Reassessing the Depositional Environment of the Amasiri Sandstone in Akpoha within the Turonian Eze-Aku Group through Integrated Geological Analyses

Abstract

The depositional environment of the Amasiri Sandstone within the Turonian Eze-Aku Group in the Lower Benue Trough, southeastern Nigeria, has remained controversial due to its lithological variability and complex facies architecture. This study combines detailed sedimentological observations derived from outcrop analysis, petrographic studies, and paleocurrent measurements to re-evaluate the depositional conditions and provenance of the Amasiri sandstone. Petrographic data indicate arkosic sandstone compositions, pointing toward potential source areas, including the Oban Massif, Calabar Flank, and the basement complexes around Ogoja. Analysis of sedimentological features and paleocurrent patterns supports a depositional scenario dominated by relatively dense gravity-driven sediment flows entering a marine or lagoonal basin. These findings suggest deposition within a hyperpycnal deltaic environment, providing a better understanding of the sedimentary processes that controlled the formation of the Amasiri Sandstone.