Melting of heterogeneous mantle in a slab window environment: examples from the middle Tertiary Masset basalts, Queen Charlotte Islands, British Columbia

2001 ◽  
Vol 38 (5) ◽  
pp. 825-838 ◽  
Author(s):  
T S Hamilton ◽  
J Dostal
Keyword(s):  
British Columbia ◽  
Stability Field ◽  
Calc Alkaline ◽  
Tholeiitic Magma ◽  
Queen Charlotte Islands ◽  
The Pacific ◽  
Heterogeneous Mantle ◽  
The Difference ◽  
Ocean Ridge ◽  
Slab Window

Voluminous basalts dominate a middle Tertiary bimodal volcanic assemblage in the Queen Charlotte Islands, British Columbia, Canada. These moderately enriched mid-ocean-ridge basalt (MORB-)like magmas were associated with significant crustal extension related to the subduction of the Pacific–Farallon ridge and the initiation of a slab window environment, which persisted for 35 Ma. These asthenospheric melts were derived from a low degree of melting of a heterogeneous peridotite source mainly in the spinel stability field, as inferred from fractional melting inversion calculations. The basaltic magmas in turn gave rise to both tholeiitic and calc-alkaline volcanic strata up to 3.5 km thick in local grabens. The tholeiitic basalts resemble MORB, with rare-earth element (REE) patterns ranging from slightly depleted to enriched in light REE (LREE). The calc-alkaline basaltic andesites are enriched in LREE, but are not strongly depleted in Nb. The rocks have overlapping Nd, Sr, and Pb isotopic compositions, similar to those of intraplate basalts from the adjacent northeast Pacific seamounts and Cordillera. The difference between the tholeiitic and calc-alkaline rocks is, in part, attributed to polybaric fractional crystallization of different proportions of plagioclase to mafic minerals from a similar tholeiitic magma. This marginal-basin subalkaline volcanic sequence and its genesis describe the slab window environment for the Tertiary tectonics of the western Canadian continental margin and provide a model for older combined tholeiitic and calc-alkaline volcanic successions.

Sediment transfer by shallow landsliding in the Queen Charlotte Islands, British Columbia

2002 ◽  
Vol 39 (2) ◽  
pp. 189-205 ◽  
Author(s):  
Yvonne Martin ◽  
Kenneth Rood ◽  
James W Schwab ◽  
Michael Church
Keyword(s):  
British Columbia ◽  
Pacific Northwest ◽  
Probability Distributions ◽  
Sampling Period ◽  
Sampling Bias ◽  
Drainage Basins ◽  
Physical Mechanisms ◽  
Queen Charlotte Islands ◽  
The Pacific ◽  
Sediment Transfer

Despite the importance of landsliding in routing sediment through mountainous drainage basins, few studies have documented landsliding rates over extended time and space scales. We have investigated landsliding in surficial material in the Queen Charlotte Islands using a large inventory of events, derived from aerial photography, covering an area of 166.7 km2. The mean erosion rate for shallow landsliding is 0.10 mm·a–1, which is at the upper end of shallow landsliding rates observed in the Pacific Northwest and coastal British Columbia, but several orders of magnitude lower than rock-based landsliding rates reported in the literature. Probability distributions for landslide area and volume are somewhat convex in form. Flattening of the curve found at low magnitudes may be due to sampling bias or physical mechanisms inhibiting failure, and the steepening for high values may exist because the sampling period is not long enough to adequately represent large events. Landslides generally initiate on hillslope gradients greater than 0.50–0.60. The largest numbers of landslides occur on south- to southwest-facing slopes and east- to northeast-facing slopes. Most events occur on concave and straight hillslopes in upper-slope positions. Landsliding rates were found not to be affected by rock type. Hillslopes in the Queen Charlotte Islands are often mantled by weathered Quaternary deposits and, hence, landsliding events are not directly controlled by weathering of bedrock. About 31% of landslides identified in this study deposited material in stream reaches, with about 83% of these landslides deposited in reaches with gradients between 3% and 10%.

New evidence for the age of the Skonun Formation, Queen Charlotte Islands, British Columbia

1981 ◽  
Vol 18 (12) ◽  
pp. 1900-1903 ◽  
Author(s):  
N. Champigny ◽  
C. M. Henderson ◽  
G. E. Rouse
Keyword(s):  
British Columbia ◽  
Pacific Northwest ◽  
Middle Miocene ◽  
Early Miocene ◽  
Queen Charlotte Islands ◽  
The Pacific ◽  
New Evidence

Recent palynological, megafaunal, and intrusive evidence from a section low in the Skonun Formation in the Cinola deposit on Graham Island indicates that it was deposited in the late Early Miocene, and that the age of the Skonun ranges up to the early Middle Miocene in outcrop sections on northeastern Graham Island. Correlations are made with several Miocene series of the Pacific Northwest and Alaska.

The lichens and lichenicolous fungi of Haida Gwaii (Queen Charlotte Islands), British Columbia, Canada. 5. A new species of Lecanora from shoreline rocksThis paper is one of a selection of papers published as part of the special Schofield Gedenkschrift.

Botany ◽  
2010 ◽  
Vol 88 (4) ◽  
pp. 352-358 ◽  
Author(s):  
Irwin M. Brodo
Keyword(s):  
British Columbia ◽  
New Species ◽  
Pacific Northwest ◽  
Similar Species ◽  
Haida Gwaii ◽  
Queen Charlotte Islands ◽  
The Pacific ◽  
A New Species ◽  
Selection Of ◽  
Northeast Coast

A species of Lecanora in the L. dispersa group, with a well-developed pale thallus and a granular epihymenium, resembling L. albescens , is found exclusively on shoreline rocks and appears to be new. It is described as Lecanora schofieldii  sp. nov., found mainly in the Pacific Northwest, but also rarely on the northeast coast. Its distinctions from similar species on shoreline rocks are given, together with a key for their identification. The first western record of L. xylophila from rocks is given.

scholarly journals A~nitrogen budget for the Strait of Georgia, British Columbia

2013 ◽  
Vol 10 (4) ◽  
pp. 7135-7169 ◽  
Author(s):  
J. N. Sutton ◽  
S. C. Johannessen ◽  
R. W. Macdonald
Keyword(s):  
British Columbia ◽  
Primary Production ◽  
Isotope Composition ◽  
Nitrogen Isotope ◽  
N Budget ◽  
Strait Of Georgia ◽  
The Pacific ◽  
Coastal Sea ◽  
The Pacific Ocean ◽  
The Difference

Abstract. Balanced budgets for dissolved inorganic N (DIN) and particulate N (PN) were constructed for the Strait of Georgia (SoG), a semi-enclosed coastal sea off the west coast of British Columbia, Canada. The dominant control on the N budget is the advection of DIN into and out of the SoG via Haro Strait. The annual influx of DIN by advection from the Pacific Ocean is 29 990 (±19 500)Mmol yr−1. The DIN flux advected out of the SoG is 24 300 (±15 500)Mmol yr−1. Most of the DIN that enters the SoG (∼23 400 Mmol yr−1) is converted to particulate N (PN) in situ by primary production. However, most of the PN produced by primary production is remineralized (∼22 000 Mmol yr−1) back into DIN within the top 50 m. The PN budget for the SoG was further constrained by nitrogen isotope composition (δ15N) that indicated regional differences in the source of PN. The southern Strait receives a much higher proportion of terrigenous PN, relative to marine PN, than does the northern Strait. The difference is due to the influence of the Fraser River, which discharges 1950 Mmol yr−1 of PN and 1660 Mmol yr−1 of DIN into the southern Strait. The overall anthropogenic contribution of PN and DIN to the SoG is minimal relative to natural sources (>30 000 Mmol yr−1). It is unlikely that the Strait will be affected by eutrophication in the near future, although anthropogenic N sources, such as wastewater outfalls, may have significant local effects.

Growth and Age Determination of the Pacific Edible Crab Cancer magister Dana

1961 ◽  
Vol 18 (5) ◽  
pp. 873-891 ◽  
Author(s):  
T. H. Butler
Keyword(s):  
British Columbia ◽  
Carapace Width ◽  
Age Groups ◽  
Age Determination ◽  
Cancer Magister ◽  
Larval Instars ◽  
Frequency Distributions ◽  
Queen Charlotte Islands ◽  
The Pacific

Of 2,820 early post-larval unsexed crabs collected by small-meshed trawl in two regions of the Queen Charlotte Islands, 1,175 were measured and the 1st and 2nd post-larval instars were identified as modes at 6.9 and 10.0 mm, respectively. Increments of 5 unsexed moulted crabs, carapace widths 6.80 to 9.96 mm, were from 36.3 to 46.5%. A total of 284 males, from 83 to 186 mm, moulted in crab traps, live-wells, and while at large as tagged specimens; 44 females, from 88 to 145 mm, moulted in traps. Using equations of regression of new carapace width on old width for both sexes and starting at the 2nd instar, average carapace widths were calculated for instars 3 to 15. In the width-frequency distributions of 8,145 crabs, separation of stages was sufficient for identification of age-groups. It is estimated that a year after hatching, males reach stage 5 or 6 (24.2 or 31.1 mm); after 2 years stage 11 or 12 (96.6 or 119.5 mm) is attained; after 3 years stage 13 (146.9 mm); after 4 years most males are in the 14th stage (176.2 mm) and above the British Columbia legal size of 165 mm; and generally after 5 years males are in stage 15 (207.5 mm). Growth of females is similar for 2 years, but afterwards is slower.

SAWFLY BIOLOGIES.: I. NEODIPRION TSUGAE MIDDLETON

1936 ◽  
Vol 68 (4) ◽  
pp. 71-79 ◽  
Author(s):  
Geo. R. Hopping ◽  
H. B. Leech
Keyword(s):  
British Columbia ◽  
Pacific Northwest ◽  
Western Hemlock ◽  
Queen Charlotte Islands ◽  
The Pacific

The western hemlock sawfly, Neodiprion tsugae Middleron, first came to our notice from the Queen Charlotte Islands, British Columbia. In 1931, reports of the dying of hemlocks over large areas came from rangers and timber operators of this region. A survey conducted by Mr. W. G. Mathers of the Dominion Entomological Branch, in September and October of that year, indicated that the injury extended over approximately forty square miles. In 1932, the outbreak showed definite signs of subsiding, and had practically disappeared by 1933, although many trees were killed during the peak year of 1931, indicating that this is a primary enemy of western hemlock, and that outbreaks may be expected from time to time in the Pacific Northwest.

Supplemental material: Cenozoic to Recent plate configurations in the Pacific Basin: Ridge subduction and slab window magmatism in western North America

2006 ◽  
Author(s):  
J.K. Madsen ◽  
D.J. Thorkelson ◽  
R.M. Friedman ◽  
D.D. Marshall
Keyword(s):  
North America ◽  
Pacific Basin ◽  
Western North America ◽  
File Size ◽  
Tectonic Model ◽  
Ridge Subduction ◽  
The Pacific ◽  
Northwestern North America ◽  
Slab Window

Geosphere, February 2006, v. 2, p. 11-34, doi: 10.1130/GES00020.1. Movie 1 - Tectonic model for the Pacific Basin and northwestern North America from 53 Ma to 39 Ma. The file size is 1.3 MB.

Experiments on Oral Secretion of the Rocky Mountain Wood Tick, Dermacentor andersoni Stiles (Acarina: Ixodidae)

1957 ◽  
Vol 89 (1) ◽  
pp. 1-5 ◽  
Author(s):  
J. D. Gregson
Keyword(s):  
British Columbia ◽  
Pacific Northwest ◽  
Rocky Mountain ◽  
Dermacentor Variabilis ◽  
Oral Secretion ◽  
Amblyomma Maculatum ◽  
Dermacentor Andersoni ◽  
The Pacific ◽  
Tick Paralysis ◽  
Rocky Mountain Wood Tick

Tick paralysis continues to be one of the most baffling and fascinating tickborne diseases in Canada. It was first reported in this country by Todd in 1912. Since then about 250 human cases, including 28 deaths, have been recorded from British Columbia. Outbreaks in cattle have affected up to 400 animals at a time, with losses in a herd as high as 65 head. Although the disease is most common in the Pacific northwest, where it is caused by the Rocky Mountain wood tick, Dermacentor andersoni Stiles, it has lately been reported as far south as Florida and has been produced by Dermacentor variabilis Say, Amblyomma maculatum Koch, and A. americanum (L.) (Gregson, 1953). The symptoms include a gradual ascending symmetrical flaccid paralysis. Apparently only man, sheep, cattle, dogs, and buffalo (one known instance) are susceptible, but even these may not necessarily be paralysed.

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