Albian Palynology of the Pinda Formation, Cabinda, Angola: Time and Environmentally Controlled Approach to a Palynological Zonation
Sheldon N. Nelson
HES, Chevron Energy Technology Company, San Ramon, CA
The Cabinda Pinda trend, with an estimated five billion barrels of oil in place, is a major oil producing reservoir in west Africa.
The Albian age Pinda Formation, found offshore Cabinda, Angola, was deposited under primarily nearshore, restricted marine conditions. A zonation of the Albian palynological assemblages found in the Pinda is presented: consisting of nine subdivisions based on time and environmentally controlled parameters. Assemblage zones are reflective of transgressive lowstand units, highstand units, regressive and progradational units, and maximum flooding surfaces.
The upper portion of the Pinda Formation is zoned primarily on the diagnostic, sequential “flooding” events of the marine taxa Subtilisphaera spp. and Leiosphaeridium spp., and the presence and relative abundance of Cyclonephelium spp., Schizea certa, Striatricolpites “takulaensis”, Elaterocolpites castelanii, Elaterosporites klaszii, and Afropollis jardinus. The lower portion of the Pinda is characterized and zoned based principally on the relative abundance of Trichodinium spp., and secondarily on the first downhole presence of Batiacasphaera sp., Elaterosporites verrucatus, Elaterosporites protensus, Muderongia sp., Diconodinium sp. and vessiculate pollen.
The overlying Cenomanian age sediment in Cabinda (Vermelha Formation) is generally characterized by a more open marine palynomorph assemblage, dominated by Subtilisphaera spp., Coronifera oceanica, Cyclonephelium spp., Florentinia radiculata, Cyclonephelium membraniphorum, and Dinopterygium tuberculatum, with the diagnostic presence and abundance of Classopollis brasiliensis. The top Albian is locally defined by the initial downhole occurrence of Afropollis jardinus and Schizea certa. The underlying Aptian age unit is characteristically terrestrial.
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