Scavenging the fossil record for clues to Earth's climate and life
Field Excursions
This page is where we will post any research, academic, or just-for-fun field work we do. The idea is to show you, the readers, what we do as paleontologists in the ‘field’.
In 2022, I took a road trip around Oregon on the west coast of USA to see all the incredible geology there is to see there. Oregon is an incredible natural geologic laboratory because there are so many different processes at play across different environments: you can see hydrology in action through massive waterfalls, naturally heated bodies of water from geothermal energy, the movement of sands in desert environments, and more- all in a single state! I’ll be writing a series of articles on the geology that I saw, so that I can share with you a small part of the incredible beauty that this Earth has to offer.
My journey started near Eugene, Oregon, a few hours inland from the Pacific coast, with a friend of mine from college. Our first stop was to go swimming at the Terwilliger hot springs in the Willamette National Forest. A hot spring is a naturally occurring feature caused by geothermal (geo meaning Earth, thermal meaning heat) activity- Earth processes cause the water in a spring to be far warmer than we would expect a typical body of water on the surface of Earth! This geologic phenomenon does not occur everywhere on Earth by any means.
So where does this geothermal activity come from and why is it restricted to certain locations? It comes from areas with volcanoes, both active and dormant (like Iceland, Hawaii, and Oregon!). The magma (lava that’s still underground) of the volcanic system is in contact with rocks closer to the surface of Earth- that heat is passed to water that is in contact with the rock (Fig. 1).
Figure 1. A diagram of how magma below the surface affects the temperature of ground water- as the magma chamber heats the porous rock above it, water that is in that rock is also heated and rises to the surface- in this case, it is a hot spring, but the water can also come to the surface in different ways, like geysers!
The temperature of the water can vary from pleasantly warm to extremely hot- meaning, some areas are safe to swim, and others are not (so if you’re in an area where hot springs exist, always check local safety guidelines!). Typically, areas with active volcanism (meaning, they’ve erupted in recent history, as opposed to dormant, where they have not erupted for some time, but have the possibility to erupt in the future) will have higher temperatures associated with their hot springs. At Terwilliger (Fig. 2), the water ranges from 112˙F to about 85˙F, so it felt a lot like a hot tub! The hottest water is closest to where the water begins to flow- so, the water closest to the heat source- as it travels downstream, it cools.
Figure 2. The hot springs, from an upstream view. The pool directly in view is the warmest- as the water in it travels downstream, it cools a bit.
Due to the nature of hot springs, the water there often contains a high amount of dissolved minerals, and the minerals present in them can range drastically, as can the pH of the water. Often, you’ll find that the water can appear very different in color and clarity across different hot springs, and that’s why- the dissolved minerals. In Teriwilliger, the water has a lot of sodium, calcium, magnesium, iron, aluminum, silica, and sulfates present in it.
Despite the high temperatures of the water, life still thrives in this environment, too- while this hot spring is not among the warmest, it is still a difficult environment for many different organisms to survive in. However, certain species of blue-green algae, or cyanobacteria, have adapted to be able to thrive in these extreme freshwater environments (species that can live in extreme environments are called extremophiles), where most other species cannot. These cyanobacteria can be seen on the rocks closer to the edges of the pool (Fig. 3) and it can be very slippery if you step on it- so be careful! I wanted to highlight these cyanobacteria because cyanobacteria represent some of the earliest complex life on Earth, with their fossil record extending billions of years- we can thank them for providing a lot of the oxygen we breathe today! Biology and geology are intertwined with one another, so by studying both, we can get a fuller picture of the world around us.
Figure 3. A close-up image of one of the pools at the hot springs- note the distinct color of the water and the blue-green algae (cyanobacteria) that coats the rocks. It’s tough to see the cyanobacteria in the deeper water, but toward the edges, you can see a colorful sheen- that’s the blue-green algae! A limited number of organisms on Earth thrive in extremely warm waters, but those that have adapted to these extreme environments can really thrive there!
Straight shelled Cephalopod collected by Terry Frank.
Cam here–
I have been quite busy for the past couple of months. In late May I had the chance to visit the state of Missouri to collect fossils and visit museums. Missouri is the farthest I have traveled so far to look for fossils. In this post I will highlight some of the trips I took and the fossils I collected along the way.
On Sunday morning we traveled up to Jefferson County, Missouri to collect fossils from the Decorah Formation. The Decorah Group was deposited in shallow tropical seas during the Late Ordovician Period (~445 million years ago). It is humbling to realize that what we were standing on used to be the seafloor. We found a variety of fossils such as brachiopods, bryozoans, bits of trilobites and corals. The biggest fossil found in the Decorah Group are the shells of huge straight shelled nautiloid cephalopods. These were top predators during the Ordovician Period. I did not realize the sheer size these animals could grow up to until Terry Frank showed me examples he collected on past trips.
Shark tooth I found from the Salem Limestone. Probably from the genus Orodus.
We also went to search for shark and fish remains from the Salem Formation. These rocks were deposited in a shallow sea during the Lower Carboniferous (Mississippian) Period. We were guided by a former geology student Adam Marty. Adam knew the stratigraphy of the region like the back of his hand. He took us to a locality that was hard to get to but ended up being very rewarding. We had to hike up a steep hill and cross bushes to get to the collecting area. Adam told us to break open the limestone blocks and look for shark teeth. Not only did we find teeth but we found cartilage, which is hard to fossilize. Many of the teeth were round in shape due to the animals using them to crush shells such as brachiopods and ammonoids. These were the only vertebrate fossils we found on our long week trip. It was a special treat because my research papers are on cartilaginous fish teeth.
A brachiopod shell in limestone that was used to build a local restaurant.
The trip was a great success. The geology was different from what I am used to seeing. Even the buildings that we walked by had fossils in them from the local rock that was used. The rocks in Missouri play an important role in the industrial growth of the state. I had a good time exploring parts of the Midwest and I plan on visiting again soon.
A cluster of brachiopod shells from the Decorah Limestone.
Linda and guest bloggers Blandine (hyperlink to Meet the Scientist) and David (hyperlink to Meet the Scientist) here – in August 2021 we packed our bags, hand lenses and sunscreen, and hopped on a plane to go on a field trip in Lourinhã, Portugal [Fig. 1]. This city is known as the Portuguese capital of dinosaurs because of its fossil-rich Jurassic outcrops. It even is the eponym (name giving location) for several taxa: sauropod dinosaur genus Lourinhasaurus, theropod dinosaur genus Lourinhanosaurus, sauropod dinosaur species Supersaurus/Dinheirosauruslourinhanensis. Today, Lourinhã is located on the Portuguese Atlantic coast. While small beaches exist, the majority of the coastline consists of tall, rocky cliffs. This area looked very different during the Mesozoic Era though.
Fig. 1. Map of Portugal with all locations highlighted that we visited or mention in this text. Figure made by David.
When Pangaea fell apart and the North Atlantic began to open, the Lusitanian rift basin formed due to the extension of the crust in the area that is today western Portugal. The Lusitanian basin was likely bordered by the Berlenga horst in the west and by the Central Plateau of the Iberian Peninsula (Meseta Central) in the east [Fig. 2]. During the Late Triassic, the evaporation of sea water in the Lusitanian Basin led to the deposition of a thick and ductile salt layer, which later caused instability in the overlying sediments. The formation and movement of salt domes constantly changed the topography and thus modified the course of river beds. The relative sea level at the coast of this area was fluctuating during the Jurassic, and as a result we observe layers representative of large, meandering rivers and layers richer in terrestrial plant material when the sea level was at its lowest, occasionally marine intercalations (with shallow marine fossils such as oysters) and fine, muddy deposits from entirely marine environments.
Fig. 2. top: Schematic showing today’s coastline (red) and key locations on top of the Jurassic landscape and main geological features. bottom: Artist’s/David’s reconstruction of the Jurassic ecosystem. Figure made by David.
The dinosaur fauna of Portugal is similar to the ones of the Morrison Formation in the US and the Tendaguru Formation in Tanzania, with several genera, such as Allosaurus, Ceratosaurus and Torvosaurus occurring in all three localities [Fig. 3]. This is remarkable since these regions were separated by the sea during the upper Jurassic; the former supercontinent Pangaea was already breaking up. That means that a faunal exchange between North America (Morrison Formation), the island Iberia (Lourinhã Formation) and Gondwana (Tendaguru Formation) was still possible, probably in times when the sea-level was low.
Fig. 3. Paleogeography of the Jurassic, showing possible connectivity between geologic formations with very similar dinosaur fossil assemblage.
Day 1) Praia de Vale Pombas and Dino Parque Lourinhã:
We spent the morning of our first day at the Praia de Vale Pombas, a small beach south of Peniche. You very quickly forget the beautiful scenery when you spot a fossil. Within minutes we found large fragments of fossilized wood and got very excited when we found bones quickly after that. Most remains were fragmented and we could not identify them, but we found a theropod metatarsal (foot) bone [Fig. 5] as well as a small piece of a rib of an unidentified animal.
Please note: while fossil collection is permitted at this specific outcrop, the different municipalities in this area handle this matter very differently, many do not allow collection by private collectors but only professional scientific excavations for which you need to file a request. Always follow the local regulations when in the field, many fossils are beautiful, but not yours to take. Also make sure to always inform the authorities when you spot something potentially important.
Fig. 4. Blandine (left) inspects a find while Linda (right) is busy extracting a dinosaur bone.Fig. 5. Theropod metatarsal (foot) bone. During the collection process, this fossil cracked and broke into several pieces. But fortunately, we were prepared and glued it back together.
In the afternoon we visited the Dino Parque in Lourinhã. A small museum in the park showcases the locally found dinosaurs with original skeletons and replicas, as well as methods and techniques used in the excavation process and during fossil preparation. The largest section of the park is a huge outside area showing life size reconstructions of different dinosaur species. We received tours behind the scenes and talked to the staff and preparators who explained their work to us. This was so much fun that we wrote a separate post just about our day in this park, check it out here [hyperlink to blog post]!
Day 2) Museu da Lourinhã:
On the second day, we visited the Museu da Lourinhã, the museum of the city of Lourinhã dedicated to the region’s geological and historical heritage. In the paleontological gallery, numerous locally found dinosaur fossils, including eggs with embryos of the theropod Lourinhanosaurus are presented. The museum’s archeological and ethnological exhibitions deal with human history in the region and show how people lived here in the past.
We were given a thorough tour of the geological and paleontological section by Carla Tómas, one of the museum’s preparators, who also led us behind the scenes into the preparators’ laboratory. Here, the preparator team works on the preparation and study of local and international vertebrate remains. While we were there, Carla explained to us that her specialty is to find new methods to stabilize very fragile fossils by preparing and treating them chemically. Some geological properties can lead to poor bone preservation, for example the presence of salt can result in extremely brittle fossils. It is therefore important to understand the chemical processes happening and stop the degradation of the material to preserve the fossil.
Day 3) Ponta do Trovão, the Toarcian GSSP
Not far away from our accommodation in the town of Peniche, just north of Lourinhã, there is a GSSP [Fig. 6]. GSSP stands for Global Boundary Stratotype Section and Point and refers to physical markers between specific layers of rock, marking the lower boundary of a stratigraphic unit. For each stage on the geologic time scale, scientists are trying to identify one GSSP somewhere in the world, indicating exactly the boundary between two stages. The end/beginning of a geological stage is defined by a change, commonly a change in fossil assemblages such as an extinction event or the first appearance of an index fossil. Currently, less than 80 GSSPs have been ratified, the vast majority of which are located in Europe. The GSSP we visited is located at Ponta do Trovão in Peniche, and marks the beginning of the Toarcian (early Jurassic, 182.7 million years ago). It is defined by the very first appearance of the ammonite genus Dactylioceras (Eodactylites).
Fig. 6 Information board and GSSP ‘spike’ at Ponta do Trovão, marking the exact end of the Pliensbachian (below the spike) and the beginning of the Toarcian (above the spike).
We spent the rest of the day exploring the area, looking for fossils in the layers below the GSSP (thus not in the Toarcian, but the previous stage, the Pliensbachian) and found thousands of belemnites [Fig. 7]. Belemnites are an extinct group of cephalopods, which looked similar to today’s squids but with hooks on their ten arms. They had an internal skeleton called the cone, of which only the calcitic guard (called rostrum) commonly fossilizes. In addition to belemnite rostra scattered around, we also spotted a few coprolites, the fossil remains of poop [Fig. 8]. It appears that something has been snacking on ancient “calamari”, but could not digest the hard, calcite guards. Between the large number of rostrum fragments, we also discovered a number of ammonites, some of which – especially when they were located in the intertidal zone and thus currently in contact with sea water – were beautifully pyritized [Fig. 9].
Since this is a special outcrop, a GSSP, we did not collect fossils here, but only marveled at their beauty.
Fig.7 Fragments of belemnite rostra found at Ponta do Trovão.Fig. 8 Coprolite (fossil poop) consisting of indigestible belemnite remains. Scale in cm.Fig. 9. Fragment of a small ammonite, shimmering golden because of pyrite, an iron sulfide mineral also known as fool’s gold.
Day 4) Praia Formosa, Praia de Santa Cruz, Praia Azul and excavation sites of the municipality of Torres Vedras
In the morning we joined a guided tour given by Bruno Camilo Silva, a local paleontologist. We learned about the geology at Praia Formosa and Praia de Santa Cruz, two beaches south of Peniche. The tall cliffs here show wonderful profiles of the rock layers of the Lower Jurassic, providing insight into the sedimentological history of this place. At the time, tectonic movements and underwater currents would cause sediments to slide down the Berlenga Horst from time to time. Those events formed a sediment known as turbidite, occurring here as massive conglomerates. We can see clearly where these turbiditic flows eroded the older sea-floor sediments, leaving irregular contacts between the layers [Fig. 10]. Considering that the Berlenga Horst was quite far away from the location these layers were deposited, it is difficult to imagine the sheer size of the sediment flows and the amount of material that must have been transported.
Fig.10 This outcrop at Praia de Santa Cruz shows fine, gray, sea sediments which are disturbed and eroded by badly sorted reddish brown sediments, a turbidite.
The layers below the turbidite in this area are unfortunately quite poor in body fossil content, despite numerous traces of invertebrate activity in the sediments. Based on those ichnofossils such as burrows, it is assumed the area had probably a rich benthic fauna, which has not been preserved in the sediment because the conditions were too unfavorable for fossilization. The fact that we know there was abundant life but all that’s left of it now are ichnofossils and we may never know which organisms once roamed the seabed here is quite humbling. After brooding about this, we chose to have our lunch break at Praia Azul, the blue beach. We used this occasion to search for fossils at the foot of the cliffs near the beach while eating our sandwiches. The most common fossils that can be found here are oysters, marking times of shallow marine conditions. Several large oyster banks are preserved [Fig. 10], though wood and other isolated plant fragments also occur frequently. In addition to these finds, coprolites, signs of bioturbation such as re-filled burrows, and – very rarely – small bones can be spotted in the cliffs of this beach.
Fig. 11. Fossil oyster bed at Praia Azul, shoe for scale.
In the afternoon, we visited active paleontological excavation sites, of which we promised to keep the locations secret in order to avoid people disturbing the ongoing work/research. A team composed of local volunteers, international students and experts, and employees of the municipality of Torres Vedras were excavating turtle and crocodylomorph remains. At a second location nearby an almost complete but at the moment of our visit still unidentified theropod dinosaur was excavated, ready to be covered in plaster and to be lifted and transported to a preparation lab to finally see the light of day again. Blandine picked up a rock very close to one of the sites and found a small tooth (identified by staff on site as possibly hybodontiformes, a sister taxon of sharks and rays), which she handed over to the excavation team so it can be included in the research. In the evening, to finish an exciting day, we paid another visit to Ponta do Trovão to search for fossils with the sun setting over the Berlengas archipelago, the remnant and eponym of the aforementioned Mesozoic horst structure, on the horizon [Fig. 12].
Fig. 12. Sunset over the Atlantic ocean, the Berlengas archipelago in the background.
Day 5) Foz do Arelho and Parque de Merendas
While we spent most of our Portugal trip in the fossil rich localities along the coast south of Peniche, we planned to explore some places north of the city on day 5. After checking geological maps of the region in order to find promising localities we decided to head to the cliffs of Foz do Arelho first. While the place itself was a spectacular sight, we didn’t find any fossils there. So, we went further north to the cliffs of Parque de Merendas near Serra do Bouro. Again, this was an amazing locality, but with very few fossils. We found interesting green minerals on and around plant remains. Bone fossils, however, were very rare, but Blandine, our dinosaur expert, found a large fragment of a dinosaur bone that could not be further identified [Fig. 13].
Fig. 13. Dinosaur bone fragment found at the cliffs of Parque de Merendas.
Day 6) Praia de Porto Dinheiro, Praia do Zimbral and cliffs near Porto Batel
Fig. 14. David extracting a small piece of dinosaur bone from the rock.
We spent the next day going to Praia de Porto Dinheiro (the town is the eponym of the dinosaur genus Dinheirosaurus) near Rebamar and to Praia do Zimbral, where we met with the local paleontologist and the geologists we had already encountered a few days earlier. While the group was excavating an unidentified fossil bone fragment, David found another piece in the rubble that had fallen from the cliff into the beach, extracted it [Fig. 14], and handed it to the local paleontologist so it could be included in their work.
For lunch we went to a local restaurant just next to Praia de Porto Dinheiro, which has a large Sauropod bone being showcased under glass plates below the floor in the entrance. The owner of the restaurant showed us a large Torvosaurus tooth from his private collection. Even the sink in the bathroom is made out of a piece of fossil oyster bank. Later that day we met again with the other geologists and paleontologists at the cliffs near Porto Batel. At this locality dinosaur footprints can be found: The group showed us large theropod tracks [Fig. 15], and the filling (negative) of a deep Sauropod footprint up in the cliff [Fig. 16]. Although way too far above for us to check, we were told that skin impressions can be found in this footprint.
Fig. 15. Large theropod dinosaur footprints at the cliffs near Porto Batel, hammer for scale.Fig. 16. The infill of a sauropod footprint at the cliffs near Porto Batel, David for scale. The cliff is slowly eroding, endangering the track.
All in all, our trip to Portugal was very exciting. We could observe plenty of fossils including dinosaur bones in the beautiful scenery where the Atlantic ocean is inexorably gnawing away at the rocks that once were the walking grounds of the giants of the past. If you know where to search it is impossible not to find nice fossils, though please remember: Collecting fossils is not permitted everywhere in this area! Inform yourself prior to your trip and stick to the local laws and regulations! The city of Lourinhã itself, its museum, and dinosaur park are also worth a visit; the geological heritage of the region is felt everywhere in the streets, the people in this area live and breathe dinosaurs, with many shops, restaurants, businesses and cafés including the term ‘dino’ in their names and life-size dinosaur models and art found in many places.
In case you haven’t had enough, here are some additional impressions of our trip [Fig. 17-22]:
Fig. 17. Sauropod graffiti on a no entry sign in Lourinhã.Fig. 18. Blandine (left) and David (right) inspecting the outcrop at Ponta do Trovão.Fig. 19. Pterodactyl reconstruction in the streets of Lourinhã.Fig. 20. Linda (left) and Blandine (right) at the cliffs at Serra do Bouro.Fig. 21. Lourinhanosaurus antunesi replica in the Museu da Lourinhã.Fig. 22. Blandine’s hand on top of theropod footprints at the cliffs near Porto Batel.
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 layers 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↓④’ 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.
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
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.
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 🙂
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 rockImage 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 bootImage 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 crystallizationImage 12. Rhyolite with pyrite (fool’s gold) clasts visible under hand lens
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.
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!
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.
