Paleoenvironmental and paleoclimatic control on early diagenetic processes and fossil record in Cretaceous continental sandstones of Brazil

The Early Cretaceous, pre-rift continental rock sequences of northeastern Brazil (Rio do Peixe, Araripe, Recôncavo–Tucano, and Sergipe–Alagoas basins), deposited in a wide intracontinental basin (Afro–Brazilian Depression), and the Late Cretaceous, post-rift continental deposits of the Paraná Basin (Bauru Group, Minas Gerais) reflect the controlling processes related to the Brazilian record of nonmarine fossil vertebrates. These sequences were deposited in braided fluvial, eolian, and lacustrine environments in a semi-arid to arid climate. Sedimentary and diagenetic processes ascribed to paleoclimatic and paleoenvironmental conditions are among the major factors that control fossil preservation in fluvial deposits. The pre-rift successions contain a rare record of a dinosaur fauna that lived near more humid highlands in the northern portion of the Afro–Brazilian Depression, relative to its southern counterpart, where hardly any fossil remains would have been preserved in the adverse climatic conditions. The Afro–Brazilian Depression is interpreted as a large pathway for dinosaurs before the breakup of Gondwana. Conversely, abundant dinosaur remains (bones, eggs, and teeth) and other vertebrates (turtles, crocodiles, frogs, and fish) are found in the Bauru Group in the Paraná Basin. In this unit, the seasonal paleoclimate provided sufficient conditions for the maintenance of bodies of water that served as nesting and living sites for various vertebrate forms. Paleoclimatic conditions are assumed to account for the different preservation of bones in the Paraná Basin relative to the Afro–Brazilian Depression, because the latter was subject to more arid conditions, and the humid environment was restricted to the northern margin.