However, the most notable application of Os in dating has been in conjunction with iridium, to analyze the layer of shocked quartz along the Cretaceous–Paleogene boundary that marks the extinction of the dinosaurs 66 million years ago.
[7] The input of both materials in the marine environment results in the observed 187Os/188Os of the oceans and has fluctuated greatly over the history of our planet.
[9] This allows for researchers to make estimates on weathering fluxes, identifying flood basalt volcanism, and impact events that may have caused some of our largest mass extinctions.
With the average extraterrestrial 187Os/188Os of ~0.13 and the huge amount of Os this impact contributed (equivalent to 600,000 years of present-day riverine inputs) lowered the global marine 187Os/188Os value of ~0.45 to ~0.2.
[11] While catalytic converters have been shown to drastically reduce the emission of NOx and CO, they are introducing platinum group elements (PGE) such as Os, to the environment.
Impacted surface waters tend to have depleted values compared to deep ocean and sediments beyond the limit of what is expected from cosmic inputs.
The long half-life of 184Os with respect to alpha decay to 180W has been proposed as a radiometric dating method for osmium-rich rocks or for differentiation of a planetary core.