Análise bioestratigráfica de foraminíferos planctônicos de quatro testemunhos do Complexo de Lobos Almirante Câmara, Bacia de Campos

Abstract

The Almirante Câmara lobe complex is located in the northeastern Campos Basin, at the southeastern Brazilian continental margin. This complex is an excellent analogue to the Carapebus Formation, where are the major hydrocarbon reserves from the post-salt interval of this basin. The objective of this work is to contribute to the existing knowledge of this lobe complex through micropaleontological analysis based on planktonic foraminifers from four piston cores, aiming to estimate the age of the sand beds deposition and to propose a hypothesis for the difference among the biozones present in each core and their expected thickness. A total of 39 samples were collected from the piston cores, prepared according to the standard methodology for Quaternary calcareous microfossils, and about 300 tests of planktonic foraminifers were taxonomically identified per sample. In the piston cores LAC 18, LAC 22 and LAC 23 were recognized the Biozone Z and the subzones Y1A and Y1B. In the piston core LAC 19 were identified the Biozone Z, the Subzone Y1 and an indication of the presence of the Biozone X at the base of the piston core. The presence of the Biozone X was not expected in the piston core LAC 19, since it is only 1.23 m long and seismic analysis done by previous works indicated that, at the site where it was collected, the thickness of the Biozone Y should be between 10 m and 20 m. Two hypothesis are considered for this difference. The first is erosion caused by the proximity of this piston core with one of the main deposition channels of the lobes. Other possibility is that of erosion caused by high-energy deep water currents, especially during the Last Glacial Maximum.