| Popis: |
ABSTARCT The concept of cyclic characterization of palynological records in a sedimentary sequence, referred to here as palynocycles, are connected to eustatic oscillations. Eustatic and climatic cycles are closely associated and are determined by variations in the coastal plant communities which are followed through pollen assemblages. Depositional systems have been found to correspond to phases of sea level oscillations, which in turn correlate with sequences or cycles of fossil pollen assemblages, palynocycles, and are driven by climatic cycles. The ecological communities and assemblages that were important in this concept are ferns, palms, mangroves, open forests and herbs. These formed the bases for relationship involving palynocycles, eustatic cycles and depositional (sequence stratigraphic) systems tracts. This paper presents the stratigraphic behaviours of depositional systems, based on controls of eustacy, subsidence and sediment supply at various scales and phases. Five wells from offshore Niger Delta Basin, Nigeria across the Eastern Thrust/Fold Belt and the Western Thrust Belt, were taken as case study for this work. These wells penetrated a total of seventeen (17) palynocycles presented as PCYL 1 to PCYL 17, dated from 17.7Ma to 0.8Ma and were correlated across the studied wells sections. Some missing intervals or sections and compressed cycles, corresponding to depositional cycles were identified. These may correspond to periods of erosion, forced regression or unfilled incised valleys during or after sediments deposition or stratigraphic condensation episodes, which could have been possible reservoir horizons or potential entrapment systems for hydrocarbon accumulations. This novel relationship approach is developed to advance better understanding of the depositional systems, enhance the development of new stratigraphic plays to search for subtle traps, which may have been bypassed and increase reservoir prospects in the Nigerian basins. Key words: Palynomorphs; palynocycles; eustacy: palynoflora; palaeoclimate; palaeoecology; bioevents; Miocene |
