Paleontology and geologyThere was no tectonic activity in Arkansas during the Devonian. Most Devonian-age rocks in the state are either deeply buried or were removed by erosion. However, the small exposures of fossil-poor sandstone, shale, and chert in northern Arkansas show us that the sea covered the state during this time interval. In the Ouachita Mountains of central Arkansas, there are deposits of chert and shale that form the lower part of a rock formation known as the Arkansas Novaculite. Much of the chert was formed from tiny, fossilized skeletal elements of sponges and microorganisms that lived in the sea; some may be from volcanic ash. This chert was later metamorphosed into the rock called novaculite, pieces of which are used today as whetstones for sharpening knives |