Prepared in cooperation with the GEOLOGICAL SURVEY

U.S. DEPARTMENT OF THE INTERIOR OPEN-FILE REPORT 03-189 U.S. GEOLOGICAL SURVEY

o DESCRIPTION OF MAP UNITS 117 o 15' 117 07' 30" CORRELATION OF MAP UNITS 33o 37' 30" 33 o 37' 30"

YOUNG SURFICIAL DEPOSITS—Sedimentary units that are slightly Kpvg Monzogranite to granodiorite-Pale gray, massive, medium-grained consolidated to cemented and slightly to moderately dissected. Alluvial fan hypidiomorphic-granular biotite monzogranite, and less abundant deposits (Qyf series) typically have high coarse:fine clast ratios. Younger hornblende-biotite granodiorite forming older ring dike. Plagioclase is surficial units have upper surfaces that are capped by slight to moderately An20 to An35, subhedral, tabular crystals. Contains included small to developed pedogenic-soil profiles (A/C to A/AC/BcambricCox profiles). large stoped blocks of gabbro Holocene Qya Qyf Qyv Qyls Includes: Kpvt Tonalite-Foliated biotite-hornblende tonalite. In eastern part of complex Qyf Young alluvial fan deposits (Holocene and latest Pleistocene)- grades into tonalite Qoa QUATERNARY Unconsolidated deposits of alluvial fans and headward drainages of Pleistocene fans. Consists predominately of gravel, sand, and silt Generic Cretaceous granitic rocks of the batholith Qpfs Qpff Qvoa Qya Young alluvial channel deposits (Holocene and latest Pleistocene)- Fluvial deposits along canyon floors. Consists of unconsolidated sand, Kgd Granodiorite, undifferentiated (Cretaceous)-Biotite and hornblende- QTsw QTcw CENOZOIC Pliocene silt, and clay-bearing alluvium biotite granodiorite, undifferentiated. Most is massive and medium- Qyv Young alluvial valley deposits (Holocene and late Pleistocene)-Fluvial grained. Restricted to small exposure along east edge of quadrangle Tvsr Tvt deposits along valley floors. Consists of unconsolidated sand, silt, and Kt Tonalite, undifferentiated (Cretaceous)-Gray, medium-grained biotite- Miocene TERTIARY clay-bearing alluvium hornblende tonalite, typically foliated. Restricted to single area Tvh Qyls Young landslide (Holocene and latest Pleistocene)-Highly fragmented flanking Tucalota Creek along east edge of quadrangle to largely coherent landslide deposits. Unconsolidated to consolidated. Kgb Gabbro (Cretaceous)-Mainly hornblende gabbro. Includes Virginia Most mapped landslides contain scarp area as well as slide deposit. quartz-norite and gabbro of Dudley (1935), and San Marcos gabbro of Kpvgr Kpvp Kpvg Kpvt Kt Generic Many landslides in part reactivated during late Holocene Larsen (1948). Typically brown-weathering, medium-to very coarse- Cretaceous Kgd OLD SURFICIAL DEPOSITS—Sedimentary units that are moderately grained hornblende gabbro; very large poikilitic hornblende crystals are rocks of CRETACEOUS the Peninsular consolidated and slightly to moderately dissected. Older surficial deposits common, and very locally gabbro is pegmatitic. Much is quite Kgb MESOZOIC Ranges have upper surfaces that are capped by moderately to well-developed heterogeneous in composition and texture. Includes noritic and dioritic batholith Khg pedogenic soils (A/AB/B/Cox profiles and Bt horizons as much as 1 to 2 m composition rocks. Abundant stoped blocks of gabbro are included in thick and maximum hues in the range of 10YR 5/4 and 6/4 through 7.5YR the Paloma ring complex }u 6/4 to 4/4 and mature Bt horizons reaching 5YR 5/6). Includes: Khg Heterogeneous granitic rocks (Cretaceous)-A wide variety of Qoa Old alluvial channel deposits (late to middle Pleistocene)-Fluvial heterogeneous granitic rocks. Rocks in , 5 km sediments deposited on canyon floors. Consists of moderately northwest of Murrieta, include a mixture of monzogranite, granodiorite, indurated, commonly slightly dissected gravel, sand, silt, and clay- tonalite, and gabbro. Tonalite composition rock is most abundant rock bearing alluvium. Locally capped by thin, discontinuous alluvial type deposits of Holocene age }u Metasedimentary rocks, undifferentiated (Mesozoic)-Wide variety of On some SCAMP geologic map plots, including the Murrieta 7.5' quadrangle, VERY OLD SURFICIAL DEPOSITS—Sediments that are slightly to low-to medium-metamorphic grade metasedimentary rocks. Within the characteristic grain size information is displayed using subscripted alpha well consolidated to indurated, and moderately to well dissected. Upper Santa Ana Mountains rocks are of low grade, greenschist or lower characters (e.g. Qyfg, Qova), where the characters conform to the following surfaces are capped by moderate to well developed pedogenic soils grade. Most of the eastern occurrences include biotite schist definitions: (A/AB/B/Cox profiles having Bt horizons as much as 2 to 3 m thick and maximum hues in the range 7.5YR 6/4 and 4/4 to 2.5YR 5/6) GEOLOGIC SUMMARY a - arenaceous (very coarse sand through very fine sand) Qvoa Very old alluvial channel deposits (middle to early Pleistocene)-Fluvial b - boulder gravel (>25mm) sediments deposited on canyon floors. Consists of moderately to well- The Murrieta quadrangle is located in the northern part of the g - gravel (cobble through granule gravel) indurated, reddish-brown, mostly very dissected gravel, sand, silt, and Peninsular Ranges Province and includes parts of two structural blocks, s - silty clay-bearing alluvium. In places, includes thin, discontinuous alluvial or structural subdivisions of the province. The quadrangle is diagonally c - clayey deposits of Holocene age crossed by the active Elsinore zone, a major fault zone of the San Pauba Formation (Pleistocene)-Siltstone, sandstone, and conglomerate. Andreas fault system, and separates the Santa Ana Mountains block to Named by Mann (1955) for exposures of in Rancho Pauba area about the west from the Perris block to the east. Both blocks are relatively 3.2 km southeast of Temecula. Vertebrate fauna from Pauba Formation stable internally and within the quadrangle are characterized by the are of late Irvingtonian and early Rancholabrean ages (Reynolds and presence of widespread erosional surfaces of low relief. Reynolds, 1990a; 1990b). Includes two informal members: The Santa Ana Mountains block, in the Murrieta quadrangle, is underlain by undifferentiated, thick-layered, granular, impure quartzite In the Description of Map Units, the Ma following U/Pb ages has an attached Qpfs Sandstone member-Brown, moderately well-indurated, cross-bedded sandstone containing sparse cobble- to boulder-conglomerate beds and well-layered, fissile, phyllitic metamorphic rock of low subscript; Maid for isotope dilution analyses, and Maip for ion probe analyses. Qpff Fanglomerate member-Grayish-brown, well indurated, poorly sorted metamorphic grade. Both quartzite and phyllitic rocks are Mesozoic. fanglomerate and mudstone; occurs along the east flank of the Santa Unconformably overlying the metamorphic rocks are remnants of Ana Mountains basalt flows having relatively unmodified flow surfaces. The age of the Sandstone and conglomerate of Wildomar area (Pleistocene and late basalt is about 7-8Ma. Large shallow depressions on the surface of the Pliocene)-Unnamed sandstone and conglomerate unit unconformably larger basalt remnants form vernal ponds that contain an endemic flora. overlain by the Pauba Formation (Kennedy, 1977). Lower part yields Beneath the basalt the upper part of the metamorphic rocks is deeply vertebrate fauna of late Blancan age, 2 to 3 Ma; upper part yields fauna weathered. The weathering appears to be the same as the regional of Irvingtonian age, less than 0.85 Ma (Reynolds and Reynolds, 1990a, Paleocene saprolitic weathering in . West of the 1990b; Reynolds and others, 1990). At Chaney Hill in Murrieta area, quadrangle a variable thickness sedimentary rock, physically Contact—Generally located within ±15 meters unit contains 0.7 Ma Bishop ash (Merriam and Bischoff, 1975). resembling Paleogene rocks, occurs between the basalt and 70 Estimated maximum thickness is 75 m. Subdivided into sandstone unit metamorphic rock. Where not protected by the basalt, the weathered Fault—High angle. Strike-slip component on all faults is right-lateral; dip-slip and conglomerate unit: rock has been removed by erosion. component is unknown, but probably reflects valley-highland relations. Solid QTsw Sandstone unit-Primarily friable, pale yellowish-green, medium grained, The dominant feature on the Perris block in the Murrieta where located within ±15 meters; dashed where located within ±30 meters; caliche-rich sandstone quadrangle is the south half of the Paloma Valley ring complex, part of dotted where concealed. Arrow and number indicate measured dip of fault QTcw Conglomerate unit-Primarily cobble-and-boulder conglomerate. the composite Peninsular Ranges batholith. The complex is elliptical in plane. Conglomerate clasts are locally derived plan and consists of an older ring-dike with two subsidiary short-arced 70 Tvsr Santa Rosa basalt of Mann (1955) (Miocene)-Remnants of basalt flows dikes that were emplaced into gabbro by magmatic stoping. Small to Kpvp—Pegmatite dikes of Paloma Valley Complex. Arrow and number indicate having relatively unmodified flow surfaces. See Hawkins (1970) for large stoped blocks of gabbro are common within the ring-dikes. A measured dip of dike. detailed petrologic description of basalt. Originally described by younger ring-set of hundreds of thin pegmatite dikes occur largely Strike and dip of beds Fairbanks (1892) and informally named by Mann (1955) for basalt within the central part of the complex. These pegmatite dikes were flows in vicinity of Rancho Santa Rosa, west of Temecula. Name also emplaced into a domal fracture system, apparently produced by 70 Inclined has been applied to basalts in general area of Temecula and Santa Ana cauldron subsidence, and include in the center of the complex, a Strike and dip of igneous foliation Mountains, but here is restricted to rocks in area west of Temecula. number of flat-floored granophyre bodies. The granophyre is Southwestern part of Santa Rosa basalt of Mann (1955) extruded on interpreted to be the result of pressure quenching of pegmatite magma. 70 Inclined deeply weathered surface of low relief similar to Paleocene age Along the eastern edge of the quadrangle is the western part of a large surfaces found elsewhere in southern California. Morton and Morton septum of medium metamorphic grade Mesozoic schist. A dissected Vertical (1979) report whole-rock conventional potassium-argon ages for Santa basalt flow caps the Hogbacks northeast of Temecula, and represents Rosa basalt of Mann (1955) 6.7 and 7.4 Ma. Slightly older age of 8.7 remnants of a channel filling flow. Beneath the basalt is a thin deposit Strike and dip of metamorphic foliation Ma was obtained by Hawkins (1970) of stream gravel. Having an age of about 10Ma, this basalt is about 2- 70 Tvt Basalt of Temecula area (Miocene)-Basalt; restricted to single exposure 3 3Ma older than the basalt flows in the Santa Ana Mountains. Inclined km northwest of Murrieta in quadrangle. Outside quadrangle, includes The forms a complex of pull-apart basins. The scattered exposures of basalt north and east of Temecula, and a small west edge of the fault zone, the Willard Fault, is marked by the high, Strike and dip of joints in sedimentary rocks exposure of vesicular basalt within valley area of Elsinore Fault zone steep eastern face of the Santa Ana Mountains. The east side of the Vertical near Wildomar (Mann, 1955; Kennedy, 1977; Hull, 1990). East of zone, the Wildomar Fault, forms a less pronounced physiographic step. Temecula, rocks assigned to this unit include exposures of vesicular In the center of the quadrangle a major splay of the fault zone, the basalt and what appears to be a dissected cinder cone and scattered Murrieta Hot Springs Fault, strikes east. Branching of the fault zone volcanic bombs (Mann, 1955) causes the development of a broad alluvial valley between the Willard Tvh Basalt of Hogbacks (Miocene)-Basalt capping Hogbacks 5 km northeast of Fault and the Murrieta Hot Springs Fault. All but the axial part of the Murrieta. Remnant of channel-filling basalt flow. Thin deposit of zone between the Willard and Wildomar Faults consist of dissected unconsolidated gray stream gravel underlies axial part of channel- Pleistocene sedimentary units. The axial part of the zone is underlain filling basalt. Basalt is less vesicular than most of Santa Rosa basalt of by Holocene and latest Pleistocene sedimentary units. Mann (1955) (Tvsr) and tends to break into slabby fragments. Whole- rock conventional potassium-argon ages are 10.4 and 10.8 Ma (Morton REFERENCES and Morton, 1979) Dudley, P.H., 1935, Geology of a portion of the Perris block, southern Rocks of the Peninsular Ranges batholith California: California Journal Mines and Geology, v. 31, p. 487-506. Fairbanks, H.W., 1892, Geology of San Diego County; also of portions of Paloma Valley Ring Complex (Cretaceous)-Composite ring dike Orange and San Bernardino Counties, in, Yale, G.Y., ed., Eleventh intrusion. Named and described by Morton and Baird (1976) for report of the State Mineralogist: California State Mining Bureau exposures south of Paloma Valley area. Included within Woodson Eleventh Report, p. 76-120. Mountain granodiorite and San Marcos gabbro by Larsen (1948). Ring Hawkins, J.W., 1970, Petrology and possible tectonic significance of Late complex consists of older, elliptical in plan, single ring-dike and two Cenozic volcanic rocks, southern California and Baja California: subsidiary short-arced dikes. Younger ring-set of thin dikes is largely Geological Society of America Bull., v. 81, no. 11, p. 3323-3338. Elsinore Romoland Winchester within older ring dike. Older dike consists of granodiorite and Hull, A.G., 1990, Seismotectonics of the Elsinore-Temecula trough, monzogranite with vertical walls emplaced into gabbro by ring Elsinore fault zone, southern California: Ph.D. dissertation, Santa fracturing and magmatic stoping of gabbro. Younger ring-dike consists Barbara, California, University of California, 233p. Murrieta of hundreds of granitic pegmatite dikes. Most pegmatite dikes range Kennedy, M.P., 1977, Recency and character of faulting along the Elsinore from 30 cm to over 1 m in thickness, and define a domal ring-dike fault zone in southern Riverside County, California: California Div. Wildomar 7.5' Bachelor Mtn. geometry in which outer dikes are moderately to steeply outward Mines and Geology, Special Report 131, 12 p. dipping and pass progressively inward to near horizontal dikes in Larsen, E.S., 1948, Batholith and associated rocks of Corona, Elsinore, and center. Spatially associated with younger dikes in center of complex, San Luis Rey quadrangles, southern California: Geol. Society America are bodies of granophyre that contain stringers of granitic pegmatite. Mem. 29, 182 p. Younger dikes are interpreted as products of volatile-rich magma that Mann, J.F., 1955, Geology of a portion of the Elsinore fault zone, Pechanga Fallbrook Temecula filled a domal set of fractures resulting from cauldron subsidence. California: California Div. Mines Special Report 43, 22 p. Granophyre is interpreted as product of pressure quenching of Merriam, Richard, and Bischoff, J.L, 1975, Bishop Ash: A widespread pegmatite magma and attendant loss of volatiles. Zircon ages of rock volcanic ash extended to southern California: Jour. Sedimentary SURROUNDING 7.5' QUADRANGLES from atypical hornblende-bearing granodiorite from western part of Petrology, v. 45, p. 207-211. 40 39 older dike is 121 Maid and 118.5 Maip. Ar/ Ar age of hornblende Morton, D.M. and Baird, A.K, 1976, Petrology of the Paloma Valley ring 117.7 Ma and biotite 118.8 Ma. Includes: complex, southern California batholith: U.S. Geol. Survey Jour. Kpvgr Granophyre-Pale gray, very fine grained, porphyritic, granophyre. Research, v. 4, n. 1, p 83-89. Forms numerous, small, irregular shaped flat-floored bodies intruding Morton, J.L. and Morton, D.M., 1979, K-Ar ages of Cenozoic volcanic gabbro (Kgb) in central part of complex. Phenocrysts of altered rocks along the Elsinore Fault zone, southwestern Riverside California: plagioclase are in groundmass of granophyric intergrowths of quartz, Geol. Soc. America, Abstracts with programs, v. 11, p. 119. potassium feldspar, and sodic plagioclase. Pyrite is ubiquitous Reynolds, R.E., Fay, L.P., and Reynolds, R.L., 1990, An early-late accessory mineral, and where oxidized, discolors outcrops reddish- Irvingtonian land mammal age fauna from Murrieta, Riverside County, brown. Network of pegmatitic-textured stringers averaging 2.5 cm California: San Bernardino County Museum Association Quarterly, v. thick cuts much of granophyre. Stringers are compositionally and XXXVII, p. 35-36. texturally zoned, with fine-grained margins and coarse-grained interiors Reynolds, R.E., and Reynolds, R.L., 1990a, A new late Blancan faunal Kpvp Pegmatite dikes of Paloma Valley Ring Complex-Linear to arcuate, assemblage from Murrieta, Riverside County, California: San Q Q 60 60 leucocratic pegmatite dikes typically 30 cm to 1 m thick. Very Bernardino County Museum Association Quarterly, v. XXXVII, p. 34. concentrated in central part of complex. Most are texturally and ______, 1990b, Irvingtonian? Faunas from the Pauba Formation, compositionally zoned. Outer zones are coarse-grained granite Temecula, Riverside County, California: San Bernardino County composed of quartz, perthite, and sodic plagioclase, and may or may Museum Association Quarterly, v. XXXVII, p. 37. ranite Granodiorite Tonalite not contain biotite and minor magnetite. Inner zone consists of Rogers, T.H., 1965, Santa Ana sheet: California Division of Mines and Granite nite pegmatitic-textured perthite, sodic plagioclase, quartz, biotite, and (or) Geology Geologic Map of California, scale, 1:250,000.

zogra muscovite, and accessory magnetite, schorl, garnet, and epidote. Streckeisen, A.L., 1973, Plutonic rocks—Classification and nomenclature i-feldspar G

Syenogranite Quartz crystal-lined vugs found locally. Graphic intergrowths of quartz recommended by the IUGA Subcommission on Systematics of Igneous Mon Alkal o and perthite are common in rock transitional between coarse-grained Rocks: Geotimes, vol. 18, p. 26-30. 33 o 30' 33 30' 20 20 Quartz granite and pegmatitic textured granite. Dikes that lack pegmatitic o o Diorite 117 15' 117 07' 30" Quartz Quartz Quartz cores consist entirely of coarse- to extremely coarse-grained granitoid Syenite Monzonite Monzodiorite Base from U.S. Geological Survey textured rock, with or without graphic intergrowths Geology mapped by M.P. Kennedy, 1975-76; 5 5 Murrieta 7.5' quadrangle, 1979 and D.M. Morton, 1967-68, 93 Syenite Monzonite Monzodiorite Diorite Polyconic projection GN A P MN SCALE 1:24,000 90 65 35 10 14.5 o 1 Classification of plutonic rock types (from IUGA, 1973, and Streckeisen, 1973). 1 2 0 1 MILE A, alkali feldspar; P, plagioclase feldspar; Q, quartz. 6a 90 37 1 3 94 63 Sample locality, showing 1 .5 0 1 KILOMETER 96 C H 94 sample numbers and 6 I 100 5 potassium-argon ages. 101 1a N 4 103 7 O Riverside 13 82 CONTOUR INTERVAL 20 FEET 102 95 Approximate location of F A boundary separating W H 12 92 I T U 108 plutons having well L 100 T I 8 88 E R T 2 11 developed penetrative 18 81 F 93 22 29 fabrics on the east, from A U 87 20 21 L T 73 30 essentially structureless 19 86 86 Z O Corona S N 17 90 A 87 79 plutons on the west. E N 71 PRELIMINARY GEOLOGIC MAP OF THE MURRIETA 7.5' QUADRANGLE, RIVERSIDE COUNTY, CALIFORNIA 9 104 96 J 24 25 86 28 10 A 88 108 16 C 23 Palm Springs 102 I 95 N 88 31 68 T 27 32 45 O 26 71 15 86 83 78 108 102 85 Version 1.0 LOCATION MAP Perris 35 46 73 36 92 60 14 88 This report is preliminary and has not been reviewed for conformity E 33 86 84 110 74 L 109 48 44 34 38 Indio 73 S 96 37 with U.S. Geological Survey editorial standards or with the North I 72 61 116 N 104 90 O 87 San Jacinto 64 63 Lake R 43 By American Stratigraphic Code. Any use of trade, firm, or product names in Elsinore E 50 47 39 96 F this publication is for descriptive purposes only and does not imply 72 109 91 A 41 66 109 51 49 U 84 endorsement by the U.S. Government. 106 90 L 52 91 T 42 39a 11 102 1 2 This map was printed on an electronic plotter directly from digital files. 4 106 94 85 Block 67 70 Perris 84 M.P. Kennedy and D.M. Morton Dimensional calibration may vary between electronic plotters and 71 Murrieta 7.5' 101 53 90 56 between X and Y directions on the same plotter, and paper may change 108 100 40 quadrangle 100 85 80 116 54 57 size due to atmospheric conditions; therefore, scale and proportions may 67 84 not be true on plots of this map. 103 98 92 68 102 Block Digital files available on World Wide Web at http://geopubs.wr.usgs.gov 115 108 98 69 58 86 Digital preparation by 55 81 88 104 Z Santa Ana O Santa Rosa Mts F N 66 A 59 E 95 U mylonite zone 2 3 L 90 Rachel M. Alvarez and Greg Morton T N Block Z O 60 96 N E 89 65 104 1 2 3 0 5 10 15 20KM California Geological Survey U.S. Geological Survey Department of Earth Sciences 61 64 63 98 655 South Hope St. Department of Earth Sciences University of California 107 106 Los Angeles , CA 90017 University of California Riverside, CA 92521 62 Location of Murrieta quadrangle relative to major structural blocks of the northern Peninsular Ranges 105 batholith. Conventional potassium-argon biotite ages of Cretaceous granitic rocks are hand contoured, and Riverside, CA 92521 are considered to reflect the cooling history of the batholith rather than representing ages of emplacement. Contouring of ages in each of the three structural blocks separated by the Elsinore and San Jacinto fault zones, was done independently of ages in adjacent blocks. Red band shows offset of 98 to 108 contours across Elsinore fault zone. Faults as shown are simplified from Rogers, 1965.