The biostratigraphic framework of CSDP-003 well, Central Swamp Depobelt, Niger Delta, Nigeria

摘要

The biostratigraphic framework of CSDP-003 well, Central Swamp Depobelt was investigated to establish the stratigraphic sequences penetrated in the well and the age of the sequences based on calcareous nannofossils recovered. The study was carried out with 138 ditch cuttings from the well and was prepared with the standard simple smear-slide technique of calcareous nannofossil sample preparatory method. The slides produced from the samples were viewed and 31 calcareous nannofossils were recovered which were used to characterize the well into 3 NN zones, following base (Last Downhole Occurrence/First Appearance Datum (LDO/FAD) of Sphenolithus heteromorphus, Top (First Downhole Occurrence/Last Appearance Datum (FDO/LAD) of Helicosphaera ampliaperta, and Top (First Downhole Occurrence/Last Appearance Datum (FDO/LAD) of Sphenolithus heteromorphus corresponding to NN3, NN4, and NN5 biozones respectively. Three Maximum Flooding Surfaces (MFS) and two Sequence Boundaries (SB) were delineated and their ages were determined using the diagnostic forms. MFS 17.40Ma was noted with high abundance and diversity of calcareous nannofossils and explosive events (ACME) of Sphenolithus heteromorphus, Helicosphaera ampliaperta, Sphenolithus moriformis, and Helicosphaera cartari at 2804m within NN4 zone, MFS 15.90Ma was identified based on abundance and diversity peak at 2429m corresponding to explosive events (ACME) of Sphenolithus heteromorphus, and Sphenolithus moriformis within NN4 zone while MFS 15.00Ma was delineated based on abundance and diversity peak with Helicosphaera cartari ACME at 1957m. The Sequence Boundary's SB 16.5 Ma (latest Burdigalian) and SB 15.5 Ma (Langhian) were delineated based on rare to non-occurrence of calcareous nannofossil at 2530m and 2228m respectively.