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.

Palaeomagnetic evidence bearing on the evolution of the Canadian Cordillera

1990 ◽  
Vol 331 (1620) ◽  
pp. 487-509 ◽  
Keyword(s):  
North America ◽  
Canadian Cordillera ◽  
Present Position ◽  
The South ◽  
The West ◽  
Western Cordillera ◽  
Palaeomagnetic Data ◽  
Comparable Magnitude ◽  
Bedded Rocks

Palaeomagnetic data from Permian, Triassic and Jurassic bedded rocks, to which attitudinal corrections can be applied, yield palaeolatitudes concordant with those of ancestral North America, but very large predominantly anticlockwise rotations about vertical axes. Data from Cretaceous rocks yield apparent palaeolatitudinal displacements that increase westward. Small or negligible displacements are obtained from the Omineca Belt. Intermediate displacements (1000-2000 km) from the Intermontane Belt, are based on data from Cretaceous bedded sequences. Further to the west in the Coast Belt, larger apparent displacements (greater than 2000 km) have been obtained from plutons for which no attitudinal control is yet available. Data from Eocene rocks are concordant. Possibilities to consider are as follows: (a) little or no displacement and tilting to the southwest at about 30°; (b) large (greater than 2000 km in the Coast Belt) northward displacement since mid-Cretaceous time preceded by southward displacement of comparable magnitude in Juro-Cretaceous time; (c) lesser (1000-2000 km) overall displacement coupled with variable and lesser tilts to the south and southeast of plutons of the Coast Belt. Under hypothesis (a) the western Cordillera was formed and has remained in approximately its present position relative to ancestral North America; data from bedded volcanics of the Intermontane Belt are not consistent with this hypothesis. From the evidence currently available we favour hypotheses (b) or (c), although more data from bedded sequences are required. It is noteworthy that hypotheses (a) and (c) predict tilt directions that differ by about 90° and hence ought to be distinguishable by geological studies.

scholarly journals Gitksan

2016 ◽  
Vol 46 (3) ◽  
pp. 367-378 ◽  
Author(s):  
Jason Brown ◽  
Henry Davis ◽  
Michael Schwan ◽  
Barbara Sennott
Keyword(s):  
British Columbia ◽  
The South ◽  
The West ◽  
The North

Gitksan (git) is an Interior Tsimshianic language spoken in northwestern British Columbia, Canada. It is closely related to Nisga'a, and more distantly related to Coast Tsimshian and Southern Tsimshian. The specific dialect of Gitksan presented here is what can be called Eastern Gitksan, spoken in the villages of Kispiox (Ansbayaxw), Glen Vowell (Sigit'ox), and Hazelton (Git-an'maaxs), which contrasts with the Western dialects, spoken in the villages of Kitwanga (Gitwingax), Gitanyow (Git-anyaaw), and Kitseguecla (Gijigyukwhla). The primary phonological differences between the dialects are a lexical shift in vowels and the presence of stop lenition in the Eastern dialects. While there exists a dialect continuum, the primary cultural and political distinction drawn is between Eastern and Western Gitksan. For reference, Gitksan is bordered on the west by Nisga'a, in the south by Coast Tsimshian and Witsuwit'en, in the east by Dakelh and Sekani, and in the north by Tahltan (the latter four of these being Athabaskan languages).

The Lower Jurassic phosphorites of southeastern British Columbia and terrane accretion to western North America

1989 ◽  
Vol 26 (8) ◽  
pp. 1612-1616 ◽  
Author(s):  
T. P. Poulton ◽  
J. D. Aitken
Keyword(s):  
British Columbia ◽  
North America ◽  
Oceanic Crust ◽  
West Coast ◽  
Cold Water ◽  
Lower Jurassic ◽  
Depositional Model ◽  
Western North America ◽  
The West ◽  
Terrane Accretion

Sinemurian phosphorites in southeastern British Columbia and southwestern Alberta conform with the "West Coast type" phosphorite depositional model. The model indicates that they were deposited on or near the Early Jurassic western cratonic margin, next to a sea or trough from which cold water upwelled. This suggests that the allochthonous terrane Quesnellia lay well offshore in Sinemurian time. The sea separating Quesnellia from North America was partly floored by oceanic crust ("Eastern Terrane") and partly by a thick sequence of rifted, continental terrace wedge rocks comprising the Purcell Supergroup and overlying Paleozoic sequence. This sequence must have been depressed sufficiently that access of upwelling deep currents to the phosphorite depositional area was not impeded.

RECORDS OF SOME SPECIES OF POLYCHAETA NEW TO BRITISH COLUMBIA AND OF EXTENSIONS IN DISTRIBUTION OF SOME OTHERS

1966 ◽  
Vol 44 (5) ◽  
pp. 839-849 ◽  
Author(s):  
C. Berkeley
Keyword(s):  
British Columbia ◽  
North America ◽  
West Coast ◽  
Vancouver Island ◽  
The Other ◽  
The West ◽  
New Subspecies ◽  
Northeast Pacific ◽  
Considerable Depth ◽  
Geographical Locations

Twenty-five species of Polychaeta recently collected off the coast of British Columbia are discussed. Most were taken in waters of considerable depth off the west coast of Vancouver Island. Sixteen are new to British Columbia. Most of these are known from farther south on the west coast of North America, but some from much shallower depths than those from which they are now recorded; two of them are new to the northeast Pacific; one is a new subspecies. The other nine have been previously known from British Columbia, but they are now recorded from much greater depths than hitherto, or in new geographical locations.

scholarly journals II.—Sketch of the Geology of British Columbia

1881 ◽  
Vol 8 (4) ◽  
pp. 156-162
Author(s):  
George M. Dawson
Keyword(s):  
British Columbia ◽  
North America ◽  
West Coast ◽  
Geological Survey ◽  
Personal Knowledge ◽  
Territorial Disputes ◽  
The West ◽  
Coast Line ◽  
Geological Features

Twenty years ago the region now included in the Province of British Columbia was—with the exception of the coast-line— little known geographically, and quite unknown geologically. From the days of Cook and Vancouver, and the old territorial disputes with the Spaniards, this part of the west coast of North America attracted little attention till the discovery of gold in 1858. As among the first in the field geologically may be mentioned Dr. Hector and Messrs. H. Bauerman and G. Gibbs. The observations of these gentlemen, though bringing to light many facts of interest, were confined to a comparatively small part of the area of the province, and it was not till the inclusion of British Columbia in the Dominion of Canada in 1871 that the systematic operations of the Geological Survey of Canada were extended to this region. Since this date a number of reports treating of the geology of British Columbia have been published, and on these, together with a personal knowledge of the country, obtained during five seasons' work in it in connexion with the Survey, I shall chiefly depend in giving a brief account of the main geological features so far developed.

On a Quartz-porphyry from the Lake District

1924 ◽  
Vol 61 (11) ◽  
pp. 513-515 ◽  
Author(s):  
Sidney Melmore
Keyword(s):  
Igneous Rock ◽  
The Body ◽  
Lake District ◽  
The South ◽  
The West ◽  
Quartz Porphyry ◽  
West Side ◽  
South Side ◽  
The Road

A Small quarry was opened about three years ago at Thwaite Head, which lies between the southern ends of Coniston Lake and Windermere. It is on the west side of the road between that hamlet and Hawkshead, and exposes a nearly vertical sill, 40 feet wide, running E.N.E.-W.S.W. in the Bannisdale slates. On the south side a series of joint-planes running parallel to the bedding of the slates and curving inwards at the top have split the igneous rock into flags, while in the body of the rock the jointing is much coarser, so that it is quarried in large blocks. Both the igneous rock and the slates are much decomposed and friable along the southern junction, and it is here a little galena is said to have been found when the quarry was first opened. This is not improbable, as the old Thwaite Head lead mine is situated not far off on the banks of Dale Park Beck.

POLYCHAETA FROM BRITISH COLUMBIA; WITH A NOTE ON SOME WESTERN CANADIAN ARCTIC FORMS

1962 ◽  
Vol 40 (4) ◽  
pp. 571-577 ◽  
Author(s):  
E. Berkeley ◽  
C. Berkeley
Keyword(s):  
British Columbia ◽  
North America ◽  
West Coast ◽  
Canadian Arctic ◽  
The West

Nine species of Polychaeta collected off the coast of British Columbia are recorded. Two of these (Micromaldane ornithochaeta and Notomastus lineatus var. balanoglossi) have not been reported previously outside Europe, one (Asychis biceps) is new to the west coast of North America, and four are new to British Columbia. Six species are recorded from the neighborhood of Herschell Island in the western Canadian Arctic. All are new to that region, though known from further western seas, and, in three cases (Melaenis loveni, Antinoella sarsi, and Nephthys malmgreni) from the western Canadian Arctic further east.

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.

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.

Kilometre-scale folding in the Teslin zone, northern Canadian Cordillera, and its tectonic implications for the accretion of the Yukon-Tanana terrane to North America

1999 ◽  
Vol 36 (3) ◽  
pp. 479-494 ◽  
Author(s):  
Martin de Keijzer ◽  
Paul F Williams ◽  
Richard L Brown
Keyword(s):  
North America ◽  
Shear Zone ◽  
North American ◽  
Root Zone ◽  
Fault System ◽  
Canadian Cordillera ◽  
The West ◽  
The North ◽  
South Central ◽  
North American Craton

The Teslin zone in south-central Yukon has previously been described as a discrete zone with a steep foliation unique to the zone. It includes the Anvil assemblage and the narrowest portion of the Yukon-Tanana terrane (the Nisutlin assemblage), and is defined by post-accretionary faults: the Big Salmon fault to the west and the d'Abbadie fault system to the east. The zone was interpreted as a lithospheric suture or a crustal-scale transpression zone, and as the root zone of klippen lying on the North American craton to the east. We demonstrate that deformation and metamorphism are the same inside and outside the zone. The steep transposition foliation in the zone, in contrast to adjacent rocks to the east, coincides with the steep limb of a regional F3 structure. This fold has a shallow limb in the easternmost part of the zone and immediately east of the zone. Thus we reject earlier interpretations. If a suture exists between the obducted Anvil and Yukon-Tanana Nisutlin assemblages and North America, it is a shear zone that occurs at the base of the obducted rocks, which has been folded by the F3 fold. However, evidence that this thrust boundary is a lithospheric suture is lacking. A consequence of our interpretation is that North American rocks pass under the eastern Teslin zone and outcrop to the west of the Nisutlin and Anvil assemblages. This geometry precludes the possibility of the Teslin zone being the root zone of the klippen.

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