GEOLOGIC TRANSECTS OF NATIONAL PARKS: THE CHESAPEAKE AND OHIO CANAL NATIONAL HISTORICAL PARK AS A TEMPLATE FOR THE BLUE RIDGE PARKWAY AND APPALACHIAN NATIONAL SCENIC TRAIL

A geologic map, professional paper, and field trip guidebook was produced for the 184.5 mile long Chesapeake and Ohio Canal National Historical Park, which extends from Washington, D.C., to Cumberland, Md., along the north shore of the Potomac River. Geologic mapping within a 2 mile wide corridor centered on the Potomac provides an opportunity to examine the geologic history of the central Appalachian region and how the canal contributed to the development of this area. Each province along the canal contains distinctive packages of rocks that influenced the character of the river and construction of the canal and towpath. Interpretation of the bedrock provides evidence of the Mesoproterozoic Grenvillian, Ordovician Taconian, Devonian Acadian, and Carboniferous Alleghanian orogenies, continental rifts in the Neoproterozoic and Mesozoic, and subsequent development of the passive margin and Coastal Plain. The canal and towpath were excavated in Quaternary flood-plain deposits and bedrock, and was locally placed in the abandoned channel of the Potomac River. The engineers used native bedrock to construct the locks, dams, and aqueducts. Culverts guided water from the Potomac River into the canal and maintained the water level as canal boats traveled from western Maryland to sea level in Washington, D.C. The geologic field trip guide follows the canal from southeast to northwest, with geologic features keyed to the mile markers along the towpath. A 1:110,000--scale map is supplemented by page-size geologic maps at ~1:60,000-scale for day excursions.

We are preparing a similar geologic map and guide for a 2 mile-wide corridor centered along the ~218 mile portion of the Blue Ridge Parkway (BRP) in Virginia. The BRP meanders across multiple Paleozoic fault blocks and provides a transect across the east and west limbs of the Blue Ridge anticlinorium and the Blue Ridge plateau and escarpment. Lessons learned from the Canal and BRP field guides could be applied to a similar geologic strip map being considered for the 2,175 mile-long Appalachian National Scenic Trail (AT). The AT extends from Maine to Georgia, and mostly follows the Blue Ridge, but locally meanders into the Valley and Ridge province en route to the glaciated northern Appalachians.