Towards an astronomical age model for the Lower to Middle Pleistocene hominin-bearing succession of the Sangiran Dome area on Java, Indonesia

Abstract

Well-dated paleoanthropological sites are critical for studying hominin evolution and dispersal, especially when related to regional or global climate change. For the rich hominin fossil record of Africa, this has been facilitated by the development of high-resolution astronomically tuned age models. So far, such age models are lacking for the Pleistocene of SE Asia with its similarly rich fossil hominin record. This study aims to develop an astronomical age model for the classical Sangiran Dome area of central Java, using a semi-quantitative grain size record of the hominin-bearing Sangiran and Bapang Formations. Two initial age models were established based on two different sets of tie points and approaches (constant sedimentation rate and Bayesian age modelling). These models, which correspond to the paleoanthropological short and long chronologies for the arrival of Homo erectus on Java, were used to convert the grain size record into a time series for time series analysis. The preferred initial age model was then used as a starting point to correlate or tune the grain size record to the LR04 benthic δ18O isotope stack. This tuning was constrained by the sudden switch in grain size from obliquity to double obliquity related cycles; this switch can be linked to the onset of the Mid-Pleistocene Transition at ∼1.2 Ma marked by a similarly abrupt change in ice age history. Two slightly different astronomical age models are presented, while a one cycle hiatus at the base of the Grenzbank cannot be excluded. These age models are in better agreement with the short paleoanthropological chronology, arguing for a late arrival of H. erectus on Java. Finally, such astronomical age models, when finalized, will provide the accurate, precise, and high-resolution age control required to gain insight into the influence of both regional and global climate change on the Pleistocene paleoenvironment and potentially the hominin population of Java.