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Offshore Geology: Offshore Geology: Continental Borderland and Continental Borderland and PaleoPaleo--TrenchTrench

Mark R. LeggLegg Geophysical, Inc.

Workshop on Establishing a Geologic Framework in Southern CaliforniaKellogg West Conference Center, Pomona, CA -- 8-9 June 2016

A brief overview of what I have learned about the offshore geology with a whole lot of help from my friends

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Translations and Vertical-Axis RotationsExtension and Contraction

The California Continental BorderlandThe California Continental Borderlandis an is an ““Organized Train WreckOrganized Train Wreck””

Charlie Hollister, 1998Charlie Hollister, 1998

Organized train wreck involves block rotation, collisions, telescoping, buckling – but one can reconstruct/repair the train. Challenge is to reconstruct the Borderland and its deformation history

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Baja California

Baja California

North AmericaNorth America

PacificPacific

GUADGUAD

WTRWTRSSAFSSAF

California Continental BorderlandCalifornia Continental Borderland

Borderland

Borderland

LALA

International Space Station Imagery

View from the International Space Station looking north across the Pacific-North America plate boundary in southern California and Baja California. Collision of the Baja California microplate against the San Andreas bend and Western Transverse Ranges is responsible for the modern complex seismotectonic environment of the region.

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Major Tectonic Major Tectonic ElementsElements

Two LargeTwo Large Oblique Rifts Oblique Rifts Separated by the Separated by the

Peninsular RangesPeninsular Ranges

•• Inner Borderland Rift Inner Borderland Rift in the in the AccretionaryAccretionaryWedgeWedge

•• Gulf of California Rift Gulf of California Rift in the in the BackarcBackarc BasinBasin

• Rifts Terminate at Transverse Ranges Forearc Terrane

• Outer Borderland Forearc and Subduction Complex

Overview map of the major tectonic elements of the Pacific-North America transform plate boundary – Two major oblique rifts, Gulf of California rifted in the former back-arc region; Inner Continental Borderland rifted in the former fore-arc region of the Farallon-North America subduction zone.

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Borderland Physiography and the Peninsular RangesBorderland Physiography and the Peninsular Ranges

Patton

Escarpment

PattonNicolas

Catalina

Western Transverse Ranges

Santa Ana

Map showing the major late Cenozoic basins of the Borderland and the lithotectonicbelts (tectono-stratigraphic terranes) of the southern California region. Basins are color coded by inferred tectonic style (focus on Inner Borderland Rift). Three Miocene craters (inferred calderas) are shown in the metamorphic core complex –Catalina Island may be another.

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Borderland GeologyBorderland GeologyMiocene and OlderMiocene and Older

Miocene SedimentaryMiocene Sedimentary and and Igneous RocksIgneous Rocks Dominate Dominate

Seafloor OutcropsSeafloor Outcrops

Miocene Igneous Rocks.Miocene Igneous Rocks.Large Crater Structures,Large Crater Structures,and and Catalina SchistCatalina Schist exist exist within the Core Complexwithin the Core Complex

Eocene, Paleocene, and Eocene, Paleocene, and Upper CretaceousUpper Cretaceous

Sedimentary Rocks crop Sedimentary Rocks crop out within the Nicolas and out within the Nicolas and

Patton Patton TerranesTerranes

Inner Borderland RiftInner Borderland Rift

Outer Borderland Outer Borderland AccretionaryAccretionary WedgeWedge

Franciscan RocksFranciscan Rocks are are found within the Patton found within the Patton

TerraneTerrane

PattonPatton

Nicolas

Nicolas

Catalina

CatalinaWestern Transverse RangesWestern Transverse Ranges

Baja California Baja California Seamount Seamount ProvinceProvince

Mapped geology of the southern California region showing Miocene and older rocks – Note the broad distribution of Miocene sedimentary and volcanic rocks in the Borderland. Outer Borderland has some Paleogene and older rocks, Inner Borderland has Mesozoic basement (Catalina Schist) – some schist crops out in the Patton terrane, too.

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Inner Borderland RiftInner Borderland RiftRightRight--Stepping RightStepping Right--Slip Slip FaultsFaultsSan San ClementeClemente & Catalina faults& Catalina faults

ElsinoreElsinore, San Jacinto & San Andreas, San Jacinto & San Andreas

Calderas within Core ComplexCalderas within Core ComplexAvalon, Emery Knoll, Catalina, NavyAvalon, Emery Knoll, Catalina, Navy

ConejoConejo & Glendora& Glendora

Is there aIs there a Miocene Miocene BathollthBathollth??

Miocene Miocene TranstensionalTranstensional BasinsBasinsSanta CruzSanta Cruz--Catalina Ridge (SCCR) & Catalina Ridge (SCCR) & San San ClementeClemente

Oceanside & Coronado BankOceanside & Coronado Bank

TorranceTorrance--Wilmington, Palos Wilmington, Palos VerdesVerdes

NewportNewport--Inglewood & Puente HillsInglewood & Puente Hills

San Diego Trough & IB Rift Axis follow ancient subduction trendsSan Diego Trough – Late Cretaceous Strandline (Santillan y Barrera)

Major Inner Borderland faults appear to be right-stepping en echelon – like the Gulf of California linking pull-apart basins with transform faults. Large calderas probably related to slab window or gaps during Miocene plate boundary reorganization –circular morphology provides large piercing points to estimate right-slip (~60 km) on the San Clemente fault zone. Distinctive fault trends record major episodes in the plate boundary evolution from subduction to transform with Miocene rifting followed by transpression (in the north).

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San Pedro BaySan Pedro Bay

Western Shelf of Western Shelf of Los Angeles BasinLos Angeles Basin

Major Hydrocarbon Major Hydrocarbon ProductionProduction

Abundant MCS DataAbundant MCS Data22--D and 3D and 3--DD

Numerous Well LogsNumerous Well Logs>3000>3000

Basin Stratigraphy is Well-Constrained

Basin Basin StratigraphyStratigraphy is is COMPLEX!COMPLEX!

Right Step-Over

Excellent subsurface geologic control is provided by widespread seismic profiles and well logs in the profilic hydrocarbon province of the Los Angeles Basin. 3-D seismic data volume and numerous wells (published logs) are available to map the subsurface structure and stratigraphy needed to evaluate the deformation history and earthquake potential. Note the right-stepping en echelon character of the THUMS-HB fault, typical of major southern California faults (including San Jacinto, Elsinore and San Andreas).

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“Yo-Yo” style of vertical tectonics, where blocks have been alternately subsided and uplifted is evident in the stratigraphy across the Wilmington Graben (San Pedro Bay). Thick Miocene sequences are found in the Palos Verdes Anticlinorium and Huntington Beach anticline, whereas the modern graben has only a thin Miocene sequence over schist basement.

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Active StrikeActive Strike--Slip Slip Vertical Fault ZoneVertical Fault Zone

Abandoned(?) StrikeAbandoned(?) Strike--Slip Slip NonNon--Vertical Fault ZoneVertical Fault Zone

3-D Seismic(Chevron/USGS)

Lower PicoLower Pico

Schist BasementSchist Basement

RepettoRepetto

Upper MioceneUpper Miocene

““YoYo--YoYo”” Tectonics in CrossTectonics in Cross--SectionSection

In-Line seismic profile from 3-D seismic data volume across the Wilmington Graben shows the thick Miocene wedge adjacent to the Palos Verdes fault and thick Pliocene wedge in the Wilmington Graben, thickening toward the THUMS-Huntington Beach fault.

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WC80WC80--191 (2191 (2--D)D)Well Log Well Log –– Seismic Correlation Seismic Correlation

Large Dots Large Dots -- SorlienSorlien

Fine Dots Fine Dots –– Legg (3Legg (3--D)D)

Well Picks – D. Clarke

Comparison of stratigraphic correlations from well logs to seismic profiles – 2-D profile shown (compare with previous slide). Dotted picks are from 2-D seismic profiles [Sorlien and Kamerling 2013]; fine dotted lines are from 3-D seismic volume [Legg, 2010]. The close match of the two independent interpretations assure confidence in the seismic stratigraphy. Note that differences between 2-D and 3-D seismic horizons may be locally significant due to the “off-line” effects (side-swipe, cross-dip, etc.)

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Santa Cruz-Catalina Ridge - Miocene Basin

Uplift along Vertical Uplift along Vertical Fault ZoneFault Zone

Miocene Miocene BasinBasin

Seismic Stratigraphy: after Sorlien et al. 2013

Transpression along the Santa Cruz-Catalina Ridge produces vertical uplift of basement and tilting of adjacent Miocene basin sediments. Stratigraphy offshore away from direct well control is constrained by seafloor sampling of outcrops and seismic correlation across the basin (Santa Monica Basin).

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CoastalCoastalOffshoreOffshoreCatalina Catalina TerraneTerrane

Regional stratigraphy across the Inner Borderland Rift shows Miocene sedimentary and volcanic rocks overlying Catalina Schist basement complex within the rift (Catalina Terrane); Upper Cretaceous and Paleogene rocks are found on the mainland coast and shelf (Santa Ana Terrane - Peninsular Ranges)

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14Legg, Nicholson, and Sorlien, 1998

HighHigh--Angle Faults Angle Faults Offset DetachmentOffset Detachment

Tilted Block

Core Complex

Inner Borderland RiftInner Borderland Rift

VE~4x @ Seafloor

South Coronado Island

Lamb, 1974

The San Diego Trough provides a cross-section of a major half-graben produced by oblique-rifting above a low-angle detachment, block tilting, and both footwall and hanging wall deformation. Vertical strike-slip faults cut through the thinned crust along the axis of the graben.

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Middle Miocene Geologic ReconstructionMiddle Miocene Geologic Reconstruction

60 km

40 km 15 km

Legg, 1991

Sixty kilometers of right-slip was removed on the San Clemente fault, 40 km dextral oblique-slip across San Diego Trough, and 15 km dextral oblique-slip on Coronado Bank fault zone was used for this reconstruction. Miocene volcanic rocks on San Clemente Island and Rosarito Beach formation (northern Baja) are in proximity of major volcanic centers (craters = calderas). Also, northern (Tijuana) part of RosaritoBeach fm and South Coronado Island are nearly adjacent to exposed Catalina Schist basement on the Thirtymile Bank escarpment – San Onofre Breccia is found on S. Coronado and Rosarito Beach fm.

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16Bohannon & Reiss, after Platt, 1975

Geology of Santa Catalina IslandGeology of Santa Catalina Island

Geologic Map of Santa Catalina Island showing distribution of igneous rocks (pink and light blue) representing the Miocene volcano, and Catalina Schist metamorphic rocks (green shades)

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Two stratigraphic columns showing intrusion of Miocene igneous rocks into Catalina Schist basement complex. Radiometric ages updated in red from Luyendyk, Gans, and Kamerling, 1998

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Catalina Schist – Subduction ComplexMetaMeta--GraywackeGraywacke Trench SedimentsTrench Sediments

GreenschistGreenschist -- Oceanic CrustOceanic Crust BlueschistBlueschist -- Oceanic CrustOceanic Crust

Garnet Garnet AmbhiboliteAmbhibolite -- Continental CrustContinental Crust

Photographs of various types of Catalina Schist metamorphic rocks representing deep crustal and upper mantle environments

SerpentiniteSerpentinite –– Upper MantleUpper Mantle

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Graded Tuff(water-laid)

Miocene DiatomiteMiocene Diatomite

Dacite Dome

AndesiteAndesiteFlowFlow--BrecciaBreccia

AndesiteAndesite FlowFlow(sub(sub--aerial)aerial)

MioceneDiatomite

Two Harbors Two Harbors –– Miocene Volcanic and Sedimentary RocksMiocene Volcanic and Sedimentary Rocks

Photographs of Miocene rocks related to oblique-rifting and volcanism

AndesiteAndesite Dike SwarmDike Swarm

Palisades

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OffshoreOffshoreGeologic MapGeologic Map

JungerJunger & Sylvester, 1979& Sylvester, 1979

GranodioriteGranodiorite--QuartzQuartzDiorite Diorite PlutonPluton ononSanta Catalina IslandSanta Catalina Island

Complex CraterMorphology ofEmery Knoll includesCentral Uplift (Knoll)Filled Moat andBuried Outer Rim

Santa CatalinaSanta CatalinaIslandIsland

Emery KnollEmery Knoll

Inferred Miocene caldera at Emery Knoll is similar to volcanic structure of Santa Catalina Island – crater morphology at Catalina has been overprinted by the post-Miocene restraining bend uplift (rhomboidal pop-up)

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USGSUSGS--120 (44120 (44--channel, channel, unmigrunmigr))

San Clemente FaultThirtymile BankDetachment

Seismic profiles across the Catalina Crater (caldera) located east of San ClementeIsland. Central uplift is inferred to be former resurgent dome composed of Miocene intrusive rocks like the quartz diorite at Catalina Island. Moat is filled with Miocene sedimentary and volcaniclastic rocks and overlain by Pliocene to Recent sediments. Outer rim is middle Miocene and older volcanic and sedimentary rocks, including Catalina Schist basement complex. Line 120 is from USGS L4-94-SC, Line 952A is from Kelez, 1973 USGS cruises

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USGSUSGS--126126

WC82WC82--108108

Santa Rosa

Santa Rosa ––Cortes Ridge

Cortes Ridge

SCCRSCCR

Map of Miocene and older rocks with locations of MCS profiles across the two major transpressional ridges: Santa Rosa-Cortes (Ferrelo fault zone) and Santa Cruz-Catalina Ridge. Miocene and older basin sedimentary rocks have been uplifted along these transpressional fault zones.

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Profiles of 2 Profiles of 2 TranspressionalTranspressional Fault SystemsFault Systems

Broad Uplift – Relatively SmoothOphiolite Basement

Low Quaternary Slip Rate

Narrow Uplifts – Irregular and SharpIgneous & Catalina Schist Basement

Moderate Quaternary Slip Rate

Transpression in the Outer Borderland (Ferrelo) manifest as broad anticlinoriumcored by forearc basin sedimentary rocks; transpression in Inner Borderland is narrower zone with steep faults and tight folds cored by uplifted Miocene volcanic and older Catalina Schist basement rocks [Legg, Kohler, Natsumi, & Weeraratne, 2015]

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Santa Rosa Santa Rosa –– Cortes Ridge / San Nicolas BasinCortes Ridge / San Nicolas Basin

Right-Stepping Echelon Fault Zone Thrust Faulting on Transverse Structure

30 km Offset

30 km Offset

North-directed shortening evident as thrust earthquakes on the west-trending San Nicolas fault zone may result from crustal block collision (log-jam) between the Outer Borderland and the Western Transverse Ranges [Legg et al. 2015]

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Complex faulting within the Ferrelo fault zone shows the remnant Miocene normal separation faults north of Cortes Bank and steeply dipping late Quaternary strike-slip faulting along the valley to the west of the uplifted banks (post-Miocene transpression) [Legg et al. 2015]

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Tectonic Blocks of Southern CaliforniaTectonic Blocks of Southern California

CrustalCrustal blocks formed blocks formed during late Cenozoic during late Cenozoic tectonic evolution of tectonic evolution of PACPAC--NAM transform NAM transform plate boundaryplate boundary

Western Transverse Western Transverse Ranges & Outer Ranges & Outer Borderland rifted from Borderland rifted from continental margin and continental margin and created Oblique Rifts: created Oblique Rifts: Inner Borderland & Inner Borderland & Southern BorderlandSouthern Borderland

Peninsular Ranges & Borderland collision w/ WTR and Big Bend San Andreas creates offshore & coastal Transpression

Major crustal blocks offshore southern California are separated by major fault zones that developed during Miocene oblique-rifting as the plate boundary evolved from subduction to transform faulting

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Major Geological QuestionsMajor Geological QuestionsThink in 4Think in 4--D!!!!D!!!!

•• Interaction between highInteraction between high--angle and lowangle and low--angle faultsangle faults•• Basement contacts Basement contacts –– between Peninsular Ranges, between Peninsular Ranges,

Inner Borderland Rift, Outer Borderland, Pacific Inner Borderland Rift, Outer Borderland, Pacific BasinBasin

•• Is there a Miocene Inner Borderland Batholith?Is there a Miocene Inner Borderland Batholith?•• What mechanism depresses the brittleWhat mechanism depresses the brittle--ductile ductile

transition in the extended Borderland crust?transition in the extended Borderland crust?•• Do earthquakes occur within the mantle beneath the Do earthquakes occur within the mantle beneath the

Borderland?Borderland?Note: 5Note: 5--D including D including RheologyRheology

Workshop on Establishing a Geologic Framework in Southern CaliforniaKellogg West Conference Center, Pomona, CA -- 8-9 June 2016

Defining the deformation history of the California Continental Borderland (and southern California) is a complex problem that requires understanding the time-varying, 3-D geological structure and stratigraphy and relative plate motions. Time-variations in rheology must also be considered as the hot ductile(?) lithosphere during the middle Miocene rifting episode cooled and became more brittle after migration of the East Pacific Rise away from the region.

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Borderland Microplate TectonicsBorderland Microplate Tectonics

Western Transverse Ranges Western Transverse Ranges –– Rotated Rotated ForearcForearc TerraneTerrane

So. California Shear Zone So. California Shear Zone –– N Peninsular Ranges & N Peninsular Ranges & Inner Borderland RiftInner Borderland Rift

Baja California Microplate –Peninsular Ranges South of Agua Blanca Fault (+ Intact Forearc South of Popcorn Ridge)

Outer Borderland Outer Borderland –– ForearcForearc& & AccretionaryAccretionary WedgeWedge

Southern Borderland Southern Borderland ––Rifted Continental MarginRifted Continental Margin

Popcorn Ridge

Major tectonic features of the southern California region considered as pieces of a splintered Baja California microplate where it collides with the Western Transverse Ranges and San Andreas restraining bend – an “Organized Train Wreck” that continues to deform

Offshore Geology: Continental Borderland and Paleo-Trench Mark R. Legg, Legg Geophysical, Inc.

SCEC – Workshop on Establishing a Geologic Framework in Southern California Kellog West Conference Center, Pomona, CA – 8-9 June 2016

References

Bohannon, R.G., and C. Reiss, 2004, Preliminary Geologic Map of Santa Catalina Island, U.S. Geological Survey, unpublished map sheet.

California Geological Survey (CGS) (2010), Fault Activity Map of California, California Geological Survey, Sacramento, Scale 1:750,000.

California Division of Mines and Geology (CDMG), CD 2000-007 (2000) GIS Data for the Geologic Map of California.

Gastil, R.G., and R.H. Miller, 1984, Prebatholithic paleogeography of peninsular California and adjacent Mexico, in Frizzell, V.A., Jr., ed., Geology of the Baja California Peninsula: Pacific Section, SEPM, v. 39, P. 9-16.

Junger, A., and A.G. Sylvester, 1979, Origin of Emery Seaknoll, southern California Borderland, EOS Trans. AGU, v. 60, p. 951.

Lamb, T.N., 1974, Geology of the Coronado Islands, Baja California, Mexico: M.S. thesis, San Diego State University, 221 p.

Lamb, T.N., 1992, Geology of the Coronado Islands, in Perry, L., ed., Natural History of the Coronado Islands (revisited 1992), San Diego Association of Geologists Field Trip Guidebook, p. 32-83, 3 pl.

Legg, M.R., 1991, Developments in understanding the tectonic evolution of the California Continental Borderland: in Osborne, R.H., ed., From Shoreline to Abyss: Shepard Commemorative Volume, SEPM Special Publication 46, p. 291-312.

Legg, M.R., 2011, Wilmington Graben Geophysical Investigation, Legg Geophysical Project Quarterly Report to Terralog Technologies, DOE Grant: Characterization of Pliocene and Miocene Formations in the Wilmington Graben, Offshore Los Angeles, for Large-Scale Geologic Storage of CO2 , 4 p.

Legg, M. R., Nicholson, C., and Sorlien, C., 1998, Late Cenozoic tectonic evolution of the San Diego Trough region, offshore southern California: [Abstract] Cordilleran Section, Geological Society of America, Annual Meeting, Long Beach, CA.

Legg, M. R., M. D. Kohler, N. Shintaku, and D. S. Weeraratne, 2015, High-resolution mapping of two large-scale transpressional fault zones in the California Continental Borderland: Santa Cruz-Catalina Ridge and Ferrelo, Journal of Geophysical Research: Earth Surface, vol. 120, doi:10.1002/2014JF003322.

Legg, M.R., Nicholson, C., Goldfinger, C., Milstein, R., and Kamerling, M., 2004, Large enigmatic crater structures offshore southern California: Geophysical Journal International, vol. 158, p. 803-815.

Lonsdale, P. 1991. Structural patterns of the Pacific floor offshore of Peninsular California. in Dauphin, P., & Ness, G. eds. The Gulf and Peninsular province of the Californias. American Association of Petroleum Geologists Memoir #47, 87-125.

Luyendyk, B. P., P. B. Gans, and M. J. Kamerling (1998), 40Ar/39Ar Geochronology of southern California Neogene volcanism, in Weigand, P. W., editor, Contributions to the Geology of the Northern Channel Islands, Southern California: American Assoc. Petroleum Geologists, Pacific Section, Ventura, 9-47.

Platt, J. P., 1976, The petrology, structure, and geologic history of the Catalina Schist terrain, southern California: University of California Publications in the Geological Sciences, v. 112, p. 1-111.

Reed, J.B., 1989, Lower Triassic(?) strata in the Vallecitos – San Marcos area, Baja California, in Abbott, P.L., ed., Geologic Studies in Baja California, Pacific Section SEPM Book 63, Bakersfield, CA, p. 87-102.

Santillan, M., y T. Barrera, 1930, Las posibilidades petrolíferas en la costa occidental de la Baja Cali-fornia, entre los paralelos 30° y 32° de latitud norte: México Instituta Geología Anales, v. 5, p. 1-37.

Sorlien, C.C., B.A. Campbell and L. Seeber, 2009, Geometry, kinematics, and activity of a young mainland-dipping fold and thrust belt: Newport Beach to San Clemente, California, U.S. Geological Survey Final Tech. Report 08HQGR0103, 25 p

Offshore Geology: Continental Borderland and Paleo-Trench Mark R. Legg, Legg Geophysical, Inc.

SCEC – Workshop on Establishing a Geologic Framework in Southern California Kellog West Conference Center, Pomona, CA – 8-9 June 2016

Sorlien, C. C., B. P. Luyendyk, L. Seeber, K. G. Broderick, W. R. Normark, M. A. Fisher, and R. W. Sliter (2013), The Palos Verdes anticlinorium along the Los Angeles, California coast: Implications for underlying thrust faulting, Geochemistry, Geophysics, Geosystems: 14, diuL19,1992/ggge.20112.

Vedder, J. G., 1987, Regional geology and petroleum potential of the southern California borderland: in Scholl, D. W., Grantz, A., and Vedder, J. G., eds., Geology and resource potential of the continental margin of western North America and adjacent ocean basins, Beaufort Sea to Baja California: Circum-Pacific Council for Energy and Mineral Resources, Houston, Texas, Earth Science Series, volume 6, p. 403-447.

Vedder, J. G., D. G. Howell, and J. A. Forman (1979), Miocene strata and their relation to other rocks: Santa Catalina Island, California, in Armentrout, J. M., M. R. Cole, and H. Terbest, Jr., eds., Cenozoic Geology of the Western United States, Pacific Coast Paleogeography Symposium 3, Soc. Econ. Paleontologists and Mineralogists, 239-256.

Wright, T. L. 1991. Structural geology and tectonic evolution of the Los Angeles basin. in Biddle, K. T., (ed) Active Margin Basins. American Association of Petroleum Geologists Memoir No. 52, 13-134.