Structural and stratigraphic setting of the Downie slide, Columbia River valley, British Columbia

1980 ◽  
Vol 17 (6) ◽  
pp. 698-709 ◽  
Author(s):  
Richard L. Brown ◽  
John F. Psutka
Keyword(s):  
British Columbia ◽  
Shear Zone ◽  
Columbia River ◽  
River Valley ◽  
Axial Plane ◽  
Western Slope ◽  
Second Phase ◽  
Main Body ◽  
The North ◽  
Slide Mass

The Downie slide is a late to postglacial rockslide situated on the western slope of the Columbia River valley about 70 km north of Revelstoke, British Columbia. It attains a maximum thickness of 270 m and is estimated to involve 1.5 × 109 m3 of rock and debris. The head of the slide is bounded by a nearly vertical escarpment reaching heights of more than 125 m; its lateral boundaries are defined by a prominent east–west trending scarp on the south and a more subdued linear northeast trending ridge on the north. The toe forms the west bank of the Columbia River in this area.The slide occurs within a compositionally anisotropic formation of high-grade pelitic and semipelitic schists and psammites. The main shear zone at the base of the slide is located in pelitic schists. Minerals in the rock of the shear zone have been mechanically crushed and locally reduced to a fine-grained gouge.Three distinct phases of deformation are recognized in the Downie slide region. The location and attitude of the second and third fold phases and their associated fabrics controlled the external geometry of the slide.Along the western slopes of this part of the Columbia River valley the second phase of deformation has been dominant. Within the formation that contains the slide, bedding is extensively deformed by tight to isoclinal second phase minor folds that exhibit a penetrative axial plane foliation. At Downie slide this foliation dips approximately 20° eastward towards the Columbia River, and nearly parallels the slope of the hillside; the basal shear zone of the slide developed parallel to the axial plane foliation.West of the slide, third phase major and minor folds have been superimposed on the second phase geometry, but they die out eastward, and are of only minor significance within the main body of the slide. The eastern limit of major superposition coincides with the head scarp of the slide. The slide mass broke away along the hinge zone of the first major monoclinal flexure fold associated with this front of phase 3 folding.Late fracturing probably influenced the position of the northern and southern lateral boundaries of the slide.

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.

Structural and metamorphic relationships between the Mount Ida and Monashee Groups at Mara Lake, British Columbia

1982 ◽  
Vol 19 (2) ◽  
pp. 288-307 ◽  
Author(s):  
Kent C. Nielsen
Keyword(s):  
British Columbia ◽  
Large Scale ◽  
Ductile Deformation ◽  
Late Triassic ◽  
Second Phase ◽  
The West ◽  
Late Mesozoic ◽  
The North ◽  
Phase Deformation ◽  
Metamorphic Core

Mara Lake, British Columbia straddles the boundary between the Monashee Group on the east and the Mount Ida Group on the west. Correlation of units across the southern end of Mara Lake indicates lithologic continuity between parts of the groups. Both groups have experienced four phases of deformation. Phases one and two are tight and recumbent, trending to the north and to the west, respectively. Phases three and four are open to closed and upright, trending northwest and northeast, respectively. Second-phase deformation includes large-scale tectonic slides that separate areas of consistent vergence. Slide surfaces are folded by third- and fourth-phase structures and outline domal outcrop patterns. Metamorphic grade increases from north to south along the west side of Mara Lake. Calc-silicate reactions involving the formation of diopside are characteristic. From west to east increasing grade is evident in the reaction of muscovite + quartz producing sillimanite + K-feldspar + water. These prograde reactions are related to relative position in the second-phase structure. The highest grade is located near the lowest slide surface. Greenschist conditions accompanied phase-three deformation. Fourth phase is characterized by hydrothermal alteration, brittle fracturing, and local faulting. First-phase deformation appears to be pre-Late Triassic whereas second and third phases are post-Late Triassic and pre-Cretaceous. The fourth phase is part of a regional Tertiary event. The third folding event is correlated with the development of the Chase antiform and the second-phase folding is related to the pervasive east–west fabric of the Shuswap Complex. The timing of these events indicates that the metamorphic core zone of the eastern Cordillera was relatively rigid during the late Mesozoic foreland thrust development. Ductile deformation significantly preceded thrusting and developed a fabric almost at right angles to the trend of the thrust belt.

The record of jökulhlaups from Summit Lake, northwestern British Columbia

1993 ◽  
Vol 30 (3) ◽  
pp. 499-508 ◽  
Author(s):  
William H. Mathews ◽  
John J. Clague
Keyword(s):  
British Columbia ◽  
Water Level ◽  
River Valley ◽  
Water Level Fluctuations ◽  
Salmon River ◽  
The Road ◽  
The North ◽  
Large Numbers ◽  
Dammed Lake ◽  
Effective Seal

Summit Lake, which is impounded by Salmon Glacier, is the largest self-draining, ice-dammed lake in Canada. Until 1961, it contained few icebergs and was stable, overflowing to the north into me Bowser River valley. The first jökulhlaup occurred in December 1961, after a lengthy period of thinning and retreat of Salmon Glacier, when a subglacial runnel developed in the weakened ice dam, allowing the lake to drain suddenly. This flood and two others in 1965 and 1967 caused major damage to the road system in the Salmon River valley south of the lake. Since 1965, with three exceptions, Summit Lake has drained annually; minor floods along Salmon River in 1966, 1969, and 1973 may record partial drainings of the lake, although other explanations are possible. Jökulhlaups in recent years have been smaller and have occurred earlier in the year than most of the early floods. Rapid water-level fluctuations associated with the annual emptying and refilling of Summit Lake have generated large numbers of icebergs, derived from the Salmon Glacier dam; these icebergs presently choke the surface of the lake. The present jökulhlaup cycle is likely to continue either until the glacier readvances or until it retreats to the point that it no longer forms an effective seal.

Quaternary Geology, Columbia River Valley, British Columbia

1968 ◽  
Author(s):  
R J Fulton
Keyword(s):  
British Columbia ◽  
Columbia River ◽  
River Valley ◽  
Quaternary Geology

Underground Houses on the British Columbian Coast

1944 ◽  
Vol 9 (3) ◽  
pp. 265-270 ◽  
Author(s):  
H. G. Barnett
Keyword(s):  
British Columbia ◽  
Bering Sea ◽  
Pacific Coast ◽  
River Valley ◽  
Fraser River ◽  
Northern California ◽  
The South ◽  
The North ◽  
The Pacific ◽  
The Way

Semi-Subterranean houses with an entrance through the roof are a well known feature of the interior of British Columbia, having been described for the Thompson, the Chilcotin, the Shuswap and others of the upper Fraser River valley. They have, in fact, an even wider distribution east of the Coast and Cascade Ranges, extending south over the Plateau and into northern California. Although this type of dwelling existed among the Aleuts, it appears that the coastal people to the south of them, even in Alaska, were either unfamiliar with the pattern or rejected it in favor of others. Sporadically, along the Pacific Coast all the way from California to Bering Sea, house floors were excavated to varying depths, sometimes even to two levels; but, everywhere, the houses characteristically lack the roof entrance and, except for sweathouses in the south and Bering Sea Eskimo dwellings in the north, even the idea of an earth covering is absent. In view of this fundamental divergence, it is interesting that subterranean structures do appear in several places on the coast of British Columbia.

Geology of the Nemo Lakes belt, northern Valhalla Range, southeast British Columbia

1981 ◽  
Vol 18 (5) ◽  
pp. 944-958 ◽  
Author(s):  
Randall R. Parrish
Keyword(s):  
British Columbia ◽  
Large Scale ◽  
Phase 1 ◽  
Normal Fault ◽  
Columbia River ◽  
Ultramafic Rocks ◽  
Phase 2 ◽  
Metasedimentary Rocks ◽  
The North ◽  
Gneiss Complex

High-grade metasedimentary rocks, probably of both early Paleozoic and late Paleozoic – Triassic ages, underlie an area termed the Nemo Lakes belt between Slocan and Arrow Lakes in the northern Valhalla Range, southeastern British Columbia. The rocks have experienced two possibly related periods of major folding. Phase 1, accompanied and outlasted by metamorphism at P–T conditions of 5.0–6.8 kbar (500–680 MPa) and 630–680 °C, involved emplacement of ultramafic rocks, major faulting, and folding. Phase 2 involved large-scale inclined to upright folds which were dominantly south-verging, deforming the phase 1 fabric. Both phases probably occurred in the Middle to Late Jurassic, as part of the Columbian Orogeny.Rocks lithologically and structurally similar to those of the Nemo Lakes belt are found across the Rodd Creek fault near the Columbia River and extend the general continuity of the belt into the Shuswap metamorphic complex.Plutonic rocks, some of which bracket the movement on the Rodd Creek fault, the southern extension of the Columbia River fault zone, range in age from Middle Jurassic to EoceneIn the valley of Slocan Lake, a major normal fault is postulated on structural and metamorphic grounds and may be related to the north–south arching of the Valhalla gneiss complex. It is suggested that this arching and uplift, which followed phase 2 deformation, produced both the fault and a zone of cataclasis on the eastern side of the complex, and gave rise to its domal shape.

40Ar/39Ar thermochronology of the Thor-Odin – Pinnacles area, southeastern British Columbia: tectonic implications of cooling and exhumation patterns

2016 ◽  
Vol 53 (10) ◽  
pp. 993-1009 ◽  
Author(s):  
D. van Rooyen ◽  
S.D. Carr
Keyword(s):  
British Columbia ◽  
Shear Zone ◽  
Late Cretaceous ◽  
Columbia River ◽  
Metamorphic Rocks ◽  
Structural Level ◽  
High Grade ◽  
Extensional Deformation ◽  
Structural Levels ◽  
Upper Boundary

The Thor-Odin dome is a basement-cored tectonothermal culmination in southern British Columbia, containing high-grade metamorphic rocks that were polydeformed during the Cordilleran orogenesis. A north–south 40Ar/39Ar thermochronology transect was carried out throughout a ∼7 km thick tilted section in the Thor-Odin dome and structurally overlying rocks to construct thermochronological histories using existing U–Pb geochronology data with new 40Ar/39Ar data and to determine the nature of the boundary between the dome and overlying rocks at Cariboo Alp. Hornblende cooling dates are ∼62–58 Ma at the highest structural level, ∼57–55 Ma in the middle, and ∼57–53 Ma at Cariboo Alp on the upper boundary of the dome. Muscovite and biotite cooling dates are ∼53–50.5 Ma; identical throughout the dome, margin, and overlying panel. The Cariboo Alp area separating the Thor-Odin dome from overlying rocks did not accommodate major post-cooling extensional deformation; rather, it is a Late Cretaceous to Paleocene compressional shear zone. These domains cooled at different rates from >700 to ca. 300 °C, with upper structural levels cooling at rates of ca. 20 °C/Ma and the lowest levels at rates in excess of 120 °C/Ma. All levels passed through the closure temperature for argon in biotite (here calculated to be 320–330 °C) together at ca. 52–51 Ma. Differential cooling rates are the result of interaction between northeast-directed compressional transport of rocks towards the foreland of the orogen overlapping with activity on the Columbia River fault zone, reflecting crustal-scale extension that reached a peak in the Eocene.

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