Abstract
: Biostratigraphic study of Well DX has yielded Cretaceous miospores and dinoflagellates cysts which heightened the recognition of sequence boundaries (SB), Maximum Flooding Surfaces (MFS) and associated Systems Tracts. Five maximum flooding surfaces between 95.6 Ma and 89.0 Ma, four sequence boundaries between 96.4 Ma and 93.0 Ma and threedepositional sequences were identified with varying average thicknesses of sediments interpreted from the gamma ray log and biostratigraphic data. The threedepositional sequences interpreted are -depositional sequence I (96.4 Ma - 95.4 Ma) (8240 ft. - 8120 ft.), depositional sequence II (95.4 Ma - 94.0 Ma) (8120 ft. - 7850 ft.) and depositionalsequence III (94.0 Ma - 93.0 Ma) (7850 ft. - 7550 ft.). All the depositional sequences fall within the third order cycle. The age of the well was attempted based on the presence of some selected marker fossils - Ephedripites spp., Classopollis spp., Spiniferites spp., Cyclonephelium distinctum, Cyclonephelium vannophorum, Subtilisphaera spp., Eucomiidites spp., Triorites africaensis, Odontochitina costata and Droseridites senonicus recovered from the studied intervals and was dated Albian - Santonian. The Sequence stratigraphic interpretations are useful in further deepening the knowledge of thesubsurface geology of the studiedwell in Gongola Sub Basin, Upper Benue Trough of Nigeria.Keywords: Sequence Boundary, Maximum Flooding Surface, System tracts, Depositional sequence
Highlights
The studied well was conducted in the Gongola Basin which forms part of the Upper Benue Trough
Sequence stratigraphy develops as an aspect of stratigraphy that subdivides rock record using a succession of depositional sequences defined as a relatively conformable succession of genetically related strata bounded by unconformities or their correlative conformities
Sequence can be divided into a systems tract and further subdivided into Lowstand Systems Tract (LST), Transgressive Systems Tract (TST) and Highstand Systems Tract (HST), each having a predictable stratigraphic order, shapes and contents
Summary
The studied well was conducted in the Gongola Basin which forms part of the Upper Benue Trough. It has an estimated area of 27,390.25 km and lies between longitude 10o 42’ 43.8’’E and Latitude 10o 07’03.9’’ N. The stratigraphic succession in the northern segment of the Benue Trough is entirely Cretaceous and starts from the very extensive continental Bima Formation which directly overlies the basement complex. The Kerri-Kerri Formation lies unconformably on the folded Cretaceous sedimentations of Paleocene (Tertiary) age.
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