Locations and ages of middle Tertiary volcanic centers in coastal California

Stanley, Richard G.; Wilson, Douglas S.; McCrory, Patricia A.

doi:10.3133/ofr00154

Cited by 13 publications

(7 citation statements)

References 57 publications

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“…He divided these volcanic rocks into three age and geographic groups, namely, a mid‐Tertiary group with ages 27–22 Ma located primarily in central California; a mid‐Miocene group with ages 18–12 Ma primarily in southern California; and a post‐mid‐Miocene group with ages younger than 15 Ma showing a northward younging age progression through central and northern California. Our compilation of well‐determined ages (Table 1 and Figure 1, simplified from Stanley et al [2000]) includes numerous recently published dates not available for previous compilations. We find it useful to subdivide Dickinson's mid‐Tertiary group into an older group with ages 27–25 Ma that occurs within and slightly north of the Transverse Ranges, and a younger group with ages 24–22 Ma that extends well to the north.…”

Section: Volcanic Recordmentioning

confidence: 99%

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Implications of volcanism in coastal California for the Neogene deformation history of western North America

2005

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The geologic record of coastal California includes evidence of numerous volcanic centers younger than 30 Ma that do not appear to have erupted in an arc setting. By correlating these volcanic centers with specific slab windows predicted from analysis of magnetic anomalies on the Pacific plate, we add new constraints to tectonic reconstructions since 30 Ma. Our correlations, such as erupting the Morro Rock–Islay Hill complex south of the Pioneer fracture zone and the Iversen Basalt south of the Mendocino fracture zone, require larger displacements within western North America than advocated by most previous authors. Specifically, we infer at least 315 km of motion between the Sierra Nevada and rigid North America at an azimuth of about N60°W and at least 515 km between Baja California and rigid North America in a similar direction. A consequence of inferring a large displacement of Baja California is that the Pacific–North American plate boundary must have developed most of its current form prior to 10 Ma. We interpret a slab window developing between Cocos and Monterey plates after 19 Ma that reconstructs under nearly all of the southern California volcanic centers dated at 18–14 Ma. Most of the sedimentary basins associated with volcanic rocks show brief periods of rapid subsidence synchronous with volcanism, followed by slow subsidence of variable but often extended duration, consistent with rapid extension of cold lithosphere over recently introduced hot asthenosphere.

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Section: Volcanic Recordmentioning

confidence: 99%

“…Map showing approximate locations of late Oligocene through middle Miocene volcanic centers in coastal California (modified from Stanley et al [2000]). See Table 1 for explanation of letter symbols.…”

Section: Volcanic Recordmentioning

confidence: 99%

Implications of volcanism in coastal California for the Neogene deformation history of western North America

2005

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“…Pinos block were also structurally high during late Oligocene and Miocene time. Synextensional deposition was accompanied by emplacement of mostly basaltic flows and sills [ Stanley et al , 2000; Kellogg , 2003] that have K‐Ar ages ranging from 20.9 to 26.5 Ma [ Frizzell and Wegand , 1993]. This volcanic episode marks a period of late Oligocene‐early Miocene crustal extension coeval with clockwise block rotation farther south [ Hornafius et al , 1986].…”

Section: Late Oligocene To Recent Geologic Frameworkmentioning

confidence: 99%

Pliocene transpressional modification of depositional basins by convergent thrusting adjacent to the “Big Bend” of the San Andreas fault: An example from Lockwood Valley, southern California

Kellogg

Minor

2005

Tectonics

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The “Big Bend” of the San Andreas fault in the western Transverse Ranges of southern California is a left stepping flexure in the dextral fault system and has long been recognized as a zone of relatively high transpression compared to adjacent regions. The Lockwood Valley region, just south of the Big Bend, underwent a profound change in early Pliocene time (∼5 Ma) from basin deposition to contraction, accompanied by widespread folding and thrusting. This change followed the recently determined initiation of opening of the northern Gulf of California and movement along the southern San Andreas fault at about 6.1 Ma, with the concomitant formation of the Big Bend. Lockwood Valley occupies a 6‐km‐wide, fault‐bounded structural basin in which converging blocks of Paleoproterozoic and Cretaceous crystalline basement and upper Oligocene and lower Miocene sedimentary rocks (Plush Ranch Formation) were thrust over Miocene and Pliocene basin‐fill sedimentary rocks (in ascending order, Caliente Formation, Lockwood Clay, and Quatal Formation). All the pre‐Quatal sedimentary rocks and most of the Pliocene Quatal Formation were deposited during a mid‐Tertiary period of regional transtension in a crustal block that underwent little clockwise vertical‐axis rotation as compared to crustal blocks to the south. Ensuing Pliocene and Quaternary transpression in the Big Bend region began during deposition of the poorly dated Quatal Formation and was marked by four converging thrust systems, which decreased the areal extent of the sedimentary basin and formed the present Lockwood Valley structural basin. None of the thrusts appears presently active. Estimated shortening across the center of the basin was about 30 percent. The formerly defined eastern Big Pine fault, now interpreted to be two separate, oppositely directed, contractional reverse or thrust faults, marks the northwestern structural boundary of Lockwood Valley. The complex geometry of the Lockwood Valley basin is similar to other Tertiary structural basins in southern California, such those that underlie Cuyama Valley, the Ridge basin, and the east Ventura basin.

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“…The formation is older than the unconformably overlying Quail Lake Formation, a unit that contains upper Miocene fossils, but isotopic ages of the severely altered volcanic rocks themselves remain ambiguous. An age of between 24 and 21 Ma from potassium-argon investigations is probable (Turner et al, 1970;Barrows et al, 1985;Weigand and Thomas, 1989;Weigand and Swisher, 1991;Dickinson, 1997;Stanley et al, 2000). The remarkable similarity of the volcanic sequence, (including its petrography and chemical composition, and its interpreted age) to the sequence in the Pinnacles area of central California leads to the conclusion that the Neenach and Pinnacles volcanic fields were one and the same before disruption and disOverview of rocks bordering Ridge Basin, southern California placement by the San Andreas of 300-315 km (Matthews, 1973(Matthews, , 1976Weigand and Thomas, 1989;Frizzell and Weigand, 1993;Stanley et al, 2000).…”

Section: Neenach Volcanic Formationmentioning

confidence: 96%

Overview of rocks bordering Ridge Basin, southern California

Crowell¹

2003

Evolution of Ridge Basin, Southern California: An Interplay of Sedimentation and Tectonics

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Ridge Basin lies within a region of basement terranes overlain nonconformably by Cenozoic strata. The distribution and characteristics of these bordering rocks show that significant tectonic movements occurred before the origin of the basin, during its filling by Miocene and Pliocene sediments, and afterwards. These movements include uplift of sediment source areas, sinking of depositional sites, thrust faulting, folding, and noteworthy strike-slip faulting.Basement rocks bordering Ridge Basin on the west, constituting the Alamo-Frazier Mountain terrane southwest of the Canton and San Gabriel faults, consist of Precambrian gneiss, Mesozoic granite, and mylonite of the latest Cretaceous Alamo-Piru shear zones. A thick section of Tertiary strata nonconformably overlies this basement and interfinger westward into beds of the deep east Ventura Basin. These strata include Eocene marine Juncal and Matilija? Formations and nonmarine "Canton Canyon beds," Oligocene nonmarine Sespe Formation, and Oligocene-lower Miocene marine shale and sandstone of the Vaqueros and Rincon Formations. Coarse Sespe conglomerates containing boulders >8 m are interpreted as deposited along a fault scarp, probably the Canton fault, at the margin of the east Ventura Basin. Distinctive lithologies of the clasts, including anorthosite, Lowe Granodiorite, and Mendenhall Gneiss indicate derivation from basement terrane now exposed in the western San Gabriel Mountains. Southwest of the San Gabriel fault, the thick marine upper Miocene Modelo Formation overlies the Sespe Formation unconformably, and includes the Devil Canyon Conglomerate member containing clasts of gneiss and anorthosite and related rocks such as those exposed in the western San Gabriel Mountains. As discussed in the tectonics chapter in this volume, in order to match conglomerates with their inferred sources, dextral displacements of ~30 km are suggested on the Canton fault in mid-Miocene time before Ridge Basin originated, followed by displacements of 45 km on the San Gabriel fault as the basin received sediment. Later events in the Pliocene include thrusting along the Frazier Mountain thrust system and truncation of Ridge Basin on the north by the San Andreas fault. Terranes north of Ridge Basin across the San Andreas fault have very different histories from that of terranes south of the fault. The northern rocks include ancient gneiss and granite of Precambrian and Mesozoic age, and pendants of Jurassic? marble. Miocene volcanic rocks and marine and nonmarine strata nonconformably overlie this basement.Areas east of Ridge Basin and south of the San Andreas fault are underlain by Mesozoic granodioritic and gneissic rocks, including small masses of distinctive Triassic megaporphyritic monzogranite and "polka-dot" granite, as well as marble of uncertain but probable Paleozoic age. This basement is overlain nonconformably by

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Locations and ages of middle Tertiary volcanic centers in coastal California

Cited by 13 publications

References 57 publications

Implications of volcanism in coastal California for the Neogene deformation history of western North America

Implications of volcanism in coastal California for the Neogene deformation history of western North America

Pliocene transpressional modification of depositional basins by convergent thrusting adjacent to the “Big Bend” of the San Andreas fault: An example from Lockwood Valley, southern California

Overview of rocks bordering Ridge Basin, southern California

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