|
Great Valley Sequence
The Great Valley Sequence of California is a -thick group of related geologic formations that are Late Jurassic through Cretaceous in age (150–65 Ma) on the geologic time scale. These sedimentary rocks were deposited during the late Mesozoic Era in an ancient seaway that corresponds roughly to the outline of the modern Great Valley (Central Valley) of California. Description Image:Franciscan subduction model.gif, Diagram showing depositional setting of the Great Valley Sequence and coeval Franciscan Assemblage Although the total thickness of the Great Valley Sequence in places is upwards of , most of these rocks today are buried beneath the thick Cenozoic sedimentary fill of the Great Valley of California. A number of gas and oil wells do penetrate these rocks in the subsurface of the valley, and these same rocks also crop out extensively along the west margin of the valley and to a lesser extent along the northern and eastern margins. The sequence overlies the Franciscan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sedimentary
Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation (geology), cementation. Sedimentation is the collective name for processes that cause these particles to settle in place. The particles that form a sedimentary rock are called sediment, and may be composed of detritus (geology), geological detritus (minerals) or detritus, biological detritus (organic matter). The geological detritus originated from weathering and erosion of existing rocks, or from the solidification of molten lava blobs erupted by volcanoes. The geological detritus is transported to the place of deposition by water, wind, ice or Mass wasting, mass movement, which are called agents of denudation. Biological detritus was formed by bodies and parts (mainly shells) of dead aquatic organisms, as well as their fecal mass, suspended in water and slowly piling up on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coeval
{{Short pages monitor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forearc Basin
Forearc is a plate tectonic term referring to a region between an oceanic trench, also known as a subduction zone, and the associated volcanic arc. Forearc regions are present along a convergent margins and eponymously form 'in front of' the volcanic arcs that are characteristic of convergent plate margins. A back-arc region is the companion region behind the volcanic arc. Many forearcs have an accretionary wedge which may form a topographic ridge known as an outer arc ridge that parallels the volcanic arc. Between the accretionary wedge and the volcanic arc a forearc basin, sometimes referred to as an outer arc trough, may be present and can accumulate thick deposits of sediment. Due to tectonic stresses as one tectonic plate rides over another, forearc regions are sources for great thrust earthquakes. Formation During subduction, an oceanic plate is thrust below another tectonic plate, which may be oceanic or continental. Water and other volatiles in the down-going plat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
California Coast Ranges
The Coast Ranges of California span from Del Norte or Humboldt County, California, south to Santa Barbara County. The other three coastal California mountain ranges are the Transverse Ranges, Peninsular Ranges and the Klamath Mountains. Physiographically, they are a section of the larger Pacific Border province, which in turn is part of the larger Pacific Mountain System physiographic division. UNESCO has included the "California Coast Ranges Biosphere Reserve" in its Man and the Biosphere Programme of World Network of Biosphere Reserves since 1983. * Physiography The northern end of the California Coast Ranges overlap the southern end of the Klamath Mountains for approximately 80 miles on the west. They extend southward for more than 600 miles to where the coastline turns eastward along the Santa Barbara Channel, around the area of Point Conception. Here the southern end meets the Los Angeles Transverse Ranges, or ''Sierras de los Angeles''. The rocks themselves that com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
San Joaquin Valley
The San Joaquin Valley ( ; es, Valle de San Joaquín) is the area of the Central Valley of the U.S. state of California that lies south of the Sacramento–San Joaquin River Delta and is drained by the San Joaquin River. It comprises seven counties of Northern and one of Southern California, including, in the north, all of San Joaquin and Kings counties, most of Stanislaus, Merced, and Fresno counties, and parts of Madera and Tulare counties, along with a majority of Kern County, in Southern California. Although the valley is predominantly rural, it has densely populated urban centers: Fresno, Bakersfield, Stockton, Modesto, Tulare, Visalia, Hanford, and Merced. The first European to enter the valley was Pedro Fages in 1772. The San Joaquin Valley was originally inhabited by the Yokuts and Miwok peoples. The Tejon Indian Tribe of California is a federally recognized tribe of Kitanemuk, Yokuts, and Chumash indigenous people of California. Their ancestral homeland ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sacramento Valley
, photo =Sacramento Riverfront.jpg , photo_caption= Sacramento , map_image=Map california central valley.jpg , map_caption= The Central Valley of California , location = California, United States , coordinates = , boundaries = Sierra Nevada (east), Cascade Range, Klamath Mountains (north), Coast Range (west), Sacramento–San Joaquin River Delta (south) , towns = Redding, Chico, Yuba City, Sacramento , watercourses = Sacramento River The Sacramento Valley is the area of the Central Valley of the U.S. state of California that lies north of the Sacramento–San Joaquin River Delta and is drained by the Sacramento River. It encompasses all or parts of ten Northern California counties. Although many areas of the Sacramento Valley are rural, it contains several urban areas, including the state capital, Sacramento. Since 2010, statewide droughts in California have further strained both the Sacramento Valley's and the Sacramento metropolitan region's water security. Geog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mudflows
A mudflow or mud flow is a form of mass wasting involving fast-moving flow of debris that has become liquified by the addition of water. Such flows can move at speeds ranging from 3 meters/minute to 5 meters/second. Mudflows contain a significant proportion of clay, which makes them more fluid than debris flows, allowing them to travel farther and across lower slope angles. Both types of flow are generally mixtures of particles with a wide range of sizes, which typically become sorted by size upon deposition. Mudflows are often called mudslides, a term applied indiscriminately by the mass media to a variety of mass wasting events. Mudflows often start as slides, becoming flows as water is entrained along the flow path; such events are often called flow slides. Other types of mudflows include lahars (involving fine-grained pyroclastic deposits on the flanks of volcanoes) and jökulhlaups (outbursts from under glaciers or icecaps). A statutory definition of "flood-related mudsli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sediment Gravity Flow
upright=1.25, This turbidite from the Devonian Becke-Oese Sandstone">Devonian.html" ;"title="turbidite from the Devonian">turbidite from the Devonian Becke-Oese Sandstone of Germany is an example of a deposit from a sediment gravity flow. Note the complete Bouma sequence. A sediment gravity flow is one of several types of sediment transport mechanisms, of which most geologists recognize four principal processes. These flows are differentiated by their dominant sediment support mechanisms, which can be difficult to distinguish as flows can be in transition from one type to the next as they evolve downslope. Sediment support mechanisms Sediment gravity flows are represented by four different mechanisms of keeping grains within the flow in suspension. * Grain flow – Grains in the flow are kept in suspension by grain-to-grain interactions, with the fluid acting only as a lubricant. As such, the grain-to-grain collisions generate a dispersive pressure that helps prevent grains from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Turbidites
A turbidite is the geologic deposit of a turbidity current, which is a type of amalgamation of fluidal and sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean. Sequencing Turbidites were first properly described by Arnold H. Bouma (1962), who studied deepwater sediments and recognized particular "fining-up intervals" within deep water, fine-grained shales, which were anomalous because they started at pebble conglomerates and terminated in shales. This was anomalous because within the deep ocean it had historically been assumed that there was no mechanism by which tractional flow could carry and deposit coarse-grained sediments into the abyssal depths. Bouma cycles begin with an erosional contact of a coarse lower bed of pebble to granule conglomerate in a sandy matrix, and grade up through coarse then medium plane parallel sandstone; through cross-bedded sandstone; rippled cross-bedded sand/silty sand, and finally lamina ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Submarine Canyons
A submarine canyon is a steep-sided valley cut into the seabed of the continental slope, sometimes extending well onto the continental shelf, having nearly vertical walls, and occasionally having canyon wall heights of up to 5 km, from canyon floor to canyon rim, as with the Great Bahama Canyon. Just as above-sea-level canyons serve as channels for the flow of water across land, submarine canyons serve as channels for the flow of turbidity currents across the seafloor. Turbidity currents are flows of dense, sediment laden waters that are supplied by rivers, or generated on the seabed by storms, submarine landslides, earthquakes, and other soil disturbances. Turbidity currents travel down slope at great speed (as much as 70 km/h), eroding the continental slope and finally depositing sediment onto the abyssal plain, where the particles settle out.Continental Margin Sedimentation: From Sediment Transport to Sequence Stratigraphy (Special Publication 37 of the IAS) M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Submarine Fan
Abyssal fans, also known as deep-sea fans, underwater deltas, and submarine fans, are underwater geological structures associated with large-scale sediment deposition and formed by turbidity currents. They can be thought of as an underwater version of alluvial fans and can vary dramatically in size, with widths from several kilometres to several thousands of kilometres The largest is the Bengal Fan, followed by the Indus Fan, but major fans are also found at the outlet of the Amazon, Congo, Mississippi and elsewhere. Formation Abyssal (or submarine) fans are formed from turbidity currents. These currents begin when a geologic activity pushes sediments over the edge of a continental shelf and down the continental slope, creating an underwater landslide. A dense slurry of muds and sands speeds towards the foot of the slope, until the current slows. The decreasing current, having a reduced ability to transport sediments, deposits the grains it carries, thus creating a su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sierra Nevada (U
The Sierra Nevada () is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primarily in Nevada. The Sierra Nevada is part of the American Cordillera, an almost continuous chain of mountain ranges that forms the western "backbone" of the Americas. The Sierra runs north-south and its width ranges from to across east–west. Notable features include General Sherman, the largest tree in the world by volume; Lake Tahoe, the largest alpine lake in North America; Mount Whitney at , the highest point in the contiguous United States; and Yosemite Valley sculpted by glaciers from one-hundred-million-year-old granite, containing high waterfalls. The Sierra is home to three national parks, twenty wilderness areas, and two national monuments. These areas include Yosemite, Sequoia, and Kings Canyon National Parks; and Devils ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
