Fossil Collecting at Caesar’s Creek Spillway

Mike here –

The Caesar Creek Lake Visitor Center

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

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

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

The walls of the spillway. Filled with fossils!

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

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

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

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

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

 

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

Urban Fossil Hunting

Mike and Jen here –

Figure 1

I couldn’t believe what I was seeing. I was on a tour of campus for my paleontology course, and Dr. Sandy took us to a low retaining wall in front of the Science Center. There it was: a large Pentamerus brachiopod (Fig 1). I’d walked by this wall for years and never noticed it before! During the rest of the tour, I saw fossils all over campus, and I had never even thought to look for them in the building materials.

Ever since then, I’ve taken closer looks at the stones used in buildings to see if there are fossils. You should, too! But ignore the igneous rocks and marble, just go for the limestone, dolostone, and sandstone pieces. The fossils I’ve seen include trace fossils and body fossils. Trace fossils are fossilized behavior of an organism, whereas body fossils are the actual skeletal or imprint of remains.

Figure 2

Primarily, I’ve encountered trace fossils. The Dayton Limestone, a formation found near Dayton, Ohio, is Silurian-aged (443.8-419.2 million years ago) limestone that was used for building foundations all over the state. It is full of burrows that are highlighted by a lining of hematite (Fig 2). The hematite likely came into the burrows after the organisms were done occupying them. This mineral helps the burrows stand out in the rock. The foundation on the left is a building on the campus of the University of Dayton. The founding on the right is a building in downtown Springfield.

Figure 3
Figure 4

Further exploration for urban fossils led me to find trails on the base of a lamppost outside of one of the courthouses in Springfield (Fig 3). I forgot a scale for this picture, but these trails were about 10 cm in length. I found this next burrow (Fig 4) in one of the retaining walls outside of the library at UD. See what I mean about fossils in places you wouldn’t expect them?

Marine animal body fossils are quite easy to find in building materials. I found these Silurian fossils in a retaining wall near some of the older buildings on UD’s campus. Large brachiopods and gastropods may be found in these stones (Fig 5), as well as colonial corals and horn corals (Fig 6). Sometimes it is difficult to recognize the fossils because the animal is within the rock and you are only getting a two-dimensional view of what it looks like.

Figure 5
Figure 6
Figure 7

Sometimes, the fossils can be very small and hard to pick out from the rock they are in. I walked by this wall for nearly 15 years and never noticed all of the gastropods, bryozoans, and crinoids until just a few weeks ago (Fig 7)! Another example of small fossils was found by Jen when she went to the Biltmore Estate in Asheville, North Carolina. She was chatting with her family when she looked down and recognized the rock, it was filled with small gastropods and bryozoans that she knew to be Mississippian (360-325 million years ago) in age (Fig 8).

Figure 8

Be sure to be on the lookout inside of buildings, too! Many building stones are made of fossiliferous rocks and they are quite visually appealing so they end up as table tops, counters, and even bathroom stalls! Jen saw this table, made of polished fossiliferous limestone, inside of the Biltmore house (Fig 9). I found these ammonites in the flooring at the Ohio Statehouse (Fig 10). Each side of the tile was about 2 ft in diameter.

Figure 9
Figure 10

Where Jen lived in Eastern Tennessee, the common limestone is called the Holston Limestone. This is the ‘marble’ that gave Knoxville the name of Marble City. Marble is a metamorphic rock whereas limestone is a sedimentary rock. Sometimes limestone can have really small grains that makes it look like marble. As a local rock it is used all over the city in a variety of places. It decorates the exterior of buildings downtown (Fig 11) and is even sculpted into monuments of past events (Fig 12).

Figure 11
Figure 12

Maggie and Jen went on a recent research trip to Oklahoma and noticed something interesting about their window sill in the kitchen (Fig 13). It was a nice pink color with lots of white specks. It happened to be the Holston Limestone from where they both were living in Eastern Tennessee! This rock has very specific features that allow you to identify it wherever you may be. Jen even discovered this rock in an old hotel (now a university) in St. Augustine, Florida.

These just a few examples of the fossils that we have seen used in construction and design. As you walk around city buildings, be on the lookout for limestone blocks, especially on older buildings. There may be a few fossils hiding in plain sight!

Figure 13

Ancient hydrothermal seafloor deposits on Mars

Ancient hydrothermal seafloor deposits in Eridania basin on Mars
Joseph R. Michalksi, Eldar Z. Noe Deobrea, Paul B. Niles, and Javier Cuadros
Summarized by Mike Hils

What data was used? High resolution imaging and spectroscopy data about mineralogy and geology

Methods: Used data from instruments on the Mars Reconnaissance Orbiter, a satellite currently orbiting Mars:

    HiRISE (High Resolution Imaging Science Experiment) was used to define the ancient basin boundaries and to inspect the types of features and rocks located in the Eridania basin. HiRISE is a camera onboard the Mars Reconnaissance Orbiter than can resolve objects to about a foot long on the surface of Mars.

    CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) to study the minerals and rocks found in the Eridania Basin. Materials bounce light off of them in a consistent pattern and energy, and spectrometers can analyze that light and identify the material on Mars’ surface.

Results: The Eridania Basin was probably up to 1.5 km (0.9 mi) deep, and flowed into a canyon named Ma’adim Vallis. Images from HiRISE show that the western half of the basin consists of massive stone that lacks bedding planes and has eroded into buttes and mesas. The basin would have held about as much water the Caspian Sea on Earth currently does. This basin is shaped different than many of the other Martian basins, and it is thought that a covering of ice kept sediment from settling on the bottom. A comparison of the craters in this part of the basin suggest that these rocks are about 3.77 Ga (G = giga, SI prefix for billion, a = annum, Latin for year) old.

Analysis from CRISM found evidence of minerals and rocks associated with deep ocean water on Earth, including iron and magnesium rich clays, serpentinite, carbonates, and chlorides. For example, serpentinite, a metamorphic rock that looks like green marble, forms when basalt reacts with warm, deep sea water. Carbonate minerals are common on Earth in the form of limestone, marble, seashells, and corals. The authors suspect that the carbonate formed due to hydrothermal interactions. Chlorides, such as salt (sodium chloride), form on Earth when water evaporates.

Map of the Martian terrane with colors indicating highs (orange) and lows (blue) of an ancient sea. The data points in the legend are minerals that were identified at each location.

Why is this study important? This study is important in two ways. First, one idea for the origin of life on Earth is that it developed around hydrothermal vents in the ocean. Although ancient rocks have been found suggesting such environments in the past, they have been significantly altered by weathering and metamorphism, and vital information has been lost. Martian sites, which haven’t been altered nearly as much as Terrestrial ones, might be a good proxy for understanding early environments on Earth. Secondly, the identification of such sites on Mars could provide key places to look for signs of life on Mars.

The big picture: Understanding how life began is a huge problem that scientists in many fields are exploring. Life may have evolved on Earth, or it may have arrived here from some other body. The identification of hydrothermal environments on Mars would allow scientists to gain a better understanding of hydrothermal environments on Earth as life was evolving and try to see if life could have started here. This would also allow astrobiologists to look for evidence of extraterrestrial life on Mars.
Two other bodies in our solar system may harbor life around hydrothermal vents. Jupiter’s moon Europa and Saturn’s moon Enceladus are both covered in salty water capped with ice, and both experience tectonic activity due to the gravitational pull from their host planets. In addition, organic molecules (chemicals made mostly of carbon that are often associated with organisms) have been detected in water escaping from Enceladus. If life could have evolved in hydrothermal environments on Earth and Mars, it is likely Europa and Enceladus both host extraterrestrial life now.

Citation: Michalski, J., Dobrea, E., Niles, P., Cuadros, J. 2017. Ancient hydrothermal seafloor deposits in Eridania basin on Mars. Nature Communications, 8:15978. doi: 10.1038/ncomms15978