Amazing stuff!
"One underused isotopic tracker is osmium, a dense, rare, and stable metal. The ratio between different osmium isotopes in seawater depends on how much of the metal leached out from the continents, the mantle, or even extraterrestrial sources such as asteroids, at any given time. To better understand osmium, a team of researchers collected and analyzed rocks containing the element from the Mid-Pacific Mountains, the Indian Ocean, and central Italy. They then combined these and existing data to reconstruct an isotopic record of osmium from the present all the way back to the Cretaceous, when dinosaurs roamed the Earth.
The record clearly tracks large-scale changes to Earth, such as when the Atlantic Ocean opened up, when the Himalaya mountains formed, and when the planet became covered with ice. It also followed less flashy changes, like the supercontinent Gondwana slowly weathering. ..."
From the editor's summary and abstract:
"Editor’s summary
Osmium occurs in Earth’s crust at the low, low rate of 50 parts per trillion. Even so, its isotopes are sensitive measures of environmental change over Earth’s history because they get variably transferred to seawater through volcanoes, rivers, and even extraterrestrial impacts. Matsumoto et al. collected 187Os/188Os data from outcrops in Italy and deep-sea cores in the Pacific and Indian oceans.
They compiled these with existing data to make a highly resolved marine osmium-isotopic record over the past 143 million years. The record shows cycles related to large Cretaceous eruptions, opening of the Atlantic Ocean, and changing Cenozoic climate. ...
Abstract
Tectonic events and volcanic pulses forming large igneous provinces (LIPs) have altered Earth’s paleoclimate. Osmium (Os) and strontium (Sr) isotopic ratios are key tracers of past continental weathering and LIP eruptions. However, limited Cretaceous seawater Os and riverine Os–Sr data have hindered quantitative reconstructions.
In this study, we present a long-term Os isotopic record from the Cretaceous to the present, revealing ~10– to 20–million-year cycles during the Cretaceous that align with rhythmic LIP eruptions.
Seawater Os–Sr isotopic trends indicate transitions in continental weathering patterns during the Late Cretaceous [~90 million years ago (Ma)] and Paleogene (~35 Ma) ascribed to intensified weathering of interior Gondwana during the opening of the Atlantic Ocean and the uplift and glaciation of the Himalaya, respectively.
Our Os isotopic record highlights its utility in tracing long-term LIP cycles and identifying major paleogeographic turning points."
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