We are currently sampling 60 stalagmites from caves in southern Illinois, and southeastern Missouri in order to determine the timing of their initiation. For dating purposes, we are using U/Th techniques and, for the very young stalagmites (200 years BP or less), a combination of U/Th dating and growth laminae counting. Preliminary results of this work and the available published dates of stalagmite initiation in Illinois and Missouri caves correspond to historic and prehistoric seismic events. The dates of initiation for stalagmites collected thus far occurred 200 +/- 50 (n = 5), 1178 +/- 17 (n = 2), 3500 +/- 100, 3,900, 4600 +/- 110 (n = 2), 5500 +/- 240 (n = 2), 11,284 +/- 70, and 17,840 +/- 120 years BP (n = 1 if not indicated). Each of these dates, within limits of analytical error, correspond with known earthquakes associated with the NMSZ determined by others using sand blows and landslides. Additional results from this investigation will be presented at the time of the meeting.
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