Blue Ridge and Inner Piedmont Geologic Mapping

Science Center Objects

The Blue Ridge and Inner Piedmont Geologic Mapping Task (BRIP) is the western focus of geologic mapping and framework studies of the Piedmont and Blue Ridge Project. BRIP will conduct modern geologic mapping and geologic framework studies in the Wytheville, Hickory and Boone 30x60-min. sheets. Collectively, the objectives of BRIP are to (1) characterize the geologic framework of the Blue Ridge and Inner Piedmont; (2) produce detailed geologic maps (1:24,000 and 1:100,000) and geodatabases; (3) provide framework data to aid in the assessment of natural resources: surface and ground water, strategic and industrial minerals, and aggregate; (4) understand and recognize potential natural hazards; (5) refine the tectonic evolution Blue Ridge and Inner Piedmont terranes; and (6) apply advanced technology to resolve geologic problems. These objectives will be completed through a collaborative approach with FEDMAP, STATEMAP and EDMAP partners.

Statement of the Problem

The Blue Ridge and Inner Piedmont of southwestern Virginia, northeastern Tennessee, and northwestern to central North Carolina (Figure 1) is covered by reconnaissance-scale geologic maps (≤1:250,000 scale) including state geologic maps, and a few detailed studies (King and Ferguson, 1960; Bryant and Reed, 1970); however, most of these maps are over 25 years old and lack modern U-Pb geochronology, a critical tool for resolving and quantifying ages of crystalline units in complex terranes (e.g., Tollo and others, 2017).  Regionally, there are many inconsistencies between existing maps and at state borders including mismatched contacts, faults and units.  For example, state geologic maps of Virginia (1993) and North Carolina (1985) interpret the contact of the eastern Blue Ridge against Mesoproterozoic rocks as either a stratigraphic unconformity or a fault, respectively.  In the Inner Piedmont, SHRIMP U-Pb detrital zircon data established that a large part of the belt is late Silurian to Devonian metasediments intruded by Devonian to Mississippian granitoids (Bream et al. 2004; Merschat et al., 2010), which is in contrast to Precambrian to early Cambrian ages previously assigned to the rocks (e.g., Rankin et al., 1972; State Geologic of NC, 1985; Goldsmith et al., 1988). 

Natural resources are abundant throughout this area. The Silurian to Devonian rocks roughly correspond to a belt of high rare earth element-bearing minerals in the Inner Piedmont (Shah et al. 2017).   Surface and ground water resources supply the Lenoir-Hickory and Statesville-Mooresville micropolitan areas, and the Charlotte metropolitan statistical area with over 2.4 million people (https://www.census.gov).  Slope stability, radon and groundwater contaminants represent some of the geologic natural hazards that affect the Blue Ridge and Inner Piedmont (Ayotte et al., 2011; Bradley and Campbell, 2012). These natural resources are known, but poorly mapped.  Naturally occurring radon and contaminants in groundwater are loosely correlated with tectonic units or contacts.  Modern detailed geologic mapping and framework studies are needed to better assess the mineral resources (especially strategic minerals) and identify the source of radon and other groundwater contaminants.

The Blue Ridge-Inner Piedmont Geologic Mapping Task (BRIP) aims to conduct geologic mapping and framework analyses in the Blue Ridge and Inner Piedmont  that will address (1) areas that have only been examined at a reconnaissance scale (1:250,000 scale or smaller); (2) reconcile geologic problems between state borders and other small-scale maps; (3) regional correlation of map units and structures; (4) areas with important societal relevance:  surface and groundwater resources, mineral resources (strategic and industrial minerals and aggregate) geologic hazards, infrastructure, and energy resources; (5) improve the understanding of the tectonic history; and (6) apply advanced technology to resolve geologic problems.  The outcome will be a seamless geologic map across the Blue Ridge and Inner Piedmont that will better reconcile geology across state borders, resolve regional- and orogen-scale correlation of map units (formations), structures and other features, promote the mitigation of geologic hazards, aid in land use planning, surface and groundwater studies, identify possible new mineral (critical or industrial) and aggregate deposits, and provide suitable data to help build 3D geologic models (GOALS #1 and #3; Brock et al., 2018).

Strategy and Approach

A cooperative approach between FEDMAP, STATEMAP and EDMAP partners is planned for the success of BRIP and is in accord with the NCGMP goals (GOAL # 1; Brock et al., 2018).  With cooperative partners, BRIP will complete an initial stage of scoping, compilation and assessment of existing mapping to identify areas where additional mapping is needed to resolve problems.  For Phase 1 objectives, Wytheville and Hickory sheets, existing FEDMAP, STATEMAP and EDMAP project maps (published and unpublish) will comprise “cornerstone” maps.  New 1:24,000 scale mapping will extend away from these cornerstones and use optimized digital field-based technologies to collect data and complete the modern geologic maps (Goal #2; Brock et al., 2018).  Other areas will be completed through cooperation with EDMAP partners (University of Kentucky, Appalachian State University).  Initial geochronology and geochemistry targets will be identified, collected, and analyzed, followed by additional targets identified during mapping.    

 

 

References Cited

Ayotte, J.D., Gronberg, J.M., and Apodaca, L.E. 2011, Trace elements and radon in groundwater across the United States, 1992–2003:  U.S. Geological Survey Scientific Investigations Report 2011–5059, 115 p.

Brock et al., 2018 in review, The 2018–2030 U.S. Geological Survey National Cooperative Geologic Mapping Program Decadal Strategic Plan:  Renewing the National Cooperative Geologic Mapping Program as the Nation’s Authoritative Source for Modern Fundamental Geologic Knowledge:  U.S. Geological Survey, unpublished administrative report, 15 p. 

Bradley, P.J., and Campbell, T., 2012, Areas of relative susceptibility to elevated radon in groundwater in North Carolina:  North Carolina Geological Survey, Preliminary Draft.

Bream, B.R., Hatcher, R.D., Jr., Miller, C.F., and Fullagar, P.D., 2004, Detrital zircon ages and Nd isotopic data from the southern Appalachian crystalline core, Georgia, South Carolina, North Carolina, and Tennessee:  New provenance constraints for Laurentian margin paragneisses, in Tollo, R.P., Corriveau, L., McLelland, J., and Bartholomew, M.J., eds., Proterozoic evolution of the Grenville orogen in North America:  Geological Society of America Memoir 197, p. 459-475.

Bryant B., and Reed, J.C., Jr., 1970, Geology of the Grandfather Mountain window and vicinity, North Carolina and Tennessee:  U.S. Geological Survey Profession Paper 615, 190 p.

Goldsmith, R., Milton, D.J., and Horton, J.W., Jr., 1988, Geologic Map of the Charlotte 1-degree × 2-degree quadrangle, North Carolina and South Carolina: U.S. Geological Survey Map I-1251-E, scale 1:250,000.

King, P.B., and Ferguson, H.W., 1960, Geology of northeasternmost Tennessee: U.S. Geological Survey Professional Paper 311, 136 p.

Merschat, A.J., Hatcher, R.D., Jr., Bream, B.R., Miller, C.F., Byars, H.E., Gatewood, M.P., and Wooden, J.L., 2010, Detrital zircon geochronology and provenance of southern Appalachian Blue Ridge and Inner Piedmont crystalline terranes, in Tollo, R.P., Bartholomew, M.J., Hibbard, J.P., and Karabinos, P.M., eds., From Rodinia to Pangea:  The Lithotectonic Record of the Appalachian Region:  Geological Society of America Memoir 206, p. 661-699.

North Carolina Geological Survey, 1985, Geologic Map of North Carolina: Raleigh, North Carolina Department of Natural Resources and Community Development, Division of Land Resources, scale 1:500,000.

Rankin, D.W., Espenshade, G.H., and Neuman, R.B., 1972, Geologic map of the west half of the Winston–Salem quadrangle, North Carolina, Virginia, and Tennessee:  U.S. Geological Survey Miscellaneous Geologic Investigations Map I–709–A, Scale 1:250,000.

Schulz, K.J., DeYoung, J.H., Jr., Seal, R.R., II, and Bradley, D.C., eds., 2017, Critical mineral resources of the United States—Economic and environmental geology and prospects for future supply: U.S. Geological Survey Professional Paper 1802, 797 p., https://doi.org/10.3133/pp1802.

Shah, A.K., Bern, C.R., Van Gosen, B.S., Daniels, D.L., Benzel, W.M., Budahn, J.R., Ellefsen, K.J., Karst, A., and Davis, R., 2017, Rare earth mineral potential in the southeastern U.S. Coastal Plain from integrated geophysical, geochemical, and geological approaches:  Geological Society of America Bulletin, v. 129, p. 1140–1157, doi:10.1130/B31481.1

Tollo, R.P., Aleinikoff, J.N., Dickin, A.P., Radwany, M.S., Southworth, C.S., and Fanning, C.M., 2017, Petrology and geochronology of the Mesoproterozoic basement of the Mount Rogers area of southwestern Virginia and northwestern North Carolina: Implications for the Precambrian tectonic evolution of the southern Blue Ridge Province: American Journal of Science, v. 317, p. 251–337, https://doi.org/10.2475/03.2017.01.

Virginia Division of Mineral Resources, Geologic Map of Virginia, 1993: Virginia Division of Mineral Resources, scale 1:500,000.