Comprehensive taphonomic study of the surface and histology of Pleistocene fossils from a fluvio-lacustrine system in the Humid Pampas

Fluvio-lacustrine environments preserve abundant vertebrate fossil assemblages and provide valuable settings for investigating the biological, physical and chemical processes involved in fossilisation. However, integrated taphonomic studies combining macrotaphonomic observations with histotaphonomic and mineralogical analyses remain scarce. Here, we apply a multiproxy approach to reconstruct decomposition, transport, burial and fossildiagenesis within a well-constrained fluvio-lacustrine succession, using the Salto de Piedra Palaeontological Locality in the Argentine Pampas as a case study. Carnivore modifications recorded throughout the fossil-bearing sequence indicate that predation and scavenging were the principal drivers of carcass accumulation, disarticulation, bone fragmentation and skeletal dispersal. The absence of microbial bioerosion is consistent with rapid skeletonisation, suggesting that early carnivore activity limited bacterial degradation of bone tissues during decay. Despite deposition in an open-air fluvio-lacustrine setting, the fossils exhibit minimal evidence of subaerial exposure, including low levels of weathering and abrasion. Permineralisation is likewise limited and involves predominantly iron oxides and carbonate minerals. These findings support the formation of mainly autochthonous to parautochthonous attritional assemblages under low-energy depositional conditions. Our results demonstrate the value of integrating multiple taphonomic proxies to reconstruct fossil preservation pathways and improve palaeoenvironmental, palaeoecological and biochronological interpretations of Quaternary continental vertebrate assemblages.