APPROACHING A UNIFIED BASIN-SCALE LITHOSTRATIGRAPHIC FRAMEWORK FOR THE MIDDLE TO UPPER DEVONIAN CLASTIC UNITS OF THE CENTRAL APPALACHIAN VALLEY AND RIDGE PROVINCE

Detailed outcrop investigations focused on basin analysis typically begin with an understanding of stratigraphic position, that information is provided by geologic maps; however, some Devonian units have poor or ambiguous delineation on geologic maps, especially those at the regional scale. The National Collaborative Geologic Mapping Program’s Appalachian Basin Mapping Project is tasked with geologic mapping in the Appalachian Valley and Ridge and Appalachian Plateaus provinces. One of the overarching goals of this project is to construct seamless maps across state boundaries at scales of 1:24,000 and 1:100,000. Over the last decade, targeted geologic mapping in Virginia, West Virginia, Maryland, and Pennsylvania has revealed many challenges in middle-upper Devonian siliciclastic strata that prevent seamless mapping. The formational units of interest are the Mahantango, Brallier, Scherr, Foreknobs, and Hampshire formations. Some of these issues are resolved through revisions to nomenclature and regional correlations. However, other issues occur at the intersection of geologic mapping, clastic facies models, and basin analysis, and require new data and novel approaches.

As a solution, this work aims to establish a regional lithostratigraphic framework using 3D reference sections, 1-meter resolution lidar raster imagery, and clastic facies analysis. This approach is demonstrated on the Devonian siliciclastic section in the Winchester, Cumberland, and Johnstown 30 x 60-minute quadrangles. This work represents an effort to correlate distinct lithofacies along strike for over 200km and across three state boundaries. This talk will also highlight scientific questions relating to Appalachian basin analysis, such as Paleozoic eustatic sea level, paleogeography, tectonics, depositional and provenance history, and how answers to those questions may help resolve mapping issues.

The results of this work will guide regional lithostratigraphic correlations and seamless mapping across state and quadrangle boundaries. Additionally, a unified lithostratigraphic framework supported by mapping, 3D reference sections, and other new data will serve as a reliable foundation for many types of new Appalachian basin research.