Fossil Collecting at Westmoreland State Park, Virginia

Adriane here-

An aerial view of Horse Head Cliffs at Westmoreland State Park overlook the Potomac River. The beautiful parallel layers of sediment contain fossils. Image courtesy of the VA Department of Conservation & Recreation.

Every now and then (well, as often as I can to be honest), I go fossil hunting with family, friends, and colleagues just for fun! There’s nothing like finding the remains of extinct animals and plants out in the field yourself. Although there are very few places where fossil collecting is prohibited, there are very few state parks and places in the US where it is encouraged. One of these places is Westmoreland State Park in Montross, Virginia.

This very well may have been the first place I found my very first fossil. I remember my dad had taken my siblings and I to the park one Saturday afternoon to play in the Potomac River and in the creeks and marshes nearby. But, once he told me we could find shark’s teeth on the river banks, my eyes were glued to the sand, systematically sweeping the ground in front of me. Lo and behold, I did find a shark’s tooth! And, it was a tooth that belonged to Carcharodon megalodon (or just Megalodon for short), one of the largest sharks to ever cruise the Earth’s oceans!

Stratigraphy of Westmoreland

Sifting for fossils on the banks of the Potomac River.

Westmoreland State Park is known among locals for its fossils, but any Virginia geologists will tell you the real gem of the park is its stratigraphy (well, OK, the fossils too). The oldest sediment that contain the fossils was laid down in a shallow extension of the Atlantic Ocean about 23-25 million years ago, during the lower Miocene. Younger sediments from the Pliocene (~5.3-2.5 million years ago) and Pleistocene (~2.5-0.01 million years ago) were laid atop the older Miocene deposits. Together, these different rock and sediment layers are called the Chesapeake Group. In the study of rock layers (=stratigraphy), a group includes different rock formations, each with their own name. For example, the Miocene formations in the Chesapeake Group (at least in parts of Virginia) are called the Calvert and Eastover formations.

After these formations were deposited, sea level dropped as glaciers on Greenland continued to grow. This allowed for rivers to flow further out into what was once a sea. Rivers are very powerful eroding mechanisms, as they have the capacity to move large boulders and wear down rocks (think of the Grand Canyon; it was made by the Colorado River cutting through the rock over time!) One of the rivers that now flows into the Atlantic Ocean is the Potomac River. This river is now eroding the Chesapeake Group formations, releasing all the fossils that were once contained in the rocks. Thus, some of these treasures wash ashore at Westmoreland State Park for visitors to find!

Fossils of Westmoreland

A small C. megalodon tooth found at Westmoreland State Park.

Over nearly a decade of visiting Westmoreland State Park, I have accumulated hundreds of shark teeth and found tons of other fossils. Some of these include whale teeth, vertebrae, rib bones and ear bones, dolphin teeth, vertebrae, rib bones and ear bones, fish vertebrae, shark vertebrae, coprolites (fossil poop), an alligator tooth, and mammal teeth. Most of these fossils are Miocene in age, but some are from the Pliocene and Pleistocene.

One of the most famous fossils to come out of the Chesapeake Group are those of the baleen whales. Several new species of whales have been found in Virginia in formations from the Miocene and Pliocene. One of these species, Eobalaeonoptera harrisoni, was found only five minutes down the road from my home in Virginia! E. harrisoni is a beloved icon of the area, in which it was found, so a complete cast of the whale now hangs in the Caroline County, VA visitor’s center.

The cast of Eobalaenoptera harrisoni that can be visited in the Caroline County, VA visitor’s center. Image from the Virginia Museum of Natural History.

Rocky Mountain Field Trip

Megan here-

Image 1. Grand Teton National Park (in the red ellipse) is located in the northwest corner of Wyoming, just south of Yellowstone National Park.

An exciting perk of attending the University of Wyoming for graduate school is the annual Rocky Mountain Field Trip. This year, the geology faculty planned an adventurous trip to Grand Teton National Park and its surrounding areas (Image 1). Over five days, current and new graduate students explored the unique geology of the Tetons by learning about mountain formations, glaciation, and sedimentation in northwest Wyoming. By the end, we were able to develop an understanding of how this stunning area formed, and how it may change in the future.

Image 2. The view from AMK Ranch stretches across Jackson Lake to the Tetons. This photo looks southwest and shows the northern part of the north-south trending range.

For the first few days of the trip, we were lucky enough to stay at the AMK Ranch, which is home to the University of Wyoming-National Park Service Research Station. From here, we had a stunning view of Grand Teton National Park’s most impressive features: the high-standing peaks of the Teton mountain range (Image 2). These mountains are tremendously tall (the Grand Teton’s peak is 13,775 feet in elevation) due to a complex tectonic history of extension and uplift. Essentially, the mountains uplifted while the valley to the east dropped down. The pointed horns of the Tetons are a result of glacial sculpting during the Pleistocene Epoch.

One of the best parts of this trip was the variety of geology and geologists (Image 3). We learned about glacial geology, sedimentology, structural geology, hydrogeology, paleontology, and so much more. The professors and guests who joined us along the trip had a massive breadth of geologic knowledge. Not to mention, we were able to explore a national park with a geologic lens. That’s one of the most exciting things about being a geologist; you can look at landscapes with towering mountains and glacial lakes, or with meandering rivers and rolling hills, and you can envision the multitude of processes that formed that landscape.

Image 3. New and returning graduate students, UW professors, and even the UW provost mimic the pointed peaks of the mountains on a hazy day in Grand Teton National Park. Photo courtesy of Robert Kirkwood.

 

Field Camp in Scotland

Maggie here –

I recently returned from a five-week field camp in Scotland. Field camp is a course that most geologists participate in that is intended to teach students how to collect geologic measurements in the field, recognize geologic structures like folds and faults, understand age relationships of the rock, and ultimately make sense of all of this by making maps and cross sections (interpretations of what the surface geology looks like underground). Field camps are incredibly important as geology students because it reinforces the ideas that the best geologists are those that have seen the most rocks and that geology needs to be learned outside, not just in the classroom.

Figure 1. Geologic map of Scotland. From the key you can see that Scotland has a lot of different rock types that represent much of the time in Earth’s history. The dashed yellow lines that have been drawn in follow the path of two major faults in Scotland; the Great Glen Fault to the North and the Highland Boundary Fault to the south.
So, why Scotland for field camp? Scotland is an interesting location geologically, because for much of Earth’s history it was essentially a ping pong ball with sections of the country getting added on by collisions with other continents as it bounced around. If you look at a map of Scotland you can see two almost parallel lines dividing the country into three pieces (Figure 1). The top most fault is the Great Glen Fault which runs through the city of Inverness and Loch Ness (where the Loch Ness monster resides). The fault further to the south is the Highland Boundary Fault which does divide the country into the Highlands and Lowlands. Each of these pieces was accreted (added on) during a different collisional event. Surprisingly, the last, and youngest, collisional event that happened, when Baltica (Northwestern Europe) collided with Laurentia (North America, Greenland, Scotland), deposited the oldest rocks that you can see in Scotland. These rocks are ~3.2 billion years old and they lay on top of limestone that is ~540 million years old (Figure 2). Seeing this age relationship in the field tells us that something crazy was happening geologically!

Field camp is a lot like summer camp mixed with a typical college class-there is a lot of fun to be had with fellow rock nerds, but also a lot of learning and homework to be done. On a typical day we would leave our hostel or house by 8:30am, work in the field, mapping and collecting data, (either in small groups or individually), leave the field around 5pm, go home and cook dinner for your small group, then work on interpretations of our data and prettying up our maps. Usually at the end of the week we would have a larger project to hand in based on the maps that we had made that week and our interpretations of the area (Figure 3).

Going to field camp can seem daunting at first, especially if you are going on one outside of your home country, but truly is an important experience in learning to be a geologist. Like practicing a sport or instrument, you have to practice geology skills in order for them to become second nature and field camp is the best place for that practice. For a lot of people, this is where geologists have their first “I am a geologist” moment. So, for anyone who wants to be a geologist (or paleontologist or other earth scientist) get outside and look at some rocks and fossils and start observing, because the best geologist has seen the most rocks!

Figure 2. “The Sandwich” roadstop. In this image the red dashed lines represent two thrust faults from the Moine Thrust in northwestern Scotland. The bottom of the sandwich in the left bottom corner of the picture is 540 million year old rock, the middle is 3.2 billion year old rock, and the top of the sandwich is 1.2 billion year old rock. The geology of the Moine Thrust is still being studied due to the complex nature of the rocks in the area.
Figure 3. Summary map of the Ross of Mull (Isle of Mull off the West coast of Scotland) based on five field localities. The areas that are boxed in and shaded darker are the field localities visited by our group with the rest of the map shaded based on interpretations of the area. This map is pretty typical of a final project that we were asked to complete for each region that we were in during field camp.

Field Trip to the Mohawk Valley, New York

Adriane here-

Students collecting fossils in the Lower Devonian (~410 million year old) rocks.

Every Spring, UMass takes its Historical Geology class on a weekend field trip to the Mohawk Valley in New York. The purpose of the trip is to show students the formation of an ancient ocean that once covered North America ~450 million years ago in the Ordovician and talk about the ancient environments that animals lived in. We also take the students to some locations on the second day of the trip to rocks that are a bit younger (~410 million years old) so they can collect fossils. In addition to talking about tectonics and fossils, we also show the students some really great sedimentary structures preserved in the rock record.

Some fossils that were collected on the trip. Red circle is around two brachiopods found on the first day; blue circles are around two trilobite heads found in the Utica Shale.

The first stop of the day involved looking at older limestones of early Middle Ordovician age in an abandoned rock quarry. At the second stop, we looked at finer-grained shales that were deposited in a deeper portion of the ancient basin. At the third stop of the day, we investigated the Utica Shale, one of the largest shale deposits on the east coast, and one that is commonly targeted by oil and gas companies because it produces these products at the right depths in the Earth. Here, we all found trilobite pieces (and a few whole specimens). The last stop of the day involved walking down to a waterfall on Plotter Kill Preserve (not really a welcoming name for a park) and investigate the shallowing or infilling of the ancient basin. In addition to beautiful scenery, there are also some really great sedimentary structures preserved at this location.

Raquel (left) and I (right) demonstrating the Taconic Unconformity. The younger Devonian rocks on the right are tilted, but the older Ordovician rocks on the left are standing straight up. Where the two formations meet, there is about 50 million years missing.

The second day of the trip is always the highlight of the weekend, at least for me! Our first stop was the Lower Devonian limestones of Schoharie, NY, which are highly fossiliferous. After we spent a few hours at this locality, we took the class to a locally famous locality called the Taconic Unconformity. Here, rocks of Middle Ordovician age (~460 million years old) are against Lower Devonian rocks (~410 million years old), meaning that a huge chunk of time (the entire Silurian Period) is totally missing. The unconformity is really apparent because the older Ordovician rocks are standing almost straight up, whereas the Devonian rocks are less tilted.

Flute casts preserved on the bottom of a rock formation. From these markings, you can interpret which direction water was flowing (indicated by the pink arrow).

The last stop of the field trip was to another locally famous and well-loved locality called ‘Dinosaur Skin’. This name is wildly misleading, as the rocks here were formed about 250 million years before the first dinosaurs roamed the Earth, although the sedimentary features preserved in the rock do resemble dinosaur skin. Instead, the features preserved in the rocks at this location are called flute casts, which are a type of sole mark, a sedimentary feature that is formed and preserved on the bottom of sedimentary beds. In the Middle Ordovician, there were intense storms as well as earthquakes as other pieces of continents and island arcs collided with the east coast of ancestral North America. These caused sediment instability in the form of turbidites, which can be thought of as underwater landslides. So, the Dinosaur Skin is actually scoured sediment that was preserved in the rock record.

Ancient Environments of Western Kentucky

Jen here –

Pentremites tulipaformis, a common blastoid found at this location.
This past weekend several students, myself, and my lab mate Maggie went to a fossil locality near Hopkinsville, Kentucky. This rock is from the Mississippian and this locality is particularly interesting to me because of the amount of blastoids you can find in a single moment. They are falling right out of the rock! So we went with a specific question to answer. We are looking to better understand the gap in fossil preservation within some of the blastoids there. Let me explain some – there are specimens that range from 0.25 – 15 mm in height. But most scientists ignore everything below 5 mm because it falls apart more easily than the larger specimens.

Recently we have examined some of the very tiny (0.25 mm) specimens and we are interested to see how the growth of the organism may be affecting its ability to preserve in the rock record! So we did some surface collecting – looking around on the ground and picking up specimens that we can see with our eyes. We also did a lot of bulk collecting. By bulk collecting I mean we filled buckets of sediment with a shovel to take home with us. We will then sieve all the sediment to differentiate the different sizes of the specimens. We will have several different sieve sizes from 5 mm all the way to 64 microns (very tiny material). We will clean everything so that we can sort through the different sizes to find what we are looking for – pieces of small blastoids!

Maggie and Chris close up and Michael in the background. Collecting fossils and enjoying the beautiful weather!

The fossils are found in limestone beds (see by Maggie’s leg – there is a bench like extension from the rock) and in the shale layers (drab gray colored rock that makes up most of the bottom) that occur between the limestone beds. The big rock on top of them is sandstone and is part of an ancient river system.

Barrier Island System of Plum Island, Massachusetts

Every year in February, we (well, my advisor and his TA, which has been me the past two years) take our Historical Geology class to a fantastic barrier island system on Plum Island, MA. First of all, a barrier island is a type of landform that forms parallel to a shoreline, and is usually characterized by a beach, dunes, and a back dune area, which can be a marsh, lagoon, or other wetlands. We do this for several reasons, but mainly, so the students can see how different a beach looks during the winter, and to help them imagine how sea level will affect the  main environments (beach, dune, marsh) at Plum Island.

 

plumisland
The three environments of Plum Island, from left to right: beach, dunes, and marsh. Note these environments are covered with snow, as New England had previously experienced snow storms.

As sea level changes, environments are pushed backward (during a sea level rise) or migrate out towards the ocean (sea level fall). Currently, as glaciers melt due to global climate change, sea level is rising at an alarming rate. This means that the environments at Plum Island will begin to be pushed backward.  During times of sea level rise, we call this a transgression. This means that the beach will move to where the dunes currently are, and the dunes will migrate back to where the marsh is. The marsh will be pushed back more inland. But what will this look like in the rock record? Beach sand, when turned into rock, is called sandstone. Dunes will also turn into sandstone, but will exhibit angular bedding, called cross bedding. Marshes are characterized by very fine sediment, such as clay and silt, as well as lots of organic material (decaying grass, organisms, poop, etc.). Thus, marshes will be represented by siltstone, mudstone, and/or coal in the rock record. These environments are stacked on top of one another as they migrate landward. Thus, in the rock record, geologists would see sandstone, maybe with some shells (beach), topped with more sandstone that has abundant cross bedding (dunes), topped by siltstone/mudstone/coal (marsh).

beach_stacked
A cross section view of beach, dunes, and marsh environments. As sea level rises, the environments move toward land, or to the right in this image. In the rock record, these environments will appear stacked on top of one another.