Computer Science
Scientific paper
Apr 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992e%26psl.109..543s&link_type=abstract
Earth and Planetary Science Letters (ISSN 0012-821X), vol. 109, no. 3-4, April 1992, p. 543-559.
Computer Science
50
Aerosols, Atmospheric Composition, Bolides, Cretaceous-Tertiary Boundary, Impact Melts, Sulfuric Acid, Acid Rain, Geochemistry, Meteorite Collisions, Paleoclimatology
Scientific paper
Impact glasses from the K/T boundary in Haiti include high-Ca glasses with up to 1 wt pct SO3, formed by the fusion of anhydrite- or gypsum-rich evaporite sediments in the presence of high-silica melts, derived from melting of continental crust. Experimental studies have duplicated these two melts by fusion of gypsum and andesite, and suggest a formation temperature of 1300 C. Geochemical evidence from the glasses is consistent with their derivation from the 180 km diameter Chicxulub impact crater on the Yucatan peninsula (Mexico), situated in a thick late Cretaceous evaporite succession. This large-diameter crater is most likely the result of a cometary impact, on the basis of bolide scaling from the Ir anomaly in K/T boundary sediments. The sulfur degassing associated with formation of the high-Ca glass alone could have formed a 2 x 10 exp 16 g H2SO4 stratospheric aerosol. However, the total sulfur degassing from the evaporite-rich sediments in the Chicxulub impact site may have led to formation of 3.8 x 10 exp 18 to 1.3 x 10 exp 19 g sulfate aerosol, and global atmospheric mass loading from the sulfate aerosol alone is estimated to be of the order of 1-2.6 g/sq cm. Combined with the great optical depth estimates of Pollack et al. and Covey et al. resulting from an impact 'dust' cloud, the sulfate aerosol may have contributed not only to a rapid decline in global surface temperatures to near-freezing in about one week, but also prolonged the cooling for several years because of the time-dependent conversion of SO2 to H2SO4 aerosol in the atmosphere.
Carey Sean
D'Hondt Steven
Sigurdsson Haraldur
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