Palaeobiogeography of the Bauru Group, a dinosaur-bearing Cretaceous unit,northeastern Parana Basin, Brazil

The integration of sedimentologic, palaeontologic and petrologic data allow s interpretation of the palaeoclimatic evolution in the northeastern Parana Basin of Brazil during the Late Cretaceous. The study of the dinosaur-bear ing Bauru Group in Minas Gerais State in two areas, the Uberaba and the Pra ta regions, allows us to discuss biogeographic aspects related to the dinos aurian fauna in Brazil. The terrigenous and carbonate rocks of the Bauru Gr oup were deposited in fluvial, eolian and lacustrine environments in a semi -arid to arid climate with marked seasonality in which dry periods alternat ed with periods of heavy rain. The climatic evolution during this period of deposition can be divided in two intervals: Time 1 (T1), Coniacian-Campani an, when the Uberaba and Adamantina Formations were deposited, and Time 2 ( T2), mainly Maastrichtian, when the Marilia Formation was deposited. During both intervals, the humidity was higher in the Uberaba region than in the Prata region, eolian deposits and caliche profiles being present in the lat ter, but not in the former. Extensive skeletal deposits and nesting sites i ndicate that favourable environmental conditions for the dinosaurian fauna existed in the Uberaba region, while the Prata region was probably a gatewa y to fauna migrating from the northeastern Parana Basin to Argentina and Bo livia. If has been suggested that Cretaceous dinosaur biogeography in the S outhern Hemisphere was largely controlled by the sequential breakup of Gond wana. Locally, the migration and preferential distribution of dinosaurian h abitats were controlled by climatic conditions, geographic topography and e ventually by volcanic activity. (C) 2000 Academic Press.