Geodynamic evolution of the Canadian Cordillera — progress and problems

1979 ◽  
Vol 16 (3) ◽  
pp. 770-791 ◽  
Author(s):  
J. W. H. Monger ◽  
R. A. Price
Keyword(s):  
Continental Margin ◽  
Middle Jurassic ◽  
Rocky Mountain ◽  
Ocean Basin ◽  
Strike Slip ◽  
Granitic Rocks ◽  
Canadian Cordillera ◽  
Thrust Faulting ◽  
Western Cordillera ◽  
Geophysical Surveys

The present geodynamic pattern of the Canadian Cordillera, the main features of which were probably established in Miocene time, involves a combination of right-hand strike-slip movements on transform faults along the continental margin, and, in the south and extreme north, convergence in subduction zones in which oceanic lithosphere moves beneath the continent, with consequent magmatism along the continental margin. In the southern Canadian Cordillera, geophysical surveys have outlined the subducting slab and the asthenospheric bulge that occurs beneath and behind the magmatic arc. They also show that there is now no root of thickened Precambrian continental crust beneath the tectonically shortened supracrustal strata in the southern parts of the Omineca Crystalline Belt and Rocky Mountain Belt.The Rocky Mountain, Omineca Crystalline, Intermontane, Coast Plutonic, and Insular Belts, the structural and physiographic provinces that dominate the present configuration of the Canadian Cordillera, were established with the initial uplift and the intrusion of granitic rocks in the Omineca Crystalline Belt in Middle and Late Jurassic time and in the Coast Plutonic Complex in Early Cretaceous time, and they dominated patterns of uplift, erosion and deposition through Cretaceous and Paleogene time. Their development may be due to compression with thrust faulting in the eastern Cordillera, and to magmatism that accompanied subduction and to accretion of an exotic terrane, Wrangellia, in the western Cordillera. Major right-lateral strike-slip faulting, which occurred well east of but sub-parallel with the continental margin during Late Cretaceous and Paleogene time, accompanied major tectonic shortening due to thrusting and folding in the Rocky Mountain Belt as well as the main subduction-related (?) magmatism in the Coast Plutonic Complex.The configuration of the western Cordillera prior to late Middle Jurassic time is enigmatic. Late Paleozoic and early Mesozoic volcanogenic strata form a complex collage of volcanic arcs and subduction complexes that was assembled mainly in the Mesozoic. The change in locus of deposition between Upper Triassic and Lower to Middle Jurassic volcanogenic assemblages, and the thrust faulting in the northern Cordillera may record emplacement of another exotic terrane, the Stikine block, in latest Triassic to Middle Jurassic time.The earliest stage in the evolution of the Cordilleran fold belt involved the protracted (1500 to 380 Ma) development of a northeasterly tapering sedimentary wedge that discordantly overlaps Precambrian structures of the cratonic basement. This miogeoclinal wedge may be a continental margin terrace wedge that was prograded into an ocean basin, but it has features that may be more indicative of progradation into a marginal basin in which there was intermittent volcanic activity, than into a stable expanding ocean basin of the Atlantic type.

Late Paleozoic and Mesozoic terrane interactions in north-central British Columbia

1991 ◽  
Vol 28 (6) ◽  
pp. 947-957 ◽  
Author(s):  
Hubert Gabrielse
Keyword(s):  
British Columbia ◽  
North America ◽  
Middle Jurassic ◽  
Subsequent Development ◽  
Structural Data ◽  
Strike Slip ◽  
Granitic Rocks ◽  
Late Triassic ◽  
North Central ◽  
Dextral Strike Slip

Five clearly defined terranes, comprising from northeast to southwest, Ancestral North America, Slide Mountain, Quesnellia, Cache Creek, and Stikinia, are the dominant tectonic elements of north-central British Columbia. Stratigraphic, sedimentological, plutonic, metamorphic, and structural data show that the Slide Mountain Terrane evolved as a subduction, accretion, and island-arc complex during Permian time. Sedimentological data hint at the demise of the Slide Mountain and Cache Creek oceanic environments in the Permian or Early Triassic and Late Triassic, respectively. Subduction led to the development of volcanic–plutonic island arcs on Stikinia, Quesnellia, and locally on the Cache Creek Terrane in Late Triassic to Middle Jurassic time. Marked inter- and intra-terrane contraction in the Middle Jurassic resulted in the south westward thrusting of the Cache Creek Terrane onto Stikinia, the subsequent development of the Bowser Basin on Stikinia, and possible coeval culmination of the emplacement of Quesnellia and the Slide Mountain Terrane onto Ancestral North America. Deformation, metamorphism, and plutonism along the western margin of Ancestral North America closely followed these events. Contraction was succeeded by a dextral strike-slip regime during the mid-Cretaceous accompanied by the intrusion of voluminous potassic, silica-rich granitic rocks in Ancestral North America. The emplacement of Early to mid-Cretaceous plutons postdated the development of broad, open, regional anticlinoria and synclinoria, perhaps during Early Cretaceous time. The plutonic episode coincided approximately with initiation of the Sustut Basin. Dextral strike-slip faulting further disrupted Ancestral North America until post-Eocene time.

scholarly journals Nailed to the craton: Stratigraphic continuity across the southeastern Canadian Cordillera with tectonic implications for ribbon continent models

Geology ◽  
2020 ◽  
Vol 49 (1) ◽  
pp. 101-105
Author(s):  
M.E. McMechan ◽  
K.G. Root ◽  
P.S. Simony ◽  
D.R.M. Pattison
Keyword(s):  
North American ◽  
Rocky Mountains ◽  
Middle Jurassic ◽  
Horizontal Displacement ◽  
Strike Slip ◽  
Upper Devonian ◽  
Canadian Cordillera ◽  
Tectonic Implications ◽  
Windermere Supergroup ◽  
North American Craton

Abstract Cambrian and Upper Devonian to Mississippian strata can be confidently traced westward, without strike-slip offset, from the autochthonous section above North American basement into the southeastern Canadian Cordillera, and are thus “nailed” to the craton. These strata are in turn stratigraphically pinned to older (Mesoproterozoic Belt-Purcell Supergroup, Neoproterozoic Windermere Supergroup, and Ediacaran), intermediate-aged (Ordovician–Silurian), and younger (Permian to Middle Jurassic) strata found only in the mountains, thus linking them to the adjacent autochthonous craton. The overlapping distribution of linking successions, regionally traceable unique stratigraphic horizons in the Belt-Purcell and Windermere Supergroups, and across-strike stratigraphic features show that the entire Cariboo, northern Selkirk, Purcell, and Rocky Mountains are directly tied to the adjacent North American craton without discernible strike-slip or oblique displacement, or substantial purely convergent plate-scale (>400 km) horizontal displacement. They link the entire width of the Belt-Purcell and Windermere basins in the southeastern Canadian Cordillera to the adjacent craton and show that any proposed Cretaceous ribbon continent suture, with its thousands of kilometers of proposed displacement, cannot run through the southeastern Canadian Cordillera.

Source Parameters of Large Australian Intracontinental Earthquakes

1988 ◽  
Vol 59 (4) ◽  
pp. 315-315
Author(s):  
Robert McCaffrey ◽  
Joanne Fredrich
Keyword(s):  
Continental Margin ◽  
Source Parameters ◽  
Strike Slip ◽  
Thrust Faulting ◽  
Long Period ◽  
The Past ◽  
Preliminary Examination ◽  
Short Period ◽  
Australian Continent ◽  
Large Earthquakes

Abstract We have examined the largest earthquakes in the Australian continent over the past 20 years by modeling their teleseismic long-period P and SH and short-period P waveforms. Eight earthquakes beneath the continent show thrust faulting at depths shallower than 10 km. Three (1, 2, 4 below) produced surface faulting and their waveforms indicate centroid depths of 3 km or less. The P-axes in the southwestern half of the continent have easterly trends. Preliminary examination of the 3 large earthquakes near Tennant Creek on 22 January, 1988, (7–9) indicate thrusting at less than 10 km depth, but with N-trending P-axes. The largest event (9), at 12:06 GMT, had a seismic moment of roughly 1019 Nm, which makes it comparable in size to the 1968 Meckering event (1). One event (6) beneath the continental margin indicates strike-slip at 26 km depth.

Jurassic location of the Yukon-Tanana Terrane from paleomagnetism of the folded Mississippian Tatlmain Batholith and Ragged Stock

2019 ◽  
Author(s):  
D T A Symons ◽  
K Kawasaki
Keyword(s):  
British Columbia ◽  
North America ◽  
Fault Zone ◽  
Early Cretaceous ◽  
Rocky Mountain ◽  
Early Jurassic ◽  
Canadian Cordillera ◽  
Clockwise Rotation ◽  
Thrust Faulting ◽  
Host Rocks

Summary The extensive Yukon-Tanana terrane of the northern Canadian Cordillera has been considered controversially to be part of the allochthonous ‘Baja B.C.’ microcontinent or of the para-autochthonous North American cratonic margin during the Mesozoic. Paleomagnetic methods have isolated a very-stable Early Jurassic thermochemical remanent remagnetization in the terrane's felsic Tatlmain batholith and mafic Ragged stock after correction for: 1) rotation from northeast-plunging anticlinal deformation; 2) northerly dipping tectonic tilt of the host rocks; and, 3) northwestward regional translation on the adjacent Tintina transcurrent fault zone. The resulting 196 ± 6 Ma Tatlmain and Ragged paleopoles are 64.9° N, 44.8° E (A95 = 5.9°) and 64.2° N, 58.5° E (A95 = 7.7°), respectively. The YTT paleopoles support para-autochthonous tectonic models that have the YTT: 1) accreting to North America by the Early Jurassic; 2) undergoing non-significant orogen-perpendicular shortening by mid-Early Cretaceous from thrust-faulting; and, then 3) undergoing significant orogen-parallel northward translation of ∼500 km from mid-Early Cretaceous to the Eocene. In contrast, the paleopoles for Stikinia and Quesnellia of the Intermontane Belt show progressive northwestward translation relative to North America by ∼1000 km and a rotation of ∼55° cw since mid-Early Cretaceous. We speculate that ∼500 km of the northward translation is related to dextral motion on the Tintina and Northern Rocky Mountain Trench fault in British Columbia, and that the clockwise rotation is related to upper crustal tectonics in both Yukon and southern British Columbia.

The Canadian Cordillera, the Hellenides, and the Sea-Floor Spreading Theory

1972 ◽  
Vol 9 (6) ◽  
pp. 709-743 ◽  
Author(s):  
Jean Dercourt
Keyword(s):  
Pacific Ocean ◽  
Oceanic Crust ◽  
Continental Margin ◽  
Middle Jurassic ◽  
Late Jurassic ◽  
Late Triassic ◽  
Canadian Cordillera ◽  
Transform Faults ◽  
Sea Floor ◽  
Sea Floor Spreading

The theory of plate tectonics is applied to the tectonic evolution of the Hellenides and the Canadian Cordillera. In the Hellenides a Tethyan zone of sea-floor spreading developed within the continental crust during Triassic time and functioned until the end of the Middle Jurassic. It led to the formation of two plates, each with continental and oceanic segments, that were separated in some places by accreting plate margins and in others by transform faults. In Late Jurassic time the mid-Tethyan ridge became inactive as new ridges developed in the Atlantic Ocean. From Late Jurassic to Recent time, Tethyan oceanic crust largely disappeared under one of the cratons. The chronology of tectonic events in the Hellenides corresponds well with that of sea-floor spreading in the Atlantic.Four periods of sea-floor spreading were involved in the formation of the Canadian Cordillera: (1) a Silurian? to Early Devonian period when an Archeo-Pacific Ocean separated the Canadian craton with a stable sedimentary margin from a volcanic archipelago; (2) a Middle Devonian to Permian period when the extinct volcanic archipelago was bounded to the west by a spreading Paleo-Pacific Ocean, and to the east by a tectonic contact which was consuming Archeo-Pacific oceanic crust; part of this crust was obducted over the continental margin; (3) a Late Triassic to Middle Jurassic period when a second volcanic archipelago separated a spreading Neo-Pacific Ocean from the continental margin; and (4) a Late Jurassic to Recent period where spreading occurred in both the Atlantic and Pacific Oceans, subjecting the second volcanic archipelago and the continental margin to major tectonism; since the Paleocene, the Cordillera has slid towards the NNW along transform faults.

The McNaughton Lake earthquake of May 14, 1978

1980 ◽  
Vol 70 (5) ◽  
pp. 1771-1786
Author(s):  
Garry C. Rogers ◽  
Robert M. Ellis ◽  
Henry S. Hasegawa
Keyword(s):  
North America ◽  
Focal Depth ◽  
Rocky Mountain ◽  
Aftershock Sequence ◽  
Strike Slip ◽  
Eastern North America ◽  
Canadian Cordillera ◽  
Large Reservoir ◽  
Induced Earthquake ◽  
The Moment

abstract At 22h37m02s UTC on May 14, 1978, a magnitude (ML) 4.8 earthquake occurred in the Canadian Rockies near McNaughton Lake, the large reservoir behind the Mica Dam in eastern British Columbia. The data suggest it was not a reservoir-induced earthquake. The earthquake was within a seismic array monitoring the reservoir and consequently, the epicenter is well constrained in a northwest-southeast direction. The preferred epicenter is 52.65°N, 118.89°W, slightly east of the Rocky Mountain Trench, with a shallow focal depth of about 10 km. There were no foreshocks but a normal aftershock sequence. The focal mechanism, the first for the eastern Canadian Cordillera, indicates predominantly right-lateral strike-slip faulting along the strike of the mountains with a significant thrust component. The moment is 4 ± 2 × 1023 dyne-cm with a low stress drop (<10 bars). A well-developed Lg phase was recorded to the south of the earthquake. The isoseismals are elongated in a north-south direction and the rate with which intensity attenuates in a southerly direction is comparable to that for eastern North America.

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