Detailed mapping near the type area of the Cache Creek Group in southern British Columbia has led to significant changes in the distribution of Cache Creek and Nicola rocks. Much of what was called Cache Creek Group is now considered to be part of the Upper Triassic Nicola Group. Several criteria can be used to distinguish the two groups. These include: 1) lithologic differences, 2) fossil information, 3) structural style, and 4) metamorphic history. The Cache Creek Group is subdivided into three mappable, fault-bounded units and appears to be a tectonic melange over much of its extent. A deformational event produced isoclinal folds, a phyllitic foliation in some lithologies, and was accompanied by metamorphism with variable pressure-temperature conditions. Mineral assemblages support conditions from temperatures less than 250°C and pressures of 4 kb or less to transitional blueschist conditions: T = 350° C and P = 6 kb. In contrast, the Nicola Group is characterized by hydrothermal alteration and the lack of a pervasive secondary fabric. It does not have the blocks in a sheared matrix tectonostratigraphic style typical of the Cache Creek Group. The two units were brought together along the Martel Fault, probably a thrust, during late Lower or early Middle Jurassic time. Deformation and melange development in the Cache Creek Group predates this event. Distribution of Cache Creek and Nicola rocks and their relationship to each other during Upper Triassic time are still not clear. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

No description available.

Metamorphic supracrustal rocks in the Cogburn Creek area belong to the Cogburn Creek Group and the Settler Schist. These are separated by a melange zone, which has been correlated with the Shuksan thrust zone and contains Baird Metadiorite and ultramafic rocks, and intruded by the Spuzzum batholith and minor younger granodiorite. Three phases of folding are recognised in the schist units: f₁ is associated with contact metamorphism that preceded regional metamorphism, f₂ produced pervasive mica foliation and tight folds, and kinks and broad warps are associated with f₃, which was locally pervasive approaching pluton margins. Mineral assemblages indicate increasing metamorphic grade from west to east from garnet to garnet-staurolite, andesine-epidote amphibolite, staurolite-kyanite, fibrolite, and coarse sillimanite zones. Metamorphic conditions vary from 300 to 500 °C in Cogburn Creek Group rocks to 550 to 700 °C at 6 to 8 kbar for pelites in the Settler Schist. Conditions deduced for metamorphism of the ultramafic rocks are consistent with those for enclosing pelitic schists. Geochronometry indicates that the Baird Metadiorite is probably Precambrian and equivalent to the Yellow Aster Complex of the North Cascade Mountains, Washington. The Cogburn Creek Group was dated as Late Paleozoic (296 ± 58 Ma, Rb-Sr WR isochron), and is provisionally correlated with the Bridge River Group. The protolith of the Settler Schist was deposited around 210 ± 27 Ma (Rb-Sr WR isochron), and it contains 2450 ± 230 Ma detrital zircon indicating partial ultimate derivation from Precambrian basement rocks. The Spuzzum batholith was intruded at 95 to 110 Ma, before the culmination of regional metamorphism. Rb-Sr biotite dates from all units and K-Ar Hb isochron dates in the range 66 to 88 Ma are metamorphic cooling dates. The youngest intrusive rocks, granodiorite dated at 32 ± 2 Ma to 42 ± 14 Ma, postdate the regional metamorphic and intrusive event. Movement on the Shuksan Thrust is bracketed as Albian, after regional blueschist metamorphism of the Shuksan Suite in the North Cascade Mountains and before intrusion of Spuzzum batholith and regional metamorphism east of Harrison Lake. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

In this thesis, we present the first detailed, long-term seismotectonic studies of oceanic ridge-transform systems. The proximity of the Juan de Fuca plate to a network of broadband seismic stations in western North America provides a unique synergy of interesting tectonic targets, high seismicity, and recording capabilities. Our main tools are earthquake source parameters, determined by robust waveform modeling techniques, and precise earthquake locations, determined by joint epicenter relocation. Regional broadband data are used to invert for the source moment tensors of the frequent, moderate-sized (M ≥ 4) earthquakes; this analysis began 1994. We include Harvard centroid moment-tensors available since 1976 for larger (M ≥ 5) earthquakes. Two studies comprise the main part of this thesis. In the first, we determine the current tectonics of Explorer region offshore western Canada. Earthquake slip vector azimuths along the Pacific-Explorer boundary require an independent Explorer plate. We determine its rotation pole and provide a tectonic model for the plate's history over the last 2 Ma. Plate motion changes caused distributed deformation in the plate's southeast corner and caused a small piece in the southwest corner to transfer to the Pacific plate. Capture of the plate fragment indicates that preserved fragments not necessary represent entire microplates. In the second study, we investigate seismicity and source parameters along the Blanco Transform Fault Zone (BTFZ). The deformation style-- strike slip and normal faulting-- correlates well with observed changes in BTFZ's morphology. We infer that Blanco Ridge probably consists of two fault segments, that several parallel faults are active along BTFZ's west part, and that Cascadia Depression possibly is a short spreading center. The slip distribution along the BTFZ is highly variable, although seismicity could account for the full plate motion rate along the entire BTFZ. The final part is a short study where we locate an earthquake in the tectonically active Mendocino triple junction region offshore northern California using land and offshore data. The precise location may be useful as a master event for relocating other earthquakes. / Graduation date: 1999

No description available.

No description available.

Vedder Mountain can be divided into three units: the eastern sediments, the crystalline rocks and the western sediments. Both eastern and western sediments are essentially unmetamorphosed whereas the crystalline rocks include both medium grade metamorphic rocks and saussuritized dioritic intrusive rocks. The crystalline rocks are bounded by steep southeast dipping faults. White mica-amphibole and garnetiferous white mica-amphibole schists and gneisses, amphibolite, epidote amphibolite and garnet-sphene-white mica schists comprise the metamorphic rocks. The mineral assemblages are typical of the almandite-amphibolite facies of Turner and Verhoogen (1960). Foliated diorites intrude (?) the metamorphic rocks. Basic contact zones, lighter colored diorite dikes, amphibole-feldspar pegmatites and small quartz diorite bodies are thought to represent various phases of differentiation of a parent magma. Pervasive saussuritization characterizes these rocks. In structural succession, the eastern sediments are comprised of chert, granitic and volcanic pebble and cobble conglomerates with plagioclase volcanic arenite interbeds; plagioclase volcanic arenite with conglomerate interbeds near the base of the unit and argillite interbeds near the top; and micro-volcanic arenite with interbeds of plagioclase volcanic arenite, argillite, chert and siliceous argillite with scattered, impure limestone pods. In structural succession, the western sediments consist of argillite; micro-volcanic arenite; chert lenticule arenite and volcanic chert arenite breccia which contain a band of impure, cherty limestone; argillite and chert. Vulcanism produced dacite porphyries which structurally underlie the sediments. The crystalline rocks comprise a tabular body believed to have been emplaced by faulting. Small, ellipsoidal serpentinite bodies lie along the southeast bounding fault of the crystalline slice. During emplacement of the crystalline slice, it appears that the sediments were pushed aside in what has been referred to as phase I deformation. Folding in the argillaceous units was "similar" in nature but in the more competent units it was "concentric." The eastern sediments comprise a synform with near horizontal northeast trending fold axis and steep southeast dipping axial plane. The western sediments comprise a steep, southeast dipping homocline. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Glacial, stratigraphic, mineralogical, structural and palynologic studies were carried out in the Princeton coalfield, B. C. Three late Pleistocene lakes on the Tulameen River, Whipsaw Creek and Granite Creek are described for the first time. Previous workers have described the Princeton Group as being made up of three units, an upper and lower volcanic rock unit separated by a sedimentary unit. Shaw (1952) names these units; the Lower Volcanic Formation (oldest), the Allenby Formation (sediments), and the Upper Volcanic Formation (youngest). The present work indicates that the Upper Volcanic Formation is interbedded with basal Allenby Formation sediments and is transitional downward into the Lower Volcanic Formation. The revised stratigraphic sequence herein proposed is the Lower Volcanic Formation (oldest), the Upper Volcanic Formation, and the Allenby Formation (youngest). The Allenby Formation is composed of interbedded conglomerates, arkosic and tuffaceous sandstones, shale, coaly shale, coal, and minor amounts of limestone, bentonite, diatomite and ash. Except for the basal Allenby Formation sediments which apparently formed as talus accumulations, the bulk of the coarse clastic sediments were derived from a granitic terrane. The shales contain silt size grains of microcline, quartz and plagioclase similar to the coarser clastics, suggesting that they are fine grained equivalents of the coarser elastics. Evidence is presented to show that the arkosic sediments were derived from the Osprey Lake Intrusion. A section of the Allenby Formation at Vermilion Bluffs is unique in that it is composed of a basal silicified diatomite overlain by a silicified dolomitic limestone and shale. Evidence is presented to show that the sequence represents an ancient spring deposit. The Princeton coalfield consists of two structural lows, separated by a small transverse anticline. Ninety-three plant microfossil species are described and illustrated. Some of these are identical with previously described material from the Green River Formation and the Fort Union Formation of the United States, and the Burrard Formation of British Columbia. Forty species of spores and pollen are abundant in the Princeton material. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Racing River area is situated near the northern end of the Rocky Mountains of British Columbia about sixty miles south of the Yukon border. The Alaska Highway passes through the map area from mile 370 to mile 460. The area covered is about two thousand square miles. Rocks exposed in the map area range in age from Late Precambrian to Upper Cretaceous, and except for thin basic dykes which cut the basement rocks, are made up entirely of sedimentary sequences. Fourteen formations have been recognized, using earlier work by M.Y. Williams (1944) and Laudon and Chronic (1949) as a basis for the subdivisions. Units mapped are essentially rock units and do not always coincide with the Formations. The area includes the physiographic provinces of the Rocky Mountain Foothills Belt, and the Rocky Mountains proper. Topography is closely related to the underlying structures, which are comprised essentially of large thrust sheets overriding each other from the west; the planes of the faults dip towards the west at varying angles. Except close to the thrust faults, the strata in general are remarkably unfolded. Secondary tension fractures have developed, often along pre-existing dykes, and quartz and carbonate material has been introduced. The veins are in places accompanied by copper mineralization. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Vanadium is concentrated in laminated, black carbonaceous, siliceous sedimentary rocks at Menzies Bay and Quadra Island, Campbell River area, British Columbia. The vanadiferous rocks are intercalated with amygdaloidal, porphyritic basalts, andesites, and spilites, many of which are pillowform. The writer has correlated the Menzies Bay, Vancouver Island, flows with the Upper Triassic Texada formation volcanic rocks of Quadra Island. A limited petrographic study of the Texada flows in the area has indicated that pumpellyite is copious and widely distributed. Amygdaloidal greenockite is present in trace amounts. The identification of pumpellyite,regarded as amphibole by earlier writers, marks its first occurrence in British Columbia. In a detailed study of the mineralization associated with the vanadiferous sedimentary rocks, the first British Columbian occurrences were noted for tenorite, brochantite, and cyanotrichite. Malachite and bronchantite were found to be the most abundant supergene copper minerals in the laminated seams. Nearly all the supergene vanadium is present as volborthite, a hydrous copper vanadate common in the Colorado Plateau ores but formerly unknown in Canada. A blue, well-crystallized mineral, thought to be a hydrous copper sulphate, occurs in the Menzies Bay vanadiferous seams in small amounts. This mineral is believed to be a new species. Trace quantities of several other unidentified supergene minerals are present. Among these is a water-soluble vanadate with an x-ray powder pattern similar to that of fernandinite. A previously unidentified opaque material constituting as much as 40 per cent of the laminated rocks has been recognized as an inorganic, volatile carbon substance containing copper and traces of vanadium. The carbonaceous matter is largely epigenetic in the Menzies Bay seams and syngenetic in the Quadra Island sediment. X-ray powder photographs and diffractograms, semi-quantitative spectrograph analyses, and polished thin section studies have delimited the primary vanadium source to the carbonaceous substance. In conjunction with the vanadium problem, an x-ray powder diffraction study was carried out on many type copper and vanadium minerals. Partially the result of this study is an appendix consisting of a compilation of all the known non-uraniferous vanadium minerals. The strongest x-ray powder lines are listed for most of these minerals. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate