bluuebunny/crossref_metadata_2025 huggingface dataset:
PALAEOMAGNETISM OF THE ABITIBI DYKE SWARM
Authors: Larochelle A.
Published: April 2011

Previous data published on the palaeomagnetism of a group of Precambrian diabase dykes, referred to as the Abitibi swarm, were characterized by considerable angular dispersion attributed to a number of possible factors. The relative importance of these factors was investigated in the light of data obtained for an independent suite of samples from the same group of dykes. Most of the previous interpretation is probably no longer valid because the magnetization of the swarm was found to be distributed tightly about three mean directions rather than dispersed widely about one mean direction, as originally thought. It is concluded that the dykes forming the swarm were injected intermittently during several widely distinct periods and that, accordingly, long-range correlation of diabase dyke swarms on the sole basis of their palaeomagnetism may be more hazardous than was realized earlier.
THE LATE-WISCONSIN PRELATE FERRY PALEOSOL OF SASKATCHEWAN
Authors: David Peter P.
Published: April 2011

Five occurrences of the Prelate Ferry paleosol are known in exposures in the tributaries of the South Saskatchewan Valley between the Prelate Ferry and Lancer Ferry crossings, in Saskatchewan. At the reference section, 8 mi north of Prelate, Saskatchewan, the paleosol is best developed, and comprises a very dark brown A1b horizon, 12 in. thick; a grey A2b horizon, 7 in.; a dark brown B1b and a lighter B2b horizon, 12 and 19 in. thick respectively; and a Cb, horizon, more than 10 in. thick. The paleosol, a planosol or possibly a solodized-solonetz, developed on the lower till and is buried by 120 ft of sediments comprising two till sheets and three beds of stratified drift. The non-glacial Prelate Ferry interval during which the paleosol formed had a local climate similar to that of today. The beginning of the interval is not known, but it ended about 20 000 years ago, when the last major ice advance occurred in the area. Laboratory examinations indicate that the paleosol is pollen-sterile; it shows an upward decrease in grain size; it is weathered, noncalcareous in most parts; it is slightly to strongly alkaline; and it has a clay mineral content similar to that of the underlying till.
GLACIER MAPPING IN GREENLAND
Authors: Helk Colonel J. V.
Published: April 2011

The history and problems of mapping in Greenland are briefly reviewed, with particular reference to the Indlandsis (the Ice Cap) and the glaciers. The author calls for greater collaboration between the glaciologist and the topographer, and cautions against placing too great reliance on the present maps for calculations of the volume of the Indlandsis. Techniques now being developed will lead to a much more accurate assessment of volume. Finally, the regime of an ice-dammed lake in southwest Greenland is discussed on the basis of photogrammetric data and as an example of how such data can be used to explain glaciological phenomena.
SOME GLACIOLOGICAL INTERPRETATIONS OF REMAPPING PROGRAMS ON SOUTH CASCADE, NISQUALLY, AND KLAWATTI GLACIERS, WASHINGTON
Authors: Meier Mark F.
Published: April 2011

Remapping programs on glaciers are undertaken to determine changes in ice thickness and volume, which supposedly reflect glacier response to changing climate. However, thickness changes, derived photogrammetrically, cannot be used to determine ablation or other specific mass budget quantities, or response characteristics, without concurrent measurements made on. the glacier surface, The varied nature of the difficulty is illustrated by the following examples: (1) data front South Cascade Glacier demonstrate that the rate of change of thickness is the vectorial combination of emergence velocity, specific net budget rate, and (in the accumulation area only) a compaction velocity; (2) limitations on the use of photogrammetric data to detect and interpret kinematic waves are illustrated by results from Nisqually Glacier; (3) changes in two lobes of Klawatti Glacier show that climatic changes cannot be extrapolated from single-glacier maps because of meso-scale meteorological complications.
GLACIER SURVEYING AND MAPPING PROGRAM OF THE OHIO STATE UNIVERSITY
Authors: Brandenberger A. J. , Bull C.
Published: April 2011

An extensive program of glacier mapping and associated glaciological studies has been in progress for about 10 years at the Department of Geodetic Science and the Institute of Polar Studies of the Ohio State University. The program covers glaciers in the western United States, Alaska, the Yukon Territory, Greenland, and Antarctica. Ground surveying and aerial triangulation have been employed, and the mapping has been performed stereophotogrammetrically by means of first- and second-order instruments. Surveying and mapping phases of the work are described, and data on glacier structure, volume variations, and surface ice velocity are presented to illustrate the value of photogrammetric techniques in glaciological studies.
INTERNATIONAL EXPERIMENTS IN GLACIER SOUNDING, 1963 AND 1964
Authors: Waite Jr. Amory H.
Published: April 2011

In 1963 and 1964, under the sponsorship of the United States Army, specialists in ice sounding from various countries assembled at Camp TUTO, Greenland, to evaluate the latest sounding techniques. These international experiments showed that British and American radio-sounding systems gave results of comparable accuracy to those obtained by seismic sounding. In the two seasons bottom profiles of the ice cap were obtained along traverses totalling about 640 km. Ice thicknesses up to 2 000 m were measured as fast as the support vehicles could travel across the ice cap.
ALLOGRAPTUS CANADENSIS N. SP.; ITS SIGNIFICANCE TO LOWER ORDOVICIAN CORRELATION
Authors: Erdtmann Bernd-Dietrich
Published: April 2011

A declined four-branched graptoloid is referred to a new species of Allograptus, a genus of the family Sinograptidae described from the uppermost Lower Ordovician of China. This new Canadian species has been discovered from the upper Lévis Formation at Lévis, Québec, and is the first representative of Allograptus in North America. A description of A. canadensis n. sp. is presented with a discussion on its possible significance for international stratigraphic correlation.
A COMPUTER-ORIENTED FIELD SHEET FOR STRUCTURAL DATA
Authors: Haugh I. , Brisbin W. C. , Turek A.
Published: April 2011

A computer-oriented field data sheet for the efficient recording and processing of structural data has been developed and tested in the field. Although primarily designed for a specific project in the Precambrian Shield, it should be suitable, with only minor modifications, for other Precambrian areas.
STRATIGRAPHY AND PALYNOLOGY OF BURIED ORGANIC DEPOSITS FROM CAPE BRETON ISLAND, NOVA SCOTIA
Authors: Mott R. J. , Prest V. K.
Published: April 2011

Pollen analysis of four non-glacial, sub-till deposits on Cape Breton Island, Nova Scotia, yielded pollen assemblages indicative of climates cooler than the present in that area. New radiocarbon dates from Hillsborough (>51 000 years), Bay St. Lawrence (>38 300), and Whycocomagh (>44 000 years) place the deposition of these deposits in pre-classical Wisconsin time. The Hillsborough and Whycocomagh deposits are considered to be time-equivalent based on pollen analysis. A lack of distinct assemblages at Bay St. Lawrence and Benacadie prohibits correlation with one another and with the Hillsborough and Whycocomagh beds. Inferences drawn from the pollen flora and the stratigraphy indicate an early Wisconsin interstadial age for these deposits rather than a Sangamon interglacial age. They are tentatively correlated with the St. Pierre interstade in Quebec.
AN ESTIMATE OF THE COMPOSITION OF PART OF THE CANADIAN SHIELD IN NORTHWESTERN ONTARIO
Authors: Reilly G. A. , Shaw D. M.
Published: April 2011

An attempt has been made to estimate the abundance of trace and major constituents in the Precambrian surficial rocks of a large part (43 000 square miles) of the Red Lake–Lansdowne House area in northwestern Ontario. One-hundred and two composite samples were made to represent eight rock types in seven adjacent map-areas of equal size. Major element analysis was carried out on eight composite samples representing rock types for the whole area. Analysis of variance techniques have detected significant regional variations of Cr, Mn, Sr, and Ba. Significant variation exists between rock types for all trace elements analyzed except Cu.
SELECTIVE CEMENTATION IN TERTIARY SANDS AND GRAVELS, SASKATCHEWAN
Authors: Kupsch W. O. , Vonhof J. A.
Published: April 2011

Selective cementation of the coarsest sediments in exposed stratigraphic sequences of the Cypress Hills Formation and the Wood Mountain Formation in Saskatchewan is a post-depositional feature of recent origin. It is governed by locally prevailing hydrologic conditions and by the factors that control the precipitation of calcium carbonate in the interstices of sand and gravel at the air-rock interface. The lateral extent of cementation is small and the process is continuous with slope retreat.
OBSERVATIONS OF TURBULENT DIFFUSIONIN A NATURAL CHANNEL
Authors: Church Michael
Published: April 2011

Fluid flow is a diffusion process. For homogeneous turbulence, dispersion occurs normally about the center of the process, the rate of growth depending on the diffusion coefficients Ki.Measurements of Ki for longitudinal and lateral diffusion are presented for the Lewis River, a proglacial stream in north-central Baffin Island. In the river, flows up to 250 m3/s, fully turbulent, are characterized by 'roller eddies'. Observations were made by electro-chemical recording of longitudinal dispersion of salt solutions and by photography of lateral dispersal of dye plumes. It is shown that the K-values depend on the scale of flow, while the overall pattern of diffusion depends on the flow and channel geometry of the stream.The geomorphological consequences of diffusion include the phenomenon of momentum transfer in the channel and resultant shear stresses brought to bear on the walls, and the pattern of sediment transport.
REFERENCE SECTION FOR THE MAJEAU LAKE FORMATION
Authors: Pollock C. A.
Published: April 2011

A cored section in the Imperial Westlock No. 14–24 well (Lsd. 14, Sec.24, Tp.59, Rge.26, W.4th Meridian) in northeastern Alberta is proposed as a type reference section for the Majeau Lake Formation, and it is proposed that Texaco McColl Majeau No. 1 (Lsd. 12, Sec. 1, Tp. 57, Rge. 3, W. 5th Meridian) be formally adopted as the type section well. The formation is 216 ft thick in the reference well. The conodont fauna suggests that the Majeau Lake Formation lies within the middle Polygnathus asymmetrica (to Iα) Zone of the German Devonian standard section.
THE CRUST OF THE EARTH UNDER HUDSON BAY
Authors: Hunter J. A. , Mereu R. F.
Published: April 2011

The Hudson Bay crustal experiment of 1965 involved 41 shots placed on two lines, E–W and NW–SE, in the Bay. The first arrival data of eight land stations situated around the bay were utilized in the time–term analysis. The preferred crustal velocity was found to be 6.32 ± .06 km/s, and the velocity of the upper mantle to be 8.23 ± .03 km/s. Depth calculations from time–terms and employing Geological Survey of Canada near-surface data, show the Mohorovicic discontinuity to be undulatory in nature throughout the bay. An overall rise of this interface occurs from a depth at Churchill of approximately 41 km to a minimum depth of approximately 27 km towards Gilmour Island. Crustal thickening occurs again on the east side of the bay, with a depth of 41 km at Povungnituk. As well, the crust thins towards the NW from an approximate depth of 37 km in the center to a depth of 26 km near Chesterfield Inlet. The correlation between existing surface geology and the Mohorovicic discontinuity undulations is discussed.
A LATE CRETACEOUS PLANT ASSEMBLAGE FROM EAST-CENTRAL BRITISH COLUMBIA: I, FOSSIL LEAVES
Authors: Rouse G. E.
Published: April 2011

Leaf compressions, spores, and pollen grains referrable to about 45 species were collected from a series of fine silts and coal stringers in the Parsnip River valley of the Rocky Mountain Trench. The leaf assemblage described in this paper indicates a late Maestrichtian to Danian age, somewhat younger than generally comparable assemblages previously reported from the lower part of the Edmonton Formation of Alberta, and from the Hell Creek, Lance, and Fox Hills Formations in the western interior of the United States. It also contains several species reported from the Nanaimo Group on eastern Vancouver Island. Plant microfossils (to be described in a later paper) include species of Glyptostrobus, Sciadopitys, Aquilapollenites, Pistillipollenites, Alnus, Myrica, Tilia, Pterocarya, and Carya, together with tricolpate pollen of uncertain affiliation. The combined leaf and microfossil assemblages indicate a warm mesothermal and humid paleoecological setting of low relief, suggesting absence of major mountain ranges westward to the Pacific Ocean.
Analogue model measurements of electromagnetic variations in the near field of an oscillating line current
Authors: Dosso H. W. , Jacobs J. A.
Published: April 2011

An analogue model for studying electromagnetic variations for an overhead oscillating line current is described. Measurements of electric and magnetic fields for model earth–sea interfaces are discussed and compared with results reported earlier for an overhead sheet current. A truncated cone representing a circular sea, a graphite wedge representing an ocean coastline, and a graphite wedge underlain by a graphite block representing an upwelling conducting zone in the earth's mantle near a sea coast are considered. In some cases the results for the line current model differ appreciably from those for the sheet current model, indicating that the nature of the source field can be an important factor in determining the behavior of the field components. The model measurements indicate that land–sea interfaces produce no appreciable anomalous magnetic fields at frequencies below 0.01 cps and hence the presence of the sea alone cannot account for coastal magnetic field anomalies. The results obtained for the model coastline structures tend to support the idea put forth by various workers that experimentally observed coastal magnetic field anomalies can in some cases be explained by assuming an upwelling conducting zone within the earth's mantle.
Occurrence of interstratified glauconite-montmorillonoid pellets, Queen Charlotte Sound, British Columbia
Authors: Murray J. W. , Mackintosh E. E.
Published: April 2011

'Glauconite pellets', discovered in the bottom sediments of the Queen Charlotte Sound on the British Columbia continental shelf, consist of interstratified glauconite-montmorillonoid and kaolin. Expansion of the interstratified material to form a broad diffuse peak on glyceration reflects the presence of the montmorillonoid component. Potassium saturation followed by a series of heat treatments produced an asymmetrical 9.94 Å peak. The clay fraction associated with the 'glauconite pellets' was composed of predominantly montmorillonoid with lesser amounts of kaolin and chlorite. These 'glauconite pellets' may be either residual (eroded out of outcrops on the sea floor), relic Pleistocene, or Recent. It is suspected, regardless of the time of formation, that this particular glauconite formed diagenetically from montmorillonoid by adsorption of potassium in interlamellar positions and possibly some substitution of magnesium and iron for aluminum in octahedral positions.
Geophysical studies of the continental margin northeast of Newfoundland
Authors: Fenwick D. K. B. , Keen M. J. , Keen Charlotte , Lambert A.
Published: April 2011

A seismic and magnetic survey has been made of an area that straddles the continental margin northeast of Newfoundland from the edge of the shelf to the ocean basin of the Labrador Sea. The results bear on the question of the extension of the mobile belt of the Appalachian System in Newfoundland to the margin. Our seismic studies show that the crust is approximately 30 km thick beneath the edge of the shelf northeast of Newfoundland, and thins to approximately 12 km at the foot of the slope. Seismic studies by Lamont Geological Observatory suggest that the mobile belt continues to the upper part of the slope; our studies support this. Large magnetic anomalies run nearly parallel to the edge of the shelf over the slope and rise, at right angles to the strike of the Appalachian System. Their amplitude is 1400 gammas and the belt of anomalies is 180 km wide. It runs continuously for at least 220 km. One interpretation is that the anomalies owe their origin to the juxtaposition of a magnetic continental plate 30 km thick against a thinner magnetic oceanic plate 10 to 12 km thick. We suggest that the continental crust is particularly magnetic, and the 'shelf-edge' anomalies particularly large, because it represents the basic mobile belt of the Appalachian System terminating beneath the lower part of the continental slope. The contrast in magnetization between non-magnetic oceanic mantle and magnetic continental crust is due to this, and perhaps also to higher temperatures in the oceanic mantle. They could be particularly high if the Labrador Sea is the site of a mid-ocean ridge. Some evidence from the magnetic survey suggests that a fault with dextral slip runs on the continent side of the margin in a northeasterly direction. It does not continue into the ocean basin.
The Grand Bois anomaly: The magnetic expression of another Monteregian pluton
Authors: Kumarapeli P. S. , Coates M. E. , Gray N. H.
Published: April 2011

An aeromagnetic anomaly, similar to the ones associated with known Monteregian plutons, occurs over a low hill at Grand Bois, about 4 km west of Mount Johnson. In the area of this anomaly, a gravity high of over 1.60 mgals and also two outcrop localities with igneous rocks of Monteregian types, were detected. Therefore, it is concluded that the aeromagnetic anomaly is caused by a blind Monteregian pluton, for which the name "Grand Bois Intrusion" is proposed.
Dating some significant events in the history of the Swaziland System by the Rb–Sr isochron method
Authors: Allsopp H. L. , Ulrych T. J. , Nicolaysen L. O.
Published: April 2011

The Swaziland System, in the southeastern Transvaal, is one of the oldest stratified systems exposed. A brief account is given of this folded synclinal belt, and of the heterogeneous tract of migmatites. gneisses, and granites which surround it. Related geochronological work in this tract is summarized.An attempt has been made to date the system using the Rb–Sr isochron technique on (1) pegmatites that intrude it, (2) shales and graywackes of the Fig Tree Series, (3) acid lavas of the Onverwacht Series, and (4) biotite-tremolite schists associated with mineralized zones along the Onverwacht-Fig Tree contact. Essentially linear isochron plots were obtained in each case, but great caution is needed in interpreting the precise geological significance of each calculated age. The pegmatite data are interpreted as establishing a minimum age of 3.00 ±.03 b.y. for the Swaziland System, and as indicating that its deposition occurred at a significantly earlier time. The Fig Tree data yield an age of 2.98 ±.02 b.y. for a period of Sr-isotope homogenization, by either sedimentary diagenesis or later metamorphism. The data for the schists and acid lavas indicate ages of ~ 2.5 b.y., which are incompatible with either times of deposition, or recognized periods of metamorphic mineral growth, for these strata. They define the last time of Sr isotope homogenization; this may reflect widespread episodic heating (associated with the post-orogenic granite cycle) or cooling associated with regional uplift.The total-rock isochron technique has thus far failed to establish the age of the Swaziland System and factors responsible for this situation are discussed. Heterogeneous biotite-rich metamorphic rocks appear to be unsuitable for 'seeing through' the effect of superimposed metamorphisms, but may be suitable for dating of the metamorphisms.
The ages of stratified Precambrian rock sequences in central Arizona and northern Sonora
Authors: Livingston Donald E. , Damon Paul E.
Published: April 2011

Stratified sequences of Precambrian rocks from twelve localities in Arizona and Sonora yield geologic and isotopic evidence of multiple periods of rock accumulation and orogeny. Isotopic dating indicates that these rocks were formed from 1800 m.y. to 950 m.y. ago. The oldest rocks are metamorphosed sequences of volcanic and sedimentary origin. They are separated in time from a younger sequence of metamorphosed volcanic and sedimentary rocks by batholithic plutonism dated at approximately 1700 m.y. The second period of volcanism and sedimentation was terminated by batholithic plutonism about 1400 m.y. ago.Subsequent to the 1400 m.y. event, the "Younger Precambrian" rocks of Arizona, the Apache Group and probably the Grand Canyon Series, were deposited. These dominantly sedimentary rocks are characteristically only slightly and locally metamorphosed and deformed. Their age is greater than the 1150 m.y. old diabase sills and dikes that intrude them. Some areas that are not underlain by rocks of the Apache Group were metamorphosed and possibly intruded by silicic plutons about 1000 m.y. ago.From these data it appears that the stratified Precambrian rocks of Arizona can be assigned to three periods of accumulation. The first period occurred prior to about 1700 m.y., and the second occurred between 1700 and 1400 m.y. The third period, the deposition of the Apache Group, occurred between 1400 and 1150 m.y. ago.
Structural relations at the eastern margin of the Shuswap Complex, near Revelstoke, southeastern British Columbia
Authors: Ross John V.
Published: April 2011

Three major phases of folding affected rocks of Late Proterozoic and Early Paleozoic age and members long assigned to the Shuswap Complex of southeastern British Columbia. The main and first phase of folding produced a large recumbent anticline, having a northerly trend, overturned to the east, that contains an exotic wedge of granite-gneiss within its core. This gneiss was mechanically emplaced into the Late Proterozoic and Early Paleozoic sediments, and already had a metamorphic and deformational history prior to its emplacement. Its age is possible Hudsonian equivalent. Metamorphism during this recumbent phase of folding was greenschist facies.Phase 2 folding was accompanied by amphibolite facies metamorphism, and caused refolding of the earlier composite recumbent anticline into open folds along southeasterly axes.A third and final phase of folding, associated with waning metamorphism, gave rise to folds along southeasterly striking axial-planes that dip steeply to the northeast. Thus, phase three folds caused tightening-up of the previously formed folds.The absolute age of these deformations is not yet known, but the Shuswap Complex, at its eastern margin, is shown to include Paleozoic rocks and some older gneisses, possibly of Hudsonian age.
Evolution of the Slocan Syncline in south-central British Columbia
Authors: Ross John V. , Kellerhals P.
Published: April 2011

The Slocan Syncline, located in the center of the Kootenay Arc, south-central British Columbia, is outlined in its core by deformed Triassic sediments—the Slocan Group. These deformed sediments were originally deposited unconformably into a synform developed on the upward-facing limb of a recumbent, eastward-closing anticline, comprising Paleozoic and older rocks.The first phase of deformation resulted in the development of a recumbent anticline closing to the east. This anticline involved a sequence of rocks ranging in age from Windermere (late Precambrian—Horsethief Creek Group) up to Permian (Milford Group) and was originally developed along almost horizontal axes contained in an axial-plane having a shallow westerly dip. The core of this anticline contains granite gneiss, having a history pre-dating the deposition of the Horsethief Creek Group, which is in imbricate relation with the gneiss.Later, phase 2 deformation refolded this recumbent anticline into a synform and a westerly complementary antiform along shallow southeasterly axes contained within axial planes dipping southwesterly at about 45 degrees. Amphibolite-facies metamorphism (the "Shuswap Metamorphism") accompanied these phases of deformation and culminated in phase 2 time. Phase 1 and phase 2 deformation and metamorphism ate dated at post-Milford Group (Permian) and pre-Slocan Group (Triassic).Slocan Group (Triassic) sediments were deposited into the phase 2 synform, whose limbs consist of variable older rocks. A later non-metamorphic deformation, phase 3, along southeasterly striking axial planes dipping steeply to the northeast tightened the earlier phase 1 anticline and the phase 2 synform, and produced the Slocan Syncline. The Triassic sediments exhibit only phase 3 structures and are cut by the Nelson batholith dated at 171 × 106 years (Early Jurassic). Phase 3 deformation is then dated at post-Triassic and pre-Early Jurassic.Structural and stratigraphic evidence suggests that the phase 1 recumbent anticline herein described is but one of a set of nappes disposed structurally above and below the one presently described, and that the Kootenay Arc is an old structure perhaps resulting from interference of phase 1 and phase 2 deformations.
Low- to medium-grade metamorphism in silicate iron-formations of the Cape Smith Belt, New Quebec
Authors: Hashimoto T. , Béland R.
Published: April 2011

Four different assemblages of iron-rich silicates from the silicate iron-formation of the Cape Smith belt in New Quebec have been investigated. These rocks all contain quartz, magnetite, some calcite, and are composed mostly of two or more of the following silicates: stilpnomelane, minnesotaite, iron chlorite, grunerite, almandite, and biotite.From eight chemical analyses and petrographic examination, using a method developed by J. B. Thompson, an isothermal phase diagram of the system Al2O3–Fe2O3–FeO–MgO–SiO2–H2O has been constructed for the upper part of the greenschist facies of metamorphism.Speculation based on this diagram and on available experimental data is offered on the sequence of reactions leading to the assemblages observed, and on the possibility of finding mineral assemblages representing invariant points in metamorphosed iron-formations.
Structure and mobility of the crust and mantle in the vicinity of island arcs
Authors: Oliver Jack , Isacks Bryan
Published: April 2011

A detailed study of seismic wave propagation in the Fiji-Tonga region shows that there exists in the upper mantle an anomalous zone whose thickness is about 100 km and whose upper surface is approximately defined by the zone of seismic foci extending to depths of about 700 km. Attenuation of seismic waves within the zone is anomalously low and velocities are high. Other island arcs appear to be associated with similar zones.The anomalous zone in Tonga can be interpreted as the westernmost portion of a block of lithosphere that has been thrust, or dragged, or has settled beneath the island arc. Such mobility of the lithosphere suggests a key role in geotectonics for this layer of strength and raises a number of possible new solutions to long standing problems. For example, assuming that deep earthquake zones throughout the world are a measure of the amount of underthrusting during the last 107 years, an average rate of spreading over the entire worldwide rift system can be obtained as a check, but not a proof, of the hypothesis. The half-velocity obtained is 1.3 cm/year and is reasonable in light of current knowledge.
Continental margins of India
Authors: Narain Hari , Kaila K. L. , Verma R. K.
Published: April 2011

The results of the latest geophysical investigations on the continental margins of India carried out by various organizations are summarized and reviewed. A close examination of the findings to date suggests a possibility that the Chagos–Maldive Islands may continue northwards under the sea bottom up to Karachi along the western coast of India and form an arcuate volcanic ridge feature. From the present study it is revealed that the continental crust, which has a thickness of about 37 km over the Indian Peninsular shield, thins to about 15 km over Maldive Islands, finally changing westwards to oceanic crust of 6 km thickness. The Laccadive–Maldive Island region on the continental margins of India represents a transition zone from continental to oceanic crust. A volcanic ridge in the Andaman Sea is also indicated parallel to and east of the Andaman Nicobar sedimentary island arc joining the inner volcanic trend of Sumatra and the igneous belt of Burma.
Igneous structures and mechanism of emplacement of Mount Johnson, a Monteregian intrusion, Quebec
Authors: Philpotts A. R.
Published: April 2011

The Mount Johnson intrusion is a small vertical plug-like body belonging to the Monteregian hills. It consists of a sequence of rocks that grade imperceptibly from a core of olivine essexite to a margin of pulaskite. Past hypotheses explaining this differentiation have invoked the migration of early crystallizing phases to the center of the conduit up which the magma was flowing, and the diffusion of low-melting components to the cooler margins of the intrusion. However, a variety of depositional and erosional features in the well-layered rocks of this intrusion indicate that the first-formed rocks are at the margin of the intrusion and the youngest in the core.Experiments with a model in which two immiscible liquids convect in a vertical pipe suggest that the zonation from pulaskite at the margin to essexite in the core could result from the solidification of a converting magma column in which a syenitic liquid had separated from an essexitic one and floated to the top.
Isotopic composition of lead from Balmat, New York
Authors: Reynolds P. H. , Russell R. D.
Published: April 2011

Isotopic data obtained by means of gas-source mass spectrometric analyses of tetramethyllead are reported for rock and ore leads from Balmat, New York. On the basis of these new precise analyses (an uncertainty in measured isotope ratios of approximately ± 0.10% at the 95% confidence level), the Balmat ores were formed from lead isotopically of the type observed by Ostic et al. (1967) in certain conformable deposits. In a case where there is a low concentration of lead in the ore, contamination of the ore lead by lead from a rock system is apparent. The rock leads (from potassium feldspars and from marbles) form a short-period anomalous suite apparently derived from source material with a μ-value of about 8.75. This short-term development took place approximately 1100 m.y. ago. It is clear that the primary system postulated for the rock leads (μ = 8.75) is distinctly different from the one associated with the ores (μ = 9.0); hence the ore lead is not genetically related to the lead in the rock system. The apparent existence of two primary lead systems in the earth must be explained by any geophysical model that attempts to describe in general terms the evolution of lead isotope ratios.
Regional magnetic anomalies, magnetic units, and crustal structure in the Kenora District of Ontario
Authors: Hall Donald H.
Published: April 2011

Regional magnetic anomalies were smoothed from aeromagnetic maps in a part of the Superior Province of the Canadian Shield (latitudes 48°45′ to 50°00′ N; longitudes 93°30′ to 95°00′ W). It was found that anomaly lows lie over Keewatin greenstone belts, and highs over adjacent granitic areas.Surface mapping of magnetic susceptibility and NRM was combined with quantitative interpretation of the regional magnetic anomalies. It was found that, when considered regionally, magnetization lies primarily in the granitic bodies, with a continuous distribution from the surface down to the Intermediate (Conrad) discontinuity. Intensity of magnetization increases with depth, and is directed nearly along the direction of the present-day geomagnetic field.As an aid to the interpretation, a method of depth determination for deep crustal magnetic units with sloping sides is introduced, and one for variable intensity of magnetization with depth.
Measurement of polarity in oceanic basalt
Authors: Irving E.
Published: April 2011

The application of magnetic viscosity in basalts to the problem of determining the magnetic polarity of the ocean floors is discussed. Its usefulness is demonstrated by a test in which the polarity of 5 samples, chosen randomly from a collection of basalts, is predicted correctly. The polarity of a sample from the median valley of the Mid-Atlantic Ridge is determined as normal by this method.
Determination of optic axial orientation of uniaxial minerals and of dolomite using an ordinary microscope
Authors: Venkitasubramanyan C. S.
Published: April 2011

Schumann's method for determination of the orientation of the C-axis of uniaxial minerals using an ordinary petrographic microscope, described nearly thirty years ago, apparently has been generally overlooked in this country. It is simple, faster, and in certain cases more accurate than determinations using a universal stage.As an additional determination, since in dolomite the pole to the twin plane [Formula: see text] lies at [Formula: see text] to the C-axis, the orientation of the twin plane can be found if the attitude of the C-axis and the 'strike' of the twin lamella when the thin section is in a reference position are known. The method is not successful with calcite because [Formula: see text] is only 26°, leading to ambiguous answers for most orientations.
Ice distribution in permafrost profiles
Authors: Williams P. J.
Published: April 2011

Soil samples from deep drill holes in permafrost have been analyzed with particular regard to lithology and ice occurrence. The occurrence of moisture accumulation and ice lensing was found to be compatible with predictions from air intrusion tests on the soil materials. Regard is paid to the special geomorphological conditions at the drill sites, and to recent findings in laboratory research on soil freezing.
Scolecodonts from the Windsor Group (Mississippian) of Nova Scotia
Authors: Globensky Yvon
Published: April 2011

This first discovery of scolecondonts (worm jaws) from the insoluble residues of limestones from the Windsor Group (Valmeyeran–Chesterian) of Nova Scotia is represented by 8 genera. The genera Lumbriconereites and Stauronereisites are restricted to Subzone E. Scolecodonts are absent from the Lower Windsor strata.
Reaction of mixed magnesium–aluminum and calcium–aluminum hydroxides with Wyoming bentonite
Authors: Clark J. S. , Ross G. J.
Published: April 2011

Excess AlCl3 was reacted with Mg(OH)2 and Ca(OH)2 in suspensions of Wyoming bentonite and the nature of the reaction products formed and their effect on the cation-exchange capacity (CEC) of the clay was determined. Reaction of Mg(OH)2 and AlCl3 with the clay produced marked decreases of the CEC in the bentonite, whereas much smaller decreases were observed in the Ca–Al–clay preparations. The decreases in the CEC were attributed to the formation of mixed Mg–Al and Ca–Al hydroxide clay complexes. The greater stability of the mixed Mg–Al hydroxide complexes with the clay appeared to account for the marked reduction of CEC in these systems.
A re-examination of pseudoleucite from Spotted Fawn Creek, west-central Yukon
Authors: Tempelman-Kluit Dirk J.
Published: April 2011

New petrographic and chemical data for pseudoleucite from Spotted Fawn Creek and two new nearby localities in central Yukon Territory are presented and discussed in the light of recent experimental evidence on the origin of pseudoleucite. The petrologic, chemical, and experimental data suggest that natural pseudoleucite results from subsolidus breakdown of leucite under water pressure and that the space provided by this breakdown results in influx of the fluid phase that accomplishes partial removal of potash, enrichment in soda, and addition of water.
Gravity variations and precipitation
Authors: Luiz M.
Published: April 2011

The effects of gravity variations on precipitation are discussed. It is shown that the most probable time of rainfall may coincide with the time of maximum rate of change of the earth's gravitational field.
The geochemistry of an Arctic watershed
Authors: Macdougall J. Douglas , Harriss Robert C.
Published: April 2011

The clay mineralogy and elemental chemistry of soil and sediment samples from a small area of the Canadian Arctic Archipelago were examined. The clay mineralogy reflects a largely physical weathering regime. Some important results of the chemical analyses are: (1) Sedimentation rates of manganese in the Arctic near-shore sediments are similar to those reported for pelagic sediments from other oceans. Manganese in the Arctic sediments does not appear to be derived locally, the most likely source being water which originates in the North Atlantic. (2) Mineral-water reactions that occur during the transition from the terrestrial to the marine environment are limited to ion-exchange reactions. The potassium: rubidium ratio of the sediments is higher than that of the source-area soils. In contrast to findings in temperature and tropical areas, little or no boron is taken up by terrestrial clays as they enter the marine environment in the polar region studied. (3) New data are presented for mercury, palladium, and gold in near-shore sediments. The values found are 30, 2.1, and 2.7 parts per billion, respectively.
Magnetization of the Perry Formation of New Brunswick, and the rotation of Newfoundland: Discussion
Authors: Pearce G. W. , Freda G. N.
Published: April 2011

Statistical analysis of the data from Perry Sandstone collected at Blacks Harbour, New Brunswick, indicates that the resolution of two components of magnetization previously reported is not justifiable.
Foraminiferal distribution and sedimentary facies on the Grand Banks of Newfoundland
Authors: Gupta B. K. Sen , McMullen R. M.
Published: April 2011

The southern part of the Grand Banks can be divided into three sedimentary regions. The north western region is dominated by gravel-size material; this is probably a reworked glacial sediment and its limit may indicate the seaward edge of the Quaternary ice sheet. The other regions are both dominated by sand-size pro-glacial material reworked in post-glacial times. The southwestern region includes a large area of finer sediment, which shows the highest density of foraminiferal tests. Dominant lineations indicate the probable influence of the Labrador Current and the Gulf Stream in the distribution of sediments.On the Tail of the Bank, an inverse relationship is commonly present between the density of the benthonic tests and the grain-size of the sediment. Of the 88 species present in the benthonic assemblage, 31 occur in 30% or more of the stations and only 5 occur in more than 90% of the stations. Islandiella islandica (Nørvang) is the most abundant species. The distribution of the living/total ratio in the benthonic Foraminifera is erratic, but particular areas of significantly high or low ratios may be related to different rates of sedimentation. The distribution of the planktonic assemblage, dominated by Globigerina pachyderma (Ehrenberg), is apparently controlled mainly by the movement of the Labrador Current waters. The percentage of planktonic tests in the total foraminiferal population decreases sharply on the shallow plateau, inward from the edge of the Bank.
Provenance of the Upper Cretaceous Kneehills Tuff, Southern Alberta
Authors: Binda P. L.
Published: April 2011

The areal distribution of the coarse fraction of ten samples of the Kneehills Tuff indicates a southern provenance for the volcanic ashes that originated the pyroclastic deposit. The coarse index (arithmetic mean of the fifty largest diameters in a thin section) is a useful parameter for quick grain-size studies of indurated sediments.
Reasons for absence of a 'granitic' layer in basins of the South Caspian and Black Sea type
Authors: Rezanov I. A. , Chamo S. S.
Published: April 2011

A profile of deep seismic sounding across the South Caspian depression is described. The peculiarity of the structure of the depression is the reduced thickness of the Paleozoic and Mesozoic folded complexes, which is indicative of its geanticlinal development at that time. These complexes have seismic velocities in the range usual for granites. They were not discovered in earlier seismic studies in the Black Sea and Caspian Sea because the complexes are too thin, and the methods used did not allow discovery of detail. One peculiarity of these depressions is the so-called 'sedimentary-basaltic' crust. This arises when strongly metamorphosed rocks have been overlain by thick, poorly consolidated sediment, after a long period of submergence.
A recalculation of the age of the solar system
Authors: Cumming G. L.
Published: April 2011

A new method of fitting a straight line to experimental points with correlated errors has been used to recalculate the age of the solar system using several different radioactive decay systems. It is shown that the possibility of correlated errors should not be neglected in evaluating the errors in the slope of a straight line fitted to experimental points. It is also shown that in spite of the large body of data now available, the usually accepted value of about 4550 ± 50 m.y. is the best that can be justified by the data. Most of the uncertainty seems to be experimental in origin and could probably be substantially reduced by careful application of presently available experimental techniques.
Preliminary interpretation of the first refraction arrivals in Gaspé from shots in Labrador and Quebec
Authors: Rankin Douglas S. , Ravindra Ravi , Zwicker David
Published: April 2011

Previous work in the Gulf of St. Lawrence has yielded an unusually high upper-mantle compressional velocity. In the Gaspé area a more recent determination has yielded a value of 8.75 ± 0.20 km/s for an unreversed profile. The arrival time at a station on the north shore of the St. Lawrence River suggests that there is no major difference in velocity and depth relative to the south shore.
Sedimentation in Upper Arrow Lake, British Columbia
Authors: Fulton R. J. , Pullen M. J. L. T.
Published: April 2011

Two rivers, the Columbia and the Incomappleux, empty into the north end of Upper Arrow Lake. The form and the general pattern of sedimentation of the two river deltas were determined by an echo sounder survey.The three classical delta sedimentation zones were recognized and observations made on sedimentation in each. Sedimentation in the topset zone is largely channel and overbank deposition similar to that taking place on river floodplains. The bottomset zone receives fine silt and clay carried out to where it can settle under lacustrine conditions. The bulk of the sediment is deposited at the river mouths near the top of the foreset zone. Following initial deposition, the sand and silt dumped at the river mouths is carried into the lake basin by a slow sliding failure of the entire foreset zone.
An Upper Pliocene neohipparion from the Flaxville Gravels, northern Montana
Authors: Storer John E.
Published: April 2011

Neohipparion sp. from the Flaxville Gravel of Sheridan County, northern Montana, compares well with late Hemphillian species of Neohipparion in height of crown, shape of protocone, and development of pli caballin. A late Hemphillian age conflicts with the Barstovian or Clarendonian age suggested by Collier and Thorn's original evidence. The part of the Flaxville Gravel considered differs greatly in age from the nearby Wood Mountain Gravel of Saskatchewan, although it may be comparable in age with the Hand Hills Gravel of Alberta.
Inorganic origin of corrugated vermiform structures in the Huronian Gordon Lake Formation near Flack Lake, Ontario
Authors: Young G. M.
Published: April 2011

Early Proterozoic rocks of widely separated areas contain corrugated, spindle-shaped structures, which formerly were considered to be of organic origin. New evidence indicates that some of these structures have formed by both upward and downward injection of silt into fissures in a muddy sediment. The fissures are interpreted as shrinkage cracks formed beneath the sediment–water interface and may possibly indicate the presence of saline waters.
Glacier surges in West Spitsbergen
Authors: Liestøl Olav
Published: April 2011

Surges constitute a common form of glacier advance in Spitsbergen. The fastest movement observed is that of the Negri Glacier, with an advance of ~ 12 km in less than a year. Observations on the Finster-walder Glacier indicate that the ice flow is too small to maintain a steady-state slope. At intervals, of the order of 100 years, the glacier will balance this build-up by surging. A small surging glacier in the Dickson Valley has a sheet of refrozen meltwater in the front. This refrozen meltwater is possibly generated by the surge.
Contribution à la théorie des ondes glaciaires
Authors: Lliboutry Louis A.
Published: April 2011

Glacier surges may result (1) from the warming of a cold glacier, which follows an unusual snow cover, with the formation of a temperate basal layer, or (2) from the fact that two values of the sliding velocity correspond to a single value of the friction.The last results about the friction law obtained by the present author are summarized. As a rule, for increasing sliding velocities the friction goes through a maximum and next through a minimum. Thus for one value of the friction three values of the velocity, two stable ones and an unstable one, can exist.Since the derivative of the friction with respect to the sliding velocity may become negative, the coefficients c0 and D0 in the perturbation equation may become infinite (their ratio remaining finite), and next negative. By this way, when a flood wave runs down a glacier an area with a negative diffusion coefficient may appear. Then the profile of the wave is altered: it vanishes at the upper part of this area and swells beyond measure at the lower one. Factors which may limit the amplitude of this surge are pointed out.
Displacement and stress field along part of the Cobequid Fault, Nova Scotia
Authors: Eisbacher Gerhard H.
Published: April 2011

The east-trending Cobequid Fault separates pre-Carboniferous rocks of the Cobequid Mountains to the north from Carboniferous clastic rocks along the southern flank of the mountains. A detailed study of the fault zone revealed tie predominance of right-lateral displacements. The orientation of the stress field that existed during deformation along the fault trace was determined by the study of systematic fractures in pebbles within Carboniferous conglomerate. Maximum compressive stress was aligned in a NW–SE direction, being compatible with the orientation of the displacement vectors in the fault zone. Transcurrent movement along the Cobequid Fault occurred in late Pennsylvanian time and involved both Carboniferous and pre-Carboniferous rocks; total displacement is unknown.
Calc-alkaline volcanism and the thickness of the early Precambrian crust in North America
Authors: Condie Kent C. , Potts Mark J.
Published: April 2011

Geochemical and geophysical data indicate that the average potash content of young calc-alkaline volcanics increases in approximately a linear manner with crustal thickness. If such a relationship existed during the Precambrian, potash contents of early Precambrian ([Formula: see text] billion years) calc-alkaline volcanics in the Canadian Shield indicate that these volcanics were erupted onto a crust that was approximately 10–25 km thick. Since 3–13 km of these volcanics are now exposed, the total thickness of the early Precambrian crust prior to the Kenoran orogeny may have approached or reached presentday crustal thicknesses.