MAPPING GEOMORPHIC SURFACES ALONG THE WESTERN FLANK OF THE BLUE RIDGE IN CENTRAL MARYLAND: AN INTEGRATED APPROACH

Good management of soil resources, shallow, unconsolidated aquifers and forest lands is possible with the proper interpretation of soil survey information and geologic data and is vital in a world now facing rapid global environmental change. Recent field data have been compared to available digital soil survey information and bedrock lithostratigraphic maps for a portion of the western flank of the Blue Ridge in Washington County, Maryland. A comparison of recent surficial exposures including distinct differences in soil and matrix color, lack of grain sorting and bedding, clast weathering criteria, and topographic expression allows relative ages to be assigned to several geomorphic surfaces. Analysis has revealed at least 3 distinct surfaces that correlate to a complex, multiple-age landscape mosaic and suggest colluvial processes were responsible for deposition in a paleoperiglacial environment.

Through the creation of digital surficial geologic maps at a scale of 1:12,000 and spatial analysis techniques within a GIS environment, a comprehensive analysis of landscape topography can be developed. Breaks in topography both in the field and on maps show sedimentological and geomorphic evidence of discontinuous younger fans developed over much older, truncated, colluvial fans or aprons. Surface streams in some reaches have incised through the fans producing an even younger alluvial environment that has exposed older colluvial materials in several localities. Field mapping and computer analysis reveal new information on the geomorphic history of this region as well as refine and strengthen previously published information for central Maryland and the surrounding Mid-Atlantic region.