A cratonic Middle Jurassic paleopole: Callovian-Oxfordian stillstand (J-2 cusp), rotation of the Colorado Plateau, and Jurassic North American apparent polar wander

Tectonics ◽  
2003 ◽  
Vol 22 (3) ◽  
pp. n/a-n/a ◽  
Author(s):  
Maureen B. Steiner
Keyword(s):  
North American ◽  
Middle Jurassic ◽  
Colorado Plateau ◽  
Polar Wander

A Discussion on global tectonics in Proterozoic times - Palaeomagnetic evidence for a Proterozoic super-continent

1976 ◽  
Vol 280 (1298) ◽  
pp. 469-490 ◽  
Keyword(s):  
North American ◽  
Mantle Convection ◽  
Great Circle ◽  
Prominent Feature ◽  
Time Data ◽  
Polar Wander ◽  
Late Precambrian ◽  
Palaeomagnetic Data ◽  
The Baltic ◽  
Global Tectonics

The Precambrian apparent polar wander (a.p.w.) curve for Africa is now defined in a general way from ca . 2700 million years (Ma) to Palaeozoic times, and is compared here with palaeomagnetic results from other Precambrian regions. Loops present in the African and North American a.p.w. curves between 2000 and 1000 Ma can be matched in size and shape, and when superimposed show that the AfroArabian and North American regions were in continuity at this time. Data from other Gondwanaland continents are reviewed and seem to be consistent with the SmithHallam reconstruction to ca . 2100 Ma for South America, to ca . 1800 Ma for India, and possibly for Australia back to ca . 2100 Ma. The a.p.w. curve from the Baltic and Ukrainian Shields can be matched with that from Africa and North America such that there was crustal continuity prior to 1000 Ma with the Gothide and Grenville mobile belts in great-circle alignment. The limited palaeomagnetic data from the Siberian Shield do not allow it to be placed uniquely with respect to the other land masses but are consistent with a position in juxtaposition with the Baltic-Ukrainian Shields such that massive anorthosites and ca . 1000 Ma mobile belts are in alignment with those from elsewhere. The palaeomagnetic evidence is consistent with a model in which the bulk of the Precambrian shields were aggregated together as a single super-continent during much of Proterozoic times, the most prominent feature of which is a great circle alignment of massive anorthosites (2250-1000 Ma) along a belt which also became a concentrated zone of igneous intrusion by rapakivi granites and alkaline intrusions, and culminated in generation of long linear mobile belts at 1150 ± 200 Ma and thick graben sedimentation. The predominance of this feature during much of the Proterozoic suggests that a simple mantle convection system pertained during this time. The proposed super-continent is not greatly different in form from the later shortlived super-continent Pangaea, formation of which may have involved relatively minor redistribution of the sialic regions in late Precambrian (probably post-800 Ma) and Palaeozoic times.

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 Lawrenceton Formation volcanic rocks, Silurian Botwood Group, Change Islands, Newfoundland

1989 ◽  
Vol 26 (2) ◽  
pp. 296-304 ◽  
Author(s):  
Julie E. Gales ◽  
Ben A. van der Pluijm ◽  
Rob Van der Voo
Keyword(s):  
North American ◽  
Volcanic Rocks ◽  
Mobile Belt ◽  
Structural Mapping ◽  
Polar Wander ◽  
The North ◽  
Apparent Polar Wander Path ◽  
Paleomagnetic Study ◽  
North American Craton

Paleomagnetic sampling of the Lawrenceton Formation of the Silurian Botwood Group in northeastern Newfoundland was combined with detailed structural mapping of the area in order to determine the deformation history and make adequate structural corrections to the paleomagnetic data.Structural analysis indicates that the Lawrenceton Formation experienced at least two folding events: (i) a regional northeast–southwest-trending, Siluro-Devonian folding episode that produced a well-developed axial-plane cleavage; and (ii) an episode of local north-trending folding. Bedding – regional cleavage relationships indicate that the latter event is older than the regional folding.Thermal demagnetization of the Lawrenceton Formation yielded univectorial southerly and shallow directions (in situ). A fold test on an early mesoscale fold indicates that the magnetization of the Botwood postdates this folding event. However, our results, combined with an earlier paleomagnetic study of nearby Lawrenceton Formation rocks, demonstrate that the magnetization predates the regional folding. Therefore, we conclude that the magnetization occurred subsequent to the local folding but prior to the period of regional folding.While a tectonic origin for local folding cannot be entirely excluded, the subaerial nature of these volcanics, the isolated occurrence of these folds, and the absence of similar north-trending folds in other areas of eastern Notre Dame Bay suggest a syndepositional origin. Consequently, the magnetization may be nearly primary. Our study yields a characteristic direction of D = 175°, I = +43°, with a paleopole (16°N, 131 °E) that plots near the mid-Silurian track of the North American apparent polar wander path. This result is consistent with an early origin for the magnetization and supports the notion that the Central Mobile Belt of Newfoundland was adjacent to the North American craton, in its present-day position, since the Silurian.

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.

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