Biostratigraphical Analysis and Palaeoenvironmental Reconstruction of Cenomanian-Turonian Boundary in Côte d'Ivoire Onshore Sedimentary Basin, West Africa

Abstract

The microfauna studied in this work was provided by the interval 1350-1590m of an onshore oil well Tiemié 1, located about 70 km West of Abidjan,in northern Gulf of Guinea. The residues of 23 samples of drill cuttings washed with soapy water, dried and sorted, revealed fourteen of mainlyplanktonic foraminiferal species dominated by the Whiteinellids,Hedbergellids and Heterohelicids. The dominance of microplankton in thelower part of the interval (1390-1590 m) , combined with the total absence ofbenthic foraminifera, reflects an environment of external platform with athick water column probably responsible of reduced oxygenation over theseafloor. At the top (1350-1390 m), absence of any microfauna suggests ashallow shelf and on which a turbulent marine winnowing phenomenonwould have probably prohibited their accumulation. This assemblagecharacterizing Turonian-Cenomanian transition in many geographicalprovinces bordering Atlantic Ocean, was discussed at bothbiostratigraphical and palaeoenvironmental and palaeogeographic plans.