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Tracing marine conditions in the Ipubi Black Shales, Araripe Basin, NE Brazil: An approach by chemical elements contents

2022; Elsevier BV; Volume: 116; Linguagem: Inglês

10.1016/j.jsames.2022.103880

1873-0647

Thales Lúcio, Willian Alexandre Lima de Moura, Gabriel C.S. Albuquerque, João Adauto de Souza Neto,

Geochemistry and Geologic Mapping

The aim of this study was to test the hypothesis of a marine influence during the Ipubi Formation deposition (late Barremian-early Aptian age) in the Araripe Basin northeast, Brazil. For this, it was utilized a representative section in the southernmost part of the basin. The section is composed of mudstone, shale-marl laminae, and black shale rocks. The organic matter in the samples is 3.27 and 18.28%; whereas the CaCO3 present values in order of 23.42–66.46%. The geochemical proxies, such as V/Ni, Ni/V (V/(V + Ni) Fe/Al suggest depositional condition from sub-oxic to anoxic. The Sr/Ba and Rb/Sr data range from brackisch to hypersaline waters. The ingression of a seawater in the Araripe Basin triggered the organic matter accumulation, as well as the trace metals mobility in the bottom surface. Our data suggests that the Ipubi Formation represents the boundary of transitional to marine conditions in the Araripe Basin, and the basin owned as a silled basin when the increase of relative sea level made it possible the water inlet in the basin.