EVIDENCE OF FIRE ACTIVITY, LANDSLIDES, AND ALLUVIAL FAN CONSTRUCTION DURING THE MID-HOLOCENE IN NORTH-CENTRAL PENNSYLVANIA

This poster details the results of a limited investigation conducted prior to a bank stabilization project on Mill Creek, Tioga County, Pennsylvania. A 4.5 m high, right-bank exposure, immediately downstream of the confluence of Cabin Run and Mill Creek, was actively eroding and threatening a portion of Mill Creek Road. A bank stabilization project including grading and the placement of riprap was completed in 2017. Investigation of the bank exposure prior to the restoration project included a description of the stratigraphy and collection of sediment and charcoal samples. The results of the field and laboratory investigations suggests that the eroding landform is a remnant of a small alluvial fan deposited approximately 5,000 cal yr B.P. The presence of wood charcoal in fan deposits and the date ranges provided by radiocarbon dating in the exposure on Mill Creek are consistent with regional research that indicates a substantial period of severe drought during the mid-Holocene characterized by fire activity. A combination of fine-grained glacio-lacustrine deposits on hillslopes, possible reduction in tree cover, and changes in regional rainfall patterns may be responsible for a period of slope instability and the production of mass movement events.