an Oscar See Down My Pants Pocket? Tom Jones Can. That's Quirky!" (Well, he didn't say "quirky", but the other "q" word is not politically correct!) This is a convenient way to remember: Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, Permian, Triassic, Jurassic, Cretaceous, Tertiary, Quaternary. The dinosaurs lived during the Triassic, Jurassic, and Cretaceous periods 230 to 65 million years ago. See this link for a good explanation of geologic time.
A Gastropod fossil found in a limestone rock at Haw Ridge in Oak Ridge.
On a walk along the trails at Haw Ridge youll see lots of limestone outcroppings that contain fossils of ancient sea animals. Look closely at this photo, youll see some nice brachiopod fossils. Limestone is an indicator that an area was once under an ocean. Limestone was formed from seashells that settled to the ocean floor. Over long periods of time and pressure the calcium carbonate (CaCO3) in the seashells was transformed into limestone. Geologists test limestone by putting drops of hydrochloric acid on it; if it bubbles, the rock is limestone. The hydrochloric acid reacts with the calcium carbonate and releases carbon dioxide gas (CO2).
