Age and palaeoenvironments of the Manacapuru Formation, Presidente Figueiredo (AM) region, Lochkovian of the Amazonas Basin

Abstract

The Manacapuru Formation, Amazonas Basin, outcrops on the margins of a highway in the region of Presidente Figueiredo, state of Amazonas. A systematic palynological and a lithofaciological analysis was carried out aiming to contribute to the paleoenvironmental understanding of the Manacapuru Formation and its respective age. The present work uses the analysis of the chitinozoan for biostratigraphic purposes as a tool. A total of 27 samples were collected in which an assemblage of lower Lochkovian can be recognized, whose characteristic species are Angochitina filosa, Cingulochitina ervensis, Lagenochitina navicula, and Pterochitina megavelata. It was possible to identify an intense reworking in the exposure, evidenced by the presence of paleofaunas ranging from Ludfordian to Pridolian, which may be associated to the constant storm events that reached the shelf. The lithofaciological analysis allowed the recognition of 6 predominantly muddy sedimentary lithofacies with sandy intercalations that suggest deposition in an offshore region inserted in a shallow marine shelf and influenced by storms.