Showing papers in "Canadian Journal of Earth Sciences in 1970"

Strain variation in shear belts

Abstract: In rocks deformed by natural orogenic processes it is usual to find that the finite strain state varies from locality to locality. In some deformed rocks high strain states are localized within app...

Isostatic response to loading of the crust in Canada

Abstract: A smoothed free air anomaly map of Canada indicates that the central part of the region occupied by the Laurentide Ice Sheet is over-compensated. Due to the close association of the free air gravity, the apparent crustal warping, the time of deglaciation, and the congruence of the gravity anomalies and the Wisconsin Glaciation, it is concluded that the over-compensation is due to incomplete recovery of the lithosphere from the displacement caused by the Pleistocene ice loads. The amplitude of the anomalies, about –50 milligals, suggests that a substantial amount of uplift has yet to occur and that the relaxation time of crustal warping is of the order of 10 000 to 20 000 y.The profile of the ground surface at the edge of a continental ice sheet on an elastic lithosphere is assessed using a value of the flexural parameter of the lithosphere calculated from gravity and deformation studies in the Interior Plains. The conclusions are: (a) a purely elastic forebulge is not likely to reach an amplitude of more ...

The Mid-Atlantic Ridge at 45° N. XIV. Oxidation and magnetic properties of basalt; review and discussion

Abstract: The magnetic properties of submarine basalt procured in a traverse across the accreting margin of a lithospheric plate are reviewed. These properties are attributed to two processes. Firstly, the rapid quenching of lava in the axial zone of accretion produces dispersed titanomagnetite of very small grain-size, ranging from about 5 μm down to submicroscopic sizes. During quenching the pillow lava acquires a very intense (0.1 c.g.s. units per cm3) and stable (mean coercivity of remanence 240 Oe) remanent magnetization, with Q of the order 100. The oxidation state is initially low (FeO/Fe2O3 averages about 7) but, presumably because of rapid quenching, it is chemically unstable, and undergoes secondary oxidation, so that at a distance of 10 km in from the accreting margin the FeO/FenO3 ratio has fallen to about unity, the remanence has decreased by a factor 10, and the Curie and blocking temperatures have risen from the range 100–300 °C to the range 300–500 °C. It is suggested that these magnetic changes are...

Studies of glacial history in Arctic Canada. I. Pumice, radiocarbon dates, and differential postglacial uplift in the eastern Queen Elizabeth Islands

Abstract: Dark brown pumice has been discovered recently on raised beaches of Ellesmere and Devon Islands, and in archeological sites on Baffin Island. It is similar in appearance and chemical composition to...

Postglacial crustal movements in southwestern British Columbia and adjacent Washington state

Abstract: Records of former land–sea relationships in southwestern British Columbia and adjacent Washington State have been established in considerable detail by terrestrial and marine stratigraphy, by terrestrial and littoral landforms, and by archeological remains, aided by radiocarbon dating of shells, wood, peat, and charcoal from critical sites. These records indicate submergent conditions at the time of retreat of the Vashon ice sheet, 13 000 y ago, followed by an unusually quick emergence of several hundred feet by about 12 000 y ago. In the north-east and north of the area studied, this emergence was followed by a submergence of some hundreds of feet during the next half millennium preceding the Sumas ice advance. During and following this ice advance, land again became emergent, and during the period 9 000 to 6 000 y ago sea level stood approximately 35 ft (10 m) below the present shore in some parts of the area. The shore has stood close to its present level for the last 5 500 y in all parts of the area.E...

The Precambrian geochronology of Rajasthan and Bundelkhand, northern India

Abstract: Many new age determinations are reported for the Precambrian of Rajasthan and Bundelkhand in northern peninsular India. All are by Rb–Sr and mostly from total-rock analyses. They show that the olde...

Heat transfer during solidification of layered intrusions. I. Sheets and sills

Abstract: With the advent of crystal settling in a solidifying igneous intrusion, the roof contact of the intrusion may be continuously subjected to temperatures approaching those of the magma itself. This c...

Recent coastal submergence of the Maritime Provinces, Canada

Abstract: Hydrographic, archeologic, and geologic evidence indicates that for the last 4000 y the Maritime Provinces have been submerging three to five times faster than the 6 cm/century rate of eustatic ris...

An alkaline rock province linking Europe and North America

Abstract: Lower Paleozoic carbonatites associated with the St. Lawrence graben system are correlated with carbonatites of similar age (565 m.y.) in Greenland and Scandinavia. The correlation is well establis...

The pollen stratigraphy of a dated section of Late Pleistocene lake sediment from central Alberta

Abstract: A 5.5 m section of limnic sediment from Lofty Lake in the Mixedwood Section of the Boreal Forest in central Alberta has yielded the first complete Late Pleistocene pollen stratigraphy for the provi...

Computer experiments on mechanics of finite amplitude folds

Abstract: Computer simulation of the time-dependent deformations of layered viscous solids serves as the basis of a study of the mechanics of large-amplitude folds. Several models of a single viscous layer embedded in a less viscous matrix and a model of an infinite stack of layers of alternating viscosity have been studied. This study treats the plane finite deformations of the models as a series of small incremental deformations. The velocity fields of the incremental problems are found using the finite element method. With the single-layer models, the contrast of viscosity between the layer and matrix strongly influences the geometry of folds at the dominant wavelength. Fold geometries vary from concentric for large viscosity contrasts to nearly similar for low contrasts. In each model, the patterns given by directions perpendicular to the principal axes of maximum total compressive strain closely resemble axial-plane foliations in natural folds. Published fabric data for calcite-twin lamellae and quartz-deforma...

Thermal conductivity of frozen soils

Abstract: Thermal conductivity measurements of two frozen soils, Leda clay and Sudbury silty clay, taken at temperatures between 0 and −22 °C by means of a thermal probe and a transient heat flow technique, ...

The Mid-Atlantic Ridge near 45 °N. VI. Remanent intensity, susceptibility, and iron content of dredged samples

Abstract: Results from 27 dredge hauls (75 samples) spaced from 150 km west to 70 km east of the Median Valley of the Mid-Atlantic Ridge at about 45 °N are reported. Basalt is the most common rock type. The basalts have a mean remanent intensity of 92 × 10−4 and a mean susceptibility of 0.9 × 10−4 cgs cm−3. The remanence varies with distance from the axis, samples from the Median Valley (mean 574 × 10−4) being ten times more magnetic than samples at a greater distance. Most of this decrease of intensity occurs within a few kilometers (less than 6 km) of the central axis and within the zone of active volcanism. It is suggested that this dramatic drop in intensity is caused by viscous decay enhanced by thermal cycling or by chemical change in the narrow volcanic axial zone.Certain other properties of the basalts vary with distance; the blocking temperatures and stability (versus a.f. demagnetization) increase, and the ratio FeO/Fe2O3 decreases with distance. These changes are most marked at the inner slopes of the Cr...

The Mid-Atlantic Ridge near 45° N. XI. Seismic velocity, density, and layering of the crust

Abstract: Compressional wave velocities at pressures to 1000 kg/cm2 and densities are given for a representative suite of rocks selected from 42 dredge hauls on the Mid-Atlantic Ridge near 45° N. The spectrum of rocks studied includes vesicular and massive basalts, metabasalts, meta-gabbros, and serpentinites. Evidence is presented for block faulting of an originally continuously layered crust of vesicular basalt and massive basalt underlain by a metamorphosed basalt and gabbro sequence. A study of the velocities of these layers at in situ pressures shows that they correlate well with the seismic layering of the oceanic crust. The velocity of the massive basalt layer is in agreement with that reported for layer 2. The underlying layer, consisting of low-to-medium grade metamorphosed basalts and gabbros (greenstones and greenschists) exhibits higher velocities. None of these exceed 6 km/s but it is suspected that these rocks at greater burial depths will exhibit velocities comparable to those of layer 3. The occurre...

Paleomagnetism and correlation of some Middle Keweenawan rocks, Lake Superior

Abstract: Paleomagnetic results from the Lake Superior region appear to indicate that Middle Keweenawan formations or magnetic divisions within formations can be correlated on the basis of magnetic polarity....

Pentlandite phase relations in the Fe–Ni–S system and notes on the monosulfide solid solution

Abstract: A curve relating composition of synthetic pentlandite with interplanar spacing was determined experimentally as follows: d115 = 1.9407 – 0.0023x + 0.0077x2, where x represents the iron to nickel we...

Lateral mixing of the Liard and Mackenzie rivers downstream from their confluence

Abstract: Data relating to the mixing rate of the Liard and Mackenzie Rivers were collected in June 1968, for a distance of 300 miles (~482.8 km) downstream from their confluence. Samples were collected from...

Volcanism and its relationship to recent crustal movements in the Canadian Cordillera

Abstract: "Compressive" folding, thrusting, and transcurrent fault movement have occurred during late Tertiary and Recent times in parts of southeastern Alaska and southern Yukon west of a line joining the Denali, Queen Charlotte, and San Andreas fault systems. East of this line "compressive" deformation and transcurrent faulting ceased in the Canadian Cordillera by late Eocene time or earlier, and was followed by a period of crustal relaxation that has continued to the present. The onset of relaxation was accompanied by acid volcanism, block faulting, and high-level intrusion of granitic plutons and dike swarms. Explosive eruptions that characterized early Tertiary volcanism were followed in late Miocene and Pliocene times by quiet outpouring of plateau basalt in central British Columbia and later, during Pleistocene and Recent times, by construction of nearly 150 cinder cones and strata volcanoes. Most of these young volcanic centers are confined to two north-south trending belts and an east–west belt offsetting ...

Metamorphic framework and plutonic styles in the Prince Rupert region of the Central Coast Mountains, British Columbia

Abstract: The metamorphic framework in Prince Rupert – Skeena region of the Coast Mountains of British Columbia comprises schist, gneiss, and migmatite displaying progressive regional metamorphism that overlaps the Barrovian and Idahoan Facies Series. Although part of the circum-Pacific metamorphic zone, the Coast Mountain metamorphic belt is apparently not paired. Plutonic rocks, which were probably an integral part of the early metamorphic framework, have apparently been mobilized during metamorphism and continued to move out of their original environment while metamorphism waned, some even deforming the pre-existing fabric.Within the framework, four main plutonic styles have been recognized:1) Autochthonous, migmatitic, plutonic complexes.2) Para-autochthonous, steep-walled (tadpole) plutons.3) Para-autochthonous, tongue-shaped, recumbent plutons.4) Allochthonous, intrusive plutons.Quartz diorite and granodiorite are the most common plutonic rocks. Diorite and quartz monzonite are less common: gabbro and especia...

A new analysis of geomagnetic depth-sounding data from western Canada

Abstract: Time varying geomagnetic fields observed in southern British Columbia and Alberta are analyzed using optimum "transfer function" techniques for periods from 4 to 240 min. Estimates of the frequency and spatial dependence of the "coast effect" are obtained. Inland anomalies are delineated and attributed to variations in conductivity in the upper-to-middle crust coupled with an abrupt east–west transition in deeper conductivity. Regional attenuation of the uncorrelated portion of the vertical magnetic component is indicative of high conductivity near the crust mantle transition zone under the western part of the Cordillera. The conclusion is in agreement with magnetotelluric observations and other geophysical data.

Post-glacial uplift and substrate age at Cape Henrietta Maria, southeastern Hudson Bay, Canada

Abstract: As a basis for future ecological and biogeographical studies, the post-glacial emergence history of Cape Henrietta Maria was required. This was obtained by fitting a post-glacial emergence curve to a number of radiocarbon dated marine strandlines of known elevation. Analysis shows that the elevation of lower samples is critical for a reasonable prediction of higher relative sea levels. This emergence curve suggests that during the last 1000 y uplift has been about 1.2 m per century. Extrapolation to likely dates of deglaciation (8000−7000 BP) indicates a maximum marine inundation of > 300 m. The current rate of uplift, and the hypothetical elevation of the marine limit are the highest estimations to date for eastern and arctic Canada and support the hypothesis that a center of uplift and ice-loading is situated in southeastern Hudson Bay and northern James Bay. The derived emergence curve was used to construct an isochrone map of Polar Bear Park, in eastern northern Ontario. This map provides the basis fo...

Present and postglacial rates of uplift for glaciated northern and eastern North America derived from postglacial uplift curves

Abstract: Average rates of postglacial uplift reach a maximum value of nearly 4 m 100 y−1 over southeastern Hudson Bay, and another high cell, with rates of about 2.5 m 100 y−1, lies between Bathurst Inlet and Southampton Island. Current rates of uplift are underestimated if exponential curves are fitted solely to dated raised marine deposits without considering the amount of future recovery. Rates of rebound are, instead, derived from A/t where A is uplift in the first 1000 y since deglaciation, and t is time since deglaciation. For the northwest margin of the former ice sheet coefficients of determination for rate of uplift, at specific times, as a function of distance are . Maps of rates of uplift for northern and eastern North America are presented for 8000 y B.P., 6000 y B.P. and the present day. They reveal the existence of three uplift centers and show that rates of uplift declined from a maximum of 10 to 12 m 100 y−1, immediately following deglaciation, to a current maximum of about 1.3 m 100 y−1. Agreement...

Rb–Sr Geochronology of the Hida metamorphic belt, Japan

Abstract: Rb–Sr whole-rock and mineral isochron ages have been determined for metamorphic and granitic rocks of the Hida metamorphic belt. The results indicate that an extensive metamorphic event together wi...

The Mid-Atlantic ridge near 45° N. VII. Magnetic properties and opaque mineralogy of dredged samples

Abstract: Measurements of the magnetic properties, paleomagnetic field intensity, and the inferred paleomagnetic field polarity have been made using fine grained basalt and coarser grained rock samples dredged from the mid-Atlantic ridge near 45° N and supplied by the Geological Survey of Canada. The opaque mineralogy of the samples was studied by microscope, Curie point, and X-ray diffraction techniques. The natural remanent magnetization of the basalt is of the order of 5 to 10 × 10−3 e.m.u./cm3 with some values from the center of the median valley reaching 10−1 e.m.u./cm3. Magnetic anomalies over the ridge can be accounted for by the remanent magnetization of a few hundred meters of this basalt. The coarse grained rocks were relatively weakly magnetized, and while they contribute little to the magnetic anomalies, their diverse character suggests that the major portion of the oceanic crust, below a thin veneer of fine grained basalt, has differentiated into a complex structure.

Hypsithermal range extension of white pine (Pinus strobus L.) in Quebec, Canada

Abstract: Fossil wood, cones, and leaves of white pine (Pinus strobus L.) were discovered at Val St. Gilles, Quebec, some 60 miles (~96.6 km) north of the present distribution limit of this species. The fossils were buried under several feet of peat, and were dated at 5030 ± 130 (GSC-585) radiocarbon years before present. In the pollen diagram from this peat exposure a white pine pollen maximum coincides with the stratigraphic unit in which the fossil pine wood was found. This discovery indicates that white pine was growing well north of its present distribution limit during the Holocene hypsithermal interval, when climatic conditions were more favorable in this region than at present.

Crystal growth and nucleation in two large diabase dikes

Abstract: The total number of nuclei, Z, of a single phase formed in a unit volume of a crystallizing magma at the distance y from the contact of a semi-infinite intrusion iswhere n is a numerical constant determined by growth controlling process during the nucleation period and the value of m in the expression assumed for the nucleation rate, JThe observed variation of Z for clinopyroxene and plagioclase from the contact towards the center of two large dikes appears to follow this relation. In the 106 m wide Kigaviarluk olivine tholeiite dike the value of n is significantly greater for the clinopyroxene (−2.2) than the plagioclase (−0.84). In the 60 m Grenville dike, a quartz tholeiite, the n value (−1.5) is the same for both minerals. The growth-controlling mechanisms of plagioclase and clinopyroxene appears to be sensitive to the bulk composition of the magma from which it is crystallizing.

Neoglacial fluctuations of the Natazhat and Klutlan Glaciers, Yukon Territory, Canada

Abstract: The Natazhat and Klutlan Glaciers are surging valley glaciers whose present termini are located at the northern edge of the St. Elias Mountains. Both glaciers have massive ice-cored Neoglacial morainal complexes extending down-valley from their ice termini. At least six separate Neoglacial moraines adjacent the Klutlan Glacier and four adjacent the Natazhat Glacier have been identified from changes in the geomorphic, pedologic, limnologic, vegetational, dendrochronologic, and lichenometric characteristics across the morainal complexes. Dating of the individual moraines by lichenometry, dendrochronology, and 14C implies that most were constructed within the last 550 years, although both glaciers have been relatively inactive near their termini since 1947.Stratigraphy and 14C dates suggest that the initial Neoglacial advance of the Natazhat Glacier near its Neoglacial maximum occurred ca. 3300 B.P. and that of the Klutlan Glacier ca. 1520 B.P.Intervals during which the glaciers constructed a number of morai...

Status of the Jurassic in the Canadian Cordillera of British Columbia, Alberta, and southern Yukon

Abstract: Jurassic index fossils of the Canadian Cordillera indicate the presence of some zones of most Jurassic stages. In this report the more important localities are listed, the source of information, published and unpublished, is indicated, and an up-dated correlation chart is presented. The importance of tectonic events and their effect on the completeness of the Jurassic fossil record and on the Jurassic paleogeography are stressed.

The analcite-bearing volcanic rocks of the Crowsnest Formation, Alberta

Abstract: The lower Cretaceous Crowsnest Formation of the Crowsnest Pass area, Alberta, is predominantly trachytic, but some sodic, analcite-rich, rocks occur. It consists of bedded pyroclastic and epiclastic material with minor flows and dikes. Most of the volcanism appears to have been explosive in nature. Almost all the igneous material is porphyry tic; nearly all the phenocrysts are zoned, and evidence of resorption is common. Sanidine phenocrysts show evidence of repeated growth and solution with as many as 60 cycles per crystal. The primary, igneous, analcite phenocrysts of the analcite phonolites and blairmorites crystallized at depth, and were preserved by rapid vertical transport and quenching at the surface. In many cases, however, partial or complete decomposition of the crystals occurred, and thermal discoloration of the analcite can be reproduced in the laboratory.

Petrofabrics: A critical review

Abstract: Petrofabric contributions are here classified into seven categories, namely: (1) descriptive techniques; (2) kinematic analyses; (3) geometric analyses of folds; (4) absolute strain analyses; (5) s...