Sedimentary supply to deep marine sandstone reservoir in Upper Cretaceous of Sergipe-Alagoas Basin, Northeast Brazil - Calumbi Formation

Abstract

Palaeogeographic and provenance studies can be important tools for assessing the volumes of sediment accumulated on the continental shelf (bypass areas) serving as a supply of material for the sedimentation in deep water, transported by landslides in the slope area or turbidity flows in the abyssal plains. The thickness and quality of the sandstone reservoirs deposited in deep waters show up strongly dependent on the conditions of these sedimentary contributions as well as the extension of the platform on which the sediments was originate been stored. The study of outcrops related to corresponding offshore deposits can be significant in this type of analysis. The objective of this paper is contribute to interpretations about the outcropping onshore portion of the Calumbi Formation, connecting the collected and interpreted data with the quality of the reservoirs in the offshore of the Sergipe Sub-Basin. The Sergipe-Alagoas Basin is located in the northeastern part of the Brazilian continental margin, being subdivided in 5 stages according to its tectono-sedimentary evolution: sineclisis, pre-rift, rift, post-rift, transitional and drift, the last one is related to deposition of the Calumbi Formation. The continental shelf and the deep waters are the prevailing depositional environments in the Calumbi Formation, being the shelf dominated by storms and waves and the deep waters dominated by gravity flows. This study include outcrops from the Campanian-Santonian section of the Calumbi Formation described in the field and where was realized a petrological analysis. The stratigraphical correlation between outcrops and subsurface data have made possible to draw interesting conclusions about the shelf sands in bypass situation to the deep water turbidites. A litoraneous and a shelf environment represent the more proximal sedimentation of the Calumbi Formation on the Upper Cretaceous found in this study. Their palaeogeographic position and the composition of the sandstones in these deposits give important contribution to the palaeogeographic reconstrution at that time slice. The main impact of this studies is the identification of the palaeogeographic situations favorable to ocurrence of large turbidites deposits.

AAPG Datapages/Search and Discovery Article #90226 © 2015 European Regional Conference and Exhibition, Lisbon, Portugal, May 18-19, 2015