| Geologic Bedrock of Loudoun County, VA (2009) | |
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Data format: SDE Feature Class File or table name: GISDBB.GISBROW.GEOLOGY_BEDROCK_POLY Coordinate system: Lambert Conformal Conic Theme keywords: geoscientificInformation, Geology, Geologic, Bedrock, Fault, Structure, Surficial, Group, Member, Formation, Map Unit |
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Abstract:
"Bedrock" is one of four layers which collectively describe the subsurface geologic formation, structural geology and surficial deposits. "Bedrock" is the subsurface expression of the geologic formations near the ground surface as mapped by outcrops and well borings.
The geology of Loudoun County, Virginia, was mapped in 1988 through 1991 under a cooperative agreement between the U.S. Geological Survey (USGS) and the Loudoun County Department of Environmental Resources. This geologic map was compiled in 1993 from a series of detailed published and unpublished field investigations at scales of 1:12,000 and 1:24,000. Some of these same data were compiled as a digital geologic map at 1:100,000 scale (Burton and others, 1992a) and were the basis for a cost-benefit analysis of the societal value of geologic maps (Bernknopf and others, 1993).
The data was later revised and published by USGS in the Open File Report, MAP OF-99-150, GEOLOGIC MAP OF LOUDOUN COUNTY, VIRGINIA By Scott Southworth, W.C. Burton, J.S. Schindler, and A.J. Froelich1 with contributions on the geology of the Piedmont province by A.A. Drake, Jr., and R.E. Weems and an aeromagnetic survey by D.L. Daniels, W.F. Hanna, and R.E. Bracken. |
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Metadata elements shown with blue text are defined in the Federal Geographic Data Committee's (FGDC) Content Standard for Digital Geospatial Metadata (CSDGM). Elements shown with green text are defined in the ESRI Profile of the CSDGM. Elements shown with a green asterisk (*) will be automatically updated by ArcCatalog. ArcCatalog adds hints indicating which FGDC elements are mandatory; these are shown with gray text.
"Bedrock" is one of four layers which collectively describe the subsurface geologic formation, structural geology and surficial deposits. "Bedrock" is the subsurface expression of the geologic formations near the ground surface as mapped by outcrops and well borings.
The geology of Loudoun County, Virginia, was mapped in 1988 through 1991 under a cooperative agreement between the U.S. Geological Survey (USGS) and the Loudoun County Department of Environmental Resources. This geologic map was compiled in 1993 from a series of detailed published and unpublished field investigations at scales of 1:12,000 and 1:24,000. Some of these same data were compiled as a digital geologic map at 1:100,000 scale (Burton and others, 1992a) and were the basis for a cost-benefit analysis of the societal value of geologic maps (Bernknopf and others, 1993).
The data was later revised and published by USGS in the Open File Report, MAP OF-99-150, GEOLOGIC MAP OF LOUDOUN COUNTY, VIRGINIA By Scott Southworth, W.C. Burton, J.S. Schindler, and A.J. Froelich1 with contributions on the geology of the Piedmont province by A.A. Drake, Jr., and R.E. Weems and an aeromagnetic survey by D.L. Daniels, W.F. Hanna, and R.E. Bracken.
Geology was researched and compiled for use in studies of soils and groundwater, and to support the County's water resources plan.
Data are published by USGS at http://geology.er.usgs.gov/eespteam/GISLab/Search/Virginia/loudoun/index.html Files are available as ESRI shapefile and .e00 files. Data were originally prepared in Lat/Long (NAD27) and have been reprojected by the County to Virginia State Plane (North), Zone 4501, datum NAD83 HARN, US Feet. Data are stored in the corporate ArcSDE Geodatabase as a polygon feature class.
For additional information, please see the geology supplements:
GEOLOGIC MAP OF LOUDOUN COUNTY, VIRGINIA
REPORT TO ACCOMPANY MAP OF-99-150
U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY
Southworth, et. al. (1999)
and
Interpretive Guide to Geology and Groundwater in Loudoun County, VA
Loudoun County, VA, Dept. of Environmental Resources (1993)
March 2004
Every reasonable effort has been made to assure the accuracy of these data. Loudoun County, Virginia does not assume any liability arising from the use of these data. These data are provided without warranty of any kind, expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular service. Reliance on these data is at the risk of the user. These data were generated for use by Loudoun County and are available to the public. These data are intended for use at 1:2400 scale or smaller. Acknowledgement of Loudoun County would be appreciated in products derived from this data.
1 Harrison Street S.E., 2nd Floor
MS 60A
Originator, USGS, provided no accuracy assessment
Topologically Clean
Features may have been eliminated or generalized due to scale and intended use. To assist Loudoun County, Virginia in the maintenance of the data, please provide any information concerning discovered errors, omissions, or other discrepancies found in the data.
Originator, USGS, provided no accuracy assessment
Pete Chirico
USGS provide ESRI shapefiles in latitude and longitude decimal degrees and .e00 files are in UTM 18 NAD83. Using ArcToolBox, the .e00 files were projected to Virginia State Plane North, HARN, US Survey feet using the Virginia HARN correction. This was done in two-step process. First projection is from UTM to NAD 83 and then from NAD83 to HARN.
ESRI coverage format-specific items that no longer apply were deleted upon conversion to SDE Geodatabase. These items included <COVER>#, <COVER>-ID, FNODE#, TNODE#, LPOLY#, RPOLY#, LENGTH, AREA, and PERIMETER
Internal feature number.
ESRI
Bedrock Mapping unit. Type of bedrock based on formation (lithology), age, and composition (minerology).
USGS
Bedrock ID
USGS
Bedrock classification
USGS
Lithological unit of bedrock
USGS
Bedrock formation
USGS
Bedrock geologic member
USGS
Bedrock group
USGS
Depositional environment
USGS
Rock classification
USGS
Sedimentary rock types from cementation of bedrock: minerals and sediments combining
USGS
Dominant foliation
USGS
Other foliation
USGS
Metamorphic gradation
USGS
Relative age
USGS
Minerals
USGS
Grain size of individual rocks or particles in bedrock
USGS
Composition of rock or particle grains in bedrock
USGS
Fossils contained in bedrock
USGS
Color
USGS
Description of material (rock, soil, or otherwise) covering bedrock
USGS
Outcrop (exposed) condition of bedrock
USGS
Source by which feature was created or modified
Loudoun County
Not for public distribution. Internal User ID of editor creating or modifying feature.
Loudoun County
Date feature class edited or created
Loudoun County
Feature geometry.
ESRI
BE_MAP_UNIT: The type of bedrock based on formation (lithology), age, and composition (minerology).
Unit Definition Ca Antietam Quartzite (Lower Cambrian) Ccp Carbonaceous phyllite (Lower Cambrian) Cf Frederick Formation (Upper Cambrian) Ch Harpers Formation (Lower Cambrian) Cl Weverton Formation (Lower Cambrian)-- Loudoun Formation (Lower Cambrian) Clc Weverton Formation (Lower Cambrian)-- Loudoun Formation (Lower Cambrian) Ct Tomstown Formation (Lower Cambrian) Cw Weverton Formation (Lower Cambrian)-- Lower member Cwl Weverton Formation (Lower Cambrian)-- Lower member Cwm Weverton Formation (Lower Cambrian)-- Middle member Cwu Weverton Formation (Lower Cambrian)-- Upper member CZmg Graywacke CZms Schist Jd Diabase dikes and sheets (Lower Jurassic) Jdc Diabase dikes and sheets (Lower Jurassic) Jdg Diabase dikes and sheets (Lower Jurassic) Jdh Diabase dikes and sheets (Lower Jurassic) Jdl Diabase dikes and sheets (Lower Jurassic) Jhg Diabase dikes and sheets (Lower Jurassic) Jhgs Diabase dikes and sheets (Lower Jurassic) Jm Midland Formation (Lower Jurassic) Jmc Midland Formation (Lower Jurassic) Jmz Mount Zion Church Basalt (Lower Jurassic) Js Sander Basalt (Lower Jurassic) Jss Sander Basalt (Lower Jurassic) Jtr Turkey Run Formation (Lower Jurassic) JTRc Catharpin Creek Formation (Upper Triassic to Lower Jurassic) Jtrc Catharpin Creek Formation (Upper Triassic to Lower Jurassic) JTRcg Catharpin Creek Formation, Goose Creek Member JTRtm Thermally Metamorphosed Rocks (Upper Triassic and Lower Jurassic) TRbl Balls Bluff Siltstone, Leesburg Member (Upper Triassic) TRbs Balls Bluff Siltstone, Fluvial and Deltaic Sandstone and Siltstone Member (Upper Triassic) TRbsh Balls Bluff Siltstone, Lacustrine Shale and Siltstone Member (Upper Triassic) TRmp Manassas Sandstone, Poolesville Member (Upper Triassic) TRmr Manassas Sandstone, Reston Member (Upper Triassic) Ybg Biotite granite gneiss Yc Charnockite Yg Leucocratic metagranite Ygt Garnetiferous leucocratic metagranite Yhm Hornblende monzogranite gneiss Ylg Layered granitic gneiss Ymb Biotitic Marshall Metagranite Ymc Coarse-grained Marshall Metagranite Yml Pink leucocratic metagranite Yn Metanorite and metadiorite Yp Paragneiss Ypg Porphyroblastic metagranite Yt Undefined Zc Catoctin Formation (Late Proterozoic) Zcb Catoctin Formation (Late Proterozoic) Zcm Catoctin Formation (Late Proterozoic) Zcp Catoctin Formation (Late Proterozoic) Zcr Catoctin Formation (Late Proterozoic) Zcs Catoctin Formation (Late Proterozoic) Zfa Fauquier Formation (Late Proterozoic) Zfc Fauquier Formation (Late Proterozoic) Zfs Fauquier Formation (Late Proterozoic) Zmd Undefined Zrd Metarhyolite dikes (Late Proterozoic) Zrr Robertson River Igneous Suite (Late Proterozoic) Zsm Swift Run Formation (Late Proterozoic) Zsp Swift Run Formation (Late Proterozoic) Zss Swift Run Formation (Late Proterozoic
BE_UPD_SOURCE: Source by which feature class was created or modified
Source Definition 0 Undetermined 1 Legacy 2 County 3 Contract
1 Harrison Street, S.E., 2nd Floor
MS 65
Every reasonable effort has been made to assure the accuracy of these data. Loudoun County, Virginia does not assume any liability arising from the use of these data. These data are provided without warranty of any kind, expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular service. Reliance on these data is at the risk of the user.
ESRI Personal Geodatabase Feature Class
ESRI Shapefile
AutoCAD Digital Exchange File
Size limit: 4.5 GB. Visit our website at: http://www.loudoun.gov/omagi, click on "Loudoun County Mapping Documents & Order Forms." The "Forms" directory will lead you to custom & standard (countywide) data order forms. Hardcopy maps may also be available; please contact the Mapping Office Public Information Counter for more information regarding all data requests.
1 Harrison Street, S.E., 2nd Floor
MS 65