| Geologic Surficial Deposits of Loudoun County, VA (2009) | |
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Data format: SDE Feature Class File or table name: GISDBB.GISBROW.GEOLOGY_SURFICIAL_POLY Coordinate system: Lambert Conformal Conic Theme keywords: geoscientificInformation, Geology, Geologic, Bedrock, Fault, Structure, Surficial, Surface Deposit, Sinkhole, Alluvium, Colluvium, Lag Gravel, Terrace |
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Abstract:
"Surficial" is one of four layers which collectively describe the subsurface geologic formation, structural geology and surficial deposits. "Surficial" is the mapping overlying surficial deposits, or the surface deposits covering bedrock layers.
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 This geologic map was compiled in 1993 from a series of detailed published and unpublished field investigations at scales of 1:12,000 and 1:24,000.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.
"Surficial" is one of four layers which collectively describe the subsurface geologic formation, structural geology and surficial deposits. "Surficial" is the mapping overlying surficial deposits, or the surface deposits covering bedrock layers.
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. Futhermore, some fields were deleted that contained no data or were not logically relevant to the geology theme, SURFICIAL. These items included SU_FORMATION, SU_MEMBER, SU_GROUP, SU_ROCK_CLASS, SU_FOLIA, SU_META_GRADE, SU_FOSSIL and SU_COLOR.
Internal feature number.
ESRI
Surficial
USGS
Lithologic unit of deposit (type of sediment deposit)
USGS
No for public distribution. Internal User ID of editor creating or modifying feature class.
Loudoun County
ID code for Surficial mapping unit symbol (SU_MAP_UNIT)
USGS
Relative age
USGS
Types of minerals in deposits
USGS
Lithologic chemistry
USGS
Possible weathering?
USGS
Date feature class created or modified
Loudoun County
Source which created or modified feature class
Loudoun County
Surficial mapping unit symbol. Type of suface deposit based on formation (lithology), age, and composition (minerology)
USGS
Feature geometry.
ESRI
SU_MAP_UNIT: Surficial Mapping unit. Surficial Mapping unit. Type of suface deposit based on formation and composition.
Unit Definition Qal Alluvium (Holocene) Qc Colluvium (Holocene and Pleistocene?) Qlg Lag gravel (Holocene and Pleistocene?) Qt Alluvial Terrace (low level) QTt Alluvial Terrace (intermediate and high level) sink Sinkhole water Surface water body
SU_UPD_SOURCE: Source which created or modified feature class.
Source Definition 0 Undetermined 1 Legacy 2 County 3 Contract
SU_ID: ID code for Surficial mapping unit symbol (SU_MAP_UNIT)
Code Map unit symbol 2 QTt 3 Qal 4 Qc 5 Qlg 6 Qt 7 sink 8 water
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