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Mélange
In geology, a mélange is a large-scale breccia, a mappable body of rock characterized by a lack of continuous bedding and the inclusion of fragments of rock of all sizes, contained in a fine-grained deformed matrix. The mélange typically consists of a jumble of large blocks of varied lithologies. Both tectonic and sedimentary processes can form mélange. Mélange occurrences are associated with thrust faulted terranes in orogenic belts. A mélange is formed in the accretionary wedge above a subduction zone. The ultramafic ophiolite sequences which have been obducted onto continental crust are typically underlain by a mélange. Smaller-scale localized mélanges may also occur in shear or fault zones, where coherent rock has been disrupted and mixed by shearing forces. Large-scale melanges formed in active continental margin settings generally consist of altered oceanic crustal material and blocks of continental slope sediments in a sheared mudstone matrix. The mixing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Franciscan Complex
The Franciscan Complex or Franciscan Assemblage is a geologic term for a late Mesozoic terrane of heterogeneous rocks found throughout the California Coast Ranges, and particularly on the San Francisco Peninsula. It was named by geologist Andrew Lawson, who also named the San Andreas fault that defines the western extent of the assemblage. The Franciscan Complex is dominated by greywacke sandstones, shales and conglomerates which have experienced low-grade metamorphism. Other important lithologies include chert, basalt, limestone, serpentinite, and high-pressure, low-temperature metabasites (blueschists and eclogites) and meta-limestones. Fossils like radiolaria are found in chert beds of the Franciscan Complex. These fossils have been used to provide age constraints on the different terranes that constitute the Franciscan. The mining opportunities within the Franciscan are restricted to deposits of cinnabar and limestone. The outcrops of the formation have a very large range ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ophiolite
An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks. The Greek word ὄφις, ''ophis'' (''snake'') is found in the name of ophiolites, because of the superficial texture of some of them. Serpentinite especially evokes a snakeskin. The suffix ''lite'' from the Greek ''lithos'' means "stone". Some ophiolites have a green color. The origin of these rocks, present in many mountainous massifs, remained uncertain until the advent of plate tectonic theory. Their great significance relates to their occurrence within mountain belts such as the Alps and the Himalayas, where they document the existence of former ocean basins that have now been consumed by subduction. This insight was one of the founding pillars of plate tectonics, and ophiolites have always played a central role in plate tectonic theory and the interpretation of ancient mountain belts. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thrust Fault
A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. If the angle of the fault plane is lower (often less than 15 degrees from the horizontal) and the displacement of the overlying block is large (often in the kilometer range) the fault is called an ''overthrust'' or ''overthrust fault''. Erosion can remove part of the overlying block, creating a ''fenster'' (or '' window'') – when the underlying block is exposed only in a relatively small area. When erosion removes most of the overlying block, leaving island-like remnants resting on the lower block, the remnants are called ''klippen'' (singular '' klippe''). Blind thrust faults If the fault plane terminates before it reaches the Earth's surface, it is referred to as a ''blind thrust'' fault. Because of the lack of surface evidence, blind ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Accretionary Wedge
An accretionary wedge or accretionary prism forms from sediments accreted onto the non- subducting tectonic plate at a convergent plate boundary. Most of the material in the accretionary wedge consists of marine sediments scraped off from the downgoing slab of oceanic crust, but in some cases the wedge includes the erosional products of volcanic island arcs formed on the overriding plate. An accretionary complex is a current (in modern use) or former accretionary wedge. Accretionary complexes are typically made up of a mix of turbidites of terrestrial material, basalts from the ocean floor, and pelagic and hemipelagic sediments. For example, most of the geological basement of Japan is made up of accretionary complexes. Materials within an accretionary wedge Accretionary wedges and accreted terranes are not equivalent to tectonic plates, but rather are associated with tectonic plates and accrete as a result of tectonic collision. Materials incorporated in accretionary wedges ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Narooma Breccia
Narooma is a town in the Australian state of New South Wales on the far south coast. The town is on the Princes Highway, which crosses the Wagonga Inlet to North Narooma. The heritage town of Central Tilba is nearby to the south. The name Narooma is said to be derived from a word in the local Aboriginal language (one of the Yuin dialects) meaning "clear blue waters". At the , Narooma had an urban population of over 3,000 people. History Before European settlement of the area, the Yuin people inhabited the lands along the stretch of coast, with the Walbunga/Walbunja clan being the traditional owners of the Narooma area. The name Narooma is said to be derived from a word in the local Aboriginal language meaning "clear blue waters". The language of the Walbunja was probably a dialect of Dhurga. There had been an earlier settlement nearby at Punkalla, which was a port for Bodalla and Nerrigundah; a ruined jetty and timber mill can still be seen there. Gold was discov ... [...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] |
Olistostrome
An olistostrome is a sedimentary deposit composed of a chaotic mass of heterogeneous material, such as blocks and mud, known as olistoliths, that accumulates as a semifluid body by submarine gravity sliding or slumping of the unconsolidated sediments. It is a mappable stratigraphic unit which lacks true bedding, but is intercalated amongst normal bedding sequences, as in the Cenozoic basin of central Sicily. The term olistostrome is derived from the Greek ''olistomai'' (to slide) and ''stroma'' (accumulation).Ernesto Abbate, et al., "Olistostromes and olistoliths", ''Sedimentary Geology'', 4 (1970), 521-557. See also *Submarine landslide Submarine landslides are marine landslides that transport sediment across the continental shelf and into the deep ocean. A submarine landslide is initiated when the downwards driving stress (gravity and other factors) exceeds the resisting str ... References Sedimentary rocks {{Geology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plate Tectonics
Plate tectonics (from the la, label= Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large tectonic plates which have been slowly moving since about 3.4 billion years ago. The model builds on the concept of ''continental drift'', an idea developed during the first decades of the 20th century. Plate tectonics came to be generally accepted by geoscientists after seafloor spreading was validated in the mid to late 1960s. Earth's lithosphere, which is the rigid outermost shell of the planet (the crust and upper mantle), is broken into seven or eight major plates (depending on how they are defined) and many minor plates or "platelets". Where the plates meet, their relative motion determines the type of plate boundary: '' convergent'', '' divergent'', or '' transform''. Earthquakes, volcanic activity, mountain-building, and oce ... [...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 themselv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Newfoundland And Labrador
Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region of Labrador, having a total size of 405,212 square kilometres (156,500 sq mi). In 2021, the population of Newfoundland and Labrador was estimated to be 521,758. The island of Newfoundland (and its smaller neighbouring islands) is home to around 94 per cent of the province's population, with more than half residing in the Avalon Peninsula. Labrador borders the province of Quebec, and the French overseas collectivity of Saint Pierre and Miquelon lies about 20 km west of the Burin Peninsula. According to the 2016 census, 97.0 per cent of residents reported English as their native language, making Newfoundland and Labrador Canada's most linguistically homogeneous province. A majority of the population is descended from English and Irish ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bay Of Islands, Newfoundland And Labrador
The Bay of Islands is an extensive inlet located on the west coast of the island of Newfoundland, in Canada. It is a sub-basin of the Gulf of St. Lawrence, consisting of many inlets such as Humber Arm and Goose Arm. The Bay of Islands is bordered on the north and south by North Arm Hills and Blow Me Down mountains, which are part of the Humber Arm Allochthon, which also include the Lewis Hills and the Tablelands. The largest island in the bay is Woods Island (which was formerly inhabited), which is surrounded in most directions by the Long Range Mountains and is directly north of the Lewis Hills. The Way Office was established on July 1, 1883. The first Waymaster was Thomas Carter. Flowing into the Bay of Islands is the Humber River. Draining Deer Lake, the Humber is one of the major rivers on the island of Newfoundland, making the Bay of Islands an important estuary. Near the mouth of the Humber River, appropriately named "Humber Mouth", is the city of Corner Brook (2011 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Matrix (geology)
The matrix or groundmass of a rock is the finer-grained mass of material in which larger grains, crystals, or clasts are embedded. The matrix of an igneous rock consists of finer-grained, often microscopic, crystals in which larger crystals, called phenocrysts, are embedded. This porphyritic texture is indicative of multi-stage cooling of magma. For example, porphyritic andesite will have large phenocrysts of plagioclase in a fine-grained matrix. Also in South Africa, diamonds are often mined from a matrix of weathered clay-like rock ( kimberlite) called "yellow ground". The matrix of sedimentary rocks is finer-grained sedimentary material, such as clay or silt, in which larger grains or clasts are embedded. It is also used to describe the rock material in which a fossil is embedded. Cementation All sediments are at first in an incoherent condition (e.g. sands, clays and gravels, beds of shells), and they may remain in this state for an indefinite period. Millions of ye ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
