Paleontology and geology
Cretaceous rocks are exposed in southern and northeastern Arkansas. These shallow marine deposits are composed of sand, silt, chalk, clay-rich carbonate, and noteworthy deposits of gypsum. The rocks contain abundant fossils, including large oysters, echinoids (sea biscuits), clams, and snails, as well as shark teeth and the occasional remains of large reptiles, such as crocodiles, mosasaurs, and plesiosaurs. There are very few dinosaurs known from Arkansas. However, a spectacular dinosaur trackway in the southwestern part of the state provides evidence that they lived in the area.