The role of accommodation/sediment supply regime/basin morphology in predicting coastal depositional style: A sequence stratigraphic framework approach for selected deep wells of oligocene-miocene sediments of coastal swamps in Niger Delta

摘要

The Oligocene – Miocene sediments of Selected Deep wells in Niger Delta is represented by marine strata that were deposited in either fluvial- wave – or tide – influenced environments. The wire line log used allows the succession to be broken down into 5 sequences and system tracts that aided in the interpretation. The changes in depositional style as observed within the sequence stratigraphic framework are as a result of fluctuations in relative sea level, variations in the effectiveness of wave and fluvial energy, basin morphology and accommodation/Sediment supply regime. The study shows that during high accommodation space/low sediment supply, the trangressive systems tract, late lowstand systems tract and early highstand systems tract, which corresponds to low sedimentation rate, will have its dominant Depositional style determined by the underlying basin morphology. During period of low accommodation space and high sediment supply regime, which corresponds to late highstand systems tract, falling stage systems tract and early lowstand systems tract, the rate of sedimentation will exceed the available accommodation space. Thus, the underlying basin geometry will have no effect on the depositional style; this will result in the coastline exposed to direct effect of wave energy. From the Predictive model used in the study, which shows the influence of basin morphology, wave and fluvial energy effectiveness, low and high Accommodation/Sediment supply regime, 2 major Depositional style with highest preservative potential and their second preservative potential were noted.