Paleontology and geology
The Devonian is not well represented in Alabama rocks, as at least some of the state was above sea level and subject to erosion. However, a stretch of Devonian rocks called the Frog Mountain Sandstone occurs in eastern Alabama. Formed nearshore in a marine environment, these rocks are reported to contain the first fragmentary traces of land plants in Alabama. Dark-colored marine rocks in northern Alabama (known as the Chattanooga Shale) show that the sea covering most of the state in the Late Devonian contained large areas of deeper, oxygen-poor water. Few organisms could tolerate these conditions. Fossils from these rocks are limited primarily to plant fragments and the remains of animals that swam above the deep, oxygen-starved waters.