--> ABSTRACT: Foraminiferal Biofacies Calibration of Neogene Depositional Systems, Eastern Niger Delta, by B. K. Rodgers, J. M. Armentrout, R. B. Bloch, L. B. Fearn, and M. Sonuga; #91021 (2010)

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Foraminiferal Biofacies Calibration of Neogene Depositional Systems, Eastern Niger Delta 

RODGERS, B. K., J. M. ARMENTROUT, R. B. BLOCH, L. B. FEARN,  and MARIE SONUGA

Biofacies mapping along seismically defined surfaces within twelve Neogene stratigraphic sequences of the of the eastern Niger delta has related paleobathymetry to seismic geometries. Using well data, maps were prepared for each of four surfaces: near base and near top of lowstand, maximum flooding surface, and upper highstand. Overlays of biofacies maps on seismic facies maps of the same sequence surface helped to distinguish wave dominated from gravity flow dominated sandstone reservoirs.

Foraminiferal biofacies ranged from paralic to upper bathyal. Biofacies patterns on each surface generally paralleled shelf edges mapped from seismic inflection points. However, biofacies mapping also provided criteria for extending shelf edges where seismic data was inconclusive. The inferred water depth at the seismic shelf edge inflection is not constant. In two different sequences where lowstand clinoforms are well developed, the seismic shelf edge inflection approximates the middle to outer neritic boundary in one and the outer neritic to upper bathyal boundary in the other. In one lowstand systems tract, the clinoform shelf edge is near the outer neritic-upper bathyal boundary in an area with well developed clinoforms and within the middle neritic in another area without clinoforms. Seaward excursions of shallow water biofacies at the top of lowstand system tracts indicate areas of rapid progradation and correlate with thick sands. 

AAPG Search and Discovery Article #91021©1997 AAPG Annual Convention, Dallas, Texas.