Age of the Bowen Island Group, southwestern Coast Mountains, British Columbia

1990 ◽  
Vol 27 (11) ◽  
pp. 1456-1461 ◽  
Author(s):  
R. M. Friedman ◽  
J. W. H. Monger ◽  
H. W. Tipper
Keyword(s):  
British Columbia ◽  
Middle Jurassic ◽  
Volcanic Rocks ◽  
Sedimentary Facies ◽  
Lower Jurassic ◽  
Coast Mountains ◽  
The North ◽  
Metavolcanic Rocks ◽  
Lake Formation ◽  
Island Group

A new U–Pb date of [Formula: see text] for foliated felsic metavolcanic rocks of the Bowen Island Group, from Mount Elphinstone in the southwesternmost Coast Mountains of British Columbia, indicates that there the age of this hitherto undated unit is early Middle Jurassic. These rocks grade along strike to the north-northwest into a more sedimentary facies, which north of Jervis Inlet contains a probable Sinemurian (Lower Jurassic) ammonite. The Bowen Island Group thus appears to include Lower and Middle Jurassic rocks and to be coeval in part with volcanic rocks of the Bonanza Formation on Vancouver Island to the west and the Harrison Lake Formation within the central Coast Mountains 75 km to the east.

Evolution of a Middle Jurassic volcanic arc: stratigraphic, isotopic, and geochemical characteristics of the Harrison Lake Formation, southwestern British Columbia

1995 ◽  
Vol 32 (10) ◽  
pp. 1759-1776 ◽  
Author(s):  
J. Brian Mahoney ◽  
Richard M. Friedman ◽  
Sean D. McKinley
Keyword(s):  
British Columbia ◽  
Middle Jurassic ◽  
Volcanic Rocks ◽  
Explosive Volcanism ◽  
Eastern Coast ◽  
Geochemical Data ◽  
Isotopic Data ◽  
Volcanic Arc ◽  
Fine Grained ◽  
Lake Formation

The Harrison Lake Formation is an Early to Middle Jurassic volcanic-arc assemblage unconformably overlying Triassic oceanic basement in the eastern Coast Belt of southwestern British Columbia. The formation is subdivided into four members including, in ascending order, the Celia Cove Member (conglomerate), the Francis Lake Member (fine-grained strata), the Weaver Lake Member (flows and breccias), and the Echo Island Member (pyroclastic and epiclastic strata). New biostratigraphic constraints pinpoint the initiation of volcanism to late early Toarcian. U–Pb geochronology demonstrates the arc was active until at least late Bajocian–early Bathonian time (166.0 ± 0.4 Ma), and that the timing of arc volcanism strongly overlaps emplacement of both hypabyssal intrusions (Hemlock Valley stock) and deep-seated plutons (Mount Jasper pluton) within and adjacent to the arc. Geochemical data indicate the arc is of medium- to high-K calc-alkaline affinity, and is strongly light rare earth element enriched (LaN/YbN = 1.5 – 2.5). Nd and Sr isotopic data from primary volcanic rocks demonstrate the juvenile nature of the magmatic system, but isotopic data from associated fine-grained sedimentary rocks suggest temporally controlled variations in isotopic composition interpreted to represent two-component mixing between juvenile volcanic detritus and a more evolved detrital component. The succession of facies in the Harrison Lake Formation records initial basin subsidence in the Early Jurassic, initiation of explosive volcanism in the late early Toarcian, a change to effusive volcanism in the early Aalenian, and late-stage explosive volcanism in the late Bajocian. The Harrison Lake Formation contains mesoscopic folds and overturned bedding that are absent in the overlying Callovian Mysterious Creek Formation, strongly suggesting the existence of a regional Bathonian deformational event in the southern Coast Belt.

Geology of the Chatham Sound region, southeast Alaska and coastal British Columbia

2001 ◽  
Vol 38 (11) ◽  
pp. 1579-1599 ◽  
Author(s):  
George E Gehrels
Keyword(s):  
British Columbia ◽  
Volcanic Rocks ◽  
Upper Jurassic ◽  
The West ◽  
Southeast Alaska ◽  
Coast Mountains ◽  
Early Tertiary ◽  
Metavolcanic Rocks ◽  
Upper Paleozoic ◽  
Coastal British Columbia

The Coast Mountains orogen is thought to have formed as a result of accretion of the Alexander and Wrangellia terranes against the western margin of the Stikine and Yukon–Tanana terranes, but the nature and age of accretion remain controversial. The Chatham Sound area, which is located along the west flank of the Coast Mountains near the Alaska – British Columbia border, displays a wide variety of relations that bear on the nature and age of the boundary between inboard and outboard terranes. Geologic and U–Pb geochronologic studies in this area reveal a coherent but deformed and metamorphosed sequence of rocks belonging to the Yukon–Tanana terrane, including pre-mid-Paleozoic marble, schist, and quartzite, mid-Paleozoic orthogneiss and metavolcanic rocks, and upper Paleozoic metaconglomerate and metavolcanic rocks. These rocks are overlain by Middle Jurassic volcanic rocks (Moffat volcanics) and Upper Jurassic – Lower Cretaceous strata of the Gravina basin, both of which also overlie Triassic and older rocks of the Alexander terrane. This overlap relationship demonstrates that the Alexander and Wrangellia terranes were initially accreted to the margin of inboard terranes during or prior to mid-Jurassic time. Accretion was apparently followed by Late Jurassic – Early Cretaceous extension–transtension to form the Gravina basin, left-slip along the inboard margin of Alexander–Wrangellia, mid-Cretaceous collapse of the Gravina basin and final structural accretion of the outboard terranes, and early Tertiary dip-slip motion on the Coast shear zone.

Nd isotopic characteristics of metamorphic and plutonic rocks of the Coast Mountains near Prince Rupert, British Columbia

1998 ◽  
Vol 35 (5) ◽  
pp. 556-561 ◽  
Author(s):  
P J Patchett ◽  
G E Gehrels ◽  
C E Isachsen
Keyword(s):  
British Columbia ◽  
Volcanic Rocks ◽  
Metamorphic Rocks ◽  
Published Data ◽  
Isotopic Data ◽  
Crustal Component ◽  
Coast Mountains ◽  
Crustal Rocks ◽  
Metasedimentary Rocks ◽  
Plutonic Rocks

Nd isotopic data are presented for a suite of metamorphic and plutonic rocks from a traverse across the Coast Mountains between Terrace and Prince Rupert, British Columbia, and for three contrasting batholiths in the Omineca Belt of southern Yukon. A presumed metamorphic equivalent of Jurassic volcanic rocks of the Stikine terrane gives epsilon Nd = +6, and a number of other metaigneous and metasedimentary rocks in the core of the Coast Mountains give epsilon Nd values from +3 to +7. A single metasedimentary rock approximately 3 km east of the Work Channel shear zone gives a epsilon Nd value of -9. Coast Belt plutons in the traverse yield epsilon Nd from -1 to +2. The Omineca Belt plutons give epsilon Nd from -10 to -17. All results are consistent with published data in demonstrating that (i) juvenile origins for both igneous and metamorphic rocks are common in the Coast Belt; (ii) representatives of a continental-margin sedimentary sequence with Precambrian crustal Nd are tectonically interleaved in the Coast Mountains; (iii) Coast Mountains plutons can be interpreted as derived from a blend of metamorphic rocks like those seen at the surface, or as arc-type melts contaminated with the older crustal component; and (iv) Omineca Belt plutons are dominated by remelted Precambrian crustal rocks.

Eocene paleo-physiography and drainage directions, southern Interior Plateau, British Columbia

2005 ◽  
Vol 42 (2) ◽  
pp. 215-230 ◽  
Author(s):  
Selina Tribe
Keyword(s):  
British Columbia ◽  
Middle Eocene ◽  
Regional Scale ◽  
River Valley ◽  
Coast Mountains ◽  
Base Level ◽  
The North ◽  
Bedrock Geology ◽  
River Valleys ◽  
Early Cenozoic

A map of reconstructed Eocene physiography and drainage directions is presented for the southern Interior Plateau region, British Columbia south of 53°N. Eocene landforms are inferred from the distribution and depositional paleoenvironment of Eocene rocks and from crosscutting relationships between regional-scale geomorphology and bedrock geology of known age. Eocene drainage directions are inferred from physiography, relief, and base level elevations of the sub-Eocene unconformity and the documented distribution, provenance, and paleocurrents of early Cenozoic fluvial sediments. The Eocene landscape of the southern Interior Plateau resembled its modern counterpart, with highlands, plains, and deeply incised drainages, except regional drainage was to the north. An anabranching valley system trending west and northwest from Quesnel and Shuswap Highlands, across the Cariboo Plateau to the Fraser River valley, contained north-flowing streams from Eocene to early Quaternary time. Other valleys dating back at least to Middle Eocene time include the North Thompson valley south of Clearwater, Thompson valley from Kamloops to Spences Bridge, the valley containing Nicola Lake, Bridge River valley, and Okanagan Lake valley. During the early Cenozoic, highlands existed where the Coast Mountains are today. Southward drainage along the modern Fraser, Chilcotin, and Thompson River valleys was established after the Late Miocene.

scholarly journals Observations on the May 2019 Joffre Peak landslides, British Columbia

Landslides ◽  
2020 ◽  
Vol 17 (4) ◽  
pp. 913-930 ◽  
Author(s):  
Pierre Friele ◽  
Tom H. Millard ◽  
Andrew Mitchell ◽  
Kate E. Allstadt ◽  
Brian Menounos ◽  
...  
Keyword(s):  
British Columbia ◽  
Debris Flow ◽  
Seismic Analysis ◽  
Rock Avalanche ◽  
Permafrost Degradation ◽  
Depth Estimate ◽  
Coast Mountains ◽  
Conditioning Factors ◽  
The North ◽  
Debris Flood

AbstractTwo catastrophic landslides occurred in quick succession on 13 and 16 May 2019, from the north face of Joffre Peak, Cerise Creek, southern Coast Mountains, British Columbia. With headscarps at 2560 m and 2690 m elevation, both began as rock avalanches, rapidly transforming into debris flows along middle Cerise Creek, and finally into debris floods affecting the fan. Beyond the fan margin, a flood surge on Cayoosh Creek reached bankfull and attenuated rapidly downstream; only fine sediment reached Duffey Lake. The toe of the main debris flow deposit reached 4 km from the headscarp, with a travel angle of 0.28, while the debris flood phase reached the fan margin 5.9 km downstream, with a travel angle of 0.22. Photogrammetry indicates the source volume of each event is 2–3 Mm3, with combined volume of 5 Mm3. Lidar differencing, used to assess deposit volume, yielded a similar total result, although error in the depth estimate introduced large volume error masking the expected increase due to dilation and entrainment. The average velocity of the rock avalanche-debris flow phases, from seismic analysis, was ~ 25–30 m/s, and the velocity of the 16 May debris flood on the upper fan, from super-elevation and boulder sizes, was 5–10 m/s. The volume of debris deposited on the fan was ~ 104 m3, 2 orders of magnitude less than the avalanche/debris flow phases. Progressive glacier retreat and permafrost degradation were likely the conditioning factors; precursor rockfall activity was noted at least ~6 months previous; thus, the mountain was primed to fail. The 13 May landslide was apparently triggered by rapid snowmelt, with debuttressing triggering the 16 May event.

Crustal velocity structure of the southern Nechako basin, British Columbia, from wide-angle seismic traveltime inversion1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.

2011 ◽  
Vol 48 (6) ◽  
pp. 1050-1063 ◽  
Author(s):  
A.L. Stephenson ◽  
G.D. Spence ◽  
K. Wang ◽  
J.A. Hole ◽  
K.C. Miller ◽  
...  
Keyword(s):  
British Columbia ◽  
Mountain Pine Beetle ◽  
Velocity Structure ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Velocity Model ◽  
Seismic Profile ◽  
Wide Angle ◽  
Seismic Velocities ◽  
Coast Mountains

In the BATHOLITHSonland seismic project, a refraction – wide-angle reflection survey was shot in 2009 across the Coast Mountains and Interior Plateau of central British Columbia. Part of the seismic profile crossed the Nechako Basin, a Jurassic–Cretaceous basin with potential for hydrocarbons within sedimentary strata that underlies widespread volcanic rocks. Along this 205 km-long line segment, eight large explosive shots were fired into 980 seismometers. Forward and inverse modelling of the traveltime data were conducted with two independent methods: ray-tracing based modelling of first and secondary arrivals, and a higher resolution wavefront-based first-arrival seismic tomography. Material with velocities less than 5.0 km/s is interpreted as sedimentary rocks of the Nechako Basin, while velocities from 5.0–6.0 km/s may correspond to interlayered sedimentary and volcanic rocks. The greatest thickness of sedimentary rocks in the basin is found in the central 110 km of the profile. Two sub-basins were identified in this region, with widths of 20–50 km and maximum sedimentary depths of 2.5 and 3.3 km. Such features are well-defined in the velocity model, since resolution tests indicate that features with widths greater than ∼13 km are reliable. Beneath the sedimentary rocks, seismic velocities increase more slowly with depth — from 6.0 km/s just below the basin to 6.3 km/s at ∼17 km in depth, and then to 6.8–7.0 km/s at the base of the crust. The Moho is found at a depth of 33.5–35 km beneath the profile, and mantle velocities are high at 8.05–8.10 km/s.

Coquitlam Drift: a pre-Vashon Fraser glacial formation in the Fraser Lowland, British Columbia

1981 ◽  
Vol 18 (9) ◽  
pp. 1443-1451 ◽  
Author(s):  
Stephen R. Hicock ◽  
John E. Armstrong
Keyword(s):  
British Columbia ◽  
Glacial Maximum ◽  
Cascade Mountains ◽  
Short Pulses ◽  
Coast Mountains ◽  
The North ◽  
Glaciomarine Sediments

Coquitlam Drift is formally defined and stratotypes established for it in the Coquitlam – Port Moody area, B.C. It is a Pleistocene formation consisting of till, glaciofluvial, ice-contact, and glaciomarine sediments deposited between 21 700 and 18 700 years BP, during the Fraser Glaciation (late Wisconsin) and prior to the main Vashon glacial maximum at about 14 500 years BP. The drift was deposited in short pulses by valley and piedmont glaciers fluctuating into the Fraser Lowland from the Coast Mountains to the north and Cascade Mountains to the east.

Nina Creek Group and Lay Range Assemblage, north-central British Columbia: remnants of late Paleozoic oceanic and arc terranes

1997 ◽  
Vol 34 (6) ◽  
pp. 854-874 ◽  
Author(s):  
Filippo Ferri
Keyword(s):  
British Columbia ◽  
North America ◽  
Volcanic Rocks ◽  
Tholeiitic Basalt ◽  
Ocean Floor ◽  
North Central ◽  
Marginal Basin ◽  
The North ◽  
Lower Division ◽  
Ocean Ridge

In north-central British Columbia, a belt of upper Paleozoic volcanic and sedimentary rocks lies between Mesozoic arc rocks of Quesnellia and Ancestral North America. These rocks belong to two distinct terranes: the Nina Creek Group of the Slide Mountain terrane and the Lay Range Assemblage of the Quesnel terrane. The Nina Creek Group is composed of Mississippian to Late Permian argillite, chert, and mid-ocean-ridge tholeiitic basalt, formed in an ocean-floor setting. The sedimentary and volcanic rocks, the Mount Howell and Pillow Ridge successions, respectively, form discrete, generally coeval sequences interpreted as facies equivalents that have been interleaved by thrusting. The entire assemblage has been faulted against the Cassiar terrane of the North American miogeocline. West of the Nina Creek Group is the Lay Range Assemblage, correlated with the Harper Ranch subterrane of Quesnellia. It includes a lower division of Mississippian to Early Pennsylvanian sedimentary and volcanic rocks, some with continental affinity, and an upper division of Permian island-arc, basaltic tuffs and lavas containing detrital quartz and zircons of Proterozoic age. Tuffaceous horizons in the Nina Creek Group imply stratigraphic links to a volcanic-arc terrane, which is inferred to be the Lay Range Assemblage. Similarly, gritty horizons in the lower part of the Nina Creek Group suggest links to the paleocontinental margin to the east. It is assumed that the Lay Range Assemblage accumulated on a piece of continental crust that rifted away from ancestral North America in the Late Devonian to Early Mississippian by the westward migration of a west-facing arc. The back-arc extension produced the Slide Mountain marginal basin in which the Nina Creek Group was deposited. Arc volcanism in the Lay Range Assemblage and other members of the Harper Ranch subterrane was episodic rather than continuous, as was ocean-floor volcanism in the marginal basin. The basin probably grew to a width of hundreds rather than thousands of kilometres.

Development of late Paleozoic volcanic arcs in the Canadian Cordillera: an example from the Klinkit Group, northern British Columbia and southern Yukon

2003 ◽  
Vol 40 (7) ◽  
pp. 907-924 ◽  
Author(s):  
Renée-Luce Simard ◽  
Jaroslav Dostal ◽  
Charlie F Roots
Keyword(s):  
British Columbia ◽  
North America ◽  
Volcanic Rocks ◽  
Late Paleozoic ◽  
Canadian Cordillera ◽  
Alkali Basalts ◽  
The North ◽  
Pacific Margin ◽  
North American Craton ◽  
Arc Setting

The late Paleozoic volcanic rocks of the northern Canadian Cordillera lying between Ancestral North America to the east and the accreted terranes of the Omineca belt to the west record early arc and rift magmatism along the paleo-Pacific margin of the North American craton. The Mississippian to Permian volcano-sedimentary Klinkit Group extends discontinuously over 250 km in northern British Columbia and southern Yukon. The two stratotype areas are as follows: (1) in the Englishman Range, southern Yukon, the English Creek Limestone is conformably overlain by the volcano-sedimentary Mount McCleary Formation (Lower Clastic Member, Alkali-Basalt Member and Volcaniclastic Member), and (2) in the Stikine Ranges, northern British Columbia, the Screw Creek Limestone is conformably overlain by the volcano-sedimentary Butsih Formation (Volcaniclastic Member and Upper Clastic Member). The calc-alkali nature of the basaltic volcaniclastic members of the Klinkit Group indicates a volcanic-arc setting ((La/Yb)N = 2.77–4.73), with little involvement of the crust in their genesis (εNd = +6.7 to +7.4). Alkali basalts in the Mount McCleary Formation ((La/Yb)N = 12.5–17.8) suggest periodic intra-arc rifting events. Broadly coeval and compositionally similar volcano-sedimentary assemblages occur in the basement of the Mesozoic Quesnel arc, north-central British Columbia, and in the pericratonic Yukon–Tanana composite terrane, central Yukon, suggesting that they all represent pieces of a single long-lived, late Paleozoic arc system that was dismembered prior to its accretion onto Ancestral North America. Therefore, Yukon–Tanana terrane is possibly the equivalent to the basement of Quesnel terrane, and the northern Quesnel terrane has a pericratonic affinity.

Large volume silicic volcanism along the proto-Pacific margin of Gondwana: lithological and stratigraphical investigations from the Antarctic Peninsula

1999 ◽  
Vol 136 (1) ◽  
pp. 1-16 ◽  
Author(s):  
TEAL R. RILEY ◽  
PHILIP T. LEAT
Keyword(s):  
Antarctic Peninsula ◽  
Middle Jurassic ◽  
East Coast ◽  
Volcanic Rocks ◽  
Lower Jurassic ◽  
Fossil Flora ◽  
Metasedimentary Rocks ◽  
Close Relationship ◽  
Pacific Margin ◽  
The Antarctic

Jurassic magmatism in western Gondwana produced the most voluminous episode of continental volcanism in the Phanerozoic era. During the Early to Middle Jurassic, some 2.5–3 million km3 of dominantly basalt, and to a lesser extent rhyolite, were erupted onto a supercontinent in the early stages of break-up. The major silicic portion of the Gondwana magmatic province is exposed in Patagonian South America. The volcanic rocks of Patagonia have been collectively termed the Chon-Aike Province and constitute one of the world's most voluminous silicic provinces. The volcanic rocks are predominantly pyroclastic, dominated by ignimbrite units of rhyolite composition. Volcanic rocks crop out sporadically across much of the once contiguous Antarctic Peninsula, and are considered to form an extension of the Chon-Aike Province. A continuation of the province to include the Antarctic Peninsula would extend its strike length along the active Pacific margin by c. 2000 km.Volcanic rocks exposed along the east coast of the Antarctic Peninsula, defined here as the Mapple Formation, are also dominated by rhyolitic ignimbrite flows, with individual units up to 80 m in thickness, and a total thickness of c. 1 km. The ignimbrites vary in degree of welding, from high-grade rheomorphic ignimbrites with parataxitic textures, to unwelded, lithic-rich ignimbrites. Rhyolite lava flows, air-fall horizons, debris flow deposits and epiclastic deposits are volumetrically minor, occurring as interbedded units within the ignimbrite succession.The lithology and stratigraphy of the Jurassic volcanic rocks of the Mapple Formation are presented, and comparisons are made to the Chon-Aike Province. A consistent stratigraphy of Permo-Triassic metasedimentary rocks, unconformably overlain by terrestrial mudstone–siltstone sequences, which are in turn conformably overlain by largely silicic, subaerial volcanic rocks, is present at several localities along the Antarctic Peninsula, and at localities in the Chon-Aike Province. Precise (zircon U–Pb) Middle Jurassic ages exist for two volcanic formations from the Antarctic Peninsula, and a Middle–Lower Jurassic age has been suggested for the underlying sedimentary formations based on fossil flora analysis. The Antarctic Peninsula chronostratigraphy, coupled with lithological similarities, indicate a close relationship to those sequences of the Chon-Aike province.

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