Palynofacies analysis and depositional environments of Upper Cretaceous sediments in the ST‐9H well, offshore South Tano Basin, Western Ghana

Abstract

Palynofacies analyses were carried out on 43 cutting samples from the ST 9H well in the Tano Basin, with the view of reconstructing the palaeoenvironment of the Upper Cretaceous sediments in the well. The stratigraphic distribution of the palynofacies assemblages defined four palynofacies units. Palynofacies PA reflects deposition in near shore/shallow marine (inner neritic) environment under distal dysoxic‐anoxic shelf condition. Palynofacies PB was deposited in an inner–middle neritic environment under mud‐dominated oxic shelf conditions, Palynofacies PC in an open marine (outer neritic) environment under distal suboxic‐anoxic basin conditions, and Palynofacies PD in a proximal–marginal marine environment under dysoxic‐anoxic basin conditions. These palynofacies assemblages (PA–PD) are characterized by kerogen types II (oil prone), III‐IV (gas prone), II > I (oil prone), and III (gas prone), respectively. Marker dinoflagellate and miospore assemblages recovered from the sediments –are indicative of a Campanian–Maastrichtian age. The palaeofloral association and the perideanacean dinocysts assemblage are typical of Senonian Palme Province and the Malloy suite, respectively. These assemblages are indicative of a warm and humid tropical‐subtropical climatic condition.