Abstract: Albian to Cenomanian Foraminiferal Zones of Angola (Cabinda), West Africa: Relationships to Chronostratigraphy, Facies, and Morphogroups
Thomas W. Dignes
For the offshore Cretaceous of Angola (Cabinda), the late Albian Trocholina silvai and early and middle Cenomanian Textularia praelonga-Cribratina foraminiferal zones of Sieglie and Baker (1982) are represented by time-transgressive assemblages which show strong sedimentary facies and microhabitat preferences. The calcareous benthic foraminifer Trocholina silvai (Petri, 1962) is closely associated with the late Albian Pinda Limestone and related coarse-grained bioclastics and oolites which have been interpreted as carbonate shoal and patch reef buildups. The Textularia praelonga-Cribratina zone occurs within the Albian when carbonate rock types are not present in sediments of that age. The foraminiferal fauna of this mixed siliciclastic facies is almost exclusively arenaceous; its dominant species reflect quite different inferred modes of life from those of the Trocholina silvai zone. The presence of forms with a suspension-feeding lifestyle in a predominantly siliciclastic facies suggests a generalized model containing the following elements: mobile, conical grazers of the Tro holina silvai zone, quite capable of holding fast to the substrate when necessary, characterize higher energy, carbonate subenvironments, while sessile, tubular and arborescent suspension feeders of the Textularia praelonga-Cribratina zone typify lower energy siliciclastic depositional settings in the Albian.
AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela