Sedimentology and stratigraphic development of sandy members of Pindiga formation, GONGOLA SUB-BASIN, northern Benue trough, Nigeria: A mixed wave, tide and fluvially influenced coastal system

摘要

This paper documents the detailed sedimentology and stratigraphic evolution of the Sandy members of the Pindiga Formation. Good understanding of this succession is relevant to resource exploration and exploitation in the frontier Gongola Sub-basin of the Northern Benue Trough and similar Cretaceous strata in general. Detailed facies analysis based on examination of twelve well exposed outcrops revealed four facies successions. Field relations show that the deposits are stratigraphically partitioned by a disconformity surface into two parts. The lower part consists of regressive wave-storm dominated deltaic and wave-storm dominated offshore to nearshore facies successions, while the upper part comprises of transgressive wave dominated estuary and tide dominated estuary successions. Fourteen facies were identified and organized into nine facies associations. Field observations show that the upper boundary of the Sandy members is an angular unconformity represented by the development of a thick paleosol unit below the Fika Shale. Conversely, the lower boundary is transitional. Contrary to earlier fluvial and coastal to littoral interpretation of the Sandy members, this work demonstrates that marine processes were important for facies development. It is shown that an integration of detailed facies and ichnological analyses is valuable in determining robust paleoenvimnmental interpretations of sedimentary successions.