TRACKING CLIMATE CHANGE IN OHIO THROUGHOUT THE LAST TERMINATION: A NETWORK OF PALEOBASINS DATING TO C. 16,000 14C YRS BP

Data from the North American Midwest documenting the Last Termination remain scarce, but recent work has identified a network of ~25 closed basin sites throughout Ohio that help fill this data gap. Preliminary analyses, including loss-on-ignition (LOI), magnetic susceptibility, and radiocarbon dating control from 1-3 horizons, show that 1) the basal ages in multiple sites range from 14,660 ±83 to 16,400 ±170 ¹⁴C yrs BP and 2) these sites track both local conditions and regional climatic forcing.

The sites within this network fall into four spatially controlled areas. The first cluster, located on the southern half of a north-south trending interlobate area in west-central Ohio, contains site 0201 – this is currently the most studied paleobasin of the network. The record therein shows a sudden increase in organic and algal productivity at 13,390 ±280 ¹⁴C yrs BP after deposition of a thick (~3 m) sequence of loess. Local biota flourish due to an apparent warming event at this time, marking the largest environmental shift record in this sector. The second cluster lies in the till plains of western Ohio, where wind-blown silt contributes to sedimentation rates so high that most paleobasins are filled prior to c. 13,000 ¹⁴C yrs BP. The third cluster is located in the northwest portion of the interlobate complex. These sites are generally younger than other areas and lack both the thick loess package and strong warming indications. The fourth cluster is in the uplands of northeastern Ohio, where loess input ceases c. 12,740 ±100 ¹⁴C yrs BP, but the timing of punctuated LOI increases range from c. 11,350 to 12,740 ±100 ¹⁴C yrs BP between local sites.

This reconnaissance work shows that the onset of deglaciation and ice sheet recession occurred before 16,400 ±170 ¹⁴C yrs BP at the southwestern portion of the network, and rapidly progressed northward. Subsequently, high eolian sedimentation prevailed in a sparsely vegetated, periglacial terrain. Most sites then transitioned into shallow lakes or bogs and completely infilled by early Holocene. Our current dating resolution and variant proxy curves for these sites do not yet show a single event at all sites, but rather increases in biological activity appear to have crossed local thresholds. Thus, the timing and nature of Last Termination warming remains open in these regional records.