Palaeoenvironments and palaeontology of the Atambua Basin, West Timor, Indonesia

Pleistocene vertebrate faunas have long been known from the island of Timor but have rarely been studied. In particular, dwarf elephant-like proboscideans such as Stegodon were once widespread across the island, including to the Atambua Basin, but the cause of their extinction is unknown. Here, we document the fossil Pleistocene fauna of this basin with their palaeoenvironmental context. We also investigate the possibility of human-Stegodon chronological overlap. Our methods include field survey, excavation, pollen analysis, and U-series dating. Palaeoenvironmental data based on geomorphology and hydrological information show a transition from marine to fluvial depositional conditions in the basin during Pleistocene. Pollen data supports this interpretation and shows a clear shift from mangrove to terrestrial vegetation types. Palaeoclimatic conditions after the transition are characterized by a high humidity with high-flow water across the basin. Fossils of vertebrate faunas are restricted to fluvially-derived sandstone units. Meanwhile lithic artefacts were recorded widely across the basin, in the from of surface finds. There is so far no example of direct association of lithic artefacts with extinct Pleistocene faunas. Direct dating of the vertebrate fossils suggest they came from the Middle Pleistocene or earlier, and consequently pre-date the oldest current records of modern human existence on the island ~45,000 years ago.