Sequence Stratigraphic Analysis of Siliciclastic Sediments from the Agbada Formation in the Niger Delta: A Well Log – Foraminifera Approach

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Sequence Stratigraphic Analysis of Siliciclastic Sediments from the Agbada Formation in the Niger Delta: A Well Log – Foraminifera Approach

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Abstract

Well log - foraminiferal sequence stratigraphic studies was carried out on eighty (80) ditch cutting samples and well logs obtained from two exploration wells (well C and F) located in the Northern Depobelt of the Tertiary Niger Delta to determine the chronostratigraphic framework and sedimentary facies for the study well. This was achieved based on the use of standard micropaleontological sample preparation procedures and the analysis and interpretation of the litho-facies, well log patterns and foraminifera biofacies assemblages that characterized the study wells. Detailed lithologic analysis indicates that the sediments penetrated by the study wells belong to the Agbada Formation of the Tertiary Niger Delta. A total of eighty four (84) foraminifera species were recovered from the study wells consisting of thirty (30) genera, eighteen (18) families and three (3) suborders with a total foraminifera count of one thousand, eight hundred and seventy two (1872) comprising twenty four (24) planktic and one thousand, eight hundred and forty eight (1848) benthic forms respectively. The planktic and benthic foraminifera recovered from the Agbada Formation are transitional in character between the typical Late Eocene (P16/17) and the Early Oligocene (P18/19) epoch and therefore, indicate the transition between Priabonian age and Rupelian age. Sequence stratigraphic analysis of well C reveals only one Sequence Boundary (SB) dated ?35.4Ma at 2560m. Three systems tracts viz: one (1) Lowstand Systems Tract (LST), one (1) Highstand Systems Tract (HST) and one (1) Transgressive Systems Tract (TST) were also identified within two depositional sequences (SQ 1 and SQ 2). Sequence stratigraphic analysis of well F on the other hand shows the presence of three (3) Maximum Flooding Surfaces (MFSs); MFS1 dated 36.8Ma at 2720m, MFS 2 dated 35.9Ma at 2520m, and MFS 3 dated 34.0Ma at 2360m as well as four (4) Sequence Boundaries (SBs), SB 1 dated ?37.3Ma at 2900m, SB 2 dated ?36.3Ma at 2560m, SB 3 dated ?35.4Ma at 2400m and SB 4 dated ?33.3Ma at 2240m. Ten (10) systems tracts viz: three (3) Lowstand Systems Tracts (LST), three (3)Transgressive Systems Tracts (TST) and four (4) Highstand Systems tracts (HST) were identified within five depositional sequences (SQ 1, SQ 2, SQ 3, SQ 4 and SQ 5). The SB identified and dated ?35.4Ma in well C correlates well with SB 3 identified and dated ?35.4ma in well F.


Publication Info:

Author: Ukpong, A.J. and Ekhalialu, O.M.

Volume: 57

Issue: September

Published By: Journal of Mining and Geology, 2024-09-01

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