Here’s some information about the fossils found in the “red dirt” that naturally dissolved from Indiana Limestone:
What are they? These fossils are all that’s left of sea animals that lived a really long time ago.
How long ago? Long before the earliest dinosaurs — about 350 million years ago.
What kinds of animals were they? They were mostly sea animals that didn’t move very much, if at all, when they were alive. The most common ones were:
Crinoids. Broken stems of crinoids look like beads. Crinoids are sometimes called sea lilies, but they are actually animals related to sea stars.
Horn corals. These coral skeletons are shaped like cow horns. Horn corals lived alone (like sea anemones), not in colonies (like most other corals).
Broken bits of stick corals look like hollow twigs, but they are made of rock. Stick corals grew in bush-shaped colonies.
Skeletons of bryozoans are covered with pin-prick sized holes. A tiny animal once lived in each hole. Bryozoans are also called moss animals.
Where were the fossils found? They were collected on a hill top in Southern Indiana (about 20 miles south of Bloomington).
How did they get there? The hill is made out of limestone rock. The fossils were originally part of the rock. The rock at the very top of the hill gradually dissolved away over thousands of years. All that was left behind was bits of rock, fossils, and reddish clay.
What’s limestone? Limestone is a rock that’s often made of the skeletons of sea animals. The limestone in that hill is the world famous Indiana Limestone. Indiana Limestone is quarried and used as a building stone.
Where can I find Indiana Limestone? Look at older buildings, especially those made of brick The window sills (yellow arrow) on many older brick buildings are made of Indiana Limestone. Also, if you ever go to the Maze Branch of the Oak Park Public Library, look closely at the front steps — they’re made of Indiana Limestone! You can even see tiny fossils in the steps.
Where can I learn more about Indiana Limestone:? Follow these links:
Lots of information and photos here: http://academic.brooklyn.cuny.edu/geology/powell/613webpage/NYCbuilding/IndianaLimestone/IndianaLimestone.htm