Geologic Map of the Steele Peak 7.5' Quadrangle, Riverside County, California

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What does this data set describe?

Geologic Map of the Steele Peak 7.5' Quadrangle, Riverside County, California
This data set maps and describes the geology of the Steele Peak 7.5' quadrangle, Riverside County, California. Created using Environmental Systems Research Institute's ARC/INFO software, the data base consists of the following items: (1) a map coverage containing geologic contacts and units, (2) a coverage containing structural data, (3) a coverage containing geologic unit annotation and leaders, and (4) attribute tables for geologic units (polygons), contacts (arcs), and site-specific data (points). In addition, the data set includes the following graphic and text products: (1) a postscript graphic plot-file containing the geologic map, topography, cultural data, a Correlation of Map Units (CMU) diagram, a Description of Map Units (DMU), and a key for point and line symbols, and (2) PDF files of the Readme (including the metadata file as an appendix), and the graphic produced by the Postscript plot file.
The Steele Peak quadrangle is located in the northern part of the Peninsular Ranges Province within the central part of the Perris block, a relatively stable, rectangular in plan area located between the Elsinore and San Jacinto fault zones.
The quadrangle is underlain by Cretaceous and older basement rocks. Cretaceous plutonic rocks are part of the composite Peninsular Ranges batholith. A wide variety of mafic to intermediate composition granitic rocks occur in the quadrangle, and are mainly of tonalitic composition, but range from monzogranite to gabbro. Most rock units are faintly to intensely foliated, compositionally heterogenous, and contain varying amounts of meso-and melanocratic discoidal-shaped inclusions. Some rocks are composed almost wholly of inclusion material and some are migmatitic. Included within these granitic rocks are septa not shown on the geologic map of Paleozoic(?) schist of upper amphibolite metamorphic grade.
Metamorphic rocks of primarily Mesozoic age occur in a discontinuous belt extending from the southeast to the northwest corner of the quadrangle. Most of these rocks are well foliated biotite-bearing schist. Near the southern edge of the quadrangle phyllitic rocks dominate. Northwestward, metamorphism increases from greenschist or sub-greenschist grade near the south edge of the quadrangle to sillimanite-bearing schist of upper amphibolite grade in the vicinity of Cajalco Road.
Biotite-hornblende tonalite of the relatively large Val Verde pluton dominates the northeastern half of the quadrangle. In most places this tonalite has a northwest oriented crude to well developed planar fabric produced by oriented biotite and hornblende. Schlieren and massive clots of mafic tonalite locally occur. Discoidal- to pancake-shaped mafic inclusions are widespread and are oriented in the plane defined by the biotite and hornblende. This planar fabric typically dips moderately to the northeast, but locally shallows to a horizontal to subhorizontal planar fabric, or fades to an isotropic fabric.
West of the Val Verde pluton are a number of plutons having fabrics ranging from massive isotropic to foliated. Compositions of these plutons range from monzogranite to pyroxene gabbro. Most of these granitic rocks fall within the composition range from monzogranite to tonalite, and are part of the composite Gavilan ring complex. Hypersthene is a characteristic mineral of most of the rocks of this complex, which includes black hypersthene-bearing monzogranite that has been quarried as a source of 'black granite' building stone. Several inactive gold mines, e.g., Goodhope, Gavilan, and Santa Rosa mines that constituted the Pinacate mining district, are located in the Gavilan ring complex.
In the center of the Gavilan ring complex is the near circular Arroyo del Toro pluton, a massive-textured granodiorite essentially devoid of inclusions. Only the northern half of this pluton is located in the quadrangle. Some rock of this pluton was quarried for building stone. The southwestern corner of the quadrangle is underlain by siliceous volcanic and volcanoclastic rock considered to be coeval with the batholith and be the supra-part of the batholithic magmatism. Most of these volcanic rocks range in composition from rhyolite to andesite with latitic composition rocks predominating.
In the northeastern part of the quadrangle is the proximal parts of a Pleistocene alluvial fan complex.
The geologic map data base contains original U.S. Geological Survey data generated by detailed field observation recorded on 1:24,000 scale aerial photographs. The map was created by transferring lines from the aerial photographs to a 1:24,000 scale topographic base. The map was digitized and lines, points, and polygons were subsequently edited using standard ARC/INFO commands. Digitizing and editing artifacts significant enough to display at a scale of 1:24,000 were corrected. Within the database, geologic contacts are represented as lines (arcs), geologic units are polygons, and site-specific data as points. Polygon, arc, and point attribute tables (.pat, .aat, and .pat, respectively) uniquely identify each geologic datum.
  1. How might this data set be cited?
    Morton, Douglas M., 2001, Geologic Map of the Steele Peak 7.5' Quadrangle, Riverside County, California: U.S. Geological Survey Open-File Report 01-449, U.S. Geological Survey, Menlo Park, California.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -117.37509096
    East_Bounding_Coordinate: -117.24990904
    North_Bounding_Coordinate: 33.87499995
    South_Bounding_Coordinate: 33.74998418
  3. What does it look like? (JPEG)
    Reduced-size image of the map sheet, 400x586 pixels, 32-bit RGB true color, 85 kbytes. (PDF)
    Printable map sheet, 1.6 megabytes.
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 2001
    New data obtained
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: vector digital data
  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):
      • Point (276)
      • String (635)
      • GT-polygon composed of chains (277)
    2. What coordinate system is used to represent geographic features?
      The map projection used is Polyconic.
      Projection parameters:
      Latitude_of_Projection_Origin: 33.75
      Longitude_of_Central_Meridian: -117.3125
      False_Easting: 0.00000
      False_Northing: 0.00000
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 1.0
      Ordinates (y-coordinates) are specified to the nearest 1.0
      Planar coordinates are specified in Meters
      The horizontal datum used is North American Datum of 1927.
      The ellipsoid used is Clarke 1866.
      The semi-major axis of the ellipsoid used is 6378206.4.
      The flattening of the ellipsoid used is 1/294.98.
  7. How does the data set describe geographic features?
    Version 1.0 of the Steele Peak 7.5' quadrangle comprises three ARC/INFO coverages, of which two contain geologic data, and one contains cartographic features: stp_geo (geology), stp_str (structural data), and stp_ano (annotation and leaders).
    Geologic data represented by line entities and the polygons they delineate are contained in the coverage STP_GEO. For display purposes, the annotation coverage contains one annotation subclass: anno.geo contains unit labels.
    Geological point data includes site-specific information describing the types and the orientation of bedding, foliation, and lineations. Annotation is respective dip and plunge values associated with individual point data.
        1  AREA                   4    12     F      3
        5  PERIMETER              4    12     F      3
        9  STP5_GEO#              4     5     B      -
       13  STP5_GEO-ID            4     5     B      -
       17  LABL                  35    35     C      -
       52  PLABL                 35    35     C      -
       87  SHD                    3     3     I      -
       90  SHDFIL                 3     3     I      -
       93  NAME                 200   200     C      -
        1  FNODE#                 4     5     B      -
        5  TNODE#                 4     5     B      -
        9  LPOLY#                 4     5     B      -
       13  RPOLY#                 4     5     B      -
       17  LENGTH                 4    12     F      3
       21  STP5_GEO#              4     5     B      -
       25  STP5_GEO-ID            4     5     B      -
       29  LTYPE                 35    35     C      -
       64  L-SYMB                 3     3     I      -
    Geologic units (LABL) and their corresponding names (NAME) identified in the Steele Peak 7.5' quadrangle
    geologic map unit label, in plain text
    KatgGranodiorite of Arroyo del Toro pluton
    KcgdGranodiorite of Cajalco pluton
    KgGranitic dikes
    KgctCoarse-grained biotite-hornblende tonalite of Gavilan ring complex
    KgdGranodiorite, undifferentiated
    KggHypersthene monzogranite of Gavilan ring complex
    KghtHeterogeneous tonalite of Gavilan ring complex
    KgtMassive textured tonalite of Gavilan ring complex
    KgtfFoliated tonalite of Gavilan ring complex
    KgtiTonalite containing abundant mesocratic inclusions, Gavilan ring complex
    KguGranite, undifferentiated
    KhgHeterogeneous granitic rocks
    KpGranitic pegmatite dikes
    KtTonalite, undifferentiated
    KvemEstelle Mountain volcanics of Herzig (1991)
    KvrRhyolite of Estelle Mountains volcanics of Herzig (1991)
    KvtVal Verde tonalite
    KvtiInclusion-rich tonalite of Val Verde pluton
    KvtkPotassium feldspar-bearing tonalite of Val Verde pluton
    MzqQuartz-rich rocks
    MzuMetasedimentary rocks, undifferentiated
    QafArtificial fill
    QoaaOld axial channel deposits, arenaceous
    QofaOld alluvial fan deposits, arenaceous
    QovaOld alluvial valley deposits, arenaceous
    QvoaaVery old axial channel deposits, arenaceous
    QvofaVery old alluvial fan deposits, arenaceous
    QyaaYoung axial channel deposits, arenaceous
    QyfaYoung alluvial fan deposits, arenaceous
    QywaYoung alluvial wash deposits, arenaceous
    TcgConglomerate in the Lake Mathews area
    TcgrRhyolite-clast conglomerate of Lake Mathews area
    TlmLake Mathews Formation
    Geological map unit label used to generate plot labels with relevant stratigraphic symbols. The geologic units with LABL designating Mesozoic (Mz) have keystroke substitute characters, }, that call their corresponding symbols from the Stratagem Font Group. Geologic map unit labels will plot on derivative map plots with appropriate stratigraphic symbols if PLABL is used as the source for unit labels.
    polygon color (as integer value) from shadeset alc1.shd (included in the data package)
    polygon fill pattern (as integer value) from shadeset geology2.shd (included in the data package)
    Geologic name of map unit (see list under LABL attribute)
    Geologic features such as contacts and faults that bound rock-unit polygons
    Description of types of lines on the geologic map (contact, fault).
    Kg, granitic dike 
    Kp, pegmatite dike 
    contact, certain 
    fault, inferred 
    map boundary 
    scratch boundary 
    stores appropriate line symbol value from the lineset geoscamp2.lin
    Geological point data includes site-specific information describing the types and the orientation of bedding, foliation, and lineations. One annotation subclass is included in the geologic points coverage, STP_STR which displays the respective dip and plunge values associated with individual point data.
    describes type of point data (bedding, horizontal bedding, foliation)
    Coded integer value that relates point to cartographic point symbol in markerset geoscamp2.mrk
    Azimuthal strike of planar feature
    Dip of planar feature
    Annotation leaders
    Coded integer value (1) that relates arcs to cartographic line symbol in lineset geoscamp2.lin

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Douglas M. Morton
  2. Who also contributed to the data set?
    Geologic mapping and digital preparation of this report were sponsored jointly by (1) the National Cooperative Geologic Mapping Program of the U.S. Geological Survey, (2) the California Division of Mines and Geology, (3) the Southern California Areal Mapping Project (SCAMP), and (4) the U.S. Air Force.
  3. To whom should users address questions about the data?
    Douglas M Morton
    U.S. Geological Survey, GEO-WRG-NGM
    UC - Riverside
    Riverside, CA

    909-276-6397 (voice)
    909-276-6295 (FAX)

Why was the data set created?

The data set for the Steele Peak 7.5' quadrangle was prepared under the U.S. Geological Survey Southern California Areal Mapping Project (SCAMP) as part of an ongoing effort to develop a regional geologic framework of southern California, and to utilize a Geographic Information System (GIS) format to create regional digital geologic databases. These regional databases are being developed as contributions to the National Geologic Map Database of the National Cooperative Geologic Mapping Program of the USGS.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 1991 (process 1 of 5)
    Field mapping and aerial photograph interpretation; iterative process (D.M. Morton).
    Date: 1999 (process 2 of 5)
    Digitization of geologic linework and point data from a scale-stable cartographic base of quadrangle. ARC/INFO database established; cleanup of artifacts; polygon, arc, and point attribute tables established. Digitizing and editing artifacts significant enough to display at a scale of 1:24,000 were corrected (R.M. Alvarez and V.M. Diep).
    Date: 2001 (process 3 of 5)
    Description of map units and correlation of map units (F.K. Miller).
    Date: 19-Sep-2001 (process 4 of 5)
    First draft of metadata created by Michael J. Watson using FGDCMETA.AML ver. 1.2 05/14/98 on ARC/INFO data set /scamp26/mwatson/stp_ofr/stp5_geo
    Date: 19-Sep-2001 (process 5 of 5)
    Creation of original metadata record Person who carried out this activity:
    U.S. Geological Survey
    Attn: Rachel M.H. Alvarez
    U.S. Geological Survey
    Department of Earth Sciences
    University of California, Riverside
    Riverside, California

    (909) 276-6397 (voice)
    (909) 276-6295 (FAX)
  3. What similar or related data should the user be aware of?
    Morton, D.M., 1999, Preliminary digital geologic map of the Santa Ana 30'x60' quadrangle, southern California, version 1.0.: U.S. Geological Survey Open-File Report 99-172, U.S. Geological Survey, California.

    Online Links:

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

  1. How well have the observations been checked?
    Geologic-map units in the Steele Peak quadrangle database were described using standard field methods. Consistent with these methods, the database author has assigned standard geologic attributes to geologic lines, points, and polygons identified in the database.
    Nationwide geologic map accuracy standards have not been developed and adopted by the U.S. Geological Survey and other earth-science entities. Until such standards are adopted, the SCAMP project has developed internal map-accuracy standards for 1:24,000-scale geologic maps produced by the project.
    Geologic lines and points on 1:24,000 scale geologic maps are judged to meet SCAMP's internal map-accuracy standards if they are located to within +/-15 meters, relative to topographic or cultural features on the base map.
    On any derivative geologic-map plot, line data that are judged to meet the SCAMP internal map-accuracy standard are denoted by solid lines; line data that may not meet the SCAMP internal map-accuracy standard are denoted by dashed or dotted lines. There is no cartographic device for denoting the map-accuracy for geologic-point data (e.g., symbols representing bedding, foliation, lineations, etc.).
  2. How accurate are the geographic locations?
    The maximum transformation RMS error acceptable for a 7.5' quadrangle transformation and data input is 0.003 (1.8 meters). Horizontal positional accuracy was checked by visual comparison of hard-copy plots with base-stable source data.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    The geologic map database of the Steele Peak 7.5' quadrangle contains new data that have been subjected to rigorous review and are a substantially complete representation of the current state of knowledge concerning the geology of the quadrangle.
  5. How consistent are the relationships among the observations, including topology?
    Polygon and chain-node topology present.
    The areal extent of the map is represented digitally by an appropriately projected (polyconic projection), mathematically generated box. Consequently, polygons intersecting the lines that comprise the map boundary are closed by that boundary. Polygons internal to the map boundary are completely enclosed by line segments which are themselves a set of sequentially numbered coordinate pairs. Point data are represented by coordinate pairs.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
The Steele Peak 7.5' geologic-map database should be used to evaluate and understand the geologic character of the Steele Peak 7.5' quadrangle as a whole. The data should not be used for purposes of site-specific land-use planning or site-specific geologic evaluations. The database is sufficiently detailed to identify and characterize many actual and potential geologic hazards represented by faults and landslides and posed by ground subsidence and earthquake-generated ground shaking. However, it is not sufficiently detailed for site-specific determinations or evaluations of these features. Faults shown do not take the place of fault-rupture hazard zones designated by the California State Geologist (see Hart, 1988).
Use of this digital geologic-map database should not violate the spatial resolution of the data. Although the digital form of the data removes the constraint imposed by the scale of a paper map, the detail and accuracy inherent in map scale are also present in the digital data. The fact that this database was compiled and edited at a scale of 1:24,000 means that higher resolution information may not have been uniformly retained in the dataset. Plotting at scales larger than 1:24,000 will not yield greater real detail, although it may reveal fine-scale irregularities below the intended resolution of the database. Similarly, although higher resolution data is incorporated in most of the map, the resolution of the combined output will be limited by the lower resolution data.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey Information Services
    Box 25286 Denver Federal Center
    Denver, Colorado

    (303)202-4700 (voice)
    (303)202-4693 (FAX)
  2. What's the catalog number I need to order this data set? USGS Open-File Report 01-449
  3. What legal disclaimers am I supposed to read?
    The U.S. Geological Survey (USGS) provides these geographic data "as is." The USGS makes no guarantee or warranty concerning the accuracy of information contained in the geographic data. The USGS further makes no warranties, either expressed or implied as to any other matter whatsoever, including, without limitation, the condition of the product, or its fitness for use lies entirely with the user. Although these data have been processed successfully on computers at the USGS, no warranty, expressed or implied, is made by the USGS regarding the use of these data on any other system, nor does the fact of distribution constitute or imply any such warranty.
    In no event shall the USGS have any liability whatsoever for payment of any consequential, incidental, indirect, special, or tort damages of any kind, including, but not limited to, any loss of profits arising out of use of or reliance on the geographic data or arising out of the delivery, installation, operation, or support by USGS.
    This digital geologic map database of the Steele Peak 7.5' quadrangle, 1:24,000 map-scale, and any derivative maps thereof, is not meant to be used or displayed at any scale larger than 1:24,000 (e.g., 1:12,000).
  4. How can I download or order the data?
    • Availability in digital form:
      Data format: Geologic units and structural features; including TIFF image of base map in format ARCE (version 7.2.1) Size: 1.9
      Network links:
    • Cost to order the data: none

Who wrote the metadata?

Last modified: 10-Jun-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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