OLD ROCKS, NEW DATA: COSMOGENIC 10BE ANALYSIS OF A RELICT PERIGLACIAL BOULDER FIELD, HICKORY RUN STATE PARK, PENNSYLVANIA
Here we present measurements of 10Be from Hickory Run boulder field, a 500 meter-long openwork of sandstone boulders immediately south of the LGM boundary near Kidder, PA. One of the most visited, enigmatic periglacial landforms, this block stream is notable for its size (~70,000m2, roughly 550x150m), flatness (<1°), and the heterogeneity of relative weathering intensity of boulders within it. We sampled boulders (n=53) in transects across the Hickory Run boulder field and into the adjacent forest to constrain the exposure age of the rock surfaces and to test whether or not there are spatial trends in isotopic concentration downfield, implying a sense of transport from outcrops upslope. Initial data at the southern end of the field suggest that Hickory Run is a significantly older than previously thought, with boulder ages ranging from 200 to 400ky indicating clearly that the field has been extant through the last several glaciations. Measurements of the remaining boulders are in progress.