Reassessing Gondwana rifting during the Early Cretaceous: biostratigraphic and tectonic implications of the Abaiara Formation, Araripe Basin, northeastern Brazil

The present work details a recently discovered ostracod fauna from the Abaiara Formation of the Araripe Basin, northeastern Brazil, comprising the following species: Theriosynoecum varietuberatum , Tucanocypris camposi , Cypridea ( Morininoides ) grekoffi and ‘ Darwinula ’ sp. Of these species, Theriosynoecum varietuberatum is of biostratigraphic interest, as the index-species for the Theriosynoecum varietuberatum Zone, coded as O02. This zone marks the Berriasian (lowermost Cretaceous) interval in the Local Stage Rio da Serra recorded throughout several lithostratigraphic units deposited under the palaeogeographical context of the Gondwana rifting system related to the Afro/Brazil depression in the earliest Cretaceous. This is the first record of Zone O02 in the Araripe Basin, and this new record is an important indicator of continuous sedimentation between the Missão Velha and Abaiara formations in the Araripe Basin. To evaluate if the occurrences of Theriosynoecum varietuberatum resulted from reworked material, analyses of the population age-structure were performed. As a result, the index-species for Zone O02 was concluded to be preserved in an autochthonous context.