Estruturas sedimentares microbianas em arenitos da Formação Sergi (Jurássico), Bacia do Recôncavo, Bahia, Brasil

Abstract

The bosedimentology is a new area of knowledge in geosciences which studies the influence of microbial organisms in sedimentological processes. Within this new area, there are more traditional studies in carbonate rocks, but more recently, a new focus on the genesis of certain structures in sedimentary sandstones and shales that occur from the precambrian to recent has opened new possibilities for studying biosedimentogy in terrigenous sediments and rocks. This study aims to identify the microbial influence in the genesis of some sedimentary structures in eolian sandstones of Sergi Formation, Jurassic of Recôncavo basin. Several structures have been recognized in this formation, similar to those which has been identified in the literature as elephant skin, pinnacles, wrinkle marks, exfoliating sand laminae and domal buildups, and microscopic structures such as laminations with peculiar spatial arrangement of grains and heavy mineral concentration, all which are associated with microbial genesis. The correct diagnosis of these structures not only increases the descriptive capacity of sedimentary lithofacies for the Sergi Formation, as well as the paleoenvironmental interpretative ability of the formation, through the possibility of recognition of humid aeolian depositional systems (paleoenvironments of interdune / sand sheet), that had not yet been hypothesized in the literature of the basin