Total field marine magnetic data, offshore British Columbia [West Coast 1981 survey]

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.

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Constrained 3D inversion of magnetic data with structural orientation and borehole lithology: A case study in the Macheng iron deposit, Hebei, China

Geophysics ◽

10.1190/geo2018-0257.1 ◽

2019 ◽

Vol 84 (2) ◽

pp. B121-B133 ◽

Cited By ~ 4

Author(s):

Shida Sun ◽

Chao Chen ◽

Yiming Liu

Keyword(s):

Remanent Magnetization ◽

Magnetic Data ◽

Iron Deposit ◽

Reference Field ◽

Total Field ◽

Equivalent Source ◽

Structural Orientation ◽

Amplitude Data ◽

Ore Bodies

We have developed a case study on the use of constrained inversion of magnetic data for recovering ore bodies quantitatively in the Macheng iron deposit, China. The inversion is constrained by the structural orientation and the borehole lithology in the presence of high magnetic susceptibility and strong remanent magnetization. Either the self-demagnetization effect caused by high susceptibility or strong remanent magnetization would lead to an unknown total magnetization direction. Here, we chose inversion of amplitude data that indicate low sensitivity to the direction of magnetization of the sources when constructing the underground model of effective susceptibility. To reduce the errors that arise when treating the total-field anomaly as the projection of an anomalous field vector in the direction of the geomagnetic reference field, we develop an equivalent source technique to calculate the amplitude data from the total-field anomaly. This equivalent source technique is based on the acquisition of the total-field anomaly, which uses the total-field intensity minus the magnitude of the reference field. We first design a synthetic model from a simplified real case to test the new approach, involving the amplitude data calculation and the constrained amplitude inversion. Then, we apply this approach to the real data. The results indicate that the structural orientation and borehole susceptibility bounds are compatible with each other and are able to improve the quality of the recovered model to obtain the distribution of ore bodies quantitatively and effectively.

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The nootka and sandwich vocabularies in the relación de la entrada de san lorenzo de nutka (1789)

Language Typology and Universals ◽

10.1524/stuf.2013.0016 ◽

2013 ◽

Vol 66 (3) ◽

Author(s):

Rebeca Fernández Rodríguez

Keyword(s):

British Columbia ◽

West Coast ◽

Vancouver Island ◽

The West ◽

San Lorenzo

AbstractNootka is an historical fur-trading centre in Yuquot, on the west coast of Vancouver Island, British Columbia, Canada. In 1788, the Spanish king Charles III sent an expedition to Nootka commanded by Ignacio Arteaga (1731-1783). A year later, Spain established a military post, San Lorenzo de Nutka, at Yuquot in 1789 which existed until 1795. The missionaries who arrived with the sailors were urged to learn the vernacular languages in order to evangelize. In chapter 5 of the

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A Model of Seawater Structure Near the West Coast of Vancouver Island, British Columbia

Journal of the Fisheries Research Board of Canada ◽

10.1139/f63-065 ◽

1963 ◽

Vol 20 (4) ◽

pp. 939-967 ◽

Cited By ~ 3

Author(s):

Robert K. Lane

Keyword(s):

British Columbia ◽

West Coast ◽

Large Scale ◽

Coastal Region ◽

Vancouver Island ◽

Structural Elements ◽

The West ◽

Characteristic Structure ◽

Oceanographic Data ◽

Vertical Sections

Oceanographic data collected in a line of stations extending seaward of the west coast of Vancouver Island, British Columbia, were reviewed and analyzed. On the basis of these data and the large-scale meteorological processes of wind, insolation, and precipitation, the characteristic structure of temperature and salinity in the coastal region was denned in five temporal stages throughout the year. These stages are presented as vertical sections along the line with characteristic ranges of values to be found in each of the structural elements.

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Gyrodiform gastropods from the Pacific Coast Cretaceous and Paleocene

Journal of Paleontology ◽

10.1017/s0022336000028225 ◽

1987 ◽

Vol 61 (1) ◽

pp. 70-100 ◽

Cited By ~ 19

Author(s):

W. P. Popenoe ◽

L. R. Saul ◽

Takeo Susuki

Keyword(s):

British Columbia ◽

New Taxa ◽

Late Cretaceous ◽

West Coast ◽

Pacific Coast ◽

Northern California ◽

Color Patterns ◽

New Subgenus ◽

The Pacific

Seven previously described and seven new taxa of gyrodiform naticoids from West Coast Late Cretaceous–Paleocene age strata are discussed. Gyrodes (Gyrodes) dowelli White of Turonian age is a typical Gyrodes; G. robustus Waring from the Paleocene has the shape of Gyrodes s.s. but lacks the crenulations. G. greeni Murphy and Rodda, G. yolensis n. sp., G. quercus n. sp., G. banites n. sp., G. canadensis Whiteaves, G. pacificus n. sp., and G. expansus Gabb comprise the new subgenus Sohlella, which thus ranges from Cenomanian through Maastrichtian. Gyrodes robsauli n. sp. resembles “Polinices” (Hypterita) helicoides (Gray), and Hypterita is reassigned to the Gyrodinae as a subgenus of Gyrodes. Gyrodes onensis n. sp. of Albian age is similar to the G. americanus group of Sohl (1960). Three texa—Natica allisoni (Murphy and Rodda) of Cenomanian age and N. conradiana Gabb and N. conradiana vacculae n. subsp. of Turonian age—which have all been previously considered to be Gyrodes are placed in Natica. Well marked relict color patterns on N. conradiana and N. conradiana vacculae suggest that these naticids from northern California and southern British Columbia were tropical forms.Diversity of taxa and size of specimens are reduced at the end of the Turonian, suggesting a change in West Coast marine conditions at that time.

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