Big Pine Fault Research Articles

Late Quaternary alluviation and offset along the eastern Big Pine fault, southern California

Determining late Quaternary offset rates on specific faults within active mountain belts is not only a key component of seismic hazard analysis, but sheds light on regional tectonic development over geologic timescales. Here we report an estimate of dip–slip rate on the eastern Big Pine oblique-reverse fault in the upper Cuyama Valley within the western Transverse Ranges of southern California, and its relation to local landscape development. Optically stimulated luminescence (OSL) dating of sandy beds within coarse-grained alluvial deposits indicates that deposition of alluvium shed from the Pine Mountain massif occurred near the southern margin of the Cuyama structural basin at the elevation of the Cuyama River between 25 and 14 ka. This alluvial deposit has been offset ∼ 10 m vertically by the eastern Big Pine fault, providing a latest Quaternary dip–slip rate estimate of ∼ 0.9 m/ky based on a 50° fault dip. Incision of the adjacent Cuyama River has exposed a section of older Cuyama River sediments beneath the Pine Mountain alluvium that accumulated between 45 and 30 ka on the down-thrown footwall block of the eastern Big Pine fault. Corroborative evidence for Holocene reverse-slip on the eastern Big Pine fault is ∼ 1 m of incised bedrock that is characteristically exposed beneath 2–3.5 ka fill terraces in tributaries south of the fault. The eastern Big Pine fault in the Cuyama Valley area has no confirmed record of historic rupture; however, based on our results, we suggest the likelihood of multiple reverse-slip rupture events since 14 ka.

Taking apart the Big Pine fault: Redefining a major structural feature in southern California

New mapping along the Big Pine fault trend in southern California indicates that this structural alignment is actually three separate faults, which exhibit different geometries, slip histories, and senses of offset since Miocene time. The easternmost fault, along the north side of Lockwood Valley, exhibits left‐lateral reverse Quaternary displacement but was a north dipping normal fault in late Oligocene to early Miocene time. The eastern Big Pine fault that bounds the southern edge of the Cuyama Badlands is a south dipping reverse fault that is continuous with the San Guillermo fault. The western segment of the Big Pine fault trend is a north dipping thrust fault continuous with the Pine Mountain fault and delineates the northern boundary of the rotated western Transverse Ranges terrane. This redefinition of the Big Pine fault differs greatly from the previous interpretation and significantly alters regional tectonic models and seismic risk estimates. The outcome of this study also demonstrates that basic geologic mapping is still needed to support the development of geologic models.

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

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.

The Tejon Pass Earthquake of 22 October 1916: An M 5.6 Event on the Lockwood Valley and San Andreas Faults, Southern California

On 22 October 1916, a moderate earthquake occurred in the vicinity of Tejon Pass and was felt over much of southern California. An intriguing aspect of this event involves reports of ground cracks that formed during the earthquake. We evaluate the reports of ground cracking and attempt to precisely locate the cracks with respect to active faults; we infer that the earthquake produced minor fault rupture along a newly discovered trace of the easternmost Lockwood Valley fault (formerly mapped as the easternmost Big Pine fault) and/or along the San Andreas fault. We also re-evaluate and present new intensity data, and we use a grid-search algorithm (derived from empirical analysis of modern earthquakes) to find the magnitude most consistent with the reported intensities. Although previous authors have attempted to use intensity data to constrain the magnitude of this event, the algorithm we use provides an alternative and statistically more robust determination of the magnitude. Our results suggest M 5.6 (-0.3/0.2) (at 95% confidence) for the 1916 event, which is consistent with earlier work. The 1916 earthquake appears to have been a rare and remarkable event in terms of its size and location and the production of minor surface rupture.

Middle Tertiary Extension Recorded by Lacustrine Fan-Delta Deposits, Plush Ranch Basin, Western Transverse Ranges, California

ABSTRACT The Plush Ranch Formation (upper Oligocene and lower Miocene) consists of more than 1800 m of nonmarine sedimentary and volcanic rocks that record the history of an extensional basin referred to here as the Plush Ranch basin. Distinctive depositional facies, provenance, and sediment transport directions along each basin margin suggest an asymmetric basin shape that is consistent with a half-graben origin. The northern basin margin consists of sandstone-dominated alluvial-plain deposits (0.1-1.5 m thick, normally graded, lenticular sandstone beds). Small deltaic sequences 1-2 m thick were formed where these alluvial systems flowed southward into a lake. Lenses of massive, boulder-rich granitic breccia that represent rockslide deposits derived from a nearby northern granitic provenance nterfinger with the alluvial-plain facies. In contrast to the northern margin, the southern basin margin is represented by coarse-grained fan-delta deposits. Matrix- and clast-supported lenticular conglomerate beds 0.2-5 m thick with interbedded trough-cross-bedded pebbly sandstone represent braided-stream and flood-flow and/or noncohesive debris-flow deposits of alluvial fans that drained a highland area to the south. The alluvial-fan deposits interfinger to the north with several types of subaqueous sediment-gravity-flow facies including turbidite sandstone beds and matrix-supported debris-flow conglomerate. Each of the basin-margin depositional systems grades basinward and to the east into lacustrine deposits that include organic-rich dark shale, evaporite, and limestone. The lacustrine deposits represent the central and eastern parts of the Plush Ranch basin, which received little coarse siliciclastic sediment. Basalt deposits that are at least 50 m thick in the west and thicken eastward are interbedded mainly with the lacustrine facies. The southern margin of the Plush Ranch basin formed along a north-dipping, normal-slip fault along which dip separation increased toward the southwest; the northern margin developed on the tilted hanging-wall block of this fault. This fault was later reactivated in post-middle Miocene time as the present left-lateral strike-slip Big Pine fault. The Plush Ranch is one of several extensional and transtensional basins that formed in southern California and western Arizona about 25-20 Ma as a response to the change from a convergent to a strikeslip tectonic regime along western North America.

Crustal strain near the Big Bend of the San Andreas Fault: Analysis of the Los Padres‐Tehachapi Trilateration Networks, California

In the region of the Los Padres‐Tehachapi geodetic network, the San Andreas fault (SAF) changes its orientation by over 30° from N40°W, close to that predicted by plate motion for a transform boundary, to N73°W. The strain orientation near the SAF is consistent with right‐lateral shear along the fault, with maximum shear rate of 0.38±0.01 μrad/yr at N63°W. In contrast, away from the SAF the strain orientations on both sides of the fault are consistent with the plate motion direction, with maximum shear rate of 0.19±0.01 μrad/yr at N44°W. The strain rate does not drop off rapidly away from the fault, and thus the area is fit by either a broad shear zone below the SAF or a single fault with a relatively deep locking depth. The fit to the line length data is poor for locking depth d less than 25 km. For d of 25 km a buried slip rate of 30 ± 6 mm/yr is estimated. We also estimated buried slip for models that included the Garlock and Big Pine faults, in addition to the SAF. Slip rates on other faults are poorly constrained by the Los Padres‐Tehachapi network. The best fitting Garlock fault model had computed left‐lateral slip rate of 11±2 mm/yr below 10 km. Buried left‐lateral slip of 15±6 mm/yr on the Big Pine fault, within the Western Transverse Ranges, provides significant reduction in line length residuals; however, deformation there may be more complicated than a single vertical fault. A subhorizontal detachment on the southern side of the SAF cannot be well constrained by these data. We investigated the location of the SAF and found that a vertical fault below the surface trace fits the data much better than either a dipping fault or a fault zone located south of the surface trace.

Russell Fault: Early Strike-Slip Fault of California Coast Ranges

The subsurface Russell fault is a controlling structure for oil fields in the Cuyama basin in the southern Salinian block of coastal California. Movement on the Russell fault began at about 23 Ma following deposition of the Oligocene Simmler Formation in extensional basins bounded on the south by normal-fault ancestors of the La Panza and Ozena reverse faults. Right-lateral strike slip on the Russell fault began with deposition of the Soda Lake Shale Member of the Vaqueros Formation. The Soda Lake Shale Member and Painted Rock Sandstone Member of the Vaqueros Formation were deposited in west-trending, right-stepping troughs, while most of the right slip on the Russell fault accumulated 23-19 Ma. Pre-Vaqueros strata are offset 26-29 km, but Vaqueros isopachs are offset onl 3.7 km. The Whiterock Bluff Shale Member of the Monterey Formation is dated as 16.5-14 Ma; the facies boundary between the Whiterock Bluff Shale Member and the Branch Canyon Sandstone is offset 3-3.4 km. Coeval subsidiary faults near the Russell fault in Miocene strata at least as young as 11 Ma also support distributed right-lateral shear. The Russell fault is overlain unconformably by the Morales Formation, which includes strata as old as 4 Ma ± 1 m.y. North of Russell Ranch oil field, the Russell fault bifurcates into a western strand that joins the Chimeneas fault and an eastern strand that is overridden by the Big Spring reverse fault. The Russell fault may continue to the southeast as the Ozena fault and be offset across the Big Pine fault. Right slip began 6-7 m.y. after the predicted time of first contact of the Pacific and North American plates. Slip rates were 6.5-7 mm/yr during 23-19 Ma, 0.1-0.3 mm/yr during 19-14 Ma, and 0.3-1.1 mm/yr during 14-4 Ma. The sudden decrease in slip rate occurred as the basin deepened at the time of Monterey Formation deposition, which began about 19 Ma. The relation of development of Vaqueros basins containing Soda Lake Shale Member to strike slip on the Russell fault suggests that a reconstruction of the early Miocene strike-slip tectonics of the southeastern Coast Ranges may permit exploration for other hidden Vaqueros basins elsewhere in the Salinian block.

Kinematic evolution of the junction of the San Andreas, Garlock, and Big Pine faults, California

If the San Andreas fault with about 300 km of right slip, the Carlock fault with about 60 km of left slip, and the Big Pine fault with about 15 km of left slip are considered to have been contemporaneously active, a space problem at their high-angle junctions becomes apparent. Large crustal masses converge in the area of the junctions as a result of the simultaneous large displacements on the faults. We present here a model in which an early straight north-northwest–trending San Andreas deforms to its present bent configuration in response to a westward displacement of crust north of the Garlock fault. During this deformation, the crust north of the Garlock in the vicinity of the junction undergoes north-south shortening, while the fault junction migrates along the trace of the San Andreas fault to the southeast relative to its original position. As a result of this migration, the Mojave area is displaced to the east relative to the original junction position. We suggest a similar history in mirror image for the Big Pine fault and the areas of crust adjacent to it.

Rinconada Fault in Southern Coast Ranges, California and Its Significance: ABSTRACT

The Rinconada fault near Santa Margarita is a major northwest-trending, high-angle fault that separates a terrane of granitic basement on the northeast from one of Franciscan basement on the southwest. Southeastward from Santa Margarita this fault extends continuously into the fault across Cuyama Gorge to intersect the Big Pine fault in the San Rafael Mountains. Northwestward the Rinconada fault does not extend into the Nacimiento fault near the Nacimiento River, as presumed, but veers northward through Paso Robles into a line of faults locally called San Marcos, Jolon, and Espinosa faults, nearly to Reliz Canyon west of King City. Detailed mapping reveals that all these aligned faults are parts of one major fault, 160 mi long. Therefore, it is proposed to call it the Rinconada fault. It is separated by a 2-mi gap from the Reliz fault, aligned northwest along the base of Sierra de Salinas. The Rinconada fault, as defined herein, is nearly parallel with, and about 22 mi southwest, of the San Andreas fault. Southeastward from Santa Margarita the Rinconada fault is along the southwestern border of the Salinia block; northwestward from that town it extends into this block. Drag folding along and near the Rinconada fault indicates right-lateral movement. Much of this movement occurred before deposition of the Paso Robles Formation. Strata of Miocene and early Pliocene ages are offset about 11 mi near Paso Robles; tho e of Late Cretaceous-early Tertiary age are offset nearly 40 mi. End_of_Article - Last_Page 432------------

Active rift system in the basin and range province

The active rift system along the postulated landward extension of the East Pacific Rise into western North America (Heezen, 1960; Menard, 1960; Cook, 1961) consists of several active rift zones which follow belts of seismicity and probable high heat flow and include: (a)the belt of grabens along the eastern margin of the Sierra Nevada, the Walker Lane, and the Churchill Arc; (b)the system of great trenches extending through western Arizona, central Utah, southeastern Idaho, western Wyoming, western Montana, and British Columbia; and (c)the Rio Grande rift belt. The present paper reviews the following additional recent geophysical evidence that defines in more detail the active rift system in the eastern part of the Basin and Range province: 1. (1) In north central Utah, gravity surveys, together with refraction and/ or reflection seismic data along some profiles, indicate that the Wasatch Trench is a northward-trending belt of grabens about 160 miles long and up to 13 miles wide. 2. (2) In south central and southwestern Utah, gravity surveys indicate grabens adjacent to the northward-trending Sevier and Hurricane fault zones, which lie along the rift belt. 3. (3) In New Mexico, several gravity profiles across the Rio Grande rift belt indicate the width and depth of the grabens. 4. (4) Sparse data tentatively indicate high heat flow in the rift belts. The possible mechanism of the Late Cenozoic vulcanism and diastrophism in the Basin and Range province is explained by a postulated mantle convection current (associated with the formation of the Rise) that rose beneath the eastern part of the Basin and Range province (or perhaps the Colorado Plateau) and flowed westward (Cook, 1961). The active rift system is in the region of tension over the upwelling convection currents. To the west, in the region of translation and compression, it is postulated that the westward-moving mantle convection current dragged along the continental crust in the California region. The crustal drag caused a large continental-type block to move westward into the Pacific Ocean about 50–100 km in the California region between the landward projections of the Mendocino and Murray fracture zones, which were probably major lines of weakness existing before the formation of the East Pacific Rise. On the northern and southern margins of the block, respectively, the movement occurred along transcurrent and/or transform faults in: 1. (1) the Cape Mendocino area (Gorda escarpment). 2. (2) the Garlock fault, Big Pine fault, Channel Islands. Transverse Ranges, and Pinto Mountain fault areas. The westward movement of the block, which occurred along transcurrent and/or transform faults associated with these two fracture zones, probably caused: (a) the folding of the Coast Ranges in California along the frontal (i.e., west) segment of the block and (b) the bending of the San Andreas fault zone in two areas along the southern margin of the block. The right-lateral movement of the San Andreas fault zone is explained by a postulated second, northwestward-trending mantle convection current with a velocity gradient increasing southwest; this movement has apparently moved into the western Basin and Range province recently to cause transcurrent faulting there (Billings, 1960), and a change in the direction of the mantle convection currents there is postulated. The concept that a westward-moving continental-type crustal block has overridden the oceanic crust in the Pacific Ocean and that the driving force probably originated in the upper-mantle spreading beneath the Basin and Range province (or perhaps the Colorado Plateau) is fundamental to the interpretation of the Late Cenozoic tectonics in the southwestern United States. If the United States, along with the North American continent, has drifted westward as a consequence of the sea-floor spreading along the Mid-Atlantic Ridge and overriden the East Pacific Rise, as postulated by Vine (1966), the westward movement of the above-mentioned crustal block would constitute about 50–100 km of horizontal displacement in addition to the “normal” westward drift of the North American continent as a whole.

Relationship of Big Pine, San Guillermo, and Ozena Faults, Northwestern Ventura County, California: ABSTRACT

The Big Pine, San Guillermo, and Ozena faults are interpreted to have experienced significant strike-slip movement. The San Guillermo and Ozena faults are northwest-trending, southwest-dipping, high-angle reverse faults that once formed a continuous trace. This trace has been offset left-laterally about 8½ mi. by post-middle Pliocene movement on the ENE-trending, essentially vertical Big Pine fault (a possibility suggested by Hill and Dibblee, 1953). Prior to being offset, the continuous San Guillermo-Ozena fault experienced at least 3½ miles of right (?)-lateral movement in late Tertiary time. The case for the San Guillermo-Ozena fault correlation is based on the following criteria. (a) Both the San Guillermo and Ozena faults have the same general trend, are high-angle reverse faults, and juxtapose the same general stratigraphic sequences near their junctions with the Big Pine fault: SSW-dipping lower Eocene marine strata on the hanging wall against Miocene-Pliocene continental strata on the footwall. (b) Two additional correlative geologic features, a unique fault and a facies contact, intersect the Big Pine fault, and their offsets are compatible with the San Guillermo-Ozena fault correlation. Southwest of each fault in its respective locale are (1) a paralleling auxiliary fault containing a rhyolite intrusive found only in and around the auxiliary fault and (2) a facies contact within the Eocene section where the Juncal Formation is overlain by the Matilija (?) Formation. (c) Projected upward, the facies contact and the San Guillermo and Ozena faults intersect, forming a line which pierces the upward projection of the Big Pine fault in each locale. A calculated net slip of 8.5 miles in a direction that pitches 6° southwest along the Big Pine fault has raised relatively the south block, yielding a 4,700-foot dip-slip component. This explains minor stratigraphic differences around each fault. (d) Subsurface data show at least 3½ miles of lateral displacement along the Ozena fault and require the existence of an offset portion. The San Guillermo fault is the only logical correlative. End_of_Article - Last_Page 1088------------

Geology and Possible Tectonic Significance of Munson Creek Fault, San Rafael Mountains, California: GEOLOGICAL NOTES

The Munson Creek fault and its southern branch, the Tule Creek fault, are about halfway between the Big Pine fault on the N. and the Santa Ynez fault on the S. These latter 2 faults bound an intensely deformed tectonic belt intermediate between the Coast Range province at the N. and the Transverse Range province at the S. The western part of the Munson Creek fault transects part of this transitional belt and is nearly aligned with the eastern part of the Big Pine fault and western part of the San Ynez fault. All these faults show left-lateral movement, suggesting the existence of a transcurrent shear zone within basement rocks which underlie the thick cover of Miocene to Cretaceous sedimentary rocks broken by these faults. The Garlock fault may be the part of this shear zone NE. of the San Andreas fault. Westward the shear zone approaches and is aligned with the Murray fracture zone which has been traced 1800 mi. across the Pacific Ocean.

SAN ANDREAS, GARLOCK, AND BIG PINE FAULTS, CALIFORNIA

The Big Pine left lateral fault extends northeastward from Big Pine Mountain to the right lateral San Andreas fault, while the left lateral Garlock fault extends northeast from the San Andreas, but from a point 5 miles to the southeast. The Big Pine fault is considered the western segment of the Garlock fault as offset by the San Andreas. Movement on this Garlock-Big Pine fault zone appears to have caused the anomalous east-west trend of the San Andreas fault in this vicinity. Tens of miles of lateral movement have probably occurred on these faults with the possibility of a cumulative movement on the San Andreas of hundreds of miles since Jurassic time. Such distances are important elements in reconstructing paleogeologic conditions. The three concurrently active, long, steep, and deep faults are considered major conjugate shears which define a primary strain pattern of relative east-west extension and north-south shortening of an area of approximately 120,000 square miles. A northeast-southwest counterclockwise compressive couple, possibly set up by drag due to the deep-seated movement of rock material from the Pacific region, is tentatively postulated as causing the deformation in this large region.