scholarly journals Stratigraphy, depositional environment, and tectonic setting of the Upper Triassic to Middle Jurassic rocks of the Chilcotin Ranges, southwestern British Columbia

1998 ◽  
Author(s):  
P J Umhoefer ◽  
H W Tipper
Keyword(s):  
British Columbia ◽  
Middle Jurassic ◽  
Depositional Environment ◽  
Tectonic Setting ◽  
Upper Triassic ◽  
Jurassic Rocks

Stratigraphy and tectonic setting of the upper part of the Cadwallader terrane, southwestern British Columbia

1990 ◽  
Vol 27 (5) ◽  
pp. 702-711 ◽  
Author(s):  
Paul J. Umhoefer
Keyword(s):  
British Columbia ◽  
Middle Jurassic ◽  
Tectonic Setting ◽  
Source Region ◽  
Upper Triassic ◽  
Magmatic Arc ◽  
Clastic Rocks ◽  
Coast Plutonic Complex ◽  
A Minor ◽  
Depositional Setting

The Upper Triassic to Middle Jurassic Cadwallader terrane lies on the northeastern edge of the Coast Plutonic Complex in southwestern British Columbia. Previous work on the Cadwallader Group, the basal unit of the terrane, suggested it was an Upper Triassic (Carnian to middle Norian) volcanic arc and related clastic rocks. Volcanism ceased in early Norian time. A detailed study of the upper part of the Cadwallader terrane (Tyaughton Group and overlying Last Creek formation) shows that it is a sedimentary sequence deposited on the fringe of the inactive Cadwallader magmatic arc. The Upper Triassic (middle to upper Norian) Tyaughton Group consists of nonmarine to shallow-marine clastic rocks and limestones that show sudden changes in depositional setting. The Lower to Middle Jurassic Last Creek formation, a transgressive sequence of clastic rocks, disconformably overlies the Tyaughton Group. The clastic rocks in the two units were derived from a mixed volcanic and plutonic source region that also included a minor metamorphic component and local lower Norian limestones. The stratigraphy of the upper part of the Cadwallader terrane records long-term thermal subsidence of the basin caused by cooling of the magmatic arc after volcanism ceased in the early Norian. The detailed stratigraphy of the upper Cadwallader terrane supports correlation of the Cadwallader with the Stikine terrane, along which it is currently structurally juxtaposed.

Geology of the Cadwallader Group and the Intermontane–Insular superterrane boundary, southwestern British Columbia

1987 ◽  
Vol 24 (11) ◽  
pp. 2279-2291 ◽  
Author(s):  
Margaret E. Rusmore
Keyword(s):  
British Columbia ◽  
Middle Jurassic ◽  
Tectonic Evolution ◽  
Middle Triassic ◽  
Upper Triassic ◽  
Tectonic Block ◽  
Volcanic Arc ◽  
Arc Volcanism ◽  
Clastic Rocks ◽  
Tectonic Settings

Several lower Mesozoic, fault-bounded units separate the Intermontane and Insular superterranes in southwestern British Columbia. Detailed study of one of these Mesozoic units, the Cadwallader Group, helps clarify the boundary between the superterranes and establish the tectonic evolution of southwestern British Columbia. The Cadwallader Group is the oldest unit in an Upper Triassic through Middle Jurassic volcanic and sedimentary tectono-stratigraphic terrane. Two formations, the Pioneer and the Hurley, compose the Cadwallader Group; the previously recognized Noel Formation is no longer considered valid. The Pioneer Formation contains pillow basalt, flows, and basalt breccia. Siltstone, sandstone, conglomerate, and minor amounts of limestone megabreccia and basalt belonging to the Hurley Formation conformably overlie the Pioneer. The Hurley spans latest Carnian or earliest Norian to middle Norian time. Two episodes of deformation affected the Cadwallader, and a thrust fault separates the group from slightly younger clastic rocks of the Tyaughton Group. Similarities in clastic rocks indicate the Tyaughton was deposited on the Cadwallader; together the units form the Cadwallader terrane. Basalts and clastic rocks in the terrane record deposition in or near a Carnian to earliest Norian volcanic arc. Volcanism waned later in the Norian, but presence of the arc is preserved in the clastic rocks.Oceanic rocks of the Middle Triassic to Middle Jurassic Bridge River terrane became juxtaposed with the Cadwallader terrane in Middle Jurassic time, after which the terranes functioned as a single tectonic block. Contrasting volcanic histories suggest that the Cadwallader terrane was not accreted to the Intermontane superterrane until Middle Jurassic or Early Cretaceous time, although the similar tectonic settings of Stikinia and the Cadwallader terrane allow a common earlier history. The Cadwallader terrane is not part of either the Alexander terrane or Wrangellia, and so the inboard margin of the Insular superterrane must lie west of the Cadwallader terrane.

Revised stratigraphy of the Takla Group, north-central British Columbia

1977 ◽  
Vol 14 (2) ◽  
pp. 318-326 ◽  
Author(s):  
J. W. H. Monger ◽  
B. N. Church
Keyword(s):  
British Columbia ◽  
Sedimentary Rocks ◽  
Lower Jurassic ◽  
Upper Triassic ◽  
Late Triassic ◽  
North Central ◽  
Volcaniclastic Rocks ◽  
Jurassic Rocks

The Takla Group of north-central British Columbia as originally defined contained volcanic and sedimentary rocks of Late Triassic and Jurassic ages. As redefined herein, it consists of three formations in the McConnell Creek map-area. Lowest is the Dewar Formation, composed of argillite and volcanic sandstone that is largely the distal equivalent of basic flows and coarse volcaniclastic rocks of the Savage Mountain Formation. These formations are overlain by the volcaniclastic, basic to intermediate Moosevale Formation. These rocks are Upper Triassic (upper Karnian and lower Norian). They are unconformably overlain by Lower Jurassic rocks of the Hazelton Group.

scholarly journals Dachstein-type Avroman Formation: An indicator of the Harsin Basin in Iraq

GeoArabia ◽  
2015 ◽  
Vol 20 (4) ◽  
pp. 17-36
Author(s):  
Agoston Sasvari ◽  
Laura Davies ◽  
Andrew Mann ◽  
Jawad Afzal ◽  
Gabor Vakarcs ◽  
...  
Keyword(s):  
Depositional Environment ◽  
Carbonate Platform ◽  
Tectonic Setting ◽  
Upper Triassic ◽  
Northern Calcareous Alps ◽  
Late Triassic ◽  
Northern Calcareous ◽  
Marine Sedimentation ◽  
Tectonic Position ◽  
Arabian Platform

ABSTRACT A field survey was carried out in 2012 focusing on the tectonic position and the role of Upper Triassic (Upper Norian–Rhaetian) Avroman Formation outcrops located in the Zalm area of Iraq, close to the Iraq-Iran border. At this location, the Cretaceous chert-bearing strata of the Qulqula Formation are overlain by sheared mafic bodies, which are in turn topped by the cliffs of the megalodontaceae-bearing Upper Triassic Avroman Formation. Similarities in lithology, sequence and tectonics position, suggest that the Triassic section of the Bisotoun Unit from the Kermanshah Zone of Iran can be used as a tectonic analogue of the Avroman Formation. According to our model, both the Avroman and the Bisotoun units formed an intra-oceanic carbonate platform, built-up by a characteristic megalodontaceae-bearing carbonate platform assemblage during the Late Triassic. The Harsin oceanic basin, which separated the Avroman-Bisotoun Platform from the Arabian Platform, was characterised by deep-marine sedimentation, the remnants of which form the Qulqula Formation in Iraq, and the Radiolaritic Nappe and the Harsin Mélange in the Kermanshah Zone. This tectonic setting is not unique; numerous authors suggest the existence of an oceanic rim basin, separating carbonate platform units (e.g. Oman ‘exotics’) from the Arabian Platform. The age of the deformation could be Late Cretaceous (Maastrichtian), but using analogues from Iran, a Palaeogene deformation also seems possible. The Avroman Formation was interpreted to be a Dachstein-type sediment, similar to the well-studied Dachstein Formation of the Northern Calcareous Alps, Austria. Rock units, with similar lithology, or identical depositional environment and macroscopic fauna, were described by numerous authors along the Neo-Tethys suture zone from Austria to Japan, and from several tectonic units along the Panthalassa margin. The implication of this correlation is important for future studies: using well-described type localities of the marine units from the Northern Calcareous Alps as a reference, it is possible to significantly extend the available background knowledge, and to gain better insight into the Triassic regional depositional environment of the Middle East.

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