Bioestratigrafia e inferências paleobatimétricas, com base em foraminíferos, do intervalo Paleógeno–Neógeno no norte da Bacia de Campos (poço Campos-01)

Abstract

-BIOSTRATIGRAPHY AND PALEOBATHYMETRIC INFERENCES BASED ON FORAMINIFERA OF THE PALEOGENE-NEOGENE INTERVAL FROM NORTHERN CAMPOS BASIN (CAMPOS-01 WELL). The micropaleontological analysis of a section of 1020 m (1760 m-2780 m) from the Campos-01 exploratory well, located at the Northern Campos Basin under 1338 m of water depth, provided a great diversity of foraminifera species recovered mostly from strata of Cenozoic age. The objective of this study is to recognize a biostratigraphic framework for the Paleogene-Neogene section crossed by the Campos-01 well, to identify unconformities in the sedimentary record, and to know paleoenvironmental characteristics of the interval in terms of paleobathymetry. For this study, 53 cutting samples were selected and the calcareous microfossils (planktic and benthic foraminifera) were analyzed both qualitatively and quantitatively. As a result of the observed stratigraphic distribution of planktic foraminifera species, the biozones P16 (uppermost Eocene), N4, N5?-N6?, N7, (lower Miocene), N8, N9, N10?-N13?, N14-N15 (middle-upper Miocene), N16 and N17 (upper Miocene), of Blow (1969), were recognized. The presence of two unconformities is suggested, representing biostratigraphical record breaks between the depth 2720 m and 2740 m (Paleocene-upper Eocene, middle part), and between the samples 2640 m and 2670 m (Oligocene). To the upper Eocene, the paleobathymetry was interpreted to have been outer neritic, which is supported by the reduction of the total abundance of foraminifera and the presence of a benthic foraminifera association typical of this environment. In the Miocene section, from the base to the top, it was noted that the percentage of planktic foraminifera corresponds to a trend of increasing paleodepth, indicating an increment of distance from the coast, with presence of genera and some species of benthic foraminifera that suggest the predominance of the upper bathyal paleobathymetry to this interval.Key words: Foraminifera, Cenozoic, Campos Basin, biostratigraphy.RESUMO -A análise micropaleontológica de uma seção de 1020 m (1760 m-2780 m) do poço exploratório Campos-01, localizado na porção norte da Bacia de Campos sob lâmina d´água de 1338 m, constatou uma grande diversidade de espécies de foraminíferos recuperados de estratos de idade majoritariamente cenozoica. O objetivo deste trabalho é reconhecer um zoneamento bioestratigráfico para essa seção do Paleógeno-Neógeno atravessada pelo poço, identificar eventuais discordâncias presentes no registro sedimentar, e fazer inferências paleoambientais para o intervalo em termos paleobatimétricos. Para isso, 53 amostras de calha foram selecionadas e os microfósseis calcários (foraminíferos planctônicos e bentônicos) presentes foram analisados qualitativa e quantitativamente. Como resultado da distribuição estratigráfica observada das espécies, foram reconhecidas as biozonas P16 (parte média do Eoceno superior), N4, N5?-N6?, N7 (Mioceno inferior), N8, N9, N10?-N13? (Mioceno médio), N14-N15 (Mioceno médio-superior), N...