Acadian deformation in the shallow crust: an example from the Siluro-Devonian Arisaig Group, Avalon terrane, mainland Nova Scotia

2006 ◽  
Vol 43 (1) ◽  
pp. 71-81 ◽  
Author(s):  
James A Braid ◽  
J Brendan Murphy
Keyword(s):  
Nova Scotia ◽  
Shear Zones ◽  
Thrust Fault ◽  
Structural Features ◽  
Strike Slip ◽  
Normal Faults ◽  
Progressive Deformation ◽  
Acadian Orogeny ◽  
Shallow Crust ◽  
Dextral Strike Slip

The Silurian – Early Devonian Arisaig Group of the Avalon terrane in northern mainland Nova Scotia consists mainly of thinly bedded sandstones, siltstones, and shales deposited in a near shore environment. These strata were deformed in the middle Devonian to form regional northeast- to NNE-trending folds and record deformation processes in the shallow crust during the Acadian orogeny, one of the most regionally extensive orogenic events in the Canadian Appalachians. Structural features in the Arisaig Group are consistent with fold propagation associated with thrust fault geometry and coeval local extension recorded by a set of conjugate normal faults. Many outcrop-scale folds have sheared limbs and show evidence of a complex progressive deformation. Folding was predominantly accomplished by bulk rotation and flattening above thrust fault tips. Early structures (D1–D2) produced regional cylindrical folds, whereas later (D3a, D3b, D3c) structures produced conical folds. D1–D3 fold orientations show high variability, but are consistent with progressive deformation related to reactivation and coeval dextral strike-slip movement along the Hollow Fault. The style of deformation is compatible with models in which strain is partitioned into preexisting shear zones in the basement, with folds in the overlying Arisaig Group initiated above the tips of upward-propagating thrusts as second-order structures related to movement along those shear zones. Taken together, these data indicate that fold mechanisms and geometry in the shallow crust during the Acadian orogeny in mainland Nova Scotia may be related to dextral strike-slip along major faults in the basement and co-genetic upward-propagating thrusts that rotated and flattened overlying strata.

Extension and transtension associated with strike-slip faults and its relation with aquifer potentials: a case study in Aravalli terrane (North Gujarat), India

2020 ◽  
Author(s):  
Rudra Mohan Pradhan ◽  
Tapas Kumar Biswal
Keyword(s):  
Complex Geometry ◽  
Fractured Rock ◽  
Primary Source ◽  
Structural Data ◽  
Shear Zones ◽  
Structural Features ◽  
Strike Slip ◽  
Normal Faults ◽  
Fold Belt ◽  
North Gujarat

<p>Fractured rock aquifers are one of the most difficult aquifers to characterize due to complex geometry and fracture network. In Aravalli terranes of North Gujarat, communities depend on basement rock aquifers as the primary source of water supply. The hydrogeology of these aquifers is poorly understood and the drinking/irrigation wells are frequently placed in this area with little appreciation of the fracture systems. Increasing water demand puts stress to explore groundwater from less reliable sources of basement rocks and hence, makes it vital to identify potential hydrogeological zones. Lineament studies are commonly used for targeting groundwater bearing zones in hard rock terrane and very often ignore the other important structural settings viz. extension, transtension etc. For the present study, structural data pertaining faults and fractures have been mapped through fieldwork and Electrical resistivity imaging (ERT) technique. The key objective of the study is to correlate the structural features (extensional and transtensional settings) with geophysical profiles and to find out potential hydrogeological zones from where water can be explored economically. The study area comes under the Ambaji basin of Aravalli-Delhi fold belt which is a Proterozoic fold belt running 700-800 km in NE-SW direction and situated in NW India. The Aravalli-Delhi fold belt had undergone multiple phases of deformation. In this area, three major sets of fractures are present and are oriented largely in WNW-ESE, NE-SW, and NW-SE direction. The WNW-ESE fracture is dextral in nature which has interpreted from the displacement of fold limbs. Further, these are right lateral en-echelon normal faults where NE-SW extension has been taken place. There is another set of fracture i.e. NW-SE which is due to stretching of strike-slip fault. The ductile shear zones in the area are also parallel to the NW-SE fracture set. The shear zones are opened-up due to extension and formed potential aquifers. ERT has been carried out along and across the fractures to understand the subsurface fracture geometry. The ERT shows deep sited fractures and low resistivity values at the cross-section of WNW-ESE faults with the shear zone. This concludes a strong correlation between different structural settings with potential aquifers which could be used for pumping as well as artificial recharge sites for long term sustainability.</p><p><strong>Keywords-</strong> Aravalli terrane, Aquifer, Extension, Fracture, ERT</p>

Acadian strike-slip tectonics in the Gaspé region, Quebec Appalachians

1989 ◽  
Vol 26 (9) ◽  
pp. 1764-1777 ◽  
Author(s):  
Michel Malo ◽  
Jacques Béland
Keyword(s):  
Middle Devonian ◽  
High Strain ◽  
Structural Features ◽  
Fault Zones ◽  
Strike Slip ◽  
Structural Units ◽  
Middle Ordovician ◽  
Southern Margin ◽  
Intense Deformation ◽  
Dextral Strike Slip

At the southern margin of the Cambro-Ordovician Humber Zone in the Quebec Appalachians, on Gaspé Peninsula, three structural units of Middle Ordovician to Middle Devonian cover rocks of the Gaspé Belt are in large part bounded by long, straight longitudinal faults. In one of these units, the Aroostook–Percé anticlinorium, several structural features, which can be ascribed to Acadian deformation, are controlled by three subparallel, dextral, strike-slip longitudinal faults: Grande Rivière, Grand Pabos, and Rivière Garin. These faults follow bands of intense deformation, contrasting with the mildly to moderately deformed intervals that separate them.Most of the structural features observed – rotated oblique folds and cleavage, subsidiary Riedel and tension faults, and offsets of markers – can be integrated in a model of strike-slip tectonics that operated in ductile–brittle conditions. A late increment of deformation in the form of conjugate cleavages and minor faults is restricted to the bands of high strain. An anticlockwise transection of the synfolding cleavage in relation to the oblique hinges may be a feature of the rotational deformation.The combined dextral strike slip that can be measured within the three major longitudinal fault zones amounts to 138 km, to which can be added 17 km of ductile movement in the intervals, for a total of 155 km.

Miocene to Messinian deformation and hydrothermal activity in a pre-Alpine basement massif of the French western Alps: new U-Th-Pb and argon ages from the Lauzière massif

2010 ◽  
Vol 181 (3) ◽  
pp. 227-241 ◽  
Author(s):  
Dominique Gasquet ◽  
Jean-Michel Bertrand ◽  
Jean-Louis Paquette ◽  
Jérémie Lehmann ◽  
Gueorgui Ratzov ◽  
...  
Keyword(s):  
Late Miocene ◽  
Shear Zones ◽  
Hydrothermal Activity ◽  
Western Alps ◽  
Strike Slip ◽  
Quartz Veins ◽  
The North ◽  
Slip Regime ◽  
Tectonically Active ◽  
Dextral Strike Slip

Abstract U-Pb and Th-Pb dating of monazite from hydrothermal quartz veins (“Alpine veins”) from the Lauzière massif (North Belledonne) together with Ar/Ar ages of adularias from the same veins constrain the age of the last tectono-metamorphic events that affected the External Crystalline Massifs (ECM). Ages obtained are surprisingly young. The study of the structural context of the veins combined with our chronological data, allow us to propose a tectonic scenario of the northern ECM for the 15-5 Ma period, which was poorly documented so far. The quartz veins are of two types: (i) the oldest are poorly mineralized (chlorite and epidote), flat-lying veins. The quartz fibres (= extension direction) are near vertical and seem to be associated with a subvertical dissolution schistosity superimposed upon an early Alpine deformation underlined by “mini-biotite”. They bear a sub-horizontal stretching lineation; (ii) the youngest veins are very rich in various minerals (anatase, rutile, phénacite, meneghinite, beryl, synchysite, ….). They are almost vertical. Their “en echelon” geometry as well as the horizontal attitude of their quartz fibres show a dextral strike-slip regime. Two groups of Th-Pb ages have been obtained: 11 to 10 Ma and 7 to 5 Ma. They were obtained from the most recent veins (vertical veins) sampled in different areas of the massif. The ca. 10 Ma ages are related to veins in the Lauzière granite and its metamorphic country-rocks at about 2 km from the eastern contact of the massif, while the ages of ca. 5 Ma correspond to veins occurring in mylonites along this contact. Adularias provided Ar/Ar ages at ca. 7 Ma. By contrast, a monazite from a vein of the Pelvoux massif (Plan du Lac) yielded a Th-Pb age of 17.6 Ma but in a different structural setting. Except fission track ages, there are very little ages of this range published in the recent literature on the Alps. The latter concern always gold mineralized veins (NE Mont Blanc and SW Lepontine dome). The last compressive tectonic regime dated between 15 and 12 Ma is coeval with (i) the late “Roselend thrust” event, which is recorded in the Mont Blanc by shear-zones with vertical lineation, (ii) the last movements in the basal mylonites of the Swiss Nappes, (iii) the horizontal Alpine veins from the Mont Blanc and Belledonne massifs (with vertical quartz fibres), which are similar to the early veins of the Lauzière. On the contrary, the vertical veins of the Lauzière, dated between 11 and 5 Ma, correspond to a dextral strike slip regime. This suggests that most of the strike-slip tectonics along the ECM took place during two stages (ca. 10 Ma and ca. 7-5 Ma) and not only at 18 Ma as had been proposed previously. Our ages are consistent with the late Miocene-Pliocene overlap of the Digne thrust to the South and to part of the normal movement along the Simplon fault to the North. Thus, all the external crystalline massifs were tectonically active during the late Miocene. This suggests that tectonic events in the external alpine belt may have contributed to some extent to the geodynamical causes of the Messinian crisis.

Pre-, syn-, and post-imbrication deformation of carbonate slices along the southern Quebec Appalachian front – implications for hydrocarbon exploration

2007 ◽  
Vol 44 (4) ◽  
pp. 543-564 ◽  
Author(s):  
Stephan Séjourné ◽  
Michel Malo
Keyword(s):  
Strain Relaxation ◽  
Structural Features ◽  
Strike Slip ◽  
Hydrocarbon Exploration ◽  
Normal Faults ◽  
Structural Style ◽  
Slip Planes ◽  
Bed Thickness ◽  
Seismic Scale ◽  
Extensional Structures

Thrust-imbricated shelf-carbonate slices form a wide but poorly understood part of the southernmost Quebec Appalachian structural front. Comprehensive structural analysis of two slices exposed at surface, the Saint-Dominique and Philipsburg slices, shows that pre- and post-imbrication structures are important in defining the final architecture of the slices. The dominant structural style is characterized by thrusts and associated asymmetrical folds, tear faults, oblique ramps and incipient backthrusts developed during WNW–ESE shortening. A forward-breaking (piggy-back) sequence of thrusting is recognised, as well as minor out-of-sequence thrusting. The complexity and diversity of contractional structures is directly influenced by lithology (bed thickness and shale content). Bedding-parallel slip planes are important in the concentration (activation and reactivation) of deformation, in that there are the loci for veining, faulting, and folding. Recognition of lithostructural units provides guidelines for the identification of sub-seismic-scale structural traps in subsurface investigations. Extensional structures (normal faults, veins, tension gashes) are found within all carbonate slices, as well as within the footwall of their basal thrusts. Only a few pre-imbrication normal faults have been identified, one of which is a growth fault. Post-imbrication extensional structures are linked with strain relaxation after overthrusting. A widespread front-parallel strike-slip faulting event postdates all other structural features and can have a major impact on the compartmentalization of potential hydrocarbon reservoirs.

Paleolatitude and Tectonic Rotations of the Early Carboniferous Fountain Lake Group, Cobequid Highlands, Nova Scotia, Canada

2021 ◽  
Author(s):  
Kate Brooks ◽  
Phil J.A. McCausland ◽  
John W.F. Waldron
Keyword(s):  
Nova Scotia ◽  
Early Carboniferous ◽  
Strike Slip ◽  
Block Rotation ◽  
Beam Analysis ◽  
Recent Origin ◽  
Stable Characteristic ◽  
Dextral Strike Slip ◽  
Slip Motion ◽  
Moose River

The ca. 355 Ma Fountain Lake Group, in the Cobequid Highlands of Nova Scotia, is part of the transtensional basin fill which formed during dextral strike-slip motion between Avalonia and the Meguma terranes following the Acadian Orogeny. Paleomagnetic analysis of the Fountain Lake Group offers a paleolatitude estimate for the Laurentian accretionary margin in the Early Carboniferous and locality-specific paleomagnetic directions which indicate clockwise-sense block rotations during dextral strike-slip motion along the Cobequid Fault zone. Stepwise demagnetization of 142 specimens from 20 sites in three Fountain Lake Group localities across the Cobequid Highlands (Squally Point, West Moose River, and Wentworth exposures) reveals remanence consisting of an easily removed component of probable recent origin, and more persistent components carried by magnetite and hematite, which in petrographic and electron beam analysis appear to be of primary igneous and volcanic oxidation origins, respectively. Sites from all three localities carry stable characteristic remanent magnetization (ChRM) directions that assume similar moderate downward inclinations when tilt-corrected. A Block Rotation Fisher analysis inclination-only fold test demonstrated best agreement at 90% unfolding, showing that remanence acquisition pre-dates Alleghenian deformation in the Late Carboniferous and is most likely of primary 355 Ma age. Paleomagnetic results for the Squally Point, West Moose River and Wentworth localities show relative rotations between the blocks that are variously clockwise-rotated compared with a Laurentia cratonic reference frame. Inclinations at all three localities imply a subtropics paleolatitude for the margin (at Squally Point, 27.2° ± 9.4°; N= 7 sites), directly supporting the depicted location of Laurentia and its Appalachian accretionary margin in most Devonian to Early Carboniferous reconstructions.

Mineralogy of the Au-Ag mineralization from the Finsterort and Anton vein system, Štiavnické vrchy Mts. (Slovakia)

2021 ◽  
Vol 29 (2) ◽  
pp. 255-269
Author(s):  
Jozef Vlasáč ◽  
Martin Chovan ◽  
Rastislav Vojtko ◽  
Peter Žitňan ◽  
Tomáš Mikuš
Keyword(s):  
Middle Miocene ◽  
Precious Metals ◽  
Central Zone ◽  
Strike Slip ◽  
Normal Faults ◽  
Normal Faulting ◽  
Vein System ◽  
Štiavnica Stratovolcano ◽  
Dextral Strike Slip ◽  
Strike Slip Movement

The Finsterort and Anton vein system is located in the central zone of the Middle Miocene Štiavnica Stratovolcano between Vyhne and Hodruša-Hámre villages. The vein system contains several partial veins and veinlets and has generally NNE - SSW strike with moderate to steep eastward dip. Kinematics of the veins is characterised by older dextral strike-slip movement replaced by younger normal faulting. The mineralization is associated with the normal faults and the veins contain interesting paragenesis of Au-Ag bearing minerals. Minerals of precious metals are represented by argentotetrahedrite-(Zn) and rozhdestvenskayaite-(Zn), Au-Ag alloys, members of polybasite-pearceite and pyrargyrite-proustite solid solutions, acanthite and uytenbogaardtite. Au-Ag mineralization is accompanied by older paragenesis comprising mainly pyrite, galena, sphalerite and chalcopyrite. Besides quartz, carbonates (calcite, siderite and dolomite) are the main gangue minerals.

Role of dextral strike slip faulting in the distribution of Aegean extension since Miocene times inferred from receiver function analysis

2020 ◽  
Author(s):  
Agathe Faucher ◽  
Christel Tiberi ◽  
Frédéric Gueydan ◽  
Alexandrine Gesret
Keyword(s):  
Receiver Function ◽  
Function Analysis ◽  
Receiver Functions ◽  
Strike Slip ◽  
Point Of View ◽  
Normal Faults ◽  
The South ◽  
Crustal Thinning ◽  
Dextral Strike Slip

<p>Aegean plate is marked since Eocene by widespread NE-SW extension induced by the African slab roll-back. In Miocene times, E-W shortening created by the westward Anatolian extrusion overlays the extension, with the formation of Miocene dextral strike slip faults in addition to normal faults. We propose to quantify the role of large dextral strike slip faults in accommodating Aegean extension, using receiver functions to image Moho geometry.</p><p>Aegean extension is particularly evidenced by a topographic difference between the emerged continental Greece and the submerged Cyclades. In this study we characterize the associated Moho geometry with a particular focus on the transition between these two domains. From a geological point of view, the transition between continental Greece and the Cyclades is marked by two dextral strike slip faults: the Pelagonian fault (onshore) and the South Evvia fault (offshore). Our objective is also to show a potential Moho signature of these strike slip faults.  We processed receiver functions (RF) from the MEDUSA stations located in Attic and Evvia.</p><p>Our results show that the Moho is deeper beneath continental Greece (~27km) than beneath the Cyclades (~25km). A detailed azimuthal study of RF distribution shows a flat Moho underneath Continental Greece. The crustal thickness is also almost constant inside the Cyclades, as already suggested by previous studies. However, the transition between the Cyclades and Continental Greece is not continuous. These two crustal blocks are separated by the Pelagonian and the South Evvia strike slip faults in a narrow transition zone (~75km). In this zone (South Evvia/Attica), dip and strike of the Moho vary and suggest a crustal signature of the strike slip structures observed at the surface. These strike slip faults therefore accommodate in a narrow zone the inferred variations in crustal thicknesses between the Cyclades and Continental Greece.</p><p>Our data show that differences in topography between Continental Greece and the Cyclades are isostatically compensated, reflecting various amount of crustal thinning larger in the Cyclades than in Continental Greece. Inside these two crustal blocks, we imaged a flat Moho, suggesting a wide rift extension process associated with the formation of numerous Miocene and Plio-Quaternary basins.  The dextral strike slip faults at the edges of the continental blocks (Continental Greece and Cyclades) accommodated the inferred variations in the amount of crustal thinning, suggesting that they act as continental transfer zones at crustal-scale during Miocene Aegean Extension.</p>

scholarly journals Structural Features of the Central Labrador Trough: A Model for Strain Partitioning, Differential Exhumation and Late Normal Faulting in a Thrust Wedge under Oblique Shortening

2019 ◽  
pp. 5-30 ◽  
Author(s):  
Elena Konstantinovskaya ◽  
Gennady Ivanov ◽  
Jean-Louis Feybesse ◽  
Jean-Luc Lescuyer
Keyword(s):  
Hanging Wall ◽  
Shear Zones ◽  
Structural Features ◽  
Normal Faults ◽  
Strain Partitioning ◽  
Oblique Collision ◽  
Fold And Thrust Belt ◽  
Thrust Tectonics ◽  
Oblique Convergence ◽  
Longitudinal Variations

The west-verging fold and thrust belt of the Central Labrador Trough originated as a part of the New Quebec Orogen from rift inversion as a result of oblique collision and dextral transpression between the Archean Superior craton and the Archean block of the Core Zone during the Trans-Hudson orogeny (1.82−1.77 Ga). The structures associated with dextral transpression are well established in the northern segment of the orogen but not in the central part. We present new field structural observations along the ca. 70 km long W−E Minowean-Romanet transect that include not only elements of thrust tectonics but also previously undocumented examples of strike-slip shear zones and late brittle, semi-brittle and ductile extensional structures which occurred both in the frontal and rear parts of the thrust wedge. The newly described low-angle mineral lineation, axes of cylindrical folds and dextral mylonitic shear zones in the footwall of the Romanet Fault are oriented subparallel to the orogen and reflect the early phase of oblique convergence. Mineral lineations and striations on planes of normal faults in the hanging wall of the Romanet Fault are oriented orthogonal to the orogen and correspond to a later phase of exhumation driven by the combined effects of erosion and underplating. To explain the increase in the degree of exhumation along the orogen in the study area from NW to SE, we propose a model of strain partitioning and differential exhumation that resulted from longitudinal variations of shortening and erosion under an oblique convergence setting.RÉSUMÉLa partie centrale de la ceinture de plissement et de chevauchement de la Fosse du Labrador de vergence vers l’ouest fait partie intégrante de l’Orogène du Nouveau-Québec, et résulte de la collision oblique avec transpression dextre entre le craton Supérieur archéen et le bloc archéen de la Zone noyau pendant l’Orogenèse trans-hudsonienne (1.82−1.77 Ga). Les structures associées à la transpression dextre sont bien établies dans la partie nord de l’orogène mais pas dans la partie centrale. Nous présentons de nouvelles observations structurales de terrain le long de la traverse ouest−est Minowean-Romanet d’environ 70 km de long, qui comprennent non seulement des évidences de tectonique de chevauchement, mais également des exemples encore non documentés de zones de cisaillement ductile et de structures d’extension fragiles, demi-fragiles et ductiles à la fois dans les parties frontales et arrière du prisme d’accrétion tectonique. La linéation minérale à faible plongement récemment décrite, les axes de plis cylindriques et les zones de cisaillement mylonitique dextre dans le compartiment inférieur de la faille de Romanet sont subparallèles à l’orogène et reflètent une phase précoce de la convergence oblique. La linéation et les stries minérales sur les plans des failles normales dans le compartiment supérieur de la faille de Romanet sont orientées orthogonalement à l’orogène et correspondent à la phase ultérieure d’exhumation induite par les effets combinés de l’érosion et de l’accrétion basale. Pour expliquer l’augmentation du degré d’exhumation le long de l’orogène du nord-ouest au sud-est dans la zone d’étude, nous proposons un modèle de partitionnement de la déformation et de l’exhumation différentielle résultant des variations longitudinales du raccourcissement et de l’érosion dans un contexte de convergence oblique.

scholarly journals The state of stress in the shallow crust of the Hikurangi Subduction Margin hangingwall, New Zealand

2021 ◽  
Author(s):  
Effat Behboudi ◽  
David McNamara ◽  
Ivan Lockmer ◽  
Laura Wallace ◽  
Tom Manzocchi
Keyword(s):  
New Zealand ◽  
Stress State ◽  
Strike Slip ◽  
P Wave ◽  
Normal Faults ◽  
Stress Regime ◽  
Seismic Reflection Data ◽  
Compressional Stress ◽  
Stress States ◽  
Shallow Crust

<p>Knowledge of in situ stress fields is critical for a better understanding of deformation, faulting regime, and earthquake processes in seismically active margins such as the Hikurangi Subduction Margin (HSM), North Island, New Zealand. In this study, we utilize Leak-off Test (LOTs) data, borehole breakout widths measured from borehole image logs, and rock unconfined compressive strengths (UCS) derived from empirical P-wave velocity log relationships to estimate vertical (Sv), minimum (Shmin), and maximum horizontal stress magnitudes (SHmax) and interpret the likely faulting regime experienced in four boreholes (Kauhauroa-2, Kauhauroa-5, Titihaoa-1, and Tawatawa-1). Using the standard Anderson’s stress regime classification, relative stress magnitudes in Kauhauroa-5 at 1200-1700 m depth and Kauhauroa-2 at 1800-2100 m and  indicate that the stress state in the shallow crust of the central and northern part of HSM is predominantly strike-slip (SHmax≥Sv≥Shmin) and normal Sv≥SHmax> Shmin respectively. Moving to the offshore, southern HSM a dominant compressional stress regime (SHmax> Shmin >Sv), with some possible strike slip stress states are observed in Titihaoa-1 from 2240-2660 m and Tawatawa-1 from 750-1350 m. The observed normal/strike-slip stress state in Kauhauroa-2 and Kauhauroa-5 is consistent with the average SHmax orientation of 64° ± 18° (NE-SW) determined from borehole breakouts and dominantly NE–SW striking normal faults interpreted from seismic reflection data. The normal/ strike-slip regime in this area suggests that the stress regime here is probably influenced by the effect of the clockwise rotation of the HSM hangingwall associated with oblique Pacific-Australia plate convergence (ENE-WSW). Alternatively, these stress states could be the result of gravitational collapse due to rapid uplift of the subducting plate during the mid-Miocene. The compressional stress regime in the southern HSM in Titihaoa-1 and Tawatawa-1 is in agreement with the SHmax orientations of 148° ± 14° (NW-SE ) and 102° ± 16° (WNW-ESE) obtained from image logs and mapped NE–SW striking reverse faults in this region. This observation suggests that the tectonics here are strongly linked to the subduction of Hikurangi plateau under Australian Plate (NW-SE) or active frontal thrusts in the overriding plate. </p>

Brittle faulting in the Thor–Odin culmination, Monashee complex, southern Canadian Cordillera: constraints on geometry and kinematics

2005 ◽  
Vol 42 (12) ◽  
pp. 2141-2160 ◽  
Author(s):  
Stefan Kruse ◽  
Paul F Williams
Keyword(s):  
Strike Slip ◽  
Normal Faults ◽  
Canadian Cordillera ◽  
The West ◽  
West Side ◽  
The North ◽  
Monashee Complex ◽  
Dextral Strike Slip Fault ◽  
Brittle Faulting ◽  
Dextral Strike Slip

Regionally recognized dextral strike-slip faulting is present in the Monashee complex of the southern Canadian Cordillera but is overprinted and partially obscured by subsequent extension. Eocene brittle faults and fractures within the Thor–Odin culmination of the Monashee complex are divisible into three distinct sets. Initial 340°–010° trending strike-slip faults (set 1) were locally overprinted and reactivated by normal faults with a 325°–020° trend (set 2). A third set of 255°–275° trending fractures (set 3) are interpreted as conjugates to set 1, reactivated as transfer faults to the set 2 normal faults. Large regional faults weather recessively, forming topographic lineaments that transect the Monashee complex. The Victor Creek Fault defines one such lineament. Detailed mapping within the northern Thor–Odin culmination reveals piercement points (fold hinges) on the east side of the fault that are not readily matched on the west side. The minimum displacement required on the Victor Creek Fault to down-drop the fold hinge below the level of exposure on the west side is 1370 m, assuming normal down-to-the-west displacement. The geometry of the fault is consistent with a set 1 dextral strike-slip fault, however. Matching the piercement points in the study area with possible equivalents to the north indicates 55–60 km of dextral strike-slip displacement.

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