We start our journey in the Paleozoic Era, when multi-cellular life was starting to diversify, filling niches in ocean environments and eventually moving on to land.
In Mississippi, we see only a very small portion of this time frame outcropping at the surface. Rocks in the most northeastern part of the state are from the Devonian Period (385-359 million years ago).
During the Devonian, sea levels were high and this area was covered with water.
Carboniferous-aged lignite coal deposits can be found in Choctaw County. Coal forms in warm, plant-rich, swampy areas. When the plants die, they are buried in oxygen-poor water where they accumulate and decay very slowly, turning them to peat. The peat is compressed and buried over time to create lignite. Lignite is the least dense type of coal containing only about 65% organic material and producing approximately 17 megajoules of energy per kilogram. Compare this to anthracite coal, which has 95% organic material and produces up to 33 megajoules of energy per kilogram and you can see why lignite is not the preferred energy producer. (eia.gov)
Lignite Coal from Mississippi
This slab of limestone shows a wide variety of taxa in just a small piece of (4"x6"). These are compression fossils, which form along bedding planes in the rock. When you retrieve a rock from the ground and hit it with a hammer, it will break along the plane where the fossils are preserved to reveal hidden treasures inside.
The lower portion, called the "part", preserves the fossils themselves while the upper portion, called the "counterpart" preserves a mold of the specimens. In this image the part is on the left and the counterpart is on the right. Can you identify any of the taxa you see in the fossil? If you need a hint, go to the "Fossil Field Guide" portion of the exhibit.
Slab of fossil-rich limestone from northeast part of the state.
