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.

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.

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.

Age and Correlation of the Kobau Group, Mount Kobau, British Columbia

1973 ◽  
Vol 10 (10) ◽  
pp. 1508-1518 ◽  
Author(s):  
Andrew V. Okulitch
Keyword(s):  
British Columbia ◽  
Volcanic Rocks ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
South Central ◽  
Shuswap Metamorphic Complex ◽  
Basic Volcanic ◽  
Devonian Age ◽  
Tertiary Period ◽  
Okanagan Valley

The Kobau Group, found in south-central British Columbia, consists of highly deformed, low-grade metamorphic rocks derived from a succession of sedimentary and basic volcanic rocks of pre-Cretaceous, likely post-Devonian age. Deformation began in Carboniferous times and recurred with decreasing intensity up to the Tertiary Period. Possible correlative successions are found surrounding Mount Kobau. These include possibly late Paleozoic formations west and northwest of Mount Kobau, the Carboniferous to Permian Anarchist Group found south of the 49th parallel and east of the Okanagan Valley, the pre-Upper Triassic, possibly Mississippian Chapperon Group west of Vernon, and parts of the Shuswap Metamorphic Complex east of the Okanagan Valley. Prior to deposition of the Kobau Group, part of the Shuswap Complex was subjected to deformation, presumably in mid-Paleozoic time.

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.

Extending the ancient margin outboard in the Canadian Cordillera: record of Proterozoic crust and Paleocene regional metamorphism in the Nicola horst, southern British Columbia

2002 ◽  
Vol 39 (11) ◽  
pp. 1605-1623 ◽  
Author(s):  
Philippe Erdmer ◽  
John M Moore ◽  
Larry Heaman ◽  
Robert I Thompson ◽  
Ken L Daughtry ◽  
...  
Keyword(s):  
British Columbia ◽  
Regional Metamorphism ◽  
Geological Mapping ◽  
Detrital Zircons ◽  
Source Rocks ◽  
Late Triassic ◽  
Low Grade ◽  
Rock Types ◽  
Ductile Flow ◽  
Juvenile Crust

The Nicola horst exposes plutonic and amphibolite-grade metamorphic rocks and is surrounded by low-grade arc rocks of the Late Triassic Nicola Group. We present new geological mapping and U–Pb, Nd, and metamorphic data for the Nicola horst near Bob Lake, ~40 km south of Kamloops, British Columbia. The Bob Lake assemblage includes felsic to intermediate metavolcaniclastic rocks, metaconglomerate, schist, phyllite, and other rock types. From U–Pb zircon analysis, a felsic metaporphyry clast in metaconglomerate is 1.04 Ga old. The oldest detrital zircons in metaconglomerate and schist are also near 1 Ga. The Bob Lake assemblage was intruded by 230 Ma tonalite, 219 Ma diorite, and 64 Ma leucogranite and includes 161 Ma felsic porphyry and 157 Ma rhyodacite. Amphibolite-grade metamorphism and ductile flattening and stretching affected all rocks except crosscutting Paleocene granite and granodiorite. The high-grade rocks may be exposed as a result of latest Cretaceous – Eocene extensional ductile flow beneath a thin brittle upper crust. A thickness of ~20 km of juvenile crust beneath the proposed Quesnel terrane is inconsistent with the evidence of Proterozoic source rocks at surface. We infer that most of the crustal lithosphere in this part of the Intermontane Belt is continental, which does not preclude possibly thick arc rocks in other parts. The local thinness of the Nicola Group, however, is inconsistent with emplacement as a regional allochthon and thus with their inclusion in a Quesnel "terrane." The Nicola arc succession appears to have been built on the ancient continental margin.

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.

Seismic and potential‐field imaging of the Guichon Creek batholith, British Columbia, Canada, to delineate structures hosting porphyry copper deposits

Geophysics ◽  
2000 ◽  
Vol 65 (5) ◽  
pp. 1418-1434 ◽  
Author(s):  
Baishali Roy ◽  
Ron M. Clowes
Keyword(s):  
British Columbia ◽  
Seismic Reflection ◽  
Porphyry Copper ◽  
Regional Scale ◽  
Low Grade ◽  
Depth Range ◽  
Porphyry Copper Deposits ◽  
Near Surface ◽  
Copper Deposits ◽  
South Central

The Guichon Creek batholith (GCB), located in south‐central British Columbia, contains several large, low‐grade copper deposits of considerable economic importance. The surface geology of the Guichon batholith and its surrounding region have been well mapped; however, little information about subsurface features is available. The batholith consists of four major phases, emplaced radially outward, which can be separated on the basis of their texture and composition. Previous interpretation of gravity data suggests a mushroom‐shaped structure for the batholith. Data from Lithoprobe seismic reflection line 88-11, acquired across the batholith in 1988, reveal weakly coherent east‐dipping reflections on the west side and west‐dipping reflections on the east in the upper 10 km. To determine if these are related to structures associated with the batholith, we reprocessed the upper 6 s with particular emphasis on applications of signal enhancement techniques (e.g., pattern recognition methods, refraction statics, dip moveout corrections) and correlation of the improved subsurface images with the geological environment associated with porphyry copper deposits. Low near‐surface velocities correlate well with the phases of the batholith hosting the major copper deposits, which structurally lie in faulted and brecciated regions. Although the top 1.5 km cannot be imaged by the regional‐scale seismic reflection data, the reprocessed seismic section helps define the edges of the batholith, its various concentric phases, and the stem in the depth range of 1.5 to 10 km. The seismic results are complemented by 2.5-D (profile sense) modeling and 3-D inversion of regional‐scale gravity and high‐resolution aeromagnetic data. These show a low‐density and low‐magnetic‐susceptibility region associated with the batholith that extends to more than 10 km depth. The region of active mining interest lies above a circular low‐susceptibility area at 2 km depth and a low‐velocity region. Integrated interpretation of geophysical results and geological observations indicates the GCB is a funnel‐shaped feature in which mineralization is located above the stem of the batholith.

scholarly journals First record of Mesozoic terrestrial vertebrates from Lithuania: phytosaurs (Diapsida: Archosauriformes) of probable Late Triassic age, with a review of phytosaur biogeography

2012 ◽  
Vol 150 (1) ◽  
pp. 110-122 ◽  
Author(s):  
STEPHEN L. BRUSATTE ◽  
RICHARD J. BUTLER ◽  
GRZEGORZ NIEDŹWIEDZKI ◽  
TOMASZ SULEJ ◽  
ROBERT BRONOWICZ ◽  
...  
Keyword(s):  
North America ◽  
Arid Regions ◽  
First Record ◽  
Upper Triassic ◽  
Late Triassic ◽  
Early Triassic ◽  
Baltic Region ◽  
Terrestrial Vertebrates ◽  
Terrestrial Vertebrate

AbstractFossils of Mesozoic terrestrial vertebrates from Lithuania and the wider East Baltic region of Europe have previously been unknown. We here report the first Mesozoic terrestrial vertebrate fossils from Lithuania: two premaxillary specimens and three teeth that belong to Phytosauria, a common clade of semiaquatic Triassic archosauriforms. These specimens represent an uncrested phytosaur, similar to several species within the generaPaleorhinus,Parasuchus,RutiodonandNicrosaurus. Because phytosaurs are currently only known from the Upper Triassic, their discovery in northwestern Lithuania (the Šaltiškiai clay-pit) suggests that at least part of the Triassic succession in this region is Late Triassic in age, and is not solely Early Triassic as has been previously considered. The new specimens are among the most northerly occurrences of phytosaurs in the Late Triassic, as Lithuania was approximately 7–10° further north than classic phytosaur-bearing localities in nearby Germany and Poland, and as much as 40° further north than the best-sampled phytosaur localities in North America. The far northerly occurrence of the Lithuanian fossils prompts a review of phytosaur biogeography and distribution, which suggests that these predators were widely distributed in the Triassic monsoonal belt but rarer in more arid regions.

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.

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.

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