Black Belt (geological formation)

Black Belt is a physical geography term referring to a roughly crescent-shaped geological formation of dark fertile soil in the Southern United States. It is about 300 miles (480 km) long and up to 25 miles (40 km) wide in c. east–west orientation, mostly in central Alabama and northeast Mississippi.^[1][2]

During the Cretaceous period, about 145 to 66 million years ago, most of what are now the central plains and the Southeastern United States were covered by shallow seas. Tiny marine plankton grew in those seas, and their carbonate skeletons accumulated into massive chalk formations. That chalk eventually became a fertile soil, highly suitable for growing crops. The Black Belt arc was the shoreline of one of those seas, where large amounts of chalk had collected in the shallow waters.^[3]