Abstract
The current understanding of Lake Warren as a proglacial lake stage in the Lake Erie basin during the last deglaciation is based on limited stratigraphic information from strandlines and a wide range of radiocarbon ages. The purpose of this study is to use ground-penetrating radar (GPR) and optically stimulated luminescence (OSL) dating to reconstruct the stratigraphy, depositional environment, and age of the Oak Openings Ridge (OOR), a former strandline of Lake Warren in northwestern Ohio. Both sedimentary exposures and >4 km of GPR data were used to demonstrate that the OOR is a barrier spit that migrated from the northeast to the southwest, and is currently blanketed by an aeolian sheet. Sediments observed in exposures show a shallowing-up sequence attributed to the retreat of proglacial lakes from the area. Corresponding GPR data reveal three distinct GPR facies. The lowermost radar facies 1 (RF1) is a sandy barrier spit platform of a lower beach face prograding across finer-grained lacustrine mud or till. Eroded into RF1 is an upper beach face of RF2, the top of which is visible in cutbank and borrow pit exposures. Overlying the RF2 beach face is uppermost unit RF3, consisting of low-relief, aeolian parabolic dunes and sand sheets. Four OSL ages from a climbing ripple sequence in RF2 average 14.2 ± 0.5 ka, consistent with an earlier published OSL age of 14.1 ± 1.0 ka (Campbell et al. in 2011) from the same unit. From earlier work, the overlying aeolian dunes (RF3) record westerly winds after formation of the OOR, and OSL dating records episodic activity from the Younger Dryas chronozone to ∼8000 years ago. The results suggest that the OOR formed in two phases. First, a barrier spit prograded into Lake Warren from the northeast. Second, parabolic sand dunes and a sand sheet formed episodically for ∼5000 years thereafter. The sediment source for the sand body is from southeast Michigan, but it is of uncertain origin.
