Sedimentology, geochemistry and paleoenvironmental reconstruction of the Cretaceous Yolde formation from Yola Sub-basin, Northern Benue Trough, NE Nigeria

Abstract

Sedimentology, organic and inorganic geochemical studies were applied on sediments of the Cretaceous Yolde formation from Yola Sub-basin, Northern Benue Trough, northeastern Nigeria with an attempt to determine the sedimentary facies, paleo-redox condition and to re-construct the palaeo-depositional environments. Eight (8) facies were identified on the basis of lithology, grain size, ichnofossils/degree of bioturbation and sedimentary structures. These facies constitute four facies associations; the FA-1 (offshore marine), FA-2 (offshore transition to lower shoreface), FA-3 (middle shoreface) and FA-4 (upper shoreface). The succession of these facies associations indicates storm and wave influenced offshore/shoreface depositional environments for the formation. Molecular organic geochemical investigation suggests deposition under sub-oxic marine environment with major contribution of phytoplankton, bacteria and minor amount of terrigenous organic matter. XRD mineralogical assessment, and major and trace elements geochemistry revealed that the Yolde formation sediments were sourced from continental areas of passive continental margin setting and deposited in semiarid climate under suboxic shallow marine conditions related to the first marine transgression that occurred in the Benue Trough during the Late Cretaceous period.