Geologic Map of the Lake Mathews 7.5' Quadrangle, Riverside County, California

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Geologic Map of the Lake Mathews 7.5' Quadrangle, Riverside County, California
This data set maps and describes the geology of the Lake Mathews 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.
All but the southeast corner of the Lake Mathews quadrangle is in the Perris block, a relatively stable, rectangular-in-plan area located between the Elsinore and San Jacinto fault zones in the northern Peninsular Ranges Province. In the southwest corner of the quadrangle, a small triangular-shaped area that is part of the Santa Ana Mountains structural block, is separated from the Perris block by a short segment of the Elsinore fault zone. The active Elsinore fault zone, a major component of the San Andreas fault system, consists of a series of en echelon northwest-striking right lateral faults located in a graben-like structure.
There is limited relief within the quadrangle because of the presence of two prominent erosion surfaces. The lower Perris surface (about 1,500 feet elevation) has low relief and dominates the physiography of the northern half of the quadrangle. This surface is discontinuously covered by coarse-grained, clastic, non-marine sedimentary rocks of the middle Miocene-age Lake Mathews Formation. A higher Gavilan-Lakeview surface (about 2,100 feet elevation) occurs in the eastern part of the quadrangle, and is locally covered by small exposures of fluvial conglomerate that contain exotic clasts of red rhyolite.
The Lake Mathews quadrangle is underlain almost entirely by Cretaceous and older basement rocks. Two different types of metamorphic rocks are exposed in the quadrangle. In the northeast is a northwest trending exposure of amphibolite grade biotite-bearing schist of probable Mesozoic age. This schist separates massive textured granitic rocks to the west from foliated and layered granitic rocks to the east. The large expanse of metamorphic rock between Temescal Wash and Lake Mathews is low metamorphic grade, typically siliceous, but highly variable in composition.
Cretaceous plutonic rocks in the quadrangle are part of the composite Peninsular Ranges batholith, and represent a wide variety of mafic to intermediate composition granitic rocks. Most are massive-textured with the exception of the crudely foliated biotite-hornblende tonalite of the Val Verde pluton in the northeast corner of the quadrangle. The Cajalco pluton, which consists of biotite monzogranite, granodiorite and lesser amounts of biotite-hornblende granodiorite, by far, accounts for most of the granitic rocks in the quadrangle. It is a shallow level pluton emplaced by magmatic stoping into largely intermediate composition volcanic and volcanoclastic rocks and metamorphic rocks in its western and southern extent and into gabbroic rocks in its northern extent. The pluton appears to be tilted up to the northeast with the texture of the rock changing from subporphyritic rock containing beta-quartz-appearing phenocrysts in the southwestern part of the pluton to coarser-grained hypautomorphic texture rock in the eastern part. Located in the upper part of the pluton and in overlying wall rock in the shallow western part of the pluton is widespread metasomatic tourmaline rock. Locally parts of the pluton have been completely replaced by tourmaline but more commonly tourmaline occurs in discrete thin zones, generally along joints. Some of the larger masses of tourmaline rock, locally termed tourmaline 'blowouts', contain cassiterite and sulfides. One large mass of cassiterite-bearing tourmaline rock supported a tin mining and smelting operation.
In the southeast corner of the quadrangle is the northwest part of the Gavilan ring complex. This shallow plutonic complex centered southeast of the quadrangle is predominantly tonalitic composition, characterized by the presence of hypersthene, which is rarely found in Peninsular Ranges batholithic rocks of intermediate composition.
Most of the southern part of the quadrangle is underlain by siliceous volcanic and volcanoclastic rocks considered to be coeval with the batholith and which are considered to represent the supra-part of the batholithic magmatism. These rocks generally range in composition from rhyolite to andesite, but latite is probably the predominate composition.
Paleocene continental rocks of the Silverado Formation occur within the Elsinore fault zone and nearby on the adjacent Perris block. Clay-rich parts of the Silverado Formation have been mined for industrial clay. Near Arlington Mountain, in the northwest part of the quadrangle, are two very small occurrences of conglomerate that consist of exotic welded-tuff clasts and a few exotic bedded quartzite clasts. Extensive Quaternary alluvial deposits are found along the south side of Lake Mathews and in the Temescal Valley along the Elsinore fault zone.
  1. How might this data set be cited?
    Morton, Douglas M., and F. Harold Weber, Jr., 2001, Geologic Map of the Lake Mathews 7.5' Quadrangle, Riverside County, California: U.S. Geological Survey Open-File Report 01-479, U.S. Geological Survey, Menlo Park, California.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -117.5000909
    East_Bounding_Coordinate: -117.37490912
    North_Bounding_Coordinate: 33.87500019
    South_Bounding_Coordinate: 33.74997833
  3. What does it look like? (JPEG)
    Reduced-size image of the map, 278x453 pixels, 32-bit RGB true color, 43 kbytes. (PDF)
    Printable map sheet, 1.4 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 (281)
      • String (703)
      • GT-polygon composed of chains (282)
    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: -117.4375
      False_Easting: 0.00000
      False_Northing: 0.00000
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 1.000373721122
      Ordinates (y-coordinates) are specified to the nearest 1.000373721122
      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 Lake Mathews 7.5' quadrangle comprises three ARC/INFO coverages, of which two contain geologic data, and one contains cartographic features: lkm_geo (geology), lkm_str (structural data), and lkm_ano (annotation and leaders).
    Geologic data represented by line entities and the polygons they delineate are contained in the coverage LKM_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                   8    18     F      5
        9  PERIMETER              8    18     F      5
       17  LKM_GEO#               4     5     B      -
       21  LKM_GEO-ID             4     5     B      -
       25  LABL                  35    35     C      -
       60  PLABL                 35    35     C      -
       95  SHD                    3     3     I      -
       98  SHDFIL                 3     3     I      -
      101  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                 8    18     F      5
       25  LKM_GEO#               4     5     B      -
       29  LKM_GEO-ID             4     5     B      -
       33  LTYPE                 60    60     C      -
       93  L-SYMB                 3     3     I      -
    Geologic units (LABL) and their corresponding names (NAME) identified in the Lake Mathews 7.5' quadrangle
    geologic map unit label, in plain text
    KcgMonzogranite of Cajalco pluton
    KcgbGranodiorite and gabbro, undifferentiated of Cajalco pluton
    KcgdGranodiorite of Cajalco pluton
    KcgqGranodiorite and quartz latite, undifferentiated of Cajalco pluton
    KctTonalite of Cajalco pluton
    KctoTourmalinized monzogranite and granodiorite
    KgtMassive textured tonalite of Gavilan ring complex
    KgtfFoliated tonalite of Gavilan ring complex
    KguGranite, undifferentiated
    KhgHeterogeneous granitic rocks
    KtTonalite, undifferentiated
    KvemEstelle Mountain volcanics of Herzig (1991)
    KvrRhyolite of Estelle Mountain volcanics of Herzig (1991)
    KvsIntermixed Estelle Mountain volcanics of Herzig (1991) and sedimentary rocks
    KvspiIntrusive rocks associated with Santiago Peak Volcanics
    KvtTonalite of Val Verde pluton
    Lake MathewsLake Mathews
    MzuMesozoic metasedimentary rocks, undifferentiated
    QTtConglomerate of Temescal Wash
    QafArtificial fill
    QoaOld axial channel deposits
    QoaaOld axial channel deposits, arenaceous
    QoagOld axial channel deposits, gravel
    QofOld alluvial fan deposits
    QofaOld alluvial fan deposits, arenaceous
    QofgOld alluvial fan deposits, gravel
    QovaOld alluvial valley deposits, arenaceous
    QvoaVery old axial channel deposits
    QvoagVery old axial channel deposits, gravel
    Qvof1gVery old alluvial fan deposits, unit 1, gravel
    QvofaVery old alluvial fan deposits, arenaceous
    QvofgVery old alluvial fan deposits, gravel
    QyaaYoung axial channel deposits, arenaceous
    QyagYoung axial channel deposits, gravel
    QyfYoung alluvial fan deposits
    QyfaYoung alluvial fan deposits, arenaceous
    QyfgYoung alluvial fan deposits, gravel
    QyvaYoung alluvial valley deposits, arenaceous
    TcgaConglomerate of Arlington Mountain
    TcgrRhyolite-clast conglomerate of Lake Mathews area
    TlmLake Mathews Formation
    Tlm?Lake Mathews Formation
    TsiSilverado Formation
    Geological map unit label used to generate plot labels with relevant stratigraphic symbols. The geologic units with LABL designating Mesozoic (Mz) have a keystroke substitute character, }, that calls their corresponding symbols from the Geoage 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
    polygon fill pattern (as integer value) from shadeset geology2.shd
    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).
    Kcto, zone of tourmalinized monzogranite and granodiorite 
    contact, certain 
    fault, approx. located 
    fault, certain 
    fault, concealed 
    map 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, LKM_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
    • F. Harold Weber, Jr.
  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, and (3) the Southern California Areal Mapping Project (SCAMP).
  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 Lake Mathews 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: 1993 (process 1 of 7)
    Field mapping and aerial photograph interpretation; iterative process (D.M. Morton).
    Date: 1976 (process 2 of 7)
    Field mapping (F.H. Weber, Jr.).
    Date: 1999 (process 3 of 7)
    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 (V.M. Diep and U. Edwards-Howells).
    Date: 2001 (process 4 of 7)
    Description of map units and correlation of map units (F.K. Miller).
    Date: 2001 (process 5 of 7)
    Revision of description of map units and correlation of map units (Kelly Corriea).
    Date: 07-Dec-2001 (process 6 of 7)
    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/lkm_ofr/lkm_geo
    Date: 07-Dec-2001 (process 7 of 7)
    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 Lake Mathews 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.
    Nation-wide 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, lineation, 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 Lake Mathews 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 Lake Mathews 7.5' geologic-map database should be used to evaluate and understand the geologic character of the Lake Mathews 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 01-479
  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 Lake Mathews 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, with TIFF image of base map in format ARCE (version 7.2.1) Size: 1.8
      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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