RATES, TIMING, AND CYCLICITY OF HOLOCENE EOLIAN ACTIVITY IN NORTH-CENTRAL UNITED-STATES - EVIDENCE FROM VARVED LAKE-SEDIMENTS

Most of the sediment components that accumulated in Elk Lake, northwes tern Minnesota, during the Holocene are autochthonous or biogenic, del ivered to the sediment-mater interface on a seasonal schedule, preserv ed in distinct annual laminae (varves), The main allochthonous compone nt is detrital clastic material, as measured by bulk-sediment concentr ations of aluminum, sodium, potassium, titanium, and quartz, that ente rs the lake mostly as eolian dust, The eolian clastic influx to Elk La ke was considerably greater during the mid-Holocene (8-4 ka) than it h as been for the past 4000 yr, when periods of increased eolian activit y correspond to the time of the Little Ice Age and the dust bowl, Geoc hemical records of eolian activity exhibit distinct cyclicities with d ominant periodicities of 400 and 84 yr.