Estudo palinoestratigráfico e de petrografia orgânica do Cretáceo inferior da Bacia do Recôncavo

Abstract

The present study was based on vertical variations analysis of the organic matter from 50 core samples collected from the well 9-FBA-61-BA, allowing better understanding of the Early Cretaceous of Reconcavo Basin palynological and palynofacies characteristics. Observations throughout combined light and blue light/UV fluorescence techniques, permitted to defined the section depositional time, and to distinguish four individual types of palynofacies, taking into account the variety and degree of preservation of organic matter.. Quantitative analysis of the organic content shows a predominance of allochthonous organic matter, represented by pollen, spores and phytoclasts on the base and top of the section; however the middle part is dominated by amorphous organic matter. On the other hand, the highest fluorescence was observed at the base and middle portion of the section suggesting a low oxidizing level at this sedimentation time. ICE data presents mature values ranging between 4.5 to 5.0 indicating that the deposits are in the oil generation window. The identified palynoflora and obtained lithological data suggests an exclusively continental paleoenvironment, composed by fluvial and deltaic - lake systems, in a warm and arid climate at the deposition time. Were identified 57 species of palynomorphs, including pollen, spores, algae and fungi. The detection of the Dicheiropollis etruscus and Aequitriradites spinulosus index species indicates these deposits belong to the Hauterivian - Barremian Vitreisporites pallidus and Dicheiropollis etruscus palynozones, respectively. This assemblage fits into those observed in the Brazilian northeastern basins and have the microfloristic assemblage characteristics that fit in to the Dicheiropollis Province (= WASA Province).