Origin of mid-cretaceous black shales in the benue through, Nigeria
Abstract Black and dark-gray laminated shales with large amounts of both terrestrial and marine organic material are common in upper Cenomanian to lower Santonian rocks of the Benue Trough. These shales were deposited during global mid-Cretaceous marine transgressions when widespread high organic carbon sedimentation took place. The Benue Trough in those times was the site of a shallow, density-stratified, anoxic epeiric sea with estuarine-type circulation. From this reservoir, nutrient-rich oxygen-depleted waters were fed into the northern parts of the South Atlantic Ocean.