Mass extinction - 6

Mass extinction - 6 - • K/T boundary site in Italy •...

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Unformatted text preview: • K/T boundary site in Italy • 2.5-cm-thick clay layer shows high concentration of iridium Cretaceous-Tertiary Boundary • Some Cretaceous-Tertiary boundary sites also contain – soot – shock-metamorphosed quartz grains Boundary Sites http://wwwdsa.uqac.ca/~mhiggins/MIAC/chicxulub.htm • Deep sea core • Recovered by Joides Resolution in 1997 Boundary Clay http://www.nmnh.si.edu/paleo/blast/k_t_boundary.htm • Proposed meteorite impact crater • Centered on Chicxulub on the Yucatán Peninsula of Mexico • Discovered in 1950’s, interpreted to be volcanic Meteorite Impact Crater But really, how many of these were impact? Dev. Impact: Playford Permian - Becker Triassic-Olsen KT-Alvarez • According to the impact hypothesis – 60 times the mass of the meteorite was blasted from the crust high into the atmosphere – heat generated at impact started raging forest fires that added more particulate matter to the atmosphere • Sunlight was blocked for several months – caused a temporary cessation of photosynthesis – food chains collapsed and extinctions followed Impact Consequences •...
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This note was uploaded on 10/26/2010 for the course GS 101 taught by Professor Passer during the Summer '09 term at University of Washington.

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Mass extinction - 6 - • K/T boundary site in Italy •...

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