It Really was the Asteroid--New Study: Sudden Impact Killed off Dinosaurs and Much of Other Life
martyb writes:
Fossil remains of tiny calcareous algae not only provide information about the end of the dinosaurs, but also show how the oceans recovered after the fatal asteroid impact. Experts agree that a collision with an asteroid caused a mass extinction on our planet, but there were hypotheses that ecosystems were already under pressure from increasing volcanism. "Our data speak against a gradual deterioration in environmental conditions 66 million years ago," says Michael Henehan of the GFZ [(GeoForschungsZentrum)] German Research Centre for Geosciences. Together with colleagues from the University of Yale, he published a study in the scientific journal Proceedings of the National Academy of Sciences(PNAS) that describes ocean acidification during this period.
He investigated isotopes of the element boron in the calcareous shells of plankton (foraminifera). According to the findings, there was a sudden impact that led to massive ocean acidification. It took millions of years for the oceans to recover from this acidification. "Before the impact event, we could not detect any increasing acidification of the oceans," says Henehan.
The impact of a celestial body left traces: the "Chicxulub crater" in the Gulf of Mexico and tiny amounts of iridium in sediments. Up to 75 percent of all animal species went extinct at the time. The impact marks the boundary of two geological eras - the Cretaceous and the Palaeogene (formerly known as the Cretaceous-Tertiary boundary).
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