3D gravity modelling of areas under the aptian lakes in the Jatobá basin and Tucano Norte sub-basin - Negra and Tonã hills.

Abstract

Due to structural similarities and the possibility of connection between the two Aptian paleolakes in the Jatobá Basin and the Tucano Norte Sub-basin in North-eastern Brazil, the influence of the architecture of the crystalline basement under these lacustrine sedimentary rocks was analysed using gravimetric data near the faulted edges of the basins where the paleolakes are located. The Negra (Jatobá Basin) and Tonã (Tucano Norte Sub-basin) Hills are mainly sedimentary deposits of Aptian age and are linked to the post-rift I tectonic sequence. Aiming at the study of reservoirs analogous to pre-salt reservoirs, the gravimetric data were processed and interpreted to define the structural framework of the basin regions around these hills. Depth maps and density models were generated that could be analysed from various 3D perspectives, and the behaviour of the crystalline basement below these sedimentary sequences was investigated. In addition to the identification of horsts and semi-grabens that influenced the current relief pattern, the modelling showed that the Aptian paleolake sedimentary rocks of the Negra Hill are in the Ibimirim Low, which is approximately 2,900 m deep, while in the Tonã Hill, the sedimentary rocks are in the Salgado do Melão Low, which is approximately 5,100 m deep.