bluuebunny/crossref_metadata_2025 huggingface dataset:
A relationship between fecundity, survival, and the operation of crassulacean acid metabolism in Talinum triangulare
Authors: Taisma María Angélica , Herrera Ana
Published: April 2011

In plants of the perennial, deciduous herb Talinum triangulare, crassulacean acid metabolism (CAM) is induced by drought; therefore, CAM may be an adaptation to water deficit in this species. The present study was undertaken to determine the effects of water deficit on fecundity and CAM in plants of T. triangulare. Plants were grown from seed in the greenhouse and the life table was constructed with dynamic cohorts. CAM was induced by drought in plants as young as 45 days old, and its induction was associated with a significant rise in fecundity; values of survival beta mean fecundity by age-class were 30-50% higher in plants subjected to drought than in control plants due to a rise in fecundity. Plants subjected to drought produced more and lighter seeds, which germinated faster than their watered controls. These characteristics could be advantageous for a colonizing species such as T. triangulare. Plants obtained from the germination of seeds of plants subjected to drought did not show higher values of nocturnal acid accumulation when subjected to drought than the droughted offspring of watered plants but they showed higher survival and an earlier and higher reproductive effort than plants obtained from the germination of seeds of watered plants. The fact that values of survival beta mean fecundity were higher in plants subjected to drought than in watered plants suggests, within the context of the life history, that characters associated with the CAM syndrome may be adaptive.Key words: fitness, inducible CAM, life table.
Growth and virulence of Ceratocystis rufipenni and three blue-stain fungi isolated from the Douglas-fir beetle
Authors: Solheim Halvor , Krokene Paal
Published: April 2011

Blue-stain fungi were isolated from the Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, and from Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, colonized by the beetle. Growth of the three most commonly isolated blue-stain fungi (Leptographium abietinum (Peck) Wingfield, Ophiostoma europhioides (Wright & Cain) Solheim, Ophiostoma pseudotsugae (Rumbold) von Arx), and Ceratocystis rufipenni Wingfield, Harrington, & Solheim, an important associate of the spruce beetle, Dendroctonus rufipennis (Kirby), was studied in sapwood and phloem of live Douglas-fir trees, on malt agar, and on malt agar under oxygen-deficient conditions. The two Ophiostoma species grew better in the phloem and induced longer phloem necroses than the other fungi. Ceratocystis rufipenni and O. europhioides grew better in the sapwood and induced deeper sapwood occlusion. All fungi were relatively fast growing on malt agar, with O. pseudotsugae growing fastest and L. abietinum, slowest. Growth of C. rufipenni and O. europhioides was inhibited less by low oxygen levels than the other fungi, and this may explain why these two fungi were better able to colonize live sapwood.Key words: Ceratocystis rufipenni, Dendroctonus pseudotsugae, Douglas-fir, Leptographium abietinum, Ophiostoma europhioides, Ophiostoma pseudotsugae.
Tropical grasses vary in their resistance to Striga aspera, Striga hermonthica, and their hybrids
Authors: Kuiper Eric , Groot Alexia , Noordover Esther CM , Pieterse Arnold H , Verkleij Joe AC
Published: April 2011

The genus Striga contains some of the most damaging parasitic plant species of the world, and it causes large problems in agricultural systems of Africa and Asia. Effective, cheap, and easy applicable methods for Striga control do not yet exist. One method with great potential may be the use of resistant crops. However, resistant crops are not widely available, hence, these genetic traits will have to be obtained from another source. Here we report the results of a screening in which it is shown that several native African savannah grass species possess a high level of resistance to Striga hermonthica (Del.) Benth., Striga aspera (L.) Kuntze, and interspecific hybrids of these two Striga species. This trait could be of potential value for the development of resistant crops. Resistance to Striga was not expressed at the levels of germination and attachment. Root exudates of all 14 grass species tested induced Striga seeds to germinate. Furthermore, attachment to the host roots was always observed. Subsequent development of the Striga seedlings, however, was absent or heavily impaired in resistant grasses. Preliminary observations suggested that the parasite could not breach the endodermal barrier of the roots. The host range of interspecific hybrids of S. aspera and S. hermonthica appeared to be a combination of the host ranges of their parents. They could not attack grass species that were resistant to both parents.Key words: Striga aspera, Striga hermonthica, interspecific hybrids, germination, attachment, tropical grasses, resistance.
Reproductive biology in two Genisteae (Papilionoideae) endemic of the western Mediterranean region: Cytisus striatus and Retama sphaerocarpa
Authors: Rodríguez-Riaño Tomás , Ortega-Olivencia Ana , Devesa Juan A
Published: April 2011

We studied the reproductive biology of two leguminous shrubs endemic of the western Mediterranean region Cytisus striatus (Hill) Rothm. and Retama sphaerocarpa (L.) Boiss. The former is polliniferous, and the latter is nectariferous, with maximum nectar production at the earliest hours of the morning. Germination of the pollen grains in the flowers of the two species occurs only after rupture of the stigmatic surface. It is also necessary in both cases that pollinators (mainly Apis mellifera) visit the flowers for fruit and seed set to occur. A study of the pollen-pistil interaction indicated that there exists prezygotic self-incompatibility in these two species, probably of the gametophytic type, but some self-pollen tubes escape this control and self-fertilize some ovules. However, after hand self-pollination, fruit and seed set is very low for both species. This suggests the existence of a postzygotic rejection mechanism, which could be due either to the existence of late-acting self-incompatibility or to an early action of inbreeding depression, although there are lines of evidence that seem to point to the second possibility. Hand cross-pollination led to an increased number of fruit and seeds per plant relative to the control plants, indicating that reproduction is pollen limited.Key words: late-acting self-incompatibility, prezygotic self-incompatibility, fruit set, seed set, inbreeding depression, Spain.
Three new scapose species of Vernonia Schreb. (Asteraceae, Vernonieae) from Angola
Authors: Ortiz Santiago
Published: April 2011

Three new species from Angola are described: Vernonia lainzii, Vernonia longibracteata, and Vernonia platyseta (Asteraceae, Vernonieae). Morphological differences with putative related taxa are detailed and discussed. Vernonia lainzii is most similar to V. antunesii O. Hoffm., from which it can be distinguished largely on the basis of leaf pubescence, phyllary morphology, and pappus color and morphology. Vernonia longibracteata is most similar to V. thodei E. Phillips and V. praemorsa Muschl., from which it can be distinguished largely on the basis of degree of branching of the scape, leaf pubescence, petiole length, phyllary size and morphology, and outer pappus length. Vernonia platyseta is most similar to V. anandrioides S. Moore and V. longipedunculata De Wild. It can be distinguished from the former principally on the basis of habit type, leaf pubescence, involucre width, phyllary morphology and texture, and pappus morphology, and from the latter principally on the basis of habit type, involucre width, phyllary morphology, and pappus length.Key words: Asteraceae, Vernonieae, Vernonia, new species, tropical Africa, Angola.
Stem chemical compositions of juvenile Elaeagnus and Alnus species
Authors: Chow Poo , Rolfe Gary L , Bajwa Dilpreet S
Published: April 2011

Four-year-old plantation-grown autumn olive (Elaeagnus umbellata Thunb.) and black alder (Alnus glutinosa L.) trees were analyzed for gross heat value, ash, alcohol-benzene extractives, hot-water extractives, 1% NaOH extractives, lignin, and pentosan. These plantations were established on marginal land that was not suitable for food production in Illinois. For comparison purpose, lumber from 60-year-old black alder trees was also analyzed. Test results indicated that the planting sites (bottomland vs. upland) factor did not affect the chemical composition of both trees. The main factor, species, was significant in determining various chemical properties. Black alder had higher average alcohol-benzene extractives, 1% NaOH extractives, pentosan, ash, and gross heat content than autumn olive. Autumn olive had higher hot-water extractives, lignin, holocellulose, and alpha-cellulose content than black alder. The commercial alder lumber had less chemical extractives but was higher in alpha-cellulose than the 4-year-old black alder trees. Based on the chemical compositions, these two juvenile, nitrogen-fixing deciduous species could serve as a raw material source for chemical and paper industries, as well as for energy or fuel.Key words: Alnus, chemicals, Elaeagnus, extractives, short-rotation trees, utilization.
Linking ocean and continental records of paleoclimate: determining accord and discord in the records
Authors: Rack Frank R , Rutter Nathaniel W , Bush Andrew , Rokosh Dean , Ding Zhongli
Published: April 2011

Climate forcing at Milankovitch and sub-Milankovitch frequencies are evaluated by linking climate proxy data from terrestrial and ocean records at two scales of temporal resolution: (1) relatively coarse resolution over the last 500 ka, and (2) higher resolution over the last 200 ka. We determine that climate proxy data from Hole 810C represent regional atmospheric and oceanic processes by comparison to core V21-146, both from the northwest Pacific Ocean. We then compare records that represent regional deposition from China and the western Pacific Ocean to focus on determining Milankovitch-type periodicities. Grain-size and magnetic susceptibility data from Hole 810C and Baoji, China are contrasted using a time-sensitive wavelet analysis. The analyses indicate a general correspondence to Milankovitch frequencies, although there is no specific frequency that dominates throughout the records. Additionally, the dominant 100 000 year frequency does not occur at the same time in the records. These factors suggest that differences in the physical mechanisms of deposition may influence the preserved apparent periodicities in these environments. Lastly, climate events over the last 200 000 years in marine and terrestrial records are correlated at a high resolution in the depth domain. The last interglacial-glacial boundary is consistently placed at the base of a cold period (C20) in the terrestrial and marine records. However, the cold period in the ocean data (δ18O) is very subdued relative to terrestrial records. Additionally, over the last 200 ka, periods of minimum insolation intensity do not correspond linearly to periods of maximum grain-size and ice volume variations revealed in the loess and ocean records, respectively. However, during the warm interstadials of the last two glaciations, peaks in insolation intensity compare favourably with the times of strongest pedogenic development in the continental records and minimum ice volume in the ocean records.
A synthesis of electromagnetic studies in the Lithoprobe Alberta Basement Transect: constraints on Paleoproterozoic indentation tectonics
Authors: Boerner D E , Kurtz R D , Craven J A , Ross G M , Jones F W
Published: April 2011

Electromagnetic surveys of the crust and upper mantle underlying the Western Canada Sedimentary Basin have revealed two conductivity anomalies that are arguably related to Paleoproterozoic tectonic processes, recording a signature diagnostic of euxinic (foreland?) basin succession and perhaps defining a deep-marine transtensional basin. As well, a regionally pervasive electrical anisotropy throughout the crust crosses Proterozoic tectonic boundaries and is aligned in many areas with the regional tectonic fabric (as expressed by aeromagnetic data) created during the final stages of Proterozoic tectonic assembly of western Laurentia. There is also an order of magnitude increase in the upper mantle conductivity underlying Churchill Province Archean crust relative to that underlying the neighbouring Proterozoic crust. The interpretations of the electromagnetic observations are analogous with the Tertiary to modern-day tectonic development of southeast Asia. The foreland basin succession would reflect the closing of the South China Sea and the deep-marine basin may be analogous to the Andaman Sea and North Sumatra basin. Electrical anisotropy may be indicative of the successive lateral accretion of oceanic crust beneath the continental shelf followed by shortening. The enhanced mantle conductivity mechanism is unknown, although it may be associated with metasomatic modification of the subcontinental lithosphere subsequent to collisional thickening and followed by delamination or convective removal of some lithosphere. While the Indo-EurasianLaurentia tectonic analogy is incomplete, it is sufficiently compelling in explaining the electromagnetic and other data that it is a useful basis for understanding the Proterozoic assembly of Laurentia.
THE GEOLOGY OF THE NEW QUEBEC CRATER
Authors: Currie K. L.
Published: April 2011

The New Quebec Crater is a circular depression in the acid Archaean gneisses of northern Quebec, about 2 miles in diameter and 1 300 ft deep. The crater is roughly bowl-shaped, with a prominent rim elevated 300 to 500 ft above the surrounding barrens. The rim structure is a relatively recent deformation resulting in systematic outward dip of rock sheeting, and radial distribution of other curviplanar structural elements. Rocks of the rim are strongly mineralized with epidote and hematite, and are altered to sericite. These minerals are not found in the same rock units outside the rim. Glaciation of the rim appears to have removed little or no material. No evidence of impact was found.The crater may have arisen either by extraterrestrial impact or by volcano-tectonic collapse. The impact theory is implausible because of absence of distinctive criteria of shock and failure to explain the characteristic structure and mineralization of the crater. The volcano-tectonic hypothesis explains the structural and petrographic evidence but appeals to a type of volcanism not presently observed in active volcanic areas. Geophysical measurements are not likely to resolve the dilemma. The diagnostic evidence lies in the rocks hidden beneath the crater, concealed by 800 ft of water.
ADDITIONAL HEAT FLOW DETERMINATIONS IN THE AREA OF MOULD BAY, ARCTIC CANADA
Authors: Paterson W. S. B. , Law L. K.
Published: April 2011

Seven determinations of geothermal heat flow were made in the general area of southern Prince Patrick Island in the Canadian Arctic Archipelago. Measurements were made from sea ice in water depths of between 200 and 600 m. The mean heat flow for the two stations on the continental shelf in the Arctic Ocean was 0.46 ± 0.08 μcal cm−2 s−1. The mean heat flow for the five stations in the channels to the east of Mould Bay was 1.46 ± 0.16 μcal cm−2 s−1. The instrument and field methods are described. Errors due to the instrument and to the environment are discussed.
EXPERIMENTS ON THE AIR PERMEABILITY OF FOREST SOILS BY RADIUM-EMANATION METHOD
Authors: Imre J.
Published: April 2011

A radium-emanation method was developed for measuring the gas diffusion coefficient D in soils of differing structure and colloidal properties. The method was quick and simple, and could be carried out under natural, undisturbed soil conditions. Diffusion coefficients varied from 200 cm2/hour in coarse-textured soil to less than 5 cm2/hour in moderately fine-textured alkaline soil. The permeability was reduced by an increase in soil moisture, clay, and alkali content in the profile. When these factors varied with depth, the diffusion coefficient was not constant and the theoretical conditions of the method were not satisfied. Useful estimates were possible, however, when the apparent D values obtained at different depths were compared with other soil properties.
ON THE FACTORS AFFECTING THE RATE OF ABLATION OF SEA ICE
Authors: Langleben M. P.
Published: April 2011

A study has been made of the heat budget just before and during the season of ablation, of first year sea ice near the head of Tanquary Fiord. Ablation started as the air temperature approached 0 °C, producing a decrease in albedo from approximately 0.6 to 0.2 in less than a week. Typical values of incident shortwave radiation were 800 cal cm−2 day−1 on clear days and 400 cal cm−2 day−1 during heavy overcast. The net influx of all-wave radiation was about 350 cal cm−2 day−1 during the ablation period, and resulted in a rate of ablation of ice of approximately 4 cm day−1.It is shown that the flux of radiative heat is the dominant factor determining the ablation rate and the change in thermal content of the ice sheet. Upward conduction from the sea is small, except when surface melt runoff occurs and collects in a stable layer immediately under the ice sheet. Even partial refreezing in this layer may release large quantities of latent heat to increase the rate of bottom conduction appreciably.
STRATIGRAPHY AND SEDIMENTARY ENVIRONMENTS OF SOME WILDERNESS (ORDOVICIAN) LIMESTONES, OTTAWA VALLEY, ONTARIO
Authors: Barnes Christopher R.
Published: April 2011

The limestones of the Pamelia, Lowville, Chaumont, and Rockland Formations have been examined over 130 mi in the Ottawa Valley, and the lithostratigraphy and conodont biostratigraphy of the Chaumont have been studied in detail. East of Ottawa, the latter is composed of uniform, thick-bedded calcarenites (fossiliferous pelmicrites). These underlie similar Rockland limestones and overlie thin-bedded calcilutites (micrites and pelmicrites) of the Lowville and Pamelia. To the west of Ottawa, the Chaumont lithology is variable and includes "Lowville-type" calcilutites and reflects four minor regressive phases within the overall transgression. The lower Rockland above is characterized by cross-stratified calcirudites (biosparrudites and intrasparrudites) that form a wedge-shaped facies thickening westwards from Ottawa.Data on stratigraphic relations, sedimentary features, petrography, and paleontology are combined to interpret paleoenvironments, which are shown to be directly analogous to those on most modern carbonate banks. The four formations are regarded as contemporaneous lateral facies representing lagoonal muds, stable muddy sands, and local mobile shoal banks. Hence, results strongly favor stratigraphic interpretations postulating diachronous facies as opposed to chronostratigraphic rock units. Moreover, conodont biostratigraphic evidence shows diachronism in the Chaumont Formation in the Ottawa Valley. This is regarded as the first sufficiently detailed paleontological evidence capable of settling the stratigraphie controversy.
Surface waves observed close to large chemical explosions at Suffield, Alberta
Authors: Hasegawa H. S.
Published: April 2011

The present investigation is a continuation of the Suffield Experimental Station seismic program concerned primarily with a study of the propagation characteristics of the large-amplitude seismic waves in the vicinity of multiton, unconfined, chemical explosions, with the identification of the significant components of these waves, and with a determination of the source mechanism. Theoretical Rayleigh and Love wave dispersion curves are compared with the experimental data: for Rayleigh waves an additional criterion is used, namely the surface particle motion.The results indicate that: (1) the propagation characteristics of these large-amplitude surface waves are strongly influenced by the multilayering of unconsolidated sediments (several hundred feet thick) that overlie sedimentary rocks; (2) the two main components of the surface wave for which the ground motion is in the radial-vertical plane are of the types previously predicted; the former component, a constant-frequency wave train, is commonly referred to as an air-coupled Rayleigh wave; and (3) the major part of the energy of these surface waves is confined to the period range 0.2 to 1.0 second.
The transition zone between the Eurasian continent and the Arctic Ocean
Authors: Demenitskaya R. M. , Karasik A. M. , Kiselev Yu. G. , Litvinenko I. V. , Ushakov S. A.
Published: April 2011

Geophysical and bathymetric results have been used for the study of the transitional zone between the Eurasian continent and the Arctic Ocean, which is being considered by the authors as a junction area of continental margins with the adjacent seaward structures, and is dependent of the actual type of the crust found beneath the ocean.The deep Arctic Ocean comprises different types of crust: basins have an oceanic crust with increased sedimentary thickness; the Lomonosov and Mendeleev Ridges have crusts close to subcontinental; and the crust of the Gakkel Ridge is typically mid-oceanic. At least four types of transition zones may be distinguished: (1) 'normal' transition zone, where the 'granitic' layer is wedging out and the crust consists of a thinned sedimentary layer and 'basalt'; this is the junction of the continent and the oceanic basin; (2) a zone where the continental crust thins to the oceanic crust, the 'granitic' layer is absent, and the 'basalt' layer is underlain by the 7.5 km/s layer, rather than the normal mantle; this is represented by the junction of the continent with the rift zone of the median ridge that juts out into the shelf and extends under the continent; (3) a zone where the continental crust thins, the 'granitic' layer is wedging out, but the crust does not thin to the oceanic crust, mainly because of an increase in thickness of sediments; this zone is a junction of the continent with a basin with subcontinental crust; (4) a zone where the continental crust thins, but does not reach oceanic thickness; this is a junction of the continent with the oceanic crust. In the transition zones of the first and third types structural downwarping compensated by the sediments has been developed.The development of the transition zone of the Arctic was intermittent in the geological past, which we see expressed by the asymmetric development of the Greenland–Canadian and Eurasian sectors. These examples of different structures of transition zones are not unique. The transition zone between the Asiatic continent and the Indian Ocean appears to be most similar in its complexity to the transition zone of the Arctic Ocean. However the 'normal' type of transition zone characteristic of much of the continents of Australia, South America, Africa, and parts of other continents frequently occurs here.
Mobility of main ion species in reverse osmosis and the modification of subsurface brines
Authors: Everdingen R. O. van
Published: April 2011

The relative mobility of ions in cellulose-acetate membranes used for desalination of water by reverse osmosis depends strongly on the size of the hydrated ions. The preferential exchange of ions by compacted clays shows a similar dependence. It is concluded that the same dependence must exist for the mobility of ions in compacted clays and shales acting as semi-permeable membranes. Qualitative results of the processes of osmosis and reverse osmosis through these materials thus should be similar to those obtained with the desalination membranes: modification of both chemical composition (ion ratios) and concentration of the solutions involved, and the occurrence of some flow-phenomena that are not in accordance with Darcy's law.
An analysis of the crust–mantle boundary in Hudson Bay from gravity and seismic observations
Authors: Weber J. R. , Goodacre A. K.
Published: April 2011

A study of the results of the gravity and seismic surveys in Hudson Bay in 1965 has shown that the gravitational effect of a two-layer model based on the seismically determined depths has no correlation with the observed gravity anomalies. On the profile from Churchill to Povungnituk the gravity and seismic observations can be reconciled by postulating lateral variations of the acoustic compressional wave velocity within the crust. A crustal model has been calculated—using the same time-terms and the same mean crustal velocity—whose gravitational effect fits the observed gravity. The velocity varies from 6.15 to 6.56 km/s and the postulated depths are almost entirely within the confidence limits of the original model.In order to test the hypothesis, the postulated velocity variations have been compared with the lower refractor velocities of the shallow seismic survey, based on the assumption that the crustal velocities ought to be systematically higher than the crystalline surface velocities and that there may be a correlation between variations in crustal and surface velocities. The test is inconclusive because bottom refractor velocities are higher than crustal velocities in two areas where volcanic flows and high-velocity sediments may be present.The case of linearly related velocity (V) and density (ρ) variations has been analyzed and it is shown that the gravitational effect of the crust–mantle boundary undulations may be completely masked or even overbalanced by density changes in the crust if [Formula: see text]. The crust can be characterized by having dominant velocity variations (in which case the gravity anomaly reflects the undulations of the crust–mantle boundary) or dominant density variations (in which case the gravity anomaly inversely reflects the crust–mantle boundary undulations) depending on the relationship between average crustal density and average crustal velocity.
Machine contouring of frequency in a three-variable closed array
Authors: Smith F. G.
Published: April 2011

A method is described for machine plotting of contour lines representing the frequency of occurrence of sample data points in a three-variable closed array. The frequency values are in units of standard normal deviation from the expected frequency of the same sample size of a random distribution. The program is written in FORTRAN IV for an IBM 7094 computer and a CALCOMP plotter under off-line magnetic tape control.
Mineralogy and origin of the upper Eastend and Whitemud Formations of south-central and southwestern Saskatchewan and southeastern Alberta
Authors: Byers P. N.
Published: April 2011

The Upper Cretaceous non-marine Whitemud Formation of south-central and southwestern Saskatchewan and southeastern Alberta consists of kaolinitic, metamorphic lithic sands and silts, and kaolinitic clays. The sands and silts are not highly feldspathic as was originally thought. The major constituent is metamorphic lithic grains with minor kaolinitic clay and vermicular kaolin, clear angular quartz, chert, muscovite, and minor volcanic lithic grains and feldspar. The upper part of the Upper Cretaceous Eastend Formation, which conformably underlies the Whitemud Formation, consists of non-marine sands, silts, and clays. Kaolin is very rare. The bulk of the sands are composed of volcanic lithic grains with minor metamorphic lithic grains, clear angular quartz, chert, feldspar, muscovite, and biotite.The contact is characterized by the following changes from the Eastend Formation upward into the Whitemud Formation: an abrupt decrease in volcanic lithic grains and increase in metamorphic lithic grains; the appearance of kaolin and the disappearance of biotite and apatite; a slight increase in clear angular quartz and muscovite and a decrease in feldspar; a general increase in metamorphic heavy minerals; and an increase in the percentage of ilmenite (both as solitary grains and intergrown with magnetite), which is altered to leucoxene.On the basis of mineralogy, the Whitemud Formation is definitely a correlative of the Colgate Member of the Fox Hills Formation in Montana and North Dakota.The upper Eastend and Whitemud Formations were derived from Upper Cretaceous volcanic rocks, Precambrian and Paleozoic metamorphic rocks, and Paleozoic carbonates all situated in Montana. Upper Eastend sediments represent fast mechanical weathering of mountains of freshly extruded volcanic rocks, whereas the Whitemud sediments represent slow chemical weathering and leaching, which predominated once the mountainous volcanic rocks were worn down. This deep chemical weathering altered the volcanic tuffs and flows into kaolinitic clay at the source area; the kaolin of the Whitemud Formation is not derived from the weathering of feldspars at the site of deposition.It is suggested that the Frenchman and Ravenscrag Formations were also derived from Upper Cretaceous and Lower Tertiary volcanic rocks in Montana.
The structure, metamorphism, and development of the Boothia Arch, Arctic Canada
Authors: Brown Richard L. , Dalziel Ian W. D. , Rust Brian R.
Published: April 2011

The Precambrian basement rocks of the Boothia Arch exhibit three phases of folding characteristic of deep-level deformation in mobile belts. Structural cross-sections demonstrate that the geometry of compositional layering and regionally parallel axial-plane foliation of first-phase folds is controlled primarily by structures of the second phase.The basement gneisses contain assemblages of the amphibolite–granulite transitional facies. The felsic gneisses exhibit a planar fabric clearly defined by nearly oblate quartz grains, usually considered to be typical of "granulite" facies rocks. In the Boothia Arch this foliation is an axial surface structure formed during the second fold phase. Fabric studies suggest that anhydrous assemblages stable in the granulite facies prior to the second phase of deformation were replaced during this phase by hydrous assemblages characteristic of the amphibolite-granulite transitional facies.The Boothia Arch was a source of clastic sediments during three periods of cover-rock deposition. It was a mild positive feature in Aston times (late Proterozoic or early Paleozoic), and was rapidly uplifted along north-south trends during late Silurian and early Devonian times to produce continental clastic facies of the Peel Sound Formation symmetrically related to the arch. The limited Cretaceous–Tertiary record suggests irregular uplift and localized deltaic sedimentation. At other times the Boothia Arch was insignificant as a source of detritus, and carbonates were deposited over the area.The north–south strike of compositional banding and axial surfaces of the first- and second-phase folds in the basement parallels the axis of the arch and axial surfaces of folds in the cover rocks. Also, fracture patterns in the basement and cover rocks are similar. Beyond this there is no obvious relationship between the internal structure of the basement and the later development of the arch.
Magnetotelluric calculations for the interaction of polarized fields with anisotropic layered media
Authors: Praus O. , Petr V.
Published: April 2011

Recurrence formulae for calculating impedance tensor elements of the magnetotelluric field at the surface of N-layer anisotropic medium have been derived and numerical results obtained for some specific models. Directional properties of impedance tensor elements, apparent resistivities, deviation angles from perpendicularity of magnetotelluric fields, and polarization characteristics are analyzed and their importance for the interpretation of magnetotelluric results is discussed.
Quaternary geology of the Grand Rapids area, Manitoba
Authors: Grice R. H.
Published: April 2011

Grand Rapids is at the mouth of the Saskatchewan River on the western side of Lake Winnipeg in central Canada and is in the western part of the region formerly covered by Glacial Lake Agassiz.Relict beaches and cliffs, and abandoned spillway and stream channels have been observed in the area. Much of the Paleozoic bedrock is covered by Quaternary deposits consisting of three or four Wisconsin tills interspersed and covered by glacio–lacustrine silts and clays.The events are correlated with the final four episodes in the general history of Lake Agassiz and it appears that after substantial changes in the drainage pattern, the recent course of the lower reaches of the Saskatchewan River developed during the last 8 000 ± 250 y.
Rb–Sr contribution to the location of Churchill–Superior boundary in Manitoba
Authors: Turek A. , Peterman Z. E.
Published: April 2011

Eight whole-rock Rb–Sr age determinations on basement cores from the Hudson Bay Lowlands define an isochron of 1975 ± 45 m.y. (λRb = 1.39 × 10−11y−1) with an initial 87Sr/88Sr 0.7018 ± 0.0005. The indicated age is characteristic of the Churchill Province and on this basis Would suggest that the boundary between the Churchill and Superior provinces is to the south of the drill hole location. A similar age, 1925 ± 105 m.y. with an initial 87Sr/86Sr 0.7025 ± 0.0007, has been obtained on six whole-rock basement samples from the Minago River – Har-grave River area north of Lake Winnipeg.
Sur le Genre Umbellina Loeblich et Tappan
Authors: Mamet B. L.
Published: April 2011

By strict application of the Code of Botanical Nomenclature, the genus Umbellina Loeblich and Tappan is valid and the genus Umbella Masslov ? in Bykova and Polenova ought to be discarded.
Evidence of Single-Domain Magnetite in the Michikamau Anorthosite
Authors: Murthy G. S. , Evans M. E. , Gough D. I.
Published: April 2011

The Michikamau anorthosite possesses very stable natural remanent magnetization, some of which resists alternating fields up to 1800 Oe. The rock contains two types of opaque grains, fine opaque needles of order 10 × 0.5 μ in the plagioclase felspar, and large equidimensional magnetite particles. Ore microscope studies suggest, but do not establish, that the needles are composed of magnetite. Saturation isothermal remanence and thermal demagnetization studies indicate magnetite as the carrier of remanent magnetization. In order to distinguish the effects of the large grains from those of the needles, mineral separation was used to show that an artificial specimen of essentially pure plagioclase had very similar isothermal remanent magnetization properties to the whole rock. Both indicated magnetite as the magnetic mineral. Thermoremanent properties of the separated mineral fractions indicated magnetite as the dominant magnetic constituent but showed some evidence of laboratory-produced hematite. Theoretical models of grains elongated along [111] and [110] axes are used to show that magnetite needles can exist in stable single-domain configuration in the size and shape ranges of the needles observed in the Michikamau anorthosite. There is thus considerable experimental and theoretical evidence for the conclusion that the stable remanent magnetization of the Michikamau anorthosite is carried by fine single–domain needles of magnetite in the plagioclase felspar.
A Measurement of Seismic Anistropy in the Northeast Pacific
Authors: Keen C. E. , Barrett D. L.
Published: April 2011

A seismic refraction experiment was conducted in the Pacific Ocean basin, off the coast of British Columbia, Canada. The purpose of these measurements was to obtain an estimate of the anisotropy of the mantle P-wave velocity in the area and to relate this parameter to the direction of sea floor spreading. The results show that the crustal structure is similar to that measured elsewhere in the Pacific basin. Significant anisotropy of the mantle rocks is observed; the direction in which the maximum velocity occurs being 107° and the change of velocity, about 8% of the mean value, 8.07 km/s. The direction of maximum velocity does not coincide exactly with the direction of sea floor spreading, 090°, inferred from magnetic lineations.
Comparison of Sedimentary and Tectonic Foliations by X-ray Diffraction
Authors: Carrara A. , Fyson W. K.
Published: April 2011

The preferred orientation of chlorite that defines a bedding-plane foliation, both in shales and adjacent slaty tectonites, Mt. Albert area, Gaspé Peninsula, has been quantitatively determined by X-ray diffraction. The resultant preferred orientation index indicates that in the shaly sedimentary rocks chlorite alignment is partly dependent on lithological variations. Nevertheless, the mean index is closely similar to that of chlorites in undeformed shaly rocks from elsewhere. In contrast, the slates with a tectonic foliation parallel to bedding exhibit, with few exceptions, distinctly higher preferred orientations.The method thus allows the quantitative separation of bedding-plane foliations of sedimentary and tectonic origin that are not otherwise readily distinguishable.
Measured Movements of Clay Slopes in the Ottawa Area
Authors: Mitchell R. J. , Eden W. J.
Published: April 2011

Natural degradation of slopes is normally considered to involve surficial displacements resulting mainly from frost action, erosion, and downhill creep. Measurements from inclinometer installations in a variety of slope profiles in the Ottawa area show that significant deep-seated movements may occur in these slopes. These movements are associated with seasonal peaks in ground water pressures within the slope and may contribute to the long term degradation of the slope.While the factor of safety against catastrophic failure of a slope is of prime importance, the possible effects of deep-seated slope movements should not be disregarded when considering adjacent land use.
Development of Nonferrous Metal Deposits in Geological Time
Authors: Laznicka P.
Published: April 2011

A computer-derived graph of a development of deposits of twelve nonferrous metals in geological time is presented. It is based on a file containing over 5000 ore deposits, districts, and metalliferous areas of the world.The sequence of depositional ages based on ore deposits presently outcropping on the earth's surface is, from the oldest to the youngest, Cr, Ni–Au–Cu, Zn–Pb, Ag–Sn, W, Sb, Mo–Hg. Although this sequence parallels several evolutionary trends involved in the formation of the earth's crust, it is believed and semiquantitatively demonstrated that depth of denudation rather than evolution is the more important factor; in other words, the conditions of preservation have had greater influence on the age relationships of ore deposits outcropping on the present earth's surface than have the conditions of formation and their progressive evolution in the earth's history.
Pétrographie des Roches Encaissantes du Gisement Cuprifère de Louvem
Authors: Spitz Guy , Darling Richard
Published: April 2011

The Louvem copper deposit, discovered by SOQUEM in 1968, is situated in the Precambrian volcanic belt that stretches between the mining districts of Noranda and Val d'Or. The ore deposit is in the upper part of the volcanic pile, near the base of the overlying silicic pyroclastic rocks, and it is conformable with surrounding rocks. Its host rocks are meta-rhyodacite and meta-dacite flows and silicic pyroclastic rocks including tuff, agglomerate, and breccia. The principal structural features are a well-developed shear zone along the original footwall of the deposit and a locally-developed, complexly folded zone that perhaps represents a zone of slumping along the original roof of the deposit. The rocks surrounding the deposit contain mineral assemblages characteristic of the greenschist metamorphic facies. Wall-rock alteration surrounding the deposit includes pyritization, chloritization, sericitization, and silicification. Pyrite and chlorite alteration is characteristic of rocks immediately surrounding the ore while sericite and secondary quartz are present in an outer alteration zone further from the deposit. Ore deposition took place in a zone of permeable pyroclastic rocks sandwiched between two massive bands of volcanic rocks.
The Orifice Correction for K-Ar Dating
Authors: Baksi A. K. , Farrar E.
Published: April 2011

When admitting gas or isotope mixtures under molecular flow conditions into a mass spectrometer for static analysis, fractionation and back diffusion occur unless equilibrium is reached. To account for this, a theoretical 'orifice correction factor' has been developed. Experimental evidence of its validity, especially in respect to K-Ar dating, is given.
Vaurealspongia and Twenhofelella, Two New Brachiospongid Hexactinellid Sponges from the Ordovician and Silurian of Anticosti Island, Quebec
Authors: Rigby J. Keith
Published: April 2011

The new brachiospongid hexactinellid sponge Vaurealispongia perforata is described from the Upper Ordovician Vauréal Formation from the northern part of the island. The closely related new genus, Twenhofelella, is proposed and T. anticostiana (Twenhofel 1928) is re-described from the Middle Silurian Jupiter Formation in the southern part of the island. Both Vaurealispongia and Twenhofelella are included in the Pelicaspongiidae. These sponges, with Hindia cf. fibrosa and Archaeoscyphia boltoni Rigby and Nitecki 1973, constitute the known representatives of the Porifera from the island.
Proterozoic Quench-Texture Basalts from the Labrador Geosyncline
Authors: Pearce T. H. , Donaldson J. A.
Published: April 2011

The occurrence of quench-crystal basalts from the Proterozoic Knob Lake and Doublet Groups of the Labrador Geosyncline is reported. The microscopic textures are similar to those in both modern abyssal basalts and Archean basalts from the Superior Province of the Canadian Shield. Textures of quench plagioclase and pyroxene have been well preserved but the plagioclase has been altered.
U–Pb Age of Zircon from a Charnockitic Granulite from Pangnirtung on the East Coast of Baffin Island
Authors: Pidgeon R. T. , Howie R. A.
Published: April 2011

The U–Pb age of three zircon fractions from a single sample of charnockite from Pangnirtung on the east coast of Baffin Island was found to be 1900 ± 20 m.y. This is interpreted as the age of igneous activity which preceded the granulite facies metamorphism.
Artificial radioactivity layers in the Devon Island ice cap, Northwest Territories
Authors: Koerner R. M. , Taniguchi H.
Published: April 2011

Bomb-produced radioactive fall-out layers are evident in the firn at the top of the Devon Island ice cap and also lower down in a zone where accumulation is in the form of re-frozen melt-water. This allows 1963–1974 snow accumulation (positive balance) gradients for the same period to be determined on sub-polar ice caps in Canada.
Rhomboidal lattice structure: a common feature on sandy beaches
Authors: Stauffer Mel R. , Hajnal Z. , Gendzwill D. J.
Published: April 2011

Rhomboidal lattice structure is a common feature on sand beaches. It results from the intersection of two sets of small grooves that trend diagonally along the beach slope and forms immediately after or during the last stages of backwash flow.The size of the grooves increases with grain size and proximity to the surf zone. The acute angle of groove intersection is bisected by the direction of beach slope and is variable between about 30° and 45 °depending on a number of factors including: beach width, beach slope, position on beach, and grain size.The grooves are probably the surface expression of planar zones of high shear stress in which the grains become more closely packed that elsewhere in the beach sand.According to this hypothesis, the shear stresses develop due to suction generated as the pore water drains into the sand.
Bar evolution and development of stratification in the gravelly, braided, Kicking Horse River, British Columbia
Authors: Hein Frances J. , Walker Roger G.
Published: April 2011

The Kicking Horse River is a gravelly, braided stream characterized by very low winter discharge, a peak spring flood (70 m3s−1 in 1973), and summer diurnal discharge fluctuations (from 18 to 44 m3/s−1 in 1973) related to daily melting on the glaciers that supply the river. The reach studied, near Field, B.C., is characterized by abundant braid bars, and was subdivided into three parts.The upstream reach is characterized by only one major channel, with few unit bars within it. Clast movement takes place at peak flood stages, and the clasts move in 'diffuse gravel sheets' on the channel floor. These sheets are only one to two clast diameters in thickness, and when the clasts stop rolling, the sheet becomes a coarse lag. By contrast, in the midstream and downstream reaches, the channel is more anastomosing, and there are many in-channel bars, mostly transverse and diagonal unit bars. The diagonal bars mostly lack foreset slopes at their downstream margin, and it is suggested that massive to crudely horizontally stratified gravels would be deposited. Transverse bars normally have a foreset slope, giving rise to cross-stratified gravels.Several bars were monitored continuously at their active stages during the diurnal rise in discharge in the late afternoon – evening. Measurement of water slope, current velocity, depth, clast sizes, and rate of bar migration were made every 15 minutes at each of the stations on each bar. The bars tended to advance episodically during periods of velocity increase, as recorded at the upstream monitoring station. However, clast size at the bar front does not seem to increase as velocity increases, possibly due to shielding effects of the largest, stationary, clasts on the bed. This effect made existing initiation-of-bedload-movement equations difficult to apply, and of severely limited use with respect to the poorly sorted gravels.Stratification could not be directly observed in the bars, but we suggest that upstream, the diffuse gravel sheets would form crudely horizontally stratified gravels, probably with a long-axis-transverse imbrication. In the midstream and downstream reaches, in finer gravels, more cross-stratification would be present, related to migration of transverse bars.
Geochemical characteristics and evolution of basalts from DSDP site 332
Authors: Dmitriev L. , Aumento F.
Published: April 2011

The drill holes at site 332 provide the most extensive continuous section that has been obtained of the upper part of oceanic layer 2. The stratigraphic relationship between the different igneous units recovered can be defined, and these relationships, together with the petrographic, geochemical, and paleomagnetic characteristics of the igneous units indicate the existence of two distinct parental magmas; one olivine-rich, the other olivine-poor, that differentiated in adjacent but separate shallow reservoirs beneath the Median Valley. The two reservoirs alternated in their contribution to the extrusive lava pile.
Secondary minerals in some basaltic rocks from DSDP Leg 37
Authors: Scarfe C. M. , Smith D. G. W.
Published: April 2011

Zeolites, clays, carbonates, palagonite, and other secondary phases in basalts and basaltic breccias from holes 332A, 332B, 333A, and 335 provide information about The alteration of the volcanic layer of the oceanic crust. Microprobe analyses of fresh and altered glasses from all holes show that palagonitization involves addition of H2O, K2O, TiO2 and total Fe, and loss of SiO2, Al2O3, CaO, MgO, and Na2O. Fresh glass is tholeiitic in composition; however, glass microinclusions in plagioclase phenocrysts are enriched in FeO and MgO and have normal CaO contents, but are strongly depleted in Al2O3. Secondary minerals include phillipsite, calcite, siderite, saponite, and Fe. K-rich clay (celadonite?), and hydrated Fe-oxides. Phillipsite, found in cavities, vesicles, and veins, is present in all holes and is K2O-rich and Al2O3-poor, showing deviations from its ideal composition. TheCaCO3 content of siderite (~15 mol%) is surprisingly high, suggesting a formation temperature in excess of 400 °C. All other indications, however, are that the secondary minerals were formed at low temperatures by interaction of seawater with basalts of oceanic layer 2. The incorporation of substantial amounts of K into palagonite, zeolites, and some clays during seawater–basalt interaction may represent one of the major components in the K-budget of the ocean.