A recent discovery at El Kef in Tunisia helps to buttress the already impressive evidence for the thesis that the impact of a large meteorite was responsible for the mass extinction (and the death of the dinosaurs) at the end of the Cretaceous period 65 million years ago. Examining rocks which were then submerged in the warm-water ocean, scientists have found fossilized dinoflagellates that ordinarily appear only in cold water regions, but which appear in a layer of sediment right at the KT boundary (the point of transition from Cretaceous to Tertiary). This supports the hypothesis that enormous quantities of sulfates and other particulate matter ejected into the atmosphere blocked off the sunlight and induced a long cold spell—an “impact winter”—which persisted for a number of years. Though the climatic (and climactic) event probably lasted no more than half a dozen years, the fossil record indicates that it took the ocean nearly 2000 years to revert to its previously warm temperature.

(Purdue University)

--From June 2004 Austin Review KB