Mason L. Hill

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.

Correlation of the marine Cenozoic formations of western North America

INTRODUCTION By Charles E. Weaver This is Number 11 of the series of correlation charts being prepared by the Committee on Stratigraphy of the National Research Council (Dunbar et al., 1942, p. 429–434.). It has been constructed by stratigraphers and paleontologists actively engaged in both field and laboratory research and is not purely a compilation of information sought for in the literature; it has resulted from continuous scientific investigations by some of the men most active in developing present-day conceptions concerning the classification of Cenozoic formations and the interpretation of the geologic history of the Cenozoic era in this part of the globe. As more critical data are obtained concerning the lithology, distribution, and stratigraphic relations of the rock formations and their contained faunas, the interpretations of the correlation and geologic history will become modified. Two schools of thought exist on the Pacific Coast regarding the classification of Cenozoic . . .

Newport-Inglewood Zone and Mesozoic Subduction, California

The Newport-Inglewood zone is a 45 mi long narrow belt of en echelon folds and faults which trends southeast through Miocene-Pleistocene sediments of the Los Angeles basin. Below is an inferred right slip fault, presumed to follow a contact separating the oceanic Catalina Schist facies from an eastern continental basement facies of granitic and associated metamorphic rocks. The Newport-Inglewood zone of deformation disappears abruptly on the northwest at the faulted south front of the Santa Monica Mountains, and it apparently ends gradually to the southeast near Newport, California. Displacement on the inferred basement fault, which is responsible for deformation in the overlying strata, mainly reflects Pliocene-Holocene north-south shortening (Pasadenan orogeny). The contact between oceanic and continental basement rocks is inferred to continue offshore, southeast of Newport, under Cenozoic and probably Late Cretaceous strata. These strata apparently are not deformed in a belt of folds and faults, as in the Los Angeles basin. The basement rock contact is inferred to continue to the southeast, passing along the west side of Baja California, for a total distance of more than 800 mi. It is assumed to have developed by a sea-floor contraction mechanism of east-west shortening in Cretaceous time (perhaps a late and western element of the Nevadan orogeny). It is named here the Southern California subduction zone, and it should not be confused with the Newport-Inglewood zone of deformation which developed over its northern segment at a later time and within a different strain system. This basement zone, along with what are called here the Coast Ranges and Great Valley subduction zones, are considered to mark the position of a Mesozoic oceanic trench which originally extended for more than 2,000 mi along the margin of the northeast Pacific Basin.

TECTONICS OF DEATH VALLEY REGION, CALIFORNIA

The north-northwest-trending Death Valley and Furnace Creek right-lateral slip fault zones border the Black Mountains, California. Other tectonic features in the Death Valley region appear compatible with this strike-slip strain system of northeast-southwest shortening and northwest-southeast relative extension. Accordingly, some of the Basin and Range structures of Tertiary to Recent age may be characterized by strike-slip rather than dip-slip faulting, and result from compressional rather than tensional dynamics.

Stratigraphy of Cuyama Valley-Caliente Range Area, California

The 1948 discovery of oil in Cuyama Valley has focused attention on the geology of this region. The development of stratigraphic data has necessitated the use of a number of new and redefined rock-stratigraphic terms. Therefore, the following names are submitted with the belief that their consistent usage will facilitate progressive geologic discussions and interpretations: Pattiway formation, Eocene (?); Simmler formation, continental Oligocene (?); Soda Lake sandstone, Soda Lake shale, and Painted Rock sandstone members of the lower Miocene Vaqueros formation; Saltos shale and the redefined Whiterock Bluff shale members of the lower and middle Miocene Monterey formation; Branch Canyon formation, middle Miocene; Caliente formation, continental lower and middle Miocene; Q atal formation, continental upper Miocene; and the redefined Morales formation, continental Pliocene (?). Other unnamed Eocene and Cretaceous strata occur in the area, but the assignment of rock unit names would be premature here. Igneous and metamorphic rocks consist of pre-Upper Cretaceous granitic and gneissic types and middle Miocene basaltic flows and sills. Most of the outcropping rock units have also been encountered in drill holes, and several of them are now proved as oil reservoirs.

San Andreas fault: History of concepts

The long and active San Andreas fault was revealed by the San Francisco earthquake of 1906. Strike-slip movement on a major crustal fracture was first established by that event. The elastic rebound theory was developed in an analysis of this earthquake. It was proposed in 1926 that cumulative horizontal movement on the San Andreas amounted to several miles, but such a great displacement was generally agreed to be unreasonable. In 1953, new evidence of cross-fault stratigraphic correlations of Pleistocene to Cretaceous rocks was presented which seemed to require tens to hundreds of miles of strike-slip displacement. Controversy and additional studies ensued, resulting in general acceptance of such movements by 1968. Since the 1965 proposal that the San Andreas is a transform fault, within a plate-tectonics mechanism, reservations about great horizontal movements of the Earth9s crust have been essentially eliminated. The single most important factor in delaying acceptance of miles of strike-slip on the San Andreas has been the long-continued confusion between fault separation and fault slip. Lawson, Noble, Taliaferro, Hill and Dibblee, Wilson, and a few others played the more leading roles in interpretations of the fault. Post-earthquake studies by Gilbert again confirmed his reputation as a great geologist. The San Francisco earthquake was the chief contributor to knowledge about the San Andreas, but now there are more questions than ever regarding the nature, geologic history, and significance of this important crustal structure. The present consensus about the role of the fault in local and global tectonics surely will be modified by revolutionary new conceptual models.

A Test of New Global Tectonics: Comparisons of Northeast Pacific and California Structures

Tectonic patterns and histories of parts of the northeast Pacific and California appear to be essentially unrelated, although both regions have been undergoing deformation for most of the past 100 m.y. This situation is indicated by contrasting the nearly east-west crustal shortening resulting from telescoping of the American and Pacific plates according to the new global tectonics, and the nearly north-south crustal shortening evidenced by the San Andreas strain system. Furthermore, none of the oceanic structures are known within the continental crust, nor can any of the continental structures be convincingly extended into the oceanic crust. Nor is there evidence that the San Andreas is a transform fault, or that it separates major crustal plates. Therefore, it seems pro ably that a tectonic discontinuity separates these two regions. It seems improbable that sea-floor movements, comprising expansion of the Atlantic and/or contraction of the Pacific, have caused Cenozoic deformation in this part of North America.

Geologic Environment of Cuyama Valley Oil Fields, California

Cuyama Valley, in the southeastern part of the Salinas-Cuyama Tertiary basin of the southern Coast Ranges of California, contains the major Russell Ranch and South Cuyama oil fields, which have produced respectively over 40 and 67 million barrels of 35° A.P.I.-gravity oil from unitized and pressure-maintained reservoirs since mid-1948 and mid-1949. Production from the fault-trapped reservoirs is derived respectively from 290 and 480 feet of Vaqueros (lower Miocene) sands at depths ranging from 2,800 to 4,300 feet; productive areas comprise 1,400 and 2,500 acres. In addition, there are three minor fields in Cuyama Valley. San Ardo, the only other major field, is located in the northwestern portion of the Salinas-Cuyama basin. This field produces 11.3° gravity oil from upper Miocene sands at depths of 1,800 to 2,400 feet, from an area of about 4,000 acres. Cumulative production to July 1, 1956 has been 50 million barrels. The Salinas-Cuyama basin, which is approximately 160 miles long and 28 miles wide, is bounded on the northeast and southwest by the San Andreas and Nacimiento fault zones, respectively. It is underlain by granitic basement and contains up to 7,000 feet of lower Miocene marine clastics. In the Cuyama portion of the Miocene basin a thick continental section grades southwestward into a very thick shallow-water marine section composed principally of deltaic sands. These, in turn, change rapidly southwestward to a thin section of marine organic shales and sands of the oil-producing, moderately shallow-water belt, which thins rapidly southwestward. These sharp thickness and facies changes are accentuated by reverse faults of probable Quaternary age. Locally these faults have a prominent str ke-slip component of displacement and conceal at least one important, old and steep lateral fault which further accentuated the stratigraphic changes. The original Salinas-Cuyama Miocene basin has been elongated many miles by cumulative movements on northwest-trending right lateral-slip faults which now juxtapose formerly widely separated sedimentary facies. In Cuyama Valley, one of these is the buried Russell fault which traps most of the oil, and another probable one, aided by reverse faulting, explains the close proximity of thick deltaic and thin basin facies.

New Global Tectonics Related to West Coast Structure: ABSTRACT

The current evidence, patterns, and history of seafloor spreading in the northeast Pacific; the character and history of the San Andreas system of deformation; and some geologic implications of their relations to a worldwide tectonic scheme are reviewed. The NE-trending East Pacific rise enters the Gulf of California from the Pacific Ocean. The essentially contemporaneous and parallel Gordo and Juan de Fuca ridges lie off the coasts of northern California and Oregon. According to the New Global Tectonics, the SE-trending San Andreas zone is a transform fault which connects these two segments of the World Rift system. Furthermore, according to the rigid-plate concept, the adjoining oceanic and continental blocks are moving northwest and southeast away from the oceanic ridges, and past each other along the San Andreas. On the other hand, according to the new comcepts, part of the sea-floor magnetic pattern and the northeast Pacific fracture zones (transform faults) indicate an earlier (10-30 m.y. ago) north-south oceanic ridge trend acc mpanied by east-west crustal extension. However, since the present crustal dynamics typified by the San Andreas system of deformation has been operative for a much longer time (at least 80 and possible for more than 135 m.y.), some doubt is cast on the interpretation of the San Andreas as a geologically young transform fault. These and other contrasting geophysical data and interpretations from the oceans tested against geologic data and interpretations from End_Page 2209------------------------------ the continents serve to emphasize tectonic discrepancies. This approach, versus searching for data and interpretations which tend to confirm the New Global Tectonics, may best stimulate both continental-based geologists and ocean-based geophysicists to obtain critical information leading to the true world tectonics. End_of_Article - Last_Page 2210------------

Some Aspects of Oil Exploration in California

Today, many of the industry9s critical problems result from an oversupply of relatively cheap oil because, on a worldwide basis, recent exploration has been too successful. California has had a glorious role in this petroleum exploration for a period of nearly 100 years. During most of this time it has ranked as the first or second oil-producing state. Furthermore, it has been a substantial foreign exporter of crude oil and products. The state9s production history is characterized by substantial annual increases up through 1953, and an annual decline since that year. The annual discovered reserves during this same period, however, show great fluctuations; since 1940 the annual discovered reserves have been relatively small and much below annual production. The principal oil-producing areas of California are the San Joaquin, Los Angeles, Ventura, Santa Maria, and Cuyama-Salinas basins. To the end of 1961, the 295 oil fields in the state have produced about 12.3 billion barrels of crude. The changing exploration methods are illustrated by the discovery of 6 selected oil fields. The Midway-Sunset field was discovered in 1901 by drilling near oil seeps. The Ventura Avenue oil field discovery in 1916 marked the early application of surface geology and the anticlinal theory. The Santa Fe Springs field in 1919 is important as the first discovery attributed to the geomorphologic concept of domal structure being reflected in alluviated surface topography. The 1936 Wilmington field discovery was the result of the early use of the seismic reflection method. This field is also famous as the world9s largest water-flooding operation. The Russell Ranch field discovered in 1948 exemplifies the combination of surface and subsurface geology. The Wheeler Ridge oil field discovered in 1922 in shallow Miocene sands was rediscovered in 1952 in Eocene sands below a subsurface thrust fault, an example of success by subsurface geology and deeper drilling. Present oil exploration is high in state offshore areas partly because of new techniques for drilling and completing wells in water. All petroleum geologists are challenged to find petroleum reserves at competitive costs, to contribute to the science of geology and its applications, to advance the professional competence of geologists, and to contribute to the economic prosperity of our states and our nation.