Abstract:

The rhenium-osmium (Re-Os) chronometer plays a significant role in constraining the timing and tempo for a wide range of processes in the Earth sciences and cosmochemistry. Critically, the Re-Os system permits the dating of minerals and materials – and therefore processes – that otherwise cannot be directly dated using other radiometric chronometers. In addition to providing age constraints, Os isotope stratigraphy can be used to investigate changes in Earth system states across intervals of interest throughout Earth history. Here I will present new Re-Os age constraints from Ediacaran-age (635-541 Ma) sedimentary units that host some of the earliest fossil animals and record large-magnitude disturbances to multiple biogeochemical cycles.

In a second vignette, I will focus on the mid-Pleistocene transition (MPT) an interval during which the glacial cycle lengthened, ice volume increased, and the shapes of marine isotopic stages display a more asymmetric pattern. A new Os isotope record from IODP cores is used to evaluate the role of changing substrate in controlling ice sheet dynamics across the MPT and into the late Pleistocene.