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Paper No. 8
Presentation Time: 8:00 AM-6:00 PM


SUBT, Cristina, University of Texas at El Paso, El Paso, TX 79968, ABBOTT, Dallas H., Lamont-Doherty Earth Observatory, Palisades, NY 10964, WEBER, Lisa C., Columbia College, New York, NY 10027 and BREGER, Dee, Micrographic Arts, Greenfield, NY 19104,

Accounts from a distant past have recorded stories of a global climate cooling event that lasted 18 months beginning in March of 536 AD and lasting until September of 537 AD (Stothers, 1984). Tree core analyses worldwide have been shown to support these stories as well (Baillie, 2007). Debate has ensued for decades about whether this event was due to a volcanic eruption, or an extraterrestrial impact. Now at last we may be close to finding an answer. Two crater candidates in the Gulf of Carpentaria (Kanmare and Tabban, 18 and 12 km. in diameter respectively) may have been the site of a comet impact at the time of the climate cooling event. The impactor was about 600 m. in diameter, capable of producing enough dust and debris to have caused a major cooling event (Rigby, 2004). To find out if these craters were indeed the site of an impact, samples were taken from the nearest usable cores and sieved into four size fractions (>250, >125, >63, and >38mm). Potential impact grains were then picked from core MD972131 (MD31) and analyzed for their chemical composition and physical features. The grains picked displayed a wide range of evidence that supports our hypothesis of an impact, such as impact spherules, shocked minerals, vesicular quartz, and shock morphology of different kinds, as well as marine microfossils found within spherule factories, which lead us to conclude that the latter material is not from the impactor but rather from the impact site. Future research will include extensive thin section and microprobe work, which may shed better light onto the composition of some grains, and begin to explain the details of the impact event. Gaining sufficient evidence to be sure that the impact in the Gulf of Carpentaria caused a climate downturn can begin to give insight into other events in the paleoclimatic record and perhaps even future events.
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