Paleomagnetism and correlation of some Middle Keweenawan rocks, Lake Superior

1970 ◽  
Vol 7 (6) ◽  
pp. 1410-1436 ◽  
Author(s):  
H. C. Palmer
Keyword(s):  
Lake Superior ◽  
Pole Position ◽  
Magnetic Polarity ◽  
Secondary Component ◽  
Equal Weight ◽  
Reverse Polarity ◽  
North Shore ◽  
The North ◽  
Normal Polarity ◽  
The Mean

Paleomagnetic results from the Lake Superior region appear to indicate that Middle Keweenawan formations or magnetic divisions within formations can be correlated on the basis of magnetic polarity. The Logan sills, the volcanics of the Osler Group, the lava section at Alona Bay, the lower 6000 ft (1829 m) of North Shore volcanics, the lower 1000 ft (305 m) of Cape Gargantua volcanics and the lower 3000 ft (914 m) at Mamainse Point are of reverse polarity. Normal directions of magnetization, which differ from the reverse directions of magnetization by amounts ranging from 140° to 163° occur throughout the Michipicoten Island section, and in the upper parts of the North Shore, Cape Gargantua, and Mamainse Point sections. Provided part of the section at Mamainse Point has been repeated by faulting, these new results, together with data from the literature, are compatible with a single polarity reversal in Middle Keweenawan time separating older reverse polarity rocks from stratigraphically younger normal polarity rocks. The mean direction of magnetization from a conglomerate test is defined with higher precision than would be expected from a randomly distributed population. It is believed that this mean direction reflects a secondary component of magnetization which cannot be preferentially removed by alternating field demagnetization and which has caused the non anti-parallel alignment of normal and reverse populations of magnetization. An estimate of the pole position during Middle Keweenawan time can, however, be made by calculating a pole given equal weight to the mean normal and mean reverse pole. This is calculated to be 159° W, 42° N.

Water in the Wilderness: The Group of Seven and the Coastal Identity of Lake Superior

2021 ◽  
pp. e20200049
Author(s):  
Isabelle Gapp
Keyword(s):  
Environmental History ◽  
Lake Superior ◽  
Indigenous Communities ◽  
Coastal Lake ◽  
Group Of Seven ◽  
North Shore ◽  
The North ◽  
The People ◽  
Coastal Landscapes ◽  
History Of

This paper challenges the wilderness ideology with which the Group of Seven’s coastal landscapes of the north shore of Lake Superior are often associated. Focusing my analysis around key works by Lawren Harris, A.Y. Jackson, J.E.H. MacDonald, and Franklin Carmichael, I offer an alternative perspective on commonly-adopted national and wilderness narratives, and instead consider these works in line with an emergent ecocritical consciousness. While a conversation about wilderness in relation to the Group of Seven often ignores the colonial history and Indigenous communities that previously inhabited coastal Lake Superior, this paper identifies these within a discussion of the environmental history of the region. That the environment of the north shore of Lake Superior was a primordial space waiting to be discovered and conquered only seeks to ratify the landscape as a colonial space. Instead, by engaging with the ecological complexities and environmental aesthetics of Lake Superior and its surrounding shoreline, I challenge this colonial and ideological construct of the wilderness, accounting for the prevailing fur trade, fishing, and lumber industries that dominated during the nineteenth and early twentieth centuries. A discussion of environmental history and landscape painting further allows for a consideration of both the exploitation and preservation of nature over the course of the twentieth century, and looks beyond the theosophical and mystical in relation to the Group’s Lake Superior works. As such, the timeliness of an ecocritical perspective on the Group of Seven’s landscapes represents an opportunity to consider how we might recontextualize these paintings in a time of unprecedented anthropogenic climate change, while recognizing the people and history to whom this land traditionally belongs.

Habitat restoration in the North Shore of Lake Superior:

2021 ◽  
pp. 183-208
Author(s):  
R. Stewart ◽  
J. Bailey
Keyword(s):  
Habitat Restoration ◽  
Lake Superior ◽  
North Shore ◽  
The North

scholarly journals Climate change and angling behavior on the North shore of Lake Superior (USA)

2020 ◽  
Vol 231 ◽  
pp. 105717
Author(s):  
Adam Hestetune ◽  
Paul M. Jakus ◽  
Christopher Monz ◽  
Jordan W. Smith
Keyword(s):  
Climate Change ◽  
Lake Superior ◽  
North Shore ◽  
The North

New 42 Ma cratonic North American paleomagnetic pole from the Yukon underscores another Cordilleran paleomagnetism-geology conundrum

2003 ◽  
Vol 40 (10) ◽  
pp. 1321-1334 ◽  
Author(s):  
David TA Symons ◽  
Philippe Erdmer ◽  
Phil JA McCausland
Keyword(s):  
North American ◽  
Magnetic Polarity ◽  
Eastern Coast ◽  
The North ◽  
Normal Polarity ◽  
Reversed Polarity ◽  
North American Craton ◽  
Host Rocks ◽  
Pacific Plate Subduction ◽  
Plate Subduction

Eocene posttectonic plutons of the Beaver River alkalic complex in southeastern Yukon intruded Devonian–Mississippian and Triassic sandstones in the Foothills of the Canadian Cordillera. A paleomagnetic collection of 27 sites from three separate plutons produced 326 specimens that were analyzed using alternating field and thermal step demagnetization methods. The A component characteristic remanent magnetization (ChRM) resides in magnetite with normal polarity in the 42.6 ± 0.8 Ma Beaver River pluton, reversed polarity in the 42.1 ± 0.7 Ma Larson Creek East pluton, and both polarities in the 41.3 ± 0.4 Ma Larson Creek West pluton, corresponding with magnetic polarity chrons 20n, 19r, and the boundary between chron 19r and 18n, respectively. The ChRMs of the plutons are indistinguishable (2σ) with a mean for the 42.0 ± 0.5 Ma complex of D = 158.8°, I = –73.1° (N = 21 sites, α95 = 3.0°, k = 116.8). A positive paleomagnetic contact test shows the A component to be primary, and the poorly isolated B component suggests the host rocks for Larson Creek West are Early to Middle Devonian. The paleopole for the Beaver River complex at 79.2°N, 145.8°E (N = 21, dp = 4.8°, dm = 5.4°; Q = 7) is concordant with interpolated 42 Ma reference poles for the North American craton. In contrast, paleopoles from the accreted Intermontane and eastern Coast Belt terranes record clockwise rotations of 24° ± 10° (Eocene) and 13° ± 5° (Oligocene–Pliocene), indicating that the allochthonous Intermontane terranes have been progressively driven ~240 ± 120 km eastwards up and over pericratonic and cratonic North American lower crust by Pacific plate subduction since the mid-Eocene.

Rb–Sr geochronology of the Coldwell Complex, northwestern Ontario, Canada

1982 ◽  
Vol 19 (9) ◽  
pp. 1796-1801 ◽  
Author(s):  
R. Garth Platt ◽  
Roger H. Mitchell
Keyword(s):  
Upper Mantle ◽  
Lake Superior ◽  
Parental Magma ◽  
Initial Ratio ◽  
North Shore ◽  
The North ◽  
Northwestern Ontario ◽  
Alkaline Intrusion ◽  
Intrusive Rocks ◽  
Igneous Activity

The Coldwell Complex of Northwestern Ontario is North America's largest structurally and petrologically complex alkaline intrusion. Situated on the north shore of Lake Superior, it consists of at least three intrusive centres and is cross-cut by a diverse suite of coeval–cogenetic dikes. The main intrusive rocks range from gabbros to ferroaugite syenites, nepheline syenites, and quartz syenites. The dikes are predominantly lamprophyric. A seventeen point whole rock Rb–Sr isochron (MSWD 2.22) gives an age of 1044.5 ± 6.2 Ma (2σ) and an initial ratio of 0.70354 ± 0.00016 (2σ). The age is late Neohelikian and is younger than the bulk of igneous activity (Keweenawan activity) prevalent in the Lake Superior Basin during the Neohelikian. The low initial ratio indicates an upper mantle origin for the parental magma of the complex.

HURONIAN STRATIGRAPHY OF THE McGREGOR BAY AREA, ONTARIO: RELEVANCE TO THE PALEOGEOGRAPHY OF THE LAKE SUPERIOR REGION

1966 ◽  
Vol 3 (2) ◽  
pp. 203-210 ◽  
Author(s):  
Grant M. Young
Keyword(s):  
United States ◽  
Lake Superior ◽  
Lake Huron ◽  
North Central ◽  
North Shore ◽  
Bay Area ◽  
The North ◽  
Central United States ◽  
Iron Formations

Mapping in the McGregor Bay area of Ontario has shown the presence of a sequence of formations which closely resembles that of the original Huronian of the Bruce Mines–Blind River area. Iron-rich siltstones and argillites above the Lorrain formation are correlated with the lower part of the Animikie iron-formations of the Port Arthur region of Lake Superior and the north central United States. The oldest Proterozoic rocks of the region south of Lake Superior are considered to be correlatives of the Cobalt group of the north shore of Lake Huron.

scholarly journals XI. Researches on the tides.—tenth series. on the laws of low water at the port of plymouth, and on the permanency of mean water

1839 ◽  
Vol 129 ◽  
pp. 151-161 ◽  
Keyword(s):  
High Water ◽  
Level Line ◽  
English Channel ◽  
Know How ◽  
North Shore ◽  
The North ◽  
South Shore ◽  
The Subject ◽  
The Mean ◽  
The Difference

In former communications to the Society, the laws of high water at Plymouth and other places have been the subject of my researches. These being obtained, the laws of low water are a subject of importance and interest on many accounts. The first ground of my pursuing this subject was the desire to ascertain how far the mean water , that is, the height midway between high and low water, is permanent during the changes which high and low water undergo. That it is approximately so at Ply­mouth, had been ascertained both by Mr. Walker and myself, by means of a com­parison of a short series of observations. But it was desirable to know with more exactness what was the real amount of this permanency, when, by using a long series of observations of high and low water, the irregularities arising from accident, and from taking imperfect cycles of inequalities, were eliminated. There was another reason which made this inquiry important at the present time. An operation has been recently carried on by the direction and at the expense of the British Association, with a view of ascertaining what surface ought to be taken as the permanent level of the sea. A Level Line has been carried with great care and accuracy from the north shore of Somerset to the south shore of Devon ; and the po­sition of this line has been fixed, so as to be recognised at any future time, by means of marks at Axmouth, at East Quantockshead, at Stolford, and at Portishead. This line has also been referred to the sea at its extremities ; and the observations show that the height of mean water coincides, at least very nearly, at different places, as well as at the same place at different times. While the difference of levels of low water at Axmouth on the English Channel, and Wick Rocks on the Bristol Channel, is not less than twelve feet; the mean water at those two places coincides in level within a few inches. In order to determine further what accuracy may be attained in this result, we are led to inquire what is the degree of permanency at one place. I may further add, that it cannot but be instructive to know how far the corrections of the height and time of low water, for lunar parallax and declination, agree in form and amount with the same corrections already obtained for high water.

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