Ironing out complexities in karst chronology: (U-Th)/He ferricrete ages reveal wet MIS 5c

Abstract

Karst landforms provide insights into landscape evolution and paleoclimate but are inherently challenging to date. An ancient interval of particularly intense weathering of Western Australian Pleistocene aeolianites is recorded in a spectacular pinnacle karst landscape with associated ferricrete nodules. (U-Th)/He dating of the ferricrete nodules revealed an age of 102.8 + 10.6/−11.4 thousand years, corresponding to marine isotope stage 5c. The (U-Th)/He age thus directly dates the wettest interglacial period in the region over the last 500 thousand years, which was responsible for the dissolution that formed the pinnacles. The reliability of the ferricrete (U-Th)/ He age is supported by bounding optically stimulated luminescence and U-Th dates on associated aeolianites and carbonate precipitates, respectively. A (U-Th)/He approach is globally applicable to aeolianites with associated ferricretes, allowing more accurate dating of the environmental changes affecting these lithologies, and temporally constraining rapid Pleistocene climatic oscillations to better contextualize the associated evolution of the biosphere.