Historic earthquakes generated by the New Madrid seismic zone represent some of the largest recorded in the United States, yet prehistoric events are recognized only through deformation in late-Wisconsin to Holocene-age, near surface sediments (liquefaction, monoclinal folding, and changes in river meanders). In this article, we show that speleothems in caves of southwestern Illinois and southeastern Missouri may constitute a previously unrecognized recorder of large earthquakes in the U.S. midcontinent region. The timing of the initiation and regrowth of stalagmites in southwestern Illinois and southeastern Missouri caves is consistent with the historic and prehistoric record of several known seismic events in the U.S. midcontinent region. We conclude that dating the initiation of original stalagmite growth and later postearthquake rejuvenation constitutes a new paleoseismic method that has the potential for being applied to any region around the world in the vicinity of major seismic zones where caves exist. Use of this technique could expand the geographical distribution of paleoseimic data, document prehistoric earthquakes, and help improve interpretations of paleoearthquakes.

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