Fault (geology)

About: Fault (geology) is a research topic. Over the lifetime, 26732 publications have been published within this topic receiving 744535 citations.

Tectonics of strike-slip restraining and releasing bends

Abstract: Restraining and releasing bends are common, but enigmatic features of strike-slip fault systems occurring in all crustal environments and at regional to microscopic scales of observation. Regional-scale restraining bends are sites of mountain building, transpressional deformation and basement exhumation, whereas releasing bends are sites of topographic subsidence, transtensional deformation, basin sedimentation and possible volcanism and economic mineralization. Because restraining and releasing bends often occur as singular self-contained domains of complex deformation, they are appealing natural laboratories for Earth scientists to study fault processes, earthquake seismology, active faulting and sedimentation, fault and fluid-flow relationships, links between tectonics and topography, tectonic and erosional controls on exhumation, and tectonic geomorphology. This volume addresses the tectonic complexity and diversity of strike-slip restraining and releasing bends with 18 contributions divided into four thematic sections: (1) a topical review of fault bends and their global distribution; (2) bends, sedimentary basins and earthquake hazards; (3) restraining bends, transpressional deformation and basement controls on development; (4) releasing bends, transtensional deformation and fluid flow.

The Tectonic Framework of Assam

Abstract: A spur of ancient rocks partly covered by gently-dipping Tertiary beds extends from the Shillong Plateau and Mikir Hills north-eastwards beneath the alluvium of Upper Assam. Over this spur the Eastern Himalaya have been thrust southwards and the Naga Hills have been thrust north-westwards. The amount of movement of the overthrust masses cannot be determined but it is suggested that in each case the total displacement may be 150-300 kilometres or even more. The Shillong Plateau is separated from the Surma Valley by a faulted monocline with southerly dips. This fault, the Dauki tear-fault, is now shown to have a probable horizontal displacement of about 250 kilometres, and thus to be a major feature of the tectonic pattern of the Indian sub-continent. The horizontal movement along the Dauki tear-fault detached the Shillong Plateau from the main mass of the Indian Shield. The principal movements occurred late in the Tertiary, mostly in the Pliocene.

Fault-propagation folds: Geometry, kinematic evolution, and hydrocarbon traps

Abstract: Fault-propagation folding, a common folding mechanism in fold and thrust belts, occurs when a propagating thrust fault loses slip and terminates upsection by transferring its shortening to a fold developing at its tip. Area-balanced theoretical models that relate the footwall cutoff angle (theta) to the fold interlimb half-angles (gamma* and gamma) show that open folds (high gamma* and gamma) are characterized by relative thickening of stratigraphically higher units, whereas tight folds (low gamma* and gamma) are characterized by relative thinning of these units. The propagation of thrusts is commonly characterized by the progressive tightening of the fold hinge and steepening of the front limb. Thickening of stratigraphically higher units in the early stages of folding i followed by localized thinning of the front limb in the late stages. The geometry of a fault-propagation fold can be modified by subsequent translation on propagating thrusts. The thrust fault may propagate through the undeformed units, along the synclinal axial plane, or through the forelimb of the anticline, depending on the tightness of the fold. Deeper thrusts commonly are abandoned upsection, and the slip transferred to steeper imbricates, resulting in the listric geometries of many thrust faults. The fold also can be transported over a ramp and onto an upper detachment, resulting in a transition to fault-bend folding. Fault-propagation folds with or without additional fold translation can be distinguished from translated detachment folds by the detailed geometries of the hanging wall and footwall structures, and by the characteristic differences n their relations between fault slip and depth to detachment. Some important characteristics of fault-propagation folds are that they require no slip transfer in or out of the structure, involve a minimum amount of shortening, and have a relatively large depth to detachment, compared to other types of fault-related folds. Fault-propagation folds form important hydrocarbon traps in fold and thrust belts. Some common trap types include fold traps in the crestal area, and fault traps in the footwall and along imbricates on the forelimb and the backlimb of major basement-detached and basement-involved anticlines. Secondary traps also occur in intraplate and leading-edge structures within major thrust sheets.

Exhumation of the ultrahigh‐pressure continental crust in east central China: Cretaceous and Cenozoic unroofing and the Tan‐Lu fault

Abstract: The orogenic architecture of the world's largest ultrahigh-pressure exposure, the Hong'an-Dabie Mountains of the Triassic Qinling-Dabie orogenic belt, is dominated by Cretaceous and Cenozoic structures that contributed to its exhumation from ≤30 km depth. Cretaceous magmatic crustal recycling (≥50% for the entire Dabie) and heating (>250° to >700°C) were most prominent in Dabie, and exhumation, magmatism, and cooling were all controlled by Cretaceous transtension. Exhumation was accomplished principally by an asymmetric Cordilleran-type extensional complex in the northern Dabie (Northern Orthogneiss unit) between 140 and 120 Ma, at rates as fast as 2 mm/yr and average horizontal stretching rates of up to 6 mm/yr. Cretaceous reactivation occurred within a regional transtensional strain field as a result of far-field collisions and Pacific subduction. The onset of crustal extension was preceded and possibly facilitated by a reheating of the Hong'an-Dabie crust (∼140 Ma) coeval with the onset of voluminous magmatism in eastern China (∼145 Ma), which resulted from a change in Pacific subduction from highly oblique to orthogonal. The Tan-Lu continental-scale fault was a normal fault zone in the mid-Cretaceous (∼110-90 Ma) and underwent ≥5.4 km dip slip and ≥4 km throw in the Cenozoic. During the India-Asia collision the Qinling-Dabie belt acted as the structural discontinuity between the strike-slip-dominated escape tectonics south of the Qilian-Qinling-Dabie belt and the rifting-dominated tectonism north of it. The most prominent Cretaceous and Cenozoic structures of the Hong'an-Dabie, the Xiaotian-Mozitang and the Jinzhai fault zones, respectively, reactivated major lithospheric structures of the Triassic orogen, i.e., the Huwan detachment zone and the suture.