U and Pb variability in older speleothems and strategies for their chronology

Abstract

Speleothem proxy records, coupled with U-Th chronologies, are widely used in studies of palaeoclimate, landscape and faunal evolution. The prospect of extending such studies beyond ∼500 ka has fuelled considerable interest in the U-Pb dating method. While theoretical mechanisms for the transport and incorporation of both U and Pb in speleothem calcite remains a matter of debate, it is clear that natural samples span a broad spectrum of compositional variation, and likely contain Pb components with multiple origins and/or transport pathways. Based upon these observations, optimal methods for sample selection are proposed and a variety of techniques for age estimation are explored. Laser ablat..