Megalineament in southeastern Alaska marks southwest edge of Coast Range batholithic complex

1978 ◽  
Vol 15 (11) ◽  
pp. 1763-1772 ◽  
Author(s):  
David A. Brew ◽  
Arthur B. Ford
Keyword(s):  
British Columbia ◽  
Structural Feature ◽  
Surface Expression ◽  
Coast Range ◽  
Glacial Erosion ◽  
Near Surface ◽  
Intrusive Rocks ◽  
Topographic Depressions ◽  
Nearly Continuous

The Coast Range megalineament is a prominent, nearly continuous topographic and structural feature that extends southeastward about 550 km (330 mi) from its junction with the Chatham Strait – Lynn Canal fault at Point Sherman to Tongass Passage near the mouth of Pearse Canal where it leaves southeastern Alaska. It probably extends still further southeastward into British Columbia along Work Channel and Chatham Sound – Grenville Channel.The megalineament is a zone a few hundred metres to 10 km (6 mi) wide in which closely spaced joints, foliation, compositional layering, and small faults define the megalineament trend. The zone usually coincides with topographic depressions apparently caused by selective fluvial and glacial erosion of the less resistant rocks of the zone.Studies in the Juneau, Endicott Arm, and Behm Canal areas indicate that the megalineament (1) is locally the site of lateral and (or) vertical separations of no greater than several kilometres; (2) does not mark a major structural or metamorphic discontinuity in the near-surface rocks; (3) may be located near a pre-metamorphic and pre-intrusive discontinuity; (4) is consistently associated with and parallel to steep gradients in both the gravity and aeromagnetic fields; and (5) probably is the surface expression of the western contact, at depth, of the intrusive rocks and gneisses of the Coast Range batholithic complex with the schists to the southwest.

STRUCTURE, STRATIGRAPHY, AND PALEONTOLOGY OF AN UPPER TRIASSIC SECTION ON THE WEST COAST OF BRITISH COLUMBIA

1965 ◽  
Vol 2 (5) ◽  
pp. 442-484 ◽  
Author(s):  
Donald Carlisle ◽  
Takeo Susuki
Keyword(s):  
British Columbia ◽  
Structural Information ◽  
Pillow Lava ◽  
Middle Part ◽  
Upper Triassic ◽  
Coast Range ◽  
Thermal Alteration ◽  
The West ◽  
Coastal British Columbia ◽  
Sedimentary Unit

The highly deformed section at Open Bay is one of the few good exposures of a thick sedimentary unit within the prebatholithic rocks along coastal British Columbia. It provides new structural information relating to emplacement of a part of the Coast Range batholith and it contains an important Upper Triassic fauna unusually well represented. Structural and paleontological analyses are mutually supporting and are purposely combined in one paper.Thirteen ammonite genera from 14 localities clearly substantiate McLearn's tentative assignment to the Tropites subbullatus zone (Upper Karnian) and suggest a restriction to the T. dilleri subzone as defined in northern California.Contrary to an earlier view, the beds are lithologically similar across the whole bay except for variations in the intensity of deformation and thermal alteration. Their contact with slightly older relatively undeformed flows is apparently a zone of dislocation. Stratigraphic thicknesses cannot be measured with confidence, and subdivision into "Marble Bay Formation" and "Open Bay Group" cannot be accepted. Open Bay Formation is redefined to include all the folded marble and interbedded pillow lava at Open Bay. Lithologic and biostratigraphic correlation is suggested with the lower middle part of the Quatsino Formation on Iron River, 24 miles to the southwest. Basalt flows and pillowed volcanics west of Open Bay are correlated with the Texada Formation within the Karmutsen Group.The predominant folding is shown to precede, accompany, and follow intrusion of numerous andesitic pods and to precede emplacement of quartz diorite of the batholith. Structural asymmetry is shown to have originated through gentle cross-folding and emplacement of minor intrusives during deformation.

III.—Recent Observations on the Glaciation of British Columbia and Adjacent Regions

1888 ◽  
Vol 5 (8) ◽  
pp. 347-350 ◽  
Author(s):  
Geo. M. Dawson
Keyword(s):  
British Columbia ◽  
Glacial Period ◽  
Coast Range ◽  
Coast Mountains ◽  
One Stage ◽  
Queen Charlotte Islands ◽  
Glacier Ice ◽  
Inland Ice ◽  
Great Valley ◽  
The U.S

Previous observations in British Columbia have shown that at one stage in the Glacial period—that of maximum glaciation—a great confluent ice-mass has occupied the region which may be named the Interior Plateau, between the Coast Mountains and Gold and Eocky Mountain Kanges. From the 55th to the 49th parallel this great glacier has left traces of its general southward or southeastward movement, which are distinct from those of subsequent local glaciers. The southern extensions or terminations of this confluent glacier, in Washington and Idaho Territories, have quite recently been examined by Mr. Bailley Willis and Prof. T. C. Chamberlin, of the U.S. Geological Survey. There is, further, evidence to show that this inland-ice flowed also, by transverse valleys and gaps, across the Coast Range, and that the fiords of the coast were thus deeply filled with glacier-ice which, supplemented by that originating on the Coast Range itself, buried the entire great valley which separates Vancouver Island from the mainland and discharged seaward round both ends of the island. Further north, the glacier extending from the mainland coast touched the northern shores of the Queen Charlotte Islands.

scholarly journals VII.—Mesozoic Volcanic Rocks of British Columbia and Chile. Relation of Volcanic and Metamorphic Rocks

1877 ◽  
Vol 4 (7) ◽  
pp. 314-317
Author(s):  
George M. Dawson
Keyword(s):  
British Columbia ◽  
South America ◽  
Volcanic Rocks ◽  
Geological Survey ◽  
Metamorphic Rocks ◽  
Coast Range ◽  
Similar Relation

In Chile and adjacent regions of South America, Mr. Darwin, in his “Geological Observations,” has described a great series of Mesozoic rocks, which he calls the “porphyritic formation,” and which shows an interesting resemblance to certain rocks in British Columbia. These I had provisionally designated in my report in connexion with the Geological Survey of Canada for 1875, as the Porphyrite series, without at the time remembering Mr. Darwin's name for the Chilian rocks. Many of Mr. Darwin's descriptions of the rocks of Chile would apply word for word to those of British Columbia, where the formation would also appear to bear a somewhat similar relation to the Cascade or Coast Range, which that of Chile does to the Cordillera.

Are There Better Disposal Methods?

2000 ◽  
Author(s):  
Hans Tammemagi
Keyword(s):  
Sustainable Development ◽  
Waste Disposal ◽  
Surface Expression ◽  
Abandoned Mines ◽  
Underground Mines ◽  
Open Pit ◽  
Near Surface ◽  
The Sustainable Development ◽  
Future Value ◽  
Deep Underground

Most of the solid waste generated by society ultimately winds up in near-surface landfills. Let us put our thinking caps firmly on, place our prejudices aside, and explore what other methods might be used to dispose of waste. We should seek, in particular, the approaches that best fulfill the three basic principles described in chapter 2. That is, we should strive to find disposal methods that are in accord with sustainable development. Existing and abandoned pits, quarries, and mines are attractive for waste disposal because a hole to contain the wastes has already been excavated. Such abandoned areas, when left unreclaimed, cannot be used for agriculture or other beneficial uses. Thus, they generally do not have significant market value and can often be obtained relatively cheaply. For these reasons, pits and quarries have been extensively used for landfills. Operating and abandoned mines, on which this section focuses, are somewhat similar to pits and quarries, though usually larger. Abandoned mines hold promise as disposal facilities because they are resource areas that have been depleted and thus have little future value. There are two basic types of mine: the open pit mine, which is effectively a large pit or hole in the ground; and the underground mine, where the mined-out openings are deep underground and there is no surface expression except for the shafts used to gain subsurface access. Because underground mines occupy minimal surface land, their use for waste disposal would be in accordance with the sustainable development principles that were advocated in chapter 2. Several European countries, with higher population densities and much smaller land mass than in North America, have long used abandoned underground mines to dispose of their rubbish. The major advantage of placing wastes deep in underground mines is that it is inherently safer than placing the wastes in a surface facility. The amount of groundwater and its flow rate decrease with depth; this fact, combined with the long transport paths back to the biosphere, minimizes the possibility that contaminants will be carried by groundwater to the surface, where they could damage the environment. The waste is contained deeper and more securely.

THE NYMPH OF CINYGMA INTEGRUM AND DESCRIPTION OF A NEW HEPTAGENINE GENUS

1933 ◽  
Vol 65 (4) ◽  
pp. 73-77 ◽  
Author(s):  
J. McDunnough
Keyword(s):  
British Columbia ◽  
Coast Range ◽  
Female Adult ◽  
Structural Details

The species, integrum Eaton, described from material collected in Washington and Oregon states, was designated by Eaton as the genotype of Cinygma. I have already (1926, Can. Ent. LVIII, 302) recorded the capture of adults of this species in the Coast range of British Columbia and at the time expressed some doubt as to whether all the species at present included in this genus were strictly congeneric. Since nymphal structures have been recognized by a number of recent workers as of great importance in furnishing distinguishing characters in the Heptagenine genera it was with considerable interest that I discovered among material collected in the Hope Mts., B. C. in 1932 by my assistant, Mr. A. N. Gartrell, a bred female adult of integrum, together with its nymphal exuvia, preserved in alcohol. A study of this exuvia soon convinced me that in the nymphal gills and mouth-parts there are excellent and in part unique structural details which should at once establish not only the validity of the genus but also its limitations and position in the group of allied genera.

The basal unconformity of the Nanaimo Group, southwestern British Columbia: a Late Cretaceous storm-swept rocky shoreline

2006 ◽  
Vol 43 (8) ◽  
pp. 1165-1181 ◽  
Author(s):  
P D Johnstone ◽  
P S Mustard ◽  
J A MacEachern
Keyword(s):  
British Columbia ◽  
Sediment Supply ◽  
Storm Activity ◽  
Fine Grained ◽  
Accommodation Space ◽  
Facies Associations ◽  
Intrusive Rocks ◽  
Coastal Cliffs ◽  
Sandstone Facies ◽  
High Sediment

The Turonian to Santonian Comox Formation forms the basal unit of the Nanaimo Group. In the southern Gulf Islands of British Columbia, the Comox Formation nonconformably overlies Devonian metavolcanic and Jurassic intrusive rocks and is interpreted to reflect a rocky foreshore reworked by waves and ultimately drowned during transgression. The nonconformity displays a relief of metres to tens of metres. Basal deposits vary in thickness, as does the facies character along the several kilometres of paleoshoreline studied. In the study area, three distinct but related environments are expressed, typical of a complex rocky shoreline with headlands and protected coves. Crudely stratified conglomerates represent gravel-dominated fans characterized by debris-flow processes, building out from local coastal cliffs and gullies directly onto the rocky shoreline. Fine-grained basal units represent shoreline environments protected from higher energy shoreline processes, presumably in small embayments. Sandstone facies associations reflect storm-dominated shoreface environments. The unusual thickness and coarseness of these shoreface intervals suggest a combination of increasing accommodation space, proximal and high sediment supply, and high frequency and energy of storm activity. This, in turn, suggests that the majority of the shoreline was exposed to the full effects of large, open-ocean storms. This interpretation differs from most previous models for the lower Nanaimo Group, which suggest that deposition occurred in more sheltered strait or bay environments.

Evidence for Regional Stream Aggradation in the Central Oregon Coast Range during the Pleistocene-Holocene Transition

1993 ◽  
Vol 40 (3) ◽  
pp. 297-308 ◽  
Author(s):  
Stephen F. Personius ◽  
Harvey M. Kelsey ◽  
Paul C. Grabau
Keyword(s):  
Wide Area ◽  
Fluvial Sediments ◽  
Coast Range ◽  
Drainage Basins ◽  
Oregon Coast Range ◽  
Oregon Coast ◽  
Fluvial Sediment ◽  
Sandy Silt ◽  
Induced Changes ◽  
Nearly Continuous

AbstractLow, nearly continuous terraces of similar age are present along streams in drainage basins that range in size from Drift Creek (190 km2) to the Umpqua River (11,800 km2) in the Oregon Coast Range. Radiocarbon ages from near the bose of fluvial sediments underlying these terraces are clustered at about 9000-11,000 14C yr B.P. Beveled bedrock surfaces (straths) that underlie the fluvial sediments are 1-8 m above summer stream levels and are present along most of the nontidal reaches of the rivers that we studied. Where exposed, the bedrock straths are overlain by 2-11 m of fluvial sediment that consists of a bottom-stratum (channel) facies of sandy pebble-cobble gravel and a top-stratum (overbank) facies of sandy silt or silt. Eight radiocarbon ages from the fluvial sediments allow correlation of the lowest continuous terrace over a wide area and thus indicate that a regional aggradation episode occurred in Coast Range drainage basins during the Pleistocene-Holocene transition. The cause of such widespread aggradation is unknown but may be related to climate-induced changes in the frequency of evacuation of colluvium from hollows, which are common in all drainage basins in the region.

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