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Cape, C. D., R. M. O'Connor, J. M. Ravens, and D. J. Woodward. "Seismic expression of shallow structures in active tectonic settings in New Zealand." Exploration Geophysics 20, no. 2 (1989): 287. http://dx.doi.org/10.1071/eg989287.
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Late Cenozoic deformation along the Australian/Pacific plate boundary is seen in onshore New Zealand as zones characterised by extension- or transcurrent- or contraction-related structures. High-resolution multichannel seismic reflection data were acquired in several of these tectonic zones and successfully reveal the shallow structures within them. Thirty kilometres of dynamite reflection data in the Rangitaiki Plains, eastern Bay of Plenty, define a series of NE-trending normal faults within this extensional back-arc volcanic region. The data cross surface ruptures activated during the 1987 Edgecumbe earthquake. In the southern North Island, a 20 km Mini-Sosie? seismic profile details the Quaternary sedimentation history and reveals the structure of the active strike-slip and thrust fault systems that form the western and eastern edges of the Wairarapa basin, respectively. This basin is considered to sit astride the boundary between a zone of distributed strike-slip faults and an active accretionary prism. In the Nelson area, northwestern South Island, previously unrecognised low-angle thrust faults of Neogene or Quaternary age are seen from Mini-Sosie data to occur at very shallow depths. Crustal shortening here was previously thought to arise from movement on high-angle reverse faults, and the identification of these low-angle faults has prompted a reassessment of that model. A grid of 18 km of Mini-Sosie seismic data from the central eastern South Island delineates Neogene or Quaternary thrust faults in Cenozoic sediments. The thrusts are interpreted as reactivated Early Eocene normal faults, and the thrust fault geometry is dominated by these older structures.
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Wex, Sebastian, Neil S. Mancktelow, Friedrich Hawemann, Alfredo Camacho, and Giorgio Pennacchioni. "Inverted distribution of ductile deformation in the relatively “dry” middle crust across the Woodroffe Thrust, central Australia." Solid Earth 9, no. 4 (July 11, 2018): 859–78. http://dx.doi.org/10.5194/se-9-859-2018.
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Abstract. Thrust fault systems typically distribute shear strain preferentially into the hanging wall rather than the footwall. The Woodroffe Thrust in the Musgrave Block of central Australia is a regional-scale example that does not fit this model. It developed due to intracontinental shortening during the Petermann Orogeny (ca. 560–520 Ma) and is interpreted to be at least 600 km long in its E–W strike direction, with an approximate top-to-north minimum displacement of 60–100 km. The associated mylonite zone is most broadly developed in the footwall. The immediate hanging wall was only marginally involved in the mylonitization process, as can be demonstrated from the contrasting thorium signatures of mylonites derived from the upper amphibolite facies footwall and the granulite facies hanging wall protoliths. Thermal weakening cannot account for such an inverse deformation gradient, as syn-deformational P–T estimates for the Petermann Orogeny in the hanging wall and footwall from the same locality are very similar. The distribution of pseudotachylytes, which acted as preferred nucleation sites for shear deformation, also cannot provide an explanation, since these fault rocks are especially prevalent in the immediate hanging wall. The most likely reason for the inverted deformation gradient across the Woodroffe Thrust is water-assisted weakening due to the increased, but still limited, presence of aqueous fluids in the footwall. We also establish a qualitative increase in the abundance of fluids in the footwall along an approx. 60 km long section in the direction of thrusting, together with a slight decrease in the temperature of mylonitization (ca. 100 °C). These changes in ambient conditions are accompanied by a 6-fold decrease in thickness (from ca. 600 to 100 m) of the Woodroffe Thrust mylonitic zone.
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Pettinga, Jarg R., Mark D. Yetton, Russ J. Van Dissen, and Gaye Downes. "Earthquake source identification and characterisation for the Canterbury region, South Island, New Zealand." Bulletin of the New Zealand Society for Earthquake Engineering 34, no. 4 (December 31, 2001): 282–317. http://dx.doi.org/10.5459/bnzsee.34.4.282-317.
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The Canterbury region of the South Island of New Zealand straddles a wide zone of active earth deformation associated with the oblique continent-continent collision between the Australian and Pacific tectonic plates east of the Alpine fault. The associated ongoing crustal strain is documented by the shallow earthquake activity (at depths of <40 km) and surface deformation expressed by active faulting, folding and ongoing geodetic strain. The level of earth deformation activity (and consequent earthquake hazard) decreases from the northwest to the southeast across the region. Deeper-level subduction related earthquake events are confined to the northernmost parts of the region, beneath Marlborough.
To describe the geological setting and seismological activity in the region we have sub-divided the Canterbury region into eight domains that are defined on the basis of structural styles of deformation. These eight domains provide an appropriate geological and seismological context on which seismic hazard assessment can be based. A further, ninth source domain is defined to include the Alpine fault, but lies outside the region.
About 90 major active earthquake source faults within and surrounding the Canterbury region are characterised in terms of their type (sense of slip), geometry (fault dimensions and attitude) and activity (slip rates, single event displacements, recurrence intervals, and timing of last rupture). In the more active, northern part of the region strike-slip and oblique strike-slip faults predominate, and recurrence intervals range from 81 to >5,000 years. In the central and southern parts of the region oblique-reverse and reverse/thrust faults predominate, and recurrence intervals typically range from -2,500 to >20,000 years.
In this study we also review information on significant historical earthquakes that have impacted on the region (e,g. Christchurch earthquakes 1869 and 1870; North Canterbury 1888; Cheviot 1902; Motunau 1922; Buller 1929; Arthurs Pass 1929 and 1994; and others), and the record of instrumental seismicity. In addition, data from available paleoseismic studies within the region are included; and we also evaluate large potential earthquake sources outside the Canterbury region that are likely to produce significant shaking within the region. The most important of these is the Alpine fault, which we include as a separate source domain in this study.
The integrated geological and seismological data base presented in this paper provide the foundation for the probabilistic seismic hazard assessment for the Canterbury region, and this is presented in a following companion paper in this Bulletin (Stirling et al. this volume).
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Wigginton, Sarah S., Elizabeth S. Petrie, and James P. Evans. "The mechanics of initiation and development of thrust faults and thrust ramps." Mountain Geologist 59, no. 2 (April 28, 2022): 47–75. http://dx.doi.org/10.31582/rmag.mg.59.2.47.
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This study integrates the results of numerical modeling analyses based on outcrop studies and structural kinematic restorations to evaluate the mechanics of thrust fault initiation and development in mechanically layered sedimentary rocks. A field-based reconstruction of a mesoscopic thrust fault at Ketobe Knob in central Utah provides evidence of thrust ramp nucleation in competent units, and fault propagation upward and downward into weaker units at both fault tips. We investigate the effects of mechanical stratigraphy on stress heterogeneity, rupture direction, fold formation, and fault geometry motivated by the geometry of the Ketobe Knob thrust fault in central Utah; the finite element modeling examines how mechanical stratigraphy, load conditions, and fault configurations influence temporal and spatial variation in stress and strain. Our modeling focuses on the predicted deformation and stress distributions in four model domains: (1) an intact, mechanically stratified rock sequence, (2) a mechanically stratified section with a range of interlayer frictional strengths, and two faulted models, (3) one with a stress loading condition, and (4) one with a displacement loading condition. The models show that early stress increase in competent rock layers are accompanied by low stresses in the weaker rocks. The frictional models reveal that the heterogeneous stress variations increase contact frictional strength. Faulted models with a 20° dipping fault in the most competent unit result in stress increases above and below fault tips, with extremely high stresses predicted in a ‘back thrust’ location at the lower fault tip. These findings support the hypothesis that thrust faults and associated folds at the Ketobe Knob developed in accordance with a ramp-first kinematic model and development of structures was significantly influenced by the nature of the mechanical stratigraphy.
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SOTIROPOULOS, SPILIOS, EVANGELOS KAMBERIS, MARIA V. TRIANTAPHYLLOU, and THEODOR DOUTSOS. "Thrust sequences in the central part of the External Hellenides." Geological Magazine 140, no. 6 (November 2003): 661–68. http://dx.doi.org/10.1017/s0016756803008367.
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The model of a foreland propagating sequence already presented for the External Hellenides is significantly modified in this paper. New data are used, including structural maps, cross-sections, stratigraphic determinations and seismic profiles. In general, thrusts formed a foreland propagating sequence but they acted simultaneously for a long period of time. Thus, during the Middle Eocene the Pindos thrust resulted in the formation of the Ionian–Gavrovo foreland and acted in tandem with the newly formed Gavrovo thrust within the basin until the Late Oligocene. The Gavrovo thrust consists of segments, showing that out-of-sequence thrusting was important. Thrust nucleation and propagation history is strongly influenced by normal faults formed in the forebulge region of the Ionian–Gavrovo foreland basin. Shortening rates within the Gavrovo–Ionian foreland are low, about 1 mm/year. Although thrust load played an important role in the formation of this basin, the additional load of 3500 m thick clastics in the basin enhanced subsidence and underthrusting.
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Trexler, Charles C., Eric Cowgill, Nathan A. Niemi, Dylan A. Vasey, and Tea Godoladze. "Tectonostratigraphy and major structures of the Georgian Greater Caucasus: Implications for structural architecture, along-strike continuity, and orogen evolution." Geosphere 18, no. 1 (January 6, 2022): 211–40. http://dx.doi.org/10.1130/ges02385.1.
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Abstract Although the Greater Caucasus Mountains have played a central role in absorbing late Cenozoic convergence between the Arabian and Eurasian plates, the orogenic architecture and the ways in which it accommodates modern shortening remain debated. Here, we addressed this problem using geologic mapping along two transects across the southern half of the western Greater Caucasus to reveal a suite of regionally coherent stratigraphic packages that are juxtaposed across a series of thrust faults, which we call the North Georgia fault system. From south to north within this system, stratigraphically repeated ~5–10-km-thick thrust sheets show systematically increasing bedding dip angles (<30° in the south to subvertical in the core of the range). Likewise, exhumation depth increases toward the core of the range, based on low-temperature thermochronologic data and metamorphic grade of exposed rocks. In contrast, active shortening in the modern system is accommodated, at least in part, by thrust faults along the southern margin of the orogen. Facilitated by the North Georgia fault system, the western Greater Caucasus Mountains broadly behave as an in-sequence, southward-propagating imbricate thrust fan, with older faults within the range progressively abandoned and new structures forming to accommodate shortening as the thrust propagates southward. We suggest that the single-fault-centric “Main Caucasus thrust” paradigm is no longer appropriate, as it is a system of faults, the North Georgia fault system, that dominates the architecture of the western Greater Caucasus Mountains.
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FUENTES, FACUNDO, BRIAN K. HORTON, DANIEL STARCK, and ANDRÉS BOLL. "Structure and tectonic evolution of hybrid thick- and thin-skinned systems in the Malargüe fold–thrust belt, Neuquén basin, Argentina." Geological Magazine 153, no. 5-6 (July 25, 2016): 1066–84. http://dx.doi.org/10.1017/s0016756816000583.
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AbstractAndean Cenozoic shortening within the Malargüe fold–thrust belt of west-central Argentina has been dominated by basement faults largely influenced by pre-existing Mesozoic rift structures of the Neuquén basin system. The basement contractional structures, however, diverge from many classic inversion geometries in that they formed large hanging-wall anticlines with steeply dipping frontal forelimbs and structural relief in the order of several kilometres. During Cenozoic E–W shortening, the reactivated basement faults propagated into cover strata, feeding slip to shallow thrust systems that were later carried in piggyback fashion above newly formed basement structures, yielding complex thick- and thin-skinned structural relationships. In the adjacent foreland, Cenozoic clastic strata recorded the broad kinematic evolution of the fold–thrust belt. We present a set of structural cross-sections supported by regional surface maps and industry seismic and well data, along with new stratigraphic information for associated Neogene synorogenic foreland basin fill. Collectively, these results provide important constraints on the temporal and geometric linkages between the deeper basement faults (including both reactivated and newly formed structures) and shallow thin-skinned thrust systems, which, in turn, offer insights for the understanding of hydrocarbon systems in the actively explored Neuquén region of the Andean orogenic belt.
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Cheng, Feng, Andrew V. Zuza, Peter J. Haproff, Chen Wu, Christina Neudorf, Hong Chang, Xiangzhong Li, and Bing Li. "Accommodation of India–Asia convergence via strike-slip faulting and block rotation in the Qilian Shan fold–thrust belt, northern margin of the Tibetan Plateau." Journal of the Geological Society 178, no. 3 (January 29, 2021): jgs2020–207. http://dx.doi.org/10.1144/jgs2020-207.
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Existing models of intracontinental deformation have focused on plate-like rigid body motion v. viscous-flow-like distributed deformation. To elucidate how plate convergence is accommodated by intracontinental strike-slip faulting and block rotation within a fold–thrust belt, we examine the Cenozoic structural framework of the central Qilian Shan of northeastern Tibet, where the NW-striking, right-slip Elashan and Riyueshan faults terminate at the WNW-striking, left-slip Haiyuan and Kunlun faults. Field- and satellite-based observations of discrete right-slip fault segments, releasing bends, horsetail termination splays and off-fault normal faulting suggest that the right-slip faults accommodate block rotation and distributed west–east crustal stretching between the Haiyuan and Kunlun faults. Luminescence dating of offset terrace risers along the Riyueshan fault yields a Quaternary slip rate of c. 1.1 mm a−1, which is similar to previous estimates. By integrating our results with regional deformation constraints, we propose that the pattern of Cenozoic deformation in northeastern Tibet is compatible with west–east crustal stretching/lateral displacement, non-rigid off-fault deformation and broad clockwise rotation and bookshelf faulting, which together accommodate NE–SW India–Asia convergence. In this model, the faults represent strain localization that approximates continuum deformation during regional clockwise lithospheric flow against the rigid Eurasian continent.Supplementary material: Luminescence dating procedures and protocols is available at https://doi.org/10.17605/OSF.IO/CR9MNThematic collection: This article is part of the Fold-and-thrust belts and associated basins collection available at: https://www.lyellcollection.org/cc/fold-and-thrust-belts
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Scherrenberg, Arne F., and Gideon Rosenbaum. "Photograph of the Month: Thrust duplex, low-angle normal faults and domino-style faults in laminated shale, Mt Isa, Australia." Journal of Structural Geology 31, no. 5 (May 2009): 475. http://dx.doi.org/10.1016/j.jsg.2008.10.015.
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Yaseen, Muhammad, Muhammad Shahab, Zeeshan Ahmad, Rehman Khan, Syed Farhan Ali Shah, and Abbas Ali Naseem. "Insights into the structure and surface geology of balanced and retrodeformed geological cross sections from the Nizampur basin, Khyber Pakhtunkhwa, Pakistan." Journal of Petroleum Exploration and Production Technology 11, no. 6 (May 9, 2021): 2561–71. http://dx.doi.org/10.1007/s13202-021-01180-8.
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AbstractThe current research work is an attempt to apply the basic geological procedures, methods of geological mapping, surface and subsurface interpretation and restoration of balanced and retrodeformed cross sections from the Nizampur basin, Khyber Pakhtunkhwa, Pakistan. The work also includes the documentation of several surface structural features, i.e., anticlines, synclines and different types of folds and faults exposed in the vicinity of study area. Four central thrust faults were recognized named as Kahi Thrusts along the cross sections. These thrust faults carried the older sequences of rocks over the younger sequences in different portion along the measured cross section. The folded and faulted rocks in the area show that stratigraphic framework comprises of Eocene, Paleocene, Cretaceous and Jurassic succession of rocks. There are Eocene rocks existing in the extreme South of the mapped area with addition of older Cretaceous and Jurassic succession and contains simple and large-scale folds, faults and back thrust. Two structural transect were mapped which encounter different folds and faults, i.e., X-sections AB oriented NS and CD oriented NE-SW. Restoration of the structural transects was calculated and assumed that at the formation of Main Boundary Thrust, the study area was exposed to the tectonic forces which prognosticated 19.5% shortening in rock sequences from Jurassic to Eocene succession along the measured cross section A_B.
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Savchuk, Yu S., and A. V. Volkov. "The Role of a Detachment Fault in the Spatial Distribution of Ore-Bearing Paleofluid Flows in the Central Kolyma Region: A Nonconventional Approach to Predictive Metallogenic Modeling." Geology of Ore Deposits 64, no. 4 (August 2022): 163–79. http://dx.doi.org/10.1134/s1075701522040055.
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Abstract— The Central Kolyma region is the main gold-bearing part of the Verkhoyansk–Kolyma fold-and-thrust belt. Analysis of the developed geodynamic models of fold and thrust belt formation mechanisms, the Verkhoyansk–Kolyma belt in particular, suggests the leading role of subhorizontal movements on the detachment zone (decollement) at the base of an orogen as the “sole,” on which nappes detached at an early stage and with which major reverse strike-slip listric faults were directly associated at the collisional stage. In our opinion, the role of a detachment fault, the most important regional structure, is obviously underestimated in predictive metallogenic models. The detachment fault zone is complicated by transverse NE-trending faults, where its thickness and the fluid permeability can occur. The paper proposes a variant that links previously discovered gold deposits and occurrences in five gold mineralization strips along the inferred paleofluid flow routes. Here, the paleofluid flow route is the horizontal projection of the most probable migration pathway of released fluids from their generation zone to the ore deposition zone, which is drawn across the largest ore accumulations.
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Thakur, V. C., R. Jayangondaperumal, and V. Joevivek. "Seismotectonics of central and NW Himalaya: plate boundary–wedge thrust earthquakes in thin- and thick-skinned tectonic framework." Geological Society, London, Special Publications 481, no. 1 (December 17, 2018): 41–63. http://dx.doi.org/10.1144/sp481.8.
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AbstractThe tectonic framework of NW Himalaya is different from that of the central Himalaya with respect to the position of the Main Central Thrust and Higher Himalayan Crystalline and the Lesser and Sub Himalayan structures. The former is characterized by thick-skinned tectonics, whereas the thin-skinned model explains the tectonic evolution of the central Himalaya. The boundary between the two segments of Himalaya is recognized along the Ropar–Manali lineament fault zone. The normal convergence rate within the Himalaya decreases from c. 18 mm a−1 in the central to c. 15 mm a−1 in the NW segments. In the last 800 years of historical accounts of large earthquakes of magnitude Mw ≥ 7, there are seven earthquakes clustered in the central Himalaya, whereas three reported earthquakes are widely separated in the NW Himalaya. The earthquakes in central Himalaya are inferred as occurring over the plate boundary fault, the Main Himalayan Thrust. The wedge thrust earthquakes in NW Himalaya originate over the faults on the hanging wall of the Main Himalayan Thrust. Palaeoseismic evidence recorded on the Himalayan front suggests the occurrence of giant earthquakes in the central Himalaya. The lack of such an event reported in the NW Himalaya may be due to oblique convergence.
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Carlsen, G. M., A. P. Simeonova, and S. N. Apak. "PETROLEUM SYSTEMS AND EXPLORATION POTENTIAL IN THE OFFICER BASIN, WESTERN AUSTRALIA." APPEA Journal 43, no. 1 (2003): 473. http://dx.doi.org/10.1071/aj02025.
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The Officer Basin in Western Australia contains a variety of hydrocarbon plays associated with compressional, halokinetic, unconformity and stratigraphic traps. Five distinct structural zones have been defined in the basin—a northeastern Marginal Overthrusted Zone, a northeastern Salt-ruptured Zone, a central Thrusted Zone, a Western Platform and a complex salt-dominated Minibasins Zone. These zones, together with salt-associated and sub-salt structure, are well delineated on about 2,900 km of reprocessed 1980s vintage seismic data, now publicly released.Neoproterozoic rocks are marginally to fully mature for oil generation on the Western Platform and immature to overmature for different levels of the succession in the Salt-ruptured and Thrusted zones. Geochemical modelling indicates that the main phases of oil generation vary from different stratigraphic intervals and different parts of the Neoproterozoic basin with peaks during the latest Neoproterozoic, Cambrian, and Permian–Triassic. A variety of hydrocarbon shows have been recorded in each of the structural zones. The most recent, a gas show recorded in the stratigraphic well Vines–1 indicates the presence of potentially effective petroleum systems in the unexplored Waigen area of the Marginal Overthrusted Zone.A wide variety of trap styles have been identified, associated with normal faults, thrust faults, thrust ramp folds, compressive folds, fault tip folds, sub-salt plays, unconformity truncations, pinchouts, lateral facies changes, erosive channels and valleys, fractured carbonates and halokinetic traps. Most of these trap styles are poorly tested or untested.
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Hervouet, Yves, Jose Tomass Castrillo-Delgado, and Oscar Odreman. "Interaction entre un chevauchement imbrique et une zone transcurrente; le flanc nord-ouest de Andes venezueliennes." Bulletin de la Société Géologique de France 172, no. 2 (March 1, 2001): 159–75. http://dx.doi.org/10.2113/172.2.159.
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Abstract Geological framework; Geological setting: The Venezuela Andes or Merida Andes (fig. 1) extend from the Colombian border in the SW to Barquisimeto in the NE, and constitute a basement uplift exceeding 5,000 m near Merida (Pico Bolivar). This young chain is bordered to the W by the Maracaibo foredeep basin, and to the E by the Barinas-Apure foreland basin. The Bocono fault divides the Andean Belt in two parts along a NE-SW direction. This shows that the uplift of the Andes is contemporaneous with an oblique translation. In the study area, located on the northwestern flank near Maracaibo basin, three major structures are present: in the E, the N-S senestral strike slip Valera-Rio Momboy fault, in the S the E-W dextral strike slip Pinango fault and, in the center, the SW-NE striking Las Virtudes thrust verging toward NW. Lithologic and stratigraphic formations (fig. 4): The Las Virtudes Fault separates two different structural zones. In the SE, overthrust units are made of crystalline basement, Paleozoic substratum and preorogenic sedimentary formations (Cretaceous-Eocene). The foredeep flexural basin, located NW, is filled by synorogenic molasses (Neogene and Quaternary), largely developed within the Betijoque Fm. (Upper Miocene to Pliocene in age) which reaches a thickness of 5000 m. Structure of the northwestern Andean flank; Las Virtudes Fault and its thrust slice zone: Near Las Virtudes village (fig. 5, 6-2), this thrust is systematically associated with a narrow overturned foredeep depobelt (Cretaceous to Neogene in age). These slices are unknown elsewhere in the Andean Chain and represent the terminal faulted part of the thrust drag. However, where this slice zone is missing (central and northeastern part of the study area), the Las Virtudes Fault is not clearly documented: its throw decreases rapidly and it is possible that the fault disappears northeastward. Andean unit: Near the main strike slip faults, NE trending SE verging reverse faults develop (fig. 6-5). In central and northeastern parts, the throw of the reverse faults increases toward the Valera Fault. It seems that reverse faults are horsetail of this major strike slip fault (fig. 5). Internal part of the northwestern Andean foredeep basin: The foredeep sedimentary formations generally dip toward the NW. Associated to the lack of some formations, tilted anticlines toward the SE are observed (fig. 6-3 and 6-7), and indicate the vicinity of decollement levels in the foredeep, located in Luna-Colon, Pauji and Betijoque Fm.. Seismic profiles show (fig. 7) that the major decollement level of the foredeep is located in La Luna and Colon Fms. [Audemard, 1991; De Toni and Kellogg, 1993; Colletta et al., 1997]. Crustal architecture and timing of the deformation: Several stages can be distinguished in the building of the Andes. Development of an intracutaneous thrust wedge: The first effects of the Andean phase during Miocene are the development of an intracutaneous thrust wedge [Price, 1986]. The lower flat is located in the basement and the upper one in Cretaceous formations. The transport direction is NW. The foredeep develops on the forelimb of this structure and collects detrital products coming from erosion of the first (oldest) reliefs. Decollements in the foredeep basin could be contemporaneous with this major overthrust. Their origin could be due to radius of curvature differences within the thick sedimentary formations (fig. 8). Las Virtudes Fault and backthrusting: Las Virtudes Fault is one of the last events of this part of the Andean Belt. During Plio-Pleistocene, the continental crust breaks with a dip of 35 degrees SE. The Andean unit overthrusts the foredeep basin. Some of the foredeep decollements could still be active and form, together with Andean basement, a triangle zone. Las Virtudes Fault throw reaches 5 km between Las Virtudes and Monte Carmelo villages (fig. 8A). It decreases southwestwards and the back thrusts are probably younger. Northeastwards the throw decreases and eventually disappears (fig. 8B). In the same time the back thrust throws increase. Both seem to be contemporaneous. Conclusions: This structural model explains the basement occurrence in front of the Las Virtudes Fault on seismic profiles and allows to restore correctly the different northwestern flank structures of the Venezuela Andes. These structures can be explained by the conjugate movements of a NW verging intracutaneous thrust wedge and strike slip faults which create a SE verging triangular area (fig. 5). The Andean overthrust is transferred in the Falcon zone along the Valera fault. In the northeastern part of the Maracaibo block, the Valera and Bocono strike slip faults limit the Trujillo block (fig. 10) which moves towards the North during Neogene and Quaternary times.
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Imrecke, Daniel B., Alexander C. Robinson, Lewis A. Owen, Jie Chen, Lindsay M. Schoenbohm, Kathryn A. Hedrick, Thomas J. Lapen, Wenqiao Li, and Zhaode Yuan. "Mesozoic evolution of the eastern Pamir." Lithosphere 11, no. 4 (May 16, 2019): 560–80. http://dx.doi.org/10.1130/l1017.1.
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Abstract We present field and analytical results from the Tashkurgan and Waqia valleys in the southeastern Pamir that shed new light on the tectonic evolution and terrane architecture of the region. Field mapping of metasedimentary and igneous units along the Tashkurgan and Waqia valleys in the Southeast Pamir, integrated with metamorphic petrology, garnet-biotite thermometry, and zircon U/Pb isotopic analysis, help identify major structures and terrane boundaries in the region, as well as compare structural units across the Miocene Muztaghata gneiss dome. South of the Muztaghata dome, the gently northwest-plunging synformal Torbashi thrust klippe juxtaposes amphibolite facies Triassic Karakul-Mazar terrane schist and gneiss structurally above (1) greenschist facies Triassic Karakul-Mazar terrane metasedimentary rock in the north, and (2) lower-amphibolite facies schist in the south that are interpreted to be Gondwanan-derived crust (Central or South Pamir terrane). Farther south, the Rouluke thrust fault imbricates the Gondwanan crust, placing early Paleozoic schists over Permian marble and slate. Exposure of the Torbashi thrust sheet terminates in the southeast, and with it the surface exposure of the Triassic Karakul-Mazar terrane, leaving the Paleozoic Kunlun terrane juxtaposed directly against Gondwanan terrane crust. Based on lithologic and isotopic similarities of units north and south of the Muztaghata gneiss dome, we document the existence of a regionally extensive thrust nappe that stretched across the northern and eastern Pamir, prior to being cut by Miocene exhumation of the Muztaghata dome. The thrust nappe links the Torbashi thrust in the southeast Pamir with the Tanymas thrust in the northern Pamir, and documents regionally extensive exposure of lithologically continuous units across the northeast Pamir. While timing of emplacement of the Torbashi thrust klippe and displacement on the Rouluke fault to the south is not well constrained, we interpret shortening to be Cretaceous in age based on previously published cooling ages. However, a component of Cenozoic shortening cannot be ruled out. A key observation from our mapping results is that the surface exposures of the Karakul–Mazar–Songpan Ganzi terrane are not continuous between western Tibet and the Pamir, which indicates tectonic and/or erosional removal, likely sometime in the Mesozoic. Furthermore, our documentation of the Jinsha suture in the southeast Pamir on the eastern side of the Karakoram fault shows deflections of terranes across the Himalayan-Tibetan orogen were not primarily accommodated along discrete, large displacement faults (>400 km) faults. Instead, oroclinal bending of the northern Pamir, and dextral shear along the Pamir margins, may be largely responsible for the northward deflection of terranes.
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Passchier, C. W., and P. R. Williams. "Proterozoic extensional deformation in the Mount Isa inlier, Queensland, Australia." Geological Magazine 126, no. 1 (January 1989): 43–53. http://dx.doi.org/10.1017/s0016756800006130.
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AbstractThe earliest of four distinct phases of deformation recognized in the central part of the Proterozoic Mount Isa inlier involved brittle extensional faulting at shallow crustal levels. Extensional faulting produced stacks of imbricate fault slices, listric normal faults and characteristic tourmalinerich breccias. Structures belonging to this phase occur over a large part of the inlier and indicate an important phase of basin-forming crustal or lithospheric extension at 1750–1730 Ma. Late intense ductile deformation and tight folding of the imbricate systems destroyed part of these older structures, and obscures their existence in many parts of the inlier.
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Godin, Laurent, Renaud Soucy La Roche, Lindsay Waffle, and Lyal B. Harris. "Influence of inherited Indian basement faults on the evolution of the Himalayan Orogen." Geological Society, London, Special Publications 481, no. 1 (April 13, 2018): 251–76. http://dx.doi.org/10.1144/sp481.4.
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AbstractIndian basement faults, which bound three orogen-perpendicular palaeotopographic ridges of Precambrian Indian basement south of the Himalaya, extend to the base of the Indian lithosphere and to the northern extent of the Indian lithosphere underneath Tibet. In the eastern Himalaya, the active orogen-perpendicular Yadong–Gulu graben is aligned with an earthquake-generating strike-slip fault in the high Himalaya. We argue that the graben results from crustal necking during reactivation of the underplated basement fault. In the central Himalaya, along-strike diachronous deformation and metamorphism within the Himalayan metamorphic core, as well as lateral ramps in the foreland thrust belt, spatially correspond to the Lucknow and Pokhara lineaments that bound the subsurface Faizabad Ridge in the Indian basement. Analogue centrifuge modelling confirms that offset along such deep-seated basement faults can affect the location, orientation and type of structures developed at various stages of orogenesis and suggests that it is mechanically feasible for strain to propagate through a melt-weakened mid-crust. We suggest that inherited Indian basement faults affect the ramp-flat geometry of the basal Main Himalayan Thrust, partition the Himalayan range into distinct zones, localize east–west extension resulting in the Tibetan graben and, ultimately, contribute to lateral variability in tectonic evolution along the orogen's strike.
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Smekalin, O. P., and A. V. Chipizubov. "Fault Activation in Central Mongolia during the Holocene: Results of Study of the Mogod Earthquake Ruptures." Russian Geology and Geophysics 62, no. 11 (November 1, 2021): 1285–95. http://dx.doi.org/10.2113/rgg20204222.
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Abstract —In order to determine the seismotectonic activity of faults in the Holocene, we performed trench studies of the ruptures produced by the catastrophic Mogod earthquake (5 January 1967, M = 7.5–7.8, I0 = 9–10) in the junction zone of the N–S striking Hulzhin Gol fault and the NW striking Tullet fault. Paleoseismic interpretation of seismic-deformation sections and radiocarbon dating of the samples allowed determining the kinematics and obtaining, for the first time, the absolute ages of paleoevents preceding the Mogod earthquake. Analysis of the tectonic conditions for realization of earthquake sources has shed light on the complex structure of ruptures in the area of the Mogod earthquake epicenter, within which three segments differing in the displacement amplitudes and kinematics have been identified. The research data indicate the repeated activation of the Tulet and Hulzhin Gol faults in the Late Pleistocene–Holocene. The absolute age of the latest activation is 596–994 AD for the Tulet fault and 11,379–6235 BC for the Hulzhin Gol fault. The cumulative deformation from paleoearthquakes in the trench sections in the Tulet fault zone points to at least two displacements of thrust kinematics, with the latest of them having an amplitude of 2.8 m. The paleoearthquake in the Hulzhin Gol fault zone is characterized by the presence of lateral slip. The amplitudes of deformations attest to earlier earthquakes similar in energy to the 1967 Mogod event or even stronger in the fault node. The obtained data on the timing of these earthquakes and the amplitudes of the accompanying displacements made it possible to estimate slip rates along the faults: 0.2–0.3 m/kyr horizontal-slip rates on the Hulzhin Gol fault and 0.5–0.7 m/kyr vertical-slip rates on the Tulet fault.
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Beaudouin, Thierry, Oliver Bellier, and Michel Sebrier. "Present-day stress and deformation field within the Sulawesi Island area (Indonesia) : geodynamic implications." Bulletin de la Société Géologique de France 174, no. 3 (May 1, 2003): 305–17. http://dx.doi.org/10.2113/174.3.305.
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Abstract Sulawesi Island, eastern Indonesia, is located at the junction between the Pacific-Philippine, Indo-Australian Plates, and the Sunda Block, i.e., the southeastern edge of the Eurasian Plate (fig. 1). Its peculiar shape results from an on-going complex history of collision and rotation of continental slivers, island arcs, and oceanic domains with respect to the Sunda Block. Seismic network document a high level of seismicity in its northern boundaries, corresponding to deformation along the North Sulawesi trench and within the Molucca Sea subduction (fig. 1). Seismic activity is lower in central and south Sulawesi (fig. 4). It represents the activity of the NE, SW and SE arms thrust and the left-lateral Central Sulawesi Fault System, which comprises the Palu-Koro and Matano fault zones. This system connects, from northwest to southeast, the North Sulawesi Subduction zone to the Sorong fault (through th Sud Sula fault, after, Hinschberger et al. [2000] and the Tolo thrust in the North Banda Sea, Silver et al., [1983] proposed a deformation model that implies a clockwise rotation of the Sula block that is limited to the west and south by the Central Sulawesi Fault System. Paleomagnetic [Surmont et al., 1994] and GPS [Walpersdorf et al., 1998a] studies confirm and measure this rotation. In order to discus the present day kinematics and deformation of Sulawesi area, we performed a seismotectonic study, using focal mechanism of moderate and large (Mw ≥ 5) shallow earthquake (≤ 60 Km), collected from the Harverd CMT database (period 1976 to 2001) and complemented by Fitch [1972] and Cardwell [1980] (period 1964–1976). From these focal mechanisms and the known structural context, we defined ten homogeneous deformation domains (fig. 3 et fig.5). For seven of these, focal solution and moment tensors were inverted (Carey-Gailhardis and Mercier method [1987Carey-Gailhardis and Mercier method [1992]) and summed, in order to obtain stress and deformation tensors and rate estimates (Brune [1968] or Kostrov [1974] methods). Results are presented in table I, on figure 2 and figure 3. In northern Molucca Sea (north of equvator), the fast convergence slip rate (75 mm/a) is absorbed by the Sangihe subduction and accommodates the major part of the Philippines/Sunda plates motion. South of the equator, the estimated slip rate is only 2 mm/yr and represents the Sangihe slap subduction, which is affected by a torsion from NNE to E strike. Along the North-Sulawesi fault system, direction of the stress axes are not significantly different from east to west (average N356°±5E), but the determined slip rates increase from 20±4 mm/a to 54±10 mm/a, respectively. These values agree with the Sula block rotation pole previously proposed and located at the eastern extremity of the Northern Arm. The Palu-Koro fault, bounding the western Sula block, contributes to this rotaion because its trace fits well a small circle centered on the pole. However, seisicity document few moderate magnitude earthquake (fig. 4) related to the left lateral Central Sulawesi fault system, despite many identified active tectonic feature [Beaudouin, 1998]. Moreover, geologically determined Palu-Koro long-term slip rate of 35±8 mm/a, [Bellier et al., 2001] agrees with the far-field strike-slip rate of 32–45 mm/a proposed from GPS measurement [Walpersdorf et al., 1998b ; Stevens et al., 1999]. This confirms that is a fast slipping fault with a relatively low level of seismicity. The southeastern limit of the Sula block is represented by the ENE-trending Sorong strike-slip fault that extends from Irian-Jaya island to the east coast of Sulawesi where it connects to the Matano fault through the South Sula fault, This structure is particularly active south of the Sula island with a major Mw=7.7 earthquake (29/11/98). The inversion provides a strike-slip regime with respectively N220°E and N310°E-trending σ1. and σ3 stress axes. This study also highlight the Sula block internal deformation that could explain in the GPS velocities model obtained by walpersdorf et al. [1998a] for the Sula block rotation. We evidence an extensional stress regime with a N030°E-trending σ3, in the southern part of the Tomini Gulf. The estimated extension rate is 9 mm/a toward a N036°E direction. Considering the location of the Tomini Gulf, this deformation could be interpreted as a back-arc spreading related to the North Sulawesi subduction. The Batui zone correspond to the domain of the collision wich occured in the early-middle Plicene [e.g., Velleneuve et al., 2000] between the NE arm and the Irian-jaya derived Banggaï-Sula block. This domain remains active (12 earthquake with a major one of Mw=7.6, 14/05/00, fig. 4) but is mainly affected by strike-slip deformation. The Tolo thrust, lying off the SE arm east coast, absorbs the convergence to the west of the North Banda Sea, as attested by six moderate earthquake with reverse faulting focal mechanisms. This allows to distinguish a North-Banda block in SE Sulawesi, bounded by the South Sula segment of the Sorong fault, the Tolo thrust and the Hamilton fault (fig. 5) and moving westward at a lower rate than the Sula block. The SW arm of Sulawesi is also characterised by a compressional stress regime with N099°E-trending σ1 and an estimated convergence rate of 8.5 mm/a toward a N080°E direction. This is the consequence of the Majene-Kalosi thrust activity and could represent the most western accommodation of the Philippines/Sunda plates motion.
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Guillaume, Benjamin, Guido M. Gianni, Jean-Jacques Kermarrec, and Khaled Bock. "Control of crustal strength, tectonic inheritance, and stretching/ shortening rates on crustal deformation and basin reactivation: insights from laboratory models." Solid Earth 13, no. 9 (September 2, 2022): 1393–414. http://dx.doi.org/10.5194/se-13-1393-2022.
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Abstract. Geological settings characterized by multiple coeval tectonic regimes provide a unique opportunity to understand complex interactions among different geodynamic processes. However, they remain comparatively less studied from an experimental point of view than areas with more simple patterns of deformation resulting from primary plate–boundary interactions. Here, we carried out analog experiments involving simultaneous shortening and orthogonal extension under different rheological conditions, including the effect of crustal inheritance. We performed brittle experiments and brittle–ductile experiments to simulate cases of “strong” and “weak” crusts, respectively. We present two types of experiments: (i) one-stage experiments with either shortening only or synchronous orthogonal shortening and stretching and (ii) two-stage experiments with a first stage of stretching and a second stage with either shortening only or synchronous orthogonal shortening and stretching. In our models, deformation is accommodated by a combination of normal, thrust, and strike-slip faults with structure location depending on boundary conditions and crustal inheritance. For brittle models, we show that the three types of structures can develop at the same time for intermediate ratios of stretching (extension) over shortening rates (1.4<Ve/Vs<2). For lower ratios, deformation is accommodated by in-sequence shortening-orthogonal thrust faults and stretching-orthogonal normal faults at the edges of the model (when Ve>0). For larger ratios and for the same amount of stretching, deformation is accommodated by normal faults at edges and in the center of the model as well as by conjugate strike-slip faults at the edges of the model. For brittle–ductile models, we always observe strike-slip faults that crosscut the entire model. They are associated with shortening-orthogonal thrust faults for models with low Ve/Vs and no initial extensional stage or stretching-orthogonal normal faults for models with high Ve/Vs and an initial extensional stage. Whatever the crustal strength, the past deformation history, and the stretching / shortening ratio, both normal and thrust faults remain with similar orientations, i.e., stretching-orthogonal and shortening-orthogonal, respectively. Instead, strike-slip faults exhibit orientations with respect to the shortening direction that vary between ∼0 and ∼65∘. Strike-slip faults parallel to the shortening direction develop in previously extended portions of models with a brittle–ductile crust, while strike-slip faults with a high angle form at the boundaries of the brittle model, their orientation being to some extent influenced by pre-existing or newly forming graben in the center of the model. We also show that extensional structures formed during a first stage of deformation are never inverted under orthogonal shortening but can be reactivated as normal or strike-slip faults depending on Ve/Vs. Our experiments reproduce V-shaped conjugate strike-slip systems and normal faulting during compression similar to structures observed in the Tibetan Plateau, the eastern Alps, western Anatolia, and the Central Asia orogen. Models with two-stage deformation show variable extensional to strike-slip reactivation of former extensional basins during basin-parallel shortening, which resembles synorogenic foreland transtensional reactivations documented in the Baikal and Golfo de San Jorge basins.
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Yu, Fusheng, Ruifeng Zhang, Jiafu Yu, Yidan Wang, Shuguang Chen, Jing Liu, Chenlin Wu, et al. "Meso-Cenozoic negative inversion model for the Linhe Depression of Hetao Basin, China." Geological Magazine 159, no. 4 (December 1, 2021): 535–60. http://dx.doi.org/10.1017/s0016756821001138.
Full textAbstract:
AbstractThe Linhe Depression is the largest tectonic unit in the Hetao Basin. The recently discovered commercial oil flow in the structural trap of wells JH2X and S5 has proved that the Meso-Cenozoic strata in the Linhe Depression have great exploration potential. Research on the kinematic model for the Mesozoic–Cenozoic Linhe Depression is important for analysing the geological conditions of hydrocarbon accumulation. In this study, field observations, seismic interpretation and scaled analogue modelling are performed. The results prove that the Linhe Depression experienced different stages of tectonic evolution, such as compressional depression (K1l), conversion from contraction to uniform subsidence (K1g), extensional rifting (E2–N2) and strike-slip deformation (Q), during the Mesozoic–Cenozoic eras. The kinematic model of negative inverted basins was first established with the early differential compression superimposed by the late extension. The seismic interpretation and analogue modelling results show that Jilantai Sag in the southern part of the Linhe Depression was subjected to compression from the Bayanwulashan fold–thrust belt on the NW side and the Helanshan fold–thrust belt on the SE side during Early Cretaceous time. Meanwhile, the Hanghou Sag in the northern part of the Linhe Depression was only compressed by the Langshan fold–thrust belt from the NW direction. The rifted structure generated by the extension from the SE direction during the Cenozoic Era resulted in the negative inversion of the pre-existing thrusts in different patterns. The intensity of negative inversion is controlled by several key factors, such as dip angle and the patterns of thrust faults, along with different basement textures. The morphological changes in the forebulge zone developed during Early Cretaceous time are responsible for the development of the segmented Central fault zones in the Hanghou Sag.
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Umhoefer, Paul J., Stuart N. Thomson, Côme Lefebvre, Michael A. Cosca, Christian Teyssier, and Donna L. Whitney. "Cenozoic tectonic evolution of the Ecemiş fault zone and adjacent basins, central Anatolia, Turkey, during the transition from Arabia-Eurasia collision to escape tectonics." Geosphere 16, no. 6 (October 27, 2020): 1358–84. http://dx.doi.org/10.1130/ges02255.1.
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Abstract The effects of Arabia-Eurasia collision are recorded in faults, basins, and exhumed metamorphic massifs across eastern and central Anatolia. These faults and basins also preserve evidence of major changes in deformation and associated sedimentary processes along major suture zones including the Inner Tauride suture where it lies along the southern (Ecemiş) segment of the Central Anatolian fault zone. Stratigraphic and structural data from the Ecemiş fault zone, adjacent NE Ulukışla basin, and metamorphic dome (Niğde Massif) record two fundamentally different stages in the Cenozoic tectonic evolution of this part of central Anatolia. The Paleogene sedimentary and volcanic strata of the NE Ulukışla basin (Ecemiş corridor) were deposited in marginal marine to marine environments on the exhuming Niğde Massif and east of it. A late Eocene–Oligocene transpressional stage of deformation involved oblique northward thrusting of older Paleogene strata onto the eastern Niğde Massif and of the eastern massif onto the rest of the massif, reburying the entire massif to >10 km depth and accompanied by left-lateral motion on the Ecemiş fault zone. A profound change in the tectonic setting at the end of the Oligocene produced widespread transtensional deformation across the area west of the Ecemiş fault zone in the Miocene. In this stage, the Ecemiş fault zone had at least 25 km of left-lateral offset. Before and during this faulting episode, the central Tauride Mountains to the east became a source of sediments that were deposited in small Miocene transtensional basins formed on the Eocene–Oligocene thrust belt between the Ecemiş fault zone and the Niğde Massif. Normal faults compatible with SW-directed extension cut across the Niğde Massif and are associated with a second (Miocene) re-exhumation of the Massif. Geochronology and thermochronology indicate that the transtensional stage started at ca. 23–22 Ma, coeval with large and diverse geological and tectonic changes across Anatolia.
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Higgins, A. K. "Geology of central and eastern North Greenland." Rapport Grønlands Geologiske Undersøgelse 128 (December 31, 1986): 37–54. http://dx.doi.org/10.34194/rapggu.v128.7923.
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A historical review of geological research in North Greenland is followed by a summary of the main results of the 1978-80 GGU expeditions to the region. New outcrops of Archaean and early Proterozoic crystalline rocks are recorded only as xenoliths in dykes and volcanic centres. A revised stratigraphy is applied to the middle Proterozoic Independence Fjord Group sandstones, while petrographic and isotopic studies have been made of the cross-cutting Midsommersø dolerites and the overlying Zig-Zag Dal Basalt Formation. No convincing evidence has been found of a Carolinidian orogenic episode separating these units from succeeding late Proterozoic sedimentary sequences. Lower Palaeozoic sediments dominate North Greenland and are divided into southern shelf and northern trough successions; new or revised stratigraphies are now applied in both settings. The shelf-trough boundary can be shown to have moved south with time, and a major early Silurian expansion of the trough is related to shelf subsidence and a new phase of turbidite deposition derived from the rising East Greenland Caledonian mountains. Devonian - Middle Carboniferous (Ellesmerian) deformation brought deposition to a close and created the North Greenland fold belt, in which deformation intensity and metamorphic grade increase northwards. Thin-skinned thrusting in association with west or south-facing folds is important in southern areas; this is one of the main differences in interpretation compared to earlier work in the fold belt. New outcrops of post-ElIesmerian sediments (Wandel Sea Basin) have mainly been recorded as fault or thrust bounded sequences; a new stratigraphy is applied to the Wandel Sea Basin succession. Cretaceous - Tertiary events include a suite of volcanic centres, dyke swarms, the Kap Washington Group volcanics, and faults and thrusts of Tertiary (Eurekan) age; all have been studied anew, as have the Quaternary deposits.
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Thurlow, J. G., C. P. Spencer, D. E. Boerner, L. E. Reed, and J. A. Wright. "Geological interpretation of a high resolution reflection seismic survey at the Buchans mine, Newfoundland." Canadian Journal of Earth Sciences 29, no. 9 (September 1, 1992): 2022–37. http://dx.doi.org/10.1139/e92-159.
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Sixteen kilometres of high resolution Vibroseis reflection seismic data have been acquired in the vicinity of the former Buchans mine. Direct identification of the cause of several reflectors is possible because the geology is tightly constrained by underground workings and drill holes both of which locally exceed 1 km depth. Many of the mine-scale thrust faults are imaged as reflectors but conformable and intrusive contacts generally responded poorly. A significant shallow-dipping thrust, the Powerline Fault, is recognized below the orebodies and traced throughout the Buchans area, primarily as a result of the seismic survey. It truncates ore stratigraphy and forms the floor thrust of a large duplex–stack, which hosts all the orebodies. Its presence has negative implications for exploration in the immediate mine area. Several lines of evidence suggest that this fault has a significant component of out-of-sequence movement. A strong reflector 4.5 km below Buchans is correlated with the surface expression of the Victoria River Delta Fault, an important regional structure, newly recognized southeast of Red Indian Lake. This shallow, north-dipping sole thrust forms the structural base of the Buchans Group and brings it above a younger fossiliferous Llanvirn volcanic sequence. This fault is not itself the Red Indian Line but is one of a series of faults that collectively effect substantial geological contrasts in central Newfoundland. The seismic survey was a cost-efficient means of gaining knowledge of Buchans structure, which might otherwise have been acquired at much higher cost and over a longer period of time.
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Cao, Kai, Philippe Hervé Leloup, Guocan Wang, Wei Liu, Gweltaz Mahéo, Tianyi Shen, Yadong Xu, Philippe Sorrel, and Kexin Zhang. "Thrusting, exhumation, and basin fill on the western margin of the South China block during the India-Asia collision." GSA Bulletin 133, no. 1-2 (April 30, 2020): 74–90. http://dx.doi.org/10.1130/b35349.1.
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Abstract The pattern and timing of deformation in southeast Tibet resulting from the early stages of the India-Asia collision are crucial factors to understand the growth of the Tibetan Plateau, but they remain poorly constrained. Detailed field mapping, structural analysis, and geochronological and thermochronological data along a 120 km section of the Ludian-Zhonghejiang fold-and-thrust belt bounding the Jianchuan basin in western Yunnan, China, document the early Cenozoic tectonic evolution of the conjunction between the Lanping-Simao and South China blocks. The study area is cut by two major southwest-dipping brittle faults, named the Ludian-Zhonghejiang fault and the Tongdian fault from east to west. Numerous kinematic indicators and the juxtaposition of Triassic metasedimentary rocks on top of Paleocene strata indicate thrusting along the Ludian-Zhonghejiang fault. Similarly, structural analysis shows that the Tongdian fault is a reverse fault. Between these structures, fault-bounded Permian–Triassic and Paleocene rocks are strongly deformed by nearly vertical and upright southwest-vergent folds with axes that trend nearly parallel to the traces of the main faults. Zircon and apatite (U-Th)/He and apatite fission-track data from a Triassic pluton with zircon U-Pb ages of 237–225 Ma in the hanging wall of the Ludian-Zhonghejiang fault, assisted by inverse modeling, reveal two episodes of accelerated cooling during 125–110 Ma and 50–39 Ma. The Cretaceous cooling event was probably related to crustal thickening during the collision between the Lhasa and Qiangtang terranes. The accelerated exhumation during 50–39 Ma is interpreted to record the life span of the fold-and-thrust belt. This timing is corroborated by the intrusive relationship of Eocene magmas of ca. 36–35 Ma zircon U-Pb age into the fold-and-thrust belt. Early Cenozoic activity of the deformation system controlled deposition of alluvial-fan and braided-river sediments in the Jianchuan basin, as evidenced by eastward and northeastward paleoflows and terrestrial clasts derived from the hanging wall of the Ludian-Zhonghejiang thrust. Since 39 Ma, decreasing cooling rates likely reflect cessation of activity on the fold-and-thrust belt. Early Cenozoic compressive deformation on the western margin of the South China block together with geological records of contraction in central, northern, and eastern Tibet document Eocene upper-crustal shortening located in the Himalaya, Qiangtang terrane, and northern plateau margins together with contractional basin development in the intervening Lhasa, Songpan-Garze, and Kunlun terranes, coeval with or shortly after the onset of the India-Asia collision. This suggests that moderate crustal shortening affected a large part of Tibet in a spaced way, contrary to models of homogeneous crustal thickening soon after the collision, and prior to the main crustal thickening, propagating progressively from south to north. This complex deformation pattern illustrates the complexity of Asian crustal rheology, which contrasts with assumptions in existing geodynamic models.
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Julikah, Julikah, Ginanjar Rahmat, and Muhammad Budisatya Wiranatanegara. "Subsurface Geological Evaluation of the Central Sumatra Basin in Relation to the Presence of Heavy Oil." Scientific Contributions Oil and Gas 44, no. 1 (July 15, 2021): 65–81. http://dx.doi.org/10.29017/scog.44.1.491.
Full textAbstract:
Central Sumatra Basin has been proven as a mature basin that produces large amounts of conventional oil. In fact, some of the existing oil fi elds are heavy oil containing such as Duri, Sebanga, Rantau Bais, and Kulin fi elds with their API Gravity values of lower than 25o . Apart from those oil fi elds the Central Sumatra Basin is expected to bear signifi cant heavy oil potential. In this light, this paper emphasizes discussion of subsurface geological evaluation on suspected fi elds/areas that contain heavy oil. This evaluation serves as a preliminary step in investigation of heavy oil resources/reserves in the basin. Analysis results on stratigraphic sequence and seismic interpretation provide information support facts over presence of heavy oil that are usually associated to main faults of Dalu-Dalu, Rokan, Sebanga, Petapahan, Pulau Gadang, and Kotabatak. Large tectonic events as a compression phase in the Middle Miocene – recent developed regional uplift and formed main thrust faults system, anticline structures due to the creature of basement highs, during which the F3 was deposited. The thrust faults system are important in the process of heavy oil generation in which surface water encroached into uplifted oil traps hence triggering heavy oil transformation mechanisms of biodegradation and water washing. This study provides illustration over sequences the heavy oil is generated in and their dimension in relation to area of structural anticlines. Based on available data, evaluation on subsurface geology has shown that anticlinal structures containing heavy oil tend to be characterized by near surface uplift (Basement up to 500 - 750 ms), whereas structures with lesser certainty in heavy oil containment tend show lower degrees of uplift marked by basement depth around 1000 ms or deeper. In general, seismic interpretation has shown that heavy oil is contained some sequences within sequences of 4 to 7 (equivalent to Menggala, Bekasap, Bangko, and Duri-Telisa formations).
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Hinsch, Ralph, Chloé Asmar, Muhammad Nasim, Muhammad Asif Abbas, and Shaista Sultan. "Linked thick- to thin-skinned inversion in the central Kirthar Fold Belt of Pakistan." Solid Earth 10, no. 2 (March 22, 2019): 425–46. http://dx.doi.org/10.5194/se-10-425-2019.
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Abstract. The Kirthar Fold Belt is part of the transpressive transfer zone in Pakistan linking the Makran accretionary wedge with the Himalaya orogeny. The region is deforming very obliquely, nearly parallel to the regional S–N plate motion vector, indicating strong strain partitioning. In the central Kirthar Fold Belt, folds trend roughly N–S and their structural control is poorly understood. In this study, we use newly acquired 2-D seismic data with pre-stack depth migration, published focal mechanisms, surface and subsurface geological data, and structural modelling with restoration and balancing to constrain the structural architecture and kinematics of the Kirthar Fold Belt. The central Kirthar Fold Belt is controlled by Pliocene to recent linked thick-skinned to thin-skinned deformation. The thick-skinned faults are most likely partially inverting rift-related normal faults. Focal mechanisms indicate dip-slip faulting on roughly N–S-trending faults with some dip angles exceeding 40∘, which are considered too steep for newly initiated thrust faults. The hinterland of the study area is primarily dominated by strike-slip faulting. The inverting faults do not break straight through the thick sedimentary column of the post-rift and flexural foreland; rather, the inversion movements link with a series of detachment horizons in the sedimentary cover. Large-scale folding and layer-parallel shortening has been observed in the northern study area. In the southern study area progressive imbrication of the former footwall of the normal fault is inferred. Due to the presence of a thick incompetent upper unit (Eocene Ghazij shales) these imbricates develop as passive roof duplexes. In both sectors the youngest footwall shortcut links with a major detachment and the deformation propagates to the deformation front, forming a large fault-propagation fold. Shortening within the studied sections is calculated to be 18 %–20 %. The central Kirthar Fold Belt is a genuine example of a hybrid thick- and thin-skinned system in which the paleogeography controls the deformation. The locations and sizes of the former rift faults control the location and orientation of the major folds. The complex tectonostratigraphy (rift, post-rift, flexural foreland) and strong E–W gradients define the mechanical stratigraphy, which in turn controls the complex thin-skinned deformation.
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Savchuk, Yu S., and A. V. Volkov. "Structural-material model of gold deposit location in the Central Kolyma region." LITHOSPHERE (Russia) 22, no. 1 (March 2, 2022): 101–17. http://dx.doi.org/10.24930/1681-9004-2022-22-1-101-117.
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Research subject. Several gold deposits, including superlarge (Natalka), large (Pavlik and Degdekan) and a number of smaller ones are located in the Central Kolyma ore region, near the Ten’kinsky deep fault. The similar position in the recumbent fault flank and confinement to upthrust-thrust plumage faults are characteristic of these objects. The differences are in the position at the different levels of the Permian section, the scale of mineralisation, and some characteristics of the material composition.Materials and methods. An analysis of the spatial characteristics of ore-bearing disturbances was carried out taking into account the change in the angles of their incidence along the section of the enclosing strata. In addition, the composition of the ores, the parameters of fluids and the regular changes in their thermodynamic characteristics were studied.Results. The additive hydrothermal column is restored, in the lower part of which the Rodionovskoye deposit is located, followed by the Degdekan and Natalka deposits, and ending in the upper part by the Pavlik deposit. The total vertical span of such a column is more than 5 km. This structural model explains the trends in the material characteristics of ore-forming fluids, reflecting the variability of the P-T characteristics from bottom to top in the hydrothermal column.Conclusions. The occurrences located directly in the zone and near the ore-supplying Ten’kinsky fault are relatively small in scale; the feathering ore-bearing reverse-thrust structures at a distance of 2–5 km from it are more favourable. Based on this model, a large-volume deposit similar to the Natalka might be located below the Pavlik deposit, which is the upper part of the column.
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Lammie, Daniel, Nadine McQuarrie, and Peter B. Sak. "Quantifying shortening across the central Appalachian fold-thrust belt, Virginia and West Virginia, USA: Reconciling grain-, outcrop-, and map-scale shortening." Geosphere 16, no. 5 (August 10, 2020): 1276–92. http://dx.doi.org/10.1130/ges02016.1.
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Abstract We present a kinematic model for the evolution of the central Appalachian fold-thrust belt (eastern United States) along a transect through the western flank of the Pennsylvania salient. New map and strain data are used to construct a balanced geologic cross section spanning 274 km from the western Great Valley of Virginia northwest across the Burning Spring anticline to the undeformed foreland of the Appalachian Plateau of West Virginia. Forty (40) oriented samples and measurements of >300 joint orientations were collected from the Appalachian Plateau and Valley and Ridge province for grain-scale bulk finite strain analysis and paleo-stress reconstruction, respectively. The central Appalachian fold-thrust belt is characterized by a passive-roof duplex, and as such, the total shortening accommodated by the sequence above the roof thrust must equal the shortening accommodated within duplexes. Earlier attempts at balancing geologic cross sections through the central Appalachians have relied upon unquantified layer-parallel shortening (LPS) to reconcile the discrepancy in restored line lengths of the imbricated carbonate sequence and mainly folded cover strata. Independent measurement of grain-scale bulk finite strain on 40 oriented samples obtained along the transect yield a transect-wide average of 10% LPS with province-wide mean values of 12% and 9% LPS for the Appalachian Plateau and Valley and Ridge, respectively. These values are used to evaluate a balanced cross section, which shows a total shortening of 56 km (18%). Measured magnitudes of LPS are highly variable, as high as 17% in the Valley and Ridge and 23% on the Appalachian Plateau. In the Valley and Ridge province, the structures that accommodate shortening vary through the stratigraphic package. In the lower Paleozoic carbonate sequences, shortening is accommodated by fault repetition (duplexing) of stratigraphic layers. In the interval between the duplex (which repeats Cambrian through Upper Ordovician strata) and Middle Devonian and younger (Permian) strata that shortened through folding and LPS, there is a zone that is both folded and faulted. Across the Appalachian Plateau, slip is transferred from the Valley and Ridge passive-roof duplex to the Appalachian Plateau along the Wills Mountain thrust. This shortening is accommodated through faulting of Upper Ordovician to Lower Devonian strata and LPS and folding within the overlying Middle Devonian through Permian rocks. The significant difference between LPS strain (10%–12%) and cross section shortening estimates (18% shortening) highlights that shortening from major subsurface faults within the central Appalachians of West Virginia is not easily linked to shortening in surface folds. Depending on length scale over which the variability in LPS can be applied, LPS can accommodate 50% to 90% of the observed shortening; other mechanisms, such as outcrop-scale shortening, are required to balance the proposed model.
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Searle, Michael P. "Structural geometry, style and timing of deformation in the Hawasina Window, Al Jabal al Akhdar and Saih Hatat culminations, Oman Mountains." GeoArabia 12, no. 2 (April 1, 2007): 99–130. http://dx.doi.org/10.2113/geoarabia120299.
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ABSTRACT The Al Jabal al Akhdar and Saih Hatat culminations in the central Oman Mountains expose the complete mid-Permian to Late Cretaceous (Cenomanian) passive shelf and margin carbonate sequence beneath the allochtonous slope (Sumeini Group), basin (Hawasina complex), distal ocean-trench (Haybi complex) facies rocks, and the Semail ophiolite thrust sheets that were emplaced from NE to SW during the Late Cretaceous. Reconstruction of the pre-thrust sequences shows that time-equivalent rocks occur in successively stacked thrust sheets from shelf to slope to basin. The Al Jabal al Akhdar structure is a 60 km wavelength anticline plunging to the northwest beneath the Hawasina Window and with a fold axis that curves from WNW-ESE (Jabal Shams) to NNE-SSW (Jabal Nakhl). The structure shows little internal deformation except for minor intra-formational thrust duplexing within the Cretaceous shelf stratigraphy along the northern margin. The upper structural boundaries around the flanks of the shelf carbonate culminations have been re-activated as late stage normal faults. The Semail thrust formed a passive roof fault during late-stage culmination of al Al Jabal al Akhdar such that the ophiolite rests directly on Wasia Formation top-shelf with the entire Sumeini, Hawasina and Haybi thrust sheets displaced around the margins. NE-directed backthrusting and intense folding in the northern part of the Hawasina Window affects all allochtonous units and is related to a steep ramp in the Late Cretaceous shelf margin at depth. The Saih Hatat culmination is another 40 km half-wavelength anticline in the central Oman Mountains, but shows extreme deformation in the form of recumbent folds, sheath folds with NNE-trending axes and thrusting along the northern margin. High-pressure carpholite, blueschist and eclogite facies rocks are exposed at successively deeper structural levels, separated by high-strain normal sense shear zones. There is no evidence for a separate ‘North Muscat microplate’ or an intra-continental subduction zone, as previously proposed; all high-pressure units can be restored to show their pre-deformation palaeographic positions along the northern margin of the Arabian Plate. Both Al Jabal al Akhdar and Saih Hatat are Late Cretaceous culminations, folded after obduction of the Hawasina, Haybi and Semail ophiolite thrust sheets from northeast to southwest during the period Turonian to Campanian-Lower Maastrichtian. Maximum compressive stress along the central Oman Mountains was oriented NE-SW, parallel to the ophiolite emplacement direction, but a second compressive stress axis was oriented WNW-ESE, either concurrently or slightly later in time, resulting in a dome and basin structural geometry. The biaxial fracture pattern in the foreland, southwest of the Oman Mountains could be explained as a result of the WNW-directed emplacement of the Masirah ophiolite belt and Batain mélange during the Campanian-early Palaeocene. Both Al Jabal al Akhdar and Saih Hatat were positive topographic features at the end of the Cretaceous with Upper Maastrichtian and Palaeogene sediments onlapping both flanks. In Jabal Abiad, these Palaeogene sediments have been uplifted by at least 2 km since the Late Miocene-Early Oligocene associated with minor NNE-SSW compression. Tertiary shortening, folding and thrusting increases to the north in the Musandam peninsula where the first effects of the Arabian Plate-Eurasian Plate (Zagros belt) continent-continent collision are seen.
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Ali, Mohammed Y., David J. W. Cooper, Michael P. Searle, and Ali Al-Lazki. "Origin of gypsiferous intrusions in the Hawasina Window, Oman Mountains: Implications from structural and gravity investigations." GeoArabia 19, no. 2 (April 1, 2014): 107–32. http://dx.doi.org/10.2113/geoarabia1902107.
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ABSTRACT Gypsiferous intrusions are exposed in road-cuts in the south-central Hawasina Window in the central Oman Mountains. They are located at lower structural levels in the allochthonous Hawasina Complex and lie along faults that cut Upper Cretaceous structures related to the obduction of the Semail Ophiolite and Hawasina Complex deep-water sediments onto the Arabian Plate. The intrusions form gypsiferous pods that are up to 200 m long, in which the gypsum occurs as a dark, fine-grained matrix that contains a pervasive network of anastomosing veins of gypsum and anhydrite. The intrusions contain abundant sub-angular to sub-rounded litharenites, and less common fragments of chert and fine-grained limestone. Although these clast types are undated, their petrographic characteristics suggest they originate from the local Hawasina (Hamrat Duru Group) country rock. Very well-rounded pebbles and cobbles of feldspathic litharenites, some of which show a well-developed cleavage, and rarer cobbles of well-rounded vein quartz appear to have come from the basement. Gravity investigations indicate salt diapirs are not present beneath the Hawasina Window. Instead, the gypsiferous intrusions are interpreted as having been brought up from depth during compression to form disconnected pods along deep-rooted faults, bringing with them small amounts of the basement country rock. Strontium isotope analysis and regional considerations, in particular the distribution, age and nature of other evaporite units on the eastern Arabian Plate, suggest the gypsum may have its origins in the Neoproterozoic (Ediacaran) to lower Cambrian Ara Group evaporites, perhaps from a previously unknown extension of the Fahud Salt Basin beneath the Hawasina thrust sheets.
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Dinc, Gulce, Jean-Paul Callot, and Jean-Claude Ringenbach. "Shale mobility: From salt-like shale flow to fluid mobilization in gravity-driven deformation, the late Albian–Turonian White Pointer Delta (Ceduna Subbasin, Great Bight, Australia)." Geology 51, no. 2 (December 20, 2022): 174–78. http://dx.doi.org/10.1130/g050611.1.
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Abstract Large offshore depocenters above a weak detachment level (either salt or shale) can undergo gravity spreading and/or gliding. The gravitational systems (e.g., gliding deltas) are classically composed of an updip domain affected by extensional listric normal faults and a downdip domain affected by toe thrusts. While the role of salt in such systems is a classic tectonic process, the role and mechanical behavior of mobile shale levels in shale-prone gravity-driven systems are increasingly questioned. A three-dimensional seismic data set in the Ceduna Subbasin (Australia) displays the late Albian–Turonian White Pointer Delta (WPD) as having an unusual diversity of shale-cored structures. The early flow of shale resulted in depocenters showing wedges, internal unconformities, and shale diapirs and ridges, while fluidization of shales underneath a significant burial resulted in mud volcanism, secondary radial fault sets, and collapse features beneath the Campanian–Maastrichtian Hammerhead Delta, which lies above the WPD. Massive shale mobilization, together with downdip shortening and distal margin uplift, localized a major thrust in the core of the basin, ending the downward-propagating failure of the WPD. Mobilization of thick shale intervals, either as salt-like flow or mud volcanism, appears to have been a key process in the deformation, which should be considered at large scale for worldwide gravity-driven deformation systems.
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Sellmann, Schirin, Mark Quigley, Brendan Duffy, and Ian Moffat. "Ground Penetrating Radar of Neotectonic Folds and Faults in South-Central Australia: Evolution of the Shallow Geophysical Structure of Fault-Propagation Folds with Increasing Strain." Geosciences 12, no. 11 (October 26, 2022): 395. http://dx.doi.org/10.3390/geosciences12110395.
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Using ground penetrating radar (GPR) we investigate the near surface (~0–10 m depth) geophysical structure of neotectonic fault-propagation folds and thrust faults in south-central Australia in varying stages of fold and fault growth. Variations in neotectonic fold scarp heights are interpreted to reflect variations in accumulated slip on the underlying reverse faults. Fold scarps on the Nullarbor and Roe Plains are characterized by broad, asymmetric morphologies with vertical displacements of ~5 to ~40 m distributed over 1 to 2 km widths (~0.5 to ~4 m per 100 m). Within increasing scarp height there is an increase in the frequency and spatial density of strong reflector packages in the hanging wall that are attributed to material contrasts imposed by co-seismic fracturing and associated lithological and weathering variations. No evidence for discrete faulting is found at scarp heights up to 40 m (maximum relief of 4 m per 100 m). Where the principal slip zone of a fault ruptures to the surface, scarp morphologies are characterized by steep gradients (ca. 10 m per 100 m). Discrete faulting is imaged in GPR as structural lineaments, abrupt changes in the thickness of reflector packages with variations of amplitude, and/or hyperbolic diffraction packages indicative of the disturbance of reflector packages. Geophysical imaging of subtle changes in the shallow geological structure during growth of fault-propagation folds can be conducted using GPR informing the identification of locations for invasive investigations (e.g., trenching).
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Arnous, Ahmad, Martin Zeckra, Agostina Venerdini, Patricia Alvarado, Ramón Arrowsmith, Julien Guillemoteau, Angela Landgraf, Antonio Gutiérrez, and Manfred R. Strecker. "Neotectonic Activity in the Low-Strain Broken Foreland (Santa Bárbara System) of the North-Western Argentinean Andes (26°S)." Lithosphere 2020, no. 1 (October 28, 2020): 1–25. http://dx.doi.org/10.2113/2020/8888588.
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Abstract Uplift in the broken Andean foreland of the Argentine Santa Bárbara System (SBS) is associated with the contractional reactivation of basement anisotropies, similar to those reported from the thick-skinned Cretaceous-Eocene Laramide province of North America. Fault scarps, deformed Quaternary deposits and landforms, disrupted drainage patterns, and medium-sized earthquakes within the SBS suggest that movement along these structures may be a recurring phenomenon, with yet to be defined repeat intervals and rupture lengths. In contrast to the Subandes thrust belt farther north, where eastward-migrating deformation has generated a well-defined thrust front, the SBS records spatiotemporally disparate deformation along structures that are only known to the first order. We present herein the results of geomorphic desktop analyses, structural field observations, and 2D electrical resistivity tomography and seismic-refraction tomography surveys and an interpretation of seismic reflection profiles across suspected fault scarps in the sedimentary basins adjacent to the Candelaria Range (CR) basement uplift, in the south-central part of the SBS. Our analysis in the CR piedmont areas reveals consistency between the results of near-surface electrical resistivity and seismic-refraction tomography surveys, the locations of prominent fault scarps, and structural geometries at greater depth imaged by seismic reflection data. We suggest that this deformation is driven by deep-seated blind thrusting beneath the CR and associated regional warping, while shortening involving Mesozoic and Cenozoic sedimentary strata in the adjacent basins was accommodated by layer-parallel folding and flexural-slip faults that cut through Quaternary landforms and deposits at the surface.
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Maduna, Nombuso G., Musa S. D. Manzi, Zubair Jinnah, and Julie E. Bourdeau. "Strato-structural evolution of the deep-water Orange Basin: constraints from 3D reflection seismic data." Solid Earth 13, no. 11 (November 18, 2022): 1755–80. http://dx.doi.org/10.5194/se-13-1755-2022.
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Abstract. Deep-water fold-and-thrust belt (DWFTB) systems are gravity-driven collapse structures often found in passive margin settings and are comprised of a linked up-dip extensional domain, central transitional/translational domain, and down-dip compressional domain. Many Late Cretaceous DWFTB systems occur along the SW African passive margin with multiple, over-pressurized, seaward-dipping shale detachment surfaces accommodating gravitational slip. In this study we use 3D reflection seismic data to constrain the strato-structural evolution of the translational and compressional domains of a Late Cretaceous DWFTB system and the overlying Cenozoic deposits in the Orange Basin, South Africa. The stratigraphy and structure of the Late Cretaceous DWFTB system is shown to have controlled fundamental sedimentary processes and the stability of the evolving margin. The compressional domain exhibits large-scale landward-dipping DWFTBs with thrust faults detaching the main Turonian shale detachment surface at depth and terminating at the early Campanian surface. A major ∼ 7 km wide seafloor slump scar reflecting margin instability occurs directly above a syncline of the same width from the buried DWFTB system's compressional domain. The translational domain is imaged as a complex region displaying overprinted features of both extensional and compressional tectonics with the downslope translation of sediment comprising listric normal and then thrust and oblique-slip faults distally. Thrust sheets are segmented along strike by extensive oblique-slip faults which extend from the translational domain into the down-dip compressional domain. Smaller, localized fold-and-thrust belts are found directly below the kilometre-scale DWFTB system in the down-dip compressional domain detaching a lower, Albian shale detachment surface which corresponds to an older gravitational collapse. The upward propagation of normal and oblique-slip faults with progressive sedimentation is hindered by the Oligocene or Miocene stratigraphic markers corresponding to mass erosional processes in the Cenozoic. A large (∼ 2.3 km wide), roughly slope-perpendicular Oligocene submarine canyon formed by turbidity currents is attributed to a major sea-level fall at ∼ 30 Ma. Oceanographic circulation is shown to have held a significant control on the deposition of mid-Miocene to present-day sedimentary sequences. Between 1200 to 1500 m water depths along the upper continental slope well-preserved extensive slope-parallel, sinusoidal channel-like features occur on the Miocene stratigraphic marker. The channels are confined within a ∼ 14 km wide zone at the interface of the upper northward-flowing Antarctic Intermediate Water (AAIW) and deeper southward-flowing North Atlantic Deep Water (NADW) currents. The erosive interaction of these oppositely flowing bottom currents combined with the effects of the Benguela Upwelling System (BUS), all of which formed or intensified at ∼ 11 Ma, are responsible for the creation and preservation of the extensive slope-parallel channels. This study shows the difference in structural styles of the translational and compressional domains of a Late Cretaceous DWFTB system and the processes responsible for mass-scale erosion in the Cenozoic.
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Nikiforova, Zinaida. "Mineralogical Criteria for the Prediction of Gold Mineralization in the Structures of the Siberian Craton." Minerals 12, no. 6 (May 30, 2022): 694. http://dx.doi.org/10.3390/min12060694.
Full textAbstract:
Generalization of the results of the study of placer gold and the mechanisms of its distribution in the east of the Siberian Platform made it possible for the first time to reveal that the ore sources of gold-bearing placers were mainly mineralization of the gold-sulfide formation formed under the influence of hydrothermal metasomatic processes occurred in deep fault zones. It is determined that the gold-bearing hydrothermal-metasomatic formations of the gold-sulfide rock formation are amagmatic, near-surface, low-temperature and spatially confined to deep faults. These formations are widespread in terrigenous-carbonate strata and sand deposits of PZ-MZ age and are observed in the zones of brecciation, silicification, and ferruginization. The analysis of the mechanisms of distribution of hydrothermal-metasomatic gold-bearing formations in the east of the Siberian Platform, based on previously conducted research of predecessors and our field observations, allowed us to establish the following. In the northeast, hydrothermal-metasomatic formations occur in the field of development of the Zhigansky fault, the Molodo-Popigai and Anabar-Eekite fault system, in the central part of the east of the Siberian Platform, the Vilyui paleorift (Kempendyai dislocations), and in the southeast in the Baikal-Patom thrust belt in ancient faults (Bappagai, Khorinsky, etc.). Metasomatites of hydrothermal origin form extended narrow formations along ancient faults activated in the Mesozoic, as well as conformable deposits in the Vendian, Cambrian carbonate strata, Jurassic and Cretaceous sandstones. It is proved that these formations are amagmatic and are not related to the widespread magmatism of the basic composition, which is confirmed by the homogenous mineral composition of metasomatites, independent of the composition of magmatic bodies spatially located with them. Zones of metasomatites with gold mineralization contain Au from 0.5 to 3.0 g/t, and in isolated cases up to 24–32 g/t. Gold is represented from finely-dispersed to visible fine, with a size from 0.01 to 0.5 mm or more. It is known that hydrothermal-metasomatic processes on the territory of Central Aldan contributed to the formation of large deposits such as Kuranakh, Tabornoye and others. It is possible that the identified gold-ore metasomatites, developed along the zones of regional faults and not confined to magmatic formations, widely occurred both in the northeast and in the southeast of the Siberian Platform, represent a huge metallogenic potential.
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Affinati, Suzanne Craddock, Thomas D. Hoisch, Michael L. Wells, and Jeffrey D. Vervoort. "Pressure-temperature-time paths from the Funeral Mountains, California, reveal Jurassic retroarc underthrusting during early Sevier orogenesis." GSA Bulletin 132, no. 5-6 (September 17, 2019): 1047–65. http://dx.doi.org/10.1130/b35095.1.
Full textAbstract:
Abstract New metamorphic pressure-temperature (P-T) paths and Lu-Hf garnet ages reveal a temporal correlation between Middle to Late Jurassic retroarc underthrusting and arc magmatism in southwestern North America. P-T paths were determined for 12 garnet porphyroblasts from six samples from the Chloride Cliff area of the Funeral Mountains in southeastern California. The composite path shows a pressure increase from 4.2 to 6.5 kbar as temperature increased from 550 to 575 °C, followed by a pressure decrease to 5.1 kbar during a further increase in temperature to 590 °C. Lu-Hf garnet ages from a pelitic schist (167.3 ± 0.7 Ma) and a garnet amphibolite (165.1 ± 9.2 Ma) place these P-T paths in the Middle Jurassic. We interpret the near-isothermal pressure increase portion of the P-T path to have developed during thrust-related burial, similar to lower grade rocks at Indian Pass, 8 km to the southeast, where garnet P-T paths show a pressure increase dated by the Lu-Hf method at 158.2 ± 2.6 Ma. We interpret the pressure decrease portion of the composite P-T path from the Chloride Cliff area to reflect exhumation contemporaneous with cooling in the Indian Pass area documented from muscovite 40Ar/39Ar step-heating ages of 152.6 ± 1.4 and 146 ± 1.1 Ma. The conditions and timing of metamorphism determined for the Indian Pass and Chloride Cliff areas, and isogradic surfaces that cut across stratigraphy, support the interpretation that the strata were dipping moderately NW during metamorphism, parallel to the thrust ramp that buried the rocks. Burial likely resulted from top-SE motion along the Funeral thrust, which was later reactivated as a low-angle normal fault with opposite motion to become the currently exposed Boundary Canyon detachment that was responsible for Miocene and possibly older exhumation. The part of the burial history captured by garnet growth occurred ∼6 m.y. before the 161 Ma peak of high-flux magmatism in the arc. Burial was contemporaneous with metamorphic ages from the western Sierra Nevada metamorphic belt, with the possible timing of accretion of arc terranes in northern California, and with the initiation of Franciscan subduction. Burial ages are also similar in timing with generally E-W crustal shortening in the retroarc that produced the East Sierra thrust system, the Luning-Fencemaker fold and thrust belt, the possible early history of the Central Nevada thrust belt, and the western thrusts of the southern Sevier belt. The timing of tectonic burial documented in this study and of high-flux magmatism in the arc supports the interpretation that the development of a coherent arc-trench system in the Early Jurassic resulted in the underthrusting of melt-fertile material beneath the arc along west- to northwest-dipping faults such as the Funeral thrust in the Jurassic, which penetrated the basement to the west as well as the roots of the magmatic arc, leading to increased magmatism.
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Thorwart, Martin, Anke Dannowski, Ingo Grevemeyer, Dietrich Lange, Heidrun Kopp, Florian Petersen, Wayne C. Crawford, and Anne Paul. "Basin inversion: reactivated rift structures in the central Ligurian Sea revealed using ocean bottom seismometers." Solid Earth 12, no. 11 (November 12, 2021): 2553–71. http://dx.doi.org/10.5194/se-12-2553-2021.
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Abstract. The northern margin of the Ligurian Basin shows notable seismicity at the Alpine front, including frequent magnitude 4 events. Seismicity decreases offshore towards the Basin centre and Corsica, revealing a diffuse distribution of low-magnitude earthquakes. We analyse data of the amphibious AlpArray seismic network with focus on the offshore component, the AlpArray ocean bottom seismometer (OBS) network, consisting of 24 broadband OBSs deployed for 8 months, to reveal the seismicity and depth distribution of micro-earthquakes beneath the Ligurian Sea. Two clusters occurred between ∼ 10 km to ∼ 16 km depth below the sea surface, within the lower crust and uppermost mantle. Thrust faulting focal mechanisms indicate compression and an inversion of the Ligurian Basin, which is an abandoned Oligocene–Miocene rift basin. The basin inversion is suggested to be related to the Africa–Europe plate convergence. The locations and focal mechanisms of seismicity suggest reactivation of pre-existing rift-related structures. Slightly different striking directions of presumed rift-related faults in the basin centre compared to faults further east and hence away from the rift basin may reflect the counter-clockwise rotation of the Corsica–Sardinia block. High mantle S-wave velocities and a low Vp/Vs ratio support the hypothesis of strengthening of crust and uppermost mantle during the Oligocene–Miocene rifting-related extension and thinning of continental crust.
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Nakano, O., M. Endo, E. Ishii, and H. Watanabe. "A new interpretation of geological structure of Tempoku Coal Field by crooked-line survey." Exploration Geophysics 23, no. 2 (1992): 241. http://dx.doi.org/10.1071/eg992241.
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Tempoku Coal Field is located in the northern area of Japan's northern island, Hokkaido. Here the exploration target, the Soya Coal-Bearing Formation, is of Tertiary age overlying Cretaceous basement. The regional structure of the area is characterised by a series of synclines and anticlines trending north-northwest, with several reverse faults. A suite of surveys was carried out in 1991, in the Asajino area in the central part of the coal field. The study included drilling, vertical seismic profiling, and trenching, as well as a reflection seismic survey with the crooked-line method, which is the subject of this paper. The crooked-line method was adopted because of the mountainous terrain of the area. The seismic lines were laid out along existing tracks and valleys. The main geological structure of the area had long been considered to be a monotonous series of folds. However, the 1991 survey revealed a large-scale thrust-related structure in the main coal seams, which presented clear reflectors. Together with the data from other surveys, a reinterpretation of the structure of the Asajino area is proposed.
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Wu, Chen, Jie Li, and Lin Ding. "Low-temperature thermochronology constraints on the evolution of the Eastern Kunlun Range, northern Tibetan Plateau." Geosphere 17, no. 4 (June 9, 2021): 1193–213. http://dx.doi.org/10.1130/ges02358.1.
Full textAbstract:
Abstract Signals of uplift and deformation across the Tibetan Plateau associated with the Cenozoic India-Asia collision can be used to test debated deformation mechanism(s) and the growth history of the plateau. The spatio-temporal evolution of the Eastern Kunlun Range in northern Tibet provides a window for understanding the intracontinental tectonic evolution of the region. The Eastern Kunlun Range exposes the Cenozoic Kunlun left-slip fault and kinematically linked thrust belts. In this contribution, integrated field observations and apatite fission-track thermochronology were conducted to constrain the initiation ages of localized thrust faults and the exhumation history of the Eastern Kunlun Range. Our analyses reveal four stages of cooling of the Eastern Kunlun Range. We relate these four stages to the following interpreted tectonic evolution: (1) an initial period of early Cretaceous cooling and slow exhumation over the early Cenozoic, which is associated with the formation of a regional unconformity observed between Cretaceous strata and early Cenozoic sediments; (2) rapid Oligocene cooling that occurred at the eastern domain of the Eastern Kunlun Range related to the southern Qaidam thrusts; (3) extensive rapid cooling since the early-middle Miocene in most of the eastern-central domains and significant uplift of the entire range; and (4) a final pulse of rapid late Miocene-to-present cooling associated with the initiation of the Kunlun left-slip fault and dip-slip shortening at the western and eastern termination of the left-slip fault. Early Cenozoic deformation was distributed along the northern extent of the Tibetan Plateau, and overprinting out-of-sequence deformation migrated back to the south with the initiation of Miocene-to-present deformation in the Eastern Kunlun Range.
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Suzuki, Yasumoto. "Historical Review of the Study on Intermediate and Deep Earthquakes." Earth Sciences History 26, no. 2 (January 1, 2007): 371–82. http://dx.doi.org/10.17704/eshi.26.2.2x665t8854776287.
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The deep earthquake was first detected by Herbert Hall Turner in 1922, and confirmed by Wadati in 1928, Scrase in 1931 and Stechschulte in 1932. Wadati demonstrated the inclined intermediatedeep earthquake zone under the Japanese islands and neighborhoods in 1935. Such earthquake zones were found in other areas in the circum-Pacific regions. Benioff (1954) classified them morphologically into two types, and ascribed them to thrusts, following Suess's idea. Richter (1958) critisized the thrust hypothesis, as most of deep earthquakes were not accompanied by reverse faults, but by normal faults which were deduced from the initial motion of P-waves. Gutenberg and Richter (1954) pointed out the regular arrangement of geology and geophysical phenomena from an outer oceanic trench to an inner belt of deep earthquakes in the circum-Pacific region. Wadati (1928) demonstrated the vertical relation between shallow earthquakes and deep ones in central Honshu of the Japanese islands. Suzuki (1975) showed a similar relationship in northeast Honshu, and suggested the role of vertical deep faults. Bemmelen (1972) attributed the inclined intermediate-deep earthquake zone to the upward driving force derived from the deep mantle. Suzuki et al. (1978) tried a simulation experiment using the finite element method to propagate the inclined intermediate-deep earthquake zone by the differential vertical displacement at the base of mantle, and the result was compared with the earthquake-generating stresses.
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Uysal, I. Tonguç, Claudio Delle Piane, Andrew James Todd, and Horst Zwingmann. "Precambrian faulting episodes and insights into the tectonothermal history of north Australia: microstructural evidence and K–Ar, <sup>40</sup>Ar–<sup>39</sup>Ar, and Rb–Sr dating of syntectonic illite from the intracratonic Millungera Basin." Solid Earth 11, no. 5 (September 4, 2020): 1653–79. http://dx.doi.org/10.5194/se-11-1653-2020.
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Abstract. Australian terranes concealed beneath Mesozoic cover record complex Precambrian tectonic histories involving a successive development of several Proterozoic to Palaeozoic orogenic systems. This study presents an integrated approach combining K–Ar, 40Ar–39Ar, and Rb–Sr geochronologies of Precambrian authigenic illites from the recently discovered Millungera Basin in north-central Australia. Brittle deformation and repeated fault activity are evident from the sampled cores and their microstructures, probably associated with the large-scale faults inferred from interpretations of seismic surveys. Rb–Sr isochron, 40Ar–39Ar total gas, and K–Ar ages are largely consistent in indicating late Mesoproterozoic and early Proterozoic episodes (∼1115±26, ∼ 1070±25, ∼1040±24, ∼1000±23, and ∼905±21 Ma) of active tectonics in north-central Australia. K–Ar results show that illites from fault gouges and authigenic matrix illites in undeformed adjacent sandstones precipitated contemporaneously, indicating that advection of tectonically mobilized fluids extended into the undeformed wall rocks above or below the fracture and shear (fault gouge) zones. Isotopic age data clearly indicate a Mesoproterozoic minimum age for the Millungera Basin and thus previously unrecorded late Mesoproterozoic–early Neoproterozoic tectonic events in north-central Australia. This study provides insight into the enigmatic time–space distribution of Precambrian tectonic zones in central Australia, which are responsible for the formation of a number of sedimentary basins with significant energy and mineral resources.
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Andrew, Joseph E. "Geologic map of southern Panamint Valley, southern Panamint Range, and central Slate Range, California, USA." Geosphere 18, no. 2 (March 10, 2022): 726–27. http://dx.doi.org/10.1130/ges02342.1.
Full textAbstract:
Abstract This detailed geologic map and supplemental digital data set1 examine and demonstrate the complex deformational history and reactivation relationships of the southern Panamint Valley area (California, USA), from active transtension of the Walker Lane belt, Miocene extension of the Basin and Range, multiple Mesozoic events related to subduction, and Neoproterozoic extension. This collection of map data focuses on the geometry, kinematics, and relative timing of deformation to understand the deformation history and effects of structural reactivation. Andrew and Walker (2009) used these geologic mapping data to palinspastically restore the Fish Canyon area of the Slate Range to overlapping the western Panamint Range at Goler Wash. Neogene extension and subsequent dextral transtension has created a complex network of faults via partial reactivation of Mesozoic and Neoproterozoic structures and has separated the Slate Range from the Panamint Range. The Neogene fault system changes from south to north from dextral strike-slip along the southern Panamint Valley fault to oblique normal slip along the Emigrant fault at a triple junction with the sinistral-oblique normal Manly Pass fault. The Mesozoic deformation history is different in the two ranges across Panamint Valley. The Slate Range was the hanging wall to Jurassic and Cretaceous contractional deformation; this same deformation in the Panamint Range to the east was localized along the western range flank with the majority of the Panamint Range thus being in the footwall to Mesozoic contraction. The western Panamint Range preserves migmatitic fabrics and deformation due to Jurassic contraction and plutonism. The Goldbug fault, along the western Panamint Range, places Paleoproterozoic to Mesoproterozoic rocks over Neoproterozoic to Cretaceous rocks. Jurassic contraction has top-to-the-northeast relative transport and the more discrete Cretaceous thrust faulting in the Panamint Range has top-to-the-east transport. The Butte Valley fault, previously recognized farther north of the map area in the Panamint Range, cuts Late Jurassic rocks and structures. Neoproterozoic to Cambrian sedimentary rocks with top-to-the-northeast contractional deformation occur as relative down-dropped block exposed east of the Butte Valley fault. The Butte Valley fault continues southward and is then deflected by Late Cretaceous thrust faulting on the Goldbug fault. Neoproterozoic deformation is more difficult to discern but is hypothesized to relate to abundant olistostromes mapped within the Kingston Peak Formation in the Panamint Range (i.e., Prave, 1999). This detailed geologic mapping and collection of structural data for the rocks in the southern Panamint Valley area were created using digital in-the-field geographic information systems software running on a field-hardened laptop computer. This map is a simplification of detailed geologic mapping data collected at 1:6000 scales and reduced to 1:20000 scale. Structural data includes kinematic and relative timing of deformation information.
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Bishop, D. J., and G. W. O'Brien. "A MULTI-DISCIPLINARY APPROACH TO DEFINITION AND CHARACTERISATION OF CARBONATE SHOALS, SHALLOW GAS ACCUMULATIONS AND RELATED COMPLEX NEAR-SURFACE SEDIMENTARY STRUCTURES IN THE TIMOR SEA." APPEA Journal 38, no. 1 (1998): 93. http://dx.doi.org/10.1071/aj97005.
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A major exploration program is being undertaken by the AC/P16 Joint Venture in the central Timor Sea, northwestern Australia. Its safe and successful execution is critically dependant on the early definition and characterisation of both the numerous carbonate shoals in the area and the complex bathymetry. This was accomplished via the acquisition of environmental, high-resolution bathymetric, 2D and 3D seismic and airborne laser fluorosensor (ALF) data. Multi-disciplinary integration and analysis of these data have enabled mapping and 3D visualisation of the shoals, and the creation of a 3D velocity model for depth conversion. Seismic amplitude anomalies and chaotic seismic reflectors, which increase in areal extent toward the sea floor, have been interpreted as being due to shallow gas. These gas accumulations are also associated with soft-sediment gravity slides in the shallow sub-surface which exhibit thrust imbrication in the contractional toes and are linked to listric extensional faults. The high resolution bathymetric data have provided images of a disturbed sea floor in several of the areas which are affected by shallow gas: craters, troughs, ridges and mounds can be explained by the localised venting of gas at the sea floor. These gas accumulations are located above basin-scale faults, which are inferred to provide migration paths from more deeply buried source rocks. ALF anomalies mapped at the sea surface, and sea floor grab samples containing petrogenic hydrocarbons, also provide evidence that hydrocarbons are presently leaking from the sea floor.
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Carr, Sharon D. "The southern Omineca Belt, British Columbia: new perspectives from the Lithoprobe Geoscience Program." Canadian Journal of Earth Sciences 32, no. 10 (October 1, 1995): 1720–39. http://dx.doi.org/10.1139/e95-135.
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Geological, isotopic, and geochronology studies carried out by university and government researchers, concurrently with the Lithoprobe program, have greatly refined our understanding of the regional geology, crustal structure, and tectonics of the Omineca Belt. Sound correlations have been established between surface geology and seismic reflection data. Cretaceous–Eocene thrust faults that are imaged in the subsurface in the Shuswap complex may be part of a break-forward thrust system that feeds into the Purcell Anticlinorium and the Foreland Belt. The Monashee décollement is the western continuation of the sole thrust beneath the Foreland Belt and provides a means of linking shortening across the entire orogen. The thermal peak of metamorphism in the central and southern Shuswap complex is now known to have occurred in the Late Cretaceous–Paleogene in contrast with earlier held views. North American basement rocks are now known to extend beneath the eastern half of the Canadian Cordillera. Geochronology studies have revealed Early Proterozoic and Late Cretaceous–Eocene metamorphism in basement rocks of the Monashee complex, and suggest that these rocks were located to the east of the metamorphic front throughout the Jurassic and Early Cretaceous. Anatectic peraluminous granites were produced in the Shuswap complex between 135 and 52 Ma in response to pulses of crustal thickening and heating, and in some cases served to localize Eocene extensional shear zones and to transfer extensional displacement from one shear zone to another. A flat Moho and other seismic reflection data are consistent with interpretations of lower crustal flow to balance early Tertiary extension in the upper crust. Crustal-scale extension and the Slocan Lake fault zone provided the source and setting for Ag–Pb–Zn–Au mineralization in the Nelson–Silverton area.
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Cooper, David J. W., Mohammed Y. Ali, Michael P. Searle, and Ali I. Al-Lazki. "Salt intrusions in Jabal Qumayrah, northern Oman Mountains: Implications from structural and gravity investigations." GeoArabia 18, no. 2 (April 1, 2013): 141–76. http://dx.doi.org/10.2113/geoarabia1802141.
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ABSTRACT The Jabal Qumayrah area, 50 km ESE of Al Ain and Buraimi, preserves a culmination of Jurassic and Cretaceous continental slope deposits (Sumeini Group) that was emplaced during the Late Cretaceous onto the Oman margin with other Neo-Tethyan units and the Semail Ophiolite. Almost uniquely in the Oman Mountains, Jabal Qumayrah also contains outcrops of gypsum and anhydrite that occur as a central complex from which laterally discontinuous linear and arcuate outcrops extend up to 4 km to the northwest and south. The gypsum and anhydrite bodies contain sedimentary clasts and rafts, which show close affinities with the local Sumeini Group host rock. There are no sedimentary features that indicate the evaporites were deposited in situ, either as part of, or unconformably overlying the Sumeini Group. Boundaries with the host rock are either high-angle faults or steep and intrusive, with significant dissolution of host rock limestones. Two gravity transects across the area indicate the areas of gypsum and anhydrite lie on a gravity low, compatible with an elongated, high-level body concentrated along the main N-S axis of the Jabal Qumayrah dome. Taken together, these features point towards an intrusive origin for the evaporite bodies in Jabal Qumayrah. While the sub-surface is poorly constrained, the central complex is interpreted as representing the deeply weathered top of a salt diapir, whose emplacement had a strong tectonic fault-driven component. The smaller, discontinuous exposures to the northwest and south are interpreted as pods of gypsum and anhydrite that were injected along faults. The absence of other evaporite minerals, in particular halite, is attributed to deep weathering and dissolution similar to that seen at the surface-piercing salt domes of the Ghaba Salt Basin in central Oman. In the absence of unequivocal dating evidence, the regional context suggests the intrusion may be derived from evaporites within the Ediacaran–Early Cambrian Ara Group. These form large deposits in the Fahud and Ghaba salt basins to the southwest of the Oman Mountains and the Hormuz Salt Basin to the north. The Jabal Qumayrah area may represent another, smaller basin or an extension to the Fahud Basin. The Jabal Qumayrah intrusion does not contain rafts of Ara Group limestones, which characterise the salt diapirs of the Ghaba Salt Basin, but this is not considered diagnostic. Other regional evaporite units of Permian to Jurassic ages do not extend into the area of the Oman Mountains and are thus unlikely potential sources. There is no evidence to suggest the Jabal Qumayrah culmination was thrust over Cenozoic evaporites and this potential source is also discounted. The timing of intrusion is constrained by the boundary faults, which cut across and thus post-date structures related to the Late Cretaceous emplacement of the Sumeini Group of Jabal Qumayrah. There is no evidence of any movement since the unroofing and exposure of the salt intrusion, which began in the Late Miocene.
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Hansen, Torsten Hundebøl, Ole Rønø Clausen, and Katrine Juul Andresen. "Thick- and thin-skinned basin inversion in the Danish Central Graben, North Sea – the role of deep evaporites and basement kinematics." Solid Earth 12, no. 8 (August 4, 2021): 1719–47. http://dx.doi.org/10.5194/se-12-1719-2021.
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Abstract. Using borehole-constrained 3D reflection seismic data, we analyse the importance of sub-salt, salt, and supra-salt deformation in controlling the geometries and the kinematics of inverted structures in the Danish Central Graben. The Danish Central Graben is part of the failed Late Jurassic North Sea rift. Later tectonic shortening caused mild basin inversion during the Late Cretaceous and Paleogene. Where mobile Zechstein evaporites are present, they have played a significant role in the structural evolution of the Danish Central Graben since the Triassic. Within the study area, Jurassic rifting generated two major W- to SW-dipping basement faults (the Coffee Soil Fault and the Gorm–Tyra Fault) with several kilometres of normal offset and associated block rotation. The Coffee Soil Fault system delineates the eastern boundary of the rift basins, and within its hanging wall a broad zone is characterized by late Mesozoic to early Paleogene shortening and relative uplift. Buttressed growth folds in the immediate hanging wall of the Coffee Soil Fault indicate thick-skinned inversion, i.e. coupled deformation between the basement and cover units. The western boundary of the inverted zone follows the westward pinch-out of the Zechstein salt. Here, thin-skinned folds and faults sole out into Zechstein units dipping into the half-graben. The most pronounced inversion structures occur directly above and in prolongation of salt anticlines and rollers that localized shortening in the cover above. With no physical links to underlying basement faults (if present), we balance thin-skinned shortening to the sub-salt basement via a triangle zone concept. This implies that thin Zechstein units on the dipping half-graben floor formed thrust detachments during inversion while basement shortening was mainly accommodated by reactivation of the major rift faults further east. Disseminated deformation (i.e. “ductile” at seismic scales) accounts for thin-skinned shortening of the cover units where such a detachment did not develop. The observed structural styles are discussed in relation to those found in other inverted basins in the North Sea Basin and to those produced from physical model experiments. Our results indicate that Zechstein units imposed a strong control on structural styles and kinematics not only during rift-related extension but also during basin inversion in large parts of the Danish Central Graben. Reactivated thin-skinned faults soling out into thin Triassic evaporite units within the carapace above Zechstein salt structures illustrate that even thin evaporite units may contribute to defining structures during tectonic extension and shortening. We thus provide an updated and dedicated case study of post-rift basin inversion, which takes into account the mechanical heterogeneity of sub-salt basement, salt, and supra-salt cover, including multiple evaporite units of which the Zechstein is the most important.
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Klaper, Eva M. "The mid-Paleozoic deformation in the Hazen fold belt, Ellesmere Island, Arctic Canada." Canadian Journal of Earth Sciences 27, no. 10 (October 1, 1990): 1359–70. http://dx.doi.org/10.1139/e90-146.
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The mid-Paleozoic deformation of lower Paleozoic subgreenschist-facies sediments of the Hazen fold belt in northern Ellesmere Island is represented predominantly by chevron-style folding. Folded multilayers display cleavage fans suggesting synchronous fold and cleavage formation. Bedding-parallel slip indicates a flexural slip mechanism of folding. The geometry of several large-scale anticlinoria has been interpreted as being due to formation of these structures over detachments and thrust ramps.The constant fold geometry, the parallel orientation of faults and large- and small-scale folds, and the axial-plane foliation are related to a single phase of folding with a migrating deformation front in the Hazen fold belt during the mid-Paleozoic orogeny. The minimum amount of shortening in the Hazen and Central Ellesmere fold belts has been estimated from surface geology to increase from 40–50% of the original bed length in the external southeastern part to 50–60% in the more internal northwestern part of the belts.The convergent, thin-skinned nature of the Hazen and Central Ellesmere fold belts indicates that the postulated transpressive plate motions during the accretion of Pearya did not affect the study area.
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BELL, T. H., and S. E. JOHNSON. "The role of deformation partitioning in the deformation and recrystallization of plagioclase and K-feldspar in the Woodroffe Thrust mylonite zone, central Australia." Journal of Metamorphic Geology 7, no. 2 (March 1989): 151–68. http://dx.doi.org/10.1111/j.1525-1314.1989.tb00582.x.
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Andrew, Joseph E. "Geologic map of central Panamint Range, California, USA." Geosphere 18, no. 2 (March 10, 2022): 730–31. http://dx.doi.org/10.1130/ges02344.1.
Full textAbstract:
Abstract This detailed geologic map and supplemental digital data set1 examine and demonstrate the complex deformational history and reactivation relationships of the Panamint Range (California, USA), from active transtension of the Walker Lane belt, Miocene extension of the Basin and Range, to multiple Mesozoic events related to subduction, and Neoproterozoic extension. This collection of map data focuses on the geometry, kinematics, and relative timing of deformation to understand the deformation history and effects of structural reactivation. A minor portion of this geologic mapping data was presented in the analysis and figures of Andrew and Walker (2009). The Neogene extension and subsequent dextral transtension deformation has created a complex network of faults via partial reactivation of Mesozoic and Neoproterozoic structures. Structural data show oblique normal slip overprinting earlier normal slip along the western range flank fault of the western Panamint Range. Jurassic and Cretaceous deformation is localized along the western range on the Goldbug fault. The hanging wall of this fault preserves migmatitic fabrics and intense deformation due to Jurassic contraction. The Goldbug fault places Paleoproterozoic to Mesoproterozoic rocks over Neoproterozoic rocks. The Jurassic contraction has top-to-the-northeast relative transport and the more discrete Cretaceous thrust faulting has top-to-the-east transport. A set of Late Cretaceous plutonic rocks and mylonitic gneisses derived from them, occur along the Goldbug fault and demonstrate the reactivated nature of this fault in the Late Cretaceous. New data for the Butte Valley fault show that this fault cuts Late Jurassic plutonic rocks and has normal slip. The Butte Valley fault ends northward at the linked sinistral slip Warm Spring Canyon fault, which was previously interpreted to be an intrusive contact. A previously unrecognized rim syncline structure occurs along the boundary of the Late Jurassic Manly Peak quartz monzonite. Neoproterozoic deformation is difficult to discern due to the overprinting deformations. Numerous Neoproterozoic deformation-related mass wasting deposits can be seen within this formation, including a set of conspicuous allochthonous deposits and clasts of older Beck Spring Dolomite that appear to be frozen in the process of breaking away from intact, normal thickness beds in the Surprise–Happy Canyons divide. This detailed geologic mapping and collection of structural data for the rocks in the central Panamint Range were created using digital in-the-field geographic information systems software running on a field-hardened laptop computer combined with an earlier set of field data that were digitized into the digital georeferenced database. This map is a simplification of detailed geologic mapping data collected at 1:2000–1:6000 scales and reduced to 1:20000 scale. Structural data include kinematic and relative timing of deformation information.