Sequence Stratigraphic Evaluation of Sediments Domicile in Day Field Located in the Onshore Central Swamp Depobelt of the Niger Delta, Nigeria

This study employs the tool of sequence stratigraphy to evaluate Day Field, in the Onshore Niger Delta of Nigeria for hydrocarbon predictions using six (6) well logs displayed at standard scales to enhance log trends for lithologic and stratal package delineation. The identified key stratigraphic bounding surfaces were tied to well-defined palynological (P) zone and foraminiferal (F) zones with the aid of the biostratigraphic data and calibrated using the Niger Delta Chronostratigraphic chart. Five (5) MFSs (34.0, 33.0, 31.3, 28.1, and 26.2 Ma) and six (6) SBs (35.4, 33.3, 32.4, 29.3, 27.3, and 24.9 Ma) were delineated. The stratigraphic surfaces were matched with the palynological (P480– P580) and foraminiferal zones (P20/N1–P22/N3) encountered. The results indicate that the study area is of Late Eocene to Late Oligocene age (26.2–35.9 Ma). The key stratigraphic surfaces also reflect a series of relative sea-level falls (regressive episodes) and sea-level rises (transgressive episodes) that are regionally extensive and correlated across the wells. Five sequences (SEQ1–SEQ5) were recognized, SEQ1 and SEQ5 comprising three system tracts (LST, TST, and HST) revealing four third-order depositional sequences (classified as type 1 sequence), while SEQ2-SEQ4 comprises two system tracts (TST and HST). Two depositional environments were interpreted from the log trends; the Fluvial (shoreface) and Tidal environments. The hydrocarbon exploration prospects identified are the sand units of the LST and HST combining with the shale units of the TST offering good reservoir and seal/source rocks respectively

Field and Sedimentological Studies of Nataco-Banda Sediments of Lokoja Formation, Southern Bida Basin, Nigeria: Implication for Depositional Environment

The study area falls within the Lokoja Formation of the Southern Bida Basin. The objective of this study was to evaluate the field characteristics and sedimentological parameters of depositional environment of the Nataco-Banda Sediments of Lokoja Formation, Southern Bida Basin, Nigeria using appropriate techniques such as granulometric and pebble morphometric analysis. Field studies revealed a repeated alternating sequence of conglomeratic and pebbly to coarse-grained sandstone and overbank fine sediment that is indicative of a braided fluvial source while the presence of crossbedding is suggestive of tidal influence. The morphometric analysis shows a fluvial setting where pebbles plot in the river area than the beach area. Environmental discrimination formulae for Y1, Y2 and Y3 indicated the dominance of Beach and Shallow agitated marine in both Y1 and Y2, respectively, while the almost equal percentage values of Y3 in both fluvial and shallow marine settings are highly suggestive of a shallow marine environment that is largely influenced by fluvial deposition

Sedimentary Facies and Palynological Studies of Ajali Sandstones Formation Outcropping in Idah, Northern Anambra Basin, Nigeria

The paleo-depositional environment of the Maastrichtian Ajali Sandstone Formation of the Anambra Basin has remained controversial as numerous studies have inferred differing origins of the sedimentary unit. This study presents analytical evidence on the depositional environment of the Formation based on its lithofacies and palynological characteristics by evaluating its depositional mechanisms, paleoclimate, and depositional environment. Microfacies and palynological studies were carried out on sediment samples from outcrop sections along the western flank of River Niger. Nine lithofacies and two facies’ associations were identified with characteristics such as fining and coarsening upward sequences, which indicate subtidal channel and sandflat deposition in a shallow marine environment. Palynological studies reveal the occurrence of significant land-derived palynomorphs such as Tricolporopollenites sp., Cyathidites sp., Distaverrusporites simples, Cingulatisporites ornatus, Psilatricolporites Crassus, Longapertites sp. with freshwater algae Botryococcus braunii of Maastrichtian age. These results confirm that the sediments of the Ajali Sandstone are of a marginal marine system fed by continental facies. These facies have been reworked by tidal processes characteristic of an inner neritic environment deposited during regressive episodes