Rattlesnake Creek Fossil Collecting

Jen here – 

Action shot of folks collecting in the creek. Taken by Victor Perez of the Florida Museum.

I recently went on a fossil collecting trip associated with a FOSSIL Project workshop on digitization and imaging of fossils. To preface this, whenever you are looking to go fossil collecting you should make sure to be aware of the laws and rules in place in your town. The spot we were heading to abuts private land so one of the coordinators made sure to reach out to them ahead of time to request permission and explain what we were doing. To give back to the community, we also cleaned up the creek while we were looking for fossils. There is always trash or debris and this is an easy way to give back to the community you are hunting in! 

In Florida, you have to prepare to be out in the heat. Surprisingly the creek was pleasant and we were pretty shaded for most of the day. I wore a UV protectant shirt, shorts, sandals, and a hat. Insects can really get you, so it’s also best to know what to prepare for and use lotion or bug spray to prevent any spread of disease.

I was mostly observing and helping facilitate this trip but I was excited to see others getting really into the fossil collection. This location is in the Coosawhatchie Formation which is Miocene (~23-5.3 million years ago) in age. It overlies the Eocene (~56-33.9 million years old) Ocala Limestone. The Ocala Limestone fossils are very different from the Coosawhatchie so they are pretty easy to distinguish from one another. Most folks were finding shark teeth, ray plates, clams, snails from the Coosawhatchie Formation and things like small echinoids and large benthic foraminifera from the Ocala Limestone. Specimens from the Ocala Limestone were often a white-cream color whereas specimens from the Coosawhatchie were very dark.

Hemipristis serra specimen collected by Corinne Daycross. Check out her specimens on myFOSSIL.

 

We also spent some time observing the local insects and sharing education apps for identifying fossils and modern life! Workshop participants were from all over the country so there was some regular chit chat and getting to know one another. I had known several participants for some time from various online platforms so it was really great getting to meet them in person! If you want to check out what the group was up to here is the myFOSSIL group that everyone was posting in: Imaging and Digitization for Avocational Paleontologists Workshop

Eagle ray plate found by Corinne Daycross. Check out her specimens on myFOSSIL.

I was also helping my friend and collaborator, Rich, with a study. He was interested in thinking about participant dynamics at workshops and field trips. So we had a matrix and were recording interactions between participants at the workshop and facilitators (/people running the workshop). He then also gave everyone a survey to see how people’s perception of who they interacted with matched what we observed. They were pretty close but perceived interactions were higher, which could be due to a variety of things. It has been really fun getting into some of these observational studies!

Check out the summary blog post on myFOSSIL about the event: Imagining and Digitization Workshop

Group photo of everyone after we had been hunting in the creek. By Jeff Gage at the Florida Museum.

The Climate is Changing, and it’s Getting Personal

Megan here-

The Ilulissat Art Museum, which opened in 1995, was originally the colony governor’s residence that was built in 1923. Today, it’s home to around 50 works by Emanuel A. Petersen as well as rotating exhibits by local Greenlandic artists.

The Ilulissat Art Museum is a charming red house with robin’s egg blue trim nestled up against a grassy hillside in the town of Ilulissat, Greenland. Almost 5,000 people live in this seaside town, including the art museum’s cheerful and friendly curator. His face lights up at the prospect of new visitors, and he enthusiastically greets us as we enter. This kindly curator shows us around the museum, offering us a wealth of knowledge about the paintings and the artists. He tells us that the lower level is primarily for paintings by Emanuel A. Petersen, a Danish painter who spent time in Greenland in the early 20th century. His paintings depict tranquil yet breathtaking scenes of the landscape surrounding Ilulissat and other Greenlandic villages. Many show icebergs stoically floating in the fjord, and tall, snowy mountains colored pink from the alpenglow. Some paintings have boats and kayaks out at sea, while others depict sleds led by teams of thick-coated dogs. While each scene may be different, each of Petersen’s paintings is so uniquely Greenland. 

It’s no wonder Petersen produced enough paintings to fill an entire floor (not to mention the 150+ pieces of his artwork at the museum in Greenland’s capital, Nuuk). The landscape around Ilulissat is an alluring contrast of rounded green hills and blue-white icebergs. No more than 20 kilometers inland, the Greenland Ice Sheet spills out into channelized outlet glaciers like Jakobshavn Isbrae–the fast-flowing ice stream that produces the icebergs occupying Ilulissat’s fjord. Up and down the coast of Greenland, glaciers flow from the ice sheet and fill the valleys and fjords with ice.

Many local Greenlanders travel over this ice, including our friendly museum curator. He has a team of six sled dogs–which we’re told is a relatively small team–that pulls his sled across snow and ice. For years, he and his wife have been traveling with their sled dogs to a spot along the margin of the ice sheet. There, an outlet glacier flows into a water-filled valley with rocky hills forming the sides. Just a few years ago, the curator and his wife arrived at this spot and were met with a great surprise: a barren, rocky island protruded from the water in the middle of the channel. Had they never been there before, this would not have seemed odd. But this was a brand new island that was recently uncovered as the nearby glacier retreated up the fjord. Up until then, that spot had been covered with ice year-round, and no one had known that a small rocky protrusion lay beneath. 

I was fascinated by his story and as I listened, I mentioned the words “ice retreat.” At that, the curator’s eyes lit up and with both passion and relief, he said, “Exactly.” It was clear that he needed us to understand his personal relationship with climate change. This was the first time I had met someone who has been so directly affected by warming temperatures and melting glaciers.

The island hasn’t made it on all the local maps yet, but it now has a name that means something like “the bald one” in English. In fact, this isn’t the only new island that has been uncovered by retreating ice. In the past twenty years, Steenstrup Glacier in northwest Greenland has also revealed a handful of new islands (2014 article, 2017 article). The effects of climate change in Greenland are complex–both for the ice sheet, the people, and the wildlife. In some cases, melting ice actually benefits certain Greenlandic industries like mining, fishing, or tourism. But shifts in these industries pose new problems and controversy. This guide to climate change in Greenland discusses what a warming climate means for people and for animals, and what new challenges may arise. Whether you’re a museum curator in Greenland or you’re somewhere else in the world, the effects of climate change will become more complex, more personal, and more prevalent. The burden of our future climate may seem daunting, but there are some small, every-day changes we can make to lessen our negative impacts. Check out this BBC article, Ten simple ways to act on climate change, to see how you can make a difference.

Jakobshavn Isbrae is the large outlet glacier that produces a vast quantity of icebergs that fill the Ilulissat Icefjord. Here, icebergs large and small fill the deep fjord and slowly flow past the town of Ilulissat and into Disko Bay.

Torreya Formation Field Trip

Please welcome Carmi, a new guest blogger here at Time Scavengers!

Carmi here –

FPS members are briefed on the geologic history of the site.

In April, I was one of the trip coordinators for the spring meeting of the Florida Paleontological Society. The Florida Paleontological Society is a collection of professionals, amateurs, and every fossil enthusiast you could possibly imagine from all around Florida- and beyond! The society’s mission is to encourage and educate people on Florida’s rich paleontological history.

Usually, trips consist of field collecting (all over the state!), a series of talks given by paleontologists, and a silent auction, with many fossil goodies. In addition to being a member of the society, I also serve as the secretary, which means that I organize membership applications, coordinate trip logistics, and edit the newsletter… among other things.

The first evening of the trip is typically a dinner with all the members who have arrived early for the meeting. It is an optional event, but it acts as a time for folks to catch up and discuss topics of interest with each other. Following dinner, and a good night’s rest, we set off to the quarry to begin the day’s work.

The formation where we looked for fossils is the lower Miocene Torreya Formation (roughly 23 million years old), a limestone deposited when Florida’s sea levels were much higher. This unit is generally thought to be marine, though there is discussion as to the exact nature of the depositional environment – if you are curious to dive into the literature, GeoLex (one of my favorite ways to compile background literature on a geologic unit) has more publications on the Torreya Formation.

Large piece of fossiliferous limestone (the Torreya Formation) with hand for scale – you can see an assortment of snails and clams

After we had our brief geologic and faunal overview, we set down the hill to begin the search. With the constant rain over the days leading up to the trip, the trip leaders were concerned that getting stuck in the clay rich sediments would be an issue – thankfully, the folks from the mine had smoothed out a portion of the road so that access to the collecting site was not too difficult. Small spoil piles were everywhere, full of all kinds of marine fossils, from shark teeth to impressions of different clams and snails.

One fun fact about the site: while many mines in Florida process material for road base (the material that makes up the highways that transport Floridians all over the state), this mine collected and refined clays used in the production of kitty litter!

The descent into the quarry – you can see layering in the distance (the different rock units in the mine)

The evening portion of the meeting took place at the Florida Geological Survey, who graciously accommodated dinner and our evening events. I gave a talk on my current research project – fossil cephalopods from the Cenozoic of Florida. Victor Perez, a graduate student at the Florida Museum of Natural History, was the other invited speaker and spoke on his dissertation research. Finally, the Assistant State Geologist, Harley Means, gave a talk on the history of the survey, and the services that the survey provides to the citizens of Florida!

After the talks, Harley led interested members throughout the survey, highlighting their museum of Florida fauna and amazing library. Inside the library, there were publications on geology of Florida as well as geology from all around the country. Not only does having these publications assist with understanding of similar earth systems elsewhere, but it acts as a way for state surveys to keep in touch and keep aware of developments in geologic mapping and other functions across the country.

Following the tour of the survey, the silent auction began. Items donated by club members were laid out on tables and folks would silently bid on what they found interesting or loudly dissuade others from bidding on these purchases. All the proceeds from the silent auction support student research in paleontology. My strategy is usually to team up with someone on a pile of publications – last year I won a vintage paleontology textbook, and this year I picked up a copy of my beloved Pliocene Mollusca, by Olsson and Harbison (which is another post entirely). After fierce competition, the auction items went home to various members – almost everyone left the auction with something exciting and new.

Of course, the activities were not over for the officers of the society – there was clean-up and then a board meeting the following day. However, trip participants agreed that it was a great experience.

If you are interested in learning more about the Florida Paleontology Society, check out their website:
http://floridapaleosociety.com/

Harley Means, Assistant State Geologist, shows FPS members different minerals mined in the state.

They have an assortment of free educational resources, different publications for sale, and grants for students in Florida who are working on paleontological research.
Until next time!

If you are not in Florida but looking to get involved in local clubs check out myFOSSIL’s Fossil Clubs and Societies – Jen

Fossil Collecting at Caesar’s Creek Spillway

Mike here –

The Caesar Creek Lake Visitor Center

When the students were on spring break a few weeks ago, I decided to take a few days off to go fossil collecting. The first site I went to was the spillway for the reservoir in Caesar Creek State Park. This is a special place for me: it’s the first site we went to collect fossils from during my paleontology course when I was a junior in college. I’ve been going back to this site for about 14 years, but I hadn’t been since 2013, when Jen, Adriane, our friend Wes, and I all went on a long weekend. During this time, Adriane and Jen were helping Alycia Stigall build the Ordovician Atlas. If you are interested in learning more about the organisms found, rock outcrops, and more head to that website!

Jen, Mike, and Adriane out collecting in the spillway in 2013. Wesley is taking the photo. An excellent weekend trip.

This site is exposed Ordovician limestone and shales (click here to learn more about types of rocks), representing warm, shallow marine environments. Three rock formations are exposed: Waynesville, Liberty, and Whitewater. If you are interested in learning more about rock formations, click this link which will go into detail on formations! Because collecting is restricted to the base of the spillway, all of the rocks are mixed together and it is difficult to tell which formation the specimens come from. When collecting from Caesar Creek, one must obtain a pass from the Visitor’s Center—run by the Army Corps of Engineers—and agree to follow their rules. Probably the most frustrating rule is that one can’t use tools to extract specimens, not even another rock! But, regardless of these rules, this location is safe for individuals and families to come collect.

The walls of the spillway. Filled with fossils!

I was excited to see what would be exposed in the spillway. This was the first warm weekend of the year, and it had rained the day before. I figured fossils would have washed out from the wall and would not be picked over yet. Usually after a good rain you get lots of new fossils coming out of the rock due to the increased erosion of the outcrop. So it may be wet and gloomy but good for fossil collecting! It sure paid off because today was one of the best fossil collecting I’ve ever had at Caesar Creek!

Crinoid calyx. Sadly, I could not extract this!
Cephalopod shell cast in the rock.
Brachiopods, bryozoans, and fragments of Isotelus.

This was the best haul I’ve had from Caesar Creek in a long time. I was not able to collect many of the really cool specimens I found. They were either way too big and/or stuck in a rock and I couldn’t use tools to remove them. I’m glad I got to see so many amazing specimens and take some home!

Read more about the Caesar’s Creek Spillway on the Dry Dredgers site by clicking here or the FossilGuy’s site by clicking here.

A huge burrow!
Trace fossil slab!
Fossil assemblage
Crinoid
Slab of trace fossils!

 

Fossil assemblage
Bryozoan and other shellies.
I found this fragment of an Isotelus, which is the largest fragment I’ve ever found. I believe this is the posterior end.
Clockwise from top: Flexicalymene trilobite, cephalopod, and various gastropod species.

Blowing Rocks Nature Preserve

Sarah here-

Image 1: You can see where the tide usually reaches the highest point by how the rocks are much narrower. One of my students is taking notes about the weathering patterns she sees on the rocks.

I recently took my geology students on a field trip to Blowing Rocks Nature Preserve on the eastern coast of Florida near Jupiter Island. This class is my upper level Sedimentary Petrology class made up of mostly geology majors (we mostly study the formation and identification of different types of sedimentary rocks, like sandstone and limestone). I wanted to show you all what we saw!

Image 2: Here is a small sea arch (back of the image) created by wave energy constantly wearing parts of the limestone away. This image was taken at about 10-15 feet away from the rocks in the background. In the forefront, you can see a sea stack-this used to be a sea arch that over time has been worn down to the point that that other half of the rock has eroded completely. In the future, that sea stack will likely collapse from the constant weathering.

The rock that is shown here is the Anastasia Limestone, which was deposited in the late Pleistocene, which spanned about 2.5 million to 12,000 years ago. The ocean levels were much higher than they are currently, when this rock was made. We know this because the limestone that comprises the Anastasia was made underwater. Now, this limestone is exposed all along the eastern shore of Florida.

This limestone is really cool because once it was exposed, it began weathering in unique patterns. First, the energy of the waves is breaking the rocks down bit by bit. This is something we call mechanical or physical weathering. You can see evidence of this mechanical weathering by looking at how the rocks get narrower closer to the bottom-the waves usually only reach that point at high tide, so the rock above it isn’t nearly as affected (image 1). This mechanical weathering can make a few different types of features: sea arches (image 2) and sea stacks (image 2) are the kinds of things we can see here.

Image 3: Here we can see the dissolution pits from water sitting on top of the limestone. Limestone is easily eroded by chemical weathering, so in the future, these pits will continue to get much larger.

The cool geology doesn’t stop here though! Chemical weathering (i.e., breaking down the rock using chemicals-the most common one is water) also affects the rocks strongly here. Limestone is easily eroded away in the presence of acid, so any acidity in the ocean water or from rain above can wear away the rock in interesting patterns. Water splashes up on top of these rocks from regular wave action-that water slowly erodes the rock away, leaving small pits in the rock (image 3). However, what makes this place famous are the large pipes that are created from a mix of the chemical and mechanical weathering processes here. These pipes are quite literally large cylindrical tubes that have been worn out of the rock through hundreds of thousands of years (image 4). Water, when it comes in from waves, rushes up through these tubes and explodes out of the top! Sometimes, these can spray as high as 50 feet-hence the name of the park, Blowing Rocks (video 1)! As we go forward into the future, these pipes will continue to grow larger because they are continuously being worn down by wave energy.

Image 4: Here are some of the pipes created by the intense combination of chemical and mechanical weathering. At high tide, water explodes through these pipes and onto the surface!
Image 5: Here are some trace fossils showing ancient burrows of creatures that lived in this area! Some have interpreted them as mangrove tree roots, but this area was likely too high energy for mangroves to live.

There were some cool fossils on this trip, too! If you look closely, you can see lots of trace fossils from creatures who made burrows into the rock (image 5) and you can also see a lot of clam and snail fossils (mollusks!) Many of these fossils are broken up and the edges have been rounded-this is because of the higher energy waves constantly breaking them down (image 6). My students and I also found a living Portuguese man o’ war (image 7)- this isn’t a jellyfish because it isn’t a single organism, but it’s a closely related colonial organism. The man o’ war has long tentacles that can give humans very painful (but rarely fatal) stings. If you see one on the beach, don’t touch it! They are fairly common on the eastern coasts of south Florida, so be warned! All in all, my students had a great time on this trip, and they learned a lot about how rocks can change due to weathering over time. I hope you enjoyed it, too!

Image 6: Fossil bivalves (clams) are all throughout this area. Most of them are species that lived in fairly shallow and higher energy areas, which match the geologic interpretation of this area. The high energy of this area means that the shells are broken up and the edges have been rounded through constant mechanical wave action wearing down the edges!
Image 7: A Portuguese man o’ war that washed up on the beach! Definitely stay away from these critters-their stings can be pretty painful!

Drumheller Channels

Rose here –

The Columbia National Wildlife Refuge was designated as a National Natural Landmark in 1986. The landscape here is amazing because while it is a desert or shrub-steppe environment, it has been amazingly eroded and carved by water from the giant Ice Age floods. This influx of water has allowed plant and animal life to flourish here, and also allowed humans to farm the land. For more, click here.
A couple of years ago my mom and I took a road trip to eastern Washington state to visit Drumheller Channels in the Columbia National Wildlife Refuge. This is an area containing giant basalt columns, part of the Columbia River Basalt flows, as well as some of the landscape known as the Channeled Scablands, remnants of the catastrophic Ice Age floods (check out the Ice Age Floods Institute for more info).

The Columbia River Basalt Group (CRBG) is a large igneous province in eastern Washington. Large igneous provinces are usually made of very low viscosity (runny) lava which has erupted from fissures in the ground and spread out to cover a large area. The CRBG is a series of lava flows (more than 350!) that cover an area of about 163,700 km2 (63,200 mi2). These lava flows altogether are more than 1.8 km (5,900 ft) thick. These flood basalt eruptions occurred from about 17 million years to about 5 million years ago

This is a view of the channeled scablands landscape, where you can see the tops of different coulees and lava flows in the distance. This land is crazy rugged to drive through!
As basalt cools, it forms a hexagonal pattern on the cooling surface exposed to the air, similar to the pattern you see in mud as it dries. From the side this pattern looks like rows of columns next to each other, and beautiful landscapes made up of several stacked flows of this “columnar basalt” are a common sight as you drive through eastern Washington. The other major component of the eastern Washington landscape, the Channeled Scablands, are the result of flooding that occurred toward the end of the last ice age. They are called Channeled Scablands because the landscape consists of many interconnected channels and coulees and appears very rugged. This landscape has turned out to be one of the most important pieces of evidence in shaping our current understanding of how geological processes have shaped the surface of the Earth.

Here I am hiking over to some of the columns so you can get a measure of scale of these features.
Before J Harlen Bretz started studying this landscape in the 1920s, geologists thought all Earth processes were extremely slow and gradual in making any changes in the landscape. This was a reaction to the suggestion by young earth creationists that the earth was formed rapidly by catastrophic events. The response of geologists to this idea was to immediately dismiss any hypothesis that the landscape had formed rapidly and insist that everything had happened very slowly and gradually. J Harlen Bretz became interested in some interesting erosional features he saw in eastern Washington and began doing intensive fieldwork in the area in 1922. As he continued to map and record his observations of the features he saw there, he became more and more convinced that this landscape had not been formed gradually but had been shaped by giant floods from further east. There are giant ripples here, giant channels and coulees, and giant “potholes” where rock has been plucked up by water rushing past. These features could not be explained by very slow and gradual erosion. Today, geologists understand that while many features are formed slowly, the landscape has also been formed in places by catastrophic events, some of which we can see today in volcanic eruptions, earthquakes, and tsunamis.

Here I am standing next to some of the best-shaped columns, which have been carefully separated from the rest of the basalt flow and stood up on their own so you can see the hexagonal shape.

If you want to know more, here are a couple of good books to start with. Check with your local public library!

More References:

We knew we had made it when we saw the giant basalt columns in the distance. Check out the pictures of me next to them to see how big they really are!
Close-up view of the basalt columns from the side.
Close-up view of the basalt columns from the top.
Standing next to the column wall so you can see how large they really are!
The sun was in my eyes, but this place was so pretty I had to get a picture with it. Thanks to my mom for all the awesome photos from this trip!

Searching for Cambrian Trilobites in Georgia

Cam here-

Figure 1. Asa and Jess searching for trilobite fossils near the edge of the Conasauga River.

On May 7th I lead two fossil hunters to an accessible fossil locality in Murray County, Georgia. The locality is part of the Conasauga Shale Formation. This rock unit runs through Georgia, Alabama, and Tennessee. It is made of shales and mudstones that were deposited during the Cambrian Period (~541-485 million years ago). During this time, Northeast Georgia was under a shallow sea known as the Iapetus Ocean. This ancient sea was located deep in the Southern Hemisphere. Animals living in these waters included sponges, brachiopods, hyoliths, and the famous trilobites.

Figure 2. Aphelaspis brachyphasis trilobite that Jess found.

The most abundant fossils in this portion of the Conasauga Formation are the shed exoskeletons of trilobites. Trilobites are arthropods that were very common animals during the Paleozoic Era (~550-250 million years ago). The trilobites found in Murray County, Georgia died from rapid mudflows that came from a deep marine basin and anoxic (lacked oxygen) environment. Because of this, the trilobite fossils from this site are preserved very well and occur in body clusters with halos of iron oxide surrounding their bodies.

We began to plunge down a hill under a bridge where the outcrops are exposed to the surface. The exposures lie right near the Conasauga River (where the rock unit received its name). It didn’t take long to split the mudstone and come across the remnants of ancient Georgia’s inhabitants. The most common species of trilobite found in the outcroppings is Aphelaspis brachyphasis. They are so common that this locality has been referred to as the Aphelaspis Biozone. There are other species that were found such as agnostids like Glyptagnostus reticulatus which serves as an index fossil for the middle Cambrian and Agnostus inexpectans.

Figure 3. The best specimen of A. brachyphasis that I found!
Figure 4. The Index Fossil for the Middle Cambrian Period Glyptagnostus reticulatus

Agnostids are very small and only occur in rocks from the Cambrian and Ordovician period. Paleontologists have debated whether agnostids are even part of the class Trilobita at all. Agnostids had a head and a tail body parts with two or three thoracic segments. They also have have no eyes which suggest they lived in deeper waters where light did not penetrate the ocean. A lot of the trilobites that we found were disarticulated but some specimens recovered were complete molts. We all came back with well-preserved and numerous specimens.

Memories of a Glacier in the Connecticut River Valley

Adriane here-

An image depicting the extent of ice over North America during the Last Glacial Maximum. The main glacier that covered New England was called the Laurentide Ice Sheet, whereas the smaller glacier that covered parts of western Canada was called the Cordilleran Ice Sheet.

Every Semester, the University of Massachusetts Amherst Department of Geosciences offers the class Introduction to Geology. The course is designed for undergraduate students who need science credits for their degree, but it is also a required course for our geoscience undergraduate majors. The course has a lab that complements and expands on topics that are covered in lecture, such as  plate tectonics, igneous, metamorphic, and sedimentary rocks, river dynamics, topography, and the history of how the Connecticut river valley was formed. The labs are run by four to five teaching assistants, graduate students who are pursuing their master’s or PhD degrees. We take the students on two field trips as part of their labs: the first trip is to look at geologic features in the valley leftover from the glaciers, and the second to look at the major rock formations in the valley.

This post is about the glaciation that ended around 20,000 years ago, and the imprint the ice and ice melt left on this area of western Massachusetts. This time of huge ice sheets that covered northern North America, Europe, and Asia is referred to as the Last Glacial Maximum. In North America, the glaciation is referred to as the Wisconsin Glaciation. The glaciers that covered North America reached their maximum southern extent about 26,000 years ago, after which the ice began to melt and retreat back to the north. At the glacier’s maximum extent, Massachusetts was totally covered by ice. Estimates based on how thick the ice was range from 1 to 2 kilometers  (0.62-1.24 miles)! That’s a ton of ice! Because ice is very heavy, it depressed the Earth’s crust below it. In southern New England, the ice is estimated to have depressed the Earth’s crust down by about 50 meters (~165 feet; Oakley and Boothroyd, 2012). Once the ice melted, the crust of the Earth began to pop back up. This phenomenon is called isostatic rebound. Satellites that measure the rate of isostatic rebound indicate that parts of Greenland and Canada, where the ice was thickest, are still popping back up today.

A shematic map of New England depicting the location and size of Glacial Lake Hitchcock. The maximum extent of the Laurentide Ice Sheet is depicted by the solid line towards the bottom of the image (Rittenour et al., 2000).

Back at a more local scale, there are several features around UMass Amherst that we, the graduate students that teach the Introduction to Geology labs, can identify that were created as a direct result of the glaciers in this area. I’m going to take you on our glacial field trip virtually, so that you, too, can get a first-hand look at the types of geologic features the glaciers left behind! First, a fun aside: There are several large boulders all over campus that, at first glance, look like they were placed in specific locations for an aesthetic affect. Upon closer inspection, the boulders are made from a certain rock type that occurs in our valley. Glaciers, and ice, act as bulldozers, and have no problem picking up and carrying huge chunks of rocks. These boulders, then, were picked up from the nearby hills and deposited all over the valley, with some ending up on our campus! These boulders aren’t part of our field trip, but are neat nonetheless.

The varves at UMass Amherst that are the sediments that made up the floor of Lake Hitchcock. The different bands are clearly visible, but the dark and light colored bands aren’t obvious when the soil is wet.

The first stop on our field trip is right on campus, behind our football stadium. Here, there is a small creek with about 5 feet of the upper part of the soil profile exposed. But there’s something special about the soil here: it is unlike anything found in other places of the world: varves! Varves are alternating bands of dark and light-colored clay layers that made up the bottom of a lake that used to cover the valley. The lake was created once the glaciers began to melt, leaving more parts of Massachusetts exposed. The meltwater from the glaciers flowed via river into the Connecticut River Valley, and became dammed here. This created Glacial Lake Hitchcock. The varves are remnants of the sediment that collected on the bottom of this lake. Varves are awesome because they record climate changes on a seasonal basis! The dark bands contain finer clay particles, and are deposited during the winter months when there is less sediment being brought into the lake by the river (during the winter months, there is less glacial melt, and thus less water flowing in the rivers). Lighter varve bands are usually made of coarser (or larger) grains and are deposited during the spring and summer months when glacial melting increases, bringing more water and thus sediments into the lake. By counting the pairs of dark and light varves, scientists can estimate how old Glacial Lake Hitchcock was. Varves from the lake were counted by scientists at UMass Amherst, and they found that the lake was around for at least 4,000 years, from 17,5000 to 13,5000 year ago (Rittenour et al., 2000)!

A kettle pond near UMass Amherst.

After checking out the varves, our second stop is a kettle hole a few miles from campus. A kettle hole is a depression in the Earth formed from a chunk of ice that broke off from the retreating glacier. The ice chunks become buried by glacial outwash, or the mix of water and sediment that spreads across the land as the glacier melts. Thus, the ice chunk is completely buried by sediments. After some time, the chunk also melts, which then creates the kettle hole. These features are prominent throughout New England, and are usually small in size.

The Sunderland Delta (left panel), with topset and foreset beds highlighted for clarity (right panel).

The third stop on our glacial field trip is to the Sunderland Delta. A delta is a place where a river meets a larger body of water, like a large lake, ocean, or sea. Some rivers flow fast, and some flow slower. In general, the faster a river flows, the more sediment it can move and carry. I mentioned earlier that the glacier began to melt back, and that melt water was transported by a river into Glacial Lake Hitchcock. The river was quite large, and had the ability to move sand-sized sediment. But where the river met the calm waters of the lake, it lost its velocity, and thus its ability to carry sediment. The sediment was then ‘dropped’ at the mouth of the river where it emptied into Glacial Lake Hitchcock. This dropped sediment formed a delta, or an area where fine-grained sand was deposited. This sand accumulated over thousands of years. Today, these sand deposits that make up the delta are mined by humans for use in concrete and manufacturing. There are several open mining pits around the university, but one in particular preserves the features of the delta, namely topset and foreset beds of sand. When the river gets close to the larger body of water, it begins to slow down. The loss of velocity leads to the river dropping some of its sediment it is transporting. This sediment is laid down in thin sheets that lie flat. These sediments form topset beds. Where the river meets the body of water, it is slowed even more, and the rest of the sediment it carries is dropped. These particles form a slope down into the lake, and make up the sloping foreset beds.

Once the students understand how the Sunderland Delta was formed, we then move downhill to our fourth stop: a trout hatchery right down the road. This, by far, is the coolest stop, as it contains a unique geologic feature: a natural spring! At our first stop, you saw that the base of Lake Hitchcock was composed of very fine sediment called clay and silt. Clay and silt grains are flat, and when they are compressed over time, they don’t allow water to pass through very quickly. In the introduction paragraphs of this post, I also explained how the Earth’s crust underneath New England, including Massachusetts, popped back up, or rebounded, after the overlying weight of the glaciers was gone. When the land began to rebound, that caused the clay layers of the lake to crack. When this happened, the groundwater that was stored deep in the sediment under the clay was able to come to the surface. Here, at the trout hatchery, is one of the places the groundwater is able to come to the surface via cracks and conduits in the thick clay layers! It can be seen bubbling to the surface continually throughout the year. The video below shows the spring in action:

A view of one of the trout ‘tanks’, where the spring water feeds into the top tank and trickles down to the two other rows of tanks below.

The water stays a constant temperature year round because it originates from so deep within the sediment. The constant temperature and clarity of the water is great for raising trout, because the water rarely, if ever, freezes during the winter and is never too hot during summer months! The trout that are raised at the hatchery are released into local streams and rivers so that fishers do not over-fish the local populations. This stop is one of my favorites, as it is an excellent example of how geology and biology go hand-in-hand, and how the geologic processes of the past are relevant and useful today.

Our fifth and final stop is just down the road from the trout hatchery. The feature here is not as impressive or obvious after the large delta feature and the natural spring, but it records an important phenomenon related to the retreat of the glaciers nonetheless. On the side of the road is a small hill that most local folks pass by probably everyday. This hill is covered in trees and vegetation, and one might totally overlook it quite easily. But if you stop and dig down 4-5 inches through the roots and topsoil, you’ll hit sand!  This small hill is, in fact, a sand dune that was formed from winds towards the end of the Last Glacial Maximum.

A hole I dug in the side of the glacial dune. Notice the darker sediment (made of rotting leaves and roots) towards the top of the hole. The base of the hole is lighter in color, as that is the sand!

When the glacier that covered Massachusetts began to melt back, the Earth was beginning to warm up. The area to the south of Massachusetts was becoming warmer, but on top of the glacier to the north, the air temperature was still very cold. This difference in air temperature, or temperature gradient, created strong winds that blew from the warmer regions towards the colder regions. This phenomenon happens today at the beach: during the day, the wind blows towards the ocean from the hot land; but at night, the wind direction changes as the land cools down until it is cooler than the ocean water. The beach is also characterized by sand dunes,which are the products of these strong winds depositing small sand grains behind the beach. Just like at the beach, the strong winds moving towards the glacier picked up small sand grains and deposited in the valley near UMass, where they are still visible today!

The features that we show our undergraduate students and that are explained here are just a few features in our valley that are leftover from the massive glaciers that once covered the land. All around New England, there is evidence of the heavy ice that was once here not too long ago: exposed rock where the glaciers scraped away soil; glacial striations, or scratches, in the exposed rocks from the glaciers moving over them; and potholes in the bedrock near the rivers, where melted water mixed with larger pebbles and boulders under the ice to carve out rounded holes in the rocks. If you’re ever in New England, keep your eyes peeled for evidence of the glaciers; it’s literally everywhere!

Bedrock, or very old rocks that underlie the soil of western Massachusetts, that were scraped clean by the glaciers in Shelburne Falls.

 

Citations

Oakley, B. A., and Boothroyd, J. C., 2012. Reconstructed topography of Southern New England prior to isostatic rebound with implications of total isostatic depression and relative sea level. Quaternary Research 79, 110-118.

Rittenour, T. M., Brigham-Grette, J., and Mann, M., 2000. El-Nino Like Teleconnections in New England during the Late Pleistocene. Science 288, 1039-1042.

Exploring St. Augustine, Florida

Jen here –

Outside of the Castillo de San Marcos along the beach. It’s quite an impressive and old structure!
I was recently one of fifteen participants in a workshop. Most participants in this workshop are graduate students or recent graduates studying paleontology or biology. The workshop is a month long with very few days off. We had one two day weekend and decided it would be fun to be tourists and go to St. Augustine! St. Augustine is a very old city that is on the eastern coast of Florida and is home to Castillo de San Marcos National Monument.

a close up of my hand next to the coquina that was molded into a pillar. Abby next to that same pillar for a better scale! Most of the rock used for the buildings was coquina!
We were incredibly excited to realize that much of the local stone work was sourced from local rock. This rock is called coquina. Coquina is a sedimentary rock that is made up of shell fragments! The coquina is from the Anastasia Formation that was deposited in the Late Pleistocene (around 2.5 to 0.012 million years ago). We spent a lot of time with our faces pressed into walls looking at what shelly creatures were preserved in the wall. The National Park Service has a nice write up explaining how creating the fort out of coquina was incredibly beneficial, click here to read more. Essentially, the rock did not break when the opposing forces began firing weapons and at the fort. Instead, the rock absorbed the shock and compressed when hit with cannon fire!

A group of scientists examining one of the coquina walls. This one was absolutely filled with nice sized oysters.
We spent time exploring the fort, which had an amazing amount of rooms with some extraordinary details preserved. When I say the entire fort was made of coquina, I mean the entire thing. It was one of the most incredible things I have ever seen! There were rooms with barrel vaulted ceilings, tall arch like ceilings, some with carvings in the walls, and much more.

Underneath the boardwalk at the St. Augustine beach. These pillars were filled with organisms that stick on other things for most of their lives.
After visiting the fort we spent time around the city exploring and being tourists. Then we decided to venture out to the beach. Remember, paleontologists study ancient life. This means many of us have training in biological sciences and get really excited about animal life! We got to the beach and some people hopped right into the water while others sat on the beach and read or took a walk along the beach. May and I decided to walk along the beach and we eventually came to these large pillars supporting a boardwalk.

A close up of some of the barnacles with my finger for scale! Some of them were quite large!
These pillars were completely covered in sea creatures! Mostly oysters, other small clams, snails, and barnacles! Most notably were the large barnacles that were a beautiful pink/purple color! Barnacles are related to crabs and lobsters but look so very different. It is absolutely astounding that these creatures can be cemented to the pillars and live for periods during high tide. Not all of the animals were still alive that were on the pillars, especially those that were quite high up.

This is a great example of how we can better explore the world around us through the lens of different sciences! Geology that contain biological remains and lots of living organisms on the beach!

Grand Canyon Trip

Rose here –

Standing on a rock at Ooh Aah Point, about a mile down the South Kaibab Rim Trail.
A year ago I got the chance to visit the Grand Canyon National Park. I had been there once as a toddler, but of course I didn’t remember it, so I was very excited to have the opportunity to go again now, especially since I’ve been studying geology for a few years. The Grand Canyon is like Disneyland for geologists. There are SO many cool geologic processes and so much geologic time represented there (click here for a fun read on the geology).

Hiking down the South Kaibab Rim Trail and looking back up at the South Rim.
We were staying in Flagstaff, AZ for a conference, but my colleague and I had a free day before it started and since the Grand Canyon is only an hour and a half away we decided to just hop in the car and go. We started off early in the morning so we could try and beat the heat. When we arrived we headed straight to the rim.
It was one of the most exciting moments of my life. I had seen pictures of the canyon, but nothing prepared me for what it was actually like to stand there in person. We walked up to the rim with our eyes on the ground so we would see it all at once. When we got close enough we looked up and were utterly speechless for at least a minute. It was so worth it. The Grand Canyon is so big. Like, SO BIG. Apart from all the cool geology, it is a really amazing view.

Sitting near the edge by the Geology Museum (I was further back than it looks!).
One of the coolest things about the Grand Canyon (besides the size) is how you can really see textbook examples of geologic concepts displayed in a way that anyone can see. For example, the Great Unconformity is a famous example of an unconformity – a place where rocks were deposited or uplifted and then some time passed and/or erosion occurred before more rocks were deposited. The Great Unconformity is the place where the beautiful sedimentary rock layers that make up most of the Grand Canyon are deposited on top of older metamorphic and igneous rocks. The distinct sedimentary rocks layers we see exposed in the canyon help geologists understand what the environment was like at different times in the past. After all these rocks were deposited, the canyon itself was carved out by the Colorado River starting at least 6 million years ago (click here for more information), resulting in the Grand Canyon we see today.

A note from the editor (Jen): I wholeheartedly agree with this description, the view is beyond breathtaking. It takes a while to soak in the awe inspiring beauty. Time is so often taken for granted but when you can see so much time in the rocks, it gives you a new perspective.

A view of the Grand Canyon from near the visitor’s center, looking north from the South Rim.
Me standing at the South Rim, with Bright Angel canyon behind me.