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Transtension
Transtension is the state in which a rock mass or area of the Earth's crust experiences both ''extensive'' and ''transtensive'' shear. As such, transtensional regions are characterised by both extensional structures ( normal faults, grabens) and wrench structures (strike-slip faults). In general, many tectonic regimes that were previously defined as simple strike-slip shear zones are actually transtensional. It is unlikely that a deforming body will experience 'pure' extension or 'pure' strike-slip. Transtensional shear zones are characterized by the co-existence of different structures, related to both strike-slip shear and extension. End member structures include pure strike-slip faults and purely extensional ("normal") dip-slip faults. Faults which have components of both (termed 'oblique' slip faults) are abundant. Releasing bend ''Releasing bends'' are transtensional structures that form where the orientation of a strike-slip fault becomes oblique to the regional slip vector ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pull-apart Basin
In geology, a basin is a region where subsidence generates accommodation space for the deposition of sediments. A pull-apart basin is a structural basin where two overlapping (en echelon) strike-slip faults or a fault bend creates an area of crustal extension undergoing tension, which causes the basin to sink down. Frequently, the basins are rhombic or sigmoidal in shape. Dimensionally, basins are limited to the distance between the faults and the length of overlap.Frisch, Wolfgang, Martin Meschede, and Ronald C. Blakey. ''Plate tectonics: Continental drift and mountain building''. Springer, 2010. Pull-apart basins are also referred to as overlapping-tension-zones (OTZ). Mechanics and fault configuration The inhomogeneity and structural complexity of continental crust causes faults to deviate from a straight course and frequently causes bends or step-overs in fault paths. Bends and step-overs of adjacent faults become favorable locations for extensional and compressional str ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pull-apart Basin
In geology, a basin is a region where subsidence generates accommodation space for the deposition of sediments. A pull-apart basin is a structural basin where two overlapping (en echelon) strike-slip faults or a fault bend creates an area of crustal extension undergoing tension, which causes the basin to sink down. Frequently, the basins are rhombic or sigmoidal in shape. Dimensionally, basins are limited to the distance between the faults and the length of overlap.Frisch, Wolfgang, Martin Meschede, and Ronald C. Blakey. ''Plate tectonics: Continental drift and mountain building''. Springer, 2010. Pull-apart basins are also referred to as overlapping-tension-zones (OTZ). Mechanics and fault configuration The inhomogeneity and structural complexity of continental crust causes faults to deviate from a straight course and frequently causes bends or step-overs in fault paths. Bends and step-overs of adjacent faults become favorable locations for extensional and compressional str ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strike-slip Tectonics
Strike-slip tectonics or wrench tectonics is the type of tectonics that is dominated by lateral (horizontal) movements within the Earth's crust (and lithosphere). Where a zone of strike-slip tectonics forms the boundary between two tectonic plates, this is known as a transform or conservative plate boundary. Areas of strike-slip tectonics are characterised by particular deformation styles including: ''stepovers'', ''Riedel shears'', ''flower structures'' and ''strike-slip duplexes''. Where the displacement along a zone of strike-slip deviates from parallelism with the zone itself, the style becomes either transpressional or transtensional depending on the sense of deviation. Strike-slip tectonics is characteristic of several geological environments, including oceanic and continental transform faults, zones of oblique collision and the deforming foreland of zones of continental collision. Deformation styles Stepovers When strike-slip fault zones develop, they typically form as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shear (geology)
Boudinaged quartz vein (with strain fringe) showing ''Fault (geology)">sinistral shear sense'', Starlight Pit, Fortnum Gold Mine, Western Australia In geology, shear is the response of a rock to deformation usually by compressive stress and forms particular textures. Shear can be homogeneous or non-homogeneous, and may be pure shear or simple shear. Study of geological shear is related to the study of structural geology, rock microstructure or rock texture and fault mechanics. The process of shearing occurs within brittle, brittle-ductile, and ductile rocks. Within purely brittle rocks, compressive stress results in fracturing and simple faulting. Rocks Rocks typical of shear zones include mylonite, cataclasite, S-tectonite and L-tectonite, pseudotachylite, certain breccias and highly foliated versions of the wall rocks. Shear zone A shear zone is a tabular to sheetlike, planar or curviplanar zone composed of rocks that are more highly strained than rocks adjacent to ... [...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] |
Fault (geology)
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic forces, with the largest forming the boundaries between the plates, such as the megathrust faults of subduction zones or transform faults. Energy release associated with rapid movement on active faults is the cause of most earthquakes. Faults may also displace slowly, by aseismic creep. A ''fault plane'' is the plane that represents the fracture surface of a fault. A ''fault trace'' or ''fault line'' is a place where the fault can be seen or mapped on the surface. A fault trace is also the line commonly plotted on geologic maps to represent a fault. A ''fault zone'' is a cluster of parallel faults. However, the term is also used for the zone of crushed rock along a single fault. Prolonged motion along closely spaced faults can blur the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strike-slip Fault
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic forces, with the largest forming the boundaries between the plates, such as the megathrust faults of subduction zones or transform faults. Energy release associated with rapid movement on active faults is the cause of most earthquakes. Faults may also displace slowly, by aseismic creep. A ''fault plane'' is the plane that represents the fracture surface of a fault. A ''fault trace'' or ''fault line'' is a place where the fault can be seen or mapped on the surface. A fault trace is also the line commonly plotted on geologic maps to represent a fault. A ''fault zone'' is a cluster of parallel faults. However, the term is also used for the zone of crushed rock along a single fault. Prolonged motion along closely spaced faults can blur the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dip-slip Fault
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic forces, with the largest forming the boundaries between the plates, such as the megathrust faults of subduction zones or transform faults. Energy release associated with rapid movement on active faults is the cause of most earthquakes. Faults may also displace slowly, by aseismic creep. A ''fault plane'' is the plane that represents the fracture surface of a fault. A ''fault trace'' or ''fault line'' is a place where the fault can be seen or mapped on the surface. A fault trace is also the line commonly plotted on geologic maps to represent a fault. A ''fault zone'' is a cluster of parallel faults. However, the term is also used for the zone of crushed rock along a single fault. Prolonged motion along closely spaced faults can blur the d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leigh Royden
Leigh "Wiki" H. Royden is an American Geologist. Early life Royden was born in Palo Alto, California. Royden's father was Halsey Royden, a mathematician. Education Royden received an A.B. degree in physics from Harvard University and a PhD in geology and geophysics from the Massachusetts Institute of Technology (MIT). Career Royden became a member of the faculty at MIT in 1988. She is director of MIT's Experimental Study Group. Royden has published important papers on thermal subsidence at the northeastern continental margin of North America and on retreating subduction boundaries formed during the collision of continental tectonic plates. In 1990, she was awarded the Donath Medal (Young Scientist Award) by the Geological Society of America. Royden was named a fellow of the American Geophysical Union in 2004. In 2011, she received the George P. Woollard Award. In 2013, she was awarded the by the European Geosciences Union. In 2018, she was named to the American Academy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Structural Geology
Structural geology is the study of the three-dimensional distribution of rock units with respect to their deformational histories. The primary goal of structural geology is to use measurements of present-day rock geometries to uncover information about the history of deformation (strain) in the rocks, and ultimately, to understand the stress field that resulted in the observed strain and geometries. This understanding of the dynamics of the stress field can be linked to important events in the geologic past; a common goal is to understand the structural evolution of a particular area with respect to regionally widespread patterns of rock deformation (e.g., mountain building, rifting) due to plate tectonics. Use and importance The study of geologic structures has been of prime importance in economic geology, both petroleum geology and mining geology. Folded and faulted rock strata commonly form traps that accumulate and concentrate fluids such as petroleum and natural gas. Simil ... [...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 the poi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet, dwarf planet, or natural satellite. It is usually distinguished from the underlying mantle by its chemical makeup; however, in the case of icy satellites, it may be distinguished based on its phase (solid crust vs. liquid mantle). The crusts of Earth, Mercury, Venus, Mars, Io, the Moon and other planetary bodies formed via igneous processes and were later modified by erosion, impact cratering, volcanism, and sedimentation. Most terrestrial planets have fairly uniform crusts. Earth, however, has two distinct types: continental crust and oceanic crust. These two types have different chemical compositions and physical properties and were formed by different geological processes. Types of crust Planetary geologists divide crust into three categories based on how and when it formed. Primary crust / primordial crust This is a planet's "original" crust. It forms from solidification of a magma ocean. Towa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
