Palynological Analysis Of The St-5 And St -6 Wells, Offshore Tano Basin, South Western Ghana: Implications For Stratigraphy And Paleoenvironment

Abstract

Miospores and dinoflagellates recovered from sediments from the ST – 5 and ST – 6 wells, offshore Tano Basin, Western Ghana were studied in order to determine their ages, establish palynostratigraphy and determine environments of deposition. Based on First Appearance Datum (FAD) and (LAD) of marker palynomorphs, three (3) biozones were erected for miospores and dinoflagellates respectively. The characteristic taxa of each of the biozones have been discussed in detail. The three biozones correspond to an Albian-Cenomanian, Campanian-Maastrichtian and a Paleocene age respectively. There are no representatives of the Turonian/Santonian ages, thus suggesting the presence of an unconformity between the Albian–Cenomanian and Campanian- Maastrichtian sediments. The Albian–Cenomanian sediments are characterised by the presence of elaterate pollen with scarce dinoflagellates which is indicative of deposition in a marginal marine environment under a warm, arid/semi-arid climate. The Campanian–Maastrichtian sediments are characterized by typical Nypa species such as Proxapertites and Longapertites that thrived in a coastal mangrove environment under a hot tropical to sub-tropical climate. The dinoflagellates of the Campanian– Maastrichtian sediments indicate that deposition took place in a marginal marine to open marine environment. These conditions were deduced based on the variations in the relative abundance of peridiniacean to gonyaulacoid cysts. The peridiniacean assemblage observed in the Campanian–Maastrichtian sediments of the ST–5 and ST– 6 wells of the Tano basin is dominated by Andalusiella, Cerodinium, Senegalinium and Phelodinium. These species are the constituents of the tropical – subtropical Malloy suite of Lentin and Williams (1980). The miospore assemblage of the Albian– Cenomanian horizons shows elements that are typical of the Albian-Cenomanian Elaterate Province of Africa and South America. The Campanian – Maastrichtian miospore assemblage observed are also typical of the Senonian Palmae Province.