Fig. 1.

Concentrations of magnetic grains and microspherules in stratigraphic sections from seven sites across North America showing no evidence for enhanced levels uniquely associated with the Younger Dryas boundary (YDB). Microspherule concentrations are not shown for Paw Paw Cove, Topper, and Shawnee-Minisink because no microspherules were recovered from these sites. Dates are shown in calendar years BP as age estimates approximated by stratigraphic correlation (dates preceded by ∼) or as radiocarbon dates (dates with error estimates).