Stratigraphic revisions of the Nicola, Cache Creek, and Mount Ida Groups, based on conodont collections from the western margin of the Shuswap Metamorphic Complex, south-central British Columbia

1976 ◽  
Vol 13 (1) ◽  
pp. 44-53 ◽  
Author(s):  
A. V. Okulitch ◽  
B. E. B. Cameron
Keyword(s):  
British Columbia ◽  
Upper Triassic ◽  
Late Triassic ◽  
Metamorphic Complex ◽  
Western Margin ◽  
South Central ◽  
Western Border ◽  
Shuswap Metamorphic Complex

Conodonts have been recovered from highly deformed limestone and calcareous argillite in Palaeozoic and Mesozoic successions near the western border of the Shuswap Metamorphic Complex. Presently known biostratigraphic sequences indicate that the Eagle Bay Formation of the Mount Ida Group is in part Mississippian in age, and likely correlative with the Slide Mountain and Milford Groups. In addition, part of the succession previously mapped as Cache Creek Group in the Vernon area is now known to be Late Triassic in age, and can be correlated with the Sicamous Formation of the Mount Ida Group, the Nicola Group, and the Slocan Group. The Upper Triassic succession was affected by deformation and metamorphism associated with development of the Shuswap Metamorphic Complex.

Devonian Plutonism in South-Central British Columbia

1975 ◽  
Vol 12 (10) ◽  
pp. 1760-1769 ◽  
Author(s):  
Andrew V. Okulitch ◽  
R. K. Wanless ◽  
W. D. Loveridge
Keyword(s):  
British Columbia ◽  
Middle Devonian ◽  
Metamorphic Complex ◽  
Western Margin ◽  
South Central ◽  
Minimum Age ◽  
History Of ◽  
Shuswap Metamorphic Complex

An apparently tabular body of granitoid gneiss, 3 to 5 km wide and more than 70 km long, that lies along the western margin of the Shuswap Metamorphic Complex between Shuswap and Admas Lakes, shows intrusive relationships with Palaeozoic and older rocks and has yielded zircons whose minimum age is 372 Ma. This intrusion, together with other granitoid plutons in the area that appear to be related to it, provide evidence of widespread plutonism during Middle Devonian time near the western edge of the Paleozoic Cordillera geosyncline and necessitate significant revisions in the interpretation of the crustal history of this region.

The Triassic unconformity of south-central British Columbia

1977 ◽  
Vol 14 (4) ◽  
pp. 606-638 ◽  
Author(s):  
P. B. Read ◽  
Andrew V. Okulitch
Keyword(s):  
British Columbia ◽  
Regional Metamorphism ◽  
Tholeiitic Basalt ◽  
Upper Triassic ◽  
Late Triassic ◽  
Low Grade ◽  
Early Triassic ◽  
Central Belt ◽  
South Central ◽  
Shuswap Metamorphic Complex

At five localities investigated in south-central British Columbia, Upper Triassic rocks are observed or inferred to unconformably overlie upper Paleozoic and older rocks. Paleozoic rocks beneath the unconformity show polyphase deformation and low-grade regional metamorphism which are absent in overlying rocks. Data from these and other localities define a regional angular unconformity of Late Permian or Early Triassic age on the western and southern margins of the Shuswap Metamorphic Complex. Permian and Triassic rocks preserve evidence of structural, sedimentary, and metamorphic events which permits separation of Triassic rocks into three fault-bounded tectonostratigraphic belts. The Eastern Belt contains the transition from miogeoclinal sedimentation throughout Triassic time in the Canadian Rockies to island arc volcanism in the Late Triassic to the west. Basal beds of the Triassic sequence become younger southwest-ward from the axis of the Early to Middle Triassic depocentre lying west of the Rockies. Rocks preserving Early Triassic deformation and metamorphism are restricted to the southwest corner of the belt and are truncated by the Pasayten Fault. The Central Belt, dominated by the products of Late Triassic volcanism in northern and central British Columbia, consists mainly of Middle (?) and Upper Triassic sediments in the south. Meagre evidence indicates that widespread deformation and low-grade regional metamorphism occurred just prior to the Late Triassic. Evidence for these events is not found beyond the faulted margins of the Central Belt. In the Western Belt, an Upper Triassic sequence of tholeiitic basalt and overlying calcareous sediments disconformably overlies Permian rocks. In the western Cordillera, low-grade regional metamorphism and minor plutonism characterize Triassic orogenies. Early Triassic orogenesis in the southwestern corner of the Eastern Belt is coeval with the Sonoma Orogeny and the Middle–Late Triassic orogenesis of the Central Belt represents the Tahltanian Orogeny.

Paleomagnetism of the Triassic Guichon Batholith and Rotation in the Interior Plateau, British Columbia

1971 ◽  
Vol 8 (11) ◽  
pp. 1388-1396 ◽  
Author(s):  
D. T. A. Symons
Keyword(s):  
British Columbia ◽  
Pole Position ◽  
Upper Triassic ◽  
Late Triassic ◽  
Ratio Analysis ◽  
Tectonic Block ◽  
Clockwise Rotation ◽  
The North ◽  
South Central ◽  
Intrusive Rocks

The Guichon Batholith, located near the south end of the Interior Plateau in south–central British Columbia, is composed of unmetamorphosed massive felsic intrusive rocks in several distinct phases (Northcote 1969). Stratigraphic and radiometric evidence indicate that the batholith was emplaced during the Late Triassic (198 ± 8 m.y.) and unroofed by Early Jurassic. Analysis of the remanence of 92 cores (184 specimens) from 19 representative sites led to the isolation of a stable primary remanent magnetism at 15 sites after alternating-field demagnetization. Variance ratio analysis of the remanence directions indicates that the phases cannot be distinguished by the paleomagnetic method. This supports the evidence from contact relationships and K–Ar isotopic dating of biotites that the phases cooled nearly contemporaneously. The pole position determined for the Guichon Batholith (12.9° E, 65.6° N) is discordant with other Upper Triassic pole positions determined for North American formations. The discordance may be explained by a clockwise rotation 40° ± 10° of the batholith and surrounding rocks in the southern end of the Interior Plateau, with most of the Plateau to the north acting as a stable non-rotated tectonic block. Other evidence is cited which is consistent with this hypothesis.

Rb–Sr dates for granodiorite intrusions on the northeast margin of the Shuswap Metamorphic Complex, Cariboo Mountains, British Columbia

1977 ◽  
Vol 14 (7) ◽  
pp. 1690-1695 ◽  
Author(s):  
Lee C. Pigage
Keyword(s):  
British Columbia ◽  
Upper Jurassic ◽  
Upper Triassic ◽  
Time Interval ◽  
Metamorphic Complex ◽  
The North ◽  
Regional Deformation ◽  
Shuswap Metamorphic Complex ◽  
North And South ◽  
Provincial Park

Whole rock Rb–Sr dates of 138 ± 12 Ma (all five whole rocks) and 163 ± 7 Ma were obtained for granodiorite stocks in Wells Gray Provincial Park, Cariboo Mountains, British Columbia. These dates bracket the biotite K–Ar date of 143 ± 14 Ma determined previously by the Geological Survey of Canada. Two biotite – whole rock ± hornblende dates of 119 ± 11 Ma and 77 ± 20 Ma indicate isotopic resetting. Initial 87Sr–86Sr ratios vary from 0.7061 ± 0.0001 to 0.7103 ± 0.0002 for rock and mineral dates.When combined with field relations, these dates restrict regional deformation and metamorphism in this area to the time interval between Upper Triassic and Upper Jurassic. The resetting event was probably Eocene, as shown in other areas along regional strike to the north and south.

Paleomagnetism of the Triassic Nikolai Greenstone, McCarthy Quadrangle, Alaska

1977 ◽  
Vol 14 (11) ◽  
pp. 2578-2592 ◽  
Author(s):  
J. W. Hillhouse
Keyword(s):  
British Columbia ◽  
High Temperature ◽  
North America ◽  
Vertical Axis ◽  
Upper Triassic ◽  
Present Position ◽  
Stable Component ◽  
South Central ◽  
Early Mesozoic ◽  
Lamellar Texture

Paleomagnetic evidence indicates that the extensive early Mesozoic basalt field near McCarthy, south-central Alaska, originated far south of its present position relative to North America. Results obtained from the Middle and (or) Upper Triassic Nikolai Greenstone suggest that those basalts originated within 15° of the paleoequator. This position is at least 27° (3000 km) south of the Upper Triassic latitude predicted for McCarthy on the basis of paleomagnetic data from continental North America. The Nikolai pole, as determined from 50 flows sampled at 5 sites, is at 2.2° N, 146.1° E (α95 = 4.8°). The polarity of the pole is ambiguous, because the corresponding magnetic direction has a low inclination and a westerly declination. Therefore, the Nikolai may have originated near 15° N latitude or, alternatively, as far south as 15° S latitude. In addition to being displaced northward, the Nikolai block has been rotated roughly 90° about the vertical axis. A measure of the reliability of this pole is provided by favorable results from the following tests: (1) Within one stratigraphic section, normal and reversed directions from consecutive flows are antipolar. (2) Consistent directions were obtained from sites 30 km apart. (3) Application of the fold test indicated the magnetization was acquired before the rocks were folded. (4) The magnetizations of several pilot specimens are thermally stable up to 550 °C. The stable component is probably carried by magnetite with lamellar texture, a primary feature commonly acquired by a basalt at high temperature during initial cooling of the magma. Geologic and paleomagnetic evidence indicates that the Nikolai is allochthonous to Alaska and that, together with associated formations in southern Alaska and British Columbia, it is part of a now disrupted equatorial terrane.

The Great Tonalite Sill of southeastern Alaska and British Columbia: emplacement into an active contractional high angle reverse shear zone (extended abstract)

1992 ◽  
Vol 83 (1-2) ◽  
pp. 383-386 ◽  
Author(s):  
Donald H. W. Hutton ◽  
Gary M. Ingram
Keyword(s):  
British Columbia ◽  
Metamorphic Grade ◽  
High Grade ◽  
Metamorphic Complex ◽  
High Angle ◽  
Western Margin ◽  
Western Cordillera ◽  
Early Tertiary ◽  
The World ◽  
Gravina Belt

The Great Tonalite Sill (GTS) of southeastern Alaska and British Columbia (Brew & Ford 1981; Himmelberg et al. 1991) is one of the most remarkable intrusive bodies in the world: it extends for more than 800 km along strike and yet is only some 25 km or less in width. It consists of a belt of broadly tonalitic sheet-like plutons striking NW–SE and dipping steeply NE, and has been dated between 55 Ma and 81 Ma (J. L. Wooden, written communication to D. A. Brew, April 1990) (late Cretaceous to early Tertiary). The sill (it is steeply inclined and rather more like a “dyke”) is emplaced along the extreme western margin of the Coast Plutonic and Metamorphic Complex (CPMC), the high grade core of the Western Cordillera. The CPMC forms the western part of a group of tectonostratigraphic terranes including Stikine and Cache Creek, collectively known as the Intermontane Superterrane (Rubin et al. 1990). To the W of the GTS, rocks of the Insular Superterrane, including the Alexander and Wrangellia terranes and the Gravina belt, form generally lower metamorphic grade assemblages. The boundary between these two superterranes is obscure but it may lie close to, or be coincident with, the trace of the GTS.

Regional implications of Upper Triassic metavolcanic and metasedimentary rocks on the Chilkat Peninsula, southeastern Alaska

1980 ◽  
Vol 17 (6) ◽  
pp. 681-689 ◽  
Author(s):  
George Plafker ◽  
Travis Hudson
Keyword(s):  
British Columbia ◽  
Volcanic Rocks ◽  
Upper Triassic ◽  
Late Triassic ◽  
Low Grade ◽  
Lake Area ◽  
Metasedimentary Rocks

A low-grade metamorphic sequence consisting of thick mafic volcanic rocks overlain by calcareous flysch with very minor limestone underlies much of the Chilkat Peninsula. Fossils collected from both units are of Triassic age, probably late Karnian. This sequence appears to be part of the Taku terrane, a linear tectono-stratigraphic belt that now can be traced for almost 700 km through southeastern Alaska to the Kelsall Lake area of British Columbia. The age and gross lithology of the Chilkat Peninsula sequence are comparable to Upper Triassic rocks that characterize the allochthonous tectono-stratigraphic terrane named Wrangellia. This suggests either that the two terranes are related in their history or that they are allochthonous with respect to one another and coincidentally evolved somewhat similar sequences in Late Triassic time.

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