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, northwestern Minnesota, during the Holocene are autochthonous or biogenic, delivered to the sediment-water interface on a seasonal schedule, preserved in distinct annual laminae (varves). The main allochthonous component is detrital clastic material, as measured by bulk-sediment concentrations of aluminum, sodium, potassium, titanium, and quartz, that enters the lake mostly as eolian dust. The eolian clastic influx to Elk Lake was considerably greater during the mid-Holocene (8–4 ka) than it has been for the past 4000 yr, when periods of increased eolian activity correspond to the time of the Little Ice age and the dust bowl. Geochemical records of eolian activity exhibit distinct cyclicities with dominant periodicities of 400 and 84 yr.