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Cave sediments suggest global cooling 13K years ago not caused by asteroid

Cave sediments suggest global cooling 13K years ago not caused by asteroid

Science
July 31 (UPI) -- Geochemical signatures found in sediments recovered from a Texas cave suggest the Younger Dryas, a period of global cooling that occurred 13,000 years ago, was caused by a series of Earth-based processes, not an extraterrestrial impact. Previously, scientists in search of an explanation for the Younger Dryas have pointed to spikes in several rare earth metals as evidence that an asteroid or comet impact triggered the cooling. Advertisement Most recently, when researchers looked at the sedimentary evidence, they found these spikes in rare earth metals actually featured relatively low concentrations of iridium, ruthenium, platinum, palladium and rhenium -- levels inconsistent with an extraterrestrial impact event. "The isotopic signatures and concentrations can be explained...