Collection of Detrital Muscovite at Horseshoe Farm

Ryan McAleer, USGS Research Geologist, collects detrital muscovite from 13,000-year-old sediment at Horseshoe Farm, on the South Anna River, in the epicentral area of the 2011 M5.8 earthquake.  Geochronologic age data using the using the Optically Stimulated Luminescence (OSL) method on sand grains from this sediment and other deposits throughout the Central Virginia Seismic Zone allow USGS scientists and our collaborators to correlate river terrace deposits, estimate regional deformation, and date specific paleoearthquake events that produced liquefaction fields.  Detrital muscovite ages using the ⁴⁰Ar/³⁹Ar will allow Dr. McAleer to piece together the provenance of this pile of sediment in the bed of the South Anna River, and determine if it was deposited by neotectonic uplift, or paleoclimatic forces.