General distribution of geologic materials in the southern San Francisco Bay region, California: A digital map database

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Frequently anticipated questions:

What does this data set describe?

General distribution of geologic materials in the southern San Francisco Bay region, California: A digital map database
The ssfb_m1 digital map database, which is compiled from 1970's vintage sources, represents the general distribution and identity of geologic materials in the southern San Francisco Bay region, California, west of the Calaveras fault. It is not a geologic map, because it does not address the geologic structure or the stratigraphic organization of the map units in a systematic way. Instead, it is directed at the distribution and character of the geologic materials following the pattern of its progenitors, Wentworth and others (1985) and Ellen and Wentworth (in press). Consultation of these reports and the other compilation sources will aid in using the database.
  1. How might this data set be cited?
    Wentworth, Carl M., 1993, General distribution of geologic materials in the southern San Francisco Bay region, California: A digital map database: U.S. Geological Survey Open-File Report 93-693.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -122.6
    East_Bounding_Coordinate: -121.335
    North_Bounding_Coordinate: 37.875
    South_Bounding_Coordinate: 36.851
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 1993
    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.
    2. What coordinate system is used to represent geographic features?
      The map projection used is Lambert Conformal Conic.
      Projection parameters:
      Standard_Parallel: 37.07
      Standard_Parallel: 38.43
      Longitude_of_Central_Meridian: -120.5
      Latitude_of_Projection_Origin: 36.5
      False_Easting: 0
      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?
    Digital map polygon coverage (Source: OFR-93-0693)
    Polygon type (Source: OFR-93-0693)
    H2OBody of water
    LSLandslide deposit
    brUndifferentiated bedrock
    damLocation of dam
    unmappedUnmapped area
    Range of values
    Map unit symbols (No definitions given) (Source: OFR-93-0693)
    Landslide deposits (Source: OFR-93-0693)
    LSLocation of landslide deposit
    (blank)Not a landslide deposit
    Age of deposit (Source: OFR-93-0693)
    TlLower Tertiary
    TuUpper Tertiary
    (blank)Age unknown
    Lithology of map unit abbreviation (Source: OFR-93-0693)
    bvmafic volcanic rocks
    fvFelsic volcanic rocks
    grgranitic rock
    mmud and silt
    mdMudstone and shale, some sandstone
    mmSheared sandstone and shale (melange)
    msLow-grade metasandstone and shale
    mvLow-grade metavolcanic rocks (greenstone)
    sSand, gravel, silt, and mud
    scSilica-carbonate rock
    slPorcellaneous or siliceous mudstone and shale; chert
    smSandstone and mudstone or shale
    ssSandstone and conglomerate, some mudstone or shale
    wmSoft, water-saturated mud, some silt
    AGE and LITH attributes combined (No definitions given) (Source: OFR-93-0693)
    Numerical symbol for geologic map unit (Source: OFR-93-0693)
    1unnamed or no name reported
    2Alum Rock Rhyolite
    3Aromas sand
    4Bay mud
    5Briones sandstone
    6Butano sandstone
    7Cierbo sandstone
    8Claremont shale
    9Colma formation
    10Franciscan complex
    11Great valley sequence
    12Hambre sandstone
    13Joaquin Miller formation
    14Knoxville formation
    15Lambert shale
    16Lambert shale and San Lorenzo formation, undivided
    17Leona rhyolite
    18Locatelli formation
    19Lompico sandstone
    20Markley formation
    21Merced formation
    22Merritt sandstone
    23Mindego basalt
    24Monterey formation
    25Monterey group
    26Monterey shale
    27Moraga formation
    28Mullholland formation
    29Neroly sandstone
    30Oakland conglomerate
    31Orinda formation
    32Oursan sandstone
    33Page Mill basalt
    34Pigeon Point formation
    35Pinehurst shale
    36Purisima formation
    37Redwood canyon formation
    38Rices mudstone member, San Lorenzo formation
    39Rodeo shale
    40San Lorenzo formation
    41San Pablo group
    42San Ramon sandstone
    43Santa Clara, Livermore, or Packwood gravels
    44Santa Cruz mudstone
    45Santa Margarita sandstone
    46Shephard Creek formation
    47Siesta formation
    48Sobrante sandstone
    49Temblor sandstone
    50Tice shale
    51Tolman formation
    52Twobar shale member, San Lorenzo formation
    53Vaqueros sandstone
    54Zayante sandstone
    Numeric Ptype (Source: OFR-93-0693)
    Range of values
    Linear map features (Source: OFR-93-0693)
    Line type (Source: OFR-93-0693)
    contact, approx. locatedContact whose position is not precisely known
    contact, certainObserved contact
    contact, concealedConcealed contact whose position is inferred
    contact, inferredContact whose position is inferred
    contact, inferred, queriedContact whose position is inferred and questionable
    fault, approx. locatedFault whose position is not precisely known
    fault, certainObserved fault
    fault, concealedConcealed fault whose position is inferred
    fault, inferred, queriedFault whose position is inferred and questionable
    map boundaryBoundary of mapped area
    scratch boundaryPosition of scratch boundary
    scratch boundary, countylineLocation of countyline
    water boundaryBoundary of body of water
    Source of line information (Source: OFR-93-0693)
    0Source information unknown
    1Helley, Lajoie, and others, 1979
    2Ellen and Wentworth, in press
    3Breabb, 1989
    4Water boundaries extracted from the 1:125,000 base scan
    5Water boundaries extracted from the 1:62,500 base scan
    6County line extracted from the 1:125,000 base scan
    Digital map point coverage (same attributes as polygon coverage SSFB_M1.PAT) (Source: OFR-93-0693)

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Carl 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 access to ARC/INFO made possible by the Menlo Park GIS Research Laboratory of the U.S. Geological Survey. E.J. Helley provided author linework of the surficial map for scanning. D.L. Knifong assigned UNIT values to the polygons for the Santa Cruz geologic map. D.S. Aitken of the GIS lab provided access to a digital version of the color boundaries for the geologic map of Santa Cruz County and scanned and vectorized the fault plates for that map and the hillside materials map and the several layers of the topographic base map. N.L. Hoskin provided access to working files of the color boundaries and polygon tags for the hillside materials map. S.D. Ellen and E.E. Brabb shared their geologic expertise about the region.
  3. To whom should users address questions about the data?
    Wentworth, Carl MJR
    Mail Stop 977, USGS
    345 Middlefield Rd
    Menlo Park, CA

    650-329-4950 (voice)

Why was the data set created?

The purpose of this digital map database is to provide a map of the distribution and character of the geologic materials following the pattern of its progenitors, Wentworth and others (1985) and Ellen and Wentworth (in press at the time of the release).

How was the data set created?

  1. From what previous works were the data drawn?
    Wentworth and others (1985) (source 1 of 2)
    Wentworth, C.M., Ellen, S.D., Frizzell, Jr., V.A., and Schlocker, Julius, 1985, Map of hillside materials and description of their engineering character, San Mateo County, California: U.S. Geological Survey Miscellaneous Investigations Series Map I-1275-D.

    Type_of_Source_Media: paper
    Source_Scale_Denominator: 62500
    Source_Contribution: Preliminary mapping of area
    Ellen and Wentworth (in press) (source 2 of 2)
    Ellen, S.D., and Wentworth, C.M., in press at time of release, Hillside materials and slopes of the San Francisco Bay Region, California: U.S. Geological Survey Professional Paper PP-1357.

    Type_of_Source_Media: paper
    Source_Scale_Denominator: 125000
    Source_Contribution: Preliminary mapping of the area
  2. How were the data generated, processed, and modified?
    Date: unknown (process 1 of 2)
    The digital map was compiled on a 1:125,000 topographic base* (scanned and vectorized version of sheet 3, U.S. Geological Survey, 1970) from three regional compilations of 1970's data. Two of the sources were compiled in the 1970's on the 1:125,000 base and address the surficial deposits (flatland deposits, Helley and others, 1979) and the bedrock (hillside materials, Ellen and Wentworth, in press) of the 9-county San Francisco Bay region. (The San Mateo County part of the hillside materials map is based, in turn, on Wentworth and others, 1985.) The geologic map of Santa Cruz County (Brabb, 1989), also based largely on 1970's and older data, was compiled on the same base enlarged to a scale of 1:62,500. Inked or scribed linework for these sources was scanned (400 or more lines per inch), converted from raster to vector format, imported into ARC/INFO (version 4), and hand edited and combined into a single coherent map. The original material used to digitize the surficial linework was author manuscript (ink on mylar) and for the hillside materials and Santa Cruz County geologic maps was print publication files that had previously been prepared for color separation by scribing and scanning, together with scribed fault plates that were separately scanned and vectorized. The faults and color boundaries were combined interactively by hand for each source separately using ALACARTE (the color boundaries were tagged as contacts or replaced by faults, as appropriate). The fault plate for Santa Cruz County required a slight xy shift and rotation in the computer to produce a reasonable fit with the color boundaries.
    Date: 17-Aug-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

    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?
    Faults are distinguished in the database only as part of the physical character of the geologic materials 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.
  5. How consistent are the relationships among the observations, including topology?
    The database delineates map units that are identified by general age and lithology and by the map labels used in the compilation sources. Stratigraphic names are included for those units named in the sources as a further means of characterization.

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 93-693
  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.
  4. How can I download or order the data?

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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