Paleo-humidity changes in a tropical Aptian continental to transitional system: a case study from the Araripe Basin, Northeastern Brazil

Abstract Although many paleogeographic reconstructions depict equatorial Brazil as being predominantly arid during the Aptian, studies using palynomorphs suggest climatic fluctuations between humid and arid phases. There is, however, a lack of studies utilizing additional proxies to demonstrate such changes. We present a case study for climatic variation in an Aptian continental to transitional system in the Araripe Basin, Brazil, applying geochemical, palynological and ostracod analyses, integrated with previously published sedimentologic and stratigraphic data from the Barbalha Formation (46 samples; drill core 1PS-06-CE). Cluster analysis of micropaleontological and weathering proxies allowed to identify seven climatic clusters (G1-G7): G1-G4 from the Batateira Beds (lower Barbalha Formation) and G5-G7 from the upper Barbalha Formation. G1-G4, linked to lacustrine facies, indicate a generally more humid interval, with proxies showing intense weathering and long-distance element transport. Paleoredox data suggests low oxygenation. In contrast, G5-G7, associated with bayhead delta environments, reflect a relative increase in aridity, with reduced weathering and evidence of subaerial exposure of organic particles. Nevertheless, humidity persisted, supported by the occurrence of pseudo amorphous organic matter and marine ichnofossils. These results show that despite an overall arid trend, significant moments of humidity were still present in equatorial Brazil during the Aptian.