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.

The southern Coast Mountains, British Columbia: New interpretations from geological, seismic reflection, and gravity data

2013 ◽  
Vol 50 (10) ◽  
pp. 1033-1050 ◽  
Author(s):  
Amanda M.M. Bustin ◽  
Ron M. Clowes ◽  
James W.H. Monger ◽  
J. Murray Journeay
Keyword(s):  
British Columbia ◽  
Early Cretaceous ◽  
Middle Jurassic ◽  
Gravity Data ◽  
Normal Faults ◽  
Southern Coast ◽  
Seismic Profiles ◽  
Coast Mountains ◽  
Clastic Rocks ◽  
Coast Plutonic Complex

The southern Coast Mountains of British Columbia are characterized by voluminous plutonic and gneissic rocks of mainly Middle Jurassic to Eocene age (the Coast Plutonic Complex), as well as metamorphic rocks, folds, and thrust and reverse faults that mostly diverge eastward and westward from an axis within the present mountains, and by more localized Eocene and younger normal faults. In the southeastern Coast Mountains, mid-Cretaceous and younger plutons intrude Bridge River, Cadwallader, and Methow terranes and overlap Middle Jurassic through Early Cretaceous marine clastic rocks of the Tyaughton–Methow basin. The combination of geological data with new or reanalyzed geophysical data originating from Lithoprobe and related studies enables revised structural interpretations to be made to 20 km depth. Five seismic profiles show very cut-up and chaotic reflectivity that probably represents slices and segments of different deformed and rearranged rock assemblages. Surface geology, seismic interpretations, physical properties, and gravity data are combined in two profiles across the Coast Mountains to generate two new 2-D density models that are interpreted in terms of the geological units. The western part of the southern Coast Mountains consists primarily of Jurassic to mid-Cretaceous plutons to depths of 20 km with slices of Wrangellia (in the west) and Early Cretaceous volcanic and sedimentary rocks (Gambier group) in the upper 10 km. The eastern part, east of the Owl Creek fault, consists of slices of Cadwallader and Bridge River terranes and Tyaughton–Methow basin strata with limited slices of plutonic rocks at depths less than 10 km. Below that, Eocene and Late Cretaceous plutons dominate for another 10 km.

Relay Mountain Group, Tyaughton–Methow basin, southwest British Columbia: a major Middle Jurassic to Early Cretaceous terrane overlap assemblage

2002 ◽  
Vol 39 (7) ◽  
pp. 1143-1167 ◽  
Author(s):  
Paul J Umhoefer ◽  
Paul Schiarizza ◽  
Matt Robinson
Keyword(s):  
British Columbia ◽  
Lower Cretaceous ◽  
Middle Jurassic ◽  
The West ◽  
Shallow Marine ◽  
Clastic Rocks ◽  
Marine Facies ◽  
Oblique Convergent ◽  
Back Arc ◽  
Middle Unit

The upper Middle Jurassic to Lower Cretaceous Relay Mountain Group is the lower part of the northern Tyaughton–Methow basin, southwestern British Columbia. The Relay Mountain Group consists of ~2700–3400 m of clastic rocks that we subdivide into three formal formations. The Callovian and lower Oxfordian Tyoax Pass Formation is marine shale and sandstone turbidites. The Teepee Mountain Formation consists of upper Oxfordian to Valanginian shallow marine clastic rocks with common Buchia and fluvial and marginal marine facies in the upper part of the unit in the northwest. These rocks overlie the lower formation across an abrupt conformable to disconformable contact. The Hauterivian (and Barremian?) Potato Range Formation consists of clastic rocks that are marine in the southeast, mainly nonmarine to the northwest, and derived from the west. This unit displays an abrupt conformable to disconformable contact with the middle formation and locally rests above the lower formation across an angular unconformity. The Relay Mountain Group and correlative strata of the southeastern Coast Belt form an overlap assemblage above the Bridge River and Cadwallader (including Methow) terranes and link them by late Middle Jurassic time. The early Relay Mountain Group appears to have been a fore-arc basin, possibly along an oblique–convergent margin in the middle unit. The upper unit indicates major changes to a back-arc basin linked to the Ottarasko, and possibly Gambier, arc to the west. This is the oldest probable link (~130 Ma) between the southeastern and southwestern Coast belts.

Provenance and tectonic setting of the Triassic clastic deposits in the Napo basin, South China: evidence from petrography, whole-rock geochemistry and detrital zircon U–Pb geochronology

2021 ◽  
pp. 1-20
Author(s):  
Lei Xia ◽  
Quan-Ren Yan ◽  
Zhong-Jin Xiang ◽  
Hong-Bo Zheng ◽  
Quan-Lin Hou ◽  
...  
Keyword(s):  
South China ◽  
Detrital Zircon ◽  
Middle Triassic ◽  
Tectonic Setting ◽  
Detrital Zircons ◽  
Island Arc ◽  
Late Permian ◽  
Magmatic Arc ◽  
Clastic Rocks ◽  
Arc Setting

Abstract The provenance and tectonic setting of the Lower–Middle Triassic clastic sediments from the Napo basin, South China, have been examined here using detrital modes, whole-rock geochemistry and detrital zircon U–Pb ages. Field investigations indicate that these sediments consist of fan delta, slope and turbidity fan facies with dominantly southward palaeocurrent directions. Detrital modes and geochemical characteristics of the clastic rocks indicate that they were derived from mixed magmatic arc and Palaeozoic successions in a continental island arc setting, with no significant sediment recycling. The U–Pb age spectra of sandstone detrital zircons from different stratigraphic positions are similar, with one major group (300–230 Ma), two subordinate groups (400–320 Ma and 480–420 Ma, respectively) and two scattered groups (1200–800 Ma and 2000–1700 Ma, respectively). Thus, we consider that the north late Permian – Middle Triassic volcanic rocks and the uplifted Palaeozoic sedimentary/volcanic sequences constituted the predominant sources. The detritus derived from the late Permian Emeishan mafic rocks is subordinate and limited. The pre-Devonian zircons are likely sedimentary-recycled or magmatic-captured instead of directly derived from the early Palaeozoic orogen (e.g. Yunkai massif) and Neoproterozoic Jiangnan orogen because of the topographic barrier of a magmatic arc and carbonate platform. Considering the spatial and temporal distribution characteristics of the volcanic arc and ophiolite, we suggest that the Triassic Napo basin was a fore-arc basin within a continental island arc setting, which developed in response to the northward subduction of the Babu–Cao Bang branch ocean beneath the South China Block.

U–Pb and K–Ar dates related to the timing of magmatism and deformation in the Cache Creek terrane and Quesnellia, southern British Columbia

1990 ◽  
Vol 27 (1) ◽  
pp. 117-123 ◽  
Author(s):  
N. Mortimer ◽  
P. van der Heyden ◽  
R. L. Armstrong ◽  
J. Harakal
Keyword(s):  
British Columbia ◽  
Early Cretaceous ◽  
North American ◽  
Late Jurassic ◽  
Early Jurassic ◽  
Early Permian ◽  
Magmatic Arc ◽  
Plutonic Complex ◽  
Minimum Age ◽  
Coast Plutonic Complex

U–Pb dating of zircon from the Guichon Creek batholith indicates an emplacement age of 210 ± 3 Ma. Comparison with previously published K–Ar (211–188 Ma) and Rb–Sr (205 and 196 Ma) dates reveals that intrusion, mineralization, cooling, and uplift of the batholith took some 20 Ma, spanning the Triassic–Jurassic boundary on the Decade of North American Geology (DNAG) time scale.The Mount Martley pluton and Tiffin Creek stock yield Late Jurassic dates of 155 ± 2 Ma (U–Pb, zircon) and 152 ± 5 Ma (K–Ar, hornblende), respectively, and provide a reliable minimum age (Kimmeridgian) for penetrative deformation in the Cache Creek terrane. K–Ar whole-rock dates from Cache Creek terrane and Ashcroft Formation argillites range from Early Permian (266 ± 8 Ma) and Early Jurassic (194 ± 6 Ma) to Late Jurassic, Kimmeridgian (154 ± 5 Ma). We interpret the younger dates as recording Middle–Late Jurassic tectonism and the older ones as possible relics from earlier deformation episodes.An Early Cretaceous K–Ar date (129 ± 5 Ma) for a lamprophyre dike that cuts the Nicola Group suggests that the Early Cretaceous magmatic arc of the Coast Plutonic Complex had an eastern alkalic fringe in the Intermontane Belt.

Structural relationships of the Skeena Fold Belt west of the Bowser Basin, northwest British Columbia

1991 ◽  
Vol 28 (6) ◽  
pp. 973-983 ◽  
Author(s):  
Carol A. Evenchick
Keyword(s):  
Middle Jurassic ◽  
Large Scale ◽  
Volcanic Rocks ◽  
Western Boundary ◽  
Thrust Faults ◽  
Fold Belt ◽  
Clastic Rocks ◽  
Structural Style ◽  
Coast Plutonic Complex ◽  
The Difference

The Skeena Fold Belt is a regional fold and thrust belt that extends across most of the width of the northern Intermontane Belt of the Canadian Cordillera. Structural and stratigraphic relationships at its northeast margin show that it developed between latest Jurassic(?) and early Tertiary time, that it involved strata at least as low as Lower and Middle Jurassic Hazelton Group, and that it is characterized by northeast-verging folds and thrust faults. The structures accommodated at least 44% shortening and appear to root to the west.Most of the fold belt is distinguished by folds in thinly layered Jurassic and Cretaceous clastic rocks of the Bowser and Sustut basins. Its boundary is difficult to establish west of the Bowser Basin in poorly layered Middle Jurassic and older strata. However, map relationships show that Hazelton Group strata are folded with Bowser Lake Group. It is suggested here that the fold belt continues westward to the east margin of the Coast Plutonic Complex, where the increase in metamorphic grade and dominance of plutonic rocks effectively mark the western boundary of the Skeena Fold Belt. The difference in structural style between the Bowser Lake Group and massive volcanic rocks of the Hazelton Group is attributed to their difference in competency. Shortening by thrust faults and large-scale folds in volcanic rocks west of the Bowser Basin may balance with shortening by folds and related detachments in Bowser Lake Group farther east.

scholarly journals Statherian (ca. 1714–1680 Ma) Extension-Related Magmatism and Deformation in the Southwestern Korean Peninsula and Its Geological Significance: Constraints from the Petrological, Structural, Geochemical and Geochronological Studies of Newly Identified Granitoids

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 557
Author(s):  
Byung-Choon Lee ◽  
Weon-Seo Kee ◽  
Uk-Hwan Byun ◽  
Sung-Won Kim
Keyword(s):  
Korean Peninsula ◽  
Tectonic Setting ◽  
Alkali Feldspar ◽  
Ductile Deformation ◽  
Southwestern Part ◽  
The North ◽  
Deformation Event ◽  
Geochemical Analyses ◽  
A Minor ◽  
T Values

In this study, petrological, structural, geochemical, and geochronological analyses of the Statherian alkali feldspar granite and porphyritic alkali feldspar granite in the southwestern part of the Korean Peninsula were conducted to examine petrogenesis of the granitoids and their tectonic setting. Zircon U-Pb dating revealed that the two granites formed around 1.71 Ga and 1.70–1.68 Ga, respectively. The results of the geochemical analyses showed that both of the granites have a high content of K2O, Nb, Ta, and Y, as well as high FeOt/MgO and Ga/Al ratios. Both granites have alkali-calcic characteristics with a ferroan composition, indicating an A-type affinity. Zircon Lu-Hf isotopic compositions yielded negative εHf(t) values (−3.5 to −10.6), indicating a derivation from ancient crustal materials. Both granite types underwent ductile deformation and exhibited a dextral sense of shear with a minor extension component. Based on field relationships and zircon U-Pb dating, it was considered that the deformation event postdated the emplacement of the alkali feldspar granite and terminated soon after the emplacement of the porphyritic alkali feldspar granite in an extensional setting. These data indicated that there were extension-related magmatic activities accompanying ductile deformation in the southwestern part of the Korean Peninsula during 1.71–1.68 Ga. The Statherian extension-related events are well correlated with those in the midwestern part of the Korean and eastern parts of the North China Craton.

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