Paleontology and geology
There was no tectonic activity in Arkansas during the Cambrian, and a sea covered the entire state. Cambrian-age rocks consist of black shales interbedded with limestones. The sediments that formed these rocks were deposited in a relatively deep marine setting and contain numerous trilobite fossils. Most Cambrian rocks in the state are below the surface; however, there are small exposures of Cambrian rocks in the Ouachita Mountains in the west central part of the state. The small extent of these exposures prohibits them from being displayed on this map.