Pedogenic processes and climatic conditions from Cretaceous (Albian) tropical paleosols of the Itapecuru Formation, Parnaíba Basin, northeast Brazil

Paleosols are an under-utilized tool for paleoenvironmental and paleoclimatic reconstruction in Brazilian intracontinental basins. The Itapecuru Formation, from the Lower Cretaceous of the Parnaiba Basin, consists of a 600-m-thick succession of interbedded very fine-to-fine-grained sandstone, mudstone, and paleosols containing rich fossil assemblages. This paper provides a detailed description of the macro and microscopic pedogenic features of a hydromorphic paleosol profile whithin the Itapecuru Formation. Analyses of clay mineralogy and whole-rock geochemistry in the hydromorphic paleosols at the Prata locality are used to infer pedogenic processes, paleoclimate, paleohumidity and paleovegetation. Estimates of paleoprecipitation and paleotemperature using climofunctions, chemical index of alteration without potassium, and paleosol weathering index proxies (PWIs) show values ranging from 810 to 1042 mm/yr (SE = +/- 78.1 mm/yr) and 10.9 to 11.8 degrees C (SE = +/- 0.23 degrees C), respectively. Climofunction values (MAP and MAT), paleohumidity, Koppen aridity index, and pedogenic clay mineral content suggest a humid paleoclimate during soil-forming and weathering processes. Based on these climate data and previously published paleogeographic and palynological studies, the Cretaceous (Albian) Prata pedotype was formed within the equatorial humid belt with vegetation of wet tropical forests.

Automated summary

This study investigates the paleosols in Brazilian intracontinental basins and focuses on a hydromorphic paleosol profile in the Lower Cretaceous Itapecuru Formation. The research analyzes clay mineralogy and whole-rock geochemistry to infer pedogenic processes and reconstruct paleoclimate, paleohumidity, and paleovegetation. The results suggest a humid paleoclimate with wet tropical forests during the Cretaceous period.