The asteroid impact that ended the age of dinosaurs 65 million years ago didn't incinerate life on our planet's surface - it just broiled it, a new study suggests. The work resolves nagging questions about a theory that the impact triggered deadly wildfires around the world, but it also raises new questions about just what led to the mass extinction at the end of the Cretaceous period.
In the hills behind the historic homestead in Waipara, north Canterbury, about 45 minutes drive north of Christchurch in the South Island, are limestone canyons and riverbeds yielding precious remnants of that catastrophic event when New Zealand was still under the ocean.The Waipara riverbed is rich in the element iridium, also found mainly in Denmark and Italy. Iridium is rare on earth but abundant in meteorites.Scattered across the Waipara property are massive rounded rocks, weighing over a tonne each, which Goord calls God's marbles.
But Keller and Addate worried that we were misreading both the geologic and fossil records. They conducted surveys at numerous sites in Mexico, including a spot called El Peñón, near the impact crater. They were especially interested in a 30-ft. layer of sediment just above the iridium layer. That sediment, they calculate, was laid down at a rate of about 0.8 in. to 1.2 in. per thousand years, meaning that all 30 feet took 300,000 years to settle into place.Analysing the fossils at this small site, they counted 52 distinct species just below the iridium layer. Then they counted the species above it. The result: the same 52. It wasn't until they sampled 30 feet higher - and 300,000 years later - that they saw the die-offs.