Foraminiferal biostratigraphy and paleoenvironments of the Oligocene-Miocene carbonate succession in Campos Basin, southeastern Brazil

• Main Authors: BouDagher-Fadel, MK, Price, GD, Koutsoukos, EAM
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: MICROPALEONTOLOGY PRESS 2010
• Subjects: CONTINENTAL-MARGIN; EVOLUTION; ASSEMBLAGES; PALEOGENE; TETHYAN; SPAIN; RAMP; Planktonic foraminifera
• Online Access: http://discovery.ucl.ac.uk/1299581/

The present investigation of the Cenozoic carbonate succession of the Campos Basin, offshore southeastern Brazil, has resulted in a high resolution biostratigraphic profile of the region based on cores and cutting samples. In general, the studied carbonate successions evolved during three depositional stages: 1)In the Oligocene a warm period prevailed where temperature-sensitive organisms, such as larger benthic foraminifera, corals, algae and arthropods thrived in a reefal setting. Four different benthic foraminiferal biozones (BF1 - BF4) were defined based upon the occurrence of the following foraminiferal assemblages which were dominated by (BF1) lepidocyclinids, (BF2) miogypsinids, (BF3) Miogypsina-Amphistegina, and (BF4) Miogypsina and Heterostegina. These biozones, are equivalent to the P18-P22 planktonic foraminiferal biozones, and reflect temporal changes of environmental and ecological conditions associated with minor sea level fluctuation.2) The warm period continued through the early Miocene, where corals, bryozoans, rare planktonic foraminifera and larger benthic foraminifera thrived in clear agitated waters of a forereefal setting. This period was represented by two benthic foraminiferal zones, BF5 - BF6, equivalent to the N4-N7 planktonic foraminiferal biozones. Miogypsinids, Lepidocyclina and Heterostegina dominate BF5, while attached forms growing in a massive branching structure, such as Sporadotrema are prominent in BF6.3) The third depositional stage is reflected by a rapid deepening of the carbonate facies at the onset of the middle Miocene, coeval with a global warming event, the so-called mid-Miocene Climatic Maximum. This resulted in the replacement of the reefal organisms by pelagic sediments containing planktonic foraminifera. The planktonic foraminiferal biozones PF1 and PF2 are equivalent to N8-N12 planktonic foraminiferal biozones, and were present in all wells. This rapid sea level change is inferred to be related to a global warming event and related oceanographic changes.The high resolution depositional and biostratigraphic scheme put forward here for the Campos Basin will enable a more detailed understanding of the general regional evolution of the economically important Cenozoic carbonate facies that are found off the Atlantic margins of South America, the Caribbean and West Africa.