Terminal Cretaceous Events

Abstract

SEVERAL explanations have been offered (see refs. 1–3) for the abrupt faunal extinctions at the end of the Cretaceous and, with the advent of the JOIDES Deep Sea Drilling Project, it was hoped that the nature of the extinctions—at least for calcareous microfossils—would be found by coring a transitional sequence across the boundary in deep sea facies. Unfortunately, the results from the few JOIDES holes so far penetrating the Cretaceous–Tertiary boundary indicate that the unconformity is even greater in the deep ocean basins than on the continents and that a transitional sequence will probably never be found, especially in calcareous pelagic sediments. Although disappointing on first inspection, these data nevertheless provide the most tangible and significant clue yet as to the nature of the terminal Cretaceous event.