Paleomagnetism of the Late Triassic, North Mountain Basalt of Nova Scotia

1968 ◽  
Vol 73 (8) ◽  
pp. 2811-2822 ◽  
Author(s):  
C. M. Carmichael ◽  
H. C. Palmer
Keyword(s):  
Nova Scotia ◽  
Late Triassic

Synsedimentary collapse of portions of the lower Blomidon Formation (Late Triassic), Fundy rift basin, Nova Scotia

1995 ◽  
Vol 32 (11) ◽  
pp. 1965-1976 ◽  
Author(s):  
Rolf V. Ackermann ◽  
Roy W. Schlische ◽  
Paul E. Olsen
Keyword(s):  
Nova Scotia ◽  
Late Triassic ◽  
Normal Faults ◽  
Rift Basin ◽  
Rift Basins ◽  
Kink Bands ◽  
Deformation Features ◽  
Terrestrial Environments ◽  
Sediment Deformation ◽  
Fluvial Sandstone

A chaotic mudstone unit within the lower Blomidon Formation (Late Triassic) has been traced for 35 km in the Mesozoic Fundy rift basin of Nova Scotia. This unit is characterized by highly disrupted bedding that is commonly cut by small (<0.5 m) domino-style synsedimentary normal faults, downward movement of material, geopetal structures, variable thickness, and an irregular, partially faulted contact with the overlying unit. The chaotic unit is locally overlain by a fluvial sandstone, which is overlain conformably by mudstone. Although the thickness of the sandstone is highly variable, the overlying mudstone unit exhibits only gentle regional dip. The sandstone unit exhibits numerous soft-sediment deformation features, including dewatering structures, convoluted bedding, kink bands, and convergent fault fans. The frequency and intensity of these features increase dramatically above low points at the base of the sandstone unit. These stratigraphic relations suggest buried interstratal karst, the subsurface dissolution of evaporites bounded by insoluble sediments. We infer that the chaotic unit was formed by subsidence and collapse resulting from the dissolution of an evaporite bed or evaporite-rich unit by groundwater, producing dewatering and synsedimentary deformation structures in the overlying sandstone unit, which infilled surface depressions resulting from collapse. In coeval Moroccan rift basins, facies similar to the Blomidon Formation are associated with halite and gypsum beds. The regional extent of the chaotic unit indicates a marked period of desiccation of a playa lake of the appropriate water chemistry. The sedimentary features described here may be useful for inferring the former existence of evaporites or evaporite-rich units in predominantly clastic terrestrial environments.

Eolian dune field of Late Triassic age, Fundy Basin, Nova Scotia

Geology ◽  
1980 ◽  
Vol 8 (11) ◽  
pp. 516 ◽  
Author(s):  
John F. Hubert ◽  
Karl A. Mertz
Keyword(s):  
Nova Scotia ◽  
Late Triassic ◽  
Dune Field ◽  
Fundy Basin

Crustal structure, seismic stratigraphy, and rift processes of the continental margin off eastern Canada: ocean bottom seismic refraction results off Nova Scotia

1981 ◽  
Vol 18 (10) ◽  
pp. 1523-1538 ◽  
Author(s):  
C. E. Keen ◽  
A. Cordsen
Keyword(s):  
Nova Scotia ◽  
Continental Margin ◽  
Seismic Refraction ◽  
Seismic Stratigraphy ◽  
Late Triassic ◽  
Ocean Bottom ◽  
Total Thickness ◽  
Eastern Canada ◽  
Continental Rise ◽  
Sonic Log

Two crustal seismic refraction profiles were obtained on the continental margin of eastern Canada. These lines were located on the upper continental rise and on the outer continental shelf off Nova Scotia. A large air gun and explosive charges provided the sound sources, and ocean bottom seismometers were used to receive the signals. The travel time data were analyzed using the tau–p extremal inversion method and ray tracing techniques. This analysis allowed velocity–depth models to be constructed that included low-velocity zones and velocity gradients, as well as abrupt velocity contrasts at layer interfaces.The results show that about 7 km of sediments lies beneath the upper continental rise, beneath which oceanic layers 2 and 3 have been identified. Layer interfaces at depths of 0.39, 1.79, and 2.80 km below the sea floor correspond to strong, regional seismic reflectors, perhaps correlative with horizons Au, A*, and β. The top of oceanic layer 2 is associated with a velocity of 5.3 km s−1 and there is no difficulty in distinguishing between basement and high-velocity sediments in this region.The crust beneath the outer shelf includes 9–16 km of sediments. A layer with compressional wave velocity of 6.3 km s−1 constitutes the main crustal layer, below which the mantle is estimated to lie at total depths of 26–30 km. Within the sediments the velocity–depth model for the upper 5 km agrees well with sonic log velocities measured in deep wells. A seismic stratigraphy for the sediments can be deduced by comparing the refraction result with sonic log velocities and with the regional stratigraphy. The total thickness of the mid-Jurassic and older sediments, not sampled in the wells, is at least 4.5 km. The total thickness of crustal rocks of pre-rift age is between 14 and 21 km, which is significantly thinner than the 35–38 km values measured beneath mainland Nova Scotia in earlier studies. Both the thin crust and the high rate of subsidence during the Early Jurassic are consistent with extention of the lithosphere during initial rifting of this margin in Late Triassic time.

scholarly journals Plate tectonic reconstructions and paleogeographic maps of the central and North Atlantic oceans 1This article is one of a series of papers published in this CJES Special Issue on the theme of Mesozoic–Cenozoic geology of the Scotian Basin. 2Earth Sciences Sector Contribution 20120172.

2012 ◽  
Vol 49 (12) ◽  
pp. 1395-1415 ◽  
Author(s):  
Jean-Claude Sibuet ◽  
Stéphane Rouzo ◽  
Shiri Srivastava
Keyword(s):  
Nova Scotia ◽  
North America ◽  
Magnetic Anomaly ◽  
Late Cretaceous ◽  
North Atlantic ◽  
West African ◽  
Late Triassic ◽  
West African Coast ◽  
African Coast ◽  
Salt Deposits

We have established a new plate kinematic model of the central and North Atlantic oceans between North America, Africa, Meseta, Iberia, Flemish Cap, and Galicia Bank from Late Triassic to Late Cretaceous to better understand the nature and timing of rifting of Nova Scotia and Morocco conjugate continental margins since Late Triassic. The maps of salt distributions at the Sinemurian–Pliensbachian limit (190 Ma; after salt deposition) and in middle Bajocian (170 Ma) show that an area of the Nova Scotia margin is devoid of allochthonous salt and that an area of similar size located oceanward of the West African Coast Magnetic Anomaly shows salt deposits, suggesting that a portion of the Nova Scotia margin with its overlying salt deposits could have been transferred onto the Moroccan side right after the formation of the conjugate East Coast Magnetic Anomaly and West African Coast Magnetic Anomaly. Seven paleogeographic maps, from Late Triassic to Late Cretaceous, are presented with structural elements and magnetic lineations. They show that the connection between the Central Atlantic and the Tethys, with an aborted rift between Iberia and North America ending in the north against the Flemish Cap – Galicia Bank dam, started to deepen at the end of the first rifting phase (190 Ma ago) after the rupture of the thinned continental crust. It is only during the Early Cretaceous, after the rupture of the Flemish Cap – Galicia Bank dam, that the deep connection around Iberia was finally established between the Central and North Atlantic, the Tethys, and the Bay of Biscay.

Geochemical discriminators and the palaeotectonic environment of the North Mountain basalts, Nova Scotia

1980 ◽  
Vol 17 (12) ◽  
pp. 1740-1745 ◽  
Author(s):  
J. M. Wark ◽  
D. B. Clarke
Keyword(s):  
Nova Scotia ◽  
Continental Crust ◽  
Early Jurassic ◽  
Late Triassic ◽  
Chemical Characteristics ◽  
Sea Floor ◽  
The North ◽  
Sea Floor Spreading

The late Triassic – early Jurassic North Mountain basalts of Nova Scotia have been analyzed for various elements believed to be useful in determining the palaeotectonic environment of eruption. The discriminant diagrams show these basalts to have within-plate affinities, with a possible indication of oceanic chemical characteristics. An oceanic environment, however, is at variance with the field relations, which show the within-plate environment to be continental; thus the oceanic chemical characteristics may suggest eruption through a continental crust that was thinning prior to the onset of active sea-floor spreading later in the Jurassic.

K–Ar isochron age and paleomagnetism of diabase along the trans-Avalon aeromagnetic lineament—evidence of Late Triassic rifting in Newfoundland

1980 ◽  
Vol 17 (4) ◽  
pp. 491-499 ◽  
Author(s):  
J. P. Hodych ◽  
A. Hayatsu
Keyword(s):  
Nova Scotia ◽  
Early Jurassic ◽  
Late Triassic ◽  
The North ◽  
Two Samples ◽  
Avalon Peninsula

A prominent aeromagnetic lineament crosses the Avalon Peninsula of Newfoundland from 46°50.4′N, 53°45.9′W to 47°22.1′N, 52°30.0′W. It is shown to be at least partly caused by diabase dikes of Late Triassic and possibly Early Jurassic age which are probably related to the Shelburne diabase dike and the North Mountain basalt, both of Nova Scotia. All are thought to have resulted from rifting which preceded opening of the Atlantic.Unmetamorphosed diabase was found at three sites along the trans-Avalon aeromagnetic lineament: as narrow sills at site 1 (46°58.0′N, 53°25.4′W), as a narrow dike at site 2 (47°4.7′N, 53°7.6′W), and as large angular boulders at site 3 (47°11.0′N, 52°52.2′W).For sites 1 and 2, analyses of seven diabase samples fall on a single K–Ar isochron whose intercept on the 40Ar/36Ar axis is at 215 ± 45 and whose slope gives a Late Triassic age of 201.1 ± 2.6 Ma. Analyses of two diabase samples from the Shelburne dike fall close to this isochron suggesting a similar age. Paleomagnetism adds support; the virtual paleopole measured for sites 1 and 2, using 12 oriented diabase samples demagnetized in 300 Oe (23 880 A/m) alternating field (AF), falls at 87.8°E, 72.9°N (dp = 3.0°, dm = 4.3°), close to the virtual paleopole reported for the Shelburne dike.For site 3, analyses of two samples fall on the K–Ar isochron reported for the North Mountain basalt, tentatively suggesting that the intrusion at site 3 occurred about 10 Ma later than at sites 1and 2.

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