Type locality and description
The type locality of the Espada Formation is in Hondo Canyon, near Point Arguello, as first described by Thomas Dibblee in his 1950 book on the geology of southwestern Santa Barbara County. [4] While the unit is 1200 meters (4,000 feet) thick at the type locality, it is much thicker elsewhere; along the southern slope of the San Rafael Mountains it is exposed from its base to its top, where it is probably in conformable contact with the Jalama Formation, and the total thickness is around 5300 meters (16,000 feet) – 5 kilometers (three miles) of uninterrupted sedimentary deposition that took place over 50 million years. [3] [5]
The formation throughout its geographic range consists of layer upon layer of well-bedded argillaceous silty to sandy shales, with smaller interbeds of arkosic sandstone. The shales are generally brown with a greenish tinge in fresh, unweathered exposures; upon weathering they develop a variety of colors. [3] [6] A few beds of pebble conglomerates and limestone, dark gray and not pure, are also found, but the shales are predominant throughout, accounting for around 90 percent of the entire unit. [3] [7] In general, the sandstone layers become more common towards the top of the stratigraphic column, and the largest conglomerate bed is in the highest part of the Espada, exposed north of the Santa Ynez River near its junction with Mono Canyon. The sandstones are composed of grains which are similar mineralogically to the underlying Franciscan Formation. [3]
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.
Rainbow Basin is a geological formation in the Calico Peaks range, located approximately 8 miles (13 km) north of Barstow in the Mojave Desert in San Bernardino County, California.
The San Juan Basin is a geologic structural basin located near the Four Corners region of the Southwestern United States. The basin covers 7,500 square miles and resides in northwestern New Mexico, southwestern Colorado, and parts of Utah and Arizona. Specifically, the basin occupies space in the San Juan, Rio Arriba, Sandoval, and McKinley counties in New Mexico, and La Plata and Archuleta counties in Colorado. The basin extends roughly 100 miles (160 km) N-S and 90 miles (140 km) E-W.
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 connect to Moorpark and Ventura, California. 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 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 Coldwater Sandstone 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 arkosic sandstone 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.
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 Bass Formation, also known as the Bass Limestone, is a Mesoproterozoic rock formation that outcrops in the eastern Grand Canyon, Coconino County, Arizona. The Bass Formation erodes as either cliffs or stair-stepped cliffs. In the case of the stair-stepped topography, resistant dolomite layers form risers and argillite layers form steep treads. In general, the Bass Formation in the Grand Canyon region and associated strata of the Unkar Group-rocks dip northeast (10°–30°) toward normal faults that dip 60+° toward the southwest. This can be seen at the Palisades fault in the eastern part of the main Unkar Group outcrop area. In addition, thick, prominent, and dark-colored basaltic sills intrude across the Bass Formation.
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 geology of Bosnia & Herzegovina is the study of rocks, minerals, water, landforms and geologic history in the country. The oldest rocks exposed at or near the surface date to the Paleozoic and the Precambrian geologic history of the region remains poorly understood. Complex assemblages of flysch, ophiolite, mélange and igneous plutons together with thick sedimentary units are a defining characteristic of the Dinaric Alps, also known as the Dinaride Mountains, which dominate much of the country's landscape.
The geology of Utah includes rocks formed at the edge of the proto-North American continent during the Precambrian. A shallow marine sedimentary environment covered the region for much of the Paleozoic and Mesozoic, followed by dryland conditions, volcanism and the formation of the basin and range terrain in the Cenozoic. Utah is a state in the western United States.
The geology of Montana includes thick sequences of Paleozoic, Mesozoic and Cenozoic sedimentary rocks overlying ancient Archean and Proterozoic crystalline basement rock. Eastern Montana has considerable oil and gas resources, while the uplifted Rocky Mountains in the west, which resulted from the Laramide orogeny and other tectonic events have locations with metal ore.
The geology of Uzbekistan consists of two microcontinents and the remnants of oceanic crust, which fused together into a tectonically complex but resource rich land mass during the Paleozoic, before becoming draped in thick, primarily marine sedimentary units.
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.
