Equatorial paleolatitude for Northeast Africa in the Late Triassic: paleomagnetic study on the Gezira and Bir-Umhebal [229–223 Ma] ring complexes, Southeastern Desert, Egypt

2018 ◽  
Vol 11 (16) ◽  
Author(s):  
Hamza Lotfy ◽  
Esmat Abd Elaal
Keyword(s):  
Late Triassic ◽  
Southeastern Desert ◽  
Paleomagnetic Study ◽  
Ring Complexes ◽  
Northeast Africa

scholarly journals Paleomagnetism and cycle stratigraphy of the Triassic Fleming Fjord and Gipsdalen Formations of East Greenland

1996 ◽  
Vol 42 ◽  
pp. 121-136
Author(s):  
D.V. Kent ◽  
L.B. Clemmensen
Keyword(s):  
Late Triassic ◽  
Eastern North America ◽  
Stability Characteristic ◽  
East Greenland ◽  
Paleomagnetic Study ◽  
The Mean ◽  
Reversed Polarity ◽  
Formation Section ◽  
Milankovitch Orbital ◽  
Newark Basin

A 210 m section of Late Triassic Fleming Fjord Formation (the Malmros Klint Member and the lowermost 80m of the overlying Carlsberg Fjord beds of the Ørsted Dal Member) in the Tait Bjerg area of the Jameson Land Basin, East Greenland, was sampled for paleomagnetic study and measured for cycle stratigraphie analysis. Paleomagnetic samples were also taken from the underlying Gipsdalen Formation in the Gipsdalen area. A high stability characteristic magnetization carried by hematite was successfully isolated in 63 sampling levels in the Fleming Fjord Formation and 9 sampling sites in the Gipsdalen Formation using progressive thermal demagnetization. The mean characteristic directions for the Herning Fjord and the Gipsdalen Formations may be be biased by sedimentary inclination error but are consistent with a northward drift of East Greenland of about 10° from the arid (ca. 25° N) to semihumid (ca. 35° N) paleoclimatic belts in the Middle to Late Triassic. Seven normal and reversed polarity intervals are clearly delineated in the Fleming Fjord Formation section. A preferred correlation of the magnetostratigraphy to a cyclostratigraphically calibrated reference polarity sequence recently derived from drill cores in the Newark Basin of eastern North America suggests that the sampled interval represents about a 3.5 m.y. interval of the late Norian. The Malmros Klint Member and the overlying Carlsberg Fjord beds have composite sedimentary cycles that vary in thickness from 25 m to about 1 m and seem to match Milankovitch orbital climatic cyclicity with periods of ~400ky, ~100ky, ~40ky, and ~20ky. The composition and thickness ratio of the cycles suggest that the measured section of the Malmros Klint Member and the Carlsberg Fjord beds represents lacustrine accumulation over about 4 m.y., a duration consistent with the magnetostratigraphic correlations.

scholarly journals Paleomagnetic reconnaissance of early Mesozoic carbonates from Williston Lake, northeastern British Columbia, Canada: evidence for late Mesozoic remagnetization

2001 ◽  
Vol 38 (8) ◽  
pp. 1157-1168 ◽  
Author(s):  
Giovanni Muttoni ◽  
Dennis V Kent ◽  
Mike Orchard
Keyword(s):  
British Columbia ◽  
North America ◽  
Late Triassic ◽  
Late Mesozoic ◽  
Early Mesozoic ◽  
Paleomagnetic Study ◽  
Normal Polarity ◽  
Geomagnetic Polarity ◽  
Geomagnetic Polarity Time Scale ◽  
Early Cenozoic

Three classic sections of Middle and Late Triassic fossiliferous limestones cropping out around Williston Lake in British Columbia, Canada, were sampled for paleomagnetic study. The objective was to test the suitability of these units for detailed magnetobiostratigraphic study with the aim of improving the reference Triassic geomagnetic polarity time scale. The Williston Lake characteristic magnetizations differ, however, from any Triassic North America cratonic reference directions. A satisfactory agreement is found instead with Cretaceous – early Cenozoic North America cratonic reference directions. The exclusive occurrence of normal polarity suggests that remagnetization likely occurred during the Cretaceous long normal superchron. Remagnetizations may have been triggered by connate brines, which moved along aquifers of porous sandstones and carbonates in the early stages of Laramide folding.

Paleomagnetism of parts of the Late Triassic diabase dike system associated with the trans-New Brunswick aeromagnetic lineament

1981 ◽  
Vol 18 (12) ◽  
pp. 1776-1787 ◽  
Author(s):  
M. K. Seguin ◽  
K. V. Rao ◽  
D. V. Venugopal ◽  
E. Gahe
Keyword(s):  
New Brunswick ◽  
Middle Jurassic ◽  
Late Jurassic ◽  
The Other ◽  
Late Triassic ◽  
General Area ◽  
Present Stage ◽  
Paleomagnetic Study ◽  
C And N ◽  
Radiometric Data

A paleomagnetic study was conducted on dike samples taken from three widely separated localities along the northeasterly trending Caraquet dike system (New Brunswick) in order to define their age relationship. This dike system is recognized on the basis of a well defined aeromagnetic lineament. Stable magnetization directions were isolated after alternating field (15–40 mT) and thermal (300–550 °C) treatments of the samples taken from the three localities: C (353°, +56°), N (353°, +50°), and T (14°, +37°). The virtual pole derived from dike T (82°E, 62°N) agrees well with previously determined Late Triassic – Early Jurassic (200–190 Ma) poles for the Appalachians. On the other hand, the other two virtual pole positions from dikes C (143°E, 78°N) and N (133°E, 74°N) fall in the general area of average paleopoles for the Middle–Late Jurassic (180–170 Ma) age. The possibility that the dike at T differs in age from that of the dikes at localities C and N by at least 20 Ma is suggested. In the absence of reliable radiometric data, it is premature at the present stage to predict a likely occurrence of "younger" magnetization in these dikes related in origin to viscous partial thermoremanence possibly associated with the rifting and opening of the Atlantic in Middle Jurassic. Further investigations on newly found diabase outcrops along the magnetic lineament are in progress.

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