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Lewis Overthrust
The Lewis Overthrust is a geologic thrust fault structure of the Rocky Mountains found within the bordering national parks of Glacier in Montana, United States and Waterton Lakes in Alberta, Canada. The structure was created due to the collision of tectonic plates about 170 million years ago that drove a several mile thick wedge of rock eastwards, causing it to overlie softer Cretaceous age rock that is 400 to 500 million years younger. Geography The Canadian Rocky Mountain foreland thrust and fold belt is a northeastward tapering deformational belt consisting of Mesoproterozoic, Paleozoic, and Mesozoic strata. The Lewis thrust sheet is one of the major structures of the foreland thrust and fold belt extending over from Mount Kidd near Calgary, AB in the Southeast Canadian Cordillera to Steamboat Mountain, located west of Great Falls, Northwest Montana in the United States. The Lewis overthrust provides scientific insight into geologic processes happening in other parts of t ... [...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 thr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allochthon
upright=1.6, Schematic overview of a thrust system. The hanging wall block is (when it has reasonable proportions) called a nappe. If an erosional hole is created in the nappe that is called a window (geology)">window. A klippe is a solitary outcrop of the nappe in the middle of autochthonous material. An allochthon, or an allochthonous block, is a large block of rock which has been moved from its original site of formation, usually by low angle thrust faulting. An allochthon which is isolated from the rock that pushed it into position is called a klippe. If an allochthon has a "hole" in it so that one can view the autochthon (geology), autochthon beneath the allochthon, the hole is called a "window" (or Fenster). Etymology: Greek; 'allo' = other, and 'chthon' = earth. In generalized terms, the term is applied to any geologic units that originated at a distance from their present location For comparison, see also Autochthon. In the United States there are three notable al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Miogeocline
A miogeocline is an area of sedimentation which occurs along the passive margin of a continent. The deposits occur as typically shallow water clastic sediments which thicken seaward to form a clastic wedge parallel to a tectonically quiescent coast. Modern examples include the continental shelf of the northern Gulf of Mexico and the Atlantic coast of North and South America. The term was coined in 1966 by Dietz and Holden from the ''miogeosyncline'' concept of the outdated geosynclinal theory. Dietz and Holden modified the term to miogeocline as the sedimentary deposits described were not synclinal in form.Dietz, Robert S. and John C. Holden, 1966, ''Miogeoclines (Miogeosynclines) in Space and Time,'' Journal of Geology, Vol. 74, No. 5, Part 1 (Sep., 1966), pp. 566-583 Ancient miogeoclines such as the Neoproterozoic to Cambrian Cordilleran miogeocline of the southwestern U. S.,Stewart, J. H. and F. G. Poole, ''Lower Paleozoic and Uppermost Precambrian Cordilleran Miogeocline, Gr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transpression
In geology, transpression is a type of strike-slip deformation that deviates from simple shear because of a simultaneous component of shortening perpendicular to the fault plane. This movement ends up resulting in oblique shear. It is generally very unlikely that a deforming body will experience "pure" shortening or "pure" strike-slip. The relative amounts of shortening and strike-slip can be expressed in the convergence angle alpha which ranges from zero (ideal strike-slip) to 90 degrees (ideal convergence). During shortening, unless material is lost, transpression produces vertical thickening in the crust. Transpression that occurs on a regional scale along plate boundaries is characterized by oblique convergence. More locally, transpression occurs within restraining bends in strike-slip fault zones. Transpressional structures Transpressional shear zones are characterized by an association of structures that suggest zone-normal shortening and zone-parallel shearing. Commonly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Canadian Rockies
The Canadian Rockies (french: Rocheuses canadiennes) or Canadian Rocky Mountains, comprising both the Alberta Rockies and the British Columbian Rockies, is the Canadian segment of the North American Rocky Mountains. It is the easternmost part of the Canadian Cordillera, which is the northern segment of the North American Cordillera, the expansive system of interconnected mountain ranges between the Interior Plains and the Pacific Coast that runs northwest–southeast from central Alaska to the Isthmus of Tehuantepec in Mexico. Canada officially defines the Rocky Mountains system as the mountain chains east of the Rocky Mountain Trench extending from the Liard River valley in northern British Columbia to the Albuquerque Basin in New Mexico, not including the Mackenzie, Richardson and British Mountains/Brooks Range in Yukon and Alaska (which are all included as the "Arctic Rockies" in the United States' definition of the Rocky Mountains system). The Canadian Rockies, bein ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laramide Orogeny
The Laramide orogeny was a time period of mountain building in western North America, which started in the Late Cretaceous, 70 to 80 million years ago, and ended 35 to 55 million years ago. The exact duration and ages of beginning and end of the orogeny are in dispute. The Laramide orogeny occurred in a series of pulses, with quiescent phases intervening. The major feature that was created by this orogeny was deep-seated, thick-skinned deformation, with evidence of this orogeny found from Canada to northern Mexico, with the easternmost extent of the mountain-building represented by the Black Hills of South Dakota. The phenomenon is named for the Laramie Mountains of eastern Wyoming. The Laramide orogeny is sometimes confused with the Sevier orogeny, which partially overlapped in time and space. The orogeny is commonly attributed to events off the west coast of North America, where the Kula Plate, Kula and Farallon Plates were sliding under the North American plate. Most hypothes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intermontane Belt
The Intermontane Belt is a physiogeological region in the Pacific Northwest of North America, stretching from northern Washington into British Columbia, Yukon, and Alaska. It comprises rolling hills, high plateaus and deeply cut valleys. The rocks in the belt have very little similarities with the North American continent. Geology The formation of the Intermontane Belt is complex. It began forming during the early Jurassic period when an island arc called the Intermontane Islands collided against a pre-existing continental margin. This island arc is believed to have formed on a pre-existing tectonic plate called the Intermontane Plate about 245 million years ago by subduction of the former Insular Plate during the Triassic period. This subduction zone records another subduction zone called the Intermontane Trench under an ancient ocean between the Intermontane Islands and the former continental margin of North America called the Slide Mountain Ocean. This arrangement of two par ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Purcell Mountains
The Purcell Mountains are a mountain range in southeastern British Columbia, Canada. They are a subrange of the Columbia Mountains, which includes the Selkirk, Monashee, and Cariboo Mountains. They are located on the west side of the Rocky Mountain Trench in the area of the Columbia Valley, and on the east side of the valley of Kootenay Lake and the Duncan River. The only large settlements in the mountains are the Panorama Ski Resort and Kicking Horse Resort, adjacent to the Columbia Valley towns of Invermere and Golden, though there are small settlements, such as Yahk and Moyie along the Crowsnest Highway, and residential rural areas dependent on the cities of Creston, Kimberley and Cranbrook, which are located adjacent to the range. The Purcells are shown on some United States maps as the Percell Mountains, where their southern limit protrudes into the states of Idaho and Montana, abutting Lake Koocanusa, a reservoir on the Kootenai River. American geographic classification ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rocky Mountain Trench
The Rocky Mountain Trench, also known as the Valley of a Thousand Peaks or simply the Trench, is a large valley on the western side of the northern part of North America's Rocky Mountains. The Trench is both visually and cartographically a striking physiographic feature extending approximately from Flathead Lake, Montana, to the Liard River, just south of the British Columbia–Yukon border near Watson Lake, Yukon. The trench bottom is wide and is above sea level. The general orientation of the Trench is an almost straight 150/330° geographic north vector and has become convenient as a visual guide for aviators heading north or south. Although some of its topography has been carved into U-shaped glacial valleys, it is primarily a byproduct of geologic faulting. The Trench separates the Rocky Mountains on its east from the Columbia Mountains and the Cassiar Mountains on its west. It also skirts part of the McGregor Plateau area of the Nechako Plateau sub-area of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Décollement
Décollement () is a gliding plane between two rock masses, also known as a basal detachment fault. Décollements are a deformational structure, resulting in independent styles of deformation in the rocks above and below the fault. They are associated with both compressional settings (involving folding and overthrusting) and extensional settings. Origin The term was first used by geologists studying the structure of the Swiss Jura Mountains, coined in 1907 by A. Buxtorf, who released a paper that theorized that the Jura is the frontal part of a décollement at the base of a nappe, rooted in the faraway Swiss Alps. Marcel Alexandre Bertrand published a paper in 1884 that dealt with Alpine nappism. Thin-skinned tectonics was implied in that paper but the actual term was not used until Buxtorf's 1907 publication. Formation Décollements are caused by surface forces, which 'push' at converging plate boundaries, facilitated by body forces (gravity sliding). Mechanically wea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strike And Dip
Strike and dip is a measurement convention used to describe the orientation, or attitude, of a planar geologic feature. A feature's strike is the azimuth of an imagined horizontal line across the plane, and its dip is the angle of inclination measured downward from horizontal. They are used together to measure and document a structure's characteristics for study or for use on a geologic map. A feature's orientation can also be represented by dip and dip direction, using the azimuth of the dip rather than the strike value. Linear features are similarly measured with trend and plunge, where "trend" is analogous to dip direction and "plunge" is the dip angle. Strike and dip are measured using a compass and a clinometer. A compass is used to measure the feature's strike by holding the compass horizontally against the feature. A clinometer measures the features dip by recording the inclination perpendicular to the strike. These can be done separately, or together using a tool such a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
