Homo erectus landscapes: Paleosols in the Bapang and Upper Sangiran Formations, Solo Basin, Central Java

The stratigraphically lowest H. erectus fossils in the Solo basin occur in the upper Sangiran Formation and date to < 1.58 Ma. H. erectus fossils increase in abundance in the overlying Bapang Formation and occupy the area until 1.0 Ma. Archaeological sites in the Solo basin, such as Ngebung, are concentrated in the terraced gravels or the conglomeratic Grenzbank zone of the Bapang Formation. No lithologies reflecting low energy depositional environments have been identified or associated with any hominin locality. In August 2001 our team identified paleosols in the middle Bapang Formation and in the upper Sangiran Formation. These ancient soils mark the presence of habitable land surfaces in the Solo basin. Two paleosol horizons were found at Pucung, Bapang Formation. The soil features of these horizons are pedogenic carbonate accumulations, risoliths (root casts) of grassy plants, and insect burrows. Two other paleosol horizons were identified at stratigraphically-lower Bukuran, upper Sangiran Formation. Here the soils are associated with lake margin environments and exhibit characteristics of poor drainage, including gray colors, redoximorphic features, and the preservation of detrital organics including in situ tree trunks. The identification of paleosols in the Solo basin provides a robust depositional and environmental context for Homo erectus in Java. The buried soils will provide information about local and regional paleoenvironments prior to and during Homo erectus' occupation of central Java. Paleosol frequency through time will yield information about Homo erectus occupation patterns, and their identification should result in the discovery of new Homo erectus localities with primary contexts.