Paleomagnetism of the Circum-Ungava Proterozoic Fold Belt (I): Cape Smith Komatiitic Basalts

1975 ◽  
Vol 12 (10) ◽  
pp. 1785-1793 ◽  
Author(s):  
Y. Fujiwara ◽  
E. J. Schwarz
Keyword(s):  
North American ◽  
Pole Position ◽  
Canadian Shield ◽  
Lower Portion ◽  
Hudson Bay ◽  
General Area ◽  
Fold Belt ◽  
Early Proterozoic ◽  
Form Part ◽  
North American Data

A total of 397 oriented cores were taken from pillowed, columnar, and massive basalt of Cape Smith Island in northeastern Hudson Bay and from the adjacent mainland coast of Quebec. The thick series of basalts form part of the Circum-Ungava Proterozoic Belt which is of Aphebian (early Proterozoic) age. The lower portion of the basalt series contains pyrrhotite (Fe7S8) and did not yield useful paleomagnetic results. The magnetization of the upper portion of the series is carried by small quantities [Formula: see text] of magnetite. The directions of magnetization of the samples do not change much during alternating field and thermal washing, and show very good grouping. The available internal evidence on the age of the stable remanence is inconclusive. The pole position (20°N, 162°E, semi-axes of the 95% oval of confidence: 4 °and 5°) after correcting for tilt is about 70° west of the preHudsonian part of the polar wandering curve established from North American data. The uncorrected pole position (16°N, 107°W), which would apply if the magnetization was acquired at the time of the Hudsonian orogeny, is in the general area of paleomagnetic poles for rocks of similar age from other localities of the Canadian Shield.

Paleomagnetism of the Great Slave Supergroup, Northwest Territories, Canada: the Stark Formation

1976 ◽  
Vol 13 (4) ◽  
pp. 563-578 ◽  
Author(s):  
D. K. Bingham ◽  
M. E. Evans
Keyword(s):  
Northwest Territories ◽  
North American ◽  
Geomagnetic Field ◽  
Pole Position ◽  
The West ◽  
Stratigraphic Sequence ◽  
Polar Wander ◽  
Early Proterozoic ◽  
The North ◽  
Polarity Reversals

Paleomagnetic results from 55 sampling sites throughout the Stark Formation are reported. The known stratigraphic sequence of these sites enables the behaviour of the geomagnetic field in these remote times (1750 m.y.) to be elucidated. Two polarity reversals are identified and these represent potentially useful correlative features in strata devoid of index fossils. One of these is investigated in detail and indicates that behaviour of the geomagnetic field during polarity reversals was essentially the same in the early Proterozoic as it has been over the last few million years. The pole position (145°W, 15°S, dp = 3.5, dm = 6.9) lies far to the west of that anticipated from earlier results, implying further complexity of the North American polar wander curve. Possible alternatives to this added complexity are discussed.

Paleomagnetism of the komatiitic basalts of the Ottawa Islands, N.W.T.

1985 ◽  
Vol 22 (4) ◽  
pp. 553-566 ◽  
Author(s):  
K. L. Buchan ◽  
W. R. A. Baragar
Keyword(s):  
North American ◽  
Hudson Bay ◽  
The West ◽  
Magnetization Direction ◽  
Polar Wander ◽  
The North ◽  
Dominant Component ◽  
Apparent Polar Wander Path

The komatiitic basalts of the Ottawa Islands in eastern Hudson Bay are on strike with and believed to form a continuation of similar units of the Cape Smith Belt 150 km to the northeast. Units sampled in the Ottawa Islands all dip gently to the west and hence are not suitable for an internal fold test of their age of magnetization. However, before correcting for the tilt of the lavas, the dominant magnetization direction (D = 207.6°, I = 61.9°, k = 168, α95 = 3.7°) does not differ significantly from the uncorrected magnetization direction reported from the steeply dipping, northwest-facing units at Cape Smith (D = 218°, I = 60°, k = 47, α95 = 4°). This negative fold test suggests that the remanence at both locations was acquired after folding. Comparison with the North American Precambrian apparent polar wander path implies that overprinting is related to the Hudsonian Orogeny.A second stable magnetization directed to the west with a shallow inclination is superimposed on the dominant component at a number of sampling sites. Its direction is poorly defined and no fold test is possible. However, magnetic evidence suggests that this component was probably acquired as an overprint after the dominant magnetization, perhaps during a mild reheating associated with the Elsonian Orogeny.

Evaluating the safety of bariatric surgery for weight loss in class I obesity: A propensity-matched analysis of North American data

2019 ◽  
Vol 15 (4) ◽  
pp. 629-635 ◽  
Author(s):  
Gary Gamme ◽  
Jerry T. Dang ◽  
Noah Switzer ◽  
Richdeep Gill ◽  
Daniel W. Birch ◽  
...  
Keyword(s):  
Bariatric Surgery ◽  
Weight Loss ◽  
North American ◽  
Class I ◽  
Class I Obesity ◽  
North American Data

Striding-Athabasca mylonite zone: implications for the Archean and Early Proterozoic tectonics of the western Canadian Shield

1995 ◽  
Vol 32 (2) ◽  
pp. 178-196 ◽  
Author(s):  
Simon Hanmer ◽  
Michael Williams ◽  
Chris Kopf
Keyword(s):  
Continental Margin ◽  
Canadian Shield ◽  
Magmatic Evolution ◽  
Tectonic Zone ◽  
Early Proterozoic ◽  
Plate Margin ◽  
Mylonite Zone ◽  
Northern Saskatchewan ◽  
Archean Crust ◽  
Rifted Margin

Study of the northern Saskatchewan–District of Mackenzie segment of the Snowbird tectonic zone suggests that fragments of relatively stiff mid-Archean crust, possibly arc related, have controlled the localization, shape, and complex kinematics of the multistage Striding–Athabasca mylonite zone during the Archean, as well as the geometry of the Early Proterozoic rifted margin of the western Churchill continent. By the late Archean, the Striding–Athabasca mylonite zone was located in the interior of the western Churchill continent, well removed from the contemporaneous plate margins. Except for the Alberta segment, the Snowbird tectonic zone was not the site of an Early Proterozoic plate margin. We suggest that the geometry of the Archean–Early Proterozoic boundary in the western Canadian Shield represents a jagged continental margin, composed of a pair of reentrants defined by rifted and transform segments. These segments were inherited from Early Proterozoic breakup and controlled by the Archean structure of the interior of the western Churchill continent. The geometry of this margin appears to have strongly influenced the Early Proterozoic tectono-magmatic evolution of the western Canadian Shield.

A Note on Synchronized Emergence in Gomphus vastus Walsh (Odonata: Gomphidae)

1963 ◽  
Vol 95 (1) ◽  
pp. 69-69 ◽  
Author(s):  
Clifford Johnson
Keyword(s):  
North American ◽  
Adult Emergence ◽  
North American Species ◽  
Ecological Classification ◽  
General Area ◽  
River Bank ◽  
Dragonfly Species

An ecological classification of dragonfly species into spring and summer types was proposed by Corbet (1954). Much of the basis for the classification rests with the pattern and period of adult emergence. Since little information of this type is known for North American species, the following observations are reported.On May 20, 1962, I spent several hours collecting Baisaeschna janata and Didymops transversa along the New River, two miles north of McCoy, Virginia. A search was made at that time for odonate exuviae. None were found. I returned to the site at 9:30 a.m. the following day. The vegetation, tree trunks, rocks and detritus along the river were clustered with exuviae, all apparently of Gomphus vastus. Several thousand individuals must have emerged from that general area of the river. As an example of the density, 230 cast skins were counted along one 20-foot stretch of the river bank. Some individuals had transformed directly on the sand banks and others at a height of seven feet.

scholarly journals Changing surface radiation and energy budgets of the Hudson Bay Complex using the North American regional reanalysis (NARR) model

2019 ◽  
Vol 5 (4) ◽  
pp. 218-239 ◽  
Author(s):  
Richard Bello ◽  
Kaz Higuchi
Keyword(s):  
North American ◽  
Surface Radiation ◽  
Energy Budgets ◽  
Hudson Bay ◽  
The North ◽  
Normal Period ◽  
Marine System ◽  
Annual Component ◽  
North American Regional Reanalysis ◽  
Regional Reanalysis

Monthly and annual component fluxes of the surface radiation and energy budgets for the two-decade period from 1997 to 2016 are compared with the climate normal period (1981–2010) for the marine system consisting of James Bay, Hudson Bay, Hudson Strait and Foxe Basin using estimates from the North American regional reanalysis model. Reflected solar radiation has declined unevenly, primarily offshore of major rivers, in polynyas and along shore leads, both during earlier melt and later freeze up. Annually, net radiation increases are driven by albedo decreases during the summer. Over 94% of the increases in ocean heat gain during the melt season are due to increases in absorbed sunlight. Large enhanced oceanic heat losses in the late fall are almost entirely consumed by intensified convective losses of both sensible and latent heat. All the seas within the Hudson Bay Complex show a reduced rate of ocean warming over the past two decades. This outcome can be partially reconciled with the observation that all water bodies are experiencing enhanced losses of energy during extended ice-free winters that exceed enhanced gains of energy during the extended ice-free summers. The implications of seasonal changes in ice cover for future climate are discussed.

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