A HIGH-RESOLUTION HOLOCENE EL NIÑO RECORD FROM FLOOD DEPOSITED SEDIMENTS PRESERVED IN SPELEOTHEMS

Groundwater flow in Crevice Cave, Missouri is governed by numerous recharge points along with a limited number of outlets, which creates a condition of slow back flooding during high recharge events. Fine silt and clay particles may become suspended during flooding and may be deposited as thin layers on speleothem and bedrock surfaces that are inundated by the flood waters. In the case of stalagmites, these thin clay-rich deposits may be preserved by the subsequent resumption of calcite growth, which encases the detrital layer. High-precision U-Th dating reveals that stalagmite CC-99-12-B was deposited at the fast average deposition rate of 68 mm per thousand years, and nineteen U-Th dates reveal an unusually uniform rate of deposition throughout the past 8,000 years. Furthermore, the frequency of flood-deposited sediments preserved in stalagmite CC-99-12-B reveal a striking correlation with the frequency of Holocene El Niño/Southern Oscillation (ENSO) as modeled by Clement et al. (2001). Millennial-scale cyclicity is apparent in the stalagmite flood record. In modern times, El Niño increases flooding in Missouri by enhancing moisture transport from the Gulf of Mexico, thereby generating increased storm potential during late fall and winter. To the best of our knowledge, our record is the most complete and best-dated long-term record of ENSO behavior for the North American mid-continent. Significance of these correlations may lead to predictions of frequency and magnitude of flooding for periods of warm ENSO-dominated climates.