SOIL GEOMORPHOLOGY OF THE MILLSTONE SITE (36EL204) ALLEGHENY NATIONAL FOREST, ELK COUNTY, PENNSYLVANIA

The Millstone Site (36EL204) is located along the Clarion River, a 6^th order stream that drains a large portion of the unglaciated high plateau region of northwestern Pennsylvania. Archaeological excavations conducted by the USDA Forest Service in 2007 exposed 180 cm of alluvial soils within a narrow T1 terrace along the northern bank of the Clarion River. Initial interpretations of the soils and sediments suggested that lower half of the soil profile represents sediments that predate the Late Pleistocene Younger Drayas stadial. Two bulk soil AMS C14 dates of 11,370 ±40 RCY BP and 19,010 ±90 RCY BP support this initial interpretation. However, the accumulated experience of archaeologists working in Pennsylvania’s alluvial settings holds that basal gravels usually represent Late Pleistocene to Early Holocene lateral accretion followed by a fining upward sequence that is entirely Holocene in age. The lack of a second, post-Younger Dryas fining upward sequence at the Millstone site questions the validity of the AMS dates and initial age interpretations. Additional archaeological excavations in 2010 examined the genetic relationships between soil formation at the Millstone Site and the development of landforms within the river valley. Preliminary data suggests that the reported AMS dates may be older than the true age of sedimentation due to the presence of radiometrically dead carbon in the form coal.