Preliminary geologic map of the San Francisco South 7.5' quadrangle and part of the Hunters Point 7.5' quadrangle, San Francisco Bay area, California: A digital database

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Frequently anticipated questions:

What does this data set describe?

Preliminary geologic map of the San Francisco South 7.5' quadrangle and part of the Hunters Point 7.5' quadrangle, San Francisco Bay area, California: A digital database
This Open-File report is a digital geologic map database of the San Francisco South 7.5' quadrangle. This pamphlet serves to introduce and describe the digital data. No paper map is included in the Open-File report, however this report includes a PostScript and a Portable Documet Format plot file containing an image of a geologic map sheet and an explanation.
  1. How might this data set be cited?
    Bonilla, M.G., 1998, Preliminary geologic map of the San Francisco South 7.5' quadrangle and part of the Hunters Point 7.5' quadrangle, San Francisco Bay area, California: A digital database: U.S. Geological Survey Open-File Report 98-354.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -122.50
    East_Bounding_Coordinate: -122.38
    North_Bounding_Coordinate: 37.75
    South_Bounding_Coordinate: 37.63
  3. What does it look like? (PDF)
    PDF representation of a 4.2 megabyte image of the geologic map and base maps at a scale of 1:24,000
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 1998
    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: California Stateplane coordinate system
      SPCS_Zone_Identifier: 3326
      Planar coordinates are encoded using coordinate pair
      Planar coordinates are specified in meters
      The horizontal datum used is NAD27.
      The ellipsoid used is Clarke 1866.
      The semi-major axis of the ellipsoid used is 6378206.
      The flattening of the ellipsoid used is 1/294.98.
  7. How does the data set describe geographic features?
    Geologic map units (Source: OFR-98-354)
    Polygon type (Source: OFR-98-354)
    waterbodies of water
    QafArtificial fill (Holocene)
    Qaf/tfArtificial fill over tidal flat (Holocene)
    QafsArtificial fill, Native American shellmound (Holocene)
    QlLandslide deposits (Holocene)
    QalAlluvium (Holocene)
    QbBeach deposits (Holocene)
    QmBay mud (Holocene)
    QdDune sand (Holocene)
    QtMarine terrace deposits (Pleistocene)
    QsrSlope debris and ravine fill (Pleistocene)
    QcColma Formation (Pleistocene)
    QuSedimentary deposits, undifferentiated (Pleistocene)
    frFault rocks (Holocene to Pleistocene)
    QTmMerced Formation (Pleistocene and Pliocene)
    KJsSandstone and shale: Franciscan complex (Cretaceous and Jurassic)
    KJskSandstone and shale: Franciscan Complex (Cretaceous nad Jurassic)
    KJcChert: Franciscan Complex (Cretaceous and Jurassic)
    KJgGreenstone: Fransciscan Complex (Cretaceous and Jurassic)
    KJmMetamorphic rocks: Franciscan Complex (Cretaceous and Jurassic)
    spSerpentine: Franciscan Complex (Cretaceous nad Jurassic)
    KJuSheared rocks: Franciscan Complex (Cretaceous and Jurassic)
    Linear geologic features (Source: OFR-98-354)
    Line type (Source: OFR-98-354)
    '1800s shoreline', certainObserved shoreline of the 1800s
    '1800s stream channel', certainObserved stream channel from the 1800s
    contact, approx. locatedGeologic contact whose position is not precisely known
    contact, certainObserved geologic contact
    contact, concealedGeologic contact that is concealed and position inferred
    contact, gradational or inferredGeologic contact whose position is either gradational or inferred
    fault, certainObserved fault
    fault, concealedFault that is concealed and its position inferred
    fault, concealed, queriedFault that is concealed and its position questionable
    fault, inferredFault whose position is inferred
    map boundary, certainextent of mapped area
    topographic escarpmentLocation of topographic escarpment
    water boundary, certainBoundary of a body of water
    Geologic map unit at specific localities (same attributes as the polygon coverage SFS-GEOL.PAT) (Source: OFR-98-354)
    Location of fold axes (Source: OFR-98-354)
    Line type (Source: OFR-98-354)
    f.a., anticline, approx. locatedAnticlinal fold-axis whose position is not precisely known
    f.a., anticline, certainObserved anticlinal fold-axis
    f.a., monocline, approx. locatedMonoclinal fold-axis whose position is not precisely known
    fault, approx. locatedFault whose position is not precisely known
    f.a., syncline, approx. locatedSynclinal fold-axis whose position is not precisely known
    Strike and Dip information (Source: OFR-98-354)
    Point type (Source: OFR-98-354)
    beddingbedding orientation
    approx beddingapproximate bedding orientation
    flat beddingflat bedding orientation
    vertical beddingvertical bedding orientation
    jointjoint orientation
    foliationfoliation orientation
    foreset bedsforeset beds orientation
    fault attitudeFault attitude
    shear planesshear planes orientation
    _l_lineation_i_Lineation orientation
    vertical jointvertical joint orientation
    dip of bedding or foliation (Source: OFR-98-354)
    Range of values
    Strike of bedding or foliation (Source: OFR-98-354)
    Range of values

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • M.G. Bonilla
  2. Who also contributed to the data set?
    Carl M. Wentworth, Todd T. Fitzgibbon, and Geoffrey A. Phelps graciously provided assistance with Alacarte and ARC/INFO. The scanning of the whole 1:24,000 quad and initial editing of the quarters of the map after it was divided was done by the following individuals: Heather Schoonover (northwest), Marjorie Lucks (southeast), Scott Graham (southwest), and Carl Wentworth (northeast). Marjorie Lucks compiled the sub-quadrangles, skillfully made many changes requested by the author, and did much of the final editing of the whole map along with Thomas May.
  3. To whom should users address questions about the data?
    Bonilla, Manuel G
    Mail Stop 977, USGS
    345 Middlefield Rd
    Menlo Park, CA

    650-329-5615 (voice)

Why was the data set created?

To provide it provides basic information on the stratigraphy and structure of the area of the San Francisco South 7.5' quadrangle and the western part of the Hunters Point 7.5 quadrangle to the public.

How was the data set created?

  1. From what previous works were the data drawn?
    Bonilla (1965) (source 1 of 1)
    Bonilla, M.G., 1965, Geologic map of the San Francisco South quadrangle, California.

    Type_of_Source_Media: paper
    Source_Scale_Denominator: 20000
    Source_Contribution: scanned for digital compilation
  2. How were the data generated, processed, and modified?
    Date: 1980 (process 1 of 2)
    The geologic map information was digitized from stable originals of the geologic map at 1:20,000 scale. A mylar copy of the earlier map (Bonilla 1965) was scanned using a Altek monochrome scanner with a resolution of 800 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 appropriate, and scanning artifacts visible at 1:24,000 were corrected. Base Map layers were prepared from scale-stable printing negatives of the U.S. Geological Survey San Francisco South (1980 photorevision), and Hunters Point (1980 photorevision) 1:24,000 topographic maps, which have a 25 foot contour interval. These base map layers are digital images but no information other than location is attached to the lines. The base maps are provided for reference only.
    Date: 15-May-2009 (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

    703-648-6974 (voice)
    703-648-6560 (FAX)
  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?
    The map's small scale does not provide sufficient detail for site development purposes. In addition, this map does not take the place of fault-rupture hazard zones designated by the California State Geologist (Hart and Bryant, 1997). The map shows mappable landslides as they existed about 1959. Although many of the landslides still exist, many others have been removed during urban development or by natural processes, and post-1959 landslides are not shown.
  5. How consistent are the relationships among the observations, including topology?
    The geologic map information was digitized from stable originals of the geologic map at 1:20,000 scale.

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

    1-888-ASK-USGS (voice)
    1-303-202-4695 (FAX)
  2. What's the catalog number I need to order this data set? USGS Open-File Report 98-354
  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 Geologic Map of the San Francisco South 7.5 Quadrangle and Part of the Hunters Point 7.5 Quadrangle, San Francisco Bay Area, 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: Depositional contacts, faults, lineations, fault dips, and unit labels, strike and dip information and fold axes, and cartographic base maps in format ARCE (version 7.x) Size: 6.2
      Network links:
    • Cost to order the data: none

Who wrote the metadata?

Last modified: 05-Feb-2016
Metadata author:
Peter N Schweitzer
USGS Midwest Area
Collection manager, USGS Geoscience Data Clearinghouse,
Mail Stop 954
12201 Sunrise Valley Dr
Reston, VA

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

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