227-9 Ice-marginal environments of the Illinoian and Wisconsinan ice sheets: facies analysis of lacustrine sedimentary exposures in southwestern Ohio, USA

Session: Recent Advances in Glacial Geology, Geomorphology, and Chronology (Posters)

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Abstract:

Continental ice margins fluctuate substantially, even within a single glacial episode, in response to environmental changes. The Laurentide Ice Sheet covered northeastern North America multiple times during the Pleistocene, but the relatively small number of exposed, well-preserved pre-Wisconsinan (LGM) ice-marginal deposits limits our ability to study margin fluctuations within earlier glaciations. In southern Ohio and Kentucky, facies in drill cores and scattered exposures indicate the formation and draining of large lakes where the Illinoian (~300-130 ka) ice sheet dammed and rearranged the Ohio River drainage network. Here we present detailed measured sections and geochemical data from two Ohio outcrops that contain similar sedimentary sequences including lake deposits.  

Paddison Run, a tributary of the Little Miami River, exposes a ~10 m section of gravels, laminated sandy clays, and sandy diamicts. These are interpreted as outwash gravels overlain by 1.5 m of lacustrine clays and capped by a sandy till, reflecting an advance of the ice margin. Prior analyses on wood from within the till indicate ages exceeding the radiocarbon limit, leading to an Illinoian age assignment. In this interpretation, Paddison Run would have drained to a large ice-dammed lake in what is now the Little Miami River valley. 

Bill’s Creek, a tributary of the Great Miami River, exposes a similar 10-m section of gravels, lake sediments, and till. The outcrop is cut into drift near a Wisconsinan recessional margin. Unlike Paddison Run, lake sediments here represent 20 cm of section, exhibiting shallow-water features including ripple marks and mud drapes. These characteristics are consistent with a small lake in a ponded tributary to the Great Miami valley during an ice margin advance. However, there is no direct age control on this section, and the sediments here are indurated, potentially allowing a pre-Wisconsinan origin. 

To directly constrain the ages of the two sections, we collected quartz rich samples for cosmogenic and luminescence dating. To evaluate provenance and environment of the lake sediments, we logged and sampled each section at high resolution for facies interpretation, XRF elemental analyses, and grain size distribution. Specifically, we aim to determine if the lake sediments at each site were sourced primarily from the ice margin or from impoundment of streams that flowed toward the margin, with implications for drainage reconfiguration during ice advances. 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-11039

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