1
80 85 50 85 75 75 45 30 85 85 65 75 80 15 20 25 25 80 50 65 45 80 60 65 85 85 85 75 45 50 45 40 15 80 50 65 75 70 80 80 60 45 85 80 80 75 35 Kt Qyf Kri J^m Qa Kgd Kri Qf Kcgw Qyf Kcg Kri Kgd Jmg Qyf Kgb Kt Qfls Kat Jmg Kt Qls Qfls Kqd Jmg Qya J^m Kcgw Kgd Qfls J^m Kgd Kt Kgd Kcg Qls Kgd Kgd Kri Qyc Kgd Qvoc Jmg Kgd Qls Qof Qls Kgd Qyf Qya Qyc Qof Qvoc Kgd Qls Kt Qfls Qvof Qvoc Jmg Qya Qoc Kt Qfls Kgd Qvof Kgd Qof Qfls Qoc Kgd J^m Qoc Qls Kgd Qls Qoc Qc Kgd J^m J^m Qa Kat Qya Qoc Qls Qvof Kgd Qfls Qyc Qls Qc Qvof J^m Qyc Qls Kqd Qvof Qvof Qls Qls Kgd Kgd Qls Kri Kgb Kri J^m Qyc Qfls Kri Qa Qa Qls Qls Kgd Qa Kri Qyf Kqd Kgd Qyf Qyf Qyf Qof Qof Qof Kgd ELSINORE FAULT ZONE J^m J^m J^m Qfls Kgd Kgb Kri Kri Kri Kgd Kgd Qc Qoc Qc Qoc Jmg Jmg Jmg Qof Qya Qoa Qvoa Qls Qls Qls Qls Qls Qls Qls Kat Qa Qls Qls J^m J^m J^m Qls Qls Qls Qoc Kt Qoc Jmg Kt Qls Qfls Qfls Qfls Qfls Qfls Qfls J^m Qls Kt Kt Kgd Qf GN 240 MILS 13 0 02 1MIL MN UTM GRID AND 1988 MAGNETIC NORTH DECLINATION AT CENTER OF SHEET 1/ 2 Contour Interval 40 Feet SCALE 1:24 000 8000 FEET 3000 4000 5000 .5 2 KILOMETERS 0 1 1/ 2 0 1 2 MILES 0 1000 2000 6000 7000 Bull, W.R., 1991, Geomorphic responses to climatic change: New York, Oxford University Press, 326 p. Gastil, G., Girty, G., Wardlaw, M., and Davis, T., 1988, Correlation of Triassic-Jurassic sandstone in peninsular California (abs.): Geological Society of America Abstracts with Programs, v. 20, no. 3, p. 162. Germinario, M. P., 1982, The depositional and tectonic environments of the Julian Schist, Julian, California: Unpublished M.S. thesis, San Diego State University, San Diego, California, 95 p. Hanley, J.B., 1951, Economic Geology of the Rincon Pegmatites, San Diego County, California: California Division of Mines, Special Report 7-B, 24 p., scale 1:24,000. Hanley, J.B., Irwin, W.P., and Ellis, M.W., 1948, Geologic map of the Rincon District, San Diego County, California, in Hanley, J.B., 1951, Economic geology of the Rincon pegmatites, San Diego County, California: California Division of Mines Special. Report. 7-B, 24p., scale 1:24,000. Hanley, J.B., Irwin, W.P., Jahns, R.H., and Ellis, M.W., 1950, Unpublished geological mapping of the Pala and Rincon pegmatite districts, San Diego County, California: U.S. Geological Survey unpublished maps, scale 1:24,000. Hart, M.W., 1991, Landslides in the Peninsular Ranges, Southern California, in Walawender, M.J. and Hanan, B.B., editors, Geological excursions in Southern California and Mexico: Geological Society of America Annual Meeting guidebook p. 349-365. Hudson, F.S., 1922, Geology of the Cuyamaca region of California, with special reference to the origin of nickeliferous pyrrhotite: University of California Department of Geological Sciences Bulletin, v. 13, p. 175-252. Irwin, W.P. and Greene, R.C., 1970, Studies related to wilderness primitive areas, Agua Tibia, California: U.S. Geological Survey Bulletin 1319-A, 19 p., scale 1:48,000. Kennedy, M.P., 2000, Geologic map of the Pechanga 7.5' quadrangle, San Diego County, California: California Geological Survey Preliminary Geologic Map website, http://www.conservation.ca.gov/cgs/rghm/rgm/preliminary_geologic_maps.htm Kennedy, M.P., 2003, Geologic map of the Vail Lake 7.5' quadrangle, San Diego and Riverside counties, California: California Geological Survey Preliminary Geologic Map website, http://www.conservation.ca.gov/cgs/rghm/rgm/preliminary_geologic_maps.htm Kennedy, M.P., 2006, Geologic map of the Valley Center 7.5' quadrangle, San Diego County, California: California Geological Survey Preliminary Geologic Map website, http://www.conservation.ca.gov/cgs/rghm/rgm/preliminary_geologic_maps.htm Larsen, E. S., Jr., 1948, Batholith and associated rocks of Corona, Elsinore and San Luis Rey quadrangles, southern California: Geological Society of America Memoir 29, 182 p., plate 1, scale 1:125,000. Matti, J. C., Cossette, P.M., and Hirschberg, D.M., 2010, Classification of surficial materials, Inland Empire Region, southern California: Conceptual and operational framework: U.S. Geological Survey Scientific Investigations Report, in press. Olmstead, F.H., 1953, Geologic map of Pauma Indian Reservation and vicinity, San Diego County, California: Unpublished geologic map, U.S. Geological Survey, Ground Water Branch, Sacramento, California, scale 1:24,000. Olmstead, F.H., 1955, Geologic map of La Jolla Indian Reservation, San Diego County, California: Unpublished geologic map, U.S. Geological Survey, Ground Water Branch, Sacramento, California, scale 1:24,000. Shaw, S.E., Todd, V.R., and Grove, M., 2003, Jurassic peraluminous gneissic granites in the axial zone of the Peninsular Ranges, southern California, in Johnson, S.E., Paterson, S.R., Fletcher, J.M., Girty, G.H., Kimbrough, D.L., and Martin-Barajas, A., editors, Tectonic evolution of northwestern Mexico and southwestern USA: Boulder, Colorado, Geological Society of America Special Paper 374, p. 157-183. Streckenisen, A.L., 1973, Plutonic rocks - classification and nomenclature recommended by the IUGA Subcommission on Systematics of Igneous Rocks: Geotimes, v. 18, p. 26-30. Tan, S. S. and Kennedy, M. P., 2003, Geologic map of the Aguanga 7.5' quadrangle, San Diego and Riverside counties, California: California Geological Survey Preliminary Geologic Map website, http://www.conservation.ca.gov/cgs/rghm/rgm/preliminary_geologic_maps.htm Todd, V.R., 2013 (in press), Geologic map of the Julian 7.5’ quadrangle, San Diego County, California: U.S. Geological Survey Open-File Report 94-16, scale 1:24,000. Todd, V.R., 1979, Geologic map of the Mount Laguna quadrangle, San Diego County, California: U.S. Geological Survey Open-File Report 79-862, 48 p., scale 1:24,000. Todd, V.R., Shaw, S.E., and Hammarstrom, J.M., 2003, Cretaceous plutons of the Peninsular Ranges batholith, San Diego and westernmost Imperial Counties, California: Intrusion across a Late Jurassic continental margin, in Johnson, S.E., Paterson, S.R., Fletcher, J.M., Girty, G.H., Kimbrough, D.L., and Martin-Barajas, A., editors, Tectonic evolution of northwestern Mexico and southwestern USA: Boulder, Colorado, Geological Society of America Special Paper 374, p. 185-235. Weber, F. H., 1963, Geology and mineral resources of San Diego County, California: California Division of Mines and Geology County Report 3, 309 p., scale 1:126,720. REFERENCES CITED steep mountain fronts north east of the EFZ as a result of regional uplift and gravity. Where they coalesce, the younger landslide deposits interfinger with the alluvial fan deposits at mid slope and are mapped as alluvial fan and landslide deposits undivided (Qfls). Numerous bedrock landslides (Qls) occur on steep slopes throughout the area. One large composite bedrock landslide occurs at Tin Can Flat, between Harrison Canyon and Pauma Creek, in the south facing slopes of Pauma Valley. The upper part of the landslide is underlain by the EFZ. Based on field observations and close scrutiny of satellite imagery and stereo photographs it is inconclusive as to whether the landslide debris is faulted. The Tin Can Flat landslide was first mapped as breccia associated with the Elsinore Fault Zone by Hanley (1951) and as landslide debris by Weber (1963) and later described in detail and given the name “Tin Can Flat Landslide” by Hart (1991). The classification of the Quaternary sedimentary deposits is modified from the U.S. Geological Survey, Classification of surficial materials, Inland Empire Region, southern California: Conceptual and operational framework, described by Matti and others (2010). Inherent to this classification is the fact that the surficial deposits have been deposited continuously, albeit at different rates, throughout the Quaternary Period and each of the four basic lithostratigaphic units mapped (alluvial fan, alluvial valley fill, colluvial slope and landslide deposits) represent often interfingered time transgressive facies. The parameters used in this modified classification include: 1) physical properties and lithologic features, e.g. consolidation, induration, fabric, grain size, sorting, etc., 2) genesis and geomorphic setting, e.g. alluvial fan, alluvial valley fill, colluvial slope deposits, etc., and 3) age determinations, e.g. radiometric analyses, paleontology, pedogenic soil characteristics, desert varnish, vegetation, degree of incision, etc. Surficial Quaternary units (excluding landslide deposits) includes: 1). “Modern surficial deposits” which are those being deposited actively or intermittently active over the past few hundred years. Their soil development is slight to non-existent. They are labeled Qf, Qa, and Qc (alluvial fan, alluvial valley fill and colluvial slope deposits). 2). “Young surficial deposits” which are those that were deposited during the Holocene and latest Pleistocene or since the Holocene-to-Pleistocene climatic transition (Bull, 1991). They are slightly dissected, have slight soil development, and little if any pavement or varnish. They are labeled Qyf, Qya and Qyc (alluvial fan, alluvial valley fill and colluvial slope deposits). 3). “Old surficial deposits” which are those that were deposited during the middle to late Pleistocene and spanning the period of approximately 500ka to about 15ka. They have moderately dissected surfaces, good soil development, minor clay films, and moderate varnish and pavement. They are labeled Qof, Qoa and Qoc (alluvial fan, alluvial valley fill and colluvial slope deposits). 4). “Very old surficial deposits” which are those that were deposited during the early to middle Pleistocene or approximately 1Ma to 500ka. They have well dissected surfaces, strong soil development, thick clay films and well developed varnish and pavement. They are labeled Qvof, Qvoa and Qvoc (alluvial fan, alluvial valley fill and colluvial slope deposits). The Boucher Hill 7.5’ quadrangle is located in the northwestern quadrant of the Borrego Valley 1:100,000-scale quadrangle (Fig. 2). Geological mapping was conducted during the period July 2005 - June 2006 by the Department of Conservation’s, California Geological Survey pursuant to U.S. Geological Survey STATEMAP cooperative mapping award No. 05HQAG0080. The geologic map of the Boucher Hill quadrangle is a product of the Southern California Areal Mapping Project (SCAMP), a cooperative U.S. Geological Survey-California Geological Survey regional geologic mapping project. Detailed 1:24,000-scale geologic mapping of the Boucher Hill Quadrangle was undertaken primarily to study the Elsinore Fault Zone (EFZ) in the rapidly uplifting region of the Agua Tibia-Palomar Mountain Block (Fig. 3). This includes depicting the principal and most active trace of the EFZ in an effort to better define areas that have potential for future surface rupture. Additional purposes for the mapping include: 1) delineating and describing the Quaternary surficial units of the region and in particularly those that might fail or otherwise behave poorly during earthquake shaking, 2) studying the tectonically active processes that are shaping the region adjacent to and within the EFZ in the Agua Tibia-Palomar Mountain block, and 3) producing a geologic framework that will prove useful to future investigations dealing with regional tectonics, paleo and real time seismology, ground response, mineral deposits and groundwater. The map and explanation can be viewed and downloaded at : http://www.consrv.ca.gov/CGS/rghm/rgm/Pages/southern_region_quads.aspx Previous geological mapping of basement rocks (Hanley, Irwin and Ellis, 1948; Hanley, and others, 1950; Irwin and Greene, 1970; Olmstead, 1953, 1955) has been useful in this study and used with modifications (Fig. 4). The landslides on the south side of the San Luis Rey River were mapped by D.M. Morton, U.S. Geological Survey during this investigation. In addition, STATEMAP sponsored mapping within the Borrego Valley 1:100,000-scale quadrangle (Fig. 2), has been completed within the EFZ and Agua Tibia-Palomar Mountain region in the Vail Lake (Kennedy, 2003), and Aguanga 7.5’ quadrangles (Tan and Kennedy, 2003). The Elsinore Fault zone, a major element of the San Andreas Fault System, divides the Boucher Hill quadrangle into a northeastern mountainous highland and a southwestern fan and landslide foreland. The area northeast of the EFZ is underlain by the Agua Tibia-Palomar Mountain block with elevations of more than 5000 feet (1500 meters) at Boucher Hill and Palomar Mountain. Youthful uplift is evidenced by the steep and deeply dissected Quaternary alluvial fan and landslide deposits that mantle the base of the slopes. The area southeast of the fault is more gentle and rolling and is dissected by the northwest flowing San Luis Rey River. Thoroughly dissected Quaternary alluvial fan and landslide deposits, originating from uplifted and over steepened slopes, are draped across the EFZ along most of its trace as well as over large low lying areas in Pauma Valley and Rincon. These surficial deposits make it difficult to determine the exact location of the fault across most of the quadrangle. The fans are extensive and extend from high on the very steep slopes, southwest to the San Luis Rey River where they are truncated and locally exposed in river bank cuts. In the vicinity of Potrero Creek the fans extend from over 3000 feet (900 meters) elev. to less than 800 feet (240 meters) elevation over a distance of 2.5 miles (4 kilometers). The Boucher Hill quadrangle is underlain by Triassic-Jurassic metasedimentary rocks intruded by two distinctly different plutonic rock suites. The older Jurassic age suite is composed of extensively fractured and well-foliated metagranitic rock. A younger Cretaceous plutonic suite consists of massive to crudely foliated granitic rock. This Mesozoic basement complex is overlain in many places by modern, young, old and very old surficial Quaternary alluvial flood plain, alluvial fan, colluvial and landslide deposits. TRIASSIC-JURASSIC METASEDIMENTARY ROCKS: The metasedimentary rocks (JTrm) consist mostly of quartzofeldspathic schist, pelitic schist, quartzite, and metabreccia. These rocks have been informally correlated with the Julian Schist by earlier workers (Hanley, 1951; Olmstead, 1955; Irwin and Greene, 1970). The protolith of the Julian Schist, based on relic depositional structures including graded bedding and Bouma sequences, appears to be a submarine fan sequence (Germinario, 1982). The age of the Julian Schist is considered to be Triassic based on a fossil ammonite (Hudson, 1922). Gastil and others (1988) report a detrital zircon Triassic-Jurassic depositional age for the protolith. The Julian Schist can be no younger than the Middle Jurassic plutonic rocks that intrude it (Shaw and others, 2003). JURASSIC METAGRANITIC ROCKS: The Jurassic metagranitic rocks (Jmg) are gneissic and composed mostly of dark-gray, coarse- to medium-grained, foliated, biotite tonalite with lesser amounts of biotite granodiorite. The unit has intruded and assimilated “Julian Schist” and is characterized by elongated remnant inclusions of it. These inclusions range in size from an inch or so (a few centimeters) to more than 30 feet (10 meters) and have their long axis in the foliation plane. These rocks are correlated with the Granodiorite of Harper Creek mapped in the Julian area by Todd (1994). They are described in detail and assigned a Middle Jurassic (U-Pb) age of 170-160 Ma by Shaw and others (2003). CRETACEOUS GRANITIC ROCKS: The Cretaceous granitic rocks are mostly tonalite and granodiorite but range in composition from gabbro to monzogranite (Streckenisen, 1973 and Fig. 4). They include the “tonalite of Rincon”, (Kri), the “tonalite of Cole Grade”, (Kcg), the “gabbro of the Agua Tibia Mountains”, (Kat), granodiorite undivided, (Kgd), tonalite undivided, (Kt), gabbro undivided, (Kgb) and quartz diorite undivided, (Kqd). Undivided means that the rocks within each of the four units is petrologically that rock type (e.g. granodiorite), but not necessarily genetically associated or part of the same pluton. The “tonalite of Rincon” (Kri) and the “tonalite of Cole Grade” (Kcg) are petrologically similar and consist mostly of light- to medium-gray, medium- to coarse-grained hornblende-biotite tonalite. The “tonalite of Rincon” (Kri) an informal name given in this report for the excellent exposures of it near Rincon on the north side of the San Luis Rey River. The “tonalite of Cole Grade” (Kcg), and where very deeply weathered (Kcgw), was given its informal name for the excellent exposures of it, south of the San Luis River, along Cole Grade Road in the adjacent Valley Center quadrangle (Kennedy, 2006). Although these two tonalites are lithologically similar they are different in that the “tonalite of Rincon” is pervasively intruded by granitic pegmatite dikes. These pegmatites are mineralogically simple, and contain only quartz, perthite, and plagioclase as essential minerals, and muscovite as a subordinate mineral. A few pegmatites contain schorl, beryl, and garnet as accessory minerals and lithia pegmatites are scarce (Hanley, 1951). Some of the pegmatite has been mined for beryl and quartz crystals. Detailed mapping of the pegmatites and a report of their occurrence was completed in 1948 by U.S. Geological Survey geologists J. Hanley, T. Ellis and W. Irwin as reported in Hanley (1951). Kcg is commonly very deeply weathered and labeled Kcgw. The “gabbro of the Agua Tibia Mountains” (Kat) is an informal name given to a massive gabbroic pluton that underlies much of the Agua Tibia Mountains to the north in the Pechanga quadrangle (Kennedy, 2000) and crops out near the northwestern corner of the quadrangle. It is mostly medium- to coarse-grained, massive- to crudely-foliated hornblende gabbro that is locally quartz bearing. Granodiorite (Kg) crops out in the north-northwestern corner and south-southeastern corner or the quadrangle and though mostly granodiorite it is partly tonalite. It is mostly white to pale brownish-gray, coarse-grained, leucocratic, hornblende-biotite granodiorite. Many of these rocks are lithologically similar to the Woodson Mountain Granodiorite of Larsen, (1948). Tonalite (Kt) crops out north of and adjacent to the EFZ in the eastern and northeastern part of the quadrangle. These rocks underlie a large part of the Palomar Mountain block and are typically massive, medium- to coarse-grained, light-gray, hornblende-biotite tonalite and in lesser amounts granodiorite and monzogranite. Because they are mostly tonalite they are labeled Kt. In large part these rocks are lithologically similar to and tentatively correlated with rocks 30 miles (50 km) to the southeast within the Julian quadrangle where they were described in detail, assigned a zircon U-Pb isotopic age of 90 – 100 Ma and given the informal name “tonalite of Granite Mountain” (Todd, 1979; 1994). Like the Jurassic plutons, they intrude Julian Schist and are locally characterized by remnant inclusions of it. Quartz diorite (Kqd) crops out in Pauma Valley where it is extensively intruded by pegmatite dikes and consists mostly of massive, coarse-grained, dark-gray, quartz diorite with lesser amounts of tonalite and gabbro. The tonalite is petrologically similar to the “tonalite of Rincon”. Gabbro (Kgb) crops out along the southeaster border of the quadrangle and is mostly massive, coarse-grained, dark-gray and black, biotite-hornblende-hypersthene gabbro with lesser amount of quartz diorite and tonalite. SURFICIAL QUATERNARY SEDIMENTARY DEPOSITS: Quaternary sedimentary deposits of the area include alluvial fan, alluvial valley fill, colluvial slope and landslide. The alluvial fan deposits are those deposited in fans along the mountain fronts. The alluvial flood plain deposits are those deposited in flood plains in the valley floors. The colluvial deposits were derived from proximal slopes and highlands during periods of heavy precipitation and laid down at the base of the slopes and in adjacent low lying hollows. The landslide deposits are mostly formed on the GEOLOGIC SUMMARY 117° 00' 00" 33° 22' 30" 116° 52' 30" 33° 22' 30" 116° 52' 30" 117° 00' 00" 33° 15' 00" 33° 15' 00" A. Hanley, J.B., Irwin, W.P. and Ellis, M.W., 1948, Geologic map of the Rincon District, San Diego County, California, in Hanley, J.B., 1951, Economic geology of the Rincon pegmatites, San Diego County, California: California Division of Mines Special Report. 7-B, 24 p., scale 1:24,000. This mapping was used with very minor modification. B. Hanley, J.B., Irwin. W.P., Jahns, R.H. and Ellis, M.W., 1950, Unpublished geological mapping of the Pala and Rincon pegmatite districts, San Diego County, California: U.S. Geological Survey unpublished maps, scale 1,24,000. This mapping was used with very minor modification for the bedrock geology in area B. C. Irwin, W.P. and Greene, R.C., 1970, Studies related to wilderness primitive areas, Agua Tibia, California: U.S. Geological Survey Bulletin 1319-A, 19 p., scale 1:48,000. This mapping was used with very minor modification. D. Kennedy, M.P., 2006, revised 2011, this map. E. Olmstead, F.H., 1953, Geologic map of Pauma Indian Reservation and vicinity, San Diego County, California: U.S. Geological Survey, Ground Water Branch, Sacramento, California, unpublished geologic map, scale 1:24,000. This mapping was modified. F. Olmstead, F.H., 1955, Geologic map of La Jolla Indian Reservation, San Diego County, California: U.S. Geological Survey, Ground Water Branch, Sacramento, California, unpublished geologic map, scale 1:24,000. This mapping was used with very minor modification. ABD BD CD CED BDF D D ABDF ED CBD Figure 4 - Index map showing sources of geological mapping. Figure 3 - Map showing the location of the Boucher Hill, Vail Lake, Aguanga and Palomar Observatory 7.5' quadrangles with respect to the Elsinore and San Jacinto Fault Zones and the Agua Tibia-Palomar Mountain Block. The Boucher Hill quadrangle (this report) was complete July 2006 under U.S. Geological Survey STATEMAP cooperative mapping award #05HQAG0080. The Vail Lake and Aguanga quadrangles were completed in 2003 under award # 02HQAG0018. The Palomar Observatory quadrangle is being considered as a future mapping project by the California Geological Survey. San Jacinto Fault Zone Elsinore Fault Zone Hot Springs Agua Caliente Fault Fault EXPLANATION Fault -- dashed where inferred 33° 30' 33° 15' 33° 30' 33° 15' 117° 00' 116° 15' 116° 15' 117° 00' Vail Lake 7.5' quadrangle Lake Henshaw Agua Palomar Mt. Block Tibia- Aguanga 7.5' quadrangle Boucher Hill 7.5' quadrangle Palomar Obs. 7.5' quadrangle Borrego Valley 1:100,000-scale Quadrangle N Miles 0 10 20 30 Aguanga Beauty Mt. Bucksnort Mt. Collins Valley Clark Lake Rabbit Pk. Oasis Boucher Hill Palomar Observatory Borrego Springs Hot Springs Mt. Borrego Palm Canyon Clark Lake Fonts Point Seventeen Palms Rodriquez Mt. Mesa Grande Warners Ranch Ranchita Tubb Canyon Borrego Sink Borrego Mt. Shell Reef Ramona Santa Ysabel Julian Earthquake Valley Whale Peak Harper Canyon Borrego Mt. S.E. Vail Lake Figure 2 - Index map showing the location of the Boucher Hill and other 7.5' quadrangles in the Borrego Valley 1:100,000-scale quadrangle. Mapping completed under STATEMAP FY 2005-06 FY 2006-07 CGS OFR 96-06 & CD 2000-008 FY 2002-03 San Pasqual Quartz Syenite Quartz Monzonite Quartz Monzodiorite Syenite Monzonite Monzodiorite Granite Alkali-feldspar Granite Tonalite Diorite Syenogranite Granodiorite Monzogranite Quartz Diorite 90 65 35 10 5 20 60 Q Q A P 60 20 5 60 Figure 1 - Classification of plutonic rock types (from IUGS, 1973, and *Streckeisen, 1973). A, alkali feldspar; P, plagioclase feldspar; Q, quartz. *Streckeisen, A.L., 1973, Plutonic rocks--Classification and nomenclature recommended by the IUGS Subcommission on Systematics of Igneous Rocks: Geotimes, vol.18, pp. 26-30. Holocene QUATERNARY CRETACEOUS JURASSIC TRIASSIC CENOZOIC MESOZOIC Pleistocene Qf Qa Qc Qyf Qya Qyc Qof Qoa Qoc Qvof Qvoa Qvoc Qfls Qls Kri Kcg Kcgw Kat Kgd Kt Kqd Kgb Jmg J^m CORRELATION OF MAP UNITS 55 Qls ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ Contact - Contact between geologic units; dashed where approximately located; dotted where concealed. Fault - Dashed where approximately located; dotted where concealed; arrows indicate relative direction of movement. Zone of intense shearing along the Elsinore Fault Zone. Where trace of fault is concealed, shearing is inferred. Landslide - Arrow(s) indicates principal direction of movement. Strike and dip of foliation in metamorphic rock: Inclined Vertical Pegmatite dike MAP SYMBOLS MODERN SURFICIAL DEPOSITS Sediment that has been recently transported and deposited in channel and washes, on surfaces of alluvial fans and alluvial plains, and on hill slopes and in artificial fills. Soil-profile development is non-existant. Includes: Alluvial fan deposits (late Holocene) - Active and recently active alluvial fans. Consists of unconsolidated, bouldery, cobbley, gravelly, sandy, or silty alluvial fan deposits, and headward channel parts of alluvial fans. Trunk drainages and proximal parts of fans contain greater percentage of coarse-grained sediment than distal parts. Alluvial flood plain deposits (late Holocene) - Active and recently active alluvial deposits along canyon floors. Consists of unconsolidated sandy, silty, or clay-bearing alluvium. Does not include alluvial fan deposits at distal ends of channels. Colluvium (late Holocene) - Active and recently active slope wash deposits along base of slopes. Consists of unconsolidated, sandy, silty, or clay-bearing colluvium. YOUNG SURFICIAL DEPOSITS Sedimentary units that are slightly consolidated to cemented and slightly to moderately dissected. Alluvial fan deposits typically have high coarse-fine clast ratios. Young surficial units have upper surfaces that are capped by slight to moderately developed pedogenic-soil profiles. Includes: Young alluvial fan deposits (Holocene and late Pleistocene) - Mostly poorly consolidated and poorly sorted sand, gravel, cobble and boulder alluvial fan deposits. Young alluvial flood plain deposits (Holocene and late Pleistocene) - Mostly poorly consolidated, poorly sorted, permeable flood plain deposits. Young colluvial deposits (Holocene and late Pleistocene) - Mostly poorly consolidated sandy, silty or clay-bearing slope wash deposits. OLD SURFICIAL DEPOSITS Sediments that are moderately consolidated and slightly to moderately dissected. Older surficial deposits have upper surfaces that are capped by moderate to well-developed pedogenic soils. Includes: Old alluvial fan deposits (late to middle Pleistocene) - Reddish-brown, sand, gravel, cobble and boulder alluvial fan deposits that are usually indurated and slightly dissected. Old alluvial flood plain deposits, undivided (late to middle Pleistocene) - Fluvial sediments deposited on canyon floors. Consists of moderately well-consolidated, poorly sorted, permeable, commonly slightly dissected gravel, sand, silt, and clay-bearing alluvium. Old colluvial deposits (late to middle Pleistocene) - Mostly consolidated sand- and silt-bearing slopewash deposits that are slightly dissected. VERY OLD SURFICIAL UNITS Sediments that are slightly to well-consolidated to indurated, and moderately to well-dissected, Upper surfaces are capped by moderate to well-developed pedogenic soils. Includes: Very old alluvial fan deposits (middle to early Pleistocene) - Mostly well-dissected, well-indurated, reddish-brown sand and gravel alluvial fan deposits. Very old alluvial flood plain deposits, undivided (middle to early Pleistocene) - Fluvial sediments deposited on canyon floors. Consists of moderately to well-indurated, reddish-brown, mostly very dissected gravel, sand, silt, and clay-bearing alluvium. Very old colluvial deposits (middle to early Pleistocene) - Reddish-brown, consolidated, sand and gravel deposits that formed as slopewash aprons over deeply weathered older rock. Alluvial fan and landslide deposits, undivided (Holocene to Pleistocene) - Over-steepened alluvial fan deposits that have undergone post depositional downslope movement as rock avalanches, debris flows, slumps and rock falls. Landslide deposits (Holocene to Pleistocene) - Highly fragmented to largely coherent landslide deposits. Unconsolidated to consolidated. Most mapped landslides contain scarp area as well as landslide deposit. PLUTONIC ROCKS (See Figure 1 for classification) Tonalite of Rincon (Cretaceous) - Mostly medium- to coarse-grained, hornblende-biotite tonalite extensively intruded by pegmatite dikes. Tonalite of Cole Grade (Cretaceous) - Mostly medium- to coarse-grained, hornblende- biotite tonalite. Tonalite of Cole Grade (weathered) (Cretaceous) - Mostly deeply weathered medium- to coarse-grained, hornblende-biotite tonalite. Gabbro of the Agua Tibia Mountains (Cretaceous) - Mostly hornblende gabbro; medium- to coarse-grained, massive- to crudely-foliated hornblende gabbro, locally quartz-bearing. Granodiorite (Cretaceous) - Mostly medium- to coarse-grained, hornblende- biotite granodiorite with lesser amounts of tonalite. Tonalite (Cretaceous) - Mostly massive, medium- to coarse-grained, light-gray, hornblende-biotite tonalite with lesser amounts of granodiorite and monzogranite. Quartz diorite (Cretaceous) - Mostly massive, coarse-grained, dark-gray, quartz diorite. Contains gabbro and tonalite. Gabbro (Cretaceous) - Mostly massive, coarse-grained, dark-gray and black, biotite-hornblende-hypersthene gabbro. Contains quartz diorite and tonalite. METAGRANITIC PLUTONIC ROCKS Metagranitic rocks (Jurassic) - Mostly dark-gray, coarse- to medium-grained, foliated, biotite tonalite with lesser amounts of biotite granite. METASEDIMENTARY ROCKS Metasedimentary rocks (Jurassic and Triassic) - Mostly quartzofeldspathic schist, pelitic schist, quartzite, and metabreccia. DESCRIPTION OF MAP UNITS Qf Qa Qc Qyf Qya Qyc Qof Qoa Qoc Qvof Qvoa Qvoc Qfls Qls Kri Kcg Kcgw Kat Kgd Kt Kqd Kgb Jmg J^m CGS S G S A M P S U C Prepared in cooperation with the U.S. Geological Survey, Southern California Areal Mapping Project 116°52'30" 33°22'30" 117°00'00" 33°22'30" 117°00'00" 33°15'00" 116°52'30" 33°15'00" Copyright © 2014 by the California Department of Conservation California Geological Survey. All rights reserved. No part of this publication may be reproduced without written consent of the California Geological Survey. "The Department of Conservation makes no warranties as to the suitability of this product for any given purpose." PRELIMINARY GEOLOGIC MAP OF THE BOUCHER HILL 7.5' QUADRANGLE, SAN DIEGO COUNTY, CALIFORNIA: A DIGITAL DATABASE Version 1.2 By MICHAEL P. KENNEDY 1 2006 (Revised 2014) Digital Preparation by Carlos I. Gutierrez 2 1. California Geological Survey, 888 South Figueroa Street, Suite 475, Los Angeles, CA 90017 2. California Geological Survey, 801 K Street, MS 12-32, Sacramento, CA 95814 Topographic base from U.S. Geological Survey Boucher Hill 7.5-minute Quadrangle, 1988 UTM projection, North American Datum 1927 This geologic map was funded in part by the U.S. Geological Survey National Cooperative Geologic Mapping Program, STATEMAP Award no. 05HQAG0080 Preliminary Geologic Map available from: http://www.conservation.ca.gov/cgs/rghm/rgm/preliminary_geologic_maps.htm STATE OF CALIFORNIA – EDMUND G. BROWN JR., GOVERNOR THE NATURAL RESOURCES AGENCY – JOHN LAIRD, SECRETARY FOR NATURAL RESOURCES DEPARTMENT OF CONSERVATION – MARK NECHODOM, CONSERVATION DIRECTOR CALIFORNIA GEOLOGICAL SURVEY JOHN G. PARRISH, Ph.D., STATE GEOLOGIST PRELIMINARY GEOLOGIC MAP OF THE BOUCHER HILL 7.5’ QUADRANGLE, CALIFORNIA
