Sedimentology and sequence stratigraphy of fluvial-lacustrine, Mesozoic, Abu Gabra and Bentiu formations, Muglad rift basin, Sudan

Abstract

The study objective is to characterize the facies, depositional environments and the sequence stratigraphy of Abu Gabra and Bentiu formations in the Muglad rift basin, Sudan. Lithofacies analysis revealed six lithofacies associations in Abu Gabra formation and four lithofacies associations in Bentiu formation. Abu Gabra formation is interpreted to be deposited within a lacustrine system and is composed of fluvial, shallow and deep lacustrine and fluvio-deltaic environments. Bentiu formation is interpreted to be deposited within a fluvial system and composed of braided, meandering and minor shallow lacustrine environments. Different orders of sequences were recognized, and these are second order super sequence, second, third and fourth order sequences. Both Abu Gabra and Bentiu formations are second order sequences. Each of Abu Gabra (17 Ma) and Bentiu (38 Ma) is a second order sequence. System tracts (LST, TST and HST) were also recognized. More over, seismic facies analysis revealed five rifting phases, starting from rift initiation to late post-rift. Both allocyclic and autocyclic factors have controlled the stratigraphic sequence development.