This is the Stone City Fossil outcrop. It’s been called one of the most fossiliferous locations in Texas. The fossils here were deposited about 35 million years ago during the Eocene Epoch of geologic time. The rock type here is a sedimentary rock meaning the rock is composed of sediment that has been compressed over time. Here, the rock is actually soft enough to dig into and that makes it perfect for locating fossils.
Fossils are the remains of organisms that lived in the geologic past and finding them in rocks can give you a great clue about Earth’s past environments. Today, certain animals and plants are only found in specific areas so, for example, whales are in the oceans and bears are terrestrial. That’s exactly how it was in the geologic past. Each organism lived in a specific geological environment. Therefore, geologists can use fossils to interpret whether a location was on land or under the ocean and can get water depth, water temperature, salinity, and more.
Fossils are preserved in several ways:
1) The original material is replaced by another mineral. Pyrite or fool’s gold is an example of a mineral that will replace original material.
2) The original material is recrystallized. The fossil may look gray when recrystallized.
3) The pore spaces in the original material are filled with another mineral. This is called permineralization. Petrified wood is an example of a fossil that was preserved this way.
4) The fossils are unaltered and look similar to modern equivalents. Relatively young fossils are preserved this way.
5) The original material is compressed into a thin layer of carbon. This is called carbonization. The fossils will look black and be very flat.
The Stone City fossils tell geologists that during the Eocene, 35 million years ago, the Bryan/College Station area was under about 100-200 feet of ocean water…. much different than today! Common fossils include gastropods (snails), pelecypods (clams), corals, ootoliths (fish ear bones), bryozoan, and you can sometimes find sharks teeth and squid beaks. Overall there are about 50 different types of fossils that can easily be found here. This is a great location for kids when the water is low so feel free to bring the little ones!
To receive credit for this earthcache you will need to do the following:
1) Locate at least 5 fossils. Are they gastropods, pelecypods, corals or others?
2) How do the fossil shells compare with modern shells you can find at the beach?
3) What type of fossil preservation can you see in the Stone City fossils (replacement, recrystallization, permineralization, unaltered, or carbonization)?
4) Email your answers… do not post on the log!
SAFETY NOTES!
1) There is POISON IVY here so beware!
2) Do not visit this cache when the river is high! The fossil site will be underwater and dangerous to approach. Also, right after the rain the location will be very muddy and possibly challenging. Use common sense and log this site when the river is low.
Thanks to Texas Bandits for the website (below) to the National Weather Service's official site. You can check the current river level. Anything 10' or below is ideal. Higher than that, things can be muddy and dangerous. And 15' and above makes the area un-accessible.
http://water.weather.gov/ahps2/hydrograph.php?wfo=hgx&gage=bbzt2
Additional notes: Parking: The parking area is just west of the bridge over the Brazos River on Highway 21. Park at the following coordinates and walk down the slope to the fossil site. N 30° 37’36’’ W 96° 32’41’’ Stay near the posted coordinates for the fossil site. Straying too far upriver (north) or down river (south) will take you on to private property. Please stay on county property near the bridges.
This cache was created by scissortail77 for the Texas Master Naturalist Brazos Valley Chapter