U.S. Geological Survey
2016
Detailed geologic mapping geodatabase for the Blue Ridge Parkway in Virginia
geodatabase
Online
U.S. Geological Survey
Recommended Citation: Carter, M.W., Crider, E.A., Southworth, C.S., and Aleinikoff, J.N., 2016, Detailed geologic mapping geodatabase for the Blue Ridge Parkway in Virginia with station point photographs: U.S. Geological Survey data release, http://dx.doi.org/10.5066/F7DN434F.
http://dx.doi.org/10.5066/F7DN434F
The US Geological Survey, in cooperation with the National Park Service, mapped 35 7.5-minute quadrangles, within a 2-mile-wide+ corridor centered on the Parkway, from BLRI (Blue Ridge Parkway) Mile Post (MP) 0 near Afton, Virginia southward to MP 218 at Cumberland Knob, approximately 1.3 km south of the Virginia – North Carolina State Line.
Detailed bedrock geologic mapping for this project was conducted at 1:24,000-scale by systematically traversing roads, trails, creeks, and ridges within and adjacent to the 2-mile-wide+ corridor along the 216.9-mile length of the BLRI in Virginia. Geologic data at more than 23,000 station points were collected during this project (September 2009 – February 2014), with approximately 19,500 included in the accompanying database. Station point geologic data collected included lithology, structural measurements (bedding, foliations, folds, lineations, etc), mineral resource information, and other important geologic observations. Station points at the start of this project (September 2009) were located in the field using topographic reckoning; after May 2012 stations were located using Topo Maps (latest version 1.12.1) for Apple IPad 2, model MC744LL/A. Since the start of the project, station point geologic data and locational metadata were recorded both in analog (field notebook and topographic field sheets) and digitally in ESRI ArcGIS (latest version ArcMAP 10.1).
Station point geologic data were used to identify major map units, construct contact lines between map units, identify the nature of those contacts (igneous, stratigraphic or structural), determine contact convention control (exact – located in field to within 15 meters; approximate – located to within 60 meters; inferred – located greater than 60 meters), trace structural elements (faults, fold axes, etc) across the project area, and determine fault orientation and kinematics. Geologic line work was initially drafted in the field during the course of systematic detailed mapping; line editing occurred during office compilation in Adobe Illustrator (latest version CS 4). Final editing occurred during conversion and compilation of Illustrator line work into the ArcGIS database, where it was merged with station point geologic data.
Station point geologic data, contacts and faults from previous work in the BLRI corridor were evaluated for compilation and synthesis in the BLRI mapping project. Station point geologic data compiled from previous work are referenced and marked with a “C” in the database. Compiled line work is also clearly tagged and referenced.
The BLRI cuts at an oblique angle nearly the entire width of the Blue Ridge Geologic Province in Virginia. Thus, the geology varies significantly along it’s along its 216-mile traverse. North of Roanoke (BLRI MP 115), the Blue Ridge is defined as an orogen-scale, northwest-vergent, northeast-plunging reclined anticlinorium, and from its start at MP 0 near Afton, Virginia, southward to Roanoke, the BLRI traverses the western limb of this structure. Here, rocks range in age from Mesoproterozoic to Cambrian: Mesoproterozoic orthogneisses and metamorphosed granitoid rocks of the Shenandoah massif comprise “basement” to Neoproterozoic to Cambrian mildy- to non-metamorphosed to sedimentary “cover” rocks; the BLRI crisscrosses in many places the contact between cover and basement. Mesoproterozoic basement rocks in the Shenandoah massif represent the original crust of the Laurentian (ancestral North American) continent; sedimentary cover rocks were deposited directly on this crust during extension and breakup of the Rodinian supercontinent in the Neoproterozoic to earliest Cambrian. Very locally, diabase dikes of earliest Jurassic age intrude older basement and cover sequences. These dikes were emplaced in the Blue Ridge during continental extension (rifting) and the opening of the Atlantic Ocean in the Mesozoic Era.
From MP 103.3 to MP 110.3 near Roanoke, the BLRI crosses into and out of a part of the Valley and Ridge Geologic Province. Unmetamorphosed sedimentary rocks of Cambrian to Ordovician age – mostly shale, siltstone and carbonate – occur here. These rocks were deposited in a terrestrial to shallow marine environment on the Laurentian continental margin, after extensional breakup of Rodinian supercontinent in the Neoproterozoic and earliest Cambrian, but before mid- to late-Paleozoic orogenesis.
South of Roanoke, the Blue Ridge Geologic Province quickly transitions from an anticlinorium to a stack of imbricated thrust sheets. After crossing the southern end of the Shenandoah Mesoproterozoic basement massif (MP 124.1 to MP 144.4), the BLRI enters the eastern Blue Ridge province, a fault-bounded geologic terrane comprised of high-metamorphic-grade sedimentary and volcanic rocks deposited east of the Laurentian continental margin from the Neoproterozoic to early Paleozoic. These rocks were significantly metamorphosed, deformed, and transported westward onto the Laurentian margin along major orogenic faults during Paleozoic orogenesis.
Sixty bedrock map units underlie the BLRI in Virginia. These units consist of one or more distinguishing lithologies (rock types), and are grouped into formal and informal hierarchal frameworks based on age, stratigraphy (formations-groups), and tectonogenesis. Many of these units exhibit characteristics and field relationships that are critical to our understanding of Appalachian orogenesis. Most of these units are named based on the dominant occurring lithology; other units follow formal nomenclature, some of which was developed and has been used for more than 100 years.
Oldest rocks occurring along the BLRI corridor are Mesoproterozoic orthopyroxene-bearing basement rocks of the Shenandoah massif, in the core of the Blue Ridge anticlinorium. Preliminary SHRIMP U-Pb zircon geochronology (J. N. Aleinikoff, this study) shows that these rocks can be grouped based on crystallization ages: Group I (~1.2 to 1.14 Ga) are strongly foliated orthogneisses and Group II (~1.06 to 1.0 Ga) are less deformed metagranitoids. Group I orthogneisses, which occur discontinuously from near Irish Gap (MP 37) to Cahas Overlook (MP 139), comprise 10 map units: leucogranitic gneiss (Yllg); megacrystic quartz-monzonitic gneiss (Yqg); granitic gneiss (Yg); lineated granitoid gneiss (Ylgg); garnetiferous leucogneiss (Yglg); Sandy Creek gneiss (Ysg); porphyroblastic garnet-biotite leucogranitic gneiss (Ygtg); dioritic gneiss (Ydg); Pilot gneiss (Ypg); and megacrystic granodioritic gneiss (Ygg). Group II metagranitoids, which are first encountered along the BLRI at Reeds Gap (MP 14) and occur discontinuously to Roanoke River Overlook (MP 115), comprise 8 map units: megacrystic meta-quartz monzonitoid (Yqm); massive metagranitoid (Ymgm); megacrystic metagranitoid (Ypgm); mesocratic porphyritic metagranitoid (Ygpm); metagranodioritoid (Ygdm); Vesuvius megaporphyritic metagranitoid (Yvm); quartz-feldspar leucogranitoid (Yqfm); and Peaks of Otter metagranitoid (Ypom). An additional relatively undeformed metagranitoid with a preliminary SHRIMP U-Pb zircon age of ~1.12 Ga is assigned to the Bottom Creek Suite (Ybcm), and well layered migmatitic gneiss (Ymg) near Irish Gap (MP 37) has a a preliminary SHRIMP U-Pb zircon age of ~1.05 Ga. Other rocks of Mesoproterozoic age include orthogneisses in the Fries thrust sheet between MP 139 and MP 144.5 that range in age from ~1.19 to
~1.07 Ga: biotite-muscovite leucogneiss (Ymlg); biotite granitic augen gneiss (Ybgg); blue-quartz gneiss (Ybqg); and biotite leucogneiss (Yblg). Latest Mesoproterozoic rocks include paragneiss and pegmatite (Yprg) near Porters Mountain Overlook (MP 90), and a suite of igneous intrusive nelsonites and jotunites (Yjn).
Two units, foliated metagreenstone (Zdm) and foliated metagranitoid (Zgm), locally intrude older Mesoproterozoic rocks in the core of the Blue Ridge anticlinorium. Metagreenstone is fine-grained and mafic in composition, and occur as narrow dikes and sills; metagranitoid is medium-grained and generally felsic in composition, and intrude basement rocks as small plutons, stocks, and a few narrow dikes.
On the west limb of the Blue Ridge anticlinorium, metamorphosed sedimentary and volcanic rocks of Neoproterozoic to Cambrian age crop out discontinuously along the BLRI from near Afton (MP 0) to MP 103.3, in the vicinity Roanoke Mountain (MP 120 to MP 124), to near Adney Gap (MP 136). These rocks are assigned to a formal stratigraphic sequence: Swift Run Formation; Catoctin Formation; Chilhowee Group.
Metasedimentary and meta-igneous rocks of lower Paleozoic (?) to Neoproterozoic age are assigned to the Alligator Back Formation, Lynchburg Group, and Ashe Formation. These units crop out southeast of the Red Valley fault from MP 144.5 southwestward to the North Carolina–Virginia State Line at Mile Post 216.9. Rocks assigned to the Alligator Back crop out in the Blue Ridge Parkway corridor from Mile Post 174.5 southward to the North Carolina–Virginia State Line: compositional-layered biotite-muscovite gneiss (abg); garnet-biotite-muscovite-quartz schist (abs); quartzite and quartz-rich metasandstone (abq); and marble (abm). The following lithologic map units along the BLRI corridor are correlated with Lynchburg Group formations: graphitic schist (lgs), muscovite-biotite metagraywacke (lmg), and graphite-muscovite-quartz metasandstone (lms). These rocks crop out between the Red Valley fault (Mile Post 144.5) and the Rock Castle Creek fault (Mile Post 174.5). Coarse-grained- to conglomeratic metagraywacke (acm), underlying Lynchburg Group rocks west of the Rock Castle Creek fault in the vicinity of Rakes Millpond (MP 162.3) and Rocky Knob Visitors Center (MP 169), are considered to be the lower metamorphic grade-equivalent of the higher metamorphic-grade Ashe Formation at its type section in northwestern North Carolina. Five meta-igneous lithologic map units occur as mappable bodies interlayered or intrusive into metasedimentary rocks of the Alligator Back Formation and Lynchburg Group. Altered ultramafic and ultrabasic rocks (um) occur mostly within the Lynchburg Group, but few thin bodies also occur within laminated amphibolite gneiss (aml) locally (laminated amphibolite gneiss is associated with rocks of the Alligator Back Formation). Amphibolites of the Lynchburg Group include biotite-bearing amphibolite (amb), clinozoisite-bearing amphibolite (amc) and quartz-layered amphibolite (amq).
Map units that occur beneath the Blue Ridge fault are assigned to the Valley and Ridge Province. In the BLRI corridor, these rocks are first exposed near Bearwallow Gap (MP 91) and continue southward beyond Roanoke near MP 125. Oldest formations are Shady Dolomite (Cs) and Waynesboro Formation (Cw), which regionally can be mapped in stratigraphic continuity with cover and basement rocks of the Blue Ridge anticlinorium. Conversely, nowhere in the Appalachians can rocks of the Elbrook Formation (Ce) or Conococheague Formation (Cco) be mapped in direct stratigraphic continuity with Mesoproterozoic basement rocks in the core of the Blue Ridge anticlinorium; however, they do stratigraphically overlie older Waynesboro Formation and Shady Dolomite within imbricates of the Blue Ridge fault system. Ordovician Martinsburg Formation (Omb) occurs beneath the Pulaski fault north of Roanoke River, about 0.85 km northwest of MP 108.
Paleozoic mylonite (Pzmy) is a tectonic rock unit that that occurs in high-strain fault zones in the core of the Blue Ridge anticlinorium from near Afton (MP 0) to Adney Gap (MP 136). Jurassic diabase (Jd) occurs in narrow dikes that intrude older map units, just south of Roanoke River near MP 118 and MP 125, north of James River near MP 56, and in the vicinity of Afton near MP 3 and north of MP 0.
The geologic map database for the Blue Ridge Parkway can be utilized to address numerous county and state, land-use, and environmental issues. Possible applications of this database include the study of landslide hazards, groundwater resource issues, land-use planning for growing communities, and further studies related to earthquake hazards. These data can also be used to study the close association between bedrock geology, overlying soils and surface ecology. All of these applications require accurate, concise, and user-friendly geologic map data to produce viable derivative products and to enable sound land-use decisions.
This database is NCGMP09 compliant with some modifications. These modifications include additional fields in points feature classes, including MapDescription (used by the Author for the actual map description on a printed map); RockType (used by the author to describe the rock in the field). The DescriptionofMapUnits table contains modifications to the Description field, many descriptions for rock units exceeded the standard column width and therefore the width was modified. In addition, many of those descriptions contained multiple DataSourceIDs so the notes field includes the additional data sources in the DataSource table. The RepurposedSymbols table was not completed but more information about repurposed symbols can obtained on request.
A list of the U.S. Geological Survey quadrangles used in preparation of this database is listed below with publication dates listed in parenthesis:
Arnold Valley, Virginia (1999)
Bent Mountain, Virginia (1996)
Big Islands, Virginia (1999)
Big Levels, Virginia (1999)
Buena Vista, Virginia (1999)
Callaway, Virginia (1963)
Cana, Virginia - North Carolina (1968)
Check, Virginia (1963)
Cornwall, Virginia (1967)
Cumberland Knob, North Carolina - Virginia (1965)
Elliston, Virginia (1963)
Endicott, virginia (1967)
Fancy Gap, Virginia (1968)
Floyd, Virginia (1968)
Garden city, Virginia (1999)
Hardy, Virginia (1963)
Lambsburg, Virginia - North Carolina (1965)
Laurel Fork, Virginia (1968)
Massies Mill, Virginia (1999)
Meadows of Dan, Virginia (1985)
Montebello, Virginia (1999)
Montvale, Virginia (1967)
Peaks of Otter, Virginia (1967)
Roanoke, Virginia (1963)
Sedalia, Virginia (1965)
Sherando, Virginia (unknown)
Snowden, Virginia (1999)
Stewartsville, Virginia (1963)
Vesuvius, Virginia (1965)
Villamont, Virginia (1999)
Waynesboro East, Virginia (1997)
Waynesboro West, Virginia (1973)
Willis, Virginia (1968)
Woodlawn, Virginia (1965)
Woolwine, Virginia (1968)
2009
2014
ground condition
None planned
-80.944912058
-78.83821867
38.067616116
36.523979729
None
Alligator Back Formation
Ashe Formation
Lynchburg Group
Antietam Formation
Ervin
Formation
Hampton Formation
Harpers Formation
Conococheague Formation
Chilhowee Group
Weverton Formation
Elbrook Formation
Shady Dolomite
Wayneboro Formation
Unicoi Formation
Martinsburg Formation
Bottom Creek Metagranitoid Suite
Mesoproterozoic gneisses of the Fries Thrust Sheet
Pilot Gneiss
Sandy Creek Gneiss
Crossnore Plutonic Suite
Swift Run Formation
Peaks of Otter Metagranitoid
Geology
Bedrock
Thrust Fault
Normal Fault
Reverse Fault
Folds
Gneiss
Granite
Metagranitoid
Carbonate
Diabase
Structure
Metabasalt
USGS Metadata Identifier
USGS:56ce06f6e4b0b1892d9f0e89
None
Blue Ridge Parkway
Virginia
North Carolina
Waynesboro
Humpback Rocks Visitor Center
Greenstone Trail
Ravens Roost
Humpback Mountain
Sherando Lake
Bald Mountain
Twenty Minute Cliff
Crabtree Faults
Tye River Gap
Tye River
Wigwarm Falls
Yankee Horse Ridge
Irish Gap
George Washington National Forest
Whites Gap Overlook
Indian Gap
Buena Vista
Bluff Mountain
Otter Creek
James River
Big Island
James River Visitor Center and Canal
Petites Gap
Terrapin Mountain
Onion Mountain Overlook
Fallingwater Cascades
Peaks of Otter Visitor Center
Sharp Top
Bearwallow Gap
Purgatory Overlook
Powell Gap
Jefferson National Forest
Blackhorse Gap
Great Valley Overlook
N&W Railroad Overlook
Roanoke River Gorge
Roanoke River
Roanoke Mountain
Virginia Explore Park and Visitor Center
Staunton River
Roanoke Valley Overlook
Adney Gap
Poor Mountain
Devils Backbone Overlook
Rakes Millpond
Sugarloaf Mountain
The Saddle
Rocky Knob
Rocky Knob Visitor Center
Mabry Hill
Meadows of Dan
Groundhog Mountain
Puckett Cabin
Volunteer Gap
Orchard Gap
Fancy Gap
Pipers Gap
Blue Ridge Music Center Visitor Center
Fox Hunters Paradise
Cumberland Knob
Stone Mountain State Park
Doughton Park
Air Bellows Gap
Bluff Mountain
Peach Bottom Mountain
Laurel Springs
Northwest Trading Post
Jumpinoff Rock
Glendale Springs
Mount Jefferson State Park
The Lump
Benge Gap
E.B. Jeffress Park
Deep Gap
Daniel Boone's Trace
Blowing Rock
Moses H. Cone Memorial Park and Visitor Center
Price Lake
Watauga River
Julian Price Memorial Park
Grandfather Mountain State Park
Grandfather Mountain
Beacon Heights
Pisgah National Forest
Flat Rock
Linville
Lineville River
Pineola
Linville Falls Visitor Center
Crossnore
Linville Falls
Hawksbill Mountain
Table Rock Mountain
Chestoa View
Bear Den
McKinney Gap
Gillespie Gap
Overmountain Victory Nation Historic Trail
Woodlaw
Museum of North Carolina Minerals Visitor Center
Little Switzerland
Crabtree Falls
Buck Creek Gap
Mount Mitchell
Mount Mitchell State Park
Green Knob
Bear Mountain Gap
Graggy Dome
Beetree Gap
Swannanoa River
Craggy Gardens Visitor Center
Bull Gap
Z.B. Vance Birthplace
Craven Gap
Ashville
Oteen
Blue Ridge Park Visitor Center and Park Headquarters
Skyland
Biltmore Estate
North Carolina Arboretum
Lake Powhaten
Hominy Creek
Mount Pisgah
Elk Pasture Gap
Wagon Road Gap
Cold Mountain
Tunnel Gap
Looking Glass Rock Overlook
Graveyard Fields
Devils Courthouse
Beech Gap
Wayneville
Richland Balsam
Nantahala National Forest
Balsam Gap
Waterrock Knob Visitor Center
Cherokee Indian Reservation
Wrights Creek
Southern End
Oconalufte Visitor Center
Big Witch Gap
Cherokee
Ervin
None
Early Paleozoic
Paleozoic
Neoproterozoic
Cambrian
Jurassic
Mesoproterozoic
None
None. Acknowledgment of the U.S. Geological Survey would be appreciated in products derived from these data. Although software enables the user to display images at various scales, map data in this report should not be used at scales greater than 1:24,000
U.S. Geological Survey, Eastern Geology and Paleoclimate Science Center
Mark W Carter
Research Geologist
mailing address
Mail Stop 926A, 12201 Sunrise Valley Dr
Reston
VA
20192
United States of America
703-648-6910
703-648-6953
mcarter@usgs.gov
Field Work and Compilation: Mark W. Carter (2006-2015)
GIS and Cartography: E. Allen Crider Jr (2011-2015)
Environment as of Metadata Creation: Microsoft Windows 7 Version 6.1 (Build 7601) Service Pack 1; Esri ArcGIS 10.1 (Build 3035) Service Pack N/A (Build N/A)
Geologic contacts and information were garnered from 1:24,000-scale mapping of geologic material based on observation from fieldwork, previously published geologic maps, and unpublished geologic data in the region. The geologic information might change if additional outcrops are discovered or exposed as the natural land changes, or as the result of development, or advances in scientific research are made. The features in the database
are not based on legal parcels or definitions.
These data are believed to be logically consistent, though no tests were performed. Geometry is topologically clean.
Data set is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details.
The data were created on a USGS 7.5-minute topographic map at 1:24,000 scale. Therefore, the horizontal accuracy is assumed to be within National Map Accuracy Standards, with a horizontal accuracy of 45.6 feet at the 95% confidence level.
The data were delineated on a USGS 7.5-minute topographic map at 1:24,000 scale. Therefore, the vertical accuracy is assumed to be within National Map Accuracy Standards, with a vertical accuracy of 11.9 feet at the 95% confidence level.
Process description is provided individually for each dataset with this geodatabase.
Unknown
This dataset collectively consists of 7 GIS data files and a saved topology layer. The data consist of point, line, and polygonal feature classes in an ESRI geodatabase. For more detailed information, including explicit feature counts, etc. please see the metadata records for the individual files.
Universal Transverse Mercator
17
0.9996
-81.0
0.0
500000.0
0.0
coordinate pair
0.6096
0.6096
Meter
D_North_American_1927
Clarke_1866
6378206.4
294.9786982
Entity and attribute information is provided individually for each dataset within this geodatabase.
The entity and attribute information was generated by the individual and/or agency identified as the originator of the data set. Please review the rest of the metadata record for additional details and information.
U.S. Geological Survey - ScienceBase
mailing address
Denver Federal Center, Building 810, Mail Stop 302
Denver
CO
80225
United States of America
1-888-275-8747
Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also contains copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner whenever applicable. The data have been approved for release and publication by the U.S. Geological Survey (USGS). Although the data have been subjected to rigorous review and are substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, the data are released on the condition that neither the USGS nor the U.S. Government may be held liable for any damages resulting from authorized or unauthorized use. Although the data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and/or contained herein. Users of the data are advised to read all metadata and associated documentation thoroughly to understand appropriate use and data limitations.
Geodatabase (.gdb)
http://dx.doi.org/10.5066/F7DN434F
None. No fees are applicable for obtaining the data set.
20200819
Ernest A Crider
U.S. Geological Survey, Eastern Geology and Paleoclimate Science Center
Geologist
mailing address
Mail Stop 926A, 12201 Sunrise Valley Dr
Reston
VA
20192
United States of America
703-648-6906
703-648-6953
ecrider@usgs.gov
FGDC Content Standard for Digital Geospatial Metadata
FGDC-STD-001-1998
local time