Paleopoles and paleolatitudes of North America and speculations about displaced terrains

1979 ◽  
Vol 16 (3) ◽  
pp. 669-694 ◽  
Author(s):  
E. Irving
Keyword(s):  
North America ◽  
Plate Tectonics ◽  
Early Carboniferous ◽  
Coast Range ◽  
Present Position ◽  
Polar Wander ◽  
The Past ◽  
Western Cordillera ◽  
Middle Paleozoic ◽  
Single Path

A statistically determined path of apparent polar wander for the past 300 Ma for North America is given. It has a zigzag form, the bends corresponding to important changes in the drift of North America. Many Mesozoic and Early Tertiary paleopoles from the Western Cordillera do not conform to this path, and they are best explained by motions of miniblocks within the Cordillera. Especially notable is the displacement of Vancouver Island and associated Alaskan terrains (Wrangellia) in the early Mesozoic, and the clockwise rotation of the Coast Range of Oregon and Washington (Siletzia) in the Cenozoic. Limited evidence indicates that part at least of the Northern Appalachian region could have been about 10° south of its present position relative to North America in Late Devonian and Early Carboniferous times, and that it achieved its present position by Late Carboniferous time. Displaced terrains of early and middle Paleozoic age may also be present in the Appalachians. Displacements in the Appalachians and Cordillera could have been caused by the exchange of fragments of continental crust across transcurrent plate junctures. Apparent polar wandering paths for the Precambrian are tentative, but a fairly simple single path can be constructed for all structural provinces of the Laurentian Shield. This reconstruction of a single Precambrian path is supported by agreement among approximately contemporaneous paleopoles from widespread localities. It implies that movements amongst the structural provinces of the shield during the Hudsonian and Grenvillian Orogenies have been modest, and perhaps not in excess of about 1000 km in a latitude sense. This idea has been disputed by those who would apply conventional ideas of plate-tectonics to the Proterozoic, but it has the merit of explaining all the paleopoles and their geological relationships in a comparatively simple unified scheme. Rates of latitude change in the Precambrian may have been over twice as great as in the Phanerozoic.

Palaeomagnetic evidence bearing on the evolution of the Canadian Cordillera

1990 ◽  
Vol 331 (1620) ◽  
pp. 487-509 ◽  
Keyword(s):  
North America ◽  
Canadian Cordillera ◽  
Present Position ◽  
The South ◽  
The West ◽  
Western Cordillera ◽  
Palaeomagnetic Data ◽  
Comparable Magnitude ◽  
Bedded Rocks

Palaeomagnetic data from Permian, Triassic and Jurassic bedded rocks, to which attitudinal corrections can be applied, yield palaeolatitudes concordant with those of ancestral North America, but very large predominantly anticlockwise rotations about vertical axes. Data from Cretaceous rocks yield apparent palaeolatitudinal displacements that increase westward. Small or negligible displacements are obtained from the Omineca Belt. Intermediate displacements (1000-2000 km) from the Intermontane Belt, are based on data from Cretaceous bedded sequences. Further to the west in the Coast Belt, larger apparent displacements (greater than 2000 km) have been obtained from plutons for which no attitudinal control is yet available. Data from Eocene rocks are concordant. Possibilities to consider are as follows: (a) little or no displacement and tilting to the southwest at about 30°; (b) large (greater than 2000 km in the Coast Belt) northward displacement since mid-Cretaceous time preceded by southward displacement of comparable magnitude in Juro-Cretaceous time; (c) lesser (1000-2000 km) overall displacement coupled with variable and lesser tilts to the south and southeast of plutons of the Coast Belt. Under hypothesis (a) the western Cordillera was formed and has remained in approximately its present position relative to ancestral North America; data from bedded volcanics of the Intermontane Belt are not consistent with this hypothesis. From the evidence currently available we favour hypotheses (b) or (c), although more data from bedded sequences are required. It is noteworthy that hypotheses (a) and (c) predict tilt directions that differ by about 90° and hence ought to be distinguishable by geological studies.

scholarly journals A Late Cretaceous true polar wander oscillation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ross N. Mitchell ◽  
Christopher J. Thissen ◽  
David A. D. Evans ◽  
Sarah P. Slotznick ◽  
Rodolfo Coccioni ◽  
...  
Keyword(s):  
High Resolution ◽  
Late Cretaceous ◽  
Plate Tectonics ◽  
Large Scale ◽  
Spin Axis ◽  
Polar Wander ◽  
The Past ◽  
True Polar Wander ◽  
Palaeomagnetic Data

AbstractTrue polar wander (TPW), or planetary reorientation, is well documented for other planets and moons and for Earth at present day with satellites, but testing its prevalence in Earth’s past is complicated by simultaneous motions due to plate tectonics. Debate has surrounded the existence of Late Cretaceous TPW ca. 84 million years ago (Ma). Classic palaeomagnetic data from the Scaglia Rossa limestone of Italy are the primary argument against the existence of ca. 84 Ma TPW. Here we present a new high-resolution palaeomagnetic record from two overlapping stratigraphic sections in Italy that provides evidence for a ~12° TPW oscillation from 86 to 78 Ma. This observation represents the most recent large-scale TPW documented and challenges the notion that the spin axis has been largely stable over the past 100 million years.

scholarly journals Remnant and the New Dark Age

Religions ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 372
Author(s):  
Edward Rommen
Keyword(s):  
North America ◽  
Moral Discourse ◽  
The Past ◽  
Personal Opinion

A new dark age has come upon us; as a result, Christianity and its churches in North America are no longer growing. One reason for this might be the widespread impression that Christians are hypocrites, saying they believe one thing while doing the opposite. However, that accusation would only be true if these believers actually believed the principles they are supposed to be violating. It is more likely that many Christians have, like those around them, abandoned truth in favor of personal opinion bringing moral discourse to a near standstill and intensifying the darkness by extinguishing the light of truth. Still, there is hope. In the past, it often was a faithful few, a remnant, who preserved the knowledge of that light and facilitated a new dawn. History shows us that the very movements that are today abdicating responsibility were once spiritual survivors themselves. They withdrew, coalesced around the remaining spark of truth in order to remember, preserve, and reignite. The thoughts and practices of these pioneers could guide the escape from today’s darkness.

scholarly journals Scoot over Smart Devices: The Invisible Costs of Rental Scooters

2019 ◽  
Vol 17 (1/2) ◽  
pp. 191-197 ◽  
Author(s):  
Andrew Boyles Petersen
Keyword(s):  
North America ◽  
Data Security ◽  
Mobile Apps ◽  
Smart Devices ◽  
Gps Data ◽  
Security Risks ◽  
The Past ◽  
Last Mile ◽  
User Data ◽  
Consumer Data

In the past year, transportation rental companies, including Bird, Lime, and Spin, have dropped hundreds of thousands of rental scooters across North America. Relying on mobile apps and scooter-mounted GPS units, these devices have access to a wide-variety of consumer data, including location, phone number, phone metadata, and more. Pairing corroborated phone and scooter GPS data with a last-mile transportation business model, scooter companies are able to collect a unique, highly identifying dataset on users. Data collected by these companies can be utilized by internal researchers or sold to advertisers and data brokers. Access to so much consumer data, however, poses serious security risks. ­Although Bird, Lime, and Spin posit electric scooters as environmentally friendly and accessible transportation, they also allow for unethical uses of user data through vaguely-worded terms of service. To promote more equitable transportation practices, this article will explore the implications of dockless scooter geotracking, as well as related infrastructure, privacy, and data security ramifications.

Implications for the age of South African Devonian rocks in which Tropidoleptus (Brachiopoda) has been found

1983 ◽  
Vol 120 (1) ◽  
pp. 51-58 ◽  
Author(s):  
A. J. Boucot ◽  
C. H. C. Brunton ◽  
J. N. Theron
Keyword(s):  
South Africa ◽  
North America ◽  
South African ◽  
Early Carboniferous ◽  
Fossil Plants ◽  
Geological Time ◽  
Marine Sedimentation ◽  
History Of ◽  
Near Shore ◽  
First Time

SummaryThe Devonian brachiopod Tropidoleptus is recognized for the first time in South Africa. It is present in the lower part of the Witteberg Group at four widely separated localities. Data regarding the stratigraphical range of the genus elsewhere, combined with information on recently described fossil plants and vertebrates from underlying strata of the upper Bokkeveld Group, suggest that a Frasnian or even Givetian age is reasonable for the lower part of the Witteberg Group. The recognition of Tropidoleptus in a shallow water, near-shore, molluscan association, at the top of the South African marine Devonian sequence, is similar to its occurrence in Bolivia, and suggests a common Malvinokaffric Realm history of shallowing, prior to later Devonian or early Carboniferous non-marine sedimentation. It is noteworthy that Tropidoleptus is now known to occur in ecologically suitable environments around the Atlantic, but is absent from these same environments in Asia and Australia. Tropidoleptus is an excellent example of dispersal in geological time — first appearing in northern Europe and Nova Scotia, then elsewhere in eastern North America and North Africa, followed by South America and South Africa, while continuing in North America.

Summary of Coastal Geologic Evidence for past Great Earthquakes at the Cascadia Subduction Zone

1995 ◽  
Vol 11 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Brian F. Atwater ◽  
Alan R. Nelson ◽  
John J. Clague ◽  
Gary A. Carver ◽  
David K. Yamaguchi ◽  
...  
Keyword(s):  
British Columbia ◽  
North America ◽  
Subduction Zone ◽  
Forest Soils ◽  
Pacific Coast ◽  
Cascadia Subduction Zone ◽  
Level Change ◽  
The Past ◽  
The Pacific ◽  
Juan De Fuca

Earthquakes in the past few thousand years have left signs of land-level change, tsunamis, and shaking along the Pacific coast at the Cascadia subduction zone. Sudden lowering of land accounts for many of the buried marsh and forest soils at estuaries between southern British Columbia and northern California. Sand layers on some of these soils imply that tsunamis were triggered by some of the events that lowered the land. Liquefaction features show that inland shaking accompanied sudden coastal subsidence at the Washington-Oregon border about 300 years ago. The combined evidence for subsidence, tsunamis, and shaking shows that earthquakes of magnitude 8 or larger have occurred on the boundary between the overriding North America plate and the downgoing Juan de Fuca and Gorda plates. Intervals between the earthquakes are poorly known because of uncertainties about the number and ages of the earthquakes. Current estimates for individual intervals at specific coastal sites range from a few centuries to about one thousand years.

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