The Beginning of the Mesozoic: Pangean Breakup with 70 Million Years of Environmental Stress

By

D.J. Bottjer (University of Southern California)

Two of Earth’s biggest mass extinctions bracket the beginning and end of the Triassic. Compared to the temporal spacing of other Phanerozoic mass extinctions, these are relatively close, on the order of 40 million years apart. Given that these two mass extinctions are also associated with prolonged recoveries, and that several minor mass extinctions occurred during this time, it is likely that as much as half of the first 70 million years of the Mesozoic occurred under conditions of heightened environmental stress. Recent work has shown that although events causing the mass extinctions that begin and end the Triassic may not be related, they occurred quite rapidly. The beginning of the Mesozoic can therefore be characterized as a time with prolonged environmental stress overlain by two temporally brief intervals of environmental and biotic stress. The most likely candidate for long-term environmental stress is the early breakup of Pangea, including tectonic, oceanographic and climatic changes. Candidates for short term stress include changes in conditions associated with Pangean breakup, as well as bolide impact. Thus, the character of these mass extinctions, as well as general environmental and biotic conditions during the beginning of the Mesozoic, were most likely largely shaped by processes leading to the breakup of Pangea. Such processes also had a strong control on source rock deposition. 

AAPG Search and Discovery Article #90008©2002 AAPG Pacific Section/SPE Western Region Joint Conference of Geoscientists and Petroleum Engineers, Anchorage, Alaska, May 18–23, 2002.