AN HISTORICAL GEOARCHAEOLOGICAL APPROACH TO SOURCING AN 18TH CENTURY BUILDING STONE: USE OF AQUIA CREEK SANDSTONE IN CHRIST CHURCH, LANCASTER COUNTY, VIRGINIA, USA

Historic Christ Church in Lancaster County, Virginia (1735) is one of America’s best-preserved examples of colonial Georgian architecture. Among its many architectural highlights is the beautiful stone trim that adorns the brick church’s doorways and windows. As it ages, conservation of original stone architectural elements is becoming necessary. The goal of this study is to determine the source of the exterior stones so appropriate matches can be acquired when repairs or replacement of some elements are needed. It will also help elucidate Christ Church’s construction history. We compared stone samples from Christ Church’s steps and keystones to samples taken from the famous Aquia Creek quarry on Government Island in Stafford County, Virginia that provided the stone for America’s first federal buildings (e.g., White House, Capital, Treasury). We used standard petrographic thin section analysis to compare the samples’ grain size, sorting, and mineralogy. Both stones are moderately sorted, medium sand sized, subarkose sandstones. Based on this as well as historical evidence, we suggest that the steps at the north, south, and west doors as well as the stone elements around the windows and doors of the church are made of the Cretaceous Aquia Creek Sandstone quarried on Government Island. Within the quarry, the sandstone most likely came from the upper Patapsco Formation of the Potomac Group rather than the lower Patuxent Formation. This information should be kept in mind as Aquia Creek Sandstone has a history of premature weathering and may require shorter term maintenance and longer-term replacement. Unfortunately, sea level rise in the Chesapeake Tidewater is limiting access to these quarries for replacement stone.