What do a volcano, a lake and shiny beetles have to do with each other? Nothing? Think again!

Linda and Michaela here – when we were undergraduate students, we had to do a four week internship as part of our degree. Learning a new skill beyond the university’s coursework is more fun when you get to get your hands dirty and spend time outdoors, preferably lots of it.  A perfect way to do so is to do an internship at a paleontological excavation. Luckily, we both got accepted at the same place and thus, spent a month excavating fossils at the eocene Eckfelder Maar in the western German Eifel mountain range (Fig 1). 

Fig 1: Location of the Eckfelder Maar in the Western German EIfel mountain range. Illustration by Michaela Falkenroth.

The Eocene is a geological epoch ranging from 56 to about 33 million years ago. Back then, a greenhouse effect had heated up central Europe and the world. Tapir relatives and tiny horses roamed (sub-)tropical forests, crocodiles stalked marsupials at lakeshores, small primates climbed palm trees. These are not the organisms and ecosystems associated with cold and rainy Germany today! But this is what it looked like, when the Eckfelder Maar came to life with a bang. An event that should change the rainforest and the lives of German paleontologists alike.

A maar is a volcano, although at first glance, it doesn’t look like one – there is no lava, no ash, not even a mountain. It resembles a volcano so little that early descriptions deemed maars the result of ‘cold eruptions’, which is wrong but relatable.

Maars usually present themselves as perfectly circular. The water-filled craters are the result of the sudden and violent evaporation of cold groundwater that came in contact with hot magma. The explosion tears a pointy, steep-sided hole into the landscape and is usually a singular event, at least in that exact location. At first, the crater is belted by a ring of debris that was thrown out by the force of the explosion. This wall, however, becomes eroded by wind and rain and, as the crater slowly fills up with rain and groundwater, no direct sign of the volcanic activity is left (Fig 2). An eruption like this is called a phreatomagmatic eruption.

Fig 2: The formation of a maar lake in 6 simple steps, all you need is groundwater and piping hot, rising magma. Illustration by Michaela Falkenroth.

The Eifel area, where the Eckfelder Maar is located, is the international type locality that coined the term ‘maar’. Over 75 of these round craters are speckled throughout the landscape and often referred to as the “eyes of the Eifel” because of the round shape and blue colour of the lakes. Over time a maar lake is destined to fill completely with sediment and eventually dry up. The Eckfelder Maar is 44.3 Million years old and hence much older than the others in this area, which formed between 500.000 and 11.000 years ago. Even of the younger maars only 9 still host a lake today, the Eckfelder Maar lake has long dried up. Initially, the eruption blasted a 1000 m wide and up to 210 m deep crater into the surrounding rocks. The bottom of the crater was quickly filled with a layer of debris. After the dust had settled and the lake had formed, it became quiet. For 250,000 years layer upon layer of clay, each less than a millimetre thick, accumulated at the lake floor and slowly but surely filled it up.

Fig 3: The excavation location is covered with a plastic tent to protect the interns (but more importantly the fossils!) from the summer heat.

For the majority of its existence the lake was strictly divided into two layers: a lower, mineral-rich and oxygen-depleted part and an oxygen-rich upper part. The density difference between the two water bodies inhibited mixing and thus kept the lake floor a life-hostile environment. What is bad for sediment-dwelling organisms is good for paleontologists – the oxygen poor lake bottom served as a preservation chamber for all kinds of organisms.

Due to the steep crater being located in a (sub-)tropical, species rich forest, many organisms ended up on the bottom of the lake. In addition to (semi-)aquatic creatures such as crocodiles, turtles and fish that spent at least part of their lives in the lake, large amounts of plant fragments fell into the lake and sank to the lake floor. Leaves and leaf fragments are among the most common finds in this lagerstätte, but pollen, pieces of bark, twigs, fruits and the occasional flower have also been discovered. Especially flowers are very valuable finds, since – in cases of exceptional preservation – they can allow the extraction of pollen. In this case the scientists have proof that a certain species of plant produces a certain type of pollen and can thus confidently identify pollen found elsewhere. Plant fragments are found so commonly, that only rare and exceptionally well preserved or otherwise special finds are being collected, such as fruits, flowers, and leaves with damages suspected to be caused by insect herbivory. Other less valuable finds are given to visitors who come by to learn about the excavation. 

Fig 4: During the excavation we usually sat on wooden blocks while splitting slabs of the sediment hoping to find a shiny jewel beetle or a winged ant inside.

In addition to plant material, insect fossils are recovered in large numbers. Honey bees, ants, termites, flies, wasps, grasshoppers, lice, dragonflies and others are found at the Eckfelder Maar. Among these, beetles are the most common find, as their comparatively high weight and drop-shaped bodies sink quickly. Lighter built creatures, like a dragonfly, tend to float on the surface of the lake and decompose or end up as someone’s dinner. Sometimes the attentive student spots a tiny, metallic blue or green shimmer among the sediment. This is the moment when you know you have encountered one of the most spectacular insect finds. The gemstone-like jewel beetles (family Buprestidae) are – even as fossils – colourful and shiny. The jewel beetles’ colouration is not caused by pigments, but by the microstructure of their wings, which can be preserved much easier than pigments, so they still look as fabulous as they did 44 million years ago.

Plant and invertebrate finds are usually very small, so a hand lens is a crucial tool, just as the dull knife we used to split the soft, wet sediment (Fig 4). If a slab of sediment contained a small fossil, we removed as much of the surrounding material as possible without damaging the find, then placed it in a plastic container and submerged the fossil in glycerin to keep it moist (Fig 5). Since the water content of the sediment is very high, a sudden change of conditions such as drying out of the fossil would lead to irreversible damages.

Fig 5: Tray with small finds of a single day. These include beetles, a snail, unidentified unarticulated bones, leaves and a coprolite.

Vertebrate fossils tend to be larger, but are much rarer. Just as today there are fewer vertebrates than ants, flies or beetles around in most ecosystems. Often, you only find a single bone or a fish scale. Every once in a while, the steep crater walls caused sediment to slide into the lake in one big gush, called a turbiditic current, destroying everything in its path on the bottom of the lake. These turbidites often contain fragmented skeletons and single bones, but are also useful features as they can function as marker horizons and thus help with the stratigraphical indexing of fossils. Finds are labelled for example ‘15’ meaning this fossil was collected from a layer 15 cm below marker horizon number 4. This is important because it later on allows to understand the fossil assemblages in the correct sequence. The exact location of all vertebrate finds is also documented using a theodolite, a device that measures the angles between points. If you place the theodolite on a fixed position, then measure the angles from there to reference points and then to a special marker held on top of the fossil (Fig 6), the exact location can be calculated and represented 3-dimensionally later. If you do find a complete skeleton unaffected by turbiditic currents, they are often in pristine condition, as due to the anoxic, inhospitable environment at the bottom of the paleo-lake no bioturbation or scavenging has affected them.

Fig 6: Measuring the location of a vertebrate fossil in 3D. A theodolite measures the angle to the reflector placed on top of the fossil, as seen in the image. Linda adjusts the angle of the reflector so it points directly at the theodolite (not within the frame) while Michaela ensures the reflector remains in the correct position.

The Eckfelder Maar is known for its well preserved horses and horse relatives (family Equidae). Several complete skeletons of different early equid species have been discovered there. The most spectacular specimen discovered there so far was a pregnant mare and both the fetus and parts of the placenta have been preserved and studied extensively. These early horse relatives had more toes than modern horses and were only the size of a dog. 

The largest complete vertebrate fossil found during our internship was a large basal ray-finned fish (family Amiidae). Since it was too large to be handled in the field, it was first coated in glue, covered in plastic foil and plaster, then lifted together with a large chunk of the surrounding rock to be carefully excavated later on in the lab (Fig 7). 

Fig 7: Larger finds such as this complete fish require more elaborate excavation techniques and are thus covered in plaster and lifted with the entire block of sediment to be slowly excavated in the lab by a geological preparator.

One of the smaller, but more exciting finds was a complete skeleton of a young bird (Fig 8). Fossil birds are rare in these kinds of deposits, since birds don’t tend to slip and fall into a lake, like it could happen to a clumsy horse on a slippery lakeshore. The specimen appeared to be a nestling, since the preserved feathers looked very fluffy. We hypothesized that it must have fallen out of its nest directly into the lake. 

Fig 8: Unidentified bird (beak pointing downwards) found during the internship. Even without any additional treatment, details such as the shape of the body, feathers, the eyes and other soft tissues can be identified easily just seconds after being exposed, due to the excellent preservation at this lagerstätte.

It’s fossils like these, preserved under exceptional circumstances, that allow us to reconstruct and understand ecosystems that are long gone. The Eckfelder Maar is a little slice of Eocene, frozen in time, waiting to be uncovered.

Valentia Island Tetrapod Trackway: one of the earliest traces of vertebrates on land

Linda here –

Due to the global pandemic, much of the field work in almost all geoscience disciplines has come to a halt. While this means we cannot travel to discover new sites, collect new samples or do field experiments, this leaves us lots of time to commemorate all the exciting field experiences we’ve had in recent years. 

Here I would like to introduce you to a small, but very important outcrop I visited a few years ago: the tetrapod trackway on Valentia Island (Co. Kerry, Ireland). 

Valentia Island is a fairly small island in the eastern North Atlantic, just off the western coast of Ireland, it is in fact one of the westernmost points of the entire country. The outcrop itself is located on the northern coast of Valentia Island, and when I say on the coast, I don’t mean near the coast, I mean the literal edge of the island, partially under water.

Panorama view of the coast, the photo was taken while standing on top of the outcrop, looking towards the east, the island in the background is Beginish Island.

 

The outcrop consists of Middle Devonian sandstones and slate called the Valentia Slate Formation. Life in the Devonian was very different from today, the first ammonites had just appeared, trilobites were common. Fish diversity was at an all time high, placoderms roamed the oceans.

Two parallel rows of small, irregular shaped impressions are among the oldest evidence for vertebrates on land that we currently know of, these fossil tracks are estimated to be approximately 385 million years old!

On land, the first plants developed proper roots, leaves and seeds, by the end of the Devonian forests were widespread. And the tetrapods made their first steps on land, too. 

A few of these very early steps have been recorded by the muddy sediments that later became the Valentia Slate Formation. 

Unfortunately these imprints are quite rough, the shapes are irregular and no digits can be identified. Still, researchers have been able to determine that this creature must have been able to support its own weight on its four legs, because no body or tail drag marks are visible, it was clearly walking, not crawling or swimming. It’s approximate body length was 0.5-1m (20-40 inch) and its hands were probably smaller than its feet (Stössel et al. 2016). 

Shoe for scale.

A reconstruction of the tetrapod that has left these tracks for us to find is depicted on a sign on a path leading to this publicly accessible outcrop. 

The outcrop is an Irish National Heritage Area, though it is threatened by erosion. When I visited, the tracks were actually filled with sea water and every once in a while a wave would wash over the outcrop. Fortunately, recently two more sites within the same formation have been discovered that contain very similar tracks and thus will aid us in our understanding of these very early tetrapods.

Reference: 

Stössel, I., Williams, E.A., and Higgs K. (2016) Ichnology and depositional environment of the Middle Devonian Valentia Island tetrapod trackways, south-west Ireland. Palaeogeogr. Palaeoclimatol. Palaeoecol., 462, pp. 16-40

A palaeontologist’s guide to modern marine ecology

Kristina here – 

Interdisciplinary experiences are a great way to learn new things and broaden your perspectives as a scientist. I’m a palaeontologist who studies the effects of climate change on predation and biotic interactions in marine invertebrates, but over the course of my research career, I’ve spent more time working with modern animals and ecosystems than I have with fossil ones. It may sound strange, but I believe it’s made me a better palaeontologist. I’ve learned a lot from working with modern ecologists, and I’d highly recommend it to any aspiring or established palaeontologists.

Why work with modern systems?

Predation in action – a giant seastar eating a giant clam (Bamfield Inlet, B.C.)

Observing animals helps you understand the mechanisms of what you might observe in the fossil record. You also really gain an appreciation for the things that don’t fossilize, like animal behaviour (I’ve been outsmarted by crabs, and maybe a snail or two, on more than one occasion). I study predation and biotic interactions, which are not possible to observe in real time in the fossil record because those animals have been dead for a very long time. Instead, we as palaeontologists must rely on other clues, like predation scars, as evidence that organisms interacted. But interpreting how or why organisms interacted in the fossil record can still be tricky. For example, crab predation on molluscs has been common since the Mesozoic, but as crabs crush their prey into oblivion to eat, the only evidence of crab predation we can observe in the fossil record are failed attacks where the prey survived and a scar formed on its shell. A big question in palaeontology has therefore been: do these failed attacks we observe in the fossil record actually tell us anything about predation? Conducting live experiments and modern field work where we observe how crabs prey upon animals like snails helps us understand what we are seeing in the fossil record and why. For example, one thing we’ve learned is that the number of crab scars on snails reflects the abundance of crabs at a locality rather than changes in how successful crabs are at killing snails between sites (Molinaro et al. 2014; Stafford et al. 2015).

Collecting snails for lab experiments (Bodega Marine Lab)

We can use modern experiments as baselines that can “calibrate” our interpretations of patterns in the fossil record. Part of my Ph.D. research involved conducting a long-term ocean acidification experiment on two species of snails at Bodega Marine Laboratory. I wanted to know how ocean acidification and predation affected snail shell growth and strength, and what this might mean for both past and future predator-prey interactions between crabs and snails. I found that some shell materials are more vulnerable to ocean acidification because they grow less and become weaker, and are therefore more susceptible to predation (Barclay et al. 2019). Not only does this mean that some mollusc species might become more vulnerable to predation with continued climate change, but it means that we can use clues like this to help identify periods of ocean acidification in the fossil record, and then watch how it plays out in ecosystems over time.

Metrhom Robo-titrator (determines water alkalinity) and Instron (measured the force required to crush my shells – very stressful after 6 months of growing them) (Bodega Marine Lab)
My study species – the red rock crab (Cancer productus) and black turban snail (Tegula funebralis) – Notice the crab predation scar on the top right snail)

Comparing modern and fossil systems is important for conservation efforts. There is an entire field of palaeontology called conservation palaeobiology where we try to use deep time perspectives to answer questions related to modern climate change and conservation issues. For another part of my Ph.D. research, I compared crab predation on snails in the same modern and fossil systems to try and understand what has happened to these systems over time. Some of my results have been a little scary, and suggest that human activity has already had major consequences on crab populations in places like southern California.

And, if I’m being perfectly honest, it’s just plain fun to work in modern marine biology! I’ve been lucky enough to travel to many beautiful field sites along the west coast of Canada and the U.S. to conduct research on rocky-intertidal invertebrates. My favourite field sites I’ve been to are on Vancouver Island (near Bamfield, B.C.) and the north-central Oregon coast. I’ve also had the great privilege to conduct research and take classes at three marine labs: Bamfield Marine Sciences Centre on the west side of Vancouver Island, Friday Harbor Laboratories on San Juan Island, Washington, and Bodega Marine Laboratory in northern California. If you ever have the opportunity to conduct research or take classes at any of these places, I’d highly recommend it, and would happily provide some connections and potential funding sources. There’s nothing like some salty sea air, observing live critters in their natural habitats, and the occasional curious seal or whale sighting to inspire your curiosity and love of the natural world. 

Bamfield Sunset at the Bamfield Marine Sciences Centre.

What I’ve learned?

Shelfie with a red abalone (Bodega Marine Lab)

Working with modern ecologists has been such a rewarding experience. I’ve learned so much about animal behaviour, chemistry, and physiology (fun fact: crabs are ridiculously stubborn and will spend hours trying to break into a snail before admitting defeat and throwing the snail across the tank in a tantrum). I’ve also learned a lot of about the world of larvae and plankton (I even got to participate in an experiment with larvae of an endangered species, the white abalone), and seaweeds (which is not something that we often get to see in the fossil record). I also learned a lot of lab, statistical, and experimental design techniques, such as how to analyse water samples for alkalinity and pH. The level of detail and complexity available in live systems can really help you tease apart how such things might influence your interpretations of the fossil record. One of the most interesting things I learned from a lab mate at Bodega Marine Lab was just how much night/day variation there is in tidepool water chemistry, with pH swings of several orders of magnitude in a 24 hour cycle (Jellison et al. 2016)! I also learned that some snails can tow several hundred times their body weight, possibly placing them as one of the strongest animals on earth!

Tidepools at Yaquina Head, Oregon

What can geoscientists offer?

Even though I’ve learned so many new things about modern marine ecology, there are several unique perspectives I’ve been able to offer to my modern marine colleagues as a geoscientist. First, as palaeontologists, our perspective of time and evolution is often completely different than an ecologist’s. One isn’t inherently better or worse, but a geological understanding of time can help you ask big picture questions and allow you to fit modern research into a larger context. For example, a long-term study in the modern is usually on the order of years or decades, whereas palaeontological studies span thousands to millions of years. We understand how things like storms, taphonomy, and time averaging might influence our results in a broader way. We also understand just how fleeting today’s conditions are. One other unique perspective is our geological field training – we think in three dimensions, especially when we are out in the field looking at outcrops. When I see a mussel bed, I’m not just thinking about the biology of individual mussels, I’m thinking about how it accumulated, how water conditions change across it, and what might cause it to change over time. I’m not saying ecologists don’t do that, because they do, but it’s just second nature to geoscientists. 

The important thing here is that one field isn’t better than the other, but rather, we all have different strengths or emphases we’ve learned and by combining both modern and fossil perspectives, you can ask really interesting, important questions!

References

Barclay, K., B. Gaylord, B. Jellison, P. Shukla, E. Sanford, and L. Leighton. 2019: Variation in the effects of ocean acidification on shell growth and strength in two intertidal gastropods. Marine Ecology Progress Series 626:109–121.

Jellison, B. M., A. T. Ninokawa, T. M. Hill, E. Sanford, and B. Gaylord. 2016: Ocean acidification alters the response of intertidal snails to a key sea star predator. Proceedings of the Royal Society B 283:20160890.

Molinaro, D. J., E. S. Stafford, B. M. J. Collins, K. M. Barclay, C. L. Tyler, and L. R. Leighton. 2014: Peeling out predation intensity in the fossil record: A test of repair scar frequency as a suitable proxy for predation pressure along a modern predation gradient. Palaeogeography, Palaeoclimatology, Palaeoecology 412:141–147.

Stafford, E. S., C. L. Tyler, and L. R. Leighton. 2015: Gastropod shell repair tracks predator abundance. Marine Ecology 36:1176–1184.

Devonian of New York: Schoharie and the Helderberg Group

Adriane here–

When I was a PhD candidate at UMass Amherst, I was the teaching assistant for our geology department’s Historical Geology class. Every spring, weather permitting, we would take our students on a weekend field trip to upstate New York, to visit rock formations and outcrops that were of Ordovician to Devonian (~450 to 385 million years ago) age. These outcrops and rocks contain abundant fossils, but there was one outcrop in particular that I always found to be the most fascinating: the Middle Devonian rocks exposed near Schoharie, New York.

Now that I am a postdoc at Binghamton University, I’m only about 1.5 hours away from this incredibly cool outcrop! A few weekends ago, my husband and I decided to take a short road trip to go fossil collecting here, as it was the perfect activity to do during a pandemic (limited to no interactions with other people, ample outside time, but also close enough to home). Unfortunately the day was incredibly hot, and we were only able to stay for about half an hour before we felt as if we were roasting. Regardless, we brought home so cool finds, namely a slab of invertebrates, some brachipods, a horn coral, and a sponge!

The outcrop exposed near Schoharie is well-known to local fossil and mineral clubs and fossil enthusiasts. The location is secluded and quiet, there is a long and wide shoulder for parking, and the outcrop itself is set off the road a bit, which is great for students and kids! The outcrop itself is located on Rickard Hill Road, just east of the town of Schoharie.

Google Map of Schoharie, New York, with the location of the outcrop denoted by the yellow star.

The rocks here are part of the Helderberg Group, which are composed of limestones that were deposited in a shallow sea during the Middle Devonian. There are three rock formations that are present: the Coeymans Limestone, Kalkberg Limestone, and Becraft Limestone. The Coeymans Limestone is the oldest formation here. It is a medium to coarse grained limestone which is massively bedded, meaning the rock layers, or beds, themselves are quite thick. Fossils are present in this formation, however, because the formation is massively bedded, the fossils are hard to get out of the rock and are less easily eroded.

An image of the Rickard Hill Road outcrop. The Kalkberg Formation is the rock that makes up the slope of the outcrop which you can walk on and collect fossils. On the right side of the image, the small cliffs are mainly composed of the Becraft Limestone. Image from http://bingweb.binghamton.edu/~kwilson/Devonian/DevSites/Schoharie/Schoharie.htm

The Kalkberg Formation lies above the Coeymans, and is described as a thin to medium bedded limestone. This means the individual rock layers within the formation are smaller and not as thick as those observed in the Coeymans Limestone. This formation also contains shale layers, a very fine-grained rock. This formation was likely deposited in a deeper-water setting than the Coeymans Limestone. Several different species and types of fossils are found in the Kalkberg, including animals such as corals, conularia, bryozoa, crinoides, brachiopods, trilobites (which are very rare), bivalves, gastropods, and even straight-shelled cephalopods. When you get out of you car at the outcrop, the Kalkberg Formation is what you are walking on!

 

My pentamerid brachiopod from the Becraft Formation. The lines visible on the surface are from glaciers that flowed across this brachiopod, which was cemented into the rock!

The Becraft Formation is the youngest of the three formations exposed at the Schoharie outcrop, and sits atop the Kalkberg Limestone. Similar to the Coeymans Limestone, the Becraft is a more massively bedded, coarse-grained limestone that was likely deposited in shallower waters than the Kalkberg Limestone. Because this formation is more resistant to weathering, it forms the small cliffs at the outcrop location. This formation contains fossils, but again, because it is more massively bedded, the fossils are not always as easily eroded out from the rocks. Other collectors have found fossils such as crinoids, brachiopods, gastropods, and bivalves.

One of the things I absolutely love about the Becraft Formation is that it contains glacial striations at the top of the cliffs! Glacial striations are grooves left in rocks when the glaciers covered much of northern North American about 15,000–20,000 years ago. Striations are commonly found on metamorphic, sedimentary,and igneous rocks, and help geoscientists know which way the ice flowed. But that’s another fun story for later. One of my all-time favorite fossil finds came from the top of the Becraft Formation: a pentamerid brachiopod that was carefully sliced in half by glaciers, that contains glacial striations! The brachiopod was likely preserved as a whole specimen with two valves, much like a clam has two parts to its shell. The glaciers eroded just enough of the formation and brachiopod to cut it perfectly in half. Incredible!

A slab of limestone containing quite a few fossils, including brachiopods, bryozoa, and bivalves!

If you are in the area, I highly recommend stopping at the Rickards Hill Road outcrop and visiting the Helderberg Group. Collecting here is fun for all ages, is open to the public, and fossils are almost guaranteed 🙂

Additional Resources

Fossil digs in Upstate New York: 5 Good Places to Search
Lower Devonian Fossils near Schoharie, NY
USGS Helderberg Group 

 

 

 

 

 

Geology of the Mount Rogers Formation and Virginia Creeper Trail

Mckenna here- This post will show you the geology of the Mount Rogers Formation and Virginia Creeper Trail on a recent field trip I took to Virginia!

Day 1

Image 1. Our professor leading us to a geology lookout point on the way to Abingdon to see an outcrop (visible rock formation).

On October 10th of 2019, my Mineralogy, Petrology, and Geochemistry class went on a 4 day field trip to Abingdon, Virginia. Imagine this: it’s October. You love fall but you’ve lived in Florida your whole life, and you finally get to wear all the winter clothes you bought for no apparent reason. Considering these facts, my excitement for the trip was through the roof. After a 14 hour ride in a van with 10 other people and frequent restroom stops (much to the dismay of my professor) we finally arrived in Abingdon, Virginia to the joys of leaves turning colors and a crisp feeling in the air. A van full of (mostly) Florida-born students  seeing fall leaves for what was probably the first time was a van full of amazement and pure excitement. It sounds silly, but it was really wholesome seeing how giddy everyone got just by seeing some colorful trees (me included). We got to our hotel and prepared for the next day spent in the field. 

Day 2

Image 2. Rhyolite at Mt. Rogers with visible high silica flow banding (lava flow)

We woke up early in the morning and were able to enjoy a delightful breakfast made by the hotel to kick start our day. I packed my lunch and snacks and put on layers of clothes to be ready for any weather. I put on my new wool socks from the outlet store and old hiking boots that seemed structurally sound at the time (important to note for later). On our way to Mount Rogers in Damascus, Virginia we happened to take a road conveniently coined “The Twist”. As a long term participant in unwillingly becoming motion sick in situations such as going down one of the curviest roads in Virginia, I wasn’t thrilled. Luckily, I knew mountain roads could be bad so I packed some Dramamine which I made sure I took every time we got in the van from then on. 

Once we got to Mount Rogers my friend and I immediately had to use the bathroom which in this case, was wherever you felt like the trees concealed you enough. They don’t really mention this too much for field trips/field camps but bring toilet paper!! It will make your life a lot easier. After this venture, we were soon on the hunt for rhyolite. Rhyolite is a type of rock that my professor has talked a lot about and I had heard from other students that it is mostly what you will be seeing on the Virginia trip. It is a type of igneous rock that has a very high silica content so it is considered felsic (which is usually light colored). Rhyolite is made up of the minerals quartz, and plagioclase with smaller amounts of hornblende and biotite

The upper part of the Mount Rogers Formation consists mostly of rhyolite which we have, thanks to the continental rifting that occurred around 750 mya. The volcanoes that were once present here erupted and the igneous rock formed from the lava flow. 

Figure 1. Formation of rift valley in Mt. Rogers (From Radford)

We used our rock hammers that you can see in Image 2 to break off bits of Rhyolite and observe them under our handheld lenses. Through these lenses, we could (almost) easily identify the minerals present in our rock samples. 

Stop after stop, we observed more rhyolite. It became quite easy to answer our professor’s questions as to what type of rock we were looking at; the answer was usually “Whitetop Rhyolite”. There were, however, different types of rocks as we descended down the side of the mountain: buzzard rock and cranberry gneiss.

Image 3. Buzzard rock
Image 4. Cranberry gneiss

 

 

 

 

 

 

 

 

After we were finished at our first destination, we drove off to Grayson Highlands State Park. Here we observed more outcrops of rhyolite with a new fun bonus: tiny horses. Apparently, these tiny horses were let loose here in the late 20th century to control the growth of brush in the park. Now, there are around 150 of them that live in the park and are considered wild. While the park discourages petting the horse, you are able to get a cool selfie with them!

Image 5. Selfie with tiny horse in Grayson Highlands State Park

At the state park , there were lots and lots of giant rocks to climb on which everyone seemed to enjoy doing. So, while climbing the rocks, we were also observing and identifying them so it was a great combination. I was taking the liberty to climb almost every rock I saw and everything was going great for the time being. At one rock, I decided I wanted some pictures, for the memories! Mid mini photo shoot, I realized that the sole of my hiking boot had come clean off. Luckily, TWO very prepared people in my class happened to have waterproof adhesive tape and offered for me to use it to fix my boots. I was so thankful (and impressed that they had it in the first place) for the tape and used it to wrap my sole back to my boot and reinforce my second one because I noticed that the sole was starting to come off. The taped boots almost got me through to the end of the second day but I had to do some careful, soleless walking to get back to the van. I was able to go to the store near our hotel to get some replacement boots for the third, and final day in the field. 

Image 6. Realization of broken boot
Image 7. The final product of taped boots

Day 3

Image 8. Shale sample taken from outcrop along the Virginia Creeper Trail

The last day in the field was spent at the Virginia Creeper Trail in Damascus, Virginia. This specific trail serves almost entirely as a 34 mile cycling trail; by almost entirely, I mean entirely a cycling trail with the exception of a class full of geology students. Our day consisted of identifying rock types in outcrops along the trail and receiving a wide range of looks from cyclists passing by as our lookouts at the front and back yelled out for us to get out of the way. We walked around 1.5 miles of the trail, all while taking notes and pictures while our professor and teaching assistants were explaining each outcrop. Once we reached a certain point, our professor informed us that they would be leaving to get the vans and we would be walking back the way we came plus a half mile or so and identifying each outcrop while counting our steps and noting our bearings. So we measured our strides and got into groups to commence the journey. The goal of this was to eventually be able to create a map of our own that indicated each outcrop type and where they were on the path we took. 

Image 9. Mudstone displaying “varves”, which are a seasonal bedding pattern that develops in high latitude lakes. The thicker deposits develop in the summer and the thinner ones develop in the winter (please ignore my nailpolish-it is not a good idea to paint your nails before a geology trip).

This all sounds relatively simple, right? The answer is well, not really. The entire venture took around 4 or 5 hours and honestly made some people a little grumpy. I was happy though, because among the rhyolites and basalts, we were also able to see some really cool sedimentary rocks. Along the way we saw some awesome shale (Image 8) which we were told had some fossils in it if you looked hard enough. Of course, being interested in sedimentary geology I would’ve stayed forever chipping away at the shale to find a fossil but we were quickly ushered along by one of our professors. Shale is a type of sedimentary rock that is formed from packed silt or clay and easily separates into sheets. This type of rock is formed under gentle pressure and heat which allows organic material to be preserved easier as opposed to igneous or metamorphic rocks. As we continued along the trail we also saw mudstones and sandstones, diamictites, and conglomerates. After reaching the end of our journey, my group might have gone a little overboard and recorded 51 different outcrops. The outcrops we recorded could be reduced to: basalt, rhyolite, diamictite, conglomerate, sandstone/mudstone, and shale. The last field day was now concluded with tired feet but happy hearts as we listened to Fleetwood Mac in the van on the way back to the hotel.

Image 10. Diamictite (type of conglomerate) with poorly sorted grains suspended in a clay matrix. This specific rock was likely created by glacial activity and/or volcanic activity.

Day 4

We had a very early morning, skipped the hotel breakfast (they put out fruit and pastries for us though), and piled into the vans for a long journey back to Tampa, Florida. This trip was everything I had hoped it would be and made me fall in love with geology even more than I already was! I hope to go on many more adventures like this in the future. 

Bonus images of cool finds:

Image 11. Swallowtail feldspar (basalt) contains epidote and quartz. Lava cooled very quickly which caused rapid crystallization
Image 12. Rhyolite with pyrite (fool’s gold) clasts visible under hand lens

Fossil hunting—On Mars!

Did you see this in the news? NASA is starting a new Mars mission, and this one has a very exciting goal: to find evidence of past life! And to study the habitability of Mars for past life and for humans in the future. 

A new rover, called Mars 2020 until a name is selected (update: Mars Perseverance Rover), will be sent to Mars this summer, with an arrival on Mars February 18, 2021. The rover will explore the Jezero crater for about one Martian year, equal to 687 Earth days. Jezero crater was chosen for study because there is evidence that this crater once contained a lake. 

Elevation map of Jezero Crater. Dark blue and purple are deeper areas, yellow is the highest. The circled area is the area of the mission. NASA/JPL-Caltech/MSSS/JHU-APL/ESA. https://photojournal.jpl.nasa.gov/catalog/PIA23511

Two rivers, on the left side of the picture, flowed into a crater. A flood like broke through the crater wall and allowed water to drain out of the crater (upper right). Inside of the crater is a former delta formed as sediments were deposited as the rivers entered the lakes and deposited sediment.  

Artist’s concept of the delta formed within the ancient lake. NASA/JPL-Caltech/University of Arizona, https://photojournal.jpl.nasa.gov/catalog/PIA22907

Spectral analyses of the deltas and fans have revealed the presence of carbonates and hydrated silicas.

Spectral analyses of the detlas and fans have revealed the presence of carbonates and hydrated silicas.

Carbonate is a chemical composed of carbon, oxygen, and a metal or hydrogen. For example, chalk, seashells, and egg shells are all made of calcium carbonate crystals (CaCO3). Carbonates need liquid water and an atmosphere with carbon dioxide to form. On Earth, carbonate rocks may be formed by the accumulation of tiny fossil shells, but carbonates can form abiotically (without life). Limestone, a carbonate rock, is a good preserver of body fossils and trace fossils. Silica, a combination of silicon and oxygen, forms in water. Chert and flint are examples of silica rocks. Chert is also formed by the accumulation of tiny shells, but these are made from silica, not carbonate.

Any fossils that are left on Mars from its warmer, wetter periods would likely be found in carbonate and silica deposits. Scientists expect that these fossils would be microorganisms (single celled organisms). 

In addition to searching for fossils, Mars 2020, Perseverance will also: 

  • Determine past climates that may have allowed ancient life to exist
  • Study the geology of Mars, including the processes that affected and altered Mars’s surface, as well as looking for rocks that formed in water and what they might reveal about past life
  • Help prepare for human explorers by studying radiation levels on Mars’s surface and chemicals common in martian soil that are known to be harmful to humans. 

This may be a very exciting mission, but the wait will be long! The search for fossils will be the last part of the mission. But we’ll keep you posted!

For more information, visit NASA’s about this mission: Mars 2020 Mission and Mars Perseverance Rover.

Cretaceous Fossils of Mississippi

An Exogyra oyster from the Ripley Formation.

Cam here-

On June 3rd and June 4th of 2019 I traveled to Tupelo, Mississippi with another fellow fossil collector to collect Cretaceous marine fossils. This was the first time I have collected fossils dating back to the Mesozoic Era. The first location we visited was part of the Ripley Formation in Blue Springs, Mississippi. The Ripley Formation was deposited a few million years before the extinction of the non-avian dinosaurs about 71 million years ago. During this time, Mississippi was submerged under a shallow sea, and North America was cut by a large inland seaway known as the Western Interior Seaway. Mississippi’s Cretaceous oceans were teeming with life. The most common fossils found were oysters and clams that were plentiful in those ancient seas.

A view of the Ripley Formation field site.

The largest oyster found in the Ripley Formation was Exogyra costata. Other fossils found in that rock unit were marine snails called Turritella vertebroides, which were the most well preserved fossils from the Ripley Formation. Another common fossil unearthed as we dug under the Ripley Formation and approached the Coon Creek Formation were crab carapaces. One species of crab that I found reach to about 5 inches in length. I was nearly in shock as I was excavating it from its silty tomb. After we spent a few hours collecting, we began to wrap up our fragile finds in tin foil and put them in crates for safe transportation back home. Our last site we visited was an open field with exposures of the Demopolis Chalk Formation. This rock unit is a few million years older than the Ripley Formation. Nevertheless, this rock unit is rich in marine fossils.

It was in the beginning of summer and it was about 90 degrees, but what we were out looking for were shark teeth. In order to search for them we had to get on our hands and knees and crawl on the white hot ground. As uncomfortable as it may seem, this is how some of the best fossils are found. When collecting fossils the best thing you need to have is patience. After about 4 minutes of searching I saw something brown and shiny glinting in the sun. It was my very first Late Cretaceous shark tooth! The tooth belonged to the genus Squalicorax. This was about a 7 foot shark that swam the seas of Mississippi about 75 million years ago. It wasn’t long before I came across my second shark tooth, but it wasn’t as complete. Besides fossils we both found beautiful iridescent crystals of the sulfide mineral marcasite. After we spent an hour searching for shark teeth and other marine fossils in the Demopolis Chalk we decided to call it a day and head back to Huntsville, Alabama to start the next day of adventures.

A large crab collected from the lower Ripley Formation.
A Squalicorax tooth found in the Demopolis Chalk Formation.
All of the Cretaceous marine fossils I collected from Mississippi.

Fossil Collecting In Maryland

The beach at Matoaka Cabins, near low tide. The waves were brutal as a storm was overhead, with high wind gusts.

Adriane here-

It’s no secret that one of my favorite hobbies and past-time outside of researching fossils is fossil collecting for fun. So when I went home over Thanksgiving 2019, of course I took it as an opportunity to visit one of my favorite fossil localities, Calvert Cliffs in Maryland, on the Chesapeake Bay. I dragged my mom and two siblings with me on this overnight adventure, and it was a blast!

These cliffs are exposed along the east coast of the US, and are a part of Westmoreland State Park which I’ve written about previously. They contain beautiful fossil of late Neogene age (Miocene to Pleistocene, about 23-0.01 million years ago). The cliffs in Maryland contain the same age fossils, and the rocks and sediments are part of the Chesapeake Group (the name given to the group of layers that the fossils are contained in). There are several beaches in the area that member of the public can hunt at, but I’ll just go over a few sites we visited.

The first place we visited was Calvert Cliffs State Park. The park has a moderate entrance fee ($5 in state, $7 out of state), but it’s totally worth it. There are bathrooms here, along with a playground for kids (although, we all had a blast on the merry-go-round, to the point of almost puking). It’s a great place for families to visit with nice facilities. The trail to the beach is about 1.8 miles down a gentle slope, and towards the end of the trail there is a low-lying land where we saw several species of ducks and aquatic plants. At the mouth of the trail, there is a wooden bin with a variety of sifters for visitors to use to find fossils. The beach is flanked by the cliffs on either side, which are roped off. The cliffs are an excellent place to collect, however, they are and can quickly become wildly unstable, with huge blocks falling with enough velocity to seriously injure someone standing below. We found a few small shark’s teeth here, and some gastropod (snail) molds in the rocks. Nothing phenomenal.

Some of the shells at Matoaka Beach. Most are broken and battered, but hiding amongst them are undoubtedly tons of smaller shark teeth and other treasures!

The next place we visited was called Brownies Beach. Here, the beach is much longer, and at low tide, you can probably walk the beach for quite a while. Be warned, though, because like Calvert Cliffs, this stretch of beach is also prone to falling blocks. We spent quite a while here, and again, all we found were a few small shark teeth (scroll down for a video of my brother finding an incomplete tooth). There wasn’t a fee during the winter, but it did seem the beach has a fee during the summer.

One of the tanks at Calvert Marine Museum., with horseshoe crabs and a turtle. The tank next to it contained crabs, starfish, and sharks, all species that are native to the Chesapeake Bay.

The next day, I took everyone to Matoaka Beach Cabins. This was a really cool spot! The beach is privately owned, with the owners charging folks a mere $5 to access the beach all day. In addition, you can rent cabins here steps from the beach! The beaches are long and are not underneath the cliffs. We had a blast here, but at this point, we were in the midst of a huge rain storm that was hitting the east coast. We were drenched within the hour, and had to give up hunting for the rest of the day. We found another few shark teeth, some smaller pectens (clam) shells, and a dead pelican that I refused to let my siblings take back to my car. This beach is somewhere I’d love to revisit, especially at low tide. The shell line was wide, with several larger shells visible in the waves (the heavier teeth and fossils tend to be found with the same weight rocks, so finding larger rocks indicates the potential of finding larger fossils).

After leaving Matoaka, we then visited the Calvert Marine Museum. Being a paleontologist, I’ve visited a lot of museums, but this little museum remains one of my top five favorites. It combines the history of the region with paleontology and biology. For that reason, I’d recommend visiting the museum first. They have amazing display cases of the fossils found along the cliffs, so you can have an idea of what you’re looking for. You will also gain an appreciation of the rich wildlife in the Chesapeake Bay, and the native peoples that used to live here. Bonus, the museum also has three otters that are incredibly entertaining, as well as tanks of live horseshoe crabs, turtles, crabs, and fish species that are common in the bay.

For a list of fossils you can find in this region, information on the rock layers, and a list of all the beaches and their admission prices, check out the Fossil Guy’s website.

If you are on Facebook, I recommend joining the Fossils of Calvert Cliffs Maryland group. They share collecting advice, recommendations for beaches, and favorite restaurants. I consulted with the group before planning my trip, and several members gave me great food and beach recommendations!

Big Bone Lick State Historic Site

Mike here –

I recently visited Big Bone Lick State Historic Site (Union, Kentucky) on the way back to Ohio from a weekend in Kentucky. I’ve been meaning to visit this place for years, so I’m glad I finally had a chance to do so! Big Bone Lick is an important site for paleontology, archaeology, and US history.

Big Bone Lick SP is the site of a salt lick, or area where animals come to obtain salt and other minerals by licking the soil for salt crystals. Natural salt and sulfur springs are the source of the minerals at Big Bone Lick, and they attracted animals from all over.

In historical times, white-tailed deer and North American bison visited the lick, but much larger mammals came during the Pleistocene epoch (2.5 million to 12,000 years ago), also called the “Ice Age.” The remains of extinct mastodons, mammoths, North American horses, ground sloths, and tapirs have been found here, as well as the still living bison, musk oxen, and peccaries. Some of them became stuck in mud and died, and their preserved skeletons became the source of the “big bones!”

Diorama of a modern bison taxidermy with ancient neighbors.

Paleoindians hunted the megafauna at Big Bone Lick, and left behind their tools at the site. Native Americans continued to hunt here into colonial times, and told the Europeans about the big bones found in the soil. President Jefferson ordered Merriweather Lewis and William Clark to stop here on their expedition to investigate these reports. Specimens were excavated and eventually sent to France for analysis by Georges Cuvier, an anatomist credited with developing the concept of extinction. He compared the remains of Asian Elephants, African elephants, and the “elephants” found at Big Bone Lick and determined that these remains came a type of elephant that no longer lived. He named this animal Mastodon, but these fossils had already been described under the name Mammut. The study of these remains has given this site credit for the birth place of vertebrate paleontology in the United States.

The visitor’s center is on Mastodon Trail!

Long after the bison were extirpated (no longer present in their native habitat, but not extinct) from Kentucky, Kentuckians mined salt and opened a health resort, at which people bathed in the mineral-rich water. 

I have always loved the Pleistocene megafauna, and I make a point to see these fossils whenever I can. Mastodons are tied with Moropus (a distant relative of horses and rhinos, imagine a draft horse with claws!) as my favorite fossil animal, and get so excited seeing them! 

The visitor’s center has nice displays about the megafauna found at Big Bone Lick, including fossil material and reconstructions of what they may have looked like. There is information about the Paleoindians that inhabited this region and their tools. Historical information about Lewis and Clark is also included in the displays. 

A mounted giant ground sloth skeleton, and a display comparing mastodons and mammoths.

Behind the visitor’s center are life-size statues that represent iconic Pleistocene megafauna. Many of them are“trapped” in the sediment, and are on their way to become fossils. This was the perfect opportunity for a selfie with a mastodon!

A trapped mammoth and a dying bison.
My selfie with a mastodon!
A giant ground sloth.

The site is actually quite large, and features a campground and several hiking trails. I took one of these trails to see the salt/sulfur springs. I could smell the sulfur as soon as I reached this point in the trail. It was pretty awful, and it amazes me that people came to bathe in these waters for the “medicinal properties” centuries ago. 

A salt/sulfur spring with salt crystals.

I continued along a trail which follows Big Bone Creek. Fossils and artifacts are still exposed as the sediment washes away, and modern excavations occur when fossils are found on site.

These signs are all over the site.

 

Big Bone Lick Creek. Fossils are still exposed as the sediment is washed away through erosion.

Informational signs are included along the trails about the history of the site and about the animals that once lived in this region. 

The park maintains a small herd of American bison (Bison bison) on its grounds. The animals are rotated around their paddock to allow the plants time to recover from grazing and trampling. Unfortunately for me, they were located too far away for me to see with them with my limited time. It is hoped that the ecosystem will be restored to its condition before the bison were extirpated from this area. 

There be bison. Somewhere…

I had a great visit to Big Bone Lick State Historic Site! If you enjoy ice age megafauna, and are in or near Kentucky, consider stopping by! For more information, visit Big Bone Lick State Historical Site

Geology Tour of Washington, D.C.

Image 1: A marble sample with a black stylolite in the right-hand corner, caused by metamorphic stress to the rock. This sample was found in a bathroom in a café in D.C. Finger for scale.

Sarah here-

Recently, I went to the Washington D.C. area to visit the Smithsonian Museum of Natural History (which you can read about here) and to attend a workshop on best practices for new faculty members. But while I was there, I spied some excellent geology right in the city! I already showed you some of those while I was in the museum itself, so I’ll show you some of the other amazing pieces of Earth history that I saw!

I want to remind you that looking at amazing geology doesn’t have to wait for you to be on vacation or in a faraway destination-you can see these sites anywhere, if you’re paying attention! If you want to read more of these types of posts, check out my post from last year on the geology of bathrooms.

Image 2: This is a staircase in the Union Station in D.C.! This is another type of marble, but clearly a very different type of marble than the one we saw earlier.

This first image is of a beautiful stylolite in a marble countertop in the bathroom of a café in the center of Washington D.C. A stylolite is caused when rock, most commonly carbonate rocks like limestone (which we call marble when they are metamorphosed), are put under extreme pressure and the individual grains will compress and leak fluid, leaving behind a squiggly line, like what you see in image 1. Just beautiful!

Image 3: Here’s a granite sample I found on the wall of a building outside. The large crystals indicate that the sample cooled slowly. What I found interesting about this sample is the large presence of the darker colored mineral (amphibole) in the sample! Finger for scale.

Our next stop brings us to Union Station in Washington D.C., where I found this magnificent staircase completely by accident (image 2). I was visiting Gallaudet University and the first signing Starbucks, when I got turned around and ended up at a different Metro station than I had originally intended. Well, serendipitously, I found this absolute beauty, making the detour more than worth it. This rock, just like the image before, is a type of marble, though it has very different colors. The red color in this marble can be attributed to chemical impurities- red is typically what we’d see if iron and feldspar was present in the marble sample. You can also see veins filled with calcite and look like quartz all throughout the staircase! I was intrigued about where this marble came from, so I did a little research. There wasn’t a lot of information, but it seems that this marble likely came from Vermont (See this blog here: https://blogs.agu.org/magmacumlaude/2014/06/13/building-dc-union-station-just-the-floors/), which was created over 400 million years ago, when limestone produced from a shallow sea collided with a volcanic arc and metamorphosed in an orogeny, or a tectonic collision. This is a fairly common scenario with how we get a lot of our marble from the Paleozoic in North America.

Image 4: Here we can see phyllite, a low-grade metamorphic rock as a decorative feature of a wall. Phyllite is easily recognizable by its slight banding (which looks more like waviness when you’re looking at this particular rock) and the glittery sheen to it, given by the muscovite mica which develops during the metamorphic process.

Our tour continues to just outside of Washington D.C., to Arlington, VA, where I was visiting a friend in the area. As we were walking to breakfast, I was treated to a spectacular number of rocks featured in the buildings’ walls along the way. First, is a beautiful granite (image 3). The pink mineral is potassium feldspar (K-spar, for short), intermixed with the milky white mineral (quartz) and a lot of amphibole, the black colored mineral that’s heavily present on the left side of the block. Granite also usually contains biotite, a black mica.  If you take a look at this granite, you’ll see that the individual crystals are quite large, which tells us a lot about its formation. It’s telling us that it was formed intrusively; meaning, it was formed in an area not exposed to Earth’s surface and it cooled slowly, giving the crystals time to grow. I stopped to take a photo of this because the amphibole (there are many varieties of amphibole-hornblende is the most common in granite) because the heavy presence of the swirling amphibole isn’t something I usually see in most granite samples. Second, I saw these gorgeous phyllite samples on the outer wall of a building (image 4). Phyllite is a low-grade metamorphic rock, which means it’s not exposed to extremely high amounts of heat and pressure, but it has undergone significant changes from its protolith (otherwise known as its parent rock). In the case of phyllite, its protolith was a shale (compacted mud). You can recognize phyllite by a few different characteristics. During the metamorphic process, muscovite (a soft mineral in the mica family) develops, giving phyllite a really lovely shiny appearance (you can think of mica as being like nature’s glitter; just like glitter, mica is nearly impossible to completely get rid of if you accidentally get it everywhere!). You can also recognize phyllite by the gentle bands that form. Many metamorphic rocks are foliated, which we can think of as banding across a rock. The more pronounced the banding usually indicates a higher amount of metamorphism applied to the rock.  Phyllite has subtle banding, which indicates that lower amount of metamorphism.

So, this next image (image 5) isn’t in D.C., but it was found during this trip in College Park, Maryland on the University of Maryland’s campus. It’s another gorgeous example of granite, this time in a fountain. Sometimes it can be really hard to recognize rocks when you’re used to seeing them beautifully polished and sealed (like the granite in image 3, but you can definitely do it with practice!) Just like in image 3, if you look closely at this fountain, you’ll see large crystals, because it’s an intrusive rock, and the same types of minerals- our pink K-spar, milky quartz, and black amphiboles. An intrusive magmatic event from millions of years ago had to form and cool, and then that granite had to be exhumed (brought to the surface) for someone to make that fountain. So cool!

Image 5: A fountain on the University of Maryland’s campus made of unpolished granite. You can tell its granite by the types of minerals in the rock (quartz, K-spar, and amphibole) and the larger crystal grains that make up the fountain!

Last, but certainly not least, let’s look at the marble here in the Ronald Reagan airport (image 6). This gorgeous marble makes up part of a seafood restaurant right near the entrance to the airport, before you go through the security line. Sorry that the image is kind of far away, but this was the closest I was able to get before having to get through the security line! One of my favorite things about marble is how different it can look from sample to sample. This marble shows completely different features than the ones I showed in images 1 and 2-remember, the color of marble is driven by chemical impurities. You can see large scale veins of what is likely calcite all over the rock itself as well as some dissolution features on the left side.

Image 6: Marble being used as the wall around the elevator shaft in the Ronald Reagan Airport. This marble shows large veins and dissolution features that we didn’t see as much in images 1 and 2!