LAST GLACIAL MAXIMUM AND LATE GLACIAL EOLIAN SAND ACTIVITY, EAST FORK WHITE RIVER BASIN, INDIANA, USA

The chronology of late Pleistocene and Holocene eolian sand activity in the midcontinent provides important insight into the timing of paleoenvironmental change and associated surface processes. In the southern Great Lakes region, numerous studies have documented dune activity during the late glacial period, between ca. 14 and 11 ka, related to several factors, including glacial lake drainage, degradation of permafrost, and changes in vegetation composition having no modern analog. Near the limit of Wisconsin Episode glaciation in south-central Indiana, eolian sand deposits are found on the eastern edge of outwash plains in the East Fork White River (EFWR) basin and provide an opportunity to test causal mechanisms for eolian sand activity during the late glacial and last glacial maximum (LGM). We present 18 OSL ages from eolian sand and three radiocarbon ages on gastropod shells within sub-dune loess and intra-dune silt units which document two phases of eolian sand activity. The first phase, between 25.0 and 18.5 ka, records deflation from an active outwash plain filling the EFWR valley during and after the local LGM, and agrees well with the chronology of Huron-Erie Lobe glacial advance into and out of the EFWR drainage basin. The second phase, between 15.9 and 11.3 ka, records reworking of older eolian sand and outwash during a period of no-analog vegetation during the Bolling-Allerod/Younger Dryas and is in general agreement with the timing of dune activity from previous studies to the north. Late glacial eolian sand deposits are significantly thinner (ca. 3 m) than those of LGM age (ca. 10 m). Late glacial dunes north of the glacial limit are isolated and overlie loess or till, whereas late glacial eolian sand south of the limit drapes existing LGM dunes. The spread in OSL ages from multiple samples within individual dunes and age differences between closely spaced dunes prohibits distinction of dune activity between the Bolling-Allerod and Younger Dryas. We hypothesize this spread is a result of the luminescence properties of quartz sand of Huron-Erie Lobe provenance. Given the latitude (south of 39.5° N) of late glacial (ca. 16 to 11 ka) eolian sand and distance from the concurrent ice margin (>500 km), an increase in sediment availability due to no-analog vegetation change was likely the controlling factor for dune activity.