--> Abstract: The Chicxulub Impact Was More Deadly Than All the K/T Volcanoes Put Together, by A. R. Hildebrand; #91012 (1992).

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ABSTRACT: The Chicxulub Impact Was More Deadly Than All the K/T Volcanoes Put Together

HILDEBRAND, ALAN R., Geological Survey of Canada, Ottawa, Ontario, Canada

The five most compelling evidences of a large Cretaceous/Tertiary (K/T) boundary impact are that the siderophile trace elements occur in the boundary layers in large amounts and in chondritic proportions; the boundary stratigraphy occurs globally with a uniformly distributed fireball layer and a geographically restricted ejecta layer; shocked mineral grains and tektites occur in the boundary layers; and the Chicxulub crater, a 180 km diameter probable impact crater buried in Yucatan, Mexico, is suitably located in both time and space to produce the layers.

Knowing the size and location of the K/T crater allows well-constrained modeling of the impact's environmental consequences. (The projectile was a comet based on the global Ir fluence and the crater's size.) The Chicxulub impact released (~1032 ergs on a timescale of minutes. This equals all the internal heat released by the Earth in ~10,000 years, all the energy released by subaerial volcanoes in ~500,000 years, and all the energy released by the Deccan flood basalts in ~1,000,000 years. The Chicxulub impact released its energy ~1012 times faster than the Deccan eruptions. Because the impact occurred in a carbonate platform >3 km thick, shock-produced CO2 could have caused severe (~10 degrees C) greenhouse warming for 103 to 105 years. The combination of the large size of the crat r and the thick carbonate/evaporite target may mean the K/T impact was particularly deadly.

 

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)