Chronology of MIS 6 Laurentide Ice Sheet marginal sedimentation in southwestern Indiana, United States

Abstract The efficacy of using luminescence dating on glacial deposits is tested for a portion of the Marine Isotope Stage (MIS) 6 Laurentide Ice Sheet margin in southwestern Indiana. We assess small-aliquot quartz optically stimulated luminescence (OSL) and feldspar infrared-stimulated luminescence (IRSL) dating of glaciofluvial, glaciodeltaic, and aeolian sediments against a well-established soil stratigraphy and a cosmogenic 10 Be depth profile. Results indicate that standard blue-light OSL regenerative protocols used on MIS 2 glacial sediments in the region warrant caution when duplicated for MIS 6 sediments. Quartz OSL ages underestimate age by up to 50% compared with cosmogenic and feldspar post-IR IRSL 200 ages. Presence of unstable or hard-to-bleach OSL signal components that cannot be removed with modified preheat protocols yields unreliable data. While dates obtained using post-IR IRSL 200 protocols on feldspar are affected by partial bleaching and anomalous fading, these factors can be accounted for. Discrimination of negligible-fading small-aliquot data allowed us to obtain post-IR IRSL 200 ages between 103 ± 12 and 241 ± 28 ka. Post-IR IRSL 200 ages are mostly consistent with 10 Be depth-profile dating and stratigraphic constraints and represent a viable option to study glaciofluvial sedimentation during MIS 6 and older glaciations in the region.