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Título

Low-temperature thermochronology (AFT and ZFT) on the eastern margin of the Parnaíba Basin (NE Brazil) – did sea way paths exist between the Cretaceous Parnaíba and Araripe basins?

Texto do resumo

The sedimentary basins of Northeast Brazil trace the history of the paleocontinent Gondwana. The Parnaíba and Araripe basins, currently separated, record equivalent Cretaceous sequences, suggesting that an epicontinental sea advanced over the northern portion of current South America connecting these basins. Ordovician-Silurian basal units of the eastern margin of the Parnaíba Basin are uplifted to >1,000 m above sea level, forming the contemporary table relief of the Serra de Ibiapaba (Piauí and Ceara states). The timing of this uplift and whether it played a role in connecting the Parnaíba and Araripe basins are hitherto unknown. This work aims to determine the thermal history of burial, denudation and exhumation of the eastern margin of the Parnaíba Basin through apatite (AFT) and zircon fission track (ZFT) thermochronometry. We present preliminary results on 28 AFT samples from sedimentary basal units and crystalline basement exposed between the Parnaíba and Araripe basins. The samples were collected in 5 E-W geological cross sections throughout the eastern borders of the Parnaíba basin. AFT central ages range from 316 to 72 Ma and mean track lengths from 10,8 to 15,6 μm. ZFT ages range from 427 to 513 Ma. The younger AFT were obtained in the northern and central par of the eastern Parnaíba basin aligned range. These ages seem to be linked to the reactivation of Ediacaran continental shear zones, such as the NNE-SSW Transbrasiliano lineament, along the northeastern border of the Parnaíba basin. The southern portion of the Parnaíba basin does not record Meso-Cenozoic cooling ages, implying a distinct evolution of the basin margin. Additional AFT analyses are ongoing in order to provide robust models for the thermo-tectonic evolution of the area that might potentially answer the enigma of the Cretaceous Parnaíba – Araripe connection. The authors gratefully acknowledge support from Shell Brasil Petróleo Ltda. and the strategic importance of the support given by ANP (Brazil’s National Oil, Natural Gas and Biofuels Agency) through the R&D levy regulation (Technical Cooperation #20.219-2).

Palavras Chave

Parnaíba Basin; Thermochronology; Paleogeography; Apatite fission track