DATABASE FOR THE EAST HALF OF "PRELIMINARY GEOLOGIC MAP OF THE BLYTHE 30' BY 60' QUADRANGLE, CALIFORNIA AND ARIZONA" (U.S. GEOLOGICAL SURVEY OPEN-FILE REPORT 90-497) By Paul Stone 2006 U.S. Geological Survey Data Series 225 DESCRIPTION OF DATA FILES INTRODUCTION This report contains a digital geologic map database created from the east half of a previously published geologic map entitled, "Preliminary Geologic Map of the Blythe 30' by 60' Quadrangle, California and Arizona" (Stone, 1990). That map was published as U.S. Geological Survey (USGS) Open-File Report 90-497 and is available from the USGS in the form of paper copies reproduced from a scale- stable film original. The scale of the previously published map is 1:100,000. The digital database of this report is intended to contain exactly the same geologic data as the east half of the published map that comprises USGS Open- File Report 90-497. No geologic line, polygon, or point data have been intentionally added, subtracted, or modified from the original map. The database has been carefully prepared and reviewed to ensure that it constitutes a faithful digital representation of the geologic data presented in the original analog map. A digital geologic map database of the west half of the Blythe 30' by 60' quadrangle also is available. That database was published as part of U.S. Geological Survey Scientific Investigations Map (SIM) 2922 (Stone, 2006). Unlike the database of the present report, the database of SIM 2922 contains new geologic data in addition to, or in place of, the data contained in the original map of Open-File Report 90-497. This document describes the types and contents of files comprising the database. Information on how to extract and plot the map also is provided. This publication includes ARC/INFO (Environmental Systems Research Institute, http://www.esri.com) version 8.1.2 coverages and associated tables; Portable Document Format (PDF) files of four illustrations that accompany the database; and a text file of FGDC-compliant metadata for the report. GEOLOGIC MAP DATABASE FILES AND ASSOCIATED FILES The files listed in this section are in a compressed tar file named ds225.tar.gz; see section below titled, SOFTWARE UTILITIES. ARC/INFO Coverage Contains Interchange file ble_geo.e00 ble_geo Contacts, faults, and rock units ble_str.e00 ble_str Folds; attitudes and dip values The directory, info/, is produced in the process of importing interchange files to ARC coverages in ARC/INFO. The info/ directory contains: Polygon attribute table ble_geo.pat Arc attribute tables ble_geo.aat, ble_str.aat Point attribute table ble_str.pat FILES FOR VIEWING AND PLOTTING PORTABLE DOCUMENT FORMAT (PDF) FILES bl_map.pdf Map of Blythe 30' by 60' quadrangle showing major geographic features and area covered by geologic database of this report. bl_cmu.pdf Correlation of map units diagram for "Preliminary Geologic Map of the Blythe 30' by 60' quadrangle, California and Arizona" (copied from USGS Open File Report 90-497). bl_index.pdf Illustration showing sources of mapping for "Preliminary Geologic Map of the Blythe 30' by 60' quadrangle, California and Arizona" (copied from USGS Open-File Report 90-497). bl_mccoy.pdf Chart showing correlation of members A through L of the McCoy Mountains Formation with units recognized by Pelka (1973) and Harding and Coney (1985) (copied from USGS Open-File Report 90-497). METADATA ble_met.txt Federal Geographic Data Committee (FGDC) compliant metadata file derived from the digital database SOFTWARE UTILITIES Files that have the .gz file extension were compressed using gzip. Gzip utilities are available free of charge via the Internet at the gzip home page, http://www.gzip.org. The data package is additionally bundled into a single tar (tape archive) file. The individual files must be extracted using a tar utility, available free of charge via the Internet through links on the Common Internet File Formats page, http://www.matisse.net/files/formats.html. One such utility is WinZip, available at http://www.winzip.com (WinZip can also decompress files). HOW TO OBTAIN THE DIGITAL FILES The digital files constituting the geologic map database of this report may be obtained via the Internet from the U.S. Geological Survey publications website. Go to the web page at http://pubs.usgs.gov/ds/2006/225 and follow the directions to download the files. EXTRACTING THE GEOLOGIC MAP DATABASE FROM THE TAR FILE After downloading the files, they must be uncompressed using a gzip utility such as gzip itself or WinZip. The data files must then be extracted using the appropriate tar utility. To do this Type this at the Unix command prompt Uncompress ble.tar.gz gzip -d ble.tar.gz (or use gzip utility to ble.tar of choice) Go to the directory that will cd local_directory hold the directory ble/ (if different from local_directory) Extract the Blythe East tar -xvof {path to tar file}/ble.tar directory from the tar file (or use tar utility of choice) This process will create a directory, ble/, that contains the ARC/INFO interchange files and supporting files. CONVERTING THE ARC/INFO EXPORT FILES ARC interchange (.e00) files are converted to ARC coverages using the ARC command IMPORT with the option COVER. ARC interchange files also can be read by some other Geographic Information Systems. Please consult your GIS documentation to see if you can use ARC interchange files and to determine the procedure for importing them. PORTABLE DOCUMENT FORMAT (PDF) FILES The PDF files are accessed using Adobe Reader software, available free from the Adobe website http://www.adobe.com. Follow instructions at the website to download and install the software. REFERENCES CITED Stone, Paul, 1990, Preliminary geologic map of the Blythe 30' by 60' quadrangle, California and Arizona: U.S. Geological Survey Open-File Report 90-497, scale 1:100,000. Stone, Paul, 2006, Geologic map of the west half of the Blythe 30' by 60' quadrangle, Riverside County, California and La Paz County, Arizona: U.S. Geological Survey Scientific Investigations Map 2922, scale 1:100,000, 21 p. APPENDIX: DESCRIPTION OF MAP UNITS, DESCRIPTION OF MAP SYMBOLS, AND REFERENCES CITED IN U.S. GEOLOGICAL SURVEY OPEN-FILE REPORT 90-497 [This text is presented as an aid to users of the database for the east half of "Preliminary Geologic Map of the Blythe 30' by 60' Quadrangle, California and Arizona" (USGS Open-File Report 90-497). Each section of text has been retyped in its entirety from Open-File Report 90-497; the text has not been intentionally modified from the original except to correct a small number of typographical errors. Notes in brackets have been added for clarity.] DESCRIPTION OF MAP UNITS [Units present in the east half of the Blythe 30' by 60' quadrangle are marked by an asterisk (*). Units without an asterisk are present only in the west half of the quadrangle.] Qw* ALLUVIUM OF MODERN WASHES (QUATERNARY)--Unconsolidated, locally derived gravel and sand Qr* ALLUVIUM OF THE MODERN COLORADO RIVER FLOODPLAIN (QUATERNARY)-- Unconsolidated sand, silt, and mud, largely converted to farmland Qp PLAYA LAKE DEPOSITS (QUATERNARY)--Unconsolidated silt, mud, and evaporitic sediment Qs* WINDBLOWN SAND (QUATERNARY)--Unconsolidated sand dunes and sheets QTa* ALLUVIAL-FAN AND FLUVIAL DEPOSITS (QUATERNARY AND TERTIARY?)-- Unconsolidated to weakly consolidated gravel and sand forming alluvial fans and sediment bodies that underlie terraces of the Colorado River. Alluvial-fan deposits consist of angular, poorly sorted gravel and sand derived from local mountains. Fluvial deposits, primarily exposed adjacent to the Colorado River where they interfinger with alluvial-fan deposits, consist of rounded, moderately to well sorted gravel and sand carried into the area by the ancestral Colorado River. Fluvial deposits commonly are crossbedded. Unit may include equivalents of the dissected fan deposits (unit QTdf), fluvial gravel deposits (unit QTfg), and fluvial sand deposits (QTfs) QTdf* DISSECTED FAN DEPOSITS (QUATERNARY OR TERTIARY)--Weakly consolidated, locally derived gravel and sand (fanglomerate) forming dissected, longitudinal hills and ridges near mountain fronts FLUVIAL DEPOSITS (QUATERNARY OR TERTIARY)--Deposits of weakly consolidated, distantly derived gravel and sand forming dissected hills that protrude a few to several meters above the surrounding fan or terrace surfaces. Interpreted as deposits of the ancestral Colorado River or related streams. Divided into: QTfg* FLUVIAL GRAVEL DEPOSITS--Deposits composed primarily of rounded gravel QTfs FLUVIAL SAND DEPOSITS--Deposits composed primarily of well-sorted, light-colored sand and minor rounded gravel; commonly crossbedded BOUSE FORMATION (PLIOCENE)--Marine to brackish-water sedimentary rocks interpreted to have been deposited in an embayment of the Gulf of California (Metzger and others, 1973). Divided into: Tbs* FINE-GRAINED SEDIMENTARY ROCKS--Thin-bedded mudstone, siltstone, fine-grained sandstone, and limestone. Mudstone is green to red and plane bedded; siltstone and sandstone are tan and plane bedded to crossbedded. Equivalent to the basal limestone unit and the interbedded unit of Metzger and others (1973) Tbt* TUFA--Thin (generally less than 2 m), locally extensive sheets of white to light-gray limestone coating Miocene and older bedrock units. Locally includes minor conglomerate Tbx* SEDIMENTARY BRECCIA (MIOCENE AND OLIGOCENE?)--Unbedded, unsorted deposits of angular gravel and slide blocks, commonly monolithologic. Interpreted as landslide deposits. Largest slide blocks are shown as a separate unit (Tsb) Tsb* SLIDE BLOCKS (MIOCENE AND OLIGOCENE?)--Large, angular blocks and slabs of Mesozoic(?) and Paleozoic carbonate rocks and quartzite interpreted to have been deposited by landslides. Generally brecciated Tvs* VOLCANIC AND SEDIMENTARY ROCKS, UNDIVIDED (MIOCENE AND OLIGOCENE?)--In upper plate of detachment fault in northern Plomosa Mountains. In descending order, general stratigraphic sequence is: fanglomerate; rhyolitic to andesitic volcanic rocks and carbonate slide blocks; limestone, shale, and ash-flow tuff; arkosic sandstone and fanglomerate (Scarborough and Meader, 1983, 1989). Includes ash-flow tuff that has a biotite K-Ar age of 24.6 ą 1.6 Ma (Eberly and Stanley, 1978; age recalculated by the method of Dalrymple, 1979) Tf* FANGLOMERATE (MIOCENE AND OLIGOCENE?)--Distinctly to indistinctly bedded, poorly to well sorted conglomerate and sandstone containing angular, locally derived clasts Tfbx FANGLOMERATE, SEDIMENTARY BRECCIA, AND SLIDE BLOCKS, UNDIVIDED (MIOCENE AND OLIGOCENE?)--In Riverside Mountains Ti* FELSIC INTRUSIVE ROCKS (MIOCENE AND OLIGOCENE?)--Light-colored, fine- grained, hypabyssal intrusive rocks of probable rhyolitic to dacitic composition. In Big Maria Mountains, includes dacite that has a hornblende K-Ar age of 21.7 ą 2.8 Ma (Martin and others, 1982) Tv* VOLCANIC ROCKS (MIOCENE AND OLIGOCENE?)--Rhyolitic to basaltic volcanic rocks including lava flows, flow breccia, airfall tuff, ash-flow tuff, and domes. In Riverside Mountains, includes andesite that has a whole-rock K-Ar age of 23.5 ą 1.0 Ma (Martin and others, 1982). In Plomosa Mountains, includes rhyodacite that has a hornblende K-Ar age of 19.6 ą 0.6 Ma and a biotite K-Ar age of 20.7 ą 0.6 Ma (Miller and McKee, 1971; ages recalculated by the method of Dalrymple, 1979) Tbbm* BASALT OF BLACK MESA (MIOCENE)--Olivine basalt flows that cap Black Mesa and other mesas in the southern Plomosa Mountains. K-Ar whole-rock age of 17.24 ą 0.43 Ma (Shafiqullah and others, 1980) Tls* LIMESTONE AND CALCAREOUS SANDSTONE (MIOCENE)--Fine-grained, thin-bedded calcareous rocks near base of the Tertiary section in central Plomosa Mountains Tg* GRANITE (MIOCENE)--Fine- to coarse-grained biotite granite and hornblende- biotite granite, locally faulted and lineated. U-Pb zircon age of 20.8 ą 3.2 Ma (Knapp, 1989) TKg* GRANITE (TERTIARY AND (OR) CRETACEOUS)--Fine- to coarse-grained biotite granite that intrudes the migmatitic gneiss of Mesquite Mountain (unit KPm). Age is inferred to be either latest Cretaceous and (or) earliest Tertiary (Knapp, 1989) Kgp* GNEISSIC PORPHYRITIC GRANITE (CRETACEOUS)--Distinctly to indistinctly foliated and lineated, medium- to coarse-grained biotite granite to granodiorite containing phenocrysts of potassium feldspar 1 to 5 cm long. Age in northern Dome Rock Mountains is Late Cretaceous on the basis of unpublished U-Pb analysis of zircon (R.M. Tosdal, oral commun., 1990). Rocks in Little Maria Mountains are considered part of the Late Cretaceous Cadiz Valley batholith (K.A. Howard, oral commun., 1990), parts of which intrude the McCoy Mountains Formation in the Coxcomb Mountains 30 km west of the map area. A biotite K-Ar age of 55.2 ą 7.8 Ma, indicating the minimum age of crystallization, has been reported for a sample from the Little Maria Mountains (Martin and others, 1982) Kd* DIORITE (CRETACEOUS)--Foliated and metamorphosed mafic igneous rocks that intrude the McCoy Mountains Formation and some of the underlying Jurassic volcanogenic rocks. Youngest unit intruded is member F of the McCoy Mountains Formation (unit Kmf), which is of Late Cretaceous age. Some of the diorite may possibly be as old as Jurassic in age(Tosdal, 1988) MCCOY MOUNTAINS FORMATION OF HARDING AND CONEY (1985) (CRETACEOUS AND JURASSIC?)--Sandstone and conglomerate; minor shale, mudstone, and siltstone; and rare volcanic rocks. Weakly to strongly foliated; metamorphosed to greenschist and lower amphibolite facies. Maximum exposed thickness approximately 8,000 m. Age range based on stratigraphic position above Jurassic volcanic rocks of the Dome Rock sequence of Tosdal and others (1989) within and outside map area and on intrusion by latest Cretaceous plutons outside map area (Tosdal and others, 1989). Divided into: Kml MEMBER L (CRETACEOUS)--Light-gray arkosic sandstone, conglomerate, and minor shale, all micaceous and phyllitic. Conglomerate clasts are quartzite, volcanic rocks, and granitic rocks. Base and top faulted; exposed thickness approximately 300 m Kmk MEMBER K (CRETACEOUS)--Dark-gray, fine-grained arkosic to volcanic- lithic sandstone; light-gray phyllitic shale; and minor conglomerate. Conglomerate clasts are volcanic and granitic rocks. In fault contact with member L (unit Kml). Exposed thickness approximately 300 m Kmj MEMBER J (CRETACEOUS)--Dark-gray, medium- to coarse-grained arkosic to volcanic-lithic sandstone and conglomerate, interbedded in lowermost part with minor light-gray arkosic sandstone. Conglomerate clasts are granitic and volcanic rocks. Thickness approximately 350 m Kmi MEMBER I (CRETACEOUS)--Light-gray, medium- to coarse-grained arkosic and micaceous sandstone, conglomeratic sandstone, and conglomerate. Conglomerate clasts are quartzite, carbonate rocks, and granitic rocks. Thickness approximately 300 m Kmh MEMBER H (CRETACEOUS)--Light-gray, fine-grained arkosic sandstone, conglomeratic sandstone, and shale, all micaceous and phyllitic. Thickness approximately 50 to 250 m Kmg MEMBER G (CRETACEOUS)--Lower part consists of light-gray to tan phyllitic and calcareous shale; tan calcareous sandstone; and conglomerate containing clasts of quartzite and carbonate rocks. Upper part consists of dark-greenish-gray, fine-grained arkosic to volcanic-lithic sandstone. Basal contact truncates beds in member F (unit Kmf) at a low angle and is interpreted as an intraformational unconformity. Thickness approximately 200 to 600 m. Locally contains late Early Cretaceous or younger fossil wood fragments (Pelka, 1973) Kmf* MEMBER F (CRETACEOUS)--Light- to medium-gray, fine- to coarse- grained arkosic sandstone and conglomerate interbedded with less abundant light- gray phyllitic shale. Dark-gray to dark-greenish-gray, very fine grained to fine-grained volcanic-lithic sandstone and siltstone present in upper part. Conglomerate clasts are granitic rocks, quartzite, volcanic rocks, and minor carbonate rocks. Fines upward from conglomerate and sandstone in lower part to very fine grained sandstone and siltstone in upper part. Basal contact with lower part of McCoy Mountains Formation (unit KJmlu) is locally unconformable. In Dome Rock Mountains, includes a lenticular, 5-m-thick tuff bed that has a U- Pb zircon age of 78 ą 2 Ma (Tosdal, 1988). On this basis, members F through L (units Kmf through Kml) are considered to be of Late Cretaceous age. Thickness in McCoy Mountains approximately 2,600 m KJmlu* LOWER PART, UNDIVIDED (CRETACEOUS OR JURASSIC)--In Dome Rock Mountains, Plomosa Mountains, and Livingston Hills. Lower part of unit consists of tan quartzose sandstone and maroon mudstone and siltstone correlative with member A (unit KJma). Upper part consists of greenish-gray, impure quartzose sandstone, siltstone, mudstone, and minor conglomerate that may be correlative with members C and E (units KJmc and KJme). Conglomerate clasts are quartzite and volcanic rocks. Strata equivalent to members B and D (units KJmb and KJmd) are not recognized. Maximum thickness approximately 2,350 m (Harding, 1982; Harding and Coney, 1985) KJme MEMBER E (CRETACEOUS OR JURASSIC)--Light-gray phyllitic shale; light-gray, dark-gray, and greenish-gray arkosic and volcanic-lithic sandstone; and minor conglomerate and calcareous rocks. Conglomerate clasts are quartzite, volcanic rocks, and granitic rocks. Grayish-orange, calcareous shale present near top. Thickness approximately 1,500 m KJmd MEMBER D (CRETACEOUS OR JURASSIC)--Dark-maroon phyllitic shale and silty to sandy shale interbedded with minor volcanic-lithic sandstone and conglomerate containing clasts of quartzite and volcanic rocks. Locally intruded by diorite (not shown). Thickness approximately 300 m KJmc MEMBER C (CRETACEOUS OR JURASSIC)--Dark-gray to dark-greenish-gray, very fine grained to fine-grained volcanic-lithic sandstone and siltstone; dark- gray to dark-greenish-gray mudstone; and minor conglomerate. Mudstone commonly contains brown calcareous pods and lenses. Conglomerate clasts are quartzite and volcanic rocks. Thickness approximately 1,200 m KJmb MEMBER B (CRETACEOUS OR JURASSIC)--Maroon mudstone and siltstone, commonly containing brown calcareous pods and lenses, interbedded with minor tan quartzite and brown, recrystallized limestone. Thickness approximately 100 m KJma MEMBER A (CRETACEOUS OR JURASSIC)--Tan, fine- to medium-grained quartzite and minor chert- and quartzite-clast conglomerate interbedded with varying amounts of maroon mudstone and siltstone that commonly contain brown calcareous pods and lenses. Thickness approximately 350 m Kgm* GRANITE OF THE MUDERSBACH MINE AREA (CRETACEOUS)--Unfoliated, fine- grained, equigranular granite. K-Ar age of 85 Ma (Amoco Minerals, oral communication, in Stoneman, 1985a; dated mineral not specified) SEDIMENTARY ROCKS OF APACHE WASH (CRETACEOUS OR JURASSIC)--Fining-upward sequence of conglomerate, sandstone, and siltstone, structurally interleaved on low-angle faults with the lower part of the McCoy Mountains Formation (unit KJmlu) in the southern Plomosa Mountains. Age relation to the McCoy Mountains Formation uncertain (Harding and Coney, 1985). Thickness in the vicinity of Apache Wash approximately 1,900 m (Harding, 1980). Divided into: KJas* SILTSTONE--Light- to medium-gray, thin-bedded siltstone and minor fine-grained sandstone. Graded beds common. Thickness approximately 900 m (Harding, 1980) KJac* CONGLOMERATE AND SANDSTONE--Brownish-yellow to reddish-brown, massive conglomerate composed primarily of poorly sorted, angular clasts of quartzite, carbonate rocks, and volcanic rocks; and medium- to dark-gray arkosic sandstone. Conglomerate decreases in abundance upsection and from south to north. In southern part of outcrop area, conglomerate locally contains large, angular blocks and slabs of quartzite and carbonate rocks as much as several hundred meters long, interpreted as slide blocks. Graded beds locally present in sandstone. Thickness in vicinity of Apache Wash approximately 1,000 m (Harding, 1980) JTRu* VOLCANIC AND SEDIMENTARY ROCKS, UNDIVIDED (JURASSIC AND TRIASSIC)--In Big Maria and Riverside Mountains Jv* VOLCANIC ROCKS OF THE DOME ROCK SEQUENCE OF TOSDAL AND OTHERS (1989) (JURASSIC)--Consists primarily of rhyolitic to dacitic, massive volcanic rocks commonly referred to as quartz porphyry. Rocks typically are composed of a microcrystalline, felsic groundmass and phenocrysts of quartz, feldspar, and rare biotite mostly 2 mm in diameter or smaller. Commonly foliated and metamorphosed to greenschist and lower amphibolite facies. Interpreted to have originated as ash-flow tuff, tuff, flows, and hypabyssal porphyry (Tosdal, 1988; Tosdal and others, 1989). Locally includes sandstone and conglomerate composed of reworked volcanic detritus, particularly near top of unit. Geochronologic data indicate a minimum age of early Late Jurassic (Tosdal and others, 1989). In Dome Rock Mountains, locally includes: Jvbu* UPPER BEDDED UNIT--Thin- to thick-bedded, fine-grained, felsic tuff and tuffaceous sedimentary rocks that form the uppermost part of the Dome Rock sequence and concordantly underlie the McCoy Mountains Formation Jvbl* LOWER BEDDED UNIT--Dark, thin-bedded, strongly metamorphosed sedimentary or volcaniclastic rocks that form the lowermost exposed part of the Dome Rock sequence. Rocks are composed largely of calc-silicate minerals, quartz, and biotite Jp* PLUTONIC ROCKS OF THE KITT PEAK-TRIGO PEAKS SUPER-UNIT OF TOSDAL AND OTHERS (1989) (JURASSIC)--Porphyritic granitoid rocks (ranging in composition from granodiorite and quartz monzodiorite to quartz syenite), leucocratic granite, granodiorite, and diorite. Most abundant rock type is medium- to coarse-grained, strongly foliated to unfoliated, porphyritic granodiorite characterized by potassium feldspar phenocrysts 1 to 5 cm long and by clotted mafic minerals, primarily biotite. Leucocratic granite is fine to coarse grained, equigranular, and unfoliated to weakly foliated; it commonly intrudes the porphyritic granitoid rocks. Fine-grained, foliated granodiorite and diorite are present locally. U-Pb zircon ages of porphyritic granodiorite and leucocratic granite of the Kitt Peak-Trigo Peaks super-unit within and outside the map area are approximately 160 to 165 Ma and 158 to 161 Ma, respectively (Tosdal, 1988; Tosdal and others, 1989; R.M. Tosdal, oral commun., 1990). Quartz syenite in the Moon Mountain area has a U-Pb zircon age of 160 ą 15 Ma (Knapp, 1989). Locally divided into: Jplg* LEUCOCRATIC GRANITE--In Dome Rock Mountains Jpgd* FOLIATED GRANODIORITE AND DIORITE--In Little Maria Mountains and northern Dome Rock Mountains Jpgb HORNBLENDE GABBRO--In Big Maria Mountains Jai* ALTERED IGNEOUS ROCKS (JURASSIC)--Light-colored, fine-grained, strongly metamorphosed, foliated, sheared igneous rocks in central Dome Rock Mountains. Probably derived from Jurassic volcanic rocks and (or) leucocratic granite JTRs* SEDIMENTARY ROCKS (JURASSIC AND TRIASSIC)--Variably metamorphosed sedimentary rocks generally consisting of, in descending order: fine-grained, locally crossbedded quartzite correlated with the Jurassic Aztec Sandstone (Hamilton, 1982, 1987); conglomeratic rocks containing clasts of quartzite, carbonate rocks, and granite; greenschist, gypsiferous schist, and calcareous quartzite correlated with the Triassic Moenkopi Formation. Includes conglomerate that unconformably overlies rocks of Proterozic age in the southern Plomosa Mountains (Reynolds and others, 1989; M.F. Lerch, unpublished mapping) TRqm QUARTZ MONZONITE AND MONZODIORITE (TRIASSIC)--Porphyritic biotite quartz monzonite and hornblende monzodiorite in Mule Mountains. Age is about 213 Ma on the basis of unpublished U-Pb analysis of zircon (R.M. Tosdal, written commun., 1990). Petrologically similar to the Late Triassic Mount Lowe Granodiorite (Tosdal, 1988) TRd DIORITE AND GABBRO (TRIASSIC?)--Hornblende diorite and gabbro, locally metamorphosed to amphibolite, in Mule Mountains and Little Chuckwalla Mountains. Age alternatively could be Proterozoic (Tosdal, 1988; R.E. Powell, written commun., 1989). In Little Chuckwalla Mountains, mixed with gneiss of probable Proterozoic age (R.M. Tosdal, written commun., 1990) Pzs* SEDIMENTARY ROCKS, UNDIVIDED (PALEOZOIC)--Variably metamorphosed sedimentary rocks of presumed Paleozoic age consisting of limestone, dolomite, calcitic marble, dolomitic marble, calc-silicate rocks, quartzite, and schist. May include some rocks of Triassic and (or) Jurassic age PCs SEDIMENTARY ROCKS (PERMIAN TO CAMBRIAN)--Complete, or nearly complete, sections of Permian to Cambrian strata equivalent to units PPs and MCs combined, but too thin (owing to tectonic attenuation) to show at the map scale PPs* SEDIMENTARY ROCKS (PERMIAN AND PENNSYLVANIAN)--Variably metamorphosed sedimentary rocks consisting of, in descending order: cherty and non-cherty limestone, dolomite, and marble correlated with the Permian Kaibab Limestone; fine-grained quartz sandstone and quartzite correlated with the Permian Coconino Sandstone; quartzitic calc-silicate schist correlated with the Permian Hermit Shale; calcareous sandstone, quartzite, and calc-silicate rocks correlated with the Permian and Pennsylvanian Supai Formation (Miller, 1970; Hamilton, 1982; Stone and others, 1983). Thickness highly variable because of tectonic attenuation MCs* SEDIMENTARY ROCKS (MISSISSIPPIAN TO CAMBRIAN)--Variably metamorphosed sedimentary rocks consisting of, in descending order: massive limestone and marble correlated with the Mississippian Redwall Limestone or Escabrosa Limestone; massive dolomite and dolomitic marble of probable Devonian and Cambrian age; thinly banded limestone and marble of probable Cambrian age; shale, schist, and thin-bedded quartzite correlated with the Cambrian Bright Angel Shale or Abrigo Formation; feldspathic quartzite and conglomeratic quartzite correlated with the Cambrian Tapeats Sandstone or Bolsa Quartzite (Miller, 1970; Hamilton, 1982; Stone and others, 1983). Thickness highly variable because of tectonic attenuation Ppg* PORPHYRITIC GRANITE AND AUGEN GNEISS (PROTEROZOIC)--Coarse-grained, variably foliated and metamorphosed plutonic rocks characterized by phenocrysts or porphyroblasts of potassium feldspar 1 to 5 cm long. In Big Maria Mountains, includes rocks that have a Middle Proterozoic U-Pb zircon age of about 1400 Ma (L.T. Silver, oral commun. in Hamilton, 1982). In parts of area, unit may include rocks of Early Proterozoic age in addition to rocks of Middle Proterozoic age. Depositionally overlain in several places by strata correlated with the Tapeats Sandstone (lowermost part of unit MCs) Pgg* GRANITE, GNEISS, AND DIORITE, UNDIVIDED (PROTEROZOIC)--In upper plate of detachment fault in northern Plomosa Mountains Pgd* GRANODIORITE (PROTEROZOIC)--Dark-colored, medium-grained, equigranular granodiorite in southern Plomosa Mountains. Early Proterozoic U-Pb zircon age of 1730 to 1750 Ma (L.T. Silver, cited in Miller, 1970) Pd* DIORITE (PROTEROZOIC)--Near Quartzsite Plg* LEUCOCRATIC GRANITE (PROTEROZOIC)--Quartz-rich, pink-weathering granite near Quartzsite Pms* METASEDIMENTARY ROCKS (PROTEROZOIC)--Fine-grained paraschist, paragneiss, and quartzite in Dome Rock Mountains. Age assignment is supported by Rb-Sr and Sm-Nd analysis (F.M. Lerch, written commun., 1990) Pmv* METAVOLCANIC ROCKS (PROTEROZOIC)--Fine-grained, felsic metavolcanic rocks in Dome Rock and Plomosa Mountains. Rocks typically contain quartz phenocrysts 1 to 2 mm in diameter. Age assignment is supported by Rb-Sr and Sm-Nd analysis (Reynolds and others, 1989; F.M. Lerch, written commun., 1990) UNITS OF MIXED AND (OR) UNCERTAIN AGE KPm* MIGMATITIC GNEISS OF MESQUITE MOUNTAIN (CRETACEOUS AND PROTEROZOIC)-- Quartzofeldspathic gneiss and amphibolite of probable Proterozoic protolith age interlayered with synmetamorphic sills of medium- to coarse-grained biotite granite of Late Cretaceous age (Knapp, 1989). U-Pb zircon age of granite crystallization and migmatization is 67.2 ą 1.4 Ma (Knapp, 1989). Gneissic layering is overprinted by younger fabrics interpreted to be related to Miocene extensional deformation (Knapp, 1989) MzPgn* GNEISSIC ROCKS, UNDIVIDED (MESOZOIC AND PROTEROZOIC)--Strongly foliated and lineated mylonitic gneiss and augen gneiss interpreted to be derived primarily from protoliths of Jurassic plutonic rocks and Proterozoic metamorphic and plutonic rocks. Includes some migmatitic gneiss (Hamilton, 1984) MzPfg FINE-GRAINED GNEISS (MESOZOIC OR PROTEROZOIC)--Quartzofeldspathic gneiss of uncertain protolith. Intruded by plutonic rocks of the Kitt Peak- Trigo Peaks superunit (unit Jp) MzPh HORNFELS (MESOZOIC OR PROTEROZOIC)--Dark-brown to green, fine-grained siliceous hornfels in central Dome Rock Mountains. Intruded by plutonic rocks of the Kitt Peak-Trigo Peaks superunit (unit Jp) EXPLANATION OF GEOLOGIC FEATURES SYMBOLIZED BY LINES AND POINTS [Features present in the east half of the Blythe 30' by 60' quadrangle are marked by an asterisk (*). Features without an asterisk are present only in the west half of the quadrangle.] CONTACT* FAULT*--Showing dip where known. Bar and ball on downthrown side. Dotted where concealed THRUST FAULT*--Sawteeth on upper plate. Dotted where concealed. Includes some ductile faults and tectonic slides (Hutton, 1979) with unknown or ambiguous senses of displacement. Largely or entirely of Mesozoic age DETACHMENT FAULT*--Showing dip where known. Hachures on upper plate. Dotted where concealed. Used specifically for low-angle normal faults of known or inferred Tertiary (Miocene) age and large displacement ANTICLINE--Showing direction of plunge ASYMMETRIC ANTICLINE--Showing direction of plunge. Short arrow indicates steeper limb OVERTURNED ANTICLINE SYNCLINE--Showing direction of plunge OVERTURNED SYNCLINE*--Dotted where concealed STRIKE AND DIP OF BEDS--Includes flow structure in some volcanic rocks INCLINED* VERTICAL* HORIZONTAL* OVERTURNED* STRIKE AND DIP OF FOLIATION INCLINED* VERTICAL* STRIKE AND DIP OF FOLIATION AND PLUNGE OF LINEATION* STRIKE AND DIP OF INCLINED FOLIATION AND DIRECTION OF PLUNGE OF LINEATION*--Used where plunge is not indicated in source of geologic mapping STRIKE AND DIP OF INCLINED FOLIATION AND HORIZONTAL LINEATION STRIKE AND DIP OF BEDS AND INTERSECTING FOLIATION*--Symbols joined at point of observation STRIKE AND DIP OF BEDS AND INTERSECTING FOLIATION OF EQUAL STRIKE AND OPPOSING DIP SOURCES OF BEDROCK GEOLOGIC MAPPING [Sources of mapping in the east half of the Blythe 30' by 60' quadrangle are marked by an asterisk (*). Sources of mapping without an asterisk are in the west half of the quadrangle.] 1. Ballard, 1990 (Little Maria Mountains, California) 2.* Crowl, 1979; this study (central Dome Rock Mountains, Arizona) 3. Hamilton, 1964, 1984; Hamilton, Warren, unpublished (Big Maria Mountains, California) 4.* Knapp, 1989 (Mesquite Mountain and Moon Mountain areas, Arizona) 5.* Knapp, 1989; Spencer and others, 1988; this study (Copper Peak area, Arizona) 6.* Miller, 1970; Lerch, M.F., unpublished; Richard, S.M., unpublished; this study (southern Plomosa Mountains, Arizona) 7. Powell, R.E., unpublished (Little Chuckwalla Mountains, California) 8*. Scarborough and Meader, 1983, 1989 (northern Plomosa Mountains, Arizona) 9. Stone and Pelka, 1989 (McCoy Mountains, California) 10.* Stoneman, 1985a, 1985b; this study (central Plomosa Mountains, Arizona) 11.* Tosdal, 1988; this study (southern Dome Rock Mountains, Arizona) 12.* Tosdal, R.M., unpublished; this study (Mule Mountains, California) 13.* Yeats, 1985a, 1985b; this study (northern Dome Rock Mountains, Arizona) 14.* This study (small areas in the Little Maria Mountains, California and in the Dome Rock and Plomosa Mountains, Arizona) Notes: Surficial deposits were mapped primarily by the author through air photo interpretation and local field study. Outcrops of the fine-grained sedimentary rocks unit of the Bouse Formation (Tbs) are from Metzger and others (1973) and A.V. Buising (unpublished mapping). REFERENCES CITED [IN USGS OPEN-FILE REPORT 90-497] Ballard, S.N., 1990, The Mesozoic structural evolution of the Little Maria Mountains, Riverside County, California: Santa Barbara, Calif., University of California, Ph.D. dissertation, 380 p. Crowl, W.J., 1979, Geology of the central Dome Rock Mountains, Yuma County, Arizona: Tucson, Ariz., University of Arizona, M.S. thesis, 76 p. Dalrymple, G.B., 1979, Critical tables for conversion of K-Ar ages from old to new constants: Geology, v. 7, p. 558-560. Eberly, L.D., and Stanley, T.B., Jr., 1978, Cenozoic stratigraphy and geologic history of southwestern Arizona: Geological Society of America Bulletin, v. 89, p. 921-940. Hamilton, Warren, 1964, Geologic map of the Big Maria Mountains NE quadrangle, Riverside County, California and Yuma County, Arizona: U.S. Geological Survey Geologic Quadrangle Map GQ-350, scale 1:24,000. Hamilton, Warren, 1982, Structural evolution of the Big Maria Mountains, northeastern Riverside County, southeastern California, in Frost, E.G., and Martin, D.L., eds., Mesozoic-Cenozoic tectonic evolution of the Colorado River region, California, Arizona, and Nevada: San Diego, California, Cordilleran Publishers, p. 1ö27. Hamilton, Warren, 1984, Generalized geologic map of the Big Maria Mountains region, northeastern Riverside County, southeastern California: U.S. Geological Survey Open-File Report 84-407, scale 1:48,000. Hamilton, Warren, 1987, Mesozoic geology and tectonics of the Big Maria Mountains region, southeastern California, in Dickinson, W.R., and Klute, M.A., eds., Mesozoic rocks of southern Arizona and adjacent areas: Arizona Geological Society Digest 18, p. 33ö48. Harding, L.E., 1980, Petrology and tectonic setting of the Livingston Hills Formation, Yuma County, Arizona, in Jenney, J.P., and Stone, Claudia, eds., Studies in western Arizona: Arizona Geological Society Digest 12, p. 135-145. Harding, L.E., 1982, Tectonic significance of the McCoy Mountains Formation, southeastern California and southwestern Arizona: Tucson, Ariz., University of Arizona, Ph.D. thesis, 197 p. Harding, L.E., and Coney, P.J., 1985, The geology of the McCoy Mountains Formation, southeastern California and southwestern Arizona: Geological Society of America Bulletin, v. 96, p. 755ö769. Hutton, D.H.W., 1979, Tectonic slides: A review and reappraisal: Earth Science Reviews, v. 15, p. 151-172. Knapp, J.K., 1989, Structural development, thermal evolution, and tectonic significance of a Cordilleran basement thrust terrane, Maria fold and thrust belt, west-central Arizona: Cambridge, Mass., Massachusetts Institute of Technology, Ph.D. thesis, 262 p. Martin, D.L., Krummenacher, Daniel, and Frost, E.G., 1982, K-Ar geochronologic record of Mesozoic and Tertiary tectonics of the Big Maria-Little Maria- Riverside Mountains terrane, in Frost, E.G., and Martin, D.L., eds., Mesozoic- Cenozoic tectonic evolution of the Colorado River region, California, Arizona, and Nevada: San Diego, California, Cordilleran Publishers, p. 519ö557. Metzger, D.G., Loeltz, O.J., and Irelan, Burdge, 1973, Geohydrology of the Parker-Blythe-Cibola area, Arizona and California: U.S. Geological Survey Professional Paper 486-G, 130 p. Miller, F.K., 1970, Geologic map of the Quartzsite quadrangle, Yuma County, Arizona: U.S. Geological Survey Geologic Quadrangle Map GQ-841, scale 1:62,500. Miller, F.K., and McKee, E.H., 1971, Thrust and strike-slip faulting in the Plomosa Mountains, southwestern Arizona: Geological Society of America Bulletin, v. 82, p. 717-722. Pelka, G.J., 1973, Geology of the McCoy and Palen Mountains, southeastern California: Santa Barbara, Calif., University of California, Ph.D. thesis, 162 p. Reynolds, S.J., Spencer, J.E., Asmerom, Yemane, DeWitt, Ed, and Laubach, S.E., 1989, Early Mesozoic uplift in west-central Arizona and southeastern California: Geology, v. 17, p. 207-211. Scarborough, Robert, and Meader, Norman, 1983, Reconnaissance geology of the northern Plomosa Mountains: Arizona Geological Survey Open-file Report 83-24, 35 p. Scarborough, Robert, and Meader, Norman, 1989, Geologic map of northern Plomosa Mountains, Yuma County, Arizona: Arizona Geological Survey Contributed Map CM- 89-D, scale 1:24,000. Shafiqullah, M., Damon, P.E., Lynch, D.J., Reynolds, S.J., Rehrig, W.A., and Raymond, R.H., 1980, K-Ar geochronology and geologic history of southwestern Arizona and adjacent areas, in Jenney, J.P., and Stone, Claudia, eds., Studies in western Arizona: Arizona Geological Society Digest 12, p. 201-260. Spencer, J.E., Duncan, J.T., and Burton, W.D., 1988, The Copperstone Mine: Arizona's new gold producer: Arizona Geological Survey Fieldnotes, v. 18, no. 2, p. 1-3. Stone, Paul, Howard, K.A., and Hamilton, Warren, 1983, Correlation of metamorphosed Paleozoic strata of the southeastern Mojave Desert region, California and Arizona: Geological Society of America Bulletin, v. 94, p. 1135ö 1147. Stone, Paul, and Pelka, G.J., 1989, Geologic map of the Palen-McCoy Wilderness Study Area and vicinity, Riverside County, California: U.S. Geological Survey Miscellaneous Field Studies Map MF-2092, scale 1:62,500. Stoneman, D.A., 1985a, Structural geology of the Plomosa Pass area, northern Plomosa Mountains, La Paz County, Arizona: Tucson, Ariz., University of Arizona, M.S. thesis, 99 p. Stoneman, D.A., 1985b, Geologic map of the Plomosa Pass area, northern Plomosa Mountains, La Paz County, Arizona: Arizona Geological Survey Miscellaneous Map MM-85b, scale 1:12,000. Tosdal, R.M., 1988, Mesozoic rock units along the Late Cretaceous Mule Mountains thrust system, southeastern California and southwestern Arizona: Santa Barbara, Calif., University of California, Ph.D. thesis, 365 p. Tosdal, R.M., Haxel, G.B, and Wright, J.E., 1989, Jurassic geology of the Sonoran Desert region, southern Arizona, southeastern California, and northernmost Sonora: Construction of a continental-margin magmatic arc, in Jenney, J.P., and Reynolds, S.J., eds., Geologic evolution of Arizona: Arizona Geological Society Digest 17, p. 397ö434. Yeats, K.J., 1985a, Geology and structure of the northern Dome Rock Mountains, La Paz County, Arizona: Tucson, Ariz., University of Arizona, M.S. thesis, 123 p. Yeats, K.J., 1985b, Geologic map and structure section of the northern Dome Rock Mountains, La Paz County, Arizona: Arizona Geological Survey Miscellaneous Map MM-85-C, scale 1:12,000.