Landscape development preceding Homo erectus immigration into Central Java, Indonesia: the Sangiran Formation Lower Lahar

The Sangiran Dome is the primary stratigraphic window for the Solo Basin, a coastal feature on the Pliocene–Pleistocene Sunda subcontinent south margin. In the Dome, the Lower Lahar unit (LLU) is a lahar-type debris flow overlying near-shore marine sediments. The event that emplaced the LLU likely originated from sector collapse on a neighboring volcanic edifice. Freshwater mollusc fossils in the LLU indicate that swamps or shallow lakes lay between the edifice and the current Dome area. 40Ar/39Ar analyses on hornblende separates from six pumice lenses suggest that the LLU was deposited as early as 1.90±0.02 Ma. The event resulting in deposition of the LLU transformed late Pliocene near-shore marine environments into estuarine and marsh settings. Shortly thereafter, glacioeustatic sea level falls completed the local transition to fully terrestrial environments that attracted Homo erectus to southernmost Sunda in the Early Pleistocene.