“Ramp and Pluck” — The Catskill Geologists

The Mountain Eagle; Jan. 26, 2018

Robert and Johanne Titus

  We have been nosing around, looking for geological features that work well in the winter. Last week we found an impressive view of Glacial Lake Schoharie, an image of that old lake that positively shined in the winter snow. That was on Rte. 145, just west of Middleburgh. Just a few minutes later, on the same drive, we stopped and took a good look at Vroman’s Nose, just east and again on Rte. 145. We noticed something we had not seen before. That’s this week’s column.

Take a good look at our photo. It’s a cross section view of the Nose; it’s the best view you can obtain. It show’s all the structure of what is called “ramp and pluck” topography. Notice that the right (north) flank of the mountain tapers off gently; its slope is relatively low. The left (south) flank, however, is far steeper. All this reflects the behavior of the glacier that once passed across the Nose.

That was the Schoharie Creek Valley glacier. It moved right to left, or north to south in our photo. The ice scoured its way up the north-facing ramp of the mountain. Then the ice passed across the crest of the mountain and soon it yanked, or plucked, an enormous mass of rock right out of the south side. That’s the south facing cliff. Well, hence the name ramp and pluck. It’s a very descriptive term, an unusually good choice of words for science.

Well, we already knew all this; we have been here so many times before. But on this visit, there was something different. It was in the snow. Notice the nice thick blanket of snow on the ramp side. Then see how the snow is nearly absent from the darker, steeper south facing slope. The plucked slope is a virtual cliff. Snow can accumulate on the ramp side but it cannot on the plucked cliff. The two sides stand out in sharp contrast, thanks to the snow.

None of this is terribly important; you won’t find anything like this discussed in a glacial geology textbook. But it is an aesthetic; isn’t it? And it helps train the eye, doesn’t it? And perhaps that does add some “importance” to what we are talking about. Geology is an experiential science; it is widely said that the best geologist is the one who has seen the most rocks. But, also, perhaps it is the best geologist who has seen the most rocks in the best way!

And that is the point here. We seem to have found a new way to look at geology in this season of the snow, and that new way is likely to offer insights as we continue our explorations. We intend to devote ourselves to noticing more winter images of this sort; there may be other interesting snowbound features out there.

But, in the meantime, it is training your eyes that we are interested in today. Ramp and pluck topography is important and common. Perhaps this is the time of the year when we should be looking for it. Perhaps you can keep out a sharp eye too.

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

The Schenectady landslide.

The Catskill Geologists

The Mountain Eagle; Feb. 2018

 Robert and Johanna Titus

Have you heard about the recent (2018) landslide in Schenectady? A mass of mud slid down a steep hill along Nott Terrace road and did major damage to two houses. It injured at least one person and left perhaps two dozen others looking for a home. This is the type of story that we have been covering for more than ten years now. Landslides are frequent geological hazards up and down the Hudson Valley and throughout parts of the Catskills. We think that this threat should be better known by you, the public.

    Reporter covers Landslide story on Albany Channel 10

We need to give you a little background first. Back in the later stages of the Ice Age, much of the Hudson Valley was submerged in a body of water called Glacial Lake Albany. That included all of the land that is now Schenectady and Rotterdam. The Mohawk River was a powerful flow back then, carrying large amounts of water from melting glaciers. It flowed into Lake Albany and carried huge amounts of sediment, which were deposited into what became a very sizable delta. Those deposits were mostly sand, silt and clay; when wet enough they become mud.

The lake eventually drained, and the delta was left behind, literally high and dry. It provided ideal conditions for people to settle. Delta tops are flat and easy to develop. It was simple to lay out roads. Settlers could build homes with deep, well-drained basements. Those homes were high enough above the Mohawk River so they did not have to fear flooding. It’s a remarkable thing to realize that both Schenectady and Rotterdam are where they are because of the Ice Age.

Over the millennia, rivers cut canyons into the delta and there lies the problem. Those canyons often have steep slopes and, when the delta deposits become wet from rainfall, they turn into mud and that mud can let go and slide downhill as mudslides. That happens from time to time. One of the most recent such events occurred in the spring of 2004. Heavy rain, the previous autumn, had soaked the ground at 1^st Avenue in Western Schenectady. The Mohawk River and an unnamed creek had eroded into the delta deposits there and created a steep slope, 80 or 90 ft. tall. When the slide began, it caused six houses to slowly subside. It is our recollection that they were all condemned. In January of 1996 a similar event occurred on Broadway, near Rte. 890 where Pleasant Valley Creek created a similar steep slope. That landslide, occurring after heavy rains, killed one man. The Nott Terrace slide is an event very similar to these.

As geo-journalists, we have been following this story for years. We have seen similar events in Delmar, Greenport, Rennselaer, Germantown and just a few years ago in New Baltimore. We fear that many more such slides will occur throughout the Hudson Valley, including at historic sites in Hyde Park. All of these slides involved the sediments of Lake Albany. These silty lake sediments soak up a lot of rainwater. When they reach a certain point, they become unstable. Great curved fractures open up and masses of earth slide along the curves of what are called rotational slumps.

All this is important; it is our region’s greatest geo-hazard. This will happen again.

Reach the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.” Read their blogs at “thecatskillgeologist.com.” Watch for their columns in Kaatskill Life and Upstate Life magazines. They are frequently in the Woodstock times.

Our reader’s rocks – Ice in Grand Gorge Gap?

The Catskill Geologists

Robert and Johanna Titus

Sept.15, 2017

We always give our email address at the bottom of each of our articles. And we can always be approached on our facebook page, so we hear from a lot of our readers. Often, they have questions, and we are usually able to help them with answers. Every once in a while, we thought we would answer one of these queries in the form of a column so here goes the first.

Recently we heard from a Gerry Hubbard. He sent us a photo of Grand Gorge Gap and wanted to know what the rounded hump on the right is. Take a look at our photo and you can see that hump. We had been wondering the same thing for years and so Gerry’s request got us to do something about the problem.

The first step is to get our topographic maps out and look at them. We found that the Roxbury 7 1/2 minute quadrangle map displayed the Gap. We found that the hump has a name; it is Jump Hill. Then we went back to our photo. The “hump” is actually something that lies in between two valleys. The contour lines on our map indicated a steep but steady slope for each of the two valleys. Each one of those is what geologists call a U-shaped valley. Every trained geologist on the planet Earth quickly recognizes the ice age history of such a valley. They record the passage of glaciers. As ice squeezed through a valley it ground away and eroded the bedrock. The shape that offers the least resistance is the U. Not surprisingly, over a period of time, glaciers will carve those U’s into the bedrock landscape. It gives each of them a path of least resistance. That forms a remarkably picturesque image and that helps make glaciated landscapes so attractive. We geologist are most fond of these U-shaped valleys.

Well, we studied the map and our photo and started speculating about what had happened here, way back, near the end of the Ice Age. Speculation is a word that scientists like to avoid; it sounds so – well speculative. So we use the word hypothesize instead. It sounds better. We hypothesized the following story: We hypothesize that the larger U-shape, on the left, is the older of the two. We think that a sizable glacier entered Grand Gorge Gap and began eroding the large U-shaped valley. Somewhere along the line, the ice was diverted and a second stream of it passed through what is the smaller, and we think younger, U-shaped on the right. All this erosion left Jump Hill in between.

We hope that Gerry likes our hypothesis. It conjures up quite an image. We travel north on Rte. 30 to where we can park and see this view. In our mind’s eyes we can imagine the advance of these glaciers; we can watch them carve the shapes of Grand Gorge Gap. That view gives us a whole new perspective on this site.

We hope you enjoyed our hypothesis. Perhaps you have a location that we could write about. Let us know.

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

A great glacial Lake

The Catskill Geologists

Mountain Eagle; Jan. 19, 2018

Robert and Johanna Titus

They say that you can’t make something out of nothing. “They,” of course, may well be wrong; it seems “they” usually are. We began to think such thoughts while traveling on Rte. 145 where, heading east, we were descending the hill on our way to Middleburgh. It was January, and that made the landscape covered with snow. And all that snow made the landscape before us all the more stunning. Take a look at our photo.

There, to the right of the highway, in all its snowy whiteness, was a great field of nothing. True, there were the remains of last summer’s corn, but the rest was broad, and flat, and white; it was indeed nothing. But not to us; we saw something; we were ready to do the impossible: to make something out of nothing.

We have written about this before; when a geologist sees a big flat nothing in the Catskills, then that geologist starts to think of a glacial lake. This one has a name; it is Glacial Lake Schoharie. The bottom of that lake was stretched out before us and it was big. When we got home, we got our maps out and found that the lake was about a mile across at Middleburgh. It stretched off to the north for miles and it did the same to the south.

But how deep was this lake? To answer that simple but important question we have to do a little elementary geology. We know that the Schoharie Creek Valley glacier dammed the valley to the north so just how did water get out of this basin? To find the answer to this, you have to continue to drive east on Rte. 145. You take a long hillslope up from Middleburgh until you reach an elevation of 1,200 feet. That’s a drive of about two miles. At the top of the hill, relatively steep slopes descend to the road. Soon you pass what is called Vlaie Pond. This location is the site of the Franklinton drain. Water from Glacial Lake Schoharie drained through this gap. It continued on down Catskill Creek as a very powerful flow.

The elevation at lake bottom, at the bottom of the hill, was at about 600 feet so that makes the old lake about 600 feet deep; that’s a lot of water.

If you make this trip we would like you to pull over and get out at the very top of the hill. Try to imagine the flow of water that passed through here late in the Ice Age. Look back to the west and see the lake spread out before you. It can be quite an experience to do this.

We have, in fact, written several articles about this lake in the Schoharie Creek Valley, but what impressed us this time is the impact of the view you get from the bottom of the hill. Look at our photo again. It nearly overwhelms you. We think it is one of those great experiences given to a geologist. It’s the sort of thing that we run this column in order to do.

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

The dance floor at Vroman’s Nose

The Catskill Geologists; The Mountain Eagle, Jan. 2017.

Robert and Johanna Titus

The local geological news, this week (July 2017), is that Vroman’s Nose, a hill that is found a short distance southwest of Middleburgh, has become the property of the Department of Environmental Conservation (DEC). The hill has long been recognized for its scenic beauty. If you look up at it, you will see a distinctive profile. The south slope is steep, almost a cliff. It rises about 600 feet above the floor of the Schoharie Creek Valley. And that gives the hill its other scenic aspect. If you look down from the edge of this south facing slope you will obtain a sweeping view of the Schoharie Creek Valley (see, our photo).

Vroman’s Nose had been, for decades, the property of a group called the Vroman’s Nose Preservation Corporation (VNPC). The hill, back in the early 1980’s, had been threatened. There had been talk of the building of a restaurant at its top. That would have ruined both scenic views so, not surprisingly, the VNPC came into existence. The group raised the money needed to buy the land and has managed it as a local park ever since. In recent years much larger numbers of visitors have been climbing the Nose and the VNPC began looking to the DEC for help in managing the site. Now the DEC will take over responsibility for the 139 acre property. It will now be known as the Vroman’s Nose Unique Area and the State will protect its natural resources and accommodate public use.

Today we would like to describe why you should plan a future visit and what you will see there. To get there, take Rte. 30 south from Middleburgh and turn right at Mill Valley Road. Nose parking can be found about a half mile up the road. The Nose Loop Trail climbs 600 feet but it is rated as an easy hike. At the top you will find yourselves at what is commonly called “the Dance Floor.”  That is a substantial ledge of Devonian sandstones (again, see our photo).

You don’t have to be a professional geologist to notice that there is something very interesting here. The Dance Floor is remarkably flat, and so smooth it looks polished. If you take the time to walk around and look it over you will soon notice that there are long straight scratches in this surface. There is not a professional geologist anywhere in the world who would not immediately see the ice age history recorded here.

The Dance Floor is the product of the Schoharie Creek glacier that, perhaps 15,000 years ago, flowed across its surface. Glaciers possess large amounts of sand, especially at their bottoms, and that makes them behave in a fashion that reminds the two of us of sandpaper. The Schoharie Creek glacier was, in effect, a large, thick and very heavy sheet of sandpaper. As it flowed across Vroman’s Nose, it ground into the bedrock and smoothed out the Dance Floor.

That same sheet of ice dragged cobbles and perhaps even boulders across this same surface. In so doing those long straight scratches came into existence. They are called glacial striations. They are oriented roughly north to south and that records the down-the- valley motion of the ice.

The Dance Floor is one of the very best locations to see such ice age features and it is well worth the hike to do just that. We like the site so much that we have started to call similar glaciated bedrock locations “dance floors.” You should become familiar with such things; there are a lot of them.

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

A day in the lives of some very ancient worms.

The Catskill Geologists

Robert and Johanna Titus

Dec. 22, 2017

To live the life of a geologist is to experience some truly stunning moments. To stand on the edge of the Grand Canyon, to gaze at rocks that are billions of years old, to find a perfect fossil or crystal; they are all unforgettable moments. But, in a way, finding genuinely ordinary moments from the distant past are also parts of the trade and, indeed, important parts.

We were walking along one day, when we found a nearly dried-up mud puddle and there, before us, was a wonderful geologic feature – a worm! Well, not just a worm but several trails that it, and its buddies, had produced. See our first photo. It had recently rained and those worms had been driven out of the waterlogged ground. They crawled around for a while and left those trails behind.

Well, we can imagine your response to all this – and you may not be all that thrilled. So, let’s continue and describe something else that we frequently encounter – fossil worm burrows. Take a look at our second photo. It shows a stratum from the bottom of the Devonian age Catskill Sea. It’s just a run-of-the-mill rock that became, perhaps, a bit more interesting by having been deposited at the floor of an ancient ocean. This really was the bottom of the sea. Later these sediments hardened into rock. We like to step up on to such rocks and talk about standing on the bottom of that ocean. That’s a bit goofy but it is fun.

What becomes even more interesting is when we combine these two commonplace features – and come up with an ancient sea floor and some ancient worms. And that is what you see in our second photo. We found this rock in our backyard, so it didn’t take a lot of hunting.

This is one of those things we want you to, having been reading our columns, become familiar with. These are genuine fossils and they are out there, waiting to be found by you. These are not bones or shells or teeth; these are what geologists call “trace fossils.” They record the activities of long ago animals, activities that left traces in the sediments that came to be hardened into rocks.

They record a few moments or a few hours in the lives of those very ancient creatures. Those creatures were just worms but we still think that is something.

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

Our reader’s Rocks: Mt. Tremper fossils

The Catskill Geologists

Robert and Johanna Titus

Robert and Johanna: Attached are some photos of fossils I found at Mt. Tremper. I would love to know more about them Linda Senft

   Linda: Thanks for your photos. We enjoy getting things like this in our email. We too, have spent time exploring the Mt. Tremper vicinity. We described the stone used in building the Zen Mountain Monastery there in one of our recent Kaatskill Life articles. In many ways your fossils seem unremarkable. These are just commonplace fossils, found throughout our region. And, as is also common, none of them are especially well preserved, most of them are just broken fragments. But, we don’t want to do an injustice to these ancient animals; there is so much more.

The gray rock in which they are petrified is, without any doubt, limestone. That, all by itself, conjures up quite some fine images. Limestone almost always forms on the floor of a shallow, tropical sea. The best examples that we know of, are found in the Bahamas, or off the western coast of Florida. Have you been? If so, then you can conjure up images of shallow, sparkling, aqua-colored seas. If you look around Mt. Tremper, you will quickly see that things have changed!

The fossils that we can identify are the ones with ridged surfaces. These are animals, shellfish that are called brachiopods. We described and illustrated them earlier this year, in our June 16^th article. Brachiopods are a group of shellfish that you should acquaint yourselves with; they are enormously common in Devonian marine sedimentary rocks. Wikipedia can help you a lot.

Brachiopods are still alive, but there are only a few hundred species still found.
There are tens of thousands of species in the fossil record. The Devonian time period was a very good stretch of time for these invertebrate animals. We find thousands and thousands of them here in the Catskills so, you can see why we urge you to become knowledgeable of them.

During the Devonian, brachiopods littered the floor of the Catskill Sea. They lived simple lives; they drew water into themselves and filtered bits and pieces of nourishing biological materials out of that water. That was their food. They are called filter feeders. It wasn’t exciting but they got by just fine.

In many ways, what makes your fossils even more interesting is where you found them. Mt. Tremper is composed and sandstones and shales that accumulated on the Devonian Catskill Delta. We have written about that from time to time. We promise you, these brachiopods did not live on the dry lands of the Catskill Delta.

Those limestones, your fossils were found in, were also not formed on a delta; they formed in that shallow sea. These limestones belong to a unit of rock called the Helderberg Limestone. It is found up and down the Hudson Valley and also along the southern flank of the Mohawk Valley. It is found in Mt. Tremper, but it is buried under a few miles of sandstones and shales. These limestones did not work their ways to the surface; they were brought to Mt. Tremper by glaciers.

If you look at a map you can soon trace the likely path they took to get to Mt. Tremper. We know that glaciers came down the Hudson Valley. Along the way, the ice scooped up these rocks from exposed Helderberg limestone outcrops. We know some of the ice turned west and rose up the valley of Esopus Creek. These limestones were dragged to Mt. Tremper and that is where the Ice Age ran out of steam. The climate warmed, the glaciers melted, and these rocks were left behind as part of the debris of a major glaciation.

Well, at first glance, we found these fossils to be “unremarkable” but after thinking a little while, we believe they tell us a wonderful story, a story about an ancient tropical sea and a not quite so ancient ice age glacier.

Linda, now you know more about your fossils.

Contact the authors at randjtitus@prodigy.net. Join their facebook age “The Catskill
Geologist.” Read their blogs at “thecatskillgeologist.com.” You can find them in Kaatskill Life magazine and sometimes in the Woodstock Times. They are just about everywhere!

Landslide hazards?
The Catskill Geologists                                                                                         Robert and Johanna Titus                                                                                          The Mountain Eagle; Dec. 8, 2017

Did you hear the news of the recent landslide, across the Hudson in the town of Greenport? It occurred at the Sons and Daughters of Italy Club on Bridge Street, right along the banks of the Claverack Creek. Several hundred yards of earth slid into the creek. This was something called a rotational slump. A large mass of earth becomes unstable. Then a sizable curved fracture opens up and the whole overlying mass slides downhill. The slide follows the fracture in a rotational fashion, hence the name. When all is done, a nearly vertical cliff is left behind at the “head” of the slide. See our photo. The bottom, or “toe” of the slide, is a chaotic mass of earth that might very well dam any stream that lies below it. That happened at Greenport and a lot of engineering had to be done on the fly in order to keep Claverack Creek from flooding its own valley.

What surprised us was that the same stretch of the Creek had seen a very similar slide only 11 years ago. We covered the story for another newspaper that we wrote for back then. The surprise wasn’t so much where and when the slide happened but in other things.

Back in 2006, just before the first slide, there had been a long period of heavy rainfall.
We had been watching this, and we saw problems developing. We reasoned that the heavy rainfall would soak into the ground and destabilize all the lake deposits along river banks such as on the Claverack. You see, that river flows across the deposits of a large glacial lake. At the close of the Ice Age, the lower Hudson Valley had been flooded by the waters of something called Glacial Lake Albany. The lake basin accumulated thick sequences of silt and clay. If you visit the Greenport vicinity, watch for all the flat landscape. Those lands formed on the floor of the lake.

Rivers, such as the Claverack, have an easy time cutting through such deposits.
They can cut steep banks into the lake deposits and that’s part of the problem. The difficulties really begin when rainfall picks up. Water soaks into the lake deposits and they start to weigh too much. The water makes them too heavy and it also makes them somewhat fluid. Those fractures form and then, abruptly, the slide occurs. We suspect that the slides are very quick, but we have never heard an eyewitness report so we don’t know for sure.

Our greatest surprise with this slide is that it did not occur during a particularly wet season. It just has not been raining all that much in the year of 2017. Those lake deposits could not have weighed all that much, and they would not have been very fluid. So, why did the slide occur? We don’t know and that alarms us.

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

Landslide hazards?
The Catskill Geologists                                                                                         Robert and Johanna Titus                                                                                          The Mountain Eagle; Dec. 8, 2017

Did you hear the news of the recent landslide, across the Hudson in the town of Greenport? It occurred at the Sons and Daughters of Italy Club on Bridge Street, right along the banks of the Claverack Creek. Several hundred yards of earth slid into the creek. This was something called a rotational slump. A large mass of earth becomes unstable. Then a sizable curved fracture opens up and the whole overlying mass slides downhill. The slide follows the fracture in a rotational fashion, hence the name. When all is done, a nearly vertical cliff is left behind at the “head” of the slide. See our photo. The bottom, or “toe” of the slide, is a chaotic mass of earth that might very well dam any stream that lies below it. That happened at Greenport and a lot of engineering had to be done on the fly in order to keep Claverack Creek from flooding its own valley.

What surprised us was that the same stretch of the Creek had seen a very similar slide only 11 years ago. We covered the story for another newspaper that we wrote for back then. The surprise wasn’t so much where and when the slide happened but in other ways.

Back in 2006, just before the first slide, there had been a long period of heavy rainfall.
We had been watching this, and we saw problems developing. We reasoned that the heavy rainfall would soak into the ground and destabilize all the lake deposits along river banks such as on the Claverack. You see, that river flows across the deposits of a large glacial lake. At the close of the Ice Age, the lower Hudson Valley had been flooded by the waters of something called Glacial Lake Albany. The lake basin accumulated thick sequences of silt and clay. If you visit the Greenport vicinity, watch for all the flat landscape. Those lands formed on the floor of the lake.

Rivers, such as the Claverack, have an easy time cutting through such deposits.
They can cut steep banks into the lake deposits and that’s part of the problem. The difficulties really begin when rainfall picks up. Water soaks into the lake deposits and they start to weigh too much. The water makes them too heavy and it also makes them somewhat fluid. Those fractures form and then, abruptly, the slide occurs. We suspect that the slides are very quick, but we have never heard an eyewitness report so we don’t know for sure.

Our greatest surprise with this slide is that it did not occur during a particularly wet season. It just has not been raining all that much in the year of 2017. Those lake deposits could not have weighed all that much, and they would not have been very fluid. So, why did the slide occur? We don’t know and that alarms us.

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

The Depths (?) of a sea,

The Catskill geologists,

The Mountain Eagle, Dec. 1, 2017

Robert and Johanna Titus

Have you ever been to Manor Kill Falls? You take Rte. 30 to where it intersects Rte. 990-V and then you head north a few miles and then watch for the signs. They have a fine parking lot and then you have a choice of trails. The upper trail heads for the top of the falls, but we want you to take the lower trail. That one takes you down to the bottom of the falls where you get a fine scenic look at it. That’s where the best geology is too.

You stand at a good location and look up at the falls. If you have an eye for rock types then you will recognize a sequence composed mostly of thinly bedded black shales. These strata are interrupted with the occasional dark sandstone. That’s a good start but now you need to get a better look at these rocks. You can do that by looking down; the ground is littered with rocks. A thin “shingle” of black shale will reveal a very fine-grained sedimentary rock; it is composed of silt and clay. None of those grains are large enough to be seen. It is black from all the organic matter in it – the stuff of ancient life.

It is natural for a geologist to begin looking for fossils. Those provide the clues for figuring out exactly what kind of environment is represented here. The hunting was disappointing at first but, after a short while, the fossils of some shellfish were turned up. These were creatures called brachiopods. Like clams, they have two shells, and like clams, they spent all of their lives lying on the seafloor. But they are not clams; they have a very different anatomy, so different that they are not even distant cousins of clams.

Nevertheless, these brachiopods are marine animals, and they tell us that all the strata we are looking at were formed, about 390 million years ago, at the bottom of something that is often called the Catskill Sea. Stand back at look up again. Each horizon of stratified rock once took its turn being the floor of that ocean.

Well, now we know something important; The Manor Kill Falls location was once the bottom of a large ocean. The next question that comes to mind, to a geologist anyway, is “just how deep was this ocean?’ We can’t throw a plumb bob overboard so just how do we determine this important bit of information. The answer is that we don’t, we can’t. But we can make some approximations.

Here’s how we do that? We have already looked those lithologies over and we have found that most of the bedrock here is fine grained black shale. That’s a type of rock that forms in relatively deep waters. The black color speaks to us of a relative scarceness of oxygen on that sea floor. That black biologic material would have decayed away if there had been oxygen. We did not find many fossils so not too many shellfish lived down there.

We thought we were building a case for a very deep-sea environment, but then we found something else. That something else was downstream. There we saw a slab of rock covered with what are called ripple marks. Take a look at our photo. These are slightly asymmetrical ripples and that indicates that these were sculpted by currents passing across that sea floor. What does that mean? Ripples are rare in very deep waters. It means that this seafloor was not all that deep.

We stood on that slab; we were literally standing on the bottom of an ancient sea. We looked up and, in our mind’s eyes, we could see the dimness of just a little sunlight that had reached down to this seafloor. It just wasn’t that deep.

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