Deformation of soft sediments and evaporites in a tectonically active basin: Bay St. George sub-basin, Newfoundland, Canada

2021 ◽  
Vol 57 ◽  
pp. 275-304
Author(s):  
Morgan E. Snyder ◽  
John W. F. Waldron
Keyword(s):  
Hanging Wall ◽  
Normal Growth ◽  
Strike Slip ◽  
Late Paleozoic ◽  
Tectonic Structures ◽  
Tectonically Active ◽  
Maritimes Basin ◽  
Dextral Strike Slip ◽  
Slip Motion ◽  
Overlying Strata

The Bay St. George sub-basin of SW Newfoundland, part of the larger late Paleozoic Maritimes basin, formed under the influence of strike-slip faulting and the movement of evaporites. New stratigraphic correlations between Newfoundland and other late Paleozoic sub-basins illustrate the effects of both basement and salt movement. Coastal outcrops show complex combinations of synsedimentary, salt-related, and tectonic structures. Map relationships and dramatic thickness contrasts in the Tournaisian Anguille Group indicate that a large, concealed, NE–striking normal growth fault (Ship Cove fault) controlled sedimentation; the exposed Snakes Bight fault originated as a hanging-wall splay. Structures formed during, or soon after deposition include soft-sediment folds, boudins, clastic dykes, and millimetre-scale diapiric bulb structures, formed by overpressuring and liquidization of sediment. These suggest that the sub-basin was tectonically active throughout deposition. Evaporite-related deformation is recorded in the Visean Codroy Group and overlying strata. Comparisons between outcrop and subsurface suggests that significant amounts of evaporite were removed from exposed sections by halokinesis and solution. Complex outcrop relationships indicate salt welds, and suggest that units of the upper Codroy and overlying Barachois groups represent fills of minibasins that subsided into thick evaporites. Field relationships suggest tectonic inversion deposition related to E-W dextral strike slip motion that affected the entire Maritimes basin in the Serpukhovian, producing reverse-sense offsets and contractional folds. Many of the structures in the Bay St. George sub-basin, previously interpreted as post-depositional and purely tectonic, were formed by deformation of unlithified sediment and ductile evaporites during basin development.

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.

The Border Ranges fault system in Glacier Bay National Park, Alaska: evidence for major early Cenozoic dextral strike-slip motion

1996 ◽  
Vol 33 (9) ◽  
pp. 1268-1282 ◽  
Author(s):  
Kevin J. Smart ◽  
Terry L. Pavlis ◽  
Virginia B. Sisson ◽  
Sarah M. Roeske ◽  
Lawrence W. Snee
Keyword(s):  
National Park ◽  
Strike Slip ◽  
Fault System ◽  
Glacier Bay ◽  
Oblique Convergence ◽  
Glacier Bay National Park ◽  
Wrangellia Terrane ◽  
Early Cenozoic ◽  
Dextral Strike Slip ◽  
Slip Motion

The Border Ranges fault system of southern Alaska, the fundamental break between the arc basement and the forearc accretionary complex, is the boundary between the Peninsular–Alexander–Wrangellia terrane and the Chugach terrane. The fault system separates crystalline rocks of the Alexander terrane from metamorphic rocks of the Chugach terrane in Glacier Bay National Park. Mylonitic rocks in the zone record abundant evidence for dextral strike-slip motion along north-northwest-striking subvertical surfaces. Geochronologic data together with regional correlations of Chugach terrane rocks involved in the deformation constrain this movement between latest Cretaceous and Early Eocene (~50 Ma). These findings are in agreement with studies to the northwest and southeast along the Border Ranges fault system which show dextral strike-slip motion occurring between 58 and 50 Ma. Correlations between Glacier Bay plutons and rocks of similar ages elsewhere along the Border Ranges fault system suggest that as much as 700 km of dextral motion may have been accommodated by this structure. These observations are consistent with oblique convergence of the Kula plate during early Cenozoic and forearc slivering above an ancient subduction zone following late Mesozoic accretion of the Peninsular–Alexander–Wrangellia terrane to North America.

scholarly journals Tectonics of the Central Part of the Adycha-Taryn Fault Zone (Verkhoyansk-Kolyma Orogenic Belt, NE Asia)

2021 ◽  
Vol 906 (1) ◽  
pp. 012109
Author(s):  
D.A. Vasiliev ◽  
A.V. Prokopiev ◽  
N.N. Ermakov
Keyword(s):  
Fault Zone ◽  
First Generation ◽  
Regional Scale ◽  
Strike Slip ◽  
Orogenic Belt ◽  
Tectonic Structures ◽  
Late Mesozoic ◽  
Deformation Stage ◽  
Fold And Thrust Belt ◽  
Dextral Strike Slip

Abstract The study area is located in the central part of the regional-scale Adycha-Taryn fault zone separating the Adycha-El’gi and Nera anticlinoria in the hinterland of the Verkhoyansk fold-and-thrust belt (central part of the Verkhoyansk-Kolyma orogenic belt). Detailed structural studies were conducted in large quarries in the lower reaches of the El’gi River (Indigirka R. basin). In the Adycha-El’gi anticlinorium, several generations of folds, faults, and cleavage are recorded. The intensity of deformation here is found to gradually increase in NE direction. The NE wall of the Adycha-Taryn fault is thought to be more strongly deformed. The results of our investigations revealed three structural parageneses. The first paragenesis includes thrusts, reverse faults, and intense NW-striking folds of the first generation. The second paragenesis consists of less intense superposed folds of the second generation, with subvertical axes, as well as sinistral strike-slip faults. The previously made assumption is confirmed about manifestation in the study area of at least two deformation stages. We also presuppose the existence of the third deformation stage in which dextral strike-slip faults were formed. A change in the intensity of tectonic deformations both along and across the Adycha-Taryn fault zone is first established. On the southwestern side of the fault zone, the intensity of deformation structures decreases from NW to SE. On the northeastern side, the deformation intensity first increases in that same direction but then tends to diminish. An assumption is made about a growing importance of reverse faults in NW direction, along the Adycha-Taryn fault zone. Orientation of paleostress axes responsible for the formation of tectonic structures in the study area is first determined. Folds and thrusts of the first deformation stage were formed under subhorizontal compression in NE direction. Sinistral strike slips and associated folds of the second deformation stage resulted from WE-oriented subhorizontal compression. The following dextral strike-slip motions occurred in the conditions of NW-directed subhorizontal compression and NE-oriented subhorizontal extension. The studied tectonic deformations were formed in Late Mesozoic time as a result of collision-accretion events in the central part of the Verkhoyansk-Kolyma orogenic belt.

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.

Paleomagnetic evidence for dextral strike-slip motion in the Pyrenees during alpine convergence (Mauléon basin, France)

2010 ◽  
Vol 494 (3-4) ◽  
pp. 165-179 ◽  
Author(s):  
B. Oliva-Urcia ◽  
A.M. Casas ◽  
E.L. Pueyo ◽  
T. Román-Berdiel ◽  
J.W. Geissman
Keyword(s):  
Strike Slip ◽  
Dextral Strike Slip ◽  
Slip Motion

Record of Late Mississippian tectonics in the new Percé Group (Viséan) of eastern Gaspésie, Quebec

2005 ◽  
Vol 42 (5) ◽  
pp. 815-832 ◽  
Author(s):  
Pierre Jutras ◽  
Gilbert Prichonnet
Keyword(s):  
Slip System ◽  
Marine Sediments ◽  
Strike Slip ◽  
Alluvial Fan ◽  
Normal Faulting ◽  
Broad Area ◽  
Tectonic Events ◽  
Upper Paleozoic ◽  
Maritimes Basin ◽  
Dextral Strike Slip

Viséan clastic units and structures at the northwest margin of the upper Paleozoic Maritimes Basin provide information on tectonic events that are only poorly recorded in more central parts of the basin. These continental units are time equivalent to marine sediments of the Windsor Group of Nova Scotia. They are herein assigned to the new Percé Group, which includes the La Coulée and Bonaventure formations, as well as a new unit, the Cap d'Espoir Formation. The latter unit unconformably underlies the Bonaventure Formation in a small but thick sub-basin of the Ristigouche Basin in eastern Quebec. It is characterized by a succession of sandstone and mudstone rhythmites that contrast with the coarse alluvial fan deposits of the overlying Bonaventure Formation. The Cap d'Espoir Formation was sourced from a broad area of subdued topography occupied by the Viséan La Coulée Formation and underlying units. Erosional remnants of the La Coulée Formation are unconformably overlain by the Bonaventure Formation in marginal parts of the Ristigouche Basin, whereas these units are separated by the Cap d'Espoir Formation in more central areas of the basin. The La Coulée and Cap d'Espoir formations underwent tilting and erosion during a normal faulting event that preceded deposition of the fault-controlled Bonaventure Formation. This series of events is interpreted to represent different steps in the reactivation of a pre-Carboniferous dextral strike-slip system in response to northwest–southeast compression during the Viséan in Gaspésie.

Post-Taconian shortening, inversion and strike slip in the Stephenville area, western Newfoundland Appalachians

2002 ◽  
Vol 39 (9) ◽  
pp. 1393-1410 ◽  
Author(s):  
Sarah E Palmer ◽  
John W.F Waldron ◽  
D M Skilliter
Keyword(s):  
Cross Sections ◽  
Complex Geometry ◽  
Early Carboniferous ◽  
Strike Slip ◽  
Petroleum Exploration ◽  
The West ◽  
Table Mountain ◽  
History Of ◽  
Dextral Strike Slip ◽  
Slip Motion

Deformed terrigenous and carbonate sedimentary rocks representing the early Paleozoic Laurentian continental margin form a series of elongate, fault-bounded blocks that plunge north beneath the Humber Arm Allochthon in the Stephenville area, west Newfoundland Appalachians. The continental shelf succession was folded and thrust-faulted after emplacement of the Humber Arm Allochthon. In the west of the area, Table Mountain is cut by a "pop-up" structure bounded by downward-converging reverse faults. Structures at the east margin of Table Mountain indicate both dextral and reverse slip. The Phillips Brook Structure, farther east, contains multiple, fault-bounded carbonate slices; one slice, carried by the West Blanche Brook fault, is thrust over the Humber Arm Allochthon. The western edge of the Indian Head massif, consisting of Grenville basement, is also a thrust contact. These reverse faults and thrusts, which cut the carbonate succession and postdate emplacement of the Humber Arm Allochthon, are in turn overprinted by structures formed during dextral strike-slip motion. Unconformable Early Carboniferous cover postdates most of the deformation. Cross-sections indicate shortening of a few kilometres, and basement was clearly involved in the deformation. The Port au Port Peninsula, immediately to the west, records a history of Acadian inversion of Taconian basins. The prevalence of pop-up structures and mappable variations within the stratigraphic units forming the top of the carbonate succession indicate that a complex geometry of Taconian horsts and grabens was inverted during post-Taconian (?Acadian) shortening and dextral strike-slip motion. These relationships suggest a variety of attractive targets in petroleum exploration.

Zircon geochronology and paleomagnetism of an Archean harzburgite intrusion, eastern Bighorn Mountains, Wyoming

2020 ◽  
Vol 57 (1) ◽  
pp. 21-40
Author(s):  
Alexandra Wallenberg ◽  
Michelle Dafov ◽  
David Malone ◽  
John Craddock
Keyword(s):  
Hanging Wall ◽  
Vertical Axis ◽  
Shear Zones ◽  
Strike Slip ◽  
Zircon Geochronology ◽  
Weighted Mean ◽  
Mafic Complex ◽  
Laramide Orogeny ◽  
Axis Rotation ◽  
Bighorn Mountains

A harzburgite intrusion, which is part of the trailside mafic complex) intrudes ~2900-2950 Ma gneisses in the hanging wall of the Laramide Bighorn uplift west of Buffalo, Wyoming. The harzburgite is composed of pristine orthopyroxene (bronzite), clinopyroxene, serpentine after olivine and accessory magnetite-serpentinite seams, and strike-slip striated shear zones. The harzburgite is crosscut by a hydrothermally altered wehrlite dike (N20°E, 90°, 1 meter wide) with no zircons recovered. Zircons from the harzburgite reveal two ages: 1) a younger set that has a concordia upper intercept age of 2908±6 Ma and a weighted mean age of 2909.5±6.1 Ma; and 2) an older set that has a concordia upper intercept age of 2934.1±8.9 Ma and a weighted mean age 2940.5±5.8 Ma. Anisotropy of magnetic susceptibility (AMS) was used as a proxy for magmatic intrusion and the harzburgite preserves a sub-horizontal Kmax fabric (n=18) suggesting lateral intrusion. Alternating Field (AF) demagnetization for the harzburgite yielded a paleopole of 177.7 longitude, -14.4 latitude. The AF paleopole for the wehrlite dike has a vertical (90°) inclination suggesting intrusion at high latitude. The wehrlite dike preserves a Kmax fabric (n=19) that plots along the great circle of the dike and is difficult to interpret. The harzburgite has a two-component magnetization preserved that indicates a younger Cretaceous chemical overprint that may indicate a 90° clockwise vertical axis rotation of the Clear Creek thrust hanging wall, a range-bounding east-directed thrust fault that accommodated uplift of Bighorn Mountains during the Eocene Laramide Orogeny.

scholarly journals Kinematic partitioning in the Southern Andes (39° S–46° S) inferred from lineament analysis and reassessment of exhumation rates

2021 ◽  
Author(s):  
Paul Leon Göllner ◽  
Jan Oliver Eisermann ◽  
Catalina Balbis ◽  
Ivan A. Petrinovic ◽  
Ulrich Riller
Keyword(s):  
Fault Zone ◽  
Vertical Displacement ◽  
Strike Slip ◽  
Structural Studies ◽  
Southern Andes ◽  
Plate Convergence ◽  
Exhumation Rates ◽  
Lineament Analysis ◽  
Dextral Strike Slip ◽  
Data Call

AbstractThe Southern Andes are often viewed as a classic example for kinematic partitioning of oblique plate convergence into components of continental margin-parallel strike-slip and transverse shortening. In this regard, the Liquiñe-Ofqui Fault Zone, one of Earth’s most prominent intra-arc deformation zones, is believed to be the most important crustal discontinuity in the Southern Andes taking up margin-parallel dextral strike-slip. Recent structural studies, however, are at odds with this simple concept of kinematic partitioning, due to the presence of margin-oblique and a number of other margin-parallel intra-arc deformation zones. However, knowledge on the extent of such zones in the Southern Andes is still limited. Here, we document traces of prominent structural discontinuities (lineaments) from the Southern Andes between 39° S and 46° S. In combination with compiled low-temperature thermochronology data and interpolation of respective exhumation rates, we revisit the issue of kinematic partitioning in the Southern Andes. Exhumation rates are maximal in the central parts of the orogen and discontinuity traces, trending predominantly N–S, WNW–ESE and NE–SW, are distributed across the entire width of the orogen. Notably, discontinuities coincide spatially with large gradients in Neogene exhumation rates and separate crustal domains characterized by uniform exhumation. Collectively, these relationships point to significant components of vertical displacement on these discontinuities, in addition to horizontal displacements known from published structural studies. Our results agree with previously documented Neogene shortening in the Southern Andes and indicate orogen-scale transpression with maximal vertical extrusion of rocks in the center of the transpression zone. The lineament and thermochronology data call into question the traditional view of kinematic partitioning in the Southern Andes, in which deformation is focused on the Liquiñe-Ofqui Fault Zone.

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