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.

Macroflora, paleogeography, and paleoecology of the Upper Cretaceous (Turonian?–Santonian) Saanich Member of the Comox Formation, Saanich Peninsula, British Columbia, Canada

2015 ◽  
Vol 52 (7) ◽  
pp. 519-536 ◽  
Author(s):  
Carl H.W. Jonsson ◽  
Richard J. Hebda
Keyword(s):  
British Columbia ◽  
North America ◽  
Upper Cretaceous ◽  
Barrier Island ◽  
Vancouver Island ◽  
Plant Macrofossil ◽  
Insight Into

Morphotypes of plant macrofossil assemblages of the basal unit of the Upper Cretaceous (Turonian?–Santonian) Comox Formation, Nanaimo Group, Vancouver Island, were investigated to provide insight into the character of the macroflora, environment of deposition, and paleogeography of Vancouver Island. Three floristic assemblages were documented: one dominated by angiosperm morphotypes such as Platanus, Menispermites, and Zizyphus-like leaves; another dominated by gymnosperm morphotypes such as those synonymous with Glyptostrobus comoxensis Bell and Pseudoctenis latipennis (Heer) Seward; and a third assemblage transitional between the previous two. These assemblages suggest the Saanich Member was likely deposited in a barrier island – estuarine floodplain complex with fluvial sedimentary input. The macrofloral assemblage also includes many endemic taxa, suggesting a barrier to floral migration between the paleocontinent and the Vancouver Island precursor during the Upper Cretaceous, which supports the existence of a third floristic province in North America during the Upper Cretaceous.

Angiosperm wood from the Upper Cretaceous (Coniacian) of British Columbia, Canada

IAWA Journal ◽  
2017 ◽  
Vol 38 (2) ◽  
pp. 141-161 ◽  
Author(s):  
Nathan A. Jud ◽  
Elisabeth A. Wheeler ◽  
Gar W. Rothwell ◽  
Ruth A. Stockey
Keyword(s):  
British Columbia ◽  
North America ◽  
Late Cretaceous ◽  
Upper Cretaceous ◽  
Vancouver Island ◽  
Growth Rings ◽  
Thin Sections ◽  
Marine Deposits ◽  
Dry Wood ◽  
Cretaceous Deposits

Fossil angiosperm wood was collected from shallow marine deposits in the Upper Cretaceous (Coniacian) Comox Formation on Vancouver Island, British Columbia, Canada. The largest specimen is a log at least 2 m long and 38 cm in diameter. Thin sections from a sample of this log reveal diffuseporous wood with indistinct growth rings and anatomy similar toParaphyllanthoxylon. Occasional idioblasts with dark contents in the rays distinguish this wood from previously knownParaphyllanthoxylonspecies and suggest affinity with Lauraceae. The log also includes galleries filled with dry-wood termite coprolites. This trunk reveals the presence of tree-sized angiosperms in what is now British Columbia, and the association of dry-wood termites with angiosperm woods by the Coniacian (89 Ma). To understand the significance of this discovery, we reviewed the record of Cretaceous woods from North America. Our analysis of the distribution of fossil wood occurrences from Cretaceous deposits supports the conclusion that there was a strong latitudinal gradient in both the size and distribution of angiosperm trees during the Late Cretaceous, with no reports of Cretaceous angiosperm trees north of 50°N paleo-latitude in North America. The rarity of angiosperm wood in the Cretaceous has long been used to support the idea that flowering plants were generally of low-stature for much of the Cretaceous; however, large-stature trees withParaphyllanthoxylon-like wood anatomy were widespread at lower–middle paleo-latitudes at least in North America during the Late Cretaceous. Thus, the presence of a largeParaphyllanthoxylonlog in the Comox Formation suggests that Vancouver Island has moved significantly northward since the Coniacian as indicated by other geological and paleobotanical studies.

Paleomagnetism of the Triassic Nikolai Greenstone, McCarthy Quadrangle, Alaska

1977 ◽  
Vol 14 (11) ◽  
pp. 2578-2592 ◽  
Author(s):  
J. W. Hillhouse
Keyword(s):  
British Columbia ◽  
High Temperature ◽  
North America ◽  
Vertical Axis ◽  
Upper Triassic ◽  
Present Position ◽  
Stable Component ◽  
South Central ◽  
Early Mesozoic ◽  
Lamellar Texture

Paleomagnetic evidence indicates that the extensive early Mesozoic basalt field near McCarthy, south-central Alaska, originated far south of its present position relative to North America. Results obtained from the Middle and (or) Upper Triassic Nikolai Greenstone suggest that those basalts originated within 15° of the paleoequator. This position is at least 27° (3000 km) south of the Upper Triassic latitude predicted for McCarthy on the basis of paleomagnetic data from continental North America. The Nikolai pole, as determined from 50 flows sampled at 5 sites, is at 2.2° N, 146.1° E (α95 = 4.8°). The polarity of the pole is ambiguous, because the corresponding magnetic direction has a low inclination and a westerly declination. Therefore, the Nikolai may have originated near 15° N latitude or, alternatively, as far south as 15° S latitude. In addition to being displaced northward, the Nikolai block has been rotated roughly 90° about the vertical axis. A measure of the reliability of this pole is provided by favorable results from the following tests: (1) Within one stratigraphic section, normal and reversed directions from consecutive flows are antipolar. (2) Consistent directions were obtained from sites 30 km apart. (3) Application of the fold test indicated the magnetization was acquired before the rocks were folded. (4) The magnetizations of several pilot specimens are thermally stable up to 550 °C. The stable component is probably carried by magnetite with lamellar texture, a primary feature commonly acquired by a basalt at high temperature during initial cooling of the magma. Geologic and paleomagnetic evidence indicates that the Nikolai is allochthonous to Alaska and that, together with associated formations in southern Alaska and British Columbia, it is part of a now disrupted equatorial terrane.

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.

A new species of Petrolisthes STIMPSON, 1858 (Anomura, Porcellanidae) from the Upper Cretaceous (upper Santonian) of Vancouver Island, Canada

2020 ◽  
Vol 298 (1) ◽  
pp. 1-8
Author(s):  
Alessandro Garassino ◽  
Torrey Nyborg ◽  
John Fam ◽  
Dan Bowden ◽  
Raymond Graham ◽  
...  
Keyword(s):  
British Columbia ◽  
New Species ◽  
Upper Cretaceous ◽  
Vancouver Island ◽  
Geographical Range ◽  
Northeastern Pacific ◽  
A New Species

A new porcellanid crab, Petrolisthes landsendi Garassino & Nyborg n. sp., from the Upper Cretaceous (upper Santonian) Nanaimo Group of Vancouver Island (British Columbia, Canada) is herein described. Petrolisthes landsendi Garassino & Nyborg n. sp. represents the oldest species of Petrolisthes Stimpson, 1858 and is the first species from the northeastern Pacific, thus expanding the stratigraphical age and geographical range of the genus.

Review: Receiver function studies in the southern Canadian Cordillera

1995 ◽  
Vol 32 (10) ◽  
pp. 1514-1519 ◽  
Author(s):  
John F. Cassidy
Keyword(s):  
British Columbia ◽  
Upper Mantle ◽  
Receiver Function ◽  
Vancouver Island ◽  
Moho Depth ◽  
Canadian Cordillera ◽  
Low Velocity ◽  
Strait Of Georgia ◽  
Low Velocity Zone ◽  
Velocity Zone

Receiver function analysis has proven to be a powerful, yet inexpensive tool for estimating the S-wave velocity structure of the crust and upper mantle beneath three-component seismograph stations in the southern Canadian Cordillera. Receiver function studies using a portable broadband seismograph array across southwestern British Columbia provided site-specific estimates for the location of the subducting Juan de Fuca plate. The oceanic crust was imaged at 47−53 km beneath central Vancouver Island, and 60–65 km beneath the Strait of Georgia. Further, these studies revealed a prominent low-velocity zone (VS = −1.0 km/s) that coincides with the E reflectors imaged ~5–10 km above the subducting plate on Lithoprobe reflection lines. The E low-velocity zone was shown to extend into the upper mantle beneath the Strait of Georgia and the British Columbia mainland, to depths of 50–60 km. Combining the receiver function and refraction models revealed a high Poisson's ratio (0.27–0.38) for this feature. The continental Moho was estimated at 36 km beneath the Strait of Georgia, and a crustal low-velocity zone associated with the Lithoprobe C reflectors beneath Vancouver Island was interpreted to extend eastward, near the base of the continental crust, to the British Columbia mainland. Analysis of data from the recently deployed Canadian National Seismograph Network demonstrates the variations in crustal thickness and complexity across the southern Canadian Cordillera, with the Moho depth varying from 35 km in the Coast Mountains, to 33 km near Penticton, to 50 km near the Rocky Mountain deformation front.

A Review of Geophysical Studies in the Canadian Cordillera

1971 ◽  
Vol 8 (7) ◽  
pp. 788-801 ◽  
Author(s):  
M. J. Berry ◽  
W. R. Jacoby ◽  
E. R. Niblett ◽  
R. A. Stacey
Keyword(s):  
British Columbia ◽  
Heat Flow ◽  
Rocky Mountain ◽  
The United States ◽  
Vancouver Island ◽  
Geophysical Data ◽  
Fault System ◽  
Canadian Cordillera ◽  
Crust And Upper Mantle ◽  
Juan De Fuca

Geophysical studies of the crust and upper mantle have been conducted in the Canadian Cordillera for over two decades, but only recently have sufficient data been collected to permit a synthesis and a correlation with the major geological units. The studies have included gravity, heat flow, and magnetotelluric observations, geomagnetic depth sounding, and high level aeromagnetics as well as both small and large scale refraction and reflection seismic surveys.It now appears that major crustal units may be recognized geophysically:(i) Seismic and gravity data suggest that the Plains and Rocky Mountains are underlain by two units of the North American craton with a crustal section 45–50 km thick. The northern unit appears to terminate at the Rocky Mountain Trench while the southern unit may extend to the Omineca Geanticline.(ii) The combined geological and geophysical data suggest that the Rocky Mountain Trench and possibly the Kootenay Arc near the 49th parallel mark the edge of the Precambrian continental margin and that the western Cordillera was formed by a complex succession of plate interactions with repeated reactivation of block boundaries.(iii) A combination of magnetic and heat flow data suggest that the region between the Rocky Mountain Trench and the Fraser Lineament is part of the Cordilleran Thermal Anomaly Zone recognized by Blackwell in the United States.(iv) Seismic data in Central British Columbia suggest that the Pinchi Fault system is a boundary between two crustal blocks.(v) The crustal thickness of the Coast Geanticline appears to increase gradually to the west to approximately 40 km and, at least in southern British Columbia, does not have a root zone below the mountains.(vi) The crustal section beneath Vancouver Island is abnormally thick and there is some paleomagnetic data which suggest that the Island may not have been formed in its present position, contiguous to the Cordillera. The crustal section for the northern part of the Insular Trough is significantly thinner.(vii) The active spreading of the Juan de Fuca Rise – Explorer Trench is now well documented. The geophysical data suggest active subduction of the Juan de Fuca plate beneath Oregon, Washing-ton, and southern Vancouver Island. However, further north there is no evidence for subduction.

A New Species of Bradyidius (Copepoda: Calanoida) from the Pacific Coast of North America

1966 ◽  
Vol 23 (6) ◽  
pp. 805-811 ◽  
Author(s):  
Tai Soo Park
Keyword(s):  
British Columbia ◽  
New Species ◽  
North America ◽  
Pacific Coast ◽  
Vancouver Island ◽  
Saanich Inlet ◽  
The Pacific ◽  
A New Species

A new species Bradyidius saanichi from Saanich Inlet, Vancouver Island, British Columbia, Canada, is described and illustrated in detail. This species is closely related to B. pacificus (Brodsky, 1950) among the six previously known species in the genus, but can be readily distinguished from the latter by the strongly divergent rostral rami in addition to some other differences.

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.

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