... Science Frontiers ONLINE No. 43: Jan-Feb 1986 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects The Cretaceous Incineration The worldwide deposit of iridium at the end of the Cretaceous implies, to many at least, that the great biological extinctions of this period were the consequence of a meteorite impact. It has now been discovered that clay samples from the Cretaceous-Tertiary boundary also contain 0.36-0 .58% graphitic carbon. It is fluffy stuff and suggests that the planet was once covered by a thick layer of soot. Quantitatively, the soot layer is equivalent to the carbon in 10% of the earth's present biomass. The authors speculate that this soot was created by huge wildfires that consumed much of the earth's vegetation and perhaps fossil fuel as well. Terrestrial life was, of course, devastated -- just as it is in the currently popular "nuclear winter" scenarios. The end-of-the-Cretaceous soot is in fact, thicker and more widely spread than nuclear winter theories predict. (Wolbach, Wendy S., et al; "Cretaceous Extinctions: Evidence for Wildfires and Search for Meteoric Material," Science, 230:167, 1985.) Comment. Questions arise, though: How could a single meteorite impact ignite worldwide wildfires? Why haven't other meteorite impacts, recorded abundantly by large craters and astroblemes, also set fire to the planet and left iridium layers? From Science Frontiers #43, JAN-FEB 1986 . 1986-2000 William ...
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... 102 -104 -fold enriched in elemental C (mainly soot), which is isotopically uniform and apparently comes from a single global fire. The soot layer coincides with the Ir layer, suggesting that the fire was triggered by meteorite impact and began before the ejecta had settled." The composition of the hydrocarbons in the sediments points to the earth's biomass (mainly surface vegetation) as the source of the soot. The total quantity of K-T soot is equivalent to that which would be produced by burning 10% of all present terrestrial plant material. (Wolbach, Wendy S., et al; "Global Fire at the Cretaceous-Tertiary Boundary," Nature, 334:665, 1988.) Comment. Unmentioned in the above article is the possibility that extensive wildfires might have been generated by volcanic eruptions, perhaps accompanied by great electrical storms. The 1988 fires in Yellowstone needed no meteoric impact. Reference. Chemical anomalies in the earth's crust are cataloged in ESC1 in Anomalies in Geology. To order this catalog volume, visit: here . Concentration "spikes" of iridium, elemental carbon and soot at the KT boundary, Woodside Creek, New Zealand. (Adapated from Nature, 334:665, 1988). From Science Frontiers #60, NOV-DEC 1988 . 1988-2000 William R. Corliss ...
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