The Pacoima area consists of Miocene (sediments and basalts) rocks underlain by a quartz diorite basement complex of Jurassic age. The stratigranhic units range from 25 feet to more than 600 feet in thickness. The lower sediments are arkosic land- laid deposits while the Modelo formation, shallow marine in origin, consists of thinly bedded sandstones, shales, volcanic ash and calcareous members. An andesitic mass, possibly a volcanic plug, outcrops near the summit of one of the hills.
\r\n\r\nAn anticline, and possibly an associated syncline, has been developed by compressional folding. Small scale contortion is locally exposed. Regional dip is northward, decreasing from south to north in the area. Faulting is common, most faults trending nearly north-south. Movement along these faults ranges from a few feet to several hundred feet.
\r\n\r\nThere are no important mineral deposits in the area. Quarrying of the basement rocks has been abandoned.
\r\n" }, { "name": "Allingham, John Wing", "degree": "Senior Thesis", "year": "1948", "title": "Geology of the Pacoima Area, Los Angeles County, California", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:07022015-134459990", "creators": [ { "name": { "family": "Allingham", "given": "John Wing" }, "id": "Allingham-John-Wing", "display_name": "Allingham, John Wing" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/P2R8-0R25", "abstract": "The Pacoima area is located on an isolated hill in the northeast section of the San Fernando, the northeast portion of the Pacoima Quadrangle, Los Angeles County, California. Within it are exposed more than 2300 feet of Tertiary rocks, which comprise three units of Middle Miocene (?) age, and approximately 950 feet of Jurassic (?) granite basement. The formations are characterized by their mode of occurrence, marine and terrestial origin, diverse lithology, and structural features.
\r\n\r\nThe basement complex is composed of intrusive granite, small masses of granodiorite and a granodiorite gneiss with the development of schistosity in sections. During the long period of erosion of the metamorphics, the granitic rocks were exposed and may have provided clastic constituents for the overlying formations.
\r\n\r\nAs a result of rapid sedimentation in a transitional environment, the Middle Miocene Twin Peaks formation was laid down unconformably on the granite. This formation is essentially a large thinning bed of gray to buff pebble and cobble conglomerate grading to coarse yellow sandstone. The contact of conglomerate and granite is characterized by its faulted and depositional nature.
\r\n\r\nBeds of extrusive andesite, basalt porphyry, compact vesicular amygdaloidal basalts, andesite breccia, interbedded feldspathic sands and clays of terrestial origin, and mudflow breccia comprise the Pacoima formation which overlies the Twin Peaks formation unconformably. A transgressing shallow sea accompanied settling of the region and initiated deposition of fine clastic sediments.
\r\n\r\nThe marine Topanga (?) formation is composed of brown to gray coarse sandstone grading into interbedded buff sandstones and gray shales. Intrusions of rhyolitedacite and ash beds mark continued but sporatic volcanism during this period.
\r\n\r\nThe area mapped represents an arch in the Tertiary sediments. Forces that produced the uplift of the granite structural high created stresses that were relieved by jointing and faulting. Vertical and horizontal movement along these faults has displaced beds, offset contacts and complicated their structure. Uplift and erosion have exposed the present sequence of beds which dip gently to the northeast. The isolated hill is believed to be in an early stage of maturity.
\r\n" }, { "name": "Shoemaker, Eugene Merle", "degree": "Senior Thesis", "year": "1947", "title": "A Geologic Report on the Pacoima Area", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:07072015-115042010", "creators": [ { "name": { "family": "Shoemaker", "given": "Eugene Merle" }, "id": "Shoemaker-Eugene-Merle", "display_name": "Shoemaker, Eugene Merle" }, { "name": { "family": "Glover", "given": "Patrick Norman" }, "id": "Glover-Patrick-Norman", "display_name": "Glover, Patrick Norman" }, { "name": { "family": "Muehlberger", "given": "William R." }, "id": "Muehlberger-William-R", "display_name": "Muehlberger, William R." }, { "name": { "family": "Nicolai", "given": "Fred H." }, "id": "Nicolai-Fred-H", "display_name": "Nicolai, Fred H." } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/NG1S-EQ56", "abstract": "The region treated in the following report is a small area of about one square mile near Pacoima, California. It consists of a group of small hills that that form the western abutment of the Hansen Dam. It is underlain by a section of intrusives, sediments, and extrusives, which may be subdivided into four groups.
\r\n\r\nThe oldest rocks form the Dimebere complex of Jurassic (?) plutonic rocks, pegmatites, and schists. Lying uncomformably on this is a series of alternating terrestrial sandstones and bassalts of Tertiary age. These are unconformably overlain in turn by the Hansen Dam formation, a series of marine shales and sandstone correlated with the Temblor by the fossil contact. Finally into these strata was intruded the Munglish andesite.
\r\n\r\nThese strata form a shallow, plunging anticline, whose axis trends slightly east of north and lies in the center of the hills. The unconformities have been offset in several places by a series of faults apparently related to the anticline.
\r\n\r\nA complete outline of the geologic history is included in the report.
\r\n" }, { "name": "Shoemaker, Eugene Merle", "degree": "Senior Thesis", "year": "1947", "title": "Geomorphology of a Portion of the Easternmost Ventura Basin", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechTHESIS:07072015-094601408", "creators": [ { "name": { "family": "Shoemaker", "given": "Eugene Merle" }, "id": "Shoemaker-Eugene-Merle", "display_name": "Shoemaker, Eugene Merle" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "option_major": [ "geol" ], "doi": "10.7907/WEN7-KY40", "abstract": "The Humphreys Quadrangle is a portion of the easternmost Ventura Basin underlain by a thick series of Tertiary sedimentary rocks. On these rocks a great variety of geomorphic forms have been molded by the processes of running water typical of a semi-arid climate and by several types of mass movement. Among the different categories of mass movement present, a new type, the siltflow, was observed.
\r\nThe geomorphic forms of special interest present in the quadrangle are rock cones, open canyonheads, asymmetric canyons, and stream terraces and straths. The author urges the adoption of the definition of strath as that part of an old dissected valley floor, including the floors of tributary valleys, which was not part of the floodplain of the main valley stream.
\r\nAn old erosion surface, the Puckett Mesa Surface, is present in the Humphreys Quadrangle which is correlative with certain of the older stream terraces. By correlating the variation of gradient and of fill of the stream terraces with post \u2013Wisconsin climatic fluctuations the age of the Puckett Mesa Surface is set at approximately 6000 B.C. This correlation sets the probable age of the older Rancho La Brea deposits at 6000 to 8000 B. C. and the probable age of the Carpenteria brea deposits at 1000 to 1 B. C.
\r\n" }, { "name": "George, John (Jack) Wesley", "degree": "Senior Thesis", "year": "1937", "title": "Geologic Report on a Portion of the Little Tujunga Quadrangle and a Portion of the Sunland Quadrangle", "advisor": "Bode, Francis D.", "url": "https://resolver.caltech.edu/CaltechTHESIS:12102009-092225763", "creators": [ { "name": { "family": "George", "given": "John (Jack) Wesley" }, "id": "George-John-Jack-Wesley", "display_name": "George, John (Jack) Wesley" } ], "advisors": [ { "name": { "family": "Bode", "given": "Francis D." }, "id": "Bode-F-D", "role": "advisor", "display_name": "Bode, Francis D." } ], "committee": [ { "name": { "family": "None", "given": "None" }, "display_name": "None, None" } ], "option_major": [ "geol" ], "doi": "10.7907/PW3T-1E97", "abstract": "The area under investigation is in the north-west portion of Sunland Quadrangle and the south-west portion of the Little Tujunga Quadrangle, Los Angeles County, California. The maps used were the advance sheets of\r\nthese two quadrangles surveyed in 1933 by the United States Geological Survey with a scale of 1:24,000 and a contour interval of twenty-five feet.
\r\n\r\nThe area is reached by traveling westward along Foothill Boulevard from Pasadena through the town of Sunland and continuing along the boulevard approximately six miles past Sunland and then turning right on the road pointing to Kagel Canyon.
\r\n\r\nSpecifically, the area is bounded on the south by the alluvium of Tujunga Valley, on the west by Lopez Canyon, on the east by Herrick Canyon, and on the north by the so called Sierra Madre Fault which give the fault contact between the Saugus sediments and the basement complex. The area is about three miles long (North-South) and two and one-half miles wide (East-West) giving a total area of approximately seven and one-half square miles.
\r\n\r\nThe field work was done on occasional Saturdays and Sundays during the school year of 1936-1937. The purpose of the work is to gain a more thorough knowledge of geological field mapping and of the structural interpretation of field work results.
\r\n\r\nThe work was done largely under the supervision of Dr. Francis Bode. His suggestions were very helpful. Mr. Richard Hopper's help was very valuable. Mr. Walter White, who covered the same area as partial fulfillment of his thesis for a Master's degree in geology offered many suggestions. For reference, the paper, \"Structure of the San Gabriel Mountains North of Los Angeles, California\", by Mason L. Hill found in the University of California Publications in Geological Sciences, Volume 19, 1929-1931 was used as well as U.S.G.S. Bulletin 753 by William S.W. Kew.
\r\n" }, { "name": "Lockwood, Robert Bruce", "degree": "Senior Thesis", "year": "1937", "title": "Geology of the Central Portion of the Sunland Quadrangle, California", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechETD:etd-09272002-133724", "creators": [ { "name": { "family": "Lockwood", "given": "Robert Bruce" }, "id": "Lockwood-Robert-Bruce", "display_name": "Lockwood, Robert Bruce" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "None", "given": "None" }, "display_name": "None, None" } ], "option_major": [ "geol" ], "doi": "10.7907/Y6KV-R629", "abstract": "The region in which the geology was mapped includes an area in the central portion of the Sunland Quadrangle, just west of the small town of Sunland and about 20 mi. north west of Los Angles. The sedimentary series here consists of interbedded conglomerates, sandstones, and siliceous shales, lower Modelo in age, which rest depositionally on old granites and gneisses. Above the lower Modelo there is a thin section of typical, highly contorted upper Modelo shales, which seem to rest with slight unconformity of the lower Modelo. Above this, and resting depositionally with about a 10\u00b0 unconformity, there is a section of about 550 feet of Pico (lower Pliocene), which consists of a series of lava conglomerates, white punky shales, and sandstones.
\r\n\r\nThese beds have been faulted in numerous places. The two main faults trend in an approximate N 70\u00b0 W direction, while the minor faults are oriented in various other directions. There has also been some folding, especially in the area to the west, which seems to be a direct result of the faulting.
" }, { "name": "Schombel, Leonard Frederick", "degree": "Senior Thesis", "year": "1937", "title": "Geology of Area Near Sunland, California", "advisor": "Unknown, Unknown", "url": "https://resolver.caltech.edu/CaltechETD:etd-09272002-134525", "creators": [ { "name": { "family": "Schombel", "given": "Leonard Frederick" }, "id": "Schombel-Leonard-Frederick", "display_name": "Schombel, Leonard Frederick" } ], "advisors": [ { "name": { "family": "Unknown", "given": "Unknown" }, "display_name": "Unknown, Unknown" } ], "committee": [ { "name": { "family": "None", "given": "None" }, "display_name": "None, None" } ], "option_major": [ "geol" ], "doi": "10.7907/JS82-JM16", "abstract": "I. Introduction.
\r\n\r\nAn area of approximately four square miles lying 20 miles northwest of Pasadena California was mapped to satisfy the senior thesis requirement in geology at the California Institute of Technology. The area mapped lies around the mouth of Big Tujunga Canyon which in turn is 2 miles east of Sunland, Calif.
II. Physical Conditions.
\r\n\r\nA series of sediments and volcanics was mapped which lie at the base of the western slope of the San Gabriel Mts. between elevations of 1400' and 2300'. The relief on the whole is rugged and of the early mature stage. The area is divided into two zones by Big Tujunga Canyon. Drainage in the northern zone is at right angles to the trend of the mountains, the streams running north and south and emptying into Big Tujunga River, Exposures in the western part of this zone are excellent, the streams having eroded steep walled canyons across the strike of the sediments. The exposures grow progressively fewer to the east, more of the country being covered by alluvium and brush. The zone lying south of Big Tujunga Canyon runs north and south. Approximately the northern 1/3 of this zone drains northward into Big Tujunga Canyon. The remainder drains westward into Tujunga Valley. Exposures in this zone are few, most of the surface being covered by recent alluvium and heavy brush.
III. Field Methods.
\r\n\r\nMapping was done on the La Crescenta and Sunland quadrangles of the Los Angeles County topographic sheets, scale 1:24,000. The Brunton Compass was the only instrument used. Locations were determined by re-section and are accurate to 100'. Dips and strikes are accurate to 5 degrees.