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 Yucatn Peninsula of Mexico Discovered in 1950s, 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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Mass extinction - 6 - K/T boundary site in Italy...

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