EARLY WISCONSINAN (?) EOLIAN ACTIVITY ALONG THE OHIO RIVER IN SOUTHWESTERN INDIANA

The strata and sediments of morphologically distinct features exposed in a sand quarry in Spencer County, Indiana support earlier interpretations that the ridges along the eastern valley wall of Little Pigeon Creek (a part of the Ohio River valley) are silt capped sand dunes (Ray, 1965) and indicate multiple episodes of deposition. Five informal units were identified in the highwall of the quarry and in the subsurface using sediment cores and Ground Penetrating Radar. The five units are interpreted as (from the oldest to youngest): Unit 0- Lacustrine silt; Unit 1- Eolian interbedded yellow and brown silt (loess) capped by a weak paleosol; Unit 2- Eolian cross bedded fine sand interbedded with coarse eolian silt (loess); Unit 3- Eolian silt (loess) with a weakly developed paleosol; Unit 4- Interbedded eolian sand and silt with modern surface soil. Changes in lithology, sediment, and bedding structures indicate five episodes of deposition. Sharp contacts between the units with limited pedogenic influence indicate relatively short-lived unconformities. The development of incipient paleosols at the tops of Units 1 and 3 indicates multiple relatively short-lived depositional hiatuses where weathering rates outpaced deposition. An AMS Radiocarbon age date (Beta-217287) on organic material collected from the lower 20 cm of Unit 2 was older than 46,000 years BP (dead). SEM images of the dated material show there is no ancient fossil material (coal). Thus, the sample's age indicates an episode of eolian activity sometime before the onset of MIS 3, or reworking of older material (pre-Wisconsinan) into discrete beds during the terminal Pleistocene.