Preliminary quaternary geologic maps of Santa Clara Valley, Santa Clara, Alameda, and San Mateo counties, California: A digital database

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Frequently anticipated questions:


What does this data set describe?

Title:
Preliminary quaternary geologic maps of Santa Clara Valley, Santa Clara, Alameda, and San Mateo counties, California: A digital database
Abstract:
This digital map database, which is compiled from previously unpublished and open-filed U.S. Geol. Survey reports (Wesling and Helley, 1989), represents the general distribution and identity of Quaternary deposits in eight 7.5 minute quadrangles in the southern San Francisco Bay region, California.
  1. How might this data set be cited?
    Helley, E.J., Graymer, R.W., Phelps, G.A., Showalter, P.K., and Wentworth, C.M., 1994, Preliminary quaternary geologic maps of Santa Clara Valley, Santa Clara, Alameda, and San Mateo counties, California: A digital database: U.S. Geological Survey Open-File Report 94-231.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -122.25
    East_Bounding_Coordinate: -121.75
    North_Bounding_Coordinate: 37.5
    South_Bounding_Coordinate: 37.125
  3. What does it look like?
    http://pubs.usgs.gov/of/1994/of94-231/sccomap.pdf (PDF)
    Plotfile of digital database in PDF format (3.4MB)
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 1994
    Currentness_Reference:
    publication date
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: 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
      • Complete chain
      • GT-polygon composed of chains
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Trasverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 10
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -123
      Latitude_of_Projection_Origin: 0.0
      False_Easting: -500000
      False_Northing: 0
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest unknown
      Ordinates (y-coordinates) are specified to the nearest unknown
      Planar coordinates are specified in meters
  7. How does the data set describe geographic features?
    XXX_UTM.PAT (XXX represents abbreviated quadrangle name)
    Quaternary geologic map units (Source: OFR-94-0231)
    PTYPE
    Polygon type (Source: OFR-94-0231)
    ValueDefinition
    GPGravel Pits
    PPPercolation ponds
    QhscStream channel deposits (Holocene)
    QhlNatural levee deposits (Holocene)
    Qhfp2Second alluvial terrace deposits (Holocene)
    Qhfp1First alluvial terrace deposits (Holocene)
    QhfpFloodplain deposits (Holocene)
    hbFloodbasin deposits (Holocene)
    QhbsSalt-affected floodbasin deposits (Holocene)
    QhbmEstuary deposits (bay mud) (Holocene)
    Qhaf1Younger alluvial fan deposits (Holocene)
    QhafAlluvial fan deposits (Holocene)
    QlsLandslide deposits (Pleistocene and Holocene)
    Qpaf1Younger alluvial fan deposits (Pleistocene)
    QpafAlluvial fan deposits (Pleistocene)
    QpoafOlder alluvial fan deposits (Pleistocene)
    QTscSanta Clara Formation (Pliocene and Pleistocene)
    brUndifferentiated bedrock (Pliocene and older)
    XXX_UTM.AAT (XXX represents abbreviated quadrangle name)
    Linear geologic features (Source: OFR-94-0231)
    LTYPE
    Line type (Source: OFR-94-0231)
    ValueDefinition
    contact, certainObserved contact
    contact, approx. locatedContact whose position is not precisely known
    contact, concealedContact whose position is concealed and inferred
    fault, certainObserved fault
    fault, approx. locatedFault whose position is not precisely known
    fault, concealedConcealed fault whose position is inferred
    water boundary, certainBoundary of a body of water
    map boundaryBoundary of mapped area
    ca. 1850 shorelineHistorical 1850 shoreline
    XXX_UTM.PAT (XXX represents abbreviated quadrangle name)
    Quaternary geologic map units at specific locations (same attributes as polygon coverage XXX_UTM.PAT) (Source: OFR-94-0231)
    CORR_UTM.PAT
    Correlation table for the units in these maps (same attributes as polygon coverage XXX_UTM.PAT) (Source: OFR-94-0231)
    CORR_UTM.AAT
    Linear features in correlation table for the units in these maps (same attributes as arc coverage XXX_UTM.AAT) (Source: OFR-94-0231)
    CORR_UTM.PAT
    Point features of correlation table for the units in these maps (same attributes as polygon coverage XXX_UTM.PAT) (Source: OFR-94-0231)
    EXPLSC_UTM.PAT
    Map explanation and key (same attributes as polygon coverage XXX_UTM.PAT) (Source: OFR-94-0231)
    EXPLSC_UTM.AAT
    Linear features on map explanation and key (same attributes as arc coverage XXX_UTM.AAT) (Source: OFR-94-0231)
    EXPLSC_UTM.PAT
    Point coverage of map explanation and key (same attributes as polygon coverage XXX_UTM.PAT) (Source: OFR-94-0231)
    Entity_and_Attribute_Overview:
    Quadrangle abbrev.  Quadrangle full name
    
    cal                 Calaveras Reservoir quadrangle
    cup                 Cupertino quadrangle
    mil                 Milpitas quadrangle
    mtv                 Mountain View quadrangle
    pal                 Palo Alto quadrangle
    sje                 San Jose East quadrangle
    sjw                 San Jose West quadrangle
    sth                 Santa Teresa Hills quadrangle
    
    Entity_and_Attribute_Detail_Citation: http://pubs.usgs.gov/of/1994/of94-231/scc_q1.ReadMe.txt

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • E.J. Helley
    • R.W. Graymer
    • G.A. Phelps
    • P.K. Showalter
    • C.M. Wentworth
  2. Who also contributed to the data set?
    Compilation of the digital database depended on advice and assistance in the use of ALACARTE - ARC/INFO from T.T. Fitzgibbon and C.M. Wentworth. E.E. Brabb provided helpful information.
  3. To whom should users address questions about the data?
    Graymer, Russell W
    USGS-GEO-WRG-NGM
    Mail Stop 975, USGS
    345 Middlefield Road
    Menlo Park, CA
    US

    650-329-4988 (voice)
    rgraymer@usgs.gov

Why was the data set created?

Together with the accompanying text file (scgeo.txt), this digital map database provides current information on the Quaternary geology of the area covered. The database delineates map units that are identified by general age and lithology following the compilation sources. One bedrock unit, the Santa Clara formation, is differentiated but the other bedrock units are combined and are not identified. More specific information about the units may be available in the original Open-file reports.

How was the data set created?

  1. From what previous works were the data drawn?
    Wesling and Helley (1989) (source 1 of 1)
    Wesling, J.R., and Helley, E.J., 1989, Quatervary Geologic Map of the San Jose West Quadrangle, Santa Clara County, California: U.S. Geological Survey Open-File Report 91-0587-B.

    Type_of_Source_Media: paper
    Source_Scale_Denominator: 24000
    Source_Contribution:
    Compilied information on the general distribution and identity of Quaternary deposits in eight 7.5 minute quadrangles in the southern San Francisco Bay region, California.
  2. How were the data generated, processed, and modified?
    Date: unknown (process 1 of 2)
    The geologic map information was digitized from stable originals of the geologic maps at 1:24,000 scale. The author manuscripts (ink on mylar) were scanned using a Tektronix 4991 monochrome scanner with a resolution of 304.8 dots per inch. The scanned images were vectorized and transformed from scanner coordinates to projection coordinates with digital tics placed by hand at quadrangle corners. The scanned lines were edited interactively by hand using ALACARTE, color boundaries were tagged as a contact or fault as appropriate, and scanning artifacts visible at 1:24,000 were removed. Quadrangle boundaries are included in each coverage to retain the integrity of units in each quadrangle, except in cal_utm where a large area of undifferentiated bedrock was placed outside the map boundary to allow convenient placement of the map explanation.
    Base Map layers were prepared from scale-stable printing negatives of the U.S. Geological Survey Palo Alto (1982 edition) and San Jose (1978 edition) 1:100,000 topographic maps. Scanned and vectorized images were transformed from scanner coordinates to projection coordinates with digital tics placed by hand at map corners. The images were then trimmed interactively by hand using ALACARTE to conform to the area of the geologic coverages, and the Palo Alto and San Jose portions were combined.
    Date: 05-Sep-2000 (process 2 of 2)
    Creation of original metadata record Person who carried out this activity:
    Jennifer Lenz
    US Geological Survey
    12201 Surise Valley Drive, Mail Stop 918
    Reston, VA
    USA

    703-648-6974 (voice)
    703-648-6560 (FAX)
    pschweitzer@usgs.gov
  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?
    Small mismatches at the San Jose - Palo Alto boundary caused by slight differences in the original scans remain in the three base map coverages.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    Faults are distinguished in the database only where they are at or near unit boundaries and the database cannot be used to identify or delineate active faults in the region. Similarly, the database cannot be used to identify or delineate most landslides in the region, because only one large landslide, in San Jose East quadrangle, is shown.
  5. How consistent are the relationships among the observations, including topology?
    This digital map database, which is compiled from previously unpublished and US Geological Survey Open-File reports (Wesling and Helley, 1989), represents the general distribution and identity of Quaternary deposits in eight 7.5 minute quadrangles in the southern San Francisco Bay region, California.

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: None
  1. Who distributes the data set? (Distributor 1 of 1)
    USGS Information Services
    Box 25286, Denver Federal Center
    Denver, Colorado
    USA

    1-888-ASK-USGS (voice)
    1-303-202-4695 (FAX)
    infoservices@usgs.gov
  2. What's the catalog number I need to order this data set? USGS Open-File Report 94-231
  3. What legal disclaimers am I supposed to read?
    This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
    This database, identified as "Preliminary Quaternary geologic maps of Santa Clara Valley, Santa Clara, Alameda, and San Mateo Counties, California: A digital database," has been approved for release and publication by the Director of the USGS. Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use.
  4. How can I download or order the data?
    • Availability in digital form:
      Data format:
      ARC/INFO coverage  Description of coverage
      
      cal_utm             Quaternary geology of Calaveras Reservoir quadrangle
      cup_utm             Cupertino quadrangle
      mil_utm             Milpitas quadrangle  (Helley and Wesling, 1989)
      mtv_utm             Mountain View quadrangle
      pal_utm             Palo Alto quadrangle
      sje_utm             San Jose East quadrangle (Helley and Wesling, 1990)
      sjw_utm             San Jose West quadrangle  (Wesling and Helley, 1989)
      sth_utm             Santa Teresa Hills quadrangle
      explsc_utm
      explsc_ano          Together, these ARC coverages produce a plottable or displayable map explanation and key
      corr_utm
      corr_ano            Together, these ARC coverages contain a correlation table for the units in these maps
      scc_dr              Drainage base map
      scc_cu              Cultural base map
      scc_topo            Topographic contours base map
      
      in format ARCE (version 6.x) Size: 8.3
      Network links: http://pubs.usgs.gov/of/1994/of94-231/scc_q1.tar.Z
    • Cost to order the data: none


Who wrote the metadata?

Dates:
Last modified: 05-Feb-2016
Metadata author:
Peter N Schweitzer
USGS Midwest Area
Collection manager, USGS Geoscience Data Clearinghouse, http://geo-nsdi.er.usgs.gov/
Mail Stop 954
12201 Sunrise Valley Dr
Reston, VA
USA

703-648-6533 (voice)
703-648-6252 (FAX)
pschweitzer@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://geo-nsdi.er.usgs.gov/metadata/open-file/94-231/metadata.faq.html>
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