bluuebunny/crossref_metadata_2025 huggingface dataset:
Accumulation, absorption et assimilation des nitrates chez différentes variétés de blé tendre marocain : influence de la lumière
Authors: Abdellaoui Abdelfattah , Larhnim Asia , Talouizte Ahmed
Published: April 2011

The absorption, the exsorption, and the reduction of NO3- ions were examined in light and in darkness in relation to the prior accumulated nitrates in various seedling parts of four Moroccan tender wheat genotypes: Marchouch, Jouda, Khair, and Sais. The genotype Sais has the highest quantity of accumulated nitrates, and the genotype Khair has the lowest. Distribution of nitrates between the roots and shoots of these wheat varieties showed that, for each variety, the shoot accumulates three to five times more NO3- than the roots. Seedlings of the different varieties exposed to light showed a higher absorption and reduction of nitrates than seedlings exposed to darkness. The exsorption of nitrates of plants that are subjected to light was significantly lower than that of the seedlings exposed to darkness. This suggested that the stimulation of NO3- absorption, observed in plants that were exposed to light in comparaison with darkness, could be partly explained by the diminution of nitrate exsorption. The quantitative examination of N-nitrate in roots of plants that were exposed to light showed the presence of quantities of NO3- similar to those of the seedling roots maintained in darkness. These results suggest, that by stimulating the reduction of nitrates, light contributes to a substantial increase of nitrate ion absorption by means of a diminution of ion exsorption out of root cells.
The discrimination of cottonwood clones in a mature grove along the Oldman River in southern Alberta
Authors: Gom Lori A , Rood Stewart B
Published: April 2011

In southwestern Alberta, the prairie cottonwood (Populus deltoides Bartr.), balsam poplar (Populus balsamifera L.), narrowleaf cottonwood (Populus angustifolia James), and interspecific hybrids provide the foundation of the biologically rich riparian forests. In addition to seedling-based reproduction, these cottonwoods are capable of clonal propagation, the extent of which is poorly understood. To investigate clonality in mature cottonwoods, a method for clone recognition was investigated. Between 1995 and 1997, the morphology and phenology of each tree in a mature cottonwood grove along the Oldman River were characterized. In decreasing order of utility, the characteristics most effective in revealing clones were sex, leaf shape, floral (inflorescence) phenology, and leaf phenology: flushing, senescence, and abscission. Independent traits of poplar bud gall mite (Aceria parapopuli Keifer) susceptibility and trunk architecture were less useful in clone delineation but validated the clonal determinations. Based on the analysis, the grove's 391 trunks (>10 cm diameter) included 115 genotypes, 48 single-trunked individuals, and 67 multiple-trunked clones. The clones (genets) contained from 2 to 53 trunks (ramets). It was found that 88% of trunks belonged to clonal groups, a proportion that was higher than anticipated. The extensive capacity for clonal recruitment should thus be considered in analyses of cottonwood reproductive ecology and cottonwood conservation and restoration programs.Key words: asexual reproduction, clone delineation, cottonwoods, morphology, phenology, Populus.
Occurrence of tertiary branched tetraamines in two aquatic plants
Authors: Hamana Koei , Niitsu Masaru , Samejima Keijiro
Published: April 2011

Four aquatic plants were tested for the occurrence of unusual polyamines by high performance liquid chromatography and gas chromatography. The whole plants ubiquitously contained norspermidine, homospermidine, norspermine, and thermospermine in addition to usual polyamines such as diaminopropane, putrescine, spermidine, and spermine. Pistia stratiotes L. and Potamogeton distinctus A. Bennett contained aminopropylhomospermidine. Caldopentamine was detected in the former plant. Homospermine was found in Ranuculus aquatilis L. Two tertiary branched tetraamines, N4-aminopropylnorspermidine and N4-aminopropylspermidine, were detected in Potamogeton distinctus and Sagittaria trifolia L.Key words: aquatic plant, polyamine, tertiary branched tetraamine.
Documenting forest stand invasion: fossil stomata and pollen in forest hollows
Authors: Parshall Tim
Published: April 2011

Stomata and pollen from forest hollow sediments in the Great Lakes were evaluated for their ability to document stand-scale forest invasion. In surface sediments of 19 forest hollows, stomate presence is related most closely to tree presence within 10-20 m for eastern hemlock (Tsuga canadensis (L.) Carr.), pine (Pinus spp. L.), balsam fir (Abies balsamea (L.) Mill.), and northern white cedar (Thuja occidentalis L.). Although the abundance of hemlock pollen in surface sediments is positively related to the abundance of hemlock trees within 100 m, it does not consistently reflect the presence of hemlock trees within this distance. Pollen and stomata preserved in forest hollow sediments from northwestern Wisconsin were used to document two stages of stand invasion by eastern hemlock. First, hemlock stomata initially appear approximately 2400 14C years BP, representing the initial colonization of the forest stand. Hemlock pollen also first appears at this time but in such low abundance that the presence of hemlock trees at the site cannot be known with certainty. Second, hemlock pollen percentages increase sharply around 350 14C years BP, approximately 2000 years following initial colonization, and represent an expansion of the local hemlock population not reflected by stomatal and needle abundance.
Prevention of ice propagation by permeability barriers in bud axes of Vitis vinifera
Authors: Jones Kim S , McKersie Bryan D , Paroschy John
Published: April 2011

A physical barrier exists in Vitis vinifera L. (wine-quality grapevines) between the canes that freeze at subzero temperatures and the buds that supercool, thereby avoiding ice formation in these delicate organs. Our objective was to characterize the ice nucleation barrier by observing grape buds at different stages of acclimation, by treating them with pectinase, and by comparing them to buds of the more hardy Vitis riparia L. and to non-supercooling buds of Populus nigra L. "Italica." Differential thermal analysis (DTA) indicated that as V. vinifera andV. riparia acclimated in the autumn, the ice nucleation point of the buds declined, then increased as the grapevines de-acclimated in the spring. Laser scanning confocal microscopy was used to detect the penetration of fluorescent rhodamine green dyes from the cane into the bud as a measure of apoplastic permeability. These pore size exclusion tests indicated that the bud axes were impermeable to a 3000 MW dextran-conjugated dye when the ice nucleation temperature was below -20°C, but permeable above -20°C. This lower porosity presumably restricts the penetration of ice into the bud from the cane. In contrast to the two Vitis species, the permeability of Populus buds did not limit ice propagation, and the water in buds froze between -5 and -10°C according to DTA. Pectinase and phosphate treatments of grape buds to remove pectin increased apoplastic permeability, increased the ice nucleation temperature, and prevented supercooling according to DTA. Light microscopy indicated that suberin coated the scales of the grape buds, probably preventing ice nucleation from the environment, but was not present in the bud axis region. We concluded that a permeability barrier, possibly containing pectin, in the axis of grape buds limits the propagation of ice into the buds and enables supercooling to occur.Key words: supercooling, freezing, acclimation, winter hardiness, pectin, confocal microscopy.
How important is phylogenetic history in explaining character states in pleurocarpous mosses?
Authors: Hedenäs Lars
Published: April 2011

A redundancy analysis (RDA) with following forward selection and variance partitioning was performed to evaluate whether character state variation in pleurocarpous mosses is best explained by higher level taxonomic position or a selected set of environmental parameters. The studied explanatory parameters explain ca. 30% of the total character state variation. Taxonomic position, reflecting the phylogenetic component, is the most important among the studied explanatory parameters, and the phylogenetic component on its own is relatively more important in explaining the variation in the gametophyte than in the sporophyte. Among the environmental parameters, the general habitat parameter was the most important, followed by the climatic zone, and the wetland to nonwetland gradient. In the RDA, gradients of the sporophyte character states are more important than those of the gametophyte. Those of the sporophyte relate to the degree of sporophyte specialization, whereas those of the gametophyte relate to characters associated with water conduction. Phylogenetic time lags are likely to account for the strong influence of the phylogenetic component in most cases, because correlations between taxonomic position and environmental parameters were very few, whereas convergent or parallel evolution is likely to explain the similar states found in strongly specialized sporophytes.
Plant regeneration from sugar beet leaf protoplasts: analysis of shoots by DNA fingerprinting and restriction fragment length polymorphism
Authors: Jazdzewska E , Sadoch Z , Niklas A , Majewska-Sawka A
Published: April 2011

Shoots were regenerated from leaf protoplasts of cytoplasmic male sterile and male fertile diploid sugar beet (Beta vulgaris L.) genotypes. Protoplasts cultured in Murashige and Skoog medium supplemented with 5 µM naphthaleneacetic acid, 2 µM 6-benzylaminopurine, 100 µM n-propyl gallate, and diamine putrescine at concentrations of 50, 100, or 500 µM were able to synthesize a new cell wall and entered successive mitotic divisions leading to the formation of callus colonies. Shoots were obtained via organogenesis by continuous culture of calli on the same basal medium supplemented with either cytokinin alone, or with a combination of cytokinin and auxin. The regenerants of both lines were characterized with regard to ploidy, and the regenerants of the male sterile line were further characterized with regard to possible somaclonal variation and organization of two mitochondrial genes: atpA and atp6. Chromosome counting revealed that tetra-, hexa-, and octa-ploids were present among regenerants. Random amplified polymorphic DNA (RAPD) analysis identified one somaclonal variant among 31 shoots tested, whereas hybridization with both mitochondrial probes showed no notable changes in the organization of mtDNA within these loci.Key words: Beta vulgaris L., protoplasts, regeneration, random amplified polymorphic DNA (RAPD), atpA, atp6.
Ecological patterns of diatom assemblages from Mackenzie Delta lakes, Northwest Territories, Canada
Authors: Hay Murray B , Michelutti Neal , Smol John P
Published: April 2011

Sediment samples were collected from 77 lakes in the Mackenzie Delta representing a gradient of lakes from those having continual connection with the sediment-laden Mackenzie River to lakes having connection for only a couple of days every few years. Diatom assemblages in all lakes were dominated by a diverse benthic microflora, primarily from the genera Navicula and Nitzschia. Maximum relative abundance of the dominant taxon at all sites was less than 30%, and most taxa did not dominate in more than one or two lakes. Delta lake assemblages were distinct from diatom assemblages associated with other regional transects of upland tundra and forest lakes. Detrended correspondence analysis showed that nonmotile epiphytic genera, such as Cocconeis and Gomphonema, were more common in lakes having a lower influence from the Mackenzie River, reflecting the extensive macrophyte growth within these lakes. Species diversity decreased as macrophyte production increased. Taxa responses along this macrophyte production gradient were modeled using partial least squares regression. Diatoms were sensitive to the degree of river influence, and the related biological and limnological changes, suggesting assemblages can provide an indication of hydrological variability within Mackenzie Delta lakes.Key words: diatoms, detrended correspondence analysis, Mackenzie Delta, floodplain, lakes.
The effects of drought and waterlogging conditions on the performance of an endemic annual plant, Aster laurentianus
Authors: Houle Gilles , Belleau Annie
Published: April 2011

Aster laurentianus Fernald is an annual plant endemic to the St. Lawrence estuary. It typically grows in salt marshes at the periphery of shallow lagoons. In this habitat, the water level fluctuates greatly both within and between years. Such fluctuations may induce significant interannual variations in marsh-plant populations. In this study, we experimentally determined the effects of different water availability conditions, imposed at various stages of plant development, on the performance of A. laurentianus. Waterlogging had no significant effect on net carbon assimilation rate, plant growth, and biomass allocation. However, a drought stress at the time of reproductive-bud differentiation had a negative effect on flower-head production. We propose that occasional reproductive failures resulting from late-summer droughts may cause significant interannual fluctuations in the size of A. laurentianus populations, potentially making them more susceptible to local extinction.Key words: Aster laurentianus, endemic plant, Îles-de-la-Madeleine, rare plant, salt marshes, water stress.
Molecular markers indicate two cryptic, genetically divergent populations of Russian thistle (Salsola tragus) in California
Authors: Ryan Frederick J , Ayres Debra R
Published: April 2011

Genetic variability among accessions of Russian thistle (Salsola tragus L.) from California was investigated using allozymes and DNA-based molecular markers. Aspartate aminotransferase and 6-phosphogluconate dehydrogenase displayed two multienzyme phenotypes that were widespread in plants throughout the state. Random amplified polymorphic DNA analysis was conducted on samples of the two isoenzymic phenotypes collected throughout California, as well as additional accessions from France and Turkey and Salsola paulsenii Litv. Six primers produced 23 polymorphic bands. Analysis of the patterns of bands by calculation of simple matching coefficients and cluster analysis confirmed the genetic distinctness of the two isoenzymic phenotypes of S. tragus; S. paulsenii was markedly different from both types. Mean fruit weights from plants grown under similar conditions were different between the two types as well. These results and preliminary cytological analysis together suggest that the two types are actually two different species of Salsola, only one of which has been previously recognized. Analysis of the DNA-based markers suggests that one of the genetic entities may be closely related to Salsola found in Europe, while the area of origin of the second entity is currently obscure.Key words: allozyme, genetic diversity, RAPD assay, Salsola tragus, Salsola paulsenii.
Morphological and molecular characterization of Chalara elegans (Thielaviopsis basicola), cause of black root rot on diverse plant species
Authors: Punja Zamir K , Sun Li-Juan
Published: April 2011

The extent of variation in colony morphology and chlamydospore size, septation, and pigmentation was studied in 50 isolates of Chalara elegans Nag Raj et Kendrick (syn. Thielaviopsis basicola (Berk. et Br.) Ferr.) originating from 12 different geographic areas and substrates. In addition, the extent of genetic variation among these isolates was determined using random amplified polymorphic DNA (RAPD) analysis. Five general morphological groups could be distinguished among the isolates, two of which were aberrant phenotypes (albino and mycelial) that were derived upon continuous subculture of some wild-type isolates in the laboratory. The isolates with the most variation in phenotype originated from British Columbia and California. Six primers (10-mers) were used to generate 90 bands in RAPD-PCR, of which 75 were polymorphic. A high degree of diversity was apparent within C. elegans, and some banding patterns generated by specific primers were unique to certain isolates, thereby generating fingerprints. Distinct groups (clusters) were obtained following UPGMA analysis and, generally, these were composed of isolates from similar geographic regions or hosts. However, isolates from some areas, for example, British Columbia, were also found to belong to different clusters. There was generally a good relationship between groups assigned on the basis of morphology and those derived from cluster analysis, that is, isolates within a cluster tended to have similar morphology. In a few isolates, the aberrant phenotypes (albino and mycelial) could be distinguished using RAPDs from the wild type by the absence of 1 or 2 bands, indicating that changes in the nucleotide sequence had occurred, possibly through mutation. The average similarity index among all 50 isolates of C. elegans was 87%. An outgroup species (Chalara thielaviodes) had a similarity value of 40%.
Chrysophycean stomatocysts from freshwater habitats of the Strømness Bay area, South Georgia, Antarctica
Authors: Van de Vijver Bart , Beyens Louis
Published: April 2011

The chrysophycean stomatocyst flora of freshwater samples from the Strømness Bay area, located in the northern part of the Sub-Antarctic Island of South Georgia, was investigated, using scanning electron microscopy. A total of 59 stomatocyst morphotypes were recorded. Thirty-one of them were previously observed and 28 are described as new, following guidelines of the International Statospore Working Group. Since this is only the second study of chrysophyte cysts from South Georgia, this large number of new morphotypes is not surprising. The cyst flora show only a small resemblance to the stomatocyst flora found on mosses of the same area.Key words: chrysophyte stomatocysts, South Georgia, Sub-Antarctica.
Water-borne conidia of aquatic hyphomycetes: seasonal and yearly patterns in Catamaran Brook, New Brunswick, Canada
Authors: Bärlocher Felix
Published: April 2011

Over a period of 5 years, monthly samples of water-borne conidia were collected at two sites, bridge and mouth, in Catamaran Brook, a third-order salmon stream in New Brunswick, Canada. Conidial concentrations and number of aquatic hyphomycete species peaked in October; a smaller peak was generally observed in June. Evenness was lowest in October. The number of species in the five 12-month periods varied between 46 and 56 (bridge) and 41 and 47 (mouth); over the entire period, 75 (bridge) and 70 (mouth) species were identified. Of these, 30 and 26, respectively, occurred in every period. The average ranks of the 12 dominant species (based on yearly conidium production) could be divided into two groups of no significant differences: ranks 1-7 (bridge) and 1-10 (mouth), respectively, and 2-12 (both sites). Monthly abundances of the 12 top-ranked species were examined for correlations. Significant correlations found in periods measuring between 1 and 4 years were rarely validated in subsequent periods.Key words: aquatic hyphomycetes, stream spora, annual and seasonal periodicity.
Mycorrhizal associations of Salix repens L. communities in succession of dune ecosystems. I. Above-ground and below-ground views of ectomycorrhizal fungi in relation to soil chemistry
Authors: van der Heijden EW , Vries FW de , Kuyper Th. W
Published: April 2011

The diversity of ectomycorrhizal (EcM) communities in 16 stands of Salix repens L. growing under a variety of environmental conditions was studied by repeated sampling of EcM sporocarps and ectomycorrhizas, to assess the possible correspondence between above- and below-ground views of fungal taxa. Above- and below-ground views were also related to soil chemistry. Sporocarps of 78 taxa of EcM fungi belonging to 12 genera were found. The majority of the species found, especially those of the Cortinariaceae, were host-specific for Salicaceae. Canonical correspondence analysis (CCA) based on fungal species showed that only pH and the concentration of available phosphorus significantly contributed to the variation explained. CCA based on fungal genera indicated that pH and moisture significantly contributed to the variation explained. Fifteen different EcM morphotypes were recognized and morphotype composition was different on two sampling dates. CCA based on morphotype composition yielded different results depending on sampling date. The numbers of EcM sporocarps and root tips were not correlated (on either sampling date). Diversity above ground (species and genus) was also not correlated with morphotype diversity below ground on either sampling date. Therefore, neither diversity nor abundance of above-ground EcM fungi can be used to assess below-ground EcM diversity or abundance. Lack of correlation in below-ground parameters on different sampling dates indicates substantial variation. Causes for temporal variation are discussed. The importance of investigating both above- and below-ground variability in EcM communities is stressed.
Mycorrhizal associations of Salix repens L. communities in succession of dune ecosystems. II. Mycorrhizal dynamics and interactions of ectomycorrhizal and arbuscular mycorrhizal fungi
Authors: van der Heijden EW , Vosatka M
Published: April 2011

Ectomycorrhizal (EcM) and arbuscular mycorrhizal (AM) associations of Salix repens were studied at 16 sites in different successional stages of dune ecosystems (calcareous-acidic, dry-wet) in the Netherlands. High EcM colonization, low AM colonization, and lack of differences between habitats indicate that ectomycorrhizas do not increase their importance in later successional stages. EcM and AM colonization and plant-nutrient status indicate that the relative importance of P and N does not change during succession, but during seasons. Salix repens showed low levels of AM colonization but, nevertheless, even these low levels contributed to covering the P demands of the plant. As a decrease in AM colonization in S. repens at the end of the season coincided with a decrease in AM inoculum potential, the seasonal decline of arbuscular mycorrhiza is caused by changes in plant demand or soil nutrient availability rather than by interference by ectomycorrhiza. Regardless of seasonal shifts and possible interaction between ectomycorrhiza and arbuscular mycorrhiza, both persist in the plant roots during seasons and throughout succession. Differences in the habitat preference of various EcM morphotypes and arbuscular mycorrhiza suggest that mycorrhizal diversity contributes to the broad ecological amplitude of S. repens.
Effects of flower production and predispersal seed predation on reproduction in Cirsium purpuratum
Authors: Ohashi Kazuharu , Yahara Tetsukazu
Published: April 2011

Researchers have often assumed that the reproductive success of a plant increases with flower production. However, if predispersal seed predation also increases with flower production, this may counteract the increase in reproductive success expected with such increased flower production. To investigate this, we examined the effect of flower number and predispersal seed predation on seed production in two field populations of Cirsium purpuratum (Maxim.) Matsum. At both sites, the proportion of seeds or heads preyed upon per plant increased with the number of flowers (florets or heads) on each plant, while the proportion of mature seeds per plant was independent of flower number per plant. Based on these results, we predicted that an increased level of seed predation at the population level would reduce the annual flower production of each plant. The observed pattern of flower production supported this prediction. Our results suggest that increased flower production may not always improve plant reproductive success under the influence of predispersal seed predation.Key words: plant reprodutive success, predispersal seed predation, Cirsium purpuratum, flower production, plant-animal interaction.
Patterns of species composition and distribution of arbuscular mycorrhizal fungi in arid regions of southwestern North America and Namibia, Africa
Authors: Stutz Jean C , Copeman Ruth , Martin Chris A , Morton Joseph B
Published: April 2011

Arbuscular mycorrhizal (AM) fungal communities at 13 sampling sites in two arid regions (Chihuahuan and Sonoran Deserts) and semi-arid grasslands in North America were compared with each other and with AM fungal communities in the Namib Desert in Africa using successive trap cultures to induce sporulation. Twenty-one AM fungal species were recovered, eight of which were undescribed. Species richness at each sampling site ranged from 6 to 12 species. There was considerable overlap in the species composition of the two desert regions surveyed in North America. Glomus microaggregatum Koske, Gemma & Olexia, Glomus etunicatum Becker & Gerd., Glomus intraradices Schenck & Smith, Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, Glomus spurcum Pfeiffer, Walker & Bloss, and two undescribed Glomus species (AZ112 and AZ123) were detected in over 50% of the sampling sites in North America. Similarities in species composition of arid regions of Namibia and North America also was high, ranging from 54 to 79%. The taxonomic range of AM fungi was limited mostly to small-spored fungi in Glomaceae and Acaulosporaceae. Acaulospora trappei Ames & Linderman, Glomus etunicatum, Glomus intraradices, Glomus occultum Walker, Glomus microaggregatum, Glomus mosseae, Glomus spurcum, and an undescribed Glomus species (AZ123) were detected in all three desert regions and in semi-arid grasslands. Gigaspora rosea Nicolson & Schenck was the only species in Gigasporaceae detected, and then only at one sampling site in North America. Scutellospora species were not found. These results indicate involvement of both historical processes such as dispersal and selective variables at the local level in determining species composition in arid environments.Key words: biogeography, Chihuahuan Desert, community structure, diversity, Glomales, Namib Desert, species richness, Sonoran Desert.
Phylogenetic relationships ofCylindrocladium pseudogracileandCylindrocladium rumohraewith morphologically similar taxa, based on morphology and DNA sequences of internal transcribed spacers and beta-tubulin
Authors: Crous Pedro W , Kang Ji-Chuan , Schoch Conrad L , Mchau Godwin RA
Published: April 2011

Unidentified strains of Cylindrocladium that were baited from soil in the Amazonas state of Brazil or isolated from Adiantum in the Netherlands were examined morphologically and analysed phylogenetically in comparison with reference strains. Phylogenetic trees inferred from the 5.8S subunit and flanking internal transcribed spacers (ITS1 and ITS2) of rDNA, as well as the beta-tubulin gene, separated species in accordance with their morphological features and characteristics. Although species differences based on ITS sequences were consistent, there were only a few informative sites available, making it difficult to clearly identify the unknown strains. Better resolution in separation of species was achieved from the beta-tubulin data. The strains baited from soil in Brazil were found to represent two species, namely Cylindrocladium gracile (Bugnic.) Boesew. and Cylindrocladium pseudogracile Crous. Morphologically, these two species are similar, except that the latter has slightly narrower, 1(-3)-septate conidia, and produces a Calonectria teleomorph. Furthermore, the strain from the Netherlands represents Cylindrocladium rumohrae El-Gholl & Alfenas, a species previously known only from Panama. Results of this study also indicated that the beta-tubulin gene is phylogenetically more informative than the ITS regions for distinguishing species of Cylindrocladium.
Trace element geochemistry of the Meen-Dempster greenstone belt, Uchi subprovince, Superior Province, Canada: back-arc development on the margins of an Archean protocontinent
Authors: Hollings Pete , Stott Greg , Wyman Derek
Published: April 2011

Comprehensive trace element analyses of mafic and felsic volcanic rocks from the 2.85-2.74 Ga Meen-Dempster greenstone belt reveal a wide compositional diversity. The ~2.85 Ga Kaminiskag assemblage is dominated by mafic tholeiite characterized by predominantly unfractionated REE (La/Smn = 0.8-1.1). Rare intermediate and felsic pyroclastic flows (SiO2 = 62-74) with moderate to pronounced LREE enrichment are intercalated with the tholeiite. The Kaminiskag assemblage is overlain by the ~2825 Ma Meen assemblage, comprising dominantly dacitic tuffs and pyroclastic breccia, displaying enriched LREE (La/Smn = 3.7-7.2) and moderately fractionated HREE, in conjunction with pronounced negative Nb anomalies. Five distinct suites have been recognized in the ~2740 Ma Confederation assemblage: (1) tholeiitic basalt with flat to smoothly depleted REE, (2) tholeiite with flat to weakly depleted LREE in conjunction with pronounced negative Nb anomalies, (3) Fe-rich basalt with elevated Ti and P contents, LREE enrichment, and fractionated HREE, (4) LREE enriched basalt and andesite with negative Nb anomalies, and (5) dacite and rhyolite with enriched LREE, moderately fractionated HREE, and variable high field strength element anomalies. The geochemistry and geochronology of the Kaminiskag and Meen assemblages are consistent with the formation of an oceanic back arc (Kaminiskag assemblage), which formed the basement for a subduction-related arc complex (Meen assemblage) after a 15 Ma hiatus. The Confederation assemblage is interpreted to represent an Archean back arc, where the complex interplay of mantle sources allows for the eruption of tholeiite, subduction-modified tholeiite, ocean island basalt-like basalt, and subduction-related arc-type volcanic rocks. The recognition of back-arc basins within the Meen-Dempster greenstone belt emphasizes a continuity of crustal growth processes from the Archean to the present day.
Geology of the Matthew Creek metamorphic zone, southeast British Columbia: a window into Middle Proterozoic metamorphism in the Purcell Basin
Authors: McFarlane C RM , Pattison D RM
Published: April 2011

Southwest of Kimberley, southeastern British Columbia, the Matthew Creek metamorphic zone occupies the core of a structural dome in Mesoproterozoic rocks of the Lower Aldridge formation (lower Purcell Supergroup). It comprises (1) a core zone of ductilely deformed sillimanite-grade metapelites, thin foliated mafic sills, and sheared quartz-plagioclase-tourmaline pegmatites; and (2) a thin transition zone of ductilely deformed metasediments which marks a textural and metamorphic transition between the core zone and overlying regionally extensive, brittlely deformed, biotite-grade semipelitic Lower Aldridge formation metasediments and thick Moyie sills. The core zone and transition zone in combination cover an area of 30 km2. The deepest exposed rocks in the core zone have a strong foliation and lineation (D1 deformation) formed during late M1 metamorphism at conditions of 580650°C and 3.5 ± 0.5 kbar. The timing of this metamorphic-structural episode is constrained to the interval 13521341 Ma based on near-concordant UPb ages from monazite in pelitic schist near the mouth of Matthew Creek. Later, weaker metamorphic and deformation episodes variably overprinted the rocks of the Matthew Creek metamorphic zone. The juxtaposition of low-grade, weakly deformed rocks above high-grade, strongly deformed rocks across a zone of ductile deformation is interpreted to be due to a subhorizontal shear zone.
Petrology and oxygen-isotope geochemistry of the Yamba Lake kimberlite rocks, N.W.T.
Authors: Orr Pauline , Luth Robert W
Published: April 2011

The Torrie, Sputnik, and Eddie kimberlite rocks, located near Yamba Lake, central Slave province, N.W.T., are volcaniclastic, macrocrystic, heterolithic, olivine-rich tuff, and olivine-rich tuff breccia. Torrie and Sputnik kimberlite rocks contain pyroxene and garnet xenocrysts and megacrysts with major-element compositions consistent with derivation mostly from disaggregated garnet lherzolite, with subordinate contributions from eclogite, spinel lherzolite, garnet harzburgite, and websterite. The presence of primary groundmass phlogopite and compositionally evolved spinel, and the absence of mantle xenocrysts, xenoliths, and megacrystic ilmenite distinguish the Eddie kimberlite pipe from the other two kimberlite pipes. Large variations in δ18O of garnet and clinopyroxene in xenocrysts and xenoliths (+3.98 to +6.36), nonequilibrium intermineral isotopic fractionation, and major-element heterogeneity are interpreted as resulting from infiltration of fluids or melts produced by dehydration or melting of subducted oceanic crust into overlying peridotite. Although the timing is unconstrained for the xenocysts, the xenolith must have experienced this metasomatic interaction shortly before entrainment in the kimberlite. Variable δ18O values for magnesian ilmenite are also interpreted to result indirectly from such metasomatic activity in the mantle as well. The Torrie and Sputnik kimberlite rocks have low concentrations of diamond indicator minerals consistent with their low-diamond grades. These kimberlite rocks did not sample a significant amount of garnet harzburgite, the rock type commonly associated with high-diamond grades in other kimberlite rocks. Furthermore, metasomatism just prior to kimberlite eruption may have caused the resorption of any diamond present.
Late Paleozoic to Cenozoic history of the offshore Sydney Basin, Atlantic Canada
Authors: Pascucci Vincenzo , Gibling Martin R , Williamson Mark A
Published: April 2011

The Sydney Basin covers a large offshore area south of Newfoundland, with a well-exposed outcrop belt on Cape Breton Island. The geological history of the poorly known offshore area is interpreted using an industry seismic grid and Lithoprobe line 86-5, tied to outcrops and two wells. The mid-Devonian to Upper Carboniferous - Permian basin fill is 6-7 km thick and represents three extensional phases with intervening and succeeding compressive phases. The mid-Devonian McAdams Lake Formation was deposited in a local half-graben during early post-Acadian extension. Following deformation, a suite of Early Carboniferous extensional basins filled mainly with Horton Group conglomerates developed on northeast-trending and southeast-dipping master faults. Some faults developed along Acadian terrane boundaries. The Windsor Group extends over the master faults to onlap basement as a result of thermal sag and Visean eustatic rise. Mid-Carboniferous deformation, linked to the Alleghanian orogeny, reactivated faults and caused basin inversion and a basinwide unconformity. Upper Carboniferous to ?Permian coal measures and redbeds were subsequently deposited in a broad basin that developed over the Early Carboniferous basins. Subsidence may reflect extension on major faults in the Cabot Strait coupled with thermal sag and (or) continued sag on an underlying mid-crustal detachment. After coalification, Acadian terrane boundaries and other lineaments were reactivated during a compressive tectonic episode, probably during the Permian. The basin's polycyclic history, with repeated subsidence and inversion phases, has important implications for hydrocarbon systems.
Predicted groundwater circulation in fractured and unfractured anisotropic porous media driven by nuclear fuel waste heatgeneration
Authors: Yang J , Edwards R N
Published: April 2011

The concept of nuclear fuel waste disposal underground is drawing increasing attention due to its many advantages against the current storage methods at surface. In this paper, we employ the Galerkin finite-element technique to solve the coupled time-dependent heat transfer and fluid flow differential equations and to predict the evolving behaviour of groundwater flow and subsurface temperature distribution associated witha proposed disposal system at the Whiteshell Research Area in southeastern Manitoba. A two-dimensional (2-D) numerical model is conceptualized from geologicalconstraints in this particular area. To investigate the free convection of groundwater flow driven by nuclear fuel waste heat generation, we assume the 2-D model has a flat upper boundary so as to eliminate the effect of topography head. Buoyancy force due to fluid density variationsis, therefore, the sole driving mechanism for fluid migration. Case studies for both unfractured and fractured porous media confirm that thermal decay of the buried fuel waste can initiate fluid circulation. In the presence of discrete fractures, the deep and hot fluid nearby the disposed contaminant can discharge to the biosphere, thus potentially threatening human health and the natural environment.
Mélanges in southern Mexico: geochemistry and metamorphism of Las Ollas complex (Guerrero terrane)
Authors: Mendoza Oscar Talavera
Published: April 2011

Las Ollas complex (LOC) is a subduction complex spatially associated with the early Cretaceous Zihuatanejo-Huetamo subterrane (Guerrero terrane) in southern Mexico. LOC tectonic mélanges compose of a stack of east-dipping, west-vergent tectonic sheets containing blocks of metabasalt, metadolerite, metagabbro, ultramafics, volcaniclastics, quartz-rich sandstone, and chert enveloped in a highly sheared clastic or serpentinitic matrix. Most igneous and igneous-derived metamorphic blocks show geochemical and isotopic features typical of island-arc tholeiitic suites: (i) low TiO2 (0.13 to 0.91%) and Zr (5 to 57 ppm) contents; (ii) high (LFSE/HFSE)N ratios; low LaN/YbN (0.5 to 4) values; and, high εNd(T) (+7.9 to +8.0) ratios. Petrographical and mineral chemistry evidence indicates that blocks underwent early recrystallization under high pressure and low temperature (HP-LT), blueschist facies conditions during subduction. Typical assemblages include blue (sodic through calco-sodic to Na-rich calcic) amphibole + lawsonite ± tremolite ± Mg-chlorite ± white mica ± albite ± quartz. Phase relations and chlorite thermometry suggest temperatures of about 200°-330o C and pressures of 5-7 kbar. It is proposed that sedimentary blocks were generated by in situ remobilization and mixing, whereas igneous blocks most probably derived from the chemically and isotopically identical Zihuatanejo island-arc suite. Our data suggest that LOC represents part of a subduction complex formed by eastward-directed subduction related with the evolution of the early Cretaceous Zihuatanejo island arc.
SHRIMP U-Pb geochronology of volcanic rocks, Belt Supergroup, western Montana: evidence for rapid deposition of sedimentary strata
Authors: Evans Karl V , Aleinikoff John N , Obradovich John D , Fanning C Mark
Published: April 2011

New sensitive high resolution ion microprobe (SHRIMP) UPb zircon analyses from two tuffs and a felsic flow in the middle and upper Belt Supergroup of northwestern Montana significantly refine the age of sedimentation for this very thick (15-20 km) Middle Proterozoic stratigraphic sequence. In ascending stratigraphic order, the results are (1) 1454 ± 9 Ma for a tuff in the upper part of the Helena Formation at Logan Pass, Glacier National Park; (2) 1443 ± 7 Ma for a regionally restricted porphyritic rhyolite to quartz latite flow of the Purcell Lava in the Yaak River region; and (3) 1401 ± 6 Ma for a tuff in the very thin transition zone between the Bonner Quartzite and Libby Formation, west of the town of Libby. Combining these ages with those previously published by other workers for ca. 1470-Ma sills in the lower Belt in Montana and Canada indicates that all but the uppermost Belt strata (about 1700 m) were deposited over a period of about 70 million years, considerably reducing the time span from longstanding estimates ranging from 250 to 600 million years. Calculated sediment accumulation rates between dated samples indicates rapid, but not unreasonable, values for early Belt strata, with decreasing rates through time. These ages also suggest the inadequacy of previously published paleomagnetic data to resolve Belt Supergroup chronology at an appropriate level of accuracy.
Periodically forced self-organization in the long-term evolution of planktic foraminifera
Authors: Prokoph Andreas , Fowler Anthony D , Patterson R Timothy
Published: April 2011

Wavelet transform and other signal analysis techniques suggest that the planktic foraminiferal (PF) long-term evolutionary record of the last 127 Ma can be attributed to complex periodic and nonlinear patterns. Correlation of the PF extinction pattern with other geological series favors an origin of the ~30 Ma periodicity and self-organization by quasi-periodic mantle-plume cycles that in turn drive episodic volcanism, CO2-degassing, oceanic anoxic conditions, and sea-level fluctuations. Stationary ~30 Ma periodicity and a weak secular trend of ~100 Ma period are evident in the PF record, even without consideration of the mass extinction at the KT boundary. The 2732 Ma periodicity in the impact crater record and lows in the global sea-level curve, respectively, are ~6.5 Ma and ~2.3 Ma out of phase with PF-extinction data, although major PF-extinction events correspond to the bolide impacts at the KT boundary and in late Eocene. Another six extinction events correspond to abrupt global sea-level falls between the late Albian and early Oligocene. Self-organization in the PF record is characterized by increased radiation rates after major extinction events and a steady number of baseline species. Our computer model of long-term PF evolution replicates this SO pattern. The model consists of output from the logistic map, which is forced at 30 Ma and 100 Ma frequencies. The model has significant correlations with the relative PF-extinction data. In particular, it replicates singularities, such as the KT event, nonstationary 2.510 Ma periodicities, and phase shifts in the ~30 Ma periodicity of the PF record.
Petrology, palynology, coal facies, and depositional environments of an Upper Carboniferous coal seam, Minto Coalfield, New Brunswick, Canada
Authors: Kalkreuth W , Marchioni D , Utting J
Published: April 2011

Coal petrology and palynology of the Minto coal seam enable depositional environments of the precursor mire to be established in terms of facies-critical maceral ratios, maceral assemblages, and spore and pollen assemblages. The overall petrographic composition indicates a vitrinite-rich coal (mean 67%), followed by inertinite (mean 27%) and liptinite (mean 7%). Pyrite is common to abundant (maximum 15%). Lithotype logs demonstrate a dominance of dull lithotypes (dull and banded dull). Petrographic composition at the lithotype and seam subsection level is highly variable. Vitrinite maceral assemblages are enriched in brighter lithotypes (banded bright and bright), whereas liptinite and inertinite maceral assemblages are enriched in dull and banded dull lithotypes. The duller lithotypes are enriched by mineral matter. Based on spores, the seam is assigned to the Vestispora Zone of Atlantic Canada, with the basal Torispora securis-Torispora laevigata (SL) Zone of western Europe and the lower Torispora securis-Vestispora fenestrata (SF) of the Illinois Basin. This indicates an early Bolsovian (Westphalian C) age. Based on the Tissue Preservation Index - Gelification Index facies concept, the seam was deposited in an upper delta plain. At the seam subsection level, facies-critical maceral ratios (Groundwater Influence Index, Vegetation Index) and maceral assemblages suggest both limnic (open moor) conditions and somewhat drier conditions. Relative low Vegetation Indices suggest mainly herbaceous source material, which is partly supported by the rare to common occurrence of small lycopsid spores and arboreous lycopods. The abundant sphenopsids, including Calamites, and rare gymnosperms may have grown outside the mire.
The Climate System History and Dynamics Program - CSHD: Introduction
Authors: Peltier W R
Published: April 2011

The goal of the Climate System History and Dynamics (CSHD) Program is to improve understanding of the global climate system so as to increase our ability to predict future change in the global environment. Papers in this special issue represent examples of work accomplished during CSHD-Phase 1, which began in 1995 and ended in 1998. This special issue presents the work of ten groups of scientists, including groups interested in the reconstruction of past climate states using geologically derived proxy data and groups interested in the use of models to predict these states, combined in a focused effort to provide a Canadian contribution to the international Paleoclimate Model Intercomparison Project (PMIP). CSHD-Phase 1 primarily focussed on two "time slices:" the last glacial maximum (LGM) of the late Cenozoic (21 ka BP) and the mid-Holocene warm period (6 ka BP).
Modes of extinction, pseudo-extinction and distribution in Middle Jurassic ammonites: terminology
Authors: Westermann Gerd EG
Published: April 2011

Mid-Jurassic Ammonitina (Cephalopoda, Mollusca) provide good examples of true and apparent "extinctions" (i.e., taxon or clade disappearances) at the local, regional, and global scales. A terminology is presented. Extinction is the termination of a phylogenetic lineage or entire clade (not of local demes or regional populations). Extinction was often preceded by progressive range contraction that resulted in diachronous regional disappearance ("extirpation") and occurred with the elimination of the last refuge. Other range contractions, however, were not terminal, but were followed by renewed expansions, resulting in temporary absence of the lineage over part of its known range only, due to pseudo-extinction. Some lineages, called Lazarus taxa, apparently disappeared entirely for short or extended periods by pseudotermination (causing a "phylogenetic hiatus"). This is an extreme form of pseudo-extinction with unknown refuge due to small size and (or) unsuitable facies and location. Lineage or clade reappearance may be in the form of new species, whose relationship to ancestral taxa has been problematic. Some disappearances can be explained with displacive competition, where the replacement taxon is either of endemic origin or an immigrant. Recent research in previously underexplored field areas has closed some of the gaps of documentation by finding the refuges. Range contractions and expansions, together with their regional disappearances and pseudo-extinctions, including pseudotermination, were often causally related to sea-level changes, especially eustasy. Most true extinctions, however, cannot be identified precisely, because they occurred in small populations and (or) refuges. Extinctions presumably did not coincide with global geoevents.