McNaughton Lake seismicity—more evidence for an Anahim hotspot?

1981 ◽  
Vol 18 (4) ◽  
pp. 826-828 ◽  
Author(s):  
Garry C. Rogers
Keyword(s):  
British Columbia ◽  
North America ◽  
Coastal Zone ◽  
Volcanic Belt ◽  
Canadian Cordillera ◽  
Lake Region

The only notable concentration of earthquakes in the Canadian Cordillera away from the coastal zone occurs in the McNaughton Lake region of British Columbia, off the eastern end of the Anahim volcanic belt. The association of these two phenomena strengthens the hypothesis that the origin of the Anahim belt is due to North America overriding a mantle hotspot and provides a possible explanation for the concentration and character of the seismicity.

Development of late Paleozoic volcanic arcs in the Canadian Cordillera: an example from the Klinkit Group, northern British Columbia and southern Yukon

2003 ◽  
Vol 40 (7) ◽  
pp. 907-924 ◽  
Author(s):  
Renée-Luce Simard ◽  
Jaroslav Dostal ◽  
Charlie F Roots
Keyword(s):  
British Columbia ◽  
North America ◽  
Volcanic Rocks ◽  
Late Paleozoic ◽  
Canadian Cordillera ◽  
Alkali Basalts ◽  
The North ◽  
Pacific Margin ◽  
North American Craton ◽  
Arc Setting

The late Paleozoic volcanic rocks of the northern Canadian Cordillera lying between Ancestral North America to the east and the accreted terranes of the Omineca belt to the west record early arc and rift magmatism along the paleo-Pacific margin of the North American craton. The Mississippian to Permian volcano-sedimentary Klinkit Group extends discontinuously over 250 km in northern British Columbia and southern Yukon. The two stratotype areas are as follows: (1) in the Englishman Range, southern Yukon, the English Creek Limestone is conformably overlain by the volcano-sedimentary Mount McCleary Formation (Lower Clastic Member, Alkali-Basalt Member and Volcaniclastic Member), and (2) in the Stikine Ranges, northern British Columbia, the Screw Creek Limestone is conformably overlain by the volcano-sedimentary Butsih Formation (Volcaniclastic Member and Upper Clastic Member). The calc-alkali nature of the basaltic volcaniclastic members of the Klinkit Group indicates a volcanic-arc setting ((La/Yb)N = 2.77–4.73), with little involvement of the crust in their genesis (εNd = +6.7 to +7.4). Alkali basalts in the Mount McCleary Formation ((La/Yb)N = 12.5–17.8) suggest periodic intra-arc rifting events. Broadly coeval and compositionally similar volcano-sedimentary assemblages occur in the basement of the Mesozoic Quesnel arc, north-central British Columbia, and in the pericratonic Yukon–Tanana composite terrane, central Yukon, suggesting that they all represent pieces of a single long-lived, late Paleozoic arc system that was dismembered prior to its accretion onto Ancestral North America. Therefore, Yukon–Tanana terrane is possibly the equivalent to the basement of Quesnel terrane, and the northern Quesnel terrane has a pericratonic affinity.

Magnetism and age of the Porteau Pluton, southern Coast Belt, British Columbia: evidence for tilt and translation

1995 ◽  
Vol 32 (4) ◽  
pp. 380-392 ◽  
Author(s):  
E. Irving ◽  
J. Baker ◽  
N. Wright ◽  
C. J. Yorath ◽  
R. J. Enkin ◽  
...  
Keyword(s):  
British Columbia ◽  
North America ◽  
Coercive Force ◽  
The Body ◽  
Canadian Cordillera ◽  
Southern Coast ◽  
The South ◽  
The West ◽  
Zircon Age ◽  
Minimum Estimate

The Porteau Pluton is a variably foliated quartz diorite to granodiorite intrusion in the southern Coast Belt of the Canadian Cordillera (49.6°N, 123.2°W). 40Ar/39Ar ages are 95 ± 5 Ma from biotite and 101.5 ± 0.7 Ma from hornblende, which, together with an earlier U–Pb zircon age of 100 ± 2 Ma, indicate that the body was emplaced, uplifted, and cooled rapidly in mid-Cretaceous time. The rocks contain high coercive force (hard) remanent magnetizations with unblocking temperatures between 500 and 600 °C, close to those of Ar in hornblende, indicating that remanence was acquired at or close to the hornblende plateau age. The hard remanence directions have an elongate distribution, in agreement with the predictions of M.E. Beck regarding magnetization acquired during tilting, uplift, and cooling of plutons. No part of the distribution agrees with the direction expected from observations from rocks of mid-Cretaceous age from cratonic North America. The elongate distribution defines the axis of tilt (347° east of north) but not its direction; tilt could have been down toward the east or down toward the west. The former yields an inclination that is 29.0 ± 4.9° shallower than expected from cratonic observations, corresponding to a displacement from the south of 3200 ± 500 km. The latter reconstruction yields an inclination that is anomalously shallow by 14.8 ± 3.9°, corresponding to a displacement from the south of 1600 ± 400 km, which is a minimum estimate. It is argued, therefore, that the Porteau Pluton has undergone both tilt and displacement from the south by distances substantially in excess of 1000 km.

Paleomagnetism of the Upper Cretaceous Nanaimo Group, southwestern Canadian Cordillera

2001 ◽  
Vol 38 (10) ◽  
pp. 1403-1422 ◽  
Author(s):  
Randolph J Enkin ◽  
Judith Baker ◽  
Peter S Mustard
Keyword(s):  
British Columbia ◽  
North America ◽  
Upper Cretaceous ◽  
Vertical Axis ◽  
Vancouver Island ◽  
Canadian Cordillera ◽  
Paleontological Data ◽  
The Mean ◽  
Prime Target

The Baja B.C. model has the Insular Superterrane and related entities of the Canadian Cordillera subject to >3000 km of northward displacement with respect to cratonic North America from ~90 to ~50 Ma. The Upper Cretaceous Nanaimo Group (on and about Vancouver Island, British Columbia) is a prime target to test the model paleomagnetically because of its locality and age. We have widely sampled the basin (67 sites from seven islands spread over 150 km, Santonian to Maastrichtian age). Most samples have low unblocking temperatures (<450°C) and coercivities (~10 mT) and strong present-field contamination, forcing us to reject three quarters of the collection. Beds are insufficiently tilted to provide a conclusive fold test, and we see evidence of relative vertical axis rotations. However, inclination-only analysis indicates pretilting remanence is preserved for many samples. Both polarities are observed, and reversals correlate well to paleontological data, proving that primary remanence is observed. The mean inclination, 55 ± 3°, is 13 ± 4° steeper than previously published results. Our new paleolatitude, 35.7 ± 2.6° is identical to that determined from the slightly older Silverquick and Powell Creek formations at Mount Tatlow, yet the inferred displacement is smaller (2300 ± 400 km versus 3000 ± 500 km) because North America was drifting southward starting around 90 Ma. The interpreted paleolatitude conflicts with sedimentologic and paleontologic evidence that the Nanaimo Basin was deposited near its present northern position.

The occurrence of the hydrozoan genus Cassianastraea from Upper Triassic (Carnian) rocks of Williston Lake, British Columbia, Canada

2011 ◽  
Vol 85 (1) ◽  
pp. 29-31
Author(s):  
George D. Stanley ◽  
John-Paul Zonneveld
Keyword(s):  
British Columbia ◽  
North America ◽  
Coral Reefs ◽  
North American ◽  
Upper Triassic ◽  
Geological Survey ◽  
The North ◽  
Lake Region ◽  
First Occurrence ◽  
North American Craton

Cassianastraea is an enigmatic colonial Triassic cnidarian first described as a coral but subsequently referred to the Hydrozoa. We report here the first occurrence in Canada of fossils we designate as Cassianastraea sp. from the Williston Lake region of British Columbia. The specimens come from older collections of the Geological Survey of Canada, collected in Upper Triassic (Carnian) strata assigned to either the Ludington or Baldonnel Formations. While well known in reef associations of the former Tethys region, Cassianiastraea is relatively rare in North America. The Carnian Baldonnel Formation contains the earliest coral reefs from the North American craton and we suspect that Cassianastraea sp. also came from this reef association.

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.

Taxonomy and nomenclature of rough fescues, Festuca altaica, F. campestris (F. scabrella var. major), and F. hallii, in Canada and the adjacent part of United States

1984 ◽  
Vol 62 (8) ◽  
pp. 1739-1749 ◽  
Author(s):  
Leon E. Pavlick ◽  
Jan Looman
Keyword(s):  
United States ◽  
British Columbia ◽  
North America ◽  
Canadian Cordillera ◽  
Eastern Asia ◽  
Eastern Canada ◽  
Adjacent Part ◽  
Gaspe Peninsula ◽  
Gaspé Peninsula ◽  
Prairie Provinces

Three species of rough fescues occur in Canada and the adjacent part of the U.S.A.: Festuca altaica, F. campestris (F. scabrella var. major), and F. halli. Festuca altaica, a wide-ranging species of eastern Asia and northern North America, extends southward in the Canadian Cordillera to about latitude 52° N and is disjunct in eastern Canada (northern Québec, Gaspé Peninsula, western Newfoundland, etc.). Festuca scabrella Torr. in Hook, is a synonym of the earlier published F. altaica Trin. in Ledeb. Rough fescues of southern British Columbia, the southern prairie provinces of Canada, and northwestern U.S.A. that have been called F. scabrella belong to F. campestris and F. hallii, a neglected species. A key to the three taxa and a map of their distribution is presented.

Nazko cone: a Quaternary volcano in the eastern Anahim Belt

1987 ◽  
Vol 24 (12) ◽  
pp. 2477-2485 ◽  
Author(s):  
J. G. Souther ◽  
J. J. Clague ◽  
R. W. Mathewes
Keyword(s):  
British Columbia ◽  
North America ◽  
Volcanic Activity ◽  
Mantle Source ◽  
Volcanic Belt ◽  
Lava Flows ◽  
Radiocarbon Dates ◽  
Depleted Mantle ◽  
Late Neogene ◽  
Cordilleran Ice Sheet

Nazko cone, located in central British Columbia at the eastern end of the Anahim Volcanic Belt, is the product of at least three episodes of Quaternary volcanic activity. An eroded Pleistocene subaerial flow at the base of the pile is overlain by a subglacial mound of hyaloclastite that is, in turn, partly covered by a younger composite pyroclastic cone and associated lava flows. A whole-rock K–Ar date of 0.34 ± 0.03 Ma on the oldest flow is consistent with a hotspot model for the Anahim Belt and implies absolute late Neogene motion of 2.6 cm/year for North America. The hyaloclastite mound was erupted beneath the Cordilleran Ice Sheet during the Late Pleistocene, perhaps during the Fraser Glaciation (25 000 – 10 000 years BP). Radiocarbon dates from peat above and below Nazko tephra in a bog near the cone suggest that the volcano last erupted about 7200 years BP.Nazko basalt has 10–15% normative nepheline and is classified as basanite. This is significantly more undersaturated than basalts farther west in the Anahim Belt and may indicate an eastward shift toward a deeper or less depleted mantle source.

Crustal temperatures near the Lithoprobe Southern Canadian Cordillera Transect

1992 ◽  
Vol 29 (6) ◽  
pp. 1197-1214 ◽  
Author(s):  
T. J. Lewis ◽  
W. H. Bentkowski ◽  
R. D. Hyndman
Keyword(s):  
British Columbia ◽  
Heat Flow ◽  
Heat Generation ◽  
Lower Crust ◽  
Volcanic Belt ◽  
The United States ◽  
Canadian Cordillera ◽  
Upper Crust ◽  
Thermal Data ◽  
Seismic Reflectors

Heat flow and radioactive heat generation have been measured and the data compiled across southern British Columbia in the region of the Lithoprobe Southern Canadian Cordillera Transect. Heat flow in the trench-arc zone between the continental margin and the Garibaldi volcanic belt is very low, but in the volcanic belt it is high and very irregular. Farther inland, to the east, the heat flow is moderately high, with the highest values in southeastern British Columbia, associated with high surface radioactive heat production. The thermal data from the central and eastern interior of southern British Columbia define a single heat-flow province with a reduced heat flow of 63 mW/m2 flowing into the upper crust. This indicates a warm, thin lithosphere similar to that of the Basin and Range of the United States to the south. Occurrences of seismic reflective bands in the lower crust of the Cordillera were compared with temperatures calculated from surface heat flow and heat generation using a simple one-dimensional conductive model. The 450 °C isotherm corresponds approximately to the brittle– ductile transition, and deeper crust may be rheologically detached from the upper crust. Where the thermal data approximately coincide with the transect seismic reflection lines, the 450 °C isotherm often corresponds to the top of characteristic sub-horizontal reflector bands, as found in Phanerozoic areas elsewhere around the world. The lower limit of the reflective band in a number of Cordilleran reflection sections is near the 730 °C isotherm, which corresponds to the transition from present "wet" amphibolite- to "dry" granulite-facies conditions. This control of the depth to the deep crustal reflective bands by present temperature provides support for the model of the reflectors being produced by fluids trapped at lithostatic pressure (layered porosity), a model that can also explain the high electrical conductivity in the deep crust of the area. The probable rheological detachment of the lower crust and a possible nonstructural origin of the deep reflectors require that interpreted lower crustal structural boundaries such as the top of the basement of the North American craton under the Lithoprobe Southern Canadian Cordillera Transect be treated with caution. However, there is no doubt that many seismic reflectors are related to crustal structures, and the model is presented as an explanation for bands of seismic reflectors in the lower Phanerozoic crust, not as a model for all seismic reflectors.

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