Biostratigraphy Analysis of Mars Field Offshore, Dahomey Basin, Nigeria

Abstract

The biostratigraphic interpretation of the Mars Field, located offshore in the Dahomey Basin of western Nigeria, was conducted through a detailed analysis of index fossil species identified across three wells: MARS 1, MARS 3, and MARS 5. This study leverages the occurrence and distribution of key microfossils to establish a robust chronostratigraphic framework spanning the Late Cretaceous to Paleogene periods. The presence of Globanomalina daubjergensis indicates a Lower Paleocene age, while the dinoflagellate Dinogymnium acuminatum suggests a Danian age at depths ranging from approximately 6250’ to 8990’, marking the transition to Cretaceous strata at 8990’ (Berggren et al., 1995). Further, the occurrence of Globotruncana gansseri points to a Late Campanian to Upper Maastrichtian age at depths of 9080’–9420’, and Globotruncana aegyptiaca denotes a Coniacian age at around 10750’ (Bralower et al., 1995). Deeper intervals reveal an Albian age inferred from Callialasporites spp. at approximately 12400’, and the presence of Dicheiropollis etruscus at about 14660’ suggests a Barremian age, indicating the oldest strata penetrated in the study area (Adeigbe et al., 2013). These biozones, derived from foraminifera, palynomorphs, and calcareous nannofossils, correlate with regional unconformities and seismic markers, providing insights into the basin’s depositional history. The analysis highlights variations in microfossil abundance and diversity with depth, reflecting changes in paleoenvironmental conditions and sedimentological processes within the transform margin setting of the Dahomey Basin. This biostratigraphic framework not only refines the geological timeline of the Mars Field but also supports its potential significance for hydrocarbon exploration by delineating key stratigraphic intervals.