have needed 50 million years or so to form.
But there is a second question. Where did all that sediment come from? Thousands of feet of sand a mud must have come from somewhere and it must have been somewhere very big, but where? The answer to that question takes us across the Hudson River and into the Berkshires. If you make this trip you will soon find very different sorts of rocks there. Visit Bash Bish Falls, in Columbia County, sometime and you will see rocks that are not sedimentary. Instead of being composed of sedimentary material, the rocks there are crystalline. We call this stuff gneiss and it formed deep within the crust of the Earth. There enormous temperatures and pressures “cooked” the rock and in that setting all the crystals were able to form. The marvelous thing about the Bash Bish Falls rocks are that they take us not only far back into time but also into the deep depths of the Earth’s crust. We are looking at rocks that formed many thousands, even tens of thousands of feet down.

We are looking at the bowels of an ancient mountain range. We have mentioned those mountains a number of times in past columns; they were the Acadian Mountains. The Acadians were an early version of the Appalachians. They began to form nearly 400 million years ago when a continent we would call Europe today drifted westward and began to collide with North America. The collision is duplicated today in Asia where India is Colliding with Tibet. The result is the great Himalayan Mountain chain. These are the highest mountains on Earth. The Acadians were very possibly just as tall.
Gaze eastward on the horizon and, in your mind’s eye, see the mountains that once were there. Their snow packed peaks are thought to have reached elevations of about 30 thousand feet. That means Bash Bish Falls and its rocks were once about five miles beneath the tops of those peaks. Climb to the top of Mt. Everest someday and then look down five miles into the earth and, presto, you understand Bash Bish Falls a lot better.
Here in Greene County we can’t see any crystalline rocks, but we can look into the depths of the Acadians. A record of those mountains is found along many of our area’s roadside outcroppings. Take a ride east on Rte. 23 to the famed outcrop on the off ramp that leads to Leeds. The rocks here display the deformations that come with two periods of mountain building. The strata stretching off to the left are Devonian in age. They dip steeply to the left. These strata were deposited as flat sheets on the bottom of the ancient sea floor. But now they are nearly vertical. What happened? They were affected by the deformation of the Acadian Mountain building event. As Europe collided with North America the crust here was lifted and crumpled. The strata were tilted steeply their original horizontality.

On the right side of the outcrop are even older rocks, dating back to the Ordovician Period, about 450 million years ago. These rocks were tilted twice. First, they were involved in a mountain building event called the Taconic Orogeny. Later they came to be tilted by the Acadian Orogeny. If you are an old sequence of strata then, eventually, you will become involved in multiple mountain building events. That’s why the angles of dip for the older and younger rocks are different. Two angles of dip – two mountain building events; it’s as simple as that.
If you continue down the off ramp and turn right, you will see a long low cliff across the road. There’s more mountain building to see there. The rocks of that cliff have been fractured. The fractures are nearly vertical and there are a lot of them. There has been some movement of the rocks along those fractures and so, technically, they are geological faults. You won’t confuse these with the San Andreas Fault; these never caused too much commotion. But you can see evidence of the motions. Some of the vertical fractures have coatings of the white mineral calcite on them. If you look very carefully you will see that the calcite has been striated. Striations are delicate scratches etched into the minerals during the motion. The blocks on each side of the fracture moved past each other and that caused the scratching. Once you have developed an eye for this you will find a lot of striations. Geologists call these slickensides.

If you return to Rte. 23 and head west, you will find more excellent cliffs of limestone. Stop from time to time along the fine cliffs here, you will soon see more evidence of mountain building deformation. A short distance down the road the strata are not only tilted, but they are folded as well. Watch the rocks carefully and you will large sweeping folds in some locations and tight complex folding elsewhere. It is a most remarkable thing to first observe folded rocks. After all, rock is pretty brittle stuff. Have you ever even thought of bending a rock?
The folds we see here are a testament to the enormous powers that are generated deep with the crust of the earth. Down there, the rocks have been heated to extraordinary temperatures and their deep burial has subjected the rocks to enormous pressures. Under these two circumstances, folding becomes a very plausible, indeed mandatory phenomenon.
But these rocks are not deeply buried within the earth’s crust; they are right at the surface. And that is the whole point. We are privileged to be looking deep into the earth’s crust while standing on its surface. How can that be? The answer is simple: the rocks that we see in Leeds were once buried under thousands of feet of other thick strata. That was hundreds of millions of years ago. And since that time weathering and erosion have been destroying the overlying rocks, the “overburden,” until nowadays what was once buried is now exposed. It is a remarkable thing but at Leeds we are indeed peering into the bowels of the Earth.

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

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