End-Cretaceous Mass Extinction Event: Argument for Terrestrial Causation

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Science  27 Nov 1987:
Vol. 238, Issue 4831, pp. 1237-1242
DOI: 10.1126/science.238.4831.1237


The end-Cretaceous mass extinctions were not a geologically instantaneous event and were selective in character. These features are incompatible with the original Alvarez hypothesis of their being caused by a single asteroid impact that produced a world-embracing dust cloud with devastating environmental consequences. By analysis of physical and chemical evidence from the stratigraphic record it is shown that a modified extraterrestrial model in which stepwise extinctions resulted from encounter with a comet shower is less plausible than one intrinsic to the earth, involving significant disturbance in the mantle.