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 mainly
planktonic foraminiferal species dominated by the Whiteinellids,
Hedbergellids and Heterohelicids. The dominance of microplankton in the
lower part of the interval (1390-1590 m) , combined with the total absence of
benthic foraminifera, reflects an environment of external platform with a
thick water column probably responsible of reduced oxygenation over the
seafloor. At the top (1350-1390 m), absence of any microfauna suggests a
shallow shelf and on which a turbulent marine winnowing phenomenon
would have probably prohibited their accumulation. This assemblage
characterizing Turonian-Cenomanian transition in many geographical
provinces bordering Atlantic Ocean, was discussed at both
biostratigraphical and palaeoenvironmental and palaeogeographic plans.