Geologic Map Database of the Washington DC Area Featuring Data From Three 30 X 60 Minute Quadrangles: Frederick, Washington West, and Fredericksburg

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Frequently anticipated questions:


What does this data set describe?

Title:
Geologic Map Database of the Washington DC Area Featuring Data From Three 30 X 60 Minute Quadrangles: Frederick, Washington West, and Fredericksburg
Abstract:
The Washington DC Area geologic map database (DCDB) provides geologic map information of areas to the NW, W, and SW of Washington, DC to various professionals and private citizens who have uses for geologic data. Digital, geographically referenced, geologic data is more versatile than traditional hard copy maps, and facilitates the examination of relationships between numerous aspects of the geology and other types of data such as: land-use data, vegetation characteristics, surface water flow and chemistry, and various types of remotely sensed images. The DCDB was created by combining Arc/Info coverages, designing a Microsoft (MS) Access database, and populating this database. Proposed improvements to the DCDB include the addition of more geochemical, structural, and hydrologic data.
Supplemental_Information:
Data are provided in several common GIS formats and MS Access database files. The geologic data themes included are bedrock, surficial, faults and fold axes, neat line, structural data, and sinkholes; the base themes are political boundaries, roads, elevation contours, and hydrography.
Data were originally collected in UTM coordinates, zone 18, NAD 1927, and projected to geographic coordinates (Lat/Long), NAD 1983. The data base is accompanied by large format color maps, a readme.txt file, and a explanatory PDF pamphlet.
  1. How might this data set be cited?
    Davis, Adam M., Southworth, C. Scott, Schindler, J. Stephen, and Reddy, James E., 2001, Geologic Map Database of the Washington DC Area Featuring Data From Three 30 X 60 Minute Quadrangles: Frederick, Washington West, and Fredericksburg: U.S. Geological Survey Open-File Report 01-227, U.S. Geological Survey, Reston, Virginia.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -78.00
    East_Bounding_Coordinate: -77.00
    North_Bounding_Coordinate: 39.50
    South_Bounding_Coordinate: 38.00
  3. What does it look like?
    http://pubs.usgs.gov/of/2001/of01-227/01227p1p.gif (GIF)
    Reduced-size image showing the general layout of map sheet. 640x864 pixels, 24-bit color.
    http://pubs.usgs.gov/of/2001/of01-227/01227p2p.gif (GIF)
    Reduced-size image showing the general layout of map sheet. 640x864 pixels, 24-bit color.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 1988
    Ending_Date: 2001
    Currentness_Reference:
    Publication date
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: Tabular digital data and map
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • Entity point
      • GT-polygon composed of chains
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.001. Longitudes are given to the nearest 0.001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257.
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    The following is a brief description of the data layers, tables, and their associated
    attributes that are used in this report.
    
    GEOLOGIC DATA:
    BEDROCK - Polygon data layer of bedrock geologic map units
      BEDROCK.PAT items:
        MAPUNIT - Bedrock geologic map unit code
        COA_ID - Compound object archive identifier, map unit names and descriptions -
                 a data linkage hub in North American Data Model (NADM) 4.3
    
    FAULT - Line data layer of geologic faults and folds
      FAULT.AAT items:
        SYMBOL - Symbol number from FAULT.LIN or ALCNEW61.LIN linesets, used for plotting
        SYMBOL-ARC - Symbol number from GDS1.LIN lineset, used for plotting
        FEATURE - Geologic Data Systems (GDS) assigned feature description
        ELEVATION - GDS assigned attribute
        TYPE - Type of fault
          TYPE Code  Description
             AC      Anticline
             AF      Antiform
            ARO      Arrow showing movement along strike-slip fault
             FZ      Fault zone
              N      Normal fault
             NT      Normal fault re-activated as thrust fault
             OT      Overturned thrust fault
             SC      Syncline
             SF      Synform
             SS      Strike-slip fault
              T      Thrust fault
             TA      Thermal aureole
             UF      Unclassified fault
            ULF      Unclassified linear feature
        CODE - Identifies fault segments which are overlaid by surficial deposits
               (CODE = 2).  Used for plotting.  Relevant only for those faults which
               lie within the boundary of the USGS Frederick 1:100000-scale map.
        QUAD - Identifies the USGS 1:100000-scale map to which the feature belongs
          QUAD
          Code  Description
           FB - Fredericksburg
           FK - Frederick
           WW - Washington West
    
    NEAT - Line data layer of map neatline
    
    SINK - Point data layer of sinkhole locations
      SINK.PAT items:
        MAPUNIT - Set to 'Sinkhole'
    
    STRUCTURE - Point data layer of geologic structure
      STRUCTURE.PAT items:
        DIP - Dip value (planar data) or plunge value (linear data)
        STRIKE_ANG - GDS assigned angle measured from North
        AZIMUTH - Angle measured from North in right-hand rule (planar data).
                  Routines used to digitize the geologic structure symbols that
                  lie within the boundaries of the USGS Frederick and Washington
                  West 1:100000-scale maps (item QUAD equal to 'FK' and 'WW',
                  respectively) resulted in the azimuth value for those symbols to
                  be calculated based on a northern trend (270<=azimuth<=90).
                  Southern trending azimuth values (90<azimuth<270) for structure
                  symbols associated with the Frederick and Washington West maps
                  were translated to their northern trend equivalents.  If necessary,
                  the southern trending azimuth values for these symbols can be
                  restored using the item SYMB_ANG and the following equations:
                    For 180<SYMB_ANG<=270,
                      azimuth = AZIMUTH + 180
                    For 270<SYMB_ANG<360,
                      azimuth = AZIMUTH - 180
        TYPE - Type of geologic structure.  Relevant for geologic structure data
               that lies within the boundaries of the USGS Frederick and Washington West
               1:100000-scale maps (item QUAD equal to 'FK' and 'WW')
          TYPE Code  Description
            AGE      Sample site for U-Pb isotopic technique for age date
             HB      Horizontal bed
            I1C      Inclined first-generation Paleozoic cleavage and (or) schistosity
            I2C      Inclined second-generation Paleozoic cleavage and (or) schistosity
            IEF      Inclined early foliation
             IB      Inclined bed
             IF      Inclined Middle Proterozoic foliation
            IMP      Inclined mylonitic and phyllonitic foliations
            IPF      Inclined phyllonitic foliation
             MA      Minor antiform
             OB      Overturned bed
             QM      Quarry or mine
            RAD      Greater than 200 pCi/L of soil gas radon
            V1C      Vertical first-generation Paleozoic cleavage and (or) schistosity
            V2C      Vertical second-generation Paleozoic cleavage and (or) schistosity
             VB      Vertical bed
            VEF      Vertical early foliation
             VF      Vertical Middle Proterozoic foliation
            VMP      Vertical mylonitic and phyllonitic foliations
        SUB_TYPE - Type of quarry mine
          SUB_TYPE
            Code    Description
             Ag     Silver
             Au     Gold
              C     Chromite
             Cu     Copper
              D     Diabase
              F     Hematite, limonite, and iron-ore
              L     Limestone
              M     Marble
             Mg     Magnetite
             Mn     Manganese
             Pb     Lead
              S     Building stone
             Sl     Slate
             Zn     Zinc
        SYMB_ANG - Standard Cartesian angle measured from East.  Used for plotting.
        DIPDIR - Direction of dip (planar data) or trend (linear data) measured from North
        SYMBOL - Symbol number from the LOUDOUN_AP.MRK markerset or the MPLY.LIN lineset,
                 used for plotting
        FEATURE - Type of geologic structure.  Relevant for geologic structure data that
                  lies within the boundary of the USGS Fredericksburg 1:100000-scale
                  map (item QUAD equal to 'FB')
        GROUP - GDS assigned attribute
        METHOD - GDS assigned attribute
        SOURCE - GDS assigned attribute
        DIP_DIR - GDS assigned attribute
        SYMB_ARC - Symbol number from the GDS1.MRK markerset, used for plotting
        QUAD - Identifies the USGS 1:100000-scale map to which the structure data belongs
          QUAD
          Code  Description
           FB - Fredericksburg
           FK - Frederick
           WW - Washington West
    
    SURFICIAL - - Polygon data layer of surficial geologic map units
      SURFICIAL.PAT items:
        MAPUNIT - Surficial geologic map unit code
        COA_ID - Compound object archive identifier, map unit names and descriptions -
                 a data linkage hub in North American Data Model (NADM) 4.3
    
    BASE DATA:
    POLBND - Net data layer of state and county boundaries:
      POLBND.AAT items:
        POLBND-ID
          TYPE - State or county boundary
      POLBND.PAT items:
        STATE_NAME - State in which county resides
        CNTY_NAME - County name
        STATE_FIPS - State FIPS code (character field)
        CNTY_FIPS - County FIPS code (character field)
        FIPS - FIPS code for state/county (character field)
        MAJOR# - DLG code
        MINOR# - DLG code
          Major DLG  Minor DLG
            Code       Code     Description
             91        ---      State FIPS code (integer field)
             92        ---      County FIPS code (integer field)
    
    ROADS - Line data layer of major highways
      ROADS.AAT items:
        MAJOR# - DLG code
        MINOR# - DLG code
          Major DLG  Minor DLG
            Code       Code     Description
            170        201      Primary route, class 1, undivided
            170        203      Primary route, class 1, divided
            170        204      Primary route, class 1, one way
            170        205      Secondary route, class 2, undivided
            170        207      Secondary route, class 2, divided
            170        209      Road or street, class 3
            170        210      Road or street, class 4
            170        401      Traffic circle
            170        402      Cloverleaf or interchange
            170        607      Underpassing
            170        617      Business route
            172        ---      Interstate route number
            173        ---      U.S. route number
            174        ---      State route number
    
    TOPO - Line data layer of elevation contours
      TOPO.AAT items:
        MAJOR# - DLG code
        MINOR# - DLG code
          Major DLG  Minor DLG
            Code       Code     Description
             20        20O      Contour (index or intermediate)
             20        201      Carrying contour
             20        204      Amended contour
             20        208      Closure line
             20        611      Depression
             24        ---      Elevation in whole meters
        TYPE - Type of contour: index (Index) or intermediate (Inter),
               used for plotting
    
    HYDRO - Polygon data layer of major water bodies
      HYDRO.PAT items:
        RINGS_OK - Attribute assigned by the Chesapeake Bay Program
        RINGS_NOK - Attribute assigned by the Chesapeake Bay Program
        FEATURE - Type of hydrologic feature (stream, pond, marsh, etc.)
    
    Entity_and_Attribute_Detail_Citation: http://pubs.usgs.gov/of/2001/of01-227/of01227.pdf

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Adam M. Davis
    • C. Scott Southworth
    • J. Stephen Schindler
    • James E. Reddy
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    C. Scott Southworth
    U.S. Geological Survey
    National Center, MS926A
    Reston, Virginia
    USA

    703-648-6385 (voice)
    703-648-6953 (FAX)
    ssouthwo@usgs.gov

Why was the data set created?

Geology was researched and compiled for use in studies of ecosystem health, environmental impact, soils, groundwater, land use, tectonics, crustal genesis, sedimentary provenance, and any others that could benefit from geographically referenced geological data.

How was the data set created?

  1. From what previous works were the data drawn?
    Mixon and others (2000) (source 1 of 3)
    Mixon, R.B., Pavlides, Louis, Powars, D.S., Froelich, A.J., Weems, R.E., Schindler, J.S., Newell, W.L., Edwards, L.E., and Ward, L.W., 2000, Geologic map of the Fredericksburg 30' X 60' quadrangle, Virginia and Maryland: U.S. Geological Survey, Geologic Investigations Series Map I-2607.

    Other_Citation_Details:
    Type_of_Source_Media: paper
    Source_Scale_Denominator: 100000
    Source_Contribution:
    These geologic data were compiled at the scale 1:100,000 from a series of detailed published and unpublished field investigations at scales ranging from 1:24000 to 1:100000.
    Lyttle and others (in press) (source 2 of 3)
    Lyttle, P.T., Aleinikoff, J.N., Drake, A.A., Jr., Froelich, A.J., Horton, J.W., Jr., Kasselas, G., McCartan, L., Mixon, R.B., Nelson, A.E., Pavlides, L., and Weems, R.E., in press, Geologic Map of the Washington West 30' X 60' Quadrangle, District of Columbia, Virginia, Maryland: U.S. Geological Survey Geologic Investigations Series Map.

    Type_of_Source_Media: mylar
    Source_Contribution:
    These geologic data were compiled at the scale 1:100,000 from a series of detailed published and unpublished field investigations at scales ranging from 1:24000 to 1:100000.
    Southworth and others (in press) (source 3 of 3)
    Southworth, S., Brezinski, D.K., Drake, A.A.,Jr., Burton, W.C., Orndorff, R.C., Froelich, A.J., Reddy, J., and Daniels, D.L., in press, Geologic Map of the Frederick 30' x 60' Quadrangle, Maryland and Virginia: U.S. Geological Survey Geologic Investigations Series Map.

    Type_of_Source_Media: mylar
    Source_Contribution:
    These geologic data were compiled at the scale 1:100,000 from a series of detailed published and unpublished field investigations at scales ranging from 1:24000 to 1:100000.
  2. How were the data generated, processed, and modified?
    Date: 1999 (process 1 of 3)
    The geologic map data was digitized from mylar scribe sheets used to prepare the published or in press Geologic Maps of the Fredericksburg (Mixon and others, 2000), Washington West (Lyttle and others, in press), and Frederick (Southworth and others, in press) 30 X 60 Minute Quadrangles at a map scale of 1:100,000. Mylar scribe sheets were scannned, vectorized and then imported into Arc/Info software. Frederick and Washington West were digitized by the Eastern Earth Surface Processes Team of the U.S. Geological Survey. Fredericksburg was digitized by Geologic Data Systems, Inc., 1600 Emerson Street, Denver, CO 80218
    Date: 21-Dec-1999 (process 2 of 3)
    Polygons, lines, and points for each of the three 30 X 60 minute quadrangles were combined into a single polygon coverage (i.e., bedrock and surficial map units), a single line coverage (i.e., faults and fold axes) and two point coverages (sinkholes and structural measurements). This process involved edgematching of linework and making the map unit symbols uniform across quadrangle boundaries.
    Date: 31-Oct-2000 (process 3 of 3)
    Surficial geology polygons were separated from the bedrock map units into a surficial polygon coverage. The result is two map unit coverages: one that contains bedrock geology units and one that contains surficial geology units.
  3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    DCDB Version 1.0 - subsequent versions may contain more data and/or a greater diversity of data types.
  5. How consistent are the relationships among the observations, including topology?
    Polygon and chain-node topology present

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
Use_Constraints:
Although all data released in this report have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials and (or) the functioning of the software. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey
    C. Scott Southworth
    National Center, MS926A
    Reston, Virginia
    USA

    703-648-6385 (voice)
    703-648-6953 (FAX)
    ssouthwo@usgs.gov
    Hours_of_Service: Monday - Friday 9:00 - 5:00 EST
  2. What's the catalog number I need to order this data set? USGS Open-File Report 01-227
  3. What legal disclaimers am I supposed to read?
    These data were prepared by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, expressed or implied, or assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product or process disclosed in this report, and represents that its use would not infringe privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of this data or related materials. Reference therein to any specific commercial product, process, or related service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.
  4. How can I download or order the data?
    • Availability in digital form:
      Data format: Bedrock and surficial geologic map units, fault and fold axes, structural geology, political boundaries, elevation contours, and major highways and water bodies. in format ARCE (version 8.0.2) Size: 37.0
      Network links: http://pubs.usgs.gov/of/2001/of01-227/of01227.zip
    • Cost to order the data: none


Who wrote the metadata?

Dates:
Last modified: 13-Jun-2016
Last Reviewed: 05-May-2002
Metadata author:
U.S. Geological Survey
James E. Reddy
30 Brown Road
Ithaca, New York
USA

607-266-0217, x3014 (voice)
607-266-0521 (FAX)
jreddy@usgs.gov
Hours_of_Service: Monday - Friday 9:00 - 5:00 EST
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

This page is <https://geo-nsdi.er.usgs.gov/metadata/open-file/01-227/metadata.faq.html>
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