Preece, Rachel Clare; (1999) The physiological response of equatorial Neogene bathyal benthic foraminifera to low oxygen conditions. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

A comprehensive taxonomic evaluation of equatorial Neogene bathyal benthic foraminifera is presented for the first time. Two wells from offshore Cabinda, West Africa, are examined. A diverse Miocene benthic foraminiferal fauna is described and illustrated, significant affinities to Venezuelan Agua Salada Fauna type material are observed. Paleoecological zonation and correlation provide original data on previously proprietary material. Palaeoenvironmental proxies and faunal data validate a periodic northward oscillation of the Benguela oceanographic system during the late early Miocene. Morphogroup analysis in conjunction with contemporaneous Total Organic Carbon data provide evidence for a dynamic shift in assemblage parameters with respect to palaeoenvironmental pressures. Taxonomic comparison of Agua Salada Fauna type material from Eastern Falcon, Venezuela, with previous records reveal additional taxa in this study. These are described and illustrated. The benthic foraminiferal faunal succession records a high productivity period and the development of an Oxygen Minimum Zone during the late Serravallian to early Tortonian. This is coincident with the initial shoaling of the Isthmus of Panama and associated bottom water restriction. Provincialisation amongst elements of the agglutinated foraminiferal assemblage between the Venezuelan and African localities is apparent. The Alveovalvulinidae and Liebusellinae of Venezuela are paleoecologically replaced by the Eggerellininae and Textulariinae offshore Cabinda. Similarly, the genus Popovia at the Venezuelan locality replaces morphologically similar Pavonitinacea common to Cabinda. Members of the Cyclamminidae are observed to follow a trend towards greater internal complexity with time at both the Venezuelan and Cabindan sites. In both cases this is coincident with the development of Oxygen Minimum Zone conditions.

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