Abstract:Petroleum Source Rock Evaluation and Paleoenvironment of Gongila Formation, part of Gongola Basin Upper Benue Trough, Northeast Nigeria
ISA, MUHAMMED T., ATB University, Geology Programme P.M.B 0248, Bauchi, Nigeria
A geochemical and micropaleontological study of the argillaceous sequence of Cenomanian-Turonian Gongila Formation from a quarry site located at the Ashaka Cement Company, part of Gongola Basin of the Upper Benue Trough was carried out. The main objective of the study was to clarify the type, quantity and thermal maturity of the sedimentary organic matter as well as paleoenvironment of the Gongila Formation. The study involved the analysis of shale samples from the quarry site at different locations.
Petroleum source rock characterization was carried out using a combination of standard geochemical techniques including: Rock-Eval pyrolysis, soxhlet extraction and computerized gas chromatography/mass spectrometry of the saturated fractions of the extract for the composition and distribution of suitable hydrocarbon geochemical fossils. Microfossils and biomarker results were used to interpret the paleoenvironment.
The analytical data revealed the abundance of type III kerogen, with
low to intermediate organic rich matter of generally less than optimal
maturity status for petroleum generation. Pristane/phytane ratios and steranes
indicated marine precursors with high input of terrestrial organic matter.
The presence of a monospecific pyritized planktonic foraminiferal fauna
served as an indication of waning marine influence. The dominance of Heterohelix
with a reduced test size and absence of keel planktonic foraminifera is
a clear indication of shallow marina environment in the study area.
AAPG Search and Discovery Article #90931©1998 AAPG Foundation Grants-in-Aid