Beyond 500 ka: Progress and prospects in the UPb chronology of speleothems, and their application to studies in palaeoclimate, human evolution, biodiversity and tectonics

This review summarises current research aimed at extending the chronology and thus scientific utility of speleothems beyond the 500 ka limit previously imposed by conventional UTh dating methods. The UPb decay scheme is familiar to all geoscientists but its application to speleothems is a relatively recent development, and one set to revolutionise their use in studies of climate change, human evolution and migration, biodiversity, tectonics and landscape evolution. Technological advances, such as the introduction of multi-collector ICPMS instruments, have played a key role in this breakthrough and multiple inter-laboratory and inter-method comparisons provide evidence that the methodology is now mature and that the ages obtained are robust. Some impediments remain, in particular with respect to corrections for initial isotopic disequilibrium (younger samples) and the construction of internal chronologies (older samples) but these are areas of intense research activity and are likely to see significant advances in the near future. The coupling of speleothem UPb dating with other nascent technologies, offering the prospect of precise palaeotemperature estimation, is an exciting development in palaeoclimate science, while UPb chronologies of archaeological sites are producing important new insights into human evolution. Although less well developed at this point, the methodology appears equally well suited and significant for future studies of past faunal change, and landscape evolution.