A 13,000-YEAR REGIONAL RECORD OF HOLOCENE STORMS FROM TERRIGENOUS LAKE SEDIMENT, NORTHEASTERN USA

Lakes in the hilly terrain of the northeastern United States preserve sedimentary archives that reveal the spatial and temporal patterns of major Holocene storm events. We retrieved eighteen 3.5- to 6-meter sediment cores from eleven small (0.03 to 4 sq. km), deep (13 to 32 m) Vermont and New York lakes with steep drainage basins across a ~20,000-sq.-km region. Visual logging, magnetic susceptibility, X-radiography, and loss-on-ignition analysis document core stratigraphic variability; multiple radiocarbon dates provide age control. In each core, several layers of coarse-grained, mineral-rich sediment with abundant macrofossils of terrestrial plants punctuate the otherwise fine-grained, organic-rich gyttja matrix. The character of these coarse layers leads us to believe that they originated as terrestrial sediment eroded from the uplands during severe storm events. If this hypothesis is valid, the ages of these terrigenous layers correspond to the approximate dates of large storms that passed over the lakes' drainage basins. Few (<~20%) of these terrigenous layers were deposited synchronously in neighboring study lakes across this region during the Holocene, and at only one time (~1200 BP) were these layers deposited synchronously in more than half of the study lakes. The disparate ages of terrigenous layer deposition in separate lakes suggests that most storms of great intensity or duration affected localized areas. The most severe Holocene storms in this region probably were not hurricanes or other physically large storms, but rather small, high-intensity storm cells that were capable of producing devastating effects. Together, the records from these lakes suggest that at least three major periods of increased storminess occurred during the Holocene, peaking at ~2000, 6000, and between 8500-10000 calendar years before present. Preliminary spectral analyses indicate that storm frequency may follow centennial- and perhaps millenial-scale cycles.