Ostracods from the Barbalha and Crato formations, Aptian of the Araripe Basin, northeast Brazil.

Ostracods have been widely used for biostratigraphic and paleoenvironmental purposes for the Lower Cretaceous deposits of northeastern interior Brazilian basins. The ostracods of the Romualdo and Crato formations of the Araripe Basin are particularly well known; however, the ones from the underlying Barbalha Formation are less so. Here we report 10 ostracod species, of which three are new, obtained from 56 samples of the Barbalha and Crato formations collected from boreholes 1PS-06-CE and 1PS-10-CE: Candonopsis? alagoensis Tomé et al., 2014, Brasacypris subovatum Do Carmo et al., 2013, Damonella medialtis sp. nov., Cypridea araripensis Silva, 1978, Pattersoncypris cf. P. angulata (Krömmelbein & Weber, 1971), Pattersoncypris micropapillosa Bate, 1972, Pattersoncypris salitrensis (Krömmelbein & Weber, 1971), Pattersoncypris trapezium sp. nov., Looneyellopsis? sagittensis sp. nov., and Theriosynoecum silvai (Silva, 1978). Preservation of this material was very good in the Crato Formation and the Batateira Beds, with numerous well-preserved juvenile carapaces down to the A-6 instar having been found in the latter. Conversely, preservation was very poor in the upper portion of the Barbalha Formation, from which mostly molds were recovered.

Early Aptian marine incursions in the interior of northeastern Brazil following the Gondwana breakup.

This study reports a set of primeval marine incursions identified in two drill cores, 1PS-06-CE, and 1PS-10-CE, which recovered the Barbalha Formation, Araripe Basin, Brazil. Based on a multi-proxy approach involving stratigraphy, microbiofacies, ichnofossils, and microfossils, three short-lived marine incursions were identified, designated Araripe Marine Incursions (AMI) 1-3. AMI-1 and AMI-2, which occur within the shales of the Batateira Beds (lower part of the Barbalha Formation), were identified by the occurrence of benthonic foraminifera, calcareous nannofossils, dinocysts, and a mass mortality event of non-marine ostracods. AMI-3 was recognized in the upper part of the Barbalha Formation, based on the occurrence of ichnofossils and planktonic foraminifera. The observation of the planktonic foraminifera genus Leupoldina for the first time in the basin indicates early Aptian/early late Aptian age for these deposits, and the first opportunity of correlation with global foraminifera biozonation. Our findings have implications for the breakup of the Gondwana Supercontinent, as these incursions represent the earliest marine-derived flooding events in the inland basins of northeastern Brazil.