Genesis and taphonomic biases of Quaternary tank deposits of northeastern Brazil

Abstract

A taphonomic comparison among ten Quaternary tank deposits bearing megafauna remains in northeastern Brazil allowed the identification of four regional-scale taphonomic aspects controlled by climate seasonality: differential preservation of mega-mammal bones, poor physical integrity, spatial resolution (local) and time averaging (104 years). Sedimentary aspects, such as the high degree of packing of fossiliferous layer, indicate conditions of low clastic detrital sediment input in arid conditions. The correlation among geochronological data of tank deposits and paleoclimatic curves of northeastern Brazil suggest that the climate was arid/semi-arid characterized by seasonality between dry and rainy periods. Thus, we postulate the succession of the two paleoenvironmental and paleoecological scenarios during the late Quaternary affecting the formation of fossiliferous tank deposits: (i) the intensity and duration of arid periods led animals to search for water and food, and consequently, concentration and death near these water sources; and (ii) in the rainy season, carcasses, disarticulated and fragmented bones around these water sources were transported and accumulated through high-energy tractive flows, reworking previously buried skeletal material.