FOSSIL CHARCOAL IN CRETACEOUS-TERTIARY BOUNDARY STRATA - EVIDENCE FORCATASTROPHIC FIRESTORM AND MEGAWAVE

Organic matter separated from calcareous sandstone from the upper port ion of a deep-water tsunami deposit at Arroyo el Mimbral, Taumalipas, Mexico, which marks the biostratigraphically defined Cretaceous-Tertia ry boundary, consists primarily of fossil charcoal, including semifusi nite and pyrofusinite. Analytical pyrolysis-gas chromatography/mass sp ectrometry revealed the highly aromatic and polyaromatic character of the organic matter assemblage, typical of the products of partial comb ustion. The organic matter probably originated as terrestrial vegetati on that was caught in a firestorm and subsequently transported far off shore in the backwash of a megawave. These data are consistent with th e hypothesis of combustion of large masses of vegetation triggered by a giant extraterrestrial impact in the Gulf-Caribbean region (probably forming the Chicxulub crater in Yucatan) at the very end of the Creta ceous Period.