bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Production Measurement in Rocks using a Gamma Ray Spectrometer with a Solid State Detector
Authors: Lewis Trevor
Published: April 2011

A gamma-ray spectrometer with a solid state detector is described for routine laboratory measurement of U, Th, and K in rocks. The results are used to determine their average rate of heat production. The liquid-nitrogen cooled Ge(Li) detector is used in preference to the conventional NaI detector, even though its counting efficiency is much lower, because its much better resolution permits the isolation of low energy peaks. Using the spectrum obtained over the larger energy range, concentrations can be determined to the same accuracy as with the NaI detector in comparable times. Two analysis techniques were used: the first compares the sample's entire spectrum to those from standards. The alternative technique compares only the sharply resolved peaks measured above the continuum: the counting efficiency is reduced but the sample density can vary as long as a self-absorption correction is made. The results on four United States Geological Survey standard rocks are given.With such a system having a high resolution, the U concentration can be measured using the 63 kev gamma-rays produced in the decay of 234Th to 234Pa, thus indicating whether or not the U series is in equilibrium.
Normal Modes of the Bay of Fundy and Gulf of Maine
Authors: Garrett Christopher
Published: April 2011

Platzman's (1972) numerical scheme has been used to study the inviscid normal modes of the Bay of Fundy and Gulf of Maine for a variety of boundary conditions. The results support the contention that the resonant period associated with the lowest mode is greater than the M2 tidal period. Calculation of a damping rate from the inviscid solution gives a dissipative Q of 3.3 for the system, though this is probably an underestimate. Changes of period and normal mode shape due to changes in geometry at the head of the Bay of Fundy are investigated and some rather uncertain implications for tidal power development are discussed.
An Evaluation of the Provenance of Terrigenous Sediments from Offshore Vancouver Island
Authors: Carter Lionel
Published: April 2011

Modern sands and gravels from Barkley Sound, Vancouver Island, are mainly composed of igneous lithic fragments, present in sediments coarser than medium sand, and of andesine plagioclase, present in finer size fractions. Heavy mineral assemblages are dominated by hornblende, epidote, opaque minerals, and chlorite. This sediment mineralogy is mainly controlled by the composition of the source area, and to a lesser extent, by hydraulic processes of the depositional environment; effects of weathering at source and river transport are minimal. Sources include Mesozoic, eugeosynclinal basalts and andesites, late Mesozoic, post-geosynclinal granodiorite and diorite plutons, and Cretaceous to (?) late Pleistocene sediments which themselves were ultimately derived from the aforementioned igneous sources.Relict sands and gravels on the continental shelf adjacent to Barkley Sound, are similar in composition to the modern sediments and have been derived from similar igneous and sedimentary source rocks. However, relative to modern sands, relict sands have a greater variety of minor constituents, particularly heavy minerals, which in addition to hornblende, epidote, and opaque minerals, include garnet, orthopyroxene, and clinopyroxene. It is suggested the more varied mineralogy is due to: (1) a more extensive source area; and (2) introduction of additional sediment from outside the study area by modern bottom currents.
ALKHAL, a File of Information on Salt Systems with an Alkali Halide Component
Authors: Smith F. G. , Smith M. I. , Watson D. F.
Published: April 2011

A computer-accessible file of bibliographic data, on the liquidus of the class of inorganic salt systems that contains at least one alkali halide, is retrospective to 1875 and is being kept current relative to Chemical Abstracts Condensates tapes. The bibliographic data are in free text with some format restrictions for facilitating file management and translation to conform to other systems or computers.
A Study of Paleosols in the Saskatoon Area of Saskatchewan
Authors: Turchenek L. W. , St. Arnaud R. J. , Christiansen E. A.
Published: April 2011

Postglacial paleosols developed in lacustrine and aeolian sediments occur on terraces and in banks of the South Saskatchewan River near Saskatoon. At each of three sites a sequence of two paleosols was studied: a lower soil of immediate postglacial age as indicated by radiocarbon dates, that is buried by aeolian sands, and an upper one, located within the dune sands, that marks a period of stability of the dunes. Climatic fluctuations are inferred to be the cause of aeolian activity.One paleosol met the classification criteria for an Orthic Black Chernozemic soil. The other soils, particularly those developed in the dune sands, were weakly developed, Regosolic types of soils.Pedogenic interpretations were based on macro- and micromorphological observations as well as chemical characteristics. Micromorphology and the determination of calcite and dolomite distribution were particularly useful in differentiating sedimentary, pedogenic, and postburial alteration processes in the buried soil profiles. Studies of the organic matter suggest that it had changed markedly after burial.
Trace Metals in the Waters of the Gulf of St. Lawrence
Authors: Bewers J. Michael , Macaulay Ian D. , Sundby Bjørn
Published: April 2011

Concentrations of the trace elements iron, cobalt, nickel, copper, zinc, cadmium, and lead were measured in samples collected from the waters of the Gulf of St. Lawrence. Cobalt, cadmium, and lead occurred at or below the detection limits of the analytical method. The mean concentrations of nickel, copper, and zinc were 0.4 μgl−1. 0.6 μgl−1 and 1.8 μgl−1 respectively, and there was no evidence that local conditions influence their distribution. The distribution of dissolved and colloidal iron is related to dilution and precipitation processes which occur as fresh and saline waters are mixed. The particulate iron distribution is largely governed by water circulation patterns and settling.
Geophysical Studies of North African Cenozoic Volcanic Areas I: Haruj Assuad, Libya
Authors: Ade-Hall J. M. , Reynolds P. H. , Dagley P. , Mussett A. E. , Hubbard T. P. , Klitzsch Eberhard
Published: April 2011

This study is the first of a series in which a main concern will be to establish the Neogene absolute motion of the African Plate. A combined palaeomagnetic and K–Ar whole rock age dating study has been made of the Haruj Assuad basaltic volcanic area of central Libya. Seventy volcanic units, largely pahoehoe basaltic flows, were sampled in the north-central Haruj Assuad in an area centred on 27°45′ N, 017°30′E. Precisely defined paleomagnetic directions were obtained for 68 of the volcanic units and a weighted mean pole at 83°N, 171°E (δp = 5°, δm = 9°) obtained. This pole is just significantly different at the 95% level from the geographic pole. The difference between the paleomagnetic and geographic poles is thought to be largely the result of a degree of nonrepresentative sampling of the geomagnetic field. K–Ar radiometric age data indicate that volcanic activity in the Haruj Assuad area continued at least over the interval 6.0 to 0.4 my. The polarities of dated units are in agreement with the predictions of the time polarity scale. The ages of dated flows indicate that most of the flows presently exposed are younger than 2.2 my (i.e.) Upper Pliocene and younger. A scheme for assigning relative ages to groups of flows by degree of surface weathering is now calibrated in part with absolute ages.
Potassium–Argon Dating of Blueschists from Pinchi Lake, Central British Columbia
Authors: Paterson I. A. , Harakal J. E.
Published: April 2011

Geologic and radiometric evidence demonstrates that the Pinchi Lake blueschists underwent an early deformation, blueschist metamorphism, uplift, cooling, and a second deformation during the Triassic Tahltanian orogeny. Potassium–argon dates on phengitic muscovites from the blueschists (211, 214, 216, 218 ± 7 my) are considered to mark the close of the second deformation which was contemporaneous with or immediately after uplift and cooling of the blueschists during the Late Triassic.
The Petrology of Mesozoic Alkaline Intrusives of Central Newfoundland
Authors: Strong D. F. , Harris A.
Published: April 2011

Lamprophyre dikes occur as northeast-striking swarms and in radiating patterns around alkaline stocks. They range in age from Jurassic to Cretaceous and are interpreted as the result of the rifting associated with formation of the North Atlantic Ocean. They show strong evidence of coexisting immiscible silicate liquids, with leucocratic globules in a darker host matrix. The globules are richer in CO2 and Na2O than the host and these liquids are not similar in composition to those of other immiscible liquid pairs. The whole suite is interpreted to have resulted from high pressure eclogite fractionation followed by volatile build-up due to lower pressure fractionation of olivine, titanaugite, plagioclase, biotite, and/or kaersutite.
A Study of Relations between Rock Fabric and Joints in Sandstone
Authors: Reik G. A. , Currie J. B.
Published: April 2011

Significant relations are visible between properties of sedimentary rock fabric determined by microscopic and experimental study of sandstone and the pattern of jointing in these rocks where observed on structures in the field. Fine-grained sandstones in the Cardium Formation were studied in fold and fault structures along South Ram River in the central Alberta Foothills.X-ray diffraction determination of lattice-spacing in the quartz component of samples from the outcrop indicates that a state of residual elastic strain resides in grains comprising the rock fabric. The direction of relative compression in grains is parallel to regional trend of structure. Results of uniaxial compression experiments at low levels of strain, and of point-loading tests on discs cored from Cardium sandstone suggest a preferential orientation of microfractures parallel to this regional trend. These and other experimentally measured parameters of the rock fabric bear a direct geometrical relation to the pattern of joints observed and measured at various sites.These relations have importance for interpretation of jointing because they suggest how joint sets, though formed primarily during later stages of a tectonic cycle—during uplift and unloading of strata—have their directions influenced by earlier stages in that cycle, namely basin subsidence, sediment diagenesis, and initial tectonic loading. The relations observed in the present study also have importance wherever an understanding of joint patterns is a matter of economic importance. Two relevant examples are the interpretation of in situ stress measurements and the evaluation of fracture permeability in rock masses.
Phase Equilibria of Veins in Polycrystalline Ice
Authors: Langham E. J.
Published: April 2011

The permeability of ice layers in the snowpack can have far reaching effects on its response to meltwater or rain. This permeability is due to the presence of veins of liquid water at the junctions of the crystals. It is shown that the size of these veins is very sensitive to changes of temperature, air pressure, and dissolved air or other material.
Lherzolite Nodules in Basalts from British Columbia, Canada
Authors: Littlejohn A. L. , Greenwood H. J.
Published: April 2011

Lherzolite nodules in basaltic rocks from three localities in British Columbia include metamorphic tectonites and crystal cumulates. Chemical analyses show that trace element concentrations and distribution coefficients differ from suite to suite. Distribution of iron and magnesium between coexisting phases is regular and characteristic of each suite. Distribution of iron and magnesium between spinel and olivine indicates temperatures of last equilibration of approximately 840 °C for the cumulate nodules from Nicola Lake, 1085 °C for the tectonite nodules from Jacques Lake, and in excess of 1600 °C for the tectonite nodules from Castle Rock. The fabric of the tectonites is ([Formula: see text] girdle) with the γ-maximum perpendicular to the plane of layering or foliation.
Geology of the Northern End of Juan de Fuca Ridge and Sea-Floor Spreading
Authors: Barr Sandra M. , Chase R. L.
Published: April 2011

The northern end of Juan de Fuca Ridge consists of a series of basement ridges and valleys, inundated with sediment except for the axis of most recent sea-floor spreading. This axis is associated with the western of two branches of the Brunhes magnetic anomaly. The eastern branch of the magnetic anomaly is associated with a largely sediment-covered ridge, apparently produced by spreading early in the Brunhes Epoch. The intervening negative anomaly is probably caused by reversely magnetized rocks older than 0.7 m.y. Basalts dredged from the region of the northern end of Juan de Fuca Ridge have compositions typical of low-potassium ocean ridge basalts. They differ from basalts reported from the southern part of Juan de Fuca Ridge which have higher K2O, TiO2, FeOT, and FeOT/MgO. This difference is compatible with the hypothesis that a mantle plume exists under the southern part of the ridge. Distribution of earthquake epicenters suggests that the Queen Charlotte Fault Zone presently extends south of Explorer Ridge to intersect Juan de Fuca Ridge at 49°N and that the Sovanco Fracture Zone no longer functions as a transform fault.
Archean Rocks of Shoshonitic Affinities at Bijou Point, Northwestern Ontario
Authors: Smith T. E. , Longstaffe F. J.
Published: April 2011

The Archean volcanic and intrusive rocks of Bijou Point, northwest Ontario show several chemical characteristics which suggest affinities to the alkali or shoshonitic series characteristic of late stages of evolution in modern island arcs. The rocks have unusually high total alkalis (7% at 58–65% SiO2), high Al2O3 and high trace element contents (Ba 800–2500 ppm, Rb 50–350 ppm, Sr 600–2000 ppm). The presence of such rocks in the greenstone belts of the Superior Province serves to further emphasize the similarities between these ancient volcanics and their modern counterparts.
An Evaluation of Seismological Data Available for the Yukon Territory and the Mackenzie Valley
Authors: Leblanc G. , Wetmiller R. J.
Published: April 2011

The Yukon Territory and the Mackenzie Valley are known to be seismically active. In view of the proposed pipeline routes through this area, all seismological data available is carefully reviewed and evaluated for completeness and reliability. Three periods in the data set are distinguished: 1899–1960, 1961–1969, 1969–onward; for each, detection and location thresholds are established and uncertainties discussed. The results of a field seismicity survey conducted in the summer of 1972 are presented to confirm older seismicity patterns, suggest estimates on focal mechanism, and evaluate the previous performance of the Canadian Network.
40Ar/39Ar Dating of the Brighton Gabbro Complex, Lushs Bight Terrane, Newfoundland
Authors: Stukas Vidas , Reynolds Peter H.
Published: April 2011

A hornblende sample from this complex has an apparent 40Ar/39Ar age of 495 ± 5 my. The 40Ar/39Ar data was obtained in a stepwise outgassing experiment. If, as has been suggested, the Brighton complex represents Layer 3 of a former oceanic crust, then the latter was produced in this region about 495 my ago (that is, in the Lower Ordovician).
The Surficial Sediments of the Big Bay Section of the Bay of Quinte, Lake Ontario
Authors: Damiani V. , Thomas R. L.
Published: April 2011

Ninety-six samples of the uppermost 3 cm of sediment were taken from the Big Bay section of the Bay of Quinte. The samples were analyzed for grain size, Eh, pH, organic C, and inorganic C. The Big Bay section contains three depositional basins and has a mean depth of 4.7 m. The sediment distribution was mapped by conventional echosounding and showed that the coarser sediments, sands and gravels, occurred on the northern shore and in the eastern part of the study area, with clayey silts and silty clays offshore in the three depositional basins. This distribution was confirmed by the grain size analyses.The textural properties of the sediments, mean grain size, standard deviation, skewness, and kurtosis, are related to the variable mixing of three populations comprising gravel, sand, and silt/clay. Trends in the grain-size statistics related to sediment distribution suggested that the distribution observed is a result of increasing energy levels downwind under prevailing westerly and southwesterly winds.
Significance of Conodonts, Graptolites, and Shelly Faunas from the Ordovician of Western and North-Central Newfoundland
Authors: Bergström Stig M. , Riva John , Kay Marshall
Published: April 2011

Numerous collections of graptolites, conodonts, and shelly fossils provide new information about the age of several previously imprecisely dated formations on Newfoundland. The Long Point Formation is raised to group rank with two new formations, the Lourdes Limestone and the Winterhouse Formation. The Lourdes is largely Porterfieldian, indicating a pre-Nemagraptus gracilis Zone age for the Bonnian phase of the Taconian orogeny. In northern Newfoundland, the Nemagraptus gracilis Zone has been identified in the Lawrence Harbour Shale, and in shales along the Trans-Canada highway; the Diplograptus multidens Zone in argillites at the base of the Point Leamington Greywacke; the Dicranograptus clingani Zone in the same argillites, shales east of Gander Bay, the Rodgers Cove Shale, the Dark Hole Formation, and unit C of the Summerford Group; and the Pleurograptus linearis Zone in the Point Leamington Greywacke, unit C of the Summerford Group and the Rodgers Cove Shale. The Pygodus anserinus and Pygodus serrus conodont zones are present in the Cobbs Arm Limestone and the latter zone in the Summerford Group. The Cobbs Arm Limestone and the Rodgers Cove Shale (new) are referred to the Hillgrade Group. The conodont and graptolite faunas from north-central Newfoundland are of 'European' rather than 'North American' type, but the conodont and graptolite faunal provinces do not have the same regional distribution in eastern North America.
Paleomagnetic Results on Early Tertiary Lava Flows from West Greenland and their bearing on the Evolution History of the Baffin Bay–Labrador Sea Region
Authors: Athavale R. N. , Sharma P. V.
Published: April 2011

Paleomagnetic investigations have been carried out on about 250 oriented block samples collected from Early Tertiary lava flows representing an altitude span of about 1200 m on the Disko Island and 600 m on the Nûgssuaq Peninsula of West Greenland. The results reveal a record of two polarity transitions on the Disko Island and the existence of normal (N) and reverse (R) groups of lava flows on the Nûgssuaq Peninsula. A tentative correlation of the lava sequences from the two areas, on the basis of polarity of magnetization, has been suggested. Subject to the assumption of relatively uniform extrusion rates in northern Disko, a correlation of the comparatively thick sequence of reverse (R) polarity flows with the relatively long reverse epoch between the anomaly no. 25 (ca. 63 m.y.) and anomaly no. 24 (ca. 60.5 m.y.B.P.), has been attempted and an age estimate of the lava flows has been obtained.The Early Tertiary paleomagnetic pole for Greenland, computed from stable remanent magnetic directions of the Disko lavas is located at 67.5 °N and 165 °W. This pole position and the one for contemporaneous lava flows on the Baffin Island of Canada have been used in testing the models proposed by various workers for a paleogeographic reconstruction of Greenland and Canada, involving a closure of the Baffin Bay – Labrador Sea. The results of this paleomagnetic test suggest the existence of an ocean basin in the area, prior to the eruption of Early Tertiary lava sequences on Baffin Island and West Greenland, and also that this ocean basin had a much wider extent in Pre-Tertiary times.A model for the evolution of Baffin Bay – Labrador Sea has been suggested in the light of available geological/geophysical information about the region. It involves the opening of this sea in the Mesozoic and its partial closure during the Cenozoic as a consequence of the drift of Greenland in the northwesterly direction.
Preliminary Muskeg (Peatland) Inventory of the Province of New Brunswick
Authors: Korpijaakko Erkki O.
Published: April 2011

The distribution of peatland as a percentage of land area and the distribution of open and treed peatlands as percentages of peatland area have been determined for the Province of New Brunswick, For this work, aerial photographs, a dot planimeter, a mirror stereoscope and a computerized mapping procedure, SYMAP, in conjunction with the University of New Brunswick IBM system/360 computer were used. The results have been displayed in the form of symbolized computer printout maps (SYMAP) showing the distribution of peatland in New Brunswick. About 10% (about 700 000 ha) of the land area of New Brunswick is covered by peatland.
Determination of the Polarity of Unoriented Basalt Samples: A Test of the Anhysteritic and Natural Coercivity Spectra Comparative Method
Authors: Mohajer-Ashjai A.
Published: April 2011

Twenty specimens, from lavas in Oregon and Mull, have been used to test Irving's (1968) suggested method for determination of the polarity of unoriented dredged basalt samples. Polarity measurements were first made by independent workers, and the samples were provided following removal of orientation and identification marks. The natural remanent magnetism (NRM) of each specimen was first measured, demagnetized at 10 Oe intervals between 40 and 180 Oe (remeasuring being made after each treatment), and the operation was then repeated following the superimposition of anhysteritic remanent magnetism (ARM), by demagnetization in a peak field of 1400 Oe in the presence of a field of 0.5 G. Analyses of the resulting two coercivity spectra for each specimen produced the polarity predictions which were then compared to the independent polarity measurements. The results clearly show that the method is unsuccessful or doubtful as many times as it is successful, and therefore, cannot be considered reliable unless further research can isolate specimen characteristics which can be used to select material. In this experiment, however, no correlation exists between success or failure of the method and titanomagnetite sizes, and/or deuteric titanomagnetic oxidation index.
Additional Evidence of Pleistocene Ungulates from the Bow River Gravels at Cochrane, Alberta
Authors: Churcher C. S.
Published: April 2011

Bison occidentals (extinct western bison), Ovis canadensis (mountain sheep), and Equus conversidens (extinct Mexican ass) are represented by new specimens recovered since 1968. The bison is represented by four additional horn-cores, a third lower molar and other elements; the sheep by a manual proximal phalanx, and the horse by four lower cheek-teeth and postcranial material.
Structure of the Canadian Cordillera from Seismic Refraction and Other Data
Authors: Berry M. J. , Forsyth D. A.
Published: April 2011

A synthesis of Canadian Cordilleran refraction data recorded prior to 1971 with other geophysical data shows major features which correlate well with the regional geological structure. The wavelength of M topography decreases from about 200 km at 54°N to about 110 km at 52°N and culminates in a major lithospheric discontinuity east of Vancouver Island. The seismic data indicate the region of the Fraser River at Quesnel, the region immediately east of and parallel to the Coast Plutonic Complex and possibly the western edge of the Hazelton Mountains are sites of significant changes in lithospheric structure.Lateral variations in the average crustal density are necessary to reconcile both gravity and seismic data. The crust beneath the central, intermontane region is characterized by a mass deficiency, whereas the density of the crust beneath Vancouver Island appears greater than average.Calculation of synthetic record sections shows that the Pn phase may propagate considerably beyond crossover in a layer a few wavelengths thick. A model for the Canadian Cordillera which includes a low velocity layer as little as 8 km below the M appears plausible. Model calculations suggest that the M approximates a discontinuity beneath the Coast Plutonic Complex, but is better modelled as a transition zone beneath the Omineca Crystalline belt.
Origin and Emplacement of Acadian Granitic Rocks, Northern Cape Breton Island
Authors: Wiebe Robert A.
Published: April 2011

Acadian granitic rocks in northern Cape Breton Island consist entirely of even-grained leucocratic granodiorite and adamellite. The compositional range is small, and the average composition corresponds well with melts that could be generated in the crust. Abundant pegmatites in the contact zone suggest high water content.Within the major plutons these granitic rocks show: (1) high scatter on a Rb–Sr isochron (Cormier 1972), (2) apparently random areal variation in K and Ca, but a systematic areal variation in K/Rb and Ca/Sr, and (3) high scatter of Na2O and K2O on plots against differentiation index. The minor compositional heterogeneity indicated by these relations could have originated within the source region of melting or by assimilation during emplacement.The granitic plutons are elongate north–south and occur in an en echelon pattern within a NNE-trending migmatite zone. The spatial arrangement of pre-emplacement structures in the country rock and the distribution of xenoliths in the intrusions suggest that emplacement was accommodated by east–west expansion, upbowing of the surrounding country rock, faulting, and minor stoping.
Palynological Studies of Lake Sediment Profiles from Southwestern New Brunswick
Authors: Mott R. J.
Published: April 2011

Lake sediment cores from two lakes yielded pollen profiles which reflect vegetational and climatic changes since deglaciation. Radiocarbon dates from specific levels outline the chronology. Correlation of pollen zones between the two profiles indicate the degree of error in the anomalously old dates from one of the sites. Total absolute pollen frequencies are used to aid in interpretation.Following deglaciation a tundra environment prevailed until about 12 000 radiocarbon years B.P. This was followed by a transition zone in which Betula and Populus were abundant. About 12 000 years B.P. Picea increased markedly and remained a dominant part of the vegetation until 9500 years B.P. when Pinus and Quercus became prominent. Tsuga and various hardwood genera predominated after 6500 years B.P. An increase in Picea and decline in Tsuga and some hardwood genera produced the forests which prevailed when the area was settled.
Gravity and Deep Structure of the Continental Margin of Banks Island and Mackenzie Delta
Authors: Sobczak L. W.
Published: April 2011

Regional and deep structure supported by drill hole, gravity, and seismic evidence is interpreted along five profiles—one across the Mackenzie Delta and four across the continental margin. Isostatic compensation has reduced the gravity effect of most structures but gravity anomalies are still sufficient to outline two major sedimentary basins—one very extensive and thick (>10 km) underlying the continental margin and Mackenzie Delta and the other narrow and shallow east and southeast of the Arctic Coastal Plain. A basement ridge separating these basins along the eastern side of the Arctic Coastal Plain is outlined by a trend of relative gravity highs.An arcuate belt of prominent elliptically-shaped free air gravity highs (peak values >100 mgal) over the continental break outlines an uncompensated region of mass excesses. These mass excesses are explained by pro-grading wedges (>2 km thick) of Quaternary and possibly Tertiary sediments that have displaced seawater and act as a load on the crust rather than by the alternative concepts of an uncompensated ridge or high density material in the basement.
Tephrostratigraphy of Olympia Interglacial Sediments in South-central British Columbia, Canada
Authors: Westgate J. A. , Fulton R. J.
Published: April 2011

The Olympia interglacial sediments in the Interior Plateau region of British Columbia contain several thin, fine-grained rhyolitic and dacitic tephras, which undoubtedly represent the distal portions of widespread air-fall eruptive units. Successful discrimination of these tephras can be made by their mineral assemblage and composition of glass, magnetite and ilmenite, as determined by use of an electron microprobe; positive identification is not possible solely on the basis of field criteria such as coloration, degree of weathering, granulometry, thickness and stratigraphic position.Each tephra layer serves as a valuable time-parallel stratigraphic marker because of its regional extent and distinctive character. Those documented in this study include, in order of increasing age: Rialto Creek tephra, about 20 000 years old; Cherryville tephra, about 25 000 years old; Riggins Road tephra, about 30 000 years old; Duncan Lake tephra, about 34 000 years old; Dufferin Hill and Sweetsbridge tephras are probably close in age to Duncan Lake tephra; Kamloops Lake tephra is slightly older than 34 000 years; Mission Flats tephra is probably older than 35 000 years; Coutlee tephra is more than 37 000 years old; and the exact age of Okanagan Centre tephra is unknown. Such a detailed tephrochronological record should greatly facilitate geochronological and correlation studies of Olympia interglacial sediments in south-central British Columbia and adjacent areas of the Pacific Northwest.No definitive statement can be made at present on the identity of source volcanoes, but it is very likely that the commungtonite-rich tephras are derived from Mount St. Helens in Washington State.
Upper Cenozoic Glacial History South of the Grand Banks of Newfoundland
Authors: Piper David J. W.
Published: April 2011

A 10 m long piston core from a ridge on the continental rise south of the Grand Banks consists of foram-nanno ooze with several clay rich intervals. Microfossils and magnetic stratigraphy show that the upper part of the sequence is Brunhes in age, and disconformably overlies upper Pliocene sediments. Goethite micronodules are common just above the disconformity. Ice rafted coarse sand and granules are found in small amounts through the whole core, including the Pliocene section, but are more abundant in the Brunhes sequence. Most were derived from Labrador Sea bergs, but two or three red clayey intervals are associated with the advance of ice through the Laurentian Channel. Montmorillonite clays were transported to the area by the Western Boundary Undercurrent, which was also responsible for the early Pleistocene disconformity.
Variations in the Isotopic Composition of Volatilized Lead and the Age of the Western Granodiorite, Yellowknife, Northwest Territories
Authors: Cumming G. L. , Tsong F.
Published: April 2011

Large variations in the isotopic composition of Pb volatilized at different temperatures from rocks occur, and are linearly related. The line so obtained may be treated as a mineral isochron and interpreted in the same way as for the equivalent Rb/Sr case. For the western granodiorite at Yellowknife, we obtain a whole rock Pb/Pb age of 2675 m.y. and a series of mineral ages ranging from this upper limit down to about 2500 m.y. The whole rock age is in good agreement with other work and the range of mineral isochron ages is consistent with a cooling interval of about 150 m.y. as deduced by others. A comparison with other recent age determinations from the same area indicates that almost all the significant igneous activity and the emplacement of the ore minerals occurred in a very short time interval around 2650 m.y. ago.
The Unmetamorphosed Sedimentary Fill of the Brent Meteorite Crater, Southeastern Ontario
Authors: Lozej G. P. , Beales F. W.
Published: April 2011

A 10 000-ft (~3050-m) diameter circular structure that exhibits rimmed crater form, shock-metamorphic features, and underlying unbrecciated basement rocks occurs near Brent, Ontario, close to the southern margin of the Canadian Shield. In its center 863 ft (263 m) of Middle Ordovician sediments are preserved. Shortly after impact a nearly level crater floor was established and the subsequent sequence appears to have been deposited close to mean sea level. Repeated sediment laminae probably reflected wind-tidal marine incursions onto the low relief margin of the contemporary Ordovician epicontinental sea. Throughout much of its period of sediment accumulation, the crater floor appears to have been nearly flat. A 380-ft (115.8 m) sequence of dolostones, arkosic siltstones, and evaporite layers and veins formed within a breccia-rimmed depression. Initially sea water carrying fine silt invaded the crater and refluxed through the porous and permeable crater rim. Subsequently some 100 ft (30.5 m) of silty arkose blanketed the area, probably resulting from further transgression of the Middle Ordovician seas and breaching of the crater walls. An upper 380 ft (115.8 m) of predominantly thin-bedded lagoonal and shallow shelf sea limestones are divided into upper and lower sequences by a middle regressive set of red beds.The implied near-flat crater floor, coupled with preservation of over 800 ft (>244 m) of crater sediments, suggests continued slow subsidence. Earlier on, this subsidence affected only the crater area, but later episodes of subsidence were regional, involving Ordovician, Silurian, and Devonian sedimentation. The superincumbent load further compacted the total crater sequence. Preservation of the rocks described here is due to final depression of the sequence into a position below the general level of the surrounding Precambrian terrain. If Brent can be considered to be a typical peri-marine meteoritic impact crater, all such craters should have in common an inward-dipping succession of open-circulation sediments overlying a crater-rim restricted sedimentary sequence, which in turn overlies a shock-metamorphosed series of breccias.Compaction of the impact-generated breccias and subsequent unmetamorphosed crater-filling sediments influenced both sediment accumulation and the ultimate crater structure.
Revision of the Fossil Horses from the Cypress Hills Formation (Lower Oligocene) of Saskatchewan
Authors: Russell Loris S.
Published: April 2011

Seven species of the equid genus Mesohippus have been recognized in the Cypress Hills fauna, all based on isolated cheek teeth. Additional teeth collected in recent years permit a reduction to four species: M. westonii (Cope), small size, vestigial hypostyle; M. propinquus Lambe, small size, prominent hypostyle; M. stenolophus Lambe, medium size, prominent hypostyle; M. assiniboiensis Lambe, large size, well developed hypostyle. The species M. praecocidens Lambe and M. planidens Lambe are regarded as undeterminable. The specimen identified by Lambe as M. brachystylus Osborn may belong to M. stenolophus.
Chemistry and Differentiation of Mafic Dikes in an area near Fiskenaesset, West Greenland
Authors: Rivalenti Giorgio
Published: April 2011

In the Fiskenaesset region (West Greenland), there are three generations of postorogenic doleritic dikes of tholeiitic affinity. Two types of differentiation are evident: (a) laterally from the contacts to center and vertically, with the upper centres of the youngest generation of dikes attaining an andesitic or rhyolitic composition; and (b) between the different generations of dikes.Major and trace element geochemistry and calculations of the cumulus composition indicate that the differentiation within dikes is due not to flow, but to a shallow crustal fractionation of an olivine tholeiite magma. The differentiation between the various generations is attributed to fractionation of an olivine tholeiite magma during its upward displacement from a deep crustal magma chamber.
Lithostratigraphic Framework and Unified Nomenclature for Silurian and Basal Devonian Rocks in Eastern Gaspé Peninsula, Québec
Authors: Bourque Pierre-André
Published: April 2011

A unified stratigraphic nomenclature is proposed for Silurian and basal Devonian rocks in the eastern half of Gaspé Peninsula. The Gascons, West Point and Indian Point Formations of the Chaleurs Bay Synclinorium are extended into the northern part of Gaspé Peninsula. The term St. Léon is restricted to a sequence of mainly fine-grained sediments in which neither the West Point nor the Bouleaux is recognized. The term Lefrançois is abandoned. New lithostratigraphic units here proposed are the Anse à Pierre-Loiselle Formation in the Chaleurs Bay Synclinorium, the Ruisseau Bleau Formation and the Lac McKay Member of the St. Léon Formation in the Mount Alexandre Syncline, and the Ruisseau Louis Member of the St. Léon Formation in the Saint-Jean River Anticline and Mount Alexandre Syncline.
Acadian Slaty Cleavage Noncoplanar with Fold Axial Surfaces in the Northern Appalachians
Authors: Stringer P.
Published: April 2011

The Acadian orogeny though polyphase produced a single generation of folds and a single generation of slaty cleavage over wide areas of the northern Appalachians. Acadian slaty cleavage noncoplanar with fold axial surfaces is more widespread than has hitherto been recognized-Published examples from several areas are quoted. Cleavage coplanar with the axial surface in one part of a fold may transect the axial surface and both limbs elsewhere in the fold, and the time relations to folding are implicitly the same. Geometric relationships of regional Acadian slaty cleavage to axial surfaces of associated folds in Silurian sediments in northeast New Brunswick are described. Slaty cleavage is superimposed upon the folds whether coplanar or noncoplanar with axial surfaces. Convergent fans and refraction of the noncoplanar cleavage indicate compression later than the cleavage. Total shortening of Silurian strata is a combination of folding and of superimposed compression accompanying and succeeding initiation of regional slaty cleavage. A possible origin of the noncoplanar Acadian structures resulting from décollement of Silurian sediments upon Ordovician basement is discussed.
The Mugford Group Volcanics of Labrador: Age, Geochemistry, and Tectonic Setting
Authors: Barton Jr. Jackson M.
Published: April 2011

The Mugford Group is a sequence of volcanic and sedimentary rocks exposed within the Khaumayät (Kaumajet) Mountains of Labrador. Separated from an intensely deformed and deeply eroded Archean basement complex by an angular unconformity, these rocks are nearly everywhere flat-lying and only locally altered. The volcanic rocks within the Mugford Group are of three types: tholeiitic basalts, komatiitic basalts and greenstones. A phosphorus fractionation diagram indicates that the tholeiitic and komatiitic basalts may be differentiates of a common magma. The greenstones, however, have undergone a separate crystallization history, but plot within the field of tholeiitic basalts on a FMA diagram, suggesting they were originally tholeiites. K–Ar whole-rock ages show that the Mugford volcanics are at least 1490 m.y. old. Rb–Sr whole-rock isotopic analyses of the tholeiitic and komatiitic basalts and the greenstones define an isochron of 2369 ± 55 m.y. with an initial 87Sr/86Sr ratio of 0.7033 ± 0.0002. This age is interpreted as approximating the time of extrusion of the Mugford volcanics. The low initial 87Sr/86Sr ratio indicates that the magmas giving rise to these rocks were not appreciably contaminated with older crustal material.The Mugford volcanics are presently the oldest recognized continental flood basalts. Their extrusion apparently occurred contemporaneously with the intrusion of the Okhakh granite at Okhakh (Okak) Harbour, 25 km to the south. This suggests that while no regional metamorphism accompanied extrusion of these volcanics, some local igneous activity did occur at that time. The Mugford volcanics may represent the extrusive equivalents of numerous basic dikes that were intruded during the final stages of stabilization of the North Atlantic craton.
Mercury in the Sediments of the Gulf of St. Lawrence
Authors: Loring D. H.
Published: April 2011

In sediments collected from the Saguenay fjord, the St. Lawrence estuary, and open Gulf of St. Lawrence, total mercury varies with sediment texture and location from 10 to 12 300 ppb (average 386 ppb). The highest concentrations occur in the Saguenay fjord (average 2980 ppb) and the lowest in the open Gulf of St. Lawrence (average 150 ppb). The concentration of mercury increases with decreasing grain size, the highest concentrations occur in the fine-grained sediments of the submarine troughs and shelf valleys and the lowest in the sandy shelf sediments. Analyses of the sediments from the Saguenay fjord, where mercury values range from 12 300 ppb at its head to > 500 ppb in the lower reaches, indicate that most of the mercury (70 to 90% of the total) is held by the organic matter in the sediments. The distribution of mercury in the fjord is apparently controlled by the downstream dispersal from local industrial sources of mercury-rich organic matter, most likely of terrestrial origin because of its high C/N ratio. In the St. Lawrence estuary where mercury values range from 30 to 950 ppb, and in the open Gulf where correlations between variables are lower and scattered anomalies exist, analyses indicate that mercury accumulates along with the fine-grained inorganic and organic matter in response to the present depositional processes. The distribution of mercury appears to be controlled by the sedimentation pattern. Terrestrial organic matter and industrial waste originating in the Saguenay drainage area have the strongest influence on its distribution.
The Origin of Foliation and Lineation in the Onaping Formation and the Deformation of the Sudbury Basin
Authors: Rousell D. H.
Published: April 2011

A penetrative secondary foliation and lineation, defined by tectonically flattened and elongated fragments, are present in the Onaping Formation of the South and East Ranges of the Sudbury Basin. These elements formed not by shearing, as previously supposed, but by flowage such that maximum shortening was normal to the foliation and maximum extension was parallel to the lineation. The basin was deformed by a 'push' from the southeast and the forward motion at the surface exceeded that at depth. This caused extensive flowage, tectonic thickening and folding in the Onaping Formation, and uplift and rotation of the South Range. The deformation intensity decreased rapidly to the northwest, so that near the basin axis the rocks yielded by folding, while in the North Range the only vestige of the deformation is a local and weak foliation.Quartz grains in the Onaping Formation are generally recrystallized and the lack of a crystallographic preferred orientation suggests post-tectonic annealing recrystallization related to a thermal event. Locally, some of the rocks escaped recrystallization and the quartz c axes lie on a girdle about the maximum principal stress direction. A late episode of brittle deformation developed joints and formed new faults and reactivated pre-existing faults. The Sudbury Basin was less elliptical than its present form, but it is unlikely that it was ever circular.
Tertiary Basalts Dredged From Baffin Bay
Authors: Clarke D. B.
Published: April 2011

Three dredge hauls were recovered from scarps on the West Greenland continental shelf in Baffin Bay. Two of the dredge hauls consisted essentially of basalts but the third, at the mouth of Disko Bay, contained some 50% Precambrian erratics. Both the mineralogy and chemistry of these offshore rocks are very similar to the most evolved basaltic compositions found elsewhere in the West Greenland Tertiary volcanic province. The dredged samples show none of the features expected for submarine tholeiites and were therefore probably erupted subaerially and later subsided below present day sea-level. A petrogenetic model, involving equilibration of a basaltic magma at a pressure in the range 5–8 kb, is proposed to account for the chemistry of this suite of rocks.
Jansaella ridingi, nouveau genre d'Algue? dans le Dévonien de l'Alberta
Authors: Mamet B. , Roux A.
Published: April 2011

This note deals with the taxonomic description and botanical affinities of a new tubular calcareous Incerta Alga (Chlorophycophyta?). A comparison with the Moscovian Uraloporella.
Fluvial Sedimentation in Southern Ontario
Authors: Dickinson W. T. , Scott A. , Wall G.
Published: April 2011

Suspended sediment data for Southern Ontario stream have been analyzed with regard to areal and temporal patterns, characteristics of sediment concentrations, and relationships between sediment loads and watershed parameters. The range of annual suspended sediment yields for seven river basins is determined as 5250 to 175 000 kg/year/km2. The daily suspended loads exhibit highly skewed frequency distributions, with mean loads being equalled or exceeded less than 20% of the time and 50% of the annual load occurring during the months of March and April. It is demonstrated that sample loads collected during periods of low flow, and stream rankings determined from low flow data, are not indicative of the annual suspended sediment load picture. No simple model between suspended loads and such basin indices as relief ratio and drainage density is found to be satisfactory for prediction purposes.
Timing of Kenoran Metamorphism in the Eastern Abitibi Greenstone Belt, Quebec: Evidence From 40Ar/39Ar Ages of Hornblende and Biotite From Post-Kinematic Plutons
Authors: Dallmeyer R. D. , Maybin A. H. , Durocher M. E.
Published: April 2011

The Opemisca and La Ronde Lake plutons are typical of post-Kenoran felsic plutons which intrude the Archean greenstone terrane of the eastern Abitibi orogen. Hornblendes from the plutons record undisturbed 40Ar/39Ar release spectra with total-gas ages of 2692 ± 30 and 2656 ± 30 m.y. (Opemisca) and 2650 ± 30 and 2623 ± 30 m.y. (La Ronde Lake). Two additional K–Ar ages of 2653 ± 64 and 2647 ± 61 m.y. have been determined for hornblendes from the Opemisca intrusive. Release spectra of biotite from the La Ronde Lake pluton are also undisturbed but define discordantly younger total-gas ages of 2544 ± 30 and 2559 ± 30 m.y. These are similar to a 2505 ± 30 m.y. 40Ar/39Ar total-gas age for biotite (undisturbed spectra) from the pre-Kenoran Opawica River pluton located immediately south of La Ronde Lake.It is suggested that the hornblende dates are close to the actual time of intrusion of both plutons. This range in age is similar to that of other post-kinematic plutons in the eastern Abitibi belt and suggests that Kenoran metamorphism must have occurred prior to ~2650–2700 m.y. Available age determinations for pre-kinematic plutons within the area are slightly older (~2780–2820 m.y.), and a bracket on the time of Kenoran metamorphism between 2650–2700 m.y. and 2780–2820 m.y. is defined.The 40Ar/39Ar biotite ages are similar to published K–Ar biotite ages (~2500–2550 m.y.) in the eastern Abitibi belt and are interpreted as dating the time during post-Kenoran metamorphic cooling when temperatures dropped below those required for argon retention in biotite.
Rubidium–Strontium Mineral Ages and Polymetamorphism at Sudbury, Ontario
Authors: Gibbins Walter A. , McNutt R. H.
Published: April 2011

Consistent rubidium–strontium ages, calculated using mineral–whole rock pairs from the Sudbury area, confirm: (1) the Sudbury event (1900 Ma), (2) the Penokean (Hudsonian) Orogeny (1600–1800 Ma), (3) a cryptic (Elsonian) thermal event (1300–1450 Ma) and (4) the Grenville Orogeny (900–1200 Ma). Rubidium–strontium whole rock isochrons independently define these same events, as do other radioactive decay schemes and conventional geologic studies. The presence of the Kenoran Orogeny (2500–2700 Ma) and pre- to syn-Nipissing diabase folding and faulting (2150–2300 Ma) can be inferred from geologic mapping and radiometric studies in adjacent areas.