bluuebunny/crossref_metadata_2025 huggingface dataset:
Nouvel impact météoritique fossile? La structure semi-circulaire de Charlevoix
Authors: Rondot Jehan
Published: April 2011

The Charlevoix semi-circular structure, located 100 km northeast of Quebec City, possesses a rim 54 km in diameter, a ring-shaped graben with outcrops of Ordovician limestone, and an inner part flat or slightly undulating with a diameter of 32 km, in the middle of which rises Mont des Eboulements.This inner part is very fractured, and contains shatter cones and red and green breccias with aphanitic components. In the central part of the structure the rocks contain small veinlets and irregular masses of pseudotachylite, and the minerals display deformation features typical of rocks subjected to a violent shock. Quartz and feldspar alteration have produced an amorphous white substance. Heterogeneous breccias and fused rocks are visible in one outcrop and in blocks left by glacial erosion.This structure resembles other circular structures in Quebec, particularly those of West Clearwater Lake and Lakes Manicouagan and Mouchalagan. A volcanic origin is suggested by its location on the margin of the St. Lawrence Valley tectonic system, but the rapidity of the event and the violence of the shock reminds one rather of a meteorite origin.
A short note on the depositional shape of the sand bodies comprising the discontinuous part of the Halfway Formation, British Columbia
Authors: Mothersill John S.
Published: April 2011

The discontinuous part of the Triassic Halfway Formation, lying northeast of and separate from the continuous part of the formation northeast of Fort St. John, consists of two parallel, extensive, south-east-trending, calcareous sand bodies. These probably originated as longshore bars and barrier beaches on a gentle basinward slope during pauses in the northeastern transgression of the Triassic Sea.
Preliminary Rb–Sr geochronology of the Rice Lake – Beresford Lake area, southeastern Manitoba
Authors: Turek A. , Peterman Z. E.
Published: April 2011

A Rb–Sr geochronologic study of rocks of the Rice Lake – Beresford Lake area, southeastern Manitoba, shows that gold-quartz veins containing sericite and fuchsite were emplaced at 2720 ± 185 m.y. ago (λ87Rb = 1.39 × 10−11 yr−1). The mineralization postdates, and thus provides a minimum age for, the Rice Lake Group as well as for the successively younger intrusive basic rocks, quartz diorite plutons, and the San Antonio Formation. A whole-rock isochron for the potassic granite that lies north of the greenstones indicates an age of 2550 ± 80 m.y., with an initial 87Sr/86Sr of 0.7031 ± 0.0021, which we also consider as the age of regional metamorphism. This is in agreement with a metamorphic age of 2490 ± 90 m.y., as registered by phyllites from the Rice Lake Group. The gneisses and granites that lie south of the greenstone belt are older than 2630 m.y., as determined by a cross-cutting pegmatite. Because the northern granite is younger than the gold-quartz veins, extensive prospecting of the northern granite for gold-quartz mineralization is not likely to be fruitful unless there was a still younger, but presently unrecognized, period of mineralization.
Ages of carbonatites and other alkaline rocks in Quebec
Authors: Doig Ronald , Barton Jr. Jackson M.
Published: April 2011

Potassium-argon ages have been determined for alkaline rocks, including carbonatites, from some fifteen localities in Quebec. Nine centers of intrusion, including two previously documented localities, yield ages in the range 400 to 600 million years. All but two of these are located on or very near the northern boundary fault of the St. Lawrence graben system. Included in this group are four carbonatites with remarkably similar ages of intrusion (565 m.y.). The existence of this widespread coeval igneous activity along a 1200-mile segment of the lowland area and its westward extension supports the hypothesis that the St. Lawrence graben is a continuous structure, and indicates that the system has been active for at least 600 million years.
The Cowichan Ice tongue, Vancouver Island
Authors: Halstead E. Carl
Published: April 2011

The sequence of late glacial deposits within Cowichan Valley and on Saanich Peninsula, Vancouver Island, British Columbia, suggests the existence of an ice tongue that occupied Cowichan Valley and extended eastward to Saanich Peninsula prior to the merging with and being overridden by Cordilleran ice of the last major glaciation. Following the maximum advance of Cordilleran ice, continuous melting and downwasting prevailed, but before deglaciation was complete, remnant ice in Cowichan Valley was rejuvenated. Similar glacio-climatic events have been recognized elsewhere in the Strait of Georgia, and are named the Evans Creek Stade, the Vashon Stade, and the Sumas Stade of the Fraser glaciation. The writer tentatively applies these names to the events on Vancouver Island.
Chemical and modal analyses of some Upper Cretaceous and Paleocene bentonites from western Alberta
Authors: Lerbekmo J. F.
Published: April 2011

Twenty-two Upper Cretaceous (Brazeau Formation) and 9 Paleocene (Paskapoo Formation) bentonites from the Foothills of the Rocky Mountains in western Alberta were chemically analyzed by X-ray fluorescence. Petrographic modal analyses were made of the coarse fractions of 11 of the Upper Cretaceous bentonites to compare chemical and mineralogical compositions.Following modal classification schemes of igneous petrologists, the original ashes were predominantly rhyodacites but ranged from dacites to rhyolites. A trend toward increasing acidity is indicated in Late Cretaceous time, reaching a maximum near the Cretaceous-Tertiary boundary.The elemental composition of the bentonites shows no close quantitative relationship to the composition of the coarse crystal fraction. Alteration of the ashes to bentonites has resulted in preferential loss of silica over alumina, and of sodium over potassium and calcium. The chemical composition of the bentonite as a whole is controlled largely by the composition of the dominant clay mineral, montmorillonite, but original differences in composition between ashes are preserved to some degree.
On the Early Cambrian age of two late orogenic granites from. west-central Ahaggar (Algerian Sahara)
Authors: Boissonnas J. , Borsi S. , Ferrara G. , Fabre J. , Fabries J. , Gravelle M.
Published: April 2011

The Pharusian belt of west-central Ahaggar belongs to the 'basement complex' underlying the Paleozoic and later sediments of the Sahara. This paper reports and discusses the Rb–Sr ages obtained on total rocks and minerals from two granitic stocks of the belt: the Tioueiine and Iskel intrusions.Both plutons gave good whole-rock isochrons, which show that the systems were closed 560 ± 40 m.y. ago with respect to Rb and Sr. This is, most probably, the age of crystallization. Three of the four values obtained on biotites are somewhat lower and scattered in the range 502–526 m.y. The discrepancies are probably due to deuteric reactions or incipient weathering. They can be ascribed neither to the loss of 87Sr during the cooling down of the granites, nor to rejuvenation by some later thermal or tectonic event.These studies confirm previous results of random sampling in Ahaggar and prove that large-scale igneous activity took place during the Early Cambrian Epoch. Knowing from field data that the Tioueiine and Iskel are late orogenic granites, it must be concluded that the Pharusian orogeny came to an end at that time.Such a result contradicts early assumptions, made in the field, of a middle Precambrian age for the Pharusian orogeny. It gives further weight to modern ideas concerning the 700–500 m.y. events in Africa, and it leaves time for erosion to create the Saharian platform before the deposition of the first Paleozoic sandstones.
Some comments on the differentiation of the Dundonald sill, Ontario
Authors: Pearce T. H.
Published: April 2011

A new technique for analyzing natural data is used on chemical data from the Dundonald sill. It is shown thereby that, with certain exceptions, the conclusions reached by Naldrett and Mason (1968) regarding the differentiation of the sill could have been expressed with greater certainty. The natural chemical data may be used as an independant check on rival hypothetical differentiation processes. The use of conventional graphical techniques has resulted in critical information remaining unused in tables of chemical analyses.
Devonian stromatoporoids from central Alberta, Canada
Authors: Fischbuch Norman R.
Published: April 2011

The Devonian Swan Hills reef complexes of western Canada contain a prolific and well-preserved stromatoporoid fauna. Species of the genera Hermatostroma, Atelodictyon, Stromatopora, Parallelopora, Ferestromatopora, and Clathrocoilona are common constituents of the reef, fore-reef, and reef platform limestones. Specimens from six reef complexes (Snipe Lake, Goose River, Kaybob, Virginia Hills, Swan Hills, and House Mountain) are described. Most species occur in several growth forms although one growth form is usually predominant. Two new species, Clathrocoilona sp. and Stromatopora sp., are recognized in the Swan Hills material.
Documentation of the sub-Cambrian unconformity, Rocky Mountains Main Ranges, Alberta
Authors: Aitken J. D.
Published: April 2011

Much of the existing literature on the base of the Cambrian System in the southern Rocky Mountains tends to de-emphasize the importance of the stratigraphic hiatus represented. Although a sub-Cambrian regional unconformity has been reported by several authors, conclusive evidence of the unconformity has not been published.This paper documents profound truncation of Miette Group strata of Windermere age at the base of the Gog Group of Early Cambrian age, and draws attention to several localities at which Precambrian structures are truncated at the base of the Cambrian. The sub-Cambrian unconformity is comparable in style and magnitude to the sub-Devonian unconformity of the same region.
The paleomagnetism of the Croker Island Complex, Ontario, Canada
Authors: Palmer H. C.
Published: April 2011

Meaningful paleomagnetic results were obtained from 23 of 30 oriented samples from the Croker Island Complex, North Channel of Lake Huron, Canada. The age of the complex is estimated to be 1475 ± 50 m.y. from a Rb–Sr isochron. The paleomagnetic pole calculated from the directions of remanent magnetization after partial ac demagnetization is 143 °West, [Formula: see text] North. This result, when compared with other paleomagnetic results from North America, indicates little or no polar wandering in the time interval 1.48 b.y. to 1.1 b.y. However, a significant shift in the pole position is indicated during the time interval 1.7 to 1.48 b.y.
Regional geochemical study of the Slave Point carbonates, Western Canada
Authors: Cameron E. M.
Published: April 2011

A regional geochemical study of the Slave Point Formation within an area of 35 000 square miles (~90 000 km2) in the subsurface of western Canada was made to relate chemical variation to facies change. Core and cuttings samples were obtained from 90 wells drilled for petroleum. The Slave Point Formation is a relatively uniform and pure calcitic limestone of Middle Devonian age. A reef facies, dolomitized in places, is developed along the margin of the carbonate shelf with a shale basin. These dolomites produce natural gas from several fields.R-mode factor analysis methods have been used to help interpret the element distribution. There are slight, but significant, chemical differences between limestones occurring close to dolomites and gas discoveries and limestones distant from these features. The principal differences are a smaller content of magnesium and strontium held in solid solution in the calcites and less clay minerals and pyrite in limestones occurring close to gas discoveries. These differences, which are related to dissimilar conditions during deposition and diagenesis, are used to form a multivariate discriminant function separating the two groups of limestone. This discriminant function is used to classify the different limestone sections. Sphalerite (with galena and quartz), a prominent feature of the unit, occurs principally in the dolomites along the margin of the shale basin.
The Federal–Provincial Committee on Huronian Stratigraphy: Progress report
Authors: Robertson J. A. , Frarey M. J. , Card K. D.
Published: April 2011

A Federal–Provincial Committee on Huronian Stratigraphy has been organized to review the present knowledge of the Huronian Supergroup, to apply a suitable stratigraphic nomenclature, and to describe type and reference sections for formations and groups. A nomenclature has been recommended and is stated in this note. Type and reference sections will be measured during the next two years.
Peter Kalm's geological observations in New France, 1749
Authors: Kranck E. H.
Published: April 2011

In 1749 Peter Kalm, a Finnish professor and naturalist, journeyed up the Hudson River, across Lake Champlain, to Montreal and thence down the St. Lawrence River. His notebooks of this journey contain many geological observations, the accuracy of which is remarkable, and merit him a place in the early history of the geology of Canada.
A simple method of calculating climatic corrections to heat flow measurements
Authors: Crain I. K.
Published: April 2011

A series approximation for calculating climatic corrections to include the effect of all of the Pleistocene glaciations is derived. The method is useful for boreholes less than 1200 m deep, and only two terms of the series are required for depths less than 600 m. About 70% of the effect at the surface is a result of the most recent deglaciation and this percentage increases with depth.
A conductivity model for certain features of the Alert anomaly in geomagnetic variations
Authors: Dyck A. V. , Garland G. D.
Published: April 2011

Measurements of the distortions of the magnetic and electric fields over a conducting body have been made on a model that emphasizes the effect of channelling of a current field, rather than electromagnetic induction. Certain effects observed on the model are similar to those which have been described for the Alert anomaly, and it is suggested that the conduction mechanism offers an explanation of some of the hitherto puzzling features at Alert.
Current, temperature, and depth data from a moored oceanographic buoy: Discussion
Authors: Needler G. T.
Published: April 2011

In the power spectrum of current speed presented by Grant there is a pronounced peak of about 18-hour period. On the basis of the period and the indicated lack of coherence of the oscillations in the vertical, the 18-hour peak undoubtedly arises from inertial oscillations.
The 1978–1980 surge of the Sherman Glacier, south-central Alaska
Authors: Bull Colin
Published: April 2011

One third of the ablation area of the Sherman Glacier was covered by a debris sheet resulting from the 1964 Alaskan earthquake. Subsequently observed changes in the mass balance and the movement regime of the glacier lead to the prediction of a surge-type advance in the near future.
References to glacier surges in North America
Authors: Horvath Eva V. , Field William O.
Published: April 2011

This compilation lists reported glacier surges in North America and published references. Additional references are also given for general discussions of surge phenomena and on surges in other parts of the world.
The climatic effects of large-scale surges of ice sheets
Authors: Wilson A. T.
Published: April 2011

Surges in ice masses of glacier size are now well accepted in glaciology. There seems no reason why a similar phenomenon should not occur in bodies of ice as large as continental ice sheets.If a continental ice sheet surged into the sea it would have a considerable effect on world sea-level. This is proposed as the mechanism of past sea-level fluctuations (cyclothems) of the Carboniferous and Tertiary.The effect of a surge of the Antarctic Ice Sheet on world climate is considered, with particular reference to the origin of ice ages.The requirements of an ice-age mechanism are discussed and it is concluded that a periodic surge of the Antarctic Ice Sheet, perhaps induced by a decrease in insolation to the south polar region, has all the requirements of an ice-age inducing mechanism. In particular, any oscillating system must have capacitance (storage) and impedance (resistance). It is not easy to find a system in nature with a sufficiently long period of oscillation. However, the build up of ice on Antarctica would provide a sufficiently slow charging of storage, and the ice sheet itself would provide the storage to yield a system of long enough period.It is proposed that when the Antarctic Ice Sheet surges, a large ice shelf is produced which increases the albedo of the Earth. The resulting cooling leads to the formation of secondary ice sheets in the Northern Hemisphere, which in turn leads to a further increase in albedo and further cooling. The break up of the ice shelf and its replacement by ocean would lead to a large decrease in the Earth's albedo. The resulting warming would lead to the rapid melting of the subsiduary ice sheets and the ending of the ice age.
Deformation of ice under high internal shear stresses
Authors: Jonas John J. , Müller Fritz
Published: April 2011

By means of transparent plastic dies, cylindrical samples of single crystal and polycrystalline ice were extruded into rods of one quarter the original cross-section area. The deformation was carried out at −5 °C and a mean strain rate of about 10−2 s−1. With the aid of polarized light, the formation of cracks and the occurrence of dynamic recrystallization were studied. The experiments of Steinemann, and more recent results in metals suggest that, during such plastic flow, two types of dynamic recrystallization are involved. At low strain rates, the recrystallization is periodic, leading to rapid increases in strain rate at constant applied stress; at higher strain rates, the recrystallization is continuous and the strain rate is constant. The possibility that dynamic recrystallization of the periodic type is associated with glacier surges is discussed.
Three-dimensional surges and recoveries in a numerical glacier model
Authors: Campbell William J. , Rasmussen Lowell A.
Published: April 2011

The Navier–Stokes equation, integrated vertically to yield a two-dimensional transport equation, is combined with the three-dimensional continuity equation. By assuming a linear relation between volume transport and bottom shear stress, a system of numerically tractable differential equations is developed that contains a nonlinear surface slope term and a term in which horizontal frictional forces are stated explicitly. These equations, which are not based on perturbation analysis, are integrated directly on a high speed digital computer. The coefficient of each term in the flow equations is composed of physical parameters (gravity, density, viscosity); therefore, since no quantities such as ice velocities enter the equations, it is only necessary to specify an arbitrary bed configuration and a net-balance versus altitude curve to obtain a glacier solution.For two beds, valley and cirque, steady-state glacier solutions are found for a variety of bed and lateral frictional values. By reducing the bed friction coefficient for one year over the entire bed of the glacier, surges are induced in each of these cases. A reduction in bed friction to 5% of its original value yields a surge resembling typical observed surges. Interesting wave forms occur during the recovery. During the initial recovery, after the bed friction has been restored to its original value, height falls continue to occur even in the lower accumulation zone. The original steady-state shape is approached asymptotically, with total recovery taking hundreds of years.
Glacier surges in the Karakoram Himalaya (Central Asia)
Authors: Hewitt Kenneth
Published: April 2011

The Karakoram and Alaska–Yukon region between them account for perhaps 90% of the known surging glacier events. While modern research and information is available for the latter region, the Karakoram, though often referred to, remains virtually unknown except in a very general sense. The prime aim of this paper is to collate all the information that is available for the Karakoram from the usually old and inaccessible documents where it is found. It establishes eleven instances of surges with reasonable certainty and the probability of many more. The (rare) instances of detailed descriptions of the phenomena are quoted. A short discussion is given of the degree to which the information, and knowledge of the Karakoram environment, equate with various mechanisms put forward to explain surging glacier events.
A succession of Tertiary strata off Nova Scotia, as determined by dredging
Authors: Marlowe James I.
Published: April 2011

Outcrops of strata ranging in age from Oligocene to Miocene occur on the sides of The Gully, a large submarine canyon near Sable Island. Data from dredge-sampling operations suggest that the exposed stratigraphic section may be as much as 1400 m thick. Analysis of dredge samples shows that the rocks collected are dominantly mudstone with minor components of sand. The exposed section is slightly coarser and more varied in texture toward the bottom than toward the top. Sand fractions are quartz-rich and contain only minor feldspar and rock fragments. Slight variations in accessory minerals may reflect the relative influences of different source rocks. The mineral suite is generally representative of plutonic and metamorphic source rocks. Abundant pyrite internal molds in mudstones suggested that the Eh in these sediments is negative. Illite and kaolinite composed most of the clay-size fraction of outcrop samples, with lesser amounts of montmorillonite.Continuous-seismic reflection surveys show that sub-bottom reflectors dip gently seaward. Below approximately 600 m, no sub-bottom reflections were recorded. Shallower, more discontinuous reflections suggest that locally reworked beds occur on the rim of the canyon.Petrological, structural, and faunal data indicate that the section is part of the Atlantic Coastal Plain Province, which, prior to this investigation, was known to occur only as far north as Georges Bank.
A gravity profile across the shield margin in the vicinity of St. Jerome, Quebec
Authors: Kumarapeli P. S. , Sharma Bijon
Published: April 2011

In the vicinity of St. Jerome, southern Quebec, platform rocks that abut against the Precambrian Shield margin belong to the Lower Ordovician Beekmantown Group. There, the basal member of the platform succession — the Upper Cambrian Potsdam Formation — that normally underlies the Beekmantown rocks does not appear at the surface. However, a gravity profile across the shield margin in this locality indicates the presence of a minimum of ~320 m of Potsdam below the Beekmantown rocks. The gravity profile also shows that at the shield margin, the Precambrian surface descends abruptly under the platform cover and the amplitude of the drop is about 600 m or more. This abrupt drop and the absence of outcropping Potsdam can be explained as due to post-Beekmantown faulting, which may actually have taken place in the Mesozoic Era.
Pollen genus Wodehousea and its stratigraphic significance in the Edmonton Formation (Maestrichtian), Alberta, Canada
Authors: Srivastava Satish K.
Published: April 2011

Four species of the pollen genus Wodehousea have been recovered from the Edmonton Formation (Maestrichtian) of Alberta, Canada. Wodehousea proved to be stratigraphically significant in subdividing the pollen assemblage of the Edmonton Formation, owing to the restricted vertical distribution of its various species.
Paleomagnetism of the Nipissing diabase, Cobalt area, Ontario
Authors: Symons D. T. A.
Published: April 2011

At Cobalt the Nipissing diabase intrusive occurs as a 1000 ft (~305 m) thick undulating sheet exposed in a series of basin and arch structures from which 112 specimens were collected at 14 sites. Paleomagnetic analysis of the cleaned natural remanence directions from the 11 acceptable sites suggests that these structures are dominantly primary. Minor post-solidification compression associated with the NW–SE trending faults may have amplified the primary NE–SW axial trends of the structures. Significant folding adjacent to the faults does not appear probable. The origin of the narrow argentiferous veins is probably related to minor local differential movements of large blocks of diabase or to cooling-contraction of the sheet. A revised pole position of 91.9 °E, 19.4 °N (dp = 3.9°; dm = 6.5°) is given for the 2140 m.y. old Nipissing diabase.
Continental marine transition in the Devonian of Prince of Wales Island, Northwest Territories
Authors: Miall A. D.
Published: April 2011

In eastern Prince of Wales Island the Peel Sound Formation is subdivided into upper and lower members on the basis of lithology. The upper member comprises five laterally equivalent north–south facies belts which are in westward order:1) Conglomerate Facies: cobble and boulder conglomerates deposited on alluvial fans mainly by the action of debris floods.2) Conglomerate–Sandstone Facies: interbedded conglomerate, fine to coarse red sandstone and red siltstone in a repeated fining-upward succession, deposited by low sinuosity braided streams. Cyclic sedimentation is attributed to channel migration and infill.3) Sandstone Facies: the presence of laterally extensive planar cross sets suggests point bar deposition in high sinuosity streams. Tabular bedded sandstone was deposited by stream floods in upper regime flow.4) Sandstone–Carbonate Facies: streams flowing westward formed small deltas, accumulating red, pink, and buff sandstones as topset deposits, interbedded with dolomites containing marine fossils, and clean washed gray sandstones, shales and dolomites with ostracods, pelecypods, gastropods, and Lingula, indicating an estuarine environment.5) Carbonate Facies: dolomites with abundant marine fauna and limited clastic content. Sedimentary structures indicate quiet, shallow water conditions.Paleocurrent evidence indicates an easterly source, confirmed by conglomerate clasts derived from the Boothia Uplift, an area of Lower Paleozoic and Proterozoic rocks extending northwards from the Boothia Peninsula to Somerset Island.
Observations on Cretaceous outcrop from a submersible—Scotian Shelf
Authors: King Lewis H. , MacLean Brian
Published: April 2011

Direct observations from a submersible on a Cretaceous bedrock occurrence at 44°47′ N and 60°20′ W corroborate previous conclusions drawn from data obtained by remote sampling techniques. The direct observations provided additional detail.
Numerical continuum approaches to analysis of nonlinear rock deformation
Authors: Voight Barry , Dahl H. D.
Published: April 2011

In the continuum approach to problems of geologic mechanics, the ground surrounding a deformation zone is replaced mathematically by an idealized material that deforms in accordance with principles of continuum mechanics. Studies published to date have been rather few in number and have often followed a methodology characterized by restrictive material property and boundary condition assumptions. In order to avoid these difficulties, emphasis in this paper is given to modern numerical methods. Discrete-element formulations of matrix structural analysis are shown to be particularly useful, inasmuch as they are adaptable to solutions of systems characterized by nonlinear anisotropic materials, heterogeneously distributed, containing internal discontinuities, and of arbitrary topographic or internal boundary configuration.
Physico-chemical characteristics and postglacial desalination of Stanwell–Fletcher Lake, Arctic Canada
Authors: Rust Brian R. , Coakley John P.
Published: April 2011

Stanwell–Fletcher Lake is a cold monomictic Arctic lake, essentially isothermal at about 1.5 °C, with almost complete ice cover throughout the year. The annual heat input is about 13 000 cal cm−2, much less than that of dimictic Arctic lakes. The lake is isochemical, with very low ionic concentrations.The lake basin was formed during the Pleistocene by glacial scouring of soft sediments from a graben. As the ice retreated the basin filled with sea water, and became a fjord. Subsequent isostatic uplift raised the marine shorelines to 150 m above present sea level; the uplift curve indicates emergence of the fjord sill and termination of estuarine conditions about 3500 years ago. Tidal influx persisted for about 1100 years before the lacustrine phase started.Comparisons with modern fjords and coastal meromictic lakes suggest that most of the salt left the lake during its lacustrine phase. The mechanism was probably entrainment of salt water into a deep freshwater current flowing over the chemocline due to convective circulation in summer.
The pollen stratigraphy of a dated section of Late Pleistocene lake sediment from central Alberta
Authors: Lichti-Federovich Sigrid
Published: April 2011

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 province. The basal organic sediment was radiocarbon dated at 11 400 ± 190 y (GSC-1049) and a layer of Mount Mazama type ash was recognized at the 398 cm level. This represents the furthest extension into Canada of Mazama ash records. Five pollen assemblage zones have been identified—at the base, a Populus – Salix – Shepherdia – Artemisia assemblage, which is unique in the Late Pleistocene of N. America, and is interpreted as a pioneer forest and shrub community which occupied the area immediately following deglaciation. This is succeeded by a spruce dominated assemblage which conforms in general to many early Late Pleistocene Picea assemblages from western Canada and adjacent United States, interpreted as a pioneering version of the boreal forest. There follows a tree birch-dominated assemblage with poplar and hazel, suggesting a slight amelioration of climate, and this trend appears to have continued to about 6000 B.P. when a birch – alder – herb assemblage reaches its maximum; this is followed by a spruce – birch – alder assemblage, which continued to the present and is interpreted as an expression of a deterioration in climate about 3500 B.P. The apparent absence at the site of grassland, although the birch – alder – herb assemblage suggests that the grassland might have advanced closer to the site than at present (240 km (150 miles)), supports the hypothesis that there was never a Late Pleistocene connection between the Peace River and the main southern grasslands.
The Mid-Atlantic Ridge near 45° N. XI. Seismic velocity, density, and layering of the crust
Authors: Barrett D. L. , Aumento F.
Published: April 2011

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 occurrence of serpentinites at all elevations on the slopes of seamounts implies that they do not form a continuous layer and because of their relatively low velocity, it is unlikely that layer 3 is composed of these rocks. Their presence as hydrated diapiric intrusives is more plausible.
New rodents and lagomorphs from the Upper Miocene Wood Mountain Formation of southern Saskatchewan
Authors: Storer John E.
Published: April 2011

Diagnoses and illustrations of the holotypes and paratypes are given for two new genera and seven new species of the mammalian orders Rodentia and Lagomorpha from the Upper Miocene Wood Mountain Formation of southern Saskatchewan. Taxa named include the eomyid Adjidaumo russelli, sp. nov.; the heteromyids Perognathus saskatchewanensis, perognathoides kleinfelderi, and Peridiomys borealis, spp. nov.; the entoptychine geomyid Lignimus montis, gen. et sp. nov.; and the ochotonids Hesperolagomys fluviatilis, sp. nov., and Russellagus vonhofi, gen. et sp. nov. All taxa treated in this paper are from the Kleinfelder Farm locality, near Rockglen, Saskatchewan. More detailed descriptions and comparisons will be given in a subsequent publication.
Coal metamorphism and hydrocarbon potential in the Upper Paleozoic of the Atlantic Provinces, Canada
Authors: Hacquebard P. A. , Donaldson J. R.
Published: April 2011

Coal rank is used to measure the degree of organic metamorphism, which is of great importance in the evaluation of the hydrocarbon potential of a region.The rank-is determined on true coal seams and coaly inclusions in sandstones by measuring the reflectance of vitrinite, which is a major constituent of coal. A large number of samples, encompassing nearly the entire area of Upper Paleozoic deposition in the Atlantic region, was examined. From these an isoreflectance map has been constructed. The map shows a distinct pattern of regional metamorphism that resembles the tectonic development of the region. The known oil and gas occurrences coincide with the areas of lowest rank.In this region the coalification is predominantly postdeformational, being caused by the maximum depth of burial that existed after folding. In the higher-rank coals the increase in rank with depth can be measured accurately by the reflectance (R0). In these coals different R0-depth factors were obtained in different areas, which can be related to different geothermal gradients.In the lower-rank coals (below 62 % fixed carbon) the reflectance parameter is useful only for broad rank assignments, and precise rank predictions at depth cannot be made from surface observations. However, on suitable borehole samples the rank can be measured with the reflectance. This has been done on eight exploration wells and has resulted in finding the approximate vertical position of the oil "deadline" with regards to the degree of organic metamorphism.Factors limiting the selection of promising areas for future exploration are discussed, with reference to the vertical and regional changes in rank that have been observed.
Potassium–argon ages of Topley Intrusions near Endako, British Columbia
Authors: White Wm. H. , Sinclair A. J. , Harakal J. E. , Dawson K. M.
Published: April 2011

Twenty-five potassium–argon ages were obtained from granitic rocks in the Endako area of central British Columbia which are presumed to be genetically related and known collectively as the Topley Intrusions. Most of the ages cluster around 138 m.y. but some are as old as 155 m.y. and one is only 114 m.y. These data might indicate either one protracted perhaps intermittent magmatic event culminating in early Upper Jurassic or three separate and unrelated events. In either case the isotopic age is some 40 m.y. less than the age previously assigned to the Topley Intrusions on a basis of apparently good geological evidence.
The use of trend surfaces in till fabric analysis
Authors: Roberts M. C. , Mark D. M.
Published: April 2011

A method, based on trend surface analysis, was developed to utilize till fabric data in the construction of ice movement maps. To illustrate the technique three areas were selected: the Wadena drumlin field of Minnesota, the till plain of East Anglia, and the Fraser Valley area of British Columbia.
Wave propagation in a horizontally-layered crust in terms of linear system theory
Authors: Jensen O. G. , Ellis R. M.
Published: April 2011

Elastic wave propagation in a horizontally-multilayered crust has been formulated in terms of linear systems theory. Exact linear system models, considering all possible internal reverberations, have been obtained for plane compressional and rotational waves incident at the base of a horizontally layered elastic medium. The linear system has been analyzed using Laplace and Fourier transform techniques. The Fourier transform solution corresponds to the Haskell matrix solution in terms of the elastic wave equations. The method has been extended to analyze the effects of attenuation within the crustal layers.
Cratonic reactivation in the Precambrian basement of western Canada. Part II. Metasomatism and isostasy
Authors: Burwash R. A. , Krupička J.
Published: April 2011

Large-scale deformation of crystalline rocks coupled with metasomatic recrystallization during the Hudsonian orogeny (~1800 m.y. ago) determined the main features of a large portion of the western Canadian Precambrian basement (the Athabasca mobile zone) and its subsequent geological history. The following are the main changes resulting from deformation and metasomatic recrystallization in the Athabasca mobile zone:(a) Significant increase in K2O and Rb, significant decrease in CaO, MgO, Na2O, and Sr, and almost unchanged Al2O3 and SiO2. These changes reflect the relative mobility of major oxides. The very marked change in the Rb/Sr ratio constitutes an important disturbing factor for isotopic age dating.(b) Marked increase in potassium feldspar combined with very marked increase in secondary minerals (epidote, chlorite, muscovite), clear-cut decrease in plagioclase and primary dark minerals, and only a slight increase in quartz. The coexistence of newly-formed microcline and low-grade minerals cannot be explained by disequilibrium.(c) Decrease in the average density of deformed and K-metasomatized complexes, and the probable subsequent long-term isostatic adjustments in the western Canadian sedimentary basin.
Sedimentation of the Mississippian evaporites of the Maritimes: an alternative model
Authors: Evans Robert
Published: April 2011

Recent work on the carbonates and sulfates of the Mississippian Windsorian rocks of the Maritime Provinces has led to the idea that the widespread evaporites in the area are the product of sedimentation in supratidal fiats and in depressions in those flats. The tectonic setting and lithologic features of the more soluble evaporites, however, suggest a comparison with the Plio-Pleistocene sediments of the Dead Sea Graben, and it is proposed that the great thicknesses of chlorides known to exist in Nova Scotia and New Brunswick are the result of rapid sedimentation in possibly deep water within the Fundy Rift formed at the end of the Acadian Orogeny.
Computerized geological mapping in the Grenville Province, Quebec
Authors: Wynne-Edwards H. R. , Nandi A. , Kehlenbeck M. M. , Laurin A. F. , Sharma K. N. M. , Franconi A.
Published: April 2011

Since 1965, the Quebec Department of Natural Resources has conducted reconnaissance mapping in the Grenville Province, completing to date over 70 000 square miles (181 000 km2). In 1968 a computer-based data processing system was designed at Queen's University, and applied to this Grenville Project. Data are recorded in the field on input documents designed to recover a complete description of the structure and lithology of an outcrop in a standard and reproducible form. From these records a data bank, now with descriptions of over 5000 outcrops, has been constructed for the field seasons of 1968 and 1969. Lthological sorting programs based on the textural and mineralogical qualities used to define rock types have been written to provide listings of some 40 potential map-units. Outcrop maps identifying lithologies have been drawn on a computer-driven drum plotter to provide the geologist with a basic document from which to make geological interpretation. Structural data have been extracted and plotted in equal-area projections, and also plotted on maps directly by machine, using standard structural symbols for layering, foliation, and lineation. The system has upgraded the standard of data collection in the field, and provides a rapid and versatile means of handling data and of interpreting the geology. The data bank, when made publicly available, will enable users of government geological maps and reports to reinterpret the area in their own manner, or freely to add any proprietary data in the preparation of revisions.
Paleomagnetism and correlation of some Middle Keweenawan rocks, Lake Superior
Authors: Palmer H. C.
Published: April 2011

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. The Logan sills, the volcanics of the Osler Group, the lava section at Alona Bay, the lower 6000 ft (1829 m) of North Shore volcanics, the lower 1000 ft (305 m) of Cape Gargantua volcanics and the lower 3000 ft (914 m) at Mamainse Point are of reverse polarity. Normal directions of magnetization, which differ from the reverse directions of magnetization by amounts ranging from 140° to 163° occur throughout the Michipicoten Island section, and in the upper parts of the North Shore, Cape Gargantua, and Mamainse Point sections. Provided part of the section at Mamainse Point has been repeated by faulting, these new results, together with data from the literature, are compatible with a single polarity reversal in Middle Keweenawan time separating older reverse polarity rocks from stratigraphically younger normal polarity rocks. The mean direction of magnetization from a conglomerate test is defined with higher precision than would be expected from a randomly distributed population. It is believed that this mean direction reflects a secondary component of magnetization which cannot be preferentially removed by alternating field demagnetization and which has caused the non anti-parallel alignment of normal and reverse populations of magnetization. An estimate of the pole position during Middle Keweenawan time can, however, be made by calculating a pole given equal weight to the mean normal and mean reverse pole. This is calculated to be 159° W, 42° N.
Regional microfabric analysis and insoluble residues of Black River Group (Middle Ordovician) in southern Ontario
Authors: Mukherji K. K. , Winder C. G.
Published: April 2011

Carbonates of the Middle Ordovician Black River Group across the outcrop in southern Ontario have a fabric of elongate particles trending consistently in NW–SE and NE–SW directions. The origin of the fabric is considered primarily resulting from longshore currents in a shallow basin influenced by tidal activity. Insoluble residues constitute a small portion of the rock mass, but contain a wide range of mineral species. Although their distribution is sporadic, suites of minerals east and west of Marmora contain distinctive species. Generally, the detrital minerals seem to reflect the Precambrian source area to the north of the Paleozoic outcrop. A higher concentration of anhydrite to the east is interpreted as indicative of an area of more restricted marine conditions.
The Mid-Atlantic Ridge near 45° N. XII. Coercivity, secondary magnetization, polarity, and thermal stability of dredge samples
Authors: Park J. K. , Irving E.
Published: April 2011

The mean coercivities of natural (n.r.m.), anhysteretic (a.r.m.), and isothermal (i.r.m.) remanent magnetization in 34 samples of submarine basalt from the Mid-Atlantic Ridge are 270, 250, and 370 oersteds respectively, showing their magnetization to be stable. The spectra of coercive force of n.r.m. and a.r.m. of these basalts are similar, although, because of small secondary components, there are small differences in the low coercive force range (0 to 100 Oe). The magnitude and sign of these differences are used to derive an empirical relationship between coercivity and the magnitude of secondary components, and to infer the polarity of primary components. The inferred polarities of samples from within the Median Valley of the Ridge are all normal, whereas both normal and reversed polarities are found from the adjacent mountains and plateaus. Experiments show that warming specimens from the Median Valley to 100 °C for 90 h causes the production of a new component with a lower intensity, and higher blocking temperature, but with the same direction as the original natural remanence. Similar effects may occur in the axial volcanic zone, and may have caused the decrease in intensity with distance from the axis. The magnetic properties of various other rock types from the Mid-Atlantic Ridge are also described.
A possible diapir in the Laurentian Channel
Authors: Keen M. J.
Published: April 2011

Seismic reflection studies in the Laurentian Channel have located a structure, which may be a diapiric salt intrusion, at 45° 12′ N, 57° 07′ W. It occurs over the eastern end of a part of the region of low, free-air gravity anomalies, which extends from eastern Nova Scotia. It is reasonable to suppose that the structure is a diapiric salt intrusion; evaporites have been reported in one drill hole to the east, on the Grand Banks. If so, this confirms the interpretation of the gravity anomalies by Loncarevic and Ewing. A reflection profile across the whole channel does not support the view that the present form of this part of it is of structural origin.
The Snipe Lake, Alberta earthquake of March 8, 1970
Authors: Milne W. G.
Published: April 2011

An earthquake of magnitude 5.1 occurred on March 8, 1970 at an unusual location in north central Alberta, Canada. The epicentral coordinates obtained from a study of seismic records and the center of the "felt" report area indicate an epicenter near Snipe Lake. Past data indicate that an earthquake in this eastern Cordillera is a very rare event. No change appears to be needed for the seismic probability map of the 1970 National Building Code.
Discovery of Mazama ash in Saskatchewan, Canada
Authors: David Peter P.
Published: April 2011

The first known Mazama ash occurrence in Saskatchewan was discovered in eolian sediments at the top of the bluffs on the South Saskatchewan River valley 20 miles (~32 km) west of Leader, Saskatchewan. The chemical composition and the refractive index of the volcanic glass serve for the definite identification of the Mazama ash. The ash layer is a useful horizon marker in the eolian sediments, for it represents a time-break at 6 600 years ago. It is suggested that eolian deposits in similar sedimentary environments be examined for other occurrences of the Mazama ash.
Marine algae of the Champlain Sea episode near Ottawa
Authors: Illman W. I. , McLachlan J. , Edelstein T.
Published: April 2011

Examination of a marine algal deposit from the Champlain Sea (10 800 ± 150 y old) found by Mott (1968) revealed that it is composed mainly of well preserved blades of Laminaria. These were associated with another brown species not susceptible of definite identification and a single fragment of a foliose red species, probably Rhodymenia.Filaments of Audouinella membranacea were found in hydroids in the deposit and another small red alga, Acrochaetium identified. The presence of several plant pigments was indicated by chromatographic and spectrographic techniques.