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Tobífera Formation
Tobífera Formation ( es, Formación Tobífera) is a volcano-sedimentary formation of Middle to Late Jurassic age. The formation is crops out in the Magallanes Region in southern Patagonia and Tierra del Fuego of Chile, the Santa Cruz Province of southern Argentina, and in the subsurface of the Malvinas Basin offshore Argentina and the Falkland Islands. Description The bulk of the formation originates from silicic pyroclastic material during a period of bimodal volcanism in Rocas Verdes Basin, a rift basin.Fildani, Andrea, Romans, B.W., Fosdick, J.C., Crane, W.H., and Hubbard, S.M. (2008)Orogenesis of the Patagonian Andes as reflected by basin evolution in southernmost South America in Spencer, J.E., and Titley, S.R., eds., Ores and orogenesis: Circum-Pacific tectonics, geologic evolution, and ore deposits: ''Arizona Geological Society Digest'' 22: 259-268. The Tobífera Formation is grouped together with other formations of similar age in Patagonia in the Chon Aike Province ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geological Formation
A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exposed in a geographical region (the stratigraphic column). It is the fundamental unit of lithostratigraphy, the study of strata or rock layers. A formation must be large enough that it can be mapped at the surface or traced in the subsurface. Formations are otherwise not defined by the thickness (geology), thickness of their rock strata, which can vary widely. They are usually, but not universally, tabular in form. They may consist of a single lithology (rock type), or of alternating beds of two or more lithologies, or even a heterogeneous mixture of lithologies, so long as this distinguishes them from adjacent bodies of rock. The concept of a geologic formation goes back to the beginnings of modern scientific geology. The term was used by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cordillera Darwin Metamorphic Complex
The Cordillera Darwin Metamorphic Complex is a geologic complex composed chiefly of metamorphic rocks located in southern Tierra del Fuego. It has been suggested that the Cordillera Darwin Metamorphic Complex is analogous to the Eastern Andes Metamorphic Complex. The Cordillera Darwin Metamorphic Complex is the only metamorphic complex in the southern Andes known to have amphibolite facies rocks containing kyanite and sillimanite which evidences high-grade metamorphism. High-grade metamorphism took place during the Cretaceous purportedly in association with the closure of the Rocas Verdes Basin. The protoliths of Cordillera Darwin Metamorphic Complex are unrelated to Tierra del Fuego Igneous and Metamorphic Complex Tierra del Fuego Igneous and Metamorphic Complex is a geological basement complex known from boreholes in northern Tierra del Fuego. The complex is made up of foliated igneous rocks of Cambrian age including orthogneiss. It underlies unconformab ... despite present ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sedimentary Basin
Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock. They form when long-term subsidence creates a regional depression that provides accommodation space for accumulation of sediments. Over millions or tens or hundreds of millions of years the deposition of sediment, primarily gravity-driven transportation of water-borne eroded material, acts to fill the depression. As the sediments are buried, they are subject to increasing pressure and begin the processes of compaction and lithification that transform them into sedimentary rock. Sedimentary basins are created by deformation of Earth's lithosphere in diverse geological settings, usually as a result of plate tectonic activity. Mechanisms of crustal deformation that lead to subsidence and sedimentary basin formation include the thinning of underlying crust; depression of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rift
In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-graben with normal faulting and rift-flank uplifts mainly on one side. Where rifts remain above sea level they form a rift valley, which may be filled by water forming a rift lake. The axis of the rift area may contain volcanic rocks, and active volcanism is a part of many, but not all, active rift systems. Major rifts occur along the central axis of most mid-ocean ridges, where new oceanic crust and lithosphere is created along a divergent boundary between two tectonic plates. ''Failed rifts'' are the result of continental rifting that failed to continue to the point of break-up. Typically the transition from rifting to spreading develops at a triple junction where three converging rifts meet over a hotspot. Two of these evolve to t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bimodal Volcanism
Bimodal volcanism is the eruption of both mafic and felsic lavas from a single volcanic centre with little or no lavas of intermediate composition. This type of volcanism is normally associated with areas of extensional tectonics, particularly rifts. Occurrence Most occurrences of bimodal volcanism are associated with thinning of the crust and the presence of such rocks in metamorphic sequences has been used to provide evidence for past rifting events. Most examples come from areas of active continental rifting such as the Basin and Range Province. Bimodal volcanism has also been described from areas of transtension, the early phases of back-arc basin formation and in the products of both continental and oceanic hotspots (e.g. Yellowstone, Anahim and the Canary Islands). Mechanism of formation Bimodal volcanism is normally explained as a result of partial melting of the crust, creating granitic magma Magma () is the molten or semi-molten natural material from which all ign ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyroclast
Tephra is fragmental material produced by a volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, they remain as tephra unless hot enough to fuse into pyroclastic rock or tuff. Tephrochronology is a geochronological technique that uses discrete layers of tephra—volcanic ash from a single eruption—to create a chronological framework in which paleoenvironmental or archaeological records can be placed. When a volcano explodes, it releases a variety of tephra including ash, cinders, and blocks. These layers settle on the land and, over time, sedimentation occurs incorporating these tephra layers into the geologic record. Often, when a volcano explodes, biological organisms are killed and their remains are buried within the tephra layer. These fossils are later dated by scientists to determine the age of the fossil and its place within the geol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Felsic
In geology, felsic is a modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted with mafic rocks, which are relatively richer in magnesium and iron. Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. Felsic magma or lava is higher in viscosity than mafic magma/lava. Felsic rocks are usually light in color and have specific gravities less than 3. The most common felsic rock is granite. Common felsic minerals include quartz, muscovite, orthoclase, and the sodium-rich plagioclase feldspars (albite-rich). Terminology In modern usage, the term ''acid rock'', although sometimes used as a synonym, normally now refers specifically to a high-silica-content (greater than 63% SiO2 by weight) volcanic rock, such as rhyolite. Older, broader usage ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Falkland Islands
The Falkland Islands (; es, Islas Malvinas, link=no ) is an archipelago in the South Atlantic Ocean on the Patagonian Shelf. The principal islands are about east of South America's southern Patagonian coast and about from Cape Dubouzet at the northern tip of the Antarctic Peninsula, at a latitude of about 52°S. The archipelago, with an area of , comprises East Falkland, West Falkland, and 776 smaller islands. As a British overseas territory, the Falklands have internal self-governance __NOTOC__ Self-governance, self-government, or self-rule is the ability of a person or group to exercise all necessary functions of regulation without intervention from an external authority. It may refer to personal conduct or to any form of ..., but the United Kingdom takes responsibility for their defence and foreign affairs. The capital and largest settlement is Stanley, Falkland Islands, Stanley on East Falkland. Controversy exists over the Falklands' discovery and sub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tierra Del Fuego
Tierra del Fuego (, ; Spanish for "Land of the Fire", rarely also Fireland in English) is an archipelago off the southernmost tip of the South American mainland, across the Strait of Magellan. The archipelago consists of the main island, Isla Grande de Tierra del Fuego, with an area of , and a group of many islands, including Cape Horn and Diego Ramírez Islands. Tierra del Fuego is divided between Chile and Argentina, with the latter controlling the eastern half of the main island and the former the western half plus the islands south of Beagle Channel and the southernmost islands. The southernmost extent of the archipelago is just north of latitude 56°S. The earliest known human settlement in Tierra del Fuego dates to approximately 8,000 BC. Europeans first explored the islands during Ferdinand Magellan's expedition of 1520. ''Tierra del Fuego'' and similar namings stem from sightings of the many bonfires that the natives built. Settlement by those of European descent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Patagonia
Patagonia () refers to a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and glaciers in the west and deserts, tablelands and steppes to the east. Patagonia is bounded by the Pacific Ocean on the west, the Atlantic Ocean to the east, and many bodies of water that connect them, such as the Strait of Magellan, the Beagle Channel, and the Drake Passage to the south. The Colorado and Barrancas rivers, which run from the Andes to the Atlantic, are commonly considered the northern limit of Argentine Patagonia. The archipelago of Tierra del Fuego is sometimes included as part of Patagonia. Most geographers and historians locate the northern limit of Chilean Patagonia at Huincul Fault, in Araucanía Region.Manuel Enrique Schilling; Richard WalterCarlson; AndrésTassara; Rommulo Vieira Conceição; Gustavo Walter B ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magallanes Region
The Magallanes Region (), officially the Magallanes y la Antártica Chilena Region ( es, Región de Magallanes y de la Antártica Chilena), is one of Chile's 16 first order administrative divisions. It is the southernmost, largest, and second least populated region of Chile. It comprises four provinces: Última Esperanza, Magallanes, Tierra del Fuego, and Antártica Chilena. Magallanes's geographical features include Torres del Paine, Cape Horn, Tierra del Fuego island, and the Strait of Magellan. It also includes the Antarctic territory claimed by Chile. Despite its large area, much of the land in the region is rugged or closed off for sheep farming, and is unsuitable for settlement. 80% of the population lives in the capital Punta Arenas, a major market city and one of the main hubs for Antarctic exploration. The main economic activities are sheep farming, oil extraction, and tourism. It is also the region with the lowest poverty level in Chile (5.8%); households in Maga ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sedimentary Formation
A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exposed in a geographical region (the stratigraphic column). It is the fundamental unit of lithostratigraphy, the study of strata or rock layers. A formation must be large enough that it can be mapped at the surface or traced in the subsurface. Formations are otherwise not defined by the thickness of their rock strata, which can vary widely. They are usually, but not universally, tabular in form. They may consist of a single lithology (rock type), or of alternating beds of two or more lithologies, or even a heterogeneous mixture of lithologies, so long as this distinguishes them from adjacent bodies of rock. The concept of a geologic formation goes back to the beginnings of modern scientific geology. The term was used by Abraham Gottlob Werne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
