The Coldwater Sandstone (or Coldwater Formation) is a sedimentary geologic unit of Eocene age found in Southern California, primarily in and south of the Santa Ynez Mountains of Santa Barbara County, and east into Ventura County. It consists primarily of massive arkosicsandstone with some siltstone and shale. Being exceptionally resistant to erosion, outcrops of the Coldwater form some of the most dramatic terrain on the south slope of the Santa Ynez Mountains, with immense white sculpted slabs forming peaks, hogback ridges, and sheer cliff faces.[1]:32–33[2]
The type locality for the Coldwater Sandstone is in Coldwater Canyon, a western branch of the Sespe River a few miles north of Fillmore.[1]:32 The unit is typically around half a mile thick, ranging from 2,500 to 3,200 feet through most of its extent, although it thins westward to around 1,000 feet thick in the hills north of El Capitan State Beach. From there going west to Gaviota, the unit gradually grades into the Sacate Formation, a similar but shalier and more siltstone-rich unit which is also conformably overlain on the Cozy Dell Formation.[3] The Coldwater and Sacate Formations are sometimes considered as a single unit, particularly underneath the Santa Barbara Channel where they appear in drill cores. The Gaviota Formation is deposited conformably on top of the Coldwater-Sacate in the western part of the dual unit's extent, and the Sespe Formation appears conformably on top of it elsewhere.[4]
The Coldwater outcrops predominantly on the south slope of the Santa Ynez Range, and on the crest of the range at San Marcos Pass.[5] Cathedral Peak, the 3,333-foot prominence directly north of Santa Barbara, is within the Coldwater unit.[6] Because the sandstone beds are resistant to erosion, wherever they dip steeply, they form distinctive hogback ridges and dip-slopes, a topography particularly characteristic of the ridge north of Goleta, where the Coldwater accounts for almost all of the terrain above approximately 1,000 feet.[2][7] While the unit is exposed prominently throughout the Santa Ynez Mountains, it dips steeply to the south and vanishes underneath the coastal plain and then the Santa Barbara Channel. Well bores in the numerous oil and gas fields in the Channel show the Gaviota Formation overlying the Cozy Dell directly, with no intervening Coldwater, excepting the offshore portion of the Capitan Oil Field, in which the Coldwater Formation is present as a natural-gas-bearing unit, underlying the Gaviota.[8]
As a potential hydrocarbon resource, the unit is considered to be equivalent to the Sacate, and is grouped with the lower-lying Cozy Dell Shale and Matilija Sandstone as the Gaviota-Sacate-Matilija Sandstone Play. The likely source rocks for any petroleum accumulation in the Coldwater-Sacate are the lower-lying organic-rich shale units, such as the Cozy Dell and the Juncal-Anita Formations.[9] Since this deep-lying play is incompletely explored, the estimates for hydrocarbon resources are speculative, with the United States Bureau of Ocean Energy Management, Regulation and Enforcement giving a range of 117 to 127 million barrels of oil recoverable using current technology for the entire Santa Barbara-Ventura Basin Province.[9] Some onshore oil fields produce from the Coldwater, including the Ojai Oil Field north of Santa Paula and Sespe oil field north of Fillmore, not far from the type locality for the formation.[8]:506,508,510
Cave in Coldwater Sandstone at Lizard's Mouth Santa Ynez Range, CA
The unit is of middle to upper Eocene age, being deposited in a shallow marine environment, during a time in which the sea was receding and becoming more shallow.[10] Because the process was not uniform, with periods of shallow-water deposition alternating with deeper water conditions, the predominantly sandstone unit is interbedded with siltstones and shales, with the siltstone and shale making up around 20% of the total composition.[1]:32 Late in the period of deposition, large oyster beds appear in the stratigraphic record, indicating a brackish-water nearshore environment.[1]:34 The source rock for the sediment making up the Coldwater was mostly granitic, and pebbles or cobbles of granite and quartzite appear in some of the nearshore sandstones near the top of the unit.[1]:33 At its top the unit grades into the redbeds and conglomerates of the Sespe Formation, which was deposited in a floodplain, riverine, and estuarine environment onshore.[3]:83–84
A 1996 study by Donald R. Prothero and Robert J. Emry determined the age of the unit using magnetostratigraphy, and gave its period of deposition as from 39.5 Ma (million years ago) to 42.5 Ma.[11] Additionally, studies of the correlation of the underlying Cozy Dell and Matilija Sandstone with similar units in the California Central Valley, along with paleomagnetic data, show that the tectonic block on which the Coldwater and its surrounding formations were deposited – including the western part of the Transverse Ranges[12] – has rotated clockwise almost 90 degrees since the time of deposition, also moving north-northwest from its original location.[13][14] This finding is consistent with earlier studies that found evidence for the large clockwise rotation of the Transverse Ranges in California.[15][16][17] Uplift along the Santa Ynez Fault during the Quaternary period – the last 2.5 million years – has brought the Coldwater and the other formations up from their deposition environments to their present prominent locations in the Santa Ynez Range. In the area north and northeast of Santa Barbara, on the south slope of the Santa Ynez Mountains eastward to near Ojai, the compression and folding associated with tectonic movements have been sufficiently intense to overturn the rock units so that the older ones are on top. This stretch of overturned rock formations is known as the "Montecito Overturn".[3]:102
Paleontology
Fossils of numerous mollusks, including many species of the genus Turritella can be found in the Coldwater, particularly near the top of the formation where the water at time of deposition was shallowest. Outcrops along Old San Marcos Pass Road above Goleta and near the contact with the Sespe Formation are rich locations for finding remnants of these sea-snails.[1]:34 Elsewhere near the top contact with the Sespe, the remnants of oyster beds can be found.[18]
1 2 3 4 5 6 7 8 Dibblee, Thomas. Geology of the central Santa Ynez Mountains, Santa Barbara County, California. Bulletin 186, California Division of Mines and Geology. San Francisco, 1966. 99p.
1 2 Minor, S.A., Kellogg, K.S., Stanley, R.G., Gurrola, L.D., Keller, E.A., and Brandt, T.R., 2009, Geologic Map of the Santa Barbara Coastal Plain Area, Santa Barbara County, California: U.S. Geological Survey Scientific Investigations Map 3001, scale 1:25,000, 1 sheet, pamphlet, 38 p.
1 2 3 Norris, Robert M. (2003). The geology and landscape of Santa Barbara County, California. Santa Barbara, California: Santa Barbara Museum of Natural History. pp.80–81. ISBN0-936494-35-2.
↑ Dibblee, Thomas. Geology of Southwestern Santa Barbara County, California. State of California, Department of Natural Resources, Division of Mines, Bulletin 150. 1950. 28.
↑ Thomas M. Dibblee, 1987. Geologic Map of the San Marcos Pass Quadrangle, Santa Barbara County, California. California Department of Conservation, Division of Mines and Geology. Dibblee Foundation Map DF#08.
↑ Thomas M. Dibblee, 1986. Geologic Map of the Santa Barbara Quadrangle, Santa Barbara County, California. California Department of Conservation, Division of Mines and Geology. Dibblee Foundation Map DF#06.
↑ Thomas M. Dibblee, 1987. Geologic Map of the Goleta Quadrangle, Santa Barbara County, California. California Department of Conservation, Division of Mines and Geology. Dibblee Foundation Map DF#07.
1 2 California Department of Conservation, Division of Oil, Gas, and Geothermal Resources (DOGGR). California Oil and Gas Fields, Volumes I, II and III. Vol. I (1998), Vol. II (1992), Vol. III (1982). PDF file available on CD from www.consrv.ca.gov. p. 642
↑ Donald R. Prothero, Robert J. Emry. The terrestrial Eocene-Oligocene transition in North America. Cambridge University Press, 1996. p. 155, 165. ISBN0-521-43387-8
↑ Dibblee Jr, T.W., 1982. Regional geology of the Transverse Ranges Province of southern California. Geology and mineral wealth of the California Transverse Ranges, 10, pp.7-26.
↑ Donald R. Prothero and Justin R. Britt. "Magnetic stratigraphy and tectonic rotation of the Middle Eocene Matilija Sandstone and Cozy Dell Shale, Ventura County, California: implications for sequence stratigraphic correlations." Earth and Planetary Science Letters, Volume 163, Issues 1-4, November 1998, Pages 261-273. doi:10.1016/j.physletb.2003.10.071
↑ Deborah R. Harden. California Geology. Prentice Hall, 1997. ISBN0-02-350042-5 p. 433
↑ Luyendyk, Bruce P.; Kamerling, Marc J.; Terres, Richard R.; Hornafius, J. Scott (1985). "Simple shear of southern California during Neogene time suggested by paleomagnetic declinations". Journal of Geophysical Research. 90 (B14): 12454. Bibcode:1985JGR....9012454L. doi:10.1029/JB090iB14p12454. ISSN0148-0227.
The Transverse Ranges are a group of mountain ranges of southern California, in the Pacific Coast Ranges physiographic region in North America. The Transverse Ranges begin at the southern end of the California Coast Ranges and lie within Santa Barbara, Ventura, Los Angeles, San Bernardino, Riverside and Kern counties. The Peninsular Ranges lie to the south. The name Transverse Ranges is due to their east–west orientation, making them transverse to the general northwest–southeast orientation of most of California's coastal mountains.
The Los Angeles Basin is a sedimentary basin located in Southern California, in a region known as the Peninsular Ranges. The basin is also connected to an anomalous group of east-west trending chains of mountains collectively known as the Transverse Ranges. The present basin is a coastal lowland area, whose floor is marked by elongate low ridges and groups of hills that is located on the edge of the Pacific Plate. The Los Angeles Basin, along with the Santa Barbara Channel, the Ventura Basin, the San Fernando Valley, and the San Gabriel Basin, lies within the greater Southern California region. The majority of the jurisdictional land area of the city of Los Angeles physically lies within this basin.
The Santa Ynez Mountains are a portion of the Transverse Ranges, part of the Pacific Coast Ranges of the west coast of North America. It is the westernmost range in the Transverse Ranges.
The Dick Smith Wilderness is a wilderness area in the mountains of eastern Santa Barbara County, California, United States, with a portion in Ventura County. It is completely contained within the Los Padres National Forest, and is northeast of the city of Santa Barbara and north of the city of Ojai. It is most easily accessible from two trailheads off State Route 33, which runs north from Ojai. It is adjacent to the large San Rafael Wilderness on the west and the Matilija Wilderness on the south. Across Highway 33 to the east, and also in the Los Padres National Forest, is the large Sespe Wilderness.
Pine Mountain Ridge is a massif of the Transverse Ranges located in northern Ventura County, and entirely within the Los Padres National Forest. The ridge is a large block of Matilija Sandstone, and reaches some of the highest elevations in the southern Transverse Ranges. The north slope of the ridge is part of the Sespe Wilderness.
Simi Valley is a synclinal valley in Southern California in the United States. It is an enclosed or hidden valley surrounded by mountains and hills. It is connected to the San Fernando Valley to the east by the Santa Susana Pass and the 118 freeway, and in the west the narrows of the Arroyo Simi and the Reagan Freeway connection to Moorpark. The relatively flat bottom of the valley contains soils formed from shales, sandstones, and conglomerates eroded from the surrounding hills of the Santa Susana Mountains to the north, which separate Simi Valley from the Santa Clara River Valley, and the Simi Hills.
The Vaqueros Formation is a sedimentary geologic unit primarily of Upper Oligocene and Lower Miocene age, which is widespread on the California coast and coastal ranges in approximately the southern half of the state. It is predominantly a medium-grained sandstone unit, deposited in a shallow marine environment. Because of its high porosity and nearness to petroleum source rocks, in many places it is an oil-bearing unit, wherever it has been configured into structural or stratigraphic traps by folding and faulting. Being resistant to erosion, it forms dramatic outcrops in the coastal mountains. Its color ranges from grayish-green to light gray when freshly broken, and it weathers to a light brown or buff color.
The Mesa Oil Field is an abandoned oil field entirely within the city limits of Santa Barbara, California, in the United States. Discovered in 1929, it was quickly developed and quickly declined, as it proved to be but a relatively small accumulation of oil in a single geologic formation. While the field was active in the 1930s, residential development in most of the Mesa neighborhood of Santa Barbara came to a halt. The field included two major productive areas with a total surface extent of only 210 acres (0.85 km2), and produced 3,700,000 barrels (590,000 m3) of oil during its brief lifetime.
The Sespe Formation is a widespread fossiliferous sedimentary geologic unit in southern and south central California in the United States. It is of nonmarine origin, consisting predominantly of sandstones and conglomerates laid down in a riverine, shoreline, and floodplain environment between the upper Eocene Epoch through the lower Miocene. It is often distinctive in appearance, with its sandstones weathering to reddish-brown, maroon, pinkish-gray, tan, and green. Since many of its sandstones are more resistant to erosion than many other regional sedimentary units it often forms dramatic outcrops and ridgelines in many local mountain ranges.
The Sisquoc Formation is a sedimentary geologic unit widespread in Southern California, both on the coast and in mountains near the coast. Overlying the Monterey Formation, it is of upper Miocene and lower Pliocene age. The formation consists of claystone, mudstone, siltstone, shale, diatomite, and conglomerates, with considerable regional variation, and was deposited in a moderately deep marine environment at a depth of approximately 500–5,000 feet (150–1,520 m). Since some of its diatomites, along with those of the underlying Monterey Formation, are of unusual purity and extent, they can be mined as diatomaceous earth. France-based Imerys operates a mine in the Sisquoc and Monterey Formations in the hills south of Lompoc, California, the largest such operation in the world.
The Rincon Formation is a sedimentary geologic unit of Lower Miocene age, abundant in the coastal portions of southern Santa Barbara County, California eastward into Ventura County. Consisting of massive to poorly bedded shale, mudstone, and siltstone, it weathers readily to a rounded hilly topography with clayey, loamy soils in which landslides and slumps are frequent. It is recognizable on the south slopes of the Santa Ynez Mountains as the band at the base of the mountains which supports grasses rather than chaparral. Outcrops of the unit are infrequent, with the best exposures on the coastal bluffs near Naples, in the San Marcos Foothills, at the Tajiguas Landfill, and in road cuts. The geologic unit is notorious as a source of radon gas related to its high uranium content, released by radioactive decay.
The Cozy Dell Shale is a geologic formation of middle Eocene age that crops out in the Santa Ynez Mountains and Topatopa Mountains of California, extending from north of Fillmore in Ventura County westward to near Point Arguello, north of Santa Barbara. Because the Cozy Dell easily weathers to a clay-rich soil, it crops out infrequently and generally forms dense stands of chaparral in saddles between peaks and ridges of the more resistant Matilija and Coldwater formations.
The Matilija Sandstone is a sedimentary geologic unit of Eocene epoch in the Paleogene Period, found in Santa Barbara and Ventura Counties in Southern California.
The Juncal Formation is a prominent sedimentary geologic unit of Eocene age found in and north of the Santa Ynez Mountain range in southern and central Santa Barbara County and central Ventura County, California. An enormously thick series of sediments deposited over millions of years in environments ranging from nearshore to deep water, it makes up much of the crest of the Santa Ynez range north of Montecito, as well as portions of the San Rafael Mountains in the interior of the county. Its softer shales weather to saddles and swales, supporting a dense growth of brush, and its sandstones form prominent outcrops.
The Jalama Formation is a sedimentary rock formation widespread in southern Santa Barbara County and northern Ventura County, southern California. Of the Late Cretaceous epoch, the unit consists predominantly of clay shale with some beds of sandstone.
The Espada Formation is a sedimentary rock formation widespread in Santa Barbara County, California. Of late Jurassic to Cretaceous age, the unit consists primarily of shale with some interbedded thin layers of sandstone, conglomerate, and limestone.
Little Pine Mountain is a mountain in Santa Barbara County, California, in the Los Padres National Forest at the southern edge of the San Rafael Mountains. It separates the drainages of Oso Creek, which flows into the upper Santa Ynez River, from the drainage of Santa Cruz Creek, which flows into the middle section of the river via Lake Cachuma. The mountain is named for a thin grove of Coulter pines located on the summit.
The La Goleta Gas Field is a natural gas field in unincorporated Santa Barbara County, California, adjacent to the city of Goleta. Discovered in 1929, and first put into production in 1932, it has been in continuous use ever since, producing approximately 12 billion cubic feet of gas. With production declining, the field was converted into a gas storage reservoir in 1941. As of 2016 it remains one of the four gas storage facilities maintained by Southern California Gas Company (SoCalGas), a division of Sempra Energy, with the others being Aliso Canyon, Honor Rancho and Playa del Rey. It is the oldest storage facility of the four and the third largest, with a maximum capacity of 21.5 billion cubic feet. The storage facilities are necessary to balance load for the over ten million customers of SoCalGas: during summer months, when gas usage is at a minimum, gas is pumped into the reservoirs; and in the winter when usage is high, gas is withdrawn. The La Goleta field serves the northern portion of SoCalGas's geographic range.
The Matilija Wilderness is a 29,207-acre (11,820 ha) wilderness area in Ventura and Santa Barbara Counties, Southern California. It is managed by the U.S. Forest Service, being situated within the Ojai Ranger District of the Los Padres National Forest. It is located adjacent to the Dick Smith Wilderness to the northwest and the Sespe Wilderness to the northeast, although it is much smaller than either one. The Matilija Wilderness was established in 1992 in part to protect California condor habitat.
The geology of California is highly complex, with numerous mountain ranges, substantial faulting and tectonic activity, rich natural resources and a history of both ancient and comparatively recent intense geological activity. The area formed as a series of small island arcs, deep-ocean sediments and mafic oceanic crust accreted to the western edge of North America, producing a series of deep basins and high mountain ranges.
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