bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparisons between the metal content of a transplanted lichen before and after the start-up of a coal-fired power station in Israel
Authors: Garty Jacob
Published: October 2008

The lichen Ramalina duriaei (De Not.) Bagl. was transplanted to 10 biomonitoring sites during the period December 1981 – December 1982. The amounts of Ni, Cr, Cu, Zn, and Pb in the lichen material were measured at the beginning and at the end of the exposure period. These data were compared with the metal amounts detected in R. duriaei transplanted to the same stations during the period February 1979 – March 1980. After the 1981 – 1982 period, the regional amounts of Ni, Cr, and Pb in the transplanted lichen were found to be higher than in the lichen transplanted to the same sites during the 1979–1980 period, prior to the operation of the coal-fired power plant. The increase of Pb in the lichen after the second period (1981 – 1982) reflects the increase in the total number of motor vehicles in the country during that time. The increase of the amounts of Cr and Ni in the latter period is probably related to emissions of these substances from the power-plant stack. The regional decrease in Zn amount in the lichen in the latter period is probably related to a decrease in the use of Zn as a constituent of foliar nutrients in agriculture.
Nuclear behavior during sporulation of the true slime mold Didymium nigripes
Authors: Kerr Sylvia Joann
Published: October 2008

Nuclear behavior during sporulation of the true slime mold Didymium nigripes Fries includes extensive episodes of nuclear degeneration of a magnitude not previously suspected, two mitotic divisions, and changes in nuclear morphology. Nuclear and nucleolar diameter are reduced and up to 60% of the nuclei present at the onset of sporulation degenerate. Didymium nigripes possesses nuclei of several ploidy levels throughout its life cycle, and ratios of these nuclear size classes change in random fashion during sporulation, presumably as a result of nuclear degeneration. This study demonstrates that the end result of nuclear degeneration is not the elimination of a single size class of nucleus.
Patatin in wild species of Solanum
Authors: Racusen David
Published: October 2008

Tubers of 28 species of the genus Solanum contained a glycoprotein that appeared identical with S. tuberosum patatin by SDS gel electrophoresis. Patatin from six of the species was isolated using a patatin-specific chromatographic protocol. Each purified patatin had a unique carbohydrate content and copurified with an esterase having a characteristic substrate preference towards α-naphthyl acetate or p-nitrophenyl laurate.
The effects of organic and inorganic phosphorus concentration on the acid phosphatase activity of ectomycorrhizal fungi
Authors: Kroehler Carolyn J. , Antibus Robert K. , Linkins Arthur E.
Published: October 2008

Kinetic constants (Km and Vmax) were determined for surface and extracellular soluble acid phosphatases produced by two ectomycorrhizal fungi (Cenococcum geophilum Fr. and Entoloma sericeum (Bull, ex Merat) Quel.) grown in axenic culture at 2 or 50 μM KH2PO4 or sodium inositol hexaphosphate. Results for cultures supplied inorganic phosphorus were similar to those supplied organic phosphorus: surface Vmax estimates were significantly greater for 2 than for 50 μM grown isolates. The presence of constitutive extracellular soluble phosphatase activity resulted in the appearance of inorganic phosphate in media initially supplied with organic phosphorus, suggesting substrate hydrolysis in excess of phosphate uptake. No consistent relationship was found between apparent Km estimates and phosphorus treatments. The two species had surface phosphatase Vmax values differing by as much as two orders of magnitude. The magnitude of the response to phosphorus treatment differed among isolates. The response of phosphatases to changes in phosphorus at concentrations comparable with soil solution phosphorus supports the hypothesis that levels of available soil phosphorus may control ectomycorrhizal phosphatase production or activation.
Étude cytochimique ultrastructurale de la dégradation des lignines dans les résidus pariétaux de bois d'épicéa et de peuplier par le Reticulitermes lucifugus var. santonensis (Rhinotermitidae, Isoptera)
Authors: Garnier-Sillam E. , Grech I. , Czaninski Y. , Tollier M.-T. , Monties B.
Published: October 2008

Free cell-wall residues were prepared by extracting wood samples of spruce (Populus euramericana cv. Fidzi Pauley) and poplar (Picea sitchensis). These species were chosen for their lignin types: guaiacyl in spruce and guaiacyl–syringyl in poplar. The parietal residues obtained were used as the sole food for the xylophagous termite Reticulitermes lucifugus var. santonensis and were compared before and after ingestion and transit in the digestive tracts. Differences due to the mechanical action of the gizzard were found in association with chemical changes. Polysaccharides were unmasked after digestion and could clearly be observed after reaction with periodic acid – thiocarbohydrazide – silver proteinate. A fibrillary meshwork was also observed inside the lignified cell walls. Biodegradation of cell wall material was particularly clear in poplar where granules formed an electron-dense plasma when uranyl acetate – lead citrate or periodic acid – thiocarbohydrazide – silver proteinate was used as a contrast medium. A selective biodegradation of syringyl monomers in poplar parietal residues was indicated by thioacidolysis but requires confirmation. Breakdown of lignified cell walls begins with a biodegradation of the lignin network associated with or followed by the digestion of polysaccharides. Syringyl-rich lignin fractions seemed to break down faster. Whether the enzymic pathway leading to ligninolysis originates from the termite digestive cells or from the endosymbionts present in their digestive tract lumen remains to be defined. Key words: Isoptera, Reticulitermes lucifugus var. santonensis, wood, lignin, spruce, poplar.
Decomposition of Bauhinia purpurea leaf litter in a polluted and unpolluted Hong Kong waterway
Authors: Au D. W. T. , Hodgkiss I. J. , Vrijmoed L. L. P.
Published: October 2008

Decomposition of Bauhinia purpurea L. leaves in litter bags submerged in the Tai Po Kau Forest Stream (TPKFS) and the Lam Tsuen River (LTR) was investigated during the winter of 1988 and the summer of 1989. At every collection, temperature, pH, turbidity, dissolved oxygen, and biological oxygen demand (BOD5) were measured. In winter, the organically enriched LTR was categorized as polluted based on BOD5, turbidity, and heterotrophic bacteria counts, whereas the TPKFS was always relatively clean. Weight loss of leaf litter at both sites was very rapid when compared with published values and exhibited a distinct seasonal pattern. The decomposition rate of leaf litter (using the single exponential decay model) varied linearly with mean water temperature. Carbon content of the leaf litter decreased during decomposition and was, as expected, negatively correlated with the percent ash content. Except in the first 2 weeks, the nitrogen content of decomposing leaf litter decreased with time at a rate correlated with the abundance of heterotrophic bacteria in winter leaf litter (insufficient data were available in summer). Based on the results of the winter study only, the decomposition of leaf litter seems to be suppressed in the polluted river. Key words: decomposition, carbon, nitrogen, water pollution, heterotrophic bacteria.
Influence de la qualité de l'éclairement sur les corrélations entre le cotylédon et son bourgeon axillaire chez le Linum usitatissimum
Authors: Oueida Ahmed Fathi , Desbiez Marie-Odile
Published: October 2008

The precedence of one cotyledonary bud over another, as a result of the removal of one of the cotyledons, can be measured quantitatively using the precedence index, g. When g tends towards +1, it is the bud opposite to the deleted cotyledon that takes the precedence, whereas when it tends toward −1, it is the axillant one. When g is close to 0, it corresponds to a globally symmetrical population of plants, in which the bud opposite to the deleted cotyledon and the axillant bud take the precedence in an approximately equal number of plants. When the flax is taken, after decapitation and removal of one cotyledon, on deficient nutrient solution under photoperiodicity of 9 h light: 15 h dark, index g is not affected if the dark period is replaced totally by a low-energy (3 W∙m−2) red light or partly by four periods of 20 min of red light during the dark period. In contrast, blue or far red light, under the same experimental conditions, caused g to tend towards 0 for all cultivars. This effect of the blue or far red light was antagonized by a following red light treatment, which suggests the interference of phytochrome. These observations were not observed with a Knop, ion-rich nutrient solution and at 18 W∙m−2, where g index remained close to +1. Key words: Linum usitatissimum, photomorphogenesis, bud, cotyledon, correlation.
Inheritance of two mutations conferring glyphosate tolerance in the fern Ceratopteris richardii
Authors: Chun Paulette Tai , Hickok Leslie G.
Published: October 2008

Two mutant strains (G492, G343) of the fern Ceratopteris richardii, selected following X-irradiation, showed enhanced tolerance to the herbicide glyphosate in both the haploid gametophyte and diploid sporophyte generations. Segregation analysis indicated that each strain carried a different nuclear mutation that was responsible for tolerance. The two mutations were unlinked. The glt1 mutation (strain G492) showed incomplete dominance and conferred higher tolerance than the recessive glt2 mutation (strain G343). Gametophyte segregants carrying both mutations did not show enhanced tolerance relative to gametophytes carrying only glt1. For both mutants, tolerance to glyphosate did not result in reduced fitness in the absence of the herbicide. Key words: fern, Ceratopteris, glyphosate tolerant, inheritance.
Ultrastructural changes in tomato infected with tomato leaf curl virus, a whitefly-transmitted geminivirus
Authors: Channarayappa Channarayappa , Muniyappa V. , Schwegler-Berry D. , Shivashankar G.
Published: October 2008

The ultrastructural modifications in nucleus of tomato infected with tomato leaf curl virus (TLCV) included hypertrophy of the nucleolus, segregation of nucleolar components into discrete granular and fibrillar regions, appearance of electron-dense particles associated ribbon-like structures, and presence of virus particles as either loosely compacted or hexagonally close-packed symmetrical arrays. The virus particles were isometric, about 18–20 nm in diameter. In the lumen of sieve elements, virus particles occasionally formed aggregates that were cylindrically arranged and occurred in pairs. Among the organelles other than the nucleus, virus particles were found in the plastids of sieve elements. In the chloroplasts of TLCV-infected cells, considerable disturbances in the internal organization were observed. In the most severe form of degeneration, the thylakoid system was fragmented and disorganized. In some chloroplasts starch grains were abnormally large. Excessive accumulation of osmiophilic bodies in degenerating chloroplasts was prominent. Key words: leaf curl virus, geminate particles, nucleolar hypertrophy, virus particles, osmiophilic body.
Effects of temperature, hydrogen ion concentration, humidity, and light quality on disease caused by Fusarium solani f.sp. phaseoli in mung bean
Authors: Schuerger Andrew C. , Mitchell David J.
Published: October 2008

Disease caused by Fusarium solani f.sp. phaseoli in mung bean grown in hydroponic solutions was influenced by temperature and hydrogen ion concentration but not by ambient humidity or light quality. Differences in fresh weights between inoculated and noninoculated plants were greatest at 20 °C; they decreased as temperature increased to 28 °C and they were not significant at 30–36 °C. At 20 °C, 52–97% of inoculated plants wilted by 14 days after inoculation and plant fresh weights were reduced an average of 60–75% compared with noninoculated plants. Disease was similar among inoculated plants maintained at 20 °C and pH 4, 5, 6, and 7. However, when plants were maintained at 25 °C, fresh weights of inoculated and noninoculated plants were different at pH 5, 6, and 7, but they were not different at pH 4. Mature conidiophores and macroconidia were produced between 10 and 14 days after inoculation at 20 °C and by 14 days at 24 and 28 °C when the pH of the nutrient solution was maintained at 5–7. However, when plants were maintained at 20 °C and pH 4, mature conidiophores and macroconidia of F. solani f.sp. phaseoli were not observed; sporodochia and branched monophialides were disorganized and poorly developed. Results of bioassays, based on root lengths of germinating seedlings of Lactuca sativa, did not support the hypothesis that plant growth-inhibiting or growth-promoting compounds accumulated in hydroponic solutions. Key words: controlled ecological life support systems, NASA, space agriculture.
Multiplication in vitro de quelques iris à partir de raciness: aspects histologiques de l'embryogenèse somatique
Authors: Vieth J. , Laublin G. , Morisset C. , Cappadocia M.
Published: October 2008

A histo-morphological investigation of indirect somatic embryogenesis was conducted on three species of Iris. The formation of "calli I" or propagules appears somewhat like a root ramification. It is initiated in the pericycle, facing one of the xylem bundles. Fully developed, this so-called callus I differs from a rootlet by its size as well as by the complete absence of an apical meristem and the quasi absence of a root cap. In terms of external and internal structures, it is different from the typical callus of other plants as well as the callus II of Iris. The latter becomes granular on the surface and is internally parenchymatous. This type of callus has an irregular growth that suggests unequal activity of a lateral meristem. This meristem is covered by a discontinuous plectenchyma or pseudoparenchyma of variable thickness that is cytologically heterogeneous. Most of the initial cells of somatic proembryos and embryoids develop in this pseudoparenchyma, of which some fragments remain attached to the embryoids until their development is complete. Key words : Iris, roots, micropropagation, indirect somatic embryogenesis, histology.
Recognition of a pathogen and a nonpathogen by barley coleoptile cells. III. Responses of microtubules and actin filaments in barley coleoptile cells to penetration attempts
Authors: Kobayashi Issei , Kobayashi Yuhko , Yamaoka Naoto , Kunoh Hitoshi
Published: October 2008

New arrangements of microtubules and actin filaments in coleoptile cells of barley that had been inoculated with either a nonpathogen, Erysiphe pisi, or a pathogen, E. graminis, were observed by cytochemistry and confocal laser scanning microscopy. In uninoculated coleoptile cells, microtubules were oriented almost obliquely or transversely to the long axis of the cells and actin filaments almost obliquely or longitudinally. A thick actin bundle was located beneath approximately 70% of appressoria of E. pisi when the appressoria matured 3–4 h before they attempted penetration. This phenomenon occurred below approximately 30% of appressoria of E. graminis. Microtubules were gathered beneath the appressoria when and after the inoculated fungi induced cytoplasmic aggregation. This phenomenon also occurred more frequently below appressoria of E. pisi than those of E. graminis. Confocal laser scanning microscopy confirmed the localization of microtubules and actin filaments in a cortical region of the coleoptile cell beneath the appressorium. The time-course study revealed that the new arrangement of actin filaments was initiated 3–4 h prior to the fungal penetration attempt, whereas that of microtubules began at the time of initiation of cytoplasmic aggregation. The incidence of cells with newly arranged cytoskeletons was distinctly higher when E. pisi rather than E. graminis was used as inoculum. The possibilities that actin filaments might be involved in sensing the presence of the fungi and that both microtubules and actin filaments might be involved in localized resistance mechanisms are discussed. Key words: microtubule, F-actin, Erysiphe pisi, E. graminis, resistance mechanism.
Données sur le contexte végétatif lié à la floraison chez le cerisier (Prunus avium)
Authors: Lauri P. E.
Published: October 2008

A unique feature of Prunus avium L. is the distribution of growth between two types of morphologically and functionally distinct branches: auxiblasts and brachyblasts. The first ones are perennial and bear flowers at the basis of annual growth units. They are determinant for the architecture of the tree. The second type, born as lateral ramifications on the previous ones, have a much shorter life and support the flowers. A morphometric study was conducted on the growth units of the different types of ramifications in their primary phase of growth, on young and aged trees. It was showed that floral zones are characterized by a predominance of the foliar components over the stem components of the ramification. On the opposite, the vegetative zone of the auxiblasts is characterized by a predominance of the stem component. To designate these two phenomena, the terms "foliarization" and "axialization" were coined. With gradual aging of the tree and parallel evolution of the auxiblasts, toward progressively shorter as well as less and less ramified structures, an increasing preponderance of the leaves over the stem was observed or, to use the new terminology, a foliarization of the ramifications. In the meantimes, these become invaded by flowers. This type of morphometric study allows to describe simultaneously the progressive aging of the vegetative system along with the evolution of the distribution of flowering on different types of ramifications. Key words: architecture, morphometry, Prunus avium, aging, flowering. [Journal translation]
Increased aggressiveness of Alternaria macrospora, a causal agent of leaf blight in cotton monoculture
Authors: Holguin Gina , Bashan Yoav
Published: October 2008

Consecutive, single-crop cultivation continues to be practiced worldwide as a matter of necessity. The monoculture of cotton now practiced in Israel results in annual outbreaks of leaf blight epidemics. Pathogenic isolates of the causal agent, Alternaria macrospora, were field collected for 6 years and inoculated onto cotton plants under controlled environmental conditions. We were able to demonstrate that the aggressiveness (virulence and fitness) of the pathogenic isolates increased over the years. The modified aggressiveness was manifested as follows: (i) an increase in the number of lesions per leaf; (ii) an increase in the size of the lesions; (iii) a decrease in the time required for symptom expression; (iv) an increase in the viability of the pathogen spores after exposure to a normally lethal temperature; and (v) a decrease in the wetting period required for symptom expression. We conclude that agricultural monoculture can accelerate evolution in the aggressiveness of this plant leaf pathogen. Key words: leaf blight of cotton, Alternaria, aggressiveness, virulence, fitness.
Influence of rainfall and grazing on belowground biomass dynamics in a dry tropical savanna
Authors: Pandey C. B. , Singh J. S.
Published: October 2008

Root biomass and its variation with time and soil depth were studied in ungrazed and grazed treatments, in a seasonally dry tropical savanna. A greater proportion of belowground biomass was located in the 0 – 10 cm soil depth in the rainy season compared with the summer season. In contrast, in the 10 – 50 cm soil profile, belowground biomass was greater in summer than in the rainy season. Peak belowground biomass in ungrazed savanna was not correlated to the rainfall in the early part of the rainy season, but it was correlated to total rainfall received in the later part of rainy season. Apparently the belowground component responds quickly to the rainfall events and generates growth pulses in the aboveground vegetation. Peak canopy biomass increased rapidly with the increase in peak belowground biomass and then plateaued, indicating a greater potential for accumulation of biomass belowground than aboveground. Grazing reduced belowground biomass by 41 – 55%. Maximum reduction occurred in the heavily grazed savanna. Peak belowground biomass was inversely related to grazing intensity. Key words: belowground biomass, grazing intensity, phased root growth, rainfall variability, tropical savanna.
Autumn distribution of marine Pythiaceae across a mangrove–saltmarsh boundary
Authors: Newell Steven Y.
Published: October 2008

Zoosporic fungi of the Pythiaceae, especially Halophytophthora vesicula, were present at high frequency (≥ 90%) on autumn-shed leaves both north and south of a mangrove–saltmarsh boundary (Florida–Georgia, U.S.A.). Submerged, decaying leaves of mangroves (three species), other trees (including conifers), shrubs, and vines bore H. vesicula. Halophytophthora bahamensis was also found north of the mangrove belt but at frequencies ≤ 10%. Halophytophthora kandeliae was found only within the mangrove environment. Leaves of intertidal grasses (Spartina and Juncus) yielded low frequencies (≤ 20%) of Halophytophthora spp., but Pythium grandisporangium exhibited frequencies of up to 40–43% on leaves of trees and of Spartina alterniflora. Key words: marine oomycetes, mangrove, saltmarsh, Avicennia germinans, Halophytophthora vesicula, Pythium grandisporangium.
Petrography and geochemistry of epidote alteration patches in gabbro dykes at Matagami, Quebec
Authors: Harrigan D. B. , MacLean W. H.
Published: October 2008

Light colored patches, ranging to 0.5 m across, are common in some gabbro dykes and volcanic rocks at Matagami. Skeletal ilmenite and outlines of plagioclase grains, traced from patches to fresh gabbro, indicate an origin by alteration and metasomatism. Gabbro near patches is composed of actinolite, hornblende, labradorite, and composite ilmenite–magnetite grains, with minor epidote, albite, quartz, and chlorite. Patches are mainly epidote, quartz, hornblende, with minor albite, chlorite, apatite, and sphene. Compared to gabbro, patches are enriched in CaO, SiO2, and P2O5, and depleted in FeO*, MgO, and alkalis.Present features of the gabbro developed in three stages: (1) magmatic, (2) autometamorphic (or deuteric), and (3) regional metamorphic. The patches formed during stage 2 by channeling of fluids through permeable zones in cooling dykes and overlying volcanic rocks.
Mercury sorption and desorption characteristics of some Ottawa River sediments
Authors: Ramamoorthy S. , Rust B. R.
Published: October 2008

Bed sediments of the Ottawa River downstream of the Gatineau River confluence are predominantly sandy, with variable organic contents, chiefly wood chips. Mercury sorption by these sands was studied at constant temperature using a mercuric-ion specific electrode, and varying added [Hg2+] and pH. Sorption rates are highest for organic-rich sands, but variation in particle size is apparently not sufficient to reveal sorption trends related to this parameter. Sorption data were fitted to a linear form of the Langmuir equation, from which sorption maxima and mercury bonding coefficients were derived. The maxima do not vary between samples, whereas the bonding coefficient relates most closely to organic content. Mercury sorption was little affected by pH.Desorption rates are low: less than 1% Hg was leached from sediment after 70 h agitation in distilled water, and a similar amount in fulvic acid solution. The mercury–sediment bonding is evidently much stronger than that between fulvic acid and mercury, irrespective of organic content of the sediment.
Silurian stratigraphy and paleogeography, Pointe Verte area, New Brunswick, Canada
Authors: Noble J. P. A.
Published: October 2008

On the basis of recent field studies the Silurian stratigraphy of the Pointe Verte area, New Brunswick, is revised. Three new formation names are proposed and type sections designated. These are the Armstrong Brook Fm., the Limestone Point Fm., and the Petit Rocher Fm., which are described and their stratigraphic relationships with other formations established. Facies relationships among all the Silurian formations are considered, allowing preliminary conclusions to be drawn on the depositional history and paleogeography of the area. Rapid lateral and vertical changes in facies are related to basin instability and to changes in paleogeography, especially about Llandovery C4–C5 time.
Paleomagnetism of the Great Slave Supergroup, Northwest Territories, Canada: the Stark Formation
Authors: Bingham D. K. , Evans M. E.
Published: October 2008

Paleomagnetic results from 55 sampling sites throughout the Stark Formation are reported. The known stratigraphic sequence of these sites enables the behaviour of the geomagnetic field in these remote times (1750 m.y.) to be elucidated. Two polarity reversals are identified and these represent potentially useful correlative features in strata devoid of index fossils. One of these is investigated in detail and indicates that behaviour of the geomagnetic field during polarity reversals was essentially the same in the early Proterozoic as it has been over the last few million years. The pole position (145°W, 15°S, dp = 3.5, dm = 6.9) lies far to the west of that anticipated from earlier results, implying further complexity of the North American polar wander curve. Possible alternatives to this added complexity are discussed.
Description and origin of banded deformation structures. II. Rheology and the growth of banded perturbations
Authors: Cobbold P. R.
Published: October 2008

This paper offers a generalized mechanical explanation for the origin and development of bandlike deformation structures such as shear zones, mylonite zones, kink bands, 'pressure-solution' seams, extension gashes, and similar folds.Methods of continuum mechanics are used to examine permissible variations in strain rate, stress, and rheological properties across a region containing ideal banded perturbations. For bands to develop, the rheological properties must vary across the banding. The physical basis for this variation is a corresponding variation in microstructure or chemical composition, influenced in turn by finite deformation, stress, and temperature. Many rocks are likely to soften or harden during progressive deformation and these changes may be enhanced by thermal or other agents. Deformation softening (including strain softening and rotation softening) is a cause of instability and has two effects: first, the deformation tends to accelerate under constant stress; second, the deformation tends to become locally perturbed. Deformation hardening has compensatory effects.Banded perturbations do not appear spontaneously in a deforming rock, but evolve towards an ideal banded form by processes of nucleation and propagation. Evidence for these processes comes from theoretical analysis, experimental data, and observation of bandlike structures that have formed as a result of natural processes of deformation.
Tidal-current control of submarine morphology at the mouth of the Miramichi estuary, New Brunswick
Authors: Reinson G. E.
Published: October 2008

The mouth of the microtidal Miramichi estuary, New Brunswick, is enclosed by a barrier-island system which is cut by two major tidal inlets. The submarine morphology adjacent to these inlets indicates the presence of large tidal deltas which formed predominantly by tidal-current processes. The extensive shoal water on the landward side of the barrier is due to the landward transport of sand through the inlets and the deposition of this sand as coalescing flood-tidal delta deposits. The creation of an artificial channel inside the main inlet in the late 19th century, and its maintenance since that time, have resulted in substantial channel-flow bypassing of the natural channel seaward of the barrier. This promoted the scouring of a new channel through the ebb-tidal delta shoal.Large tidal deltas apparently are not common morphological features of estuaries on microtidal, barrier-island coastlines, but they do occur at the entrances of very large microtidal estuaries such as the Miramichi. In such cases they are usually completely subtidal, and much larger than tidal deltas of mesotidal estuaries reported in the literature. Rather than tidal range, the tidal prism, which takes into account both tidal range and estuary surface area, may play the major role in the formation of tidal deltas in both mesotidal and microtidal estuaries.
Interglacial chronology of the Rocky and Mackenzie Mountains based upon 230Th–234U dating of calcite speleothems
Authors: Harmon Russell S. , Ford Derek C. , Schwarcz Henry P.
Published: October 2008

Fifty-four 230Th–234U ages for 36 different speleothems from mountain karst areas of the Rocky and Mackenzie Mountains cluster into five distinct age groups. Speleothems of the two oldest groups are particularly massive and ornamented. Several samples exhibit complex growth histories with successive periods of deposition separated by periods of interrupted growth and (or) erosion. Attributing episodes of deposition to interglacials and nondeposition to glacial periods, interglacials are recognized at (i) present to about 15 ka; (ii) 90–150 ka; (iii) 185–235 ka; (iv) 275–320 ka; and (v) ≥ 350 ka. These interglacials correlate well with periods of high sea stand and warm climate observed in the marine paleoclimate record. It appears that during the broad period 275–400 ka interglacial conditions were strongly predominant in the mountains, producing effects suggestive of a 'great interglacial'.
Partial melting and mineral-stability boundaries and their bearing on the seismic exploration of the lithosphere in Canada
Authors: Hall D. H.
Published: October 2008

The possible velocity transitions, if the uppermost mantle beneath Canada conforms to the pyrolite–peridotite model, have been explored. It is found that partial melting of pyrolite or peridotite with a small amount of water would occur at depths consistent with known velocity transitions, in particular with the low velocity zones for S waves that have been interpreted as occurring beneath various regions of Canada. In addition, a spinel–garnet transition would occur for a pyrolite–peridotite mantle at a depth of 50–60 km beneath the shield, and somewhat deeper to the south and east of that region. These depths correspond to velocity transitions which have been detected in the mantle. Reasonable variations in composition could lead to variations of up to 30 km in these depths. The outflow of basalt in the Archean beneath the Lake-of-the Woods area, through its effect on mantle composition (and thus on the depth to the spinel–garnet transition) may explain the depression there in a shallow mantle refractor mapped by B. Gurbuz.
An alternative view of the Gondwana Paleozoic apparent polar wander path
Authors: Schmidt P. W. , Morris W. A.
Published: October 2008

A reappraisal of Paleozoic paleomagnetic data from Australia is given. An alternative apparent polar wander path is suggested after adopting the reversed polarity option for pre-Devonian poles. Hitherto 'anomalous' Siluro-Devonian pole positions thus appear as conformable. This new polar path is compared to Paleozoic paleomagnetic data from other Gondwana continents which are seen to support the Australian path. The new path, in turn, supports the interpretation of Paleozoic glacial deposits being indicative of high latitudes and the transgression of an ice cap.It is suggested speculatively that systematic polar wandering of the type described here may indicate a systematic pattern of plate motions and consequently, systematic tectonic processes.
Étude pétro-structurale des chevauchements ductiles himalayens sur la transversale de l'Everest–Makalu (Népal oriental)
Authors: Brunel Maurice , Kienast Jean-Robert
Published: October 2008

Tectonic and microtectonic data in eastern Nepal indicate that the major observed thrusting (100 km) on the Main Central Thrust (MCT) postdates the Barrovian metamorphism of the High Himalaya gneisses. This result, at variance with the famous "reverse metamorphism model," better explains the abnormal metamorphic superpositions in the Himalayas and accounts for the lack of high-pressure assemblages under the thick, allochtonous High Himalaya Tibetan slab.Pressure and temperature estimates by microprobe analysis on plagioclase, biotite, garnet, kyanite, sillimanite, and cordierite assemblages are presented for samples collected along the MCT shear zone and across the gneiss slab in the Everest–Makalu area. Since there is very little difference in pressure at the front of the slab (Kathmandu Klippe) and its root, these estimates support the existence of important late metamorphic thrusting. The decrease of pressure towards the top of the gneiss pile, combined with a small temperature increase, explains the kyanite–sillimanite transition. The reverse metamorphism model, which implies refolded isograds, predicts heat loss by conduction throughout the sole of the thrust; pressure–temperature variations and kyanite–sillimanite transition phases more likely reflect a late heat supply in the upper part of the gneisses. Intrusion of leucogranitic bodies, confined to the interface with the Tethyan sediments, could account for this heat supply.A new tectonic evolution model of the Himalayan intracrustal thrusts is discussed. Without completely denying the existence of a reverse metamorphism synchronous with the phases of early shearing, it can be shown that the metamorphic zonation seen at present was governed by the structure of the later shearing.
Origine et évolution du marais tourbeux de Keswick, Ontario, par l'analyse pollinique et macrofossile
Authors: Dinel H. , Richard P. J. H. , Levésque P. E. M. , Larouche A.
Published: October 2008

The objectives of the present study were to explain the origin and to reconstitute the different phases of the paleovegetation of the Keswick marsh, Ontario. Palynological evidence was used to key out the regional and extra-local paleovegetation, and macrofossils analysis served to establish the history of the vegetation at the field site. The data showed that in the vicinity of Lake Simcoe the origin of the marsh was closely associated with the changes in the climatic conditions that favored the development of an environment suitable for peat-forming plant communities; 2.4 m of peat accumulated in the last 4000 years on a washed silty clay. The macrofossils of hardwood species, seeds of Aralia racemosa, and sporangia of Polypodiaceae at the base of the deposit indicated that a mixed forest, composed mainly of deciduous species surrounded by tamaracks, prevailed prior to the initiation of peat accumulation. Furthermore, additional vegetation changes occurred, notably the replacement of an arboreal swamp vegetation by an herbaceous marsh, followed by a shrub–herb marsh and then an herbaceous marsh, recently drained and cultivated.
Probable marsupial footprints from the Cretaceous sediments of British Columbia
Authors: Sarjeant W. A. S. , Thulborn R. A.
Published: October 2008

Probable marsupial footprints, exhibiting syndactyly of digits II and III of the pes, are described and placed into a new ichnogenus and species, Duquettichnus kooli. The type specimen is from the Cretaceous (late Aptian to early Albian) sediments of the Peace River canyon near Hudson Hope, British Columbia. This constitutes the first evidence for syndactyly among Mesozoic mammals, whose postcranial skeletons are very poorly known. It may well also constitute the earliest evidence for the presence of marsupials in Mesozoic North America.
A candidate stratotype for the Precambrian–Cambrian boundary, Fortune Head, Burin Peninsula, southeastern Newfoundland
Authors: Narbonne Guy M. , Myrow Paul M. , Landing Ed , Anderson Michael M.
Published: October 2008

The Burin Peninsula exhibits an exceptionally thick and essentially continuous succession of marine strata through the Precambrian–Cambrian transition. Fossils are abundant and include trace fossils, small shelly fossils, vendotaenid algae, soft-bodied megafossils, and microfossils. The Burin Peninsula is readily accessible and has long been considered a potential area for a Precambrian–Cambrian boundary stratotype.A continuous section through the upper part of member 1 and all of member 2 of the Chapel Island Formation is exposed at Fortune Head, and this section is herein proposed as a global stratotype for the Precambrian–Cambrian boundary. The boundary horizon is located 2.4 m above the base of member 2 of the Chapel Island Formation. This horizon marks the base of the basal Cambrian Phycodes pedum (ichnofossil) Zone and immediately overlies the top of the Late Precambrian Harlaniella podolica (ichnofossil) Zone. Shelly fossils (sabelliditids) first appear a few metres below the proposed boundary. Soft-bodied megafossils, carbonaceous impressions of vendotaenid algae, and organic-walled microfossils occur both below and above this boundary and enhance global correlation with this section.Fossils of the Rusophycus avalonensis (ichnofossil) Zone first appear midway through member 2 (approximately 135 m above the proposed boundary) and occur commonly throughout the upper part of the Chapel Island Formation and the overlying Random Formation. Calcareous small shelly fossils (?Circotheca sp.) appear near the top of member 2 (approximately 400 m above the proposed boundary), and a more diverse Aldanella attleborensis small shelly fossil assemblage characterizes the uppermost strata of member 3 and all of member 4 of the Chapel Island Formation (approximately 550–650 m above the proposed boundary). The lowest trilobites, representatives of the Callavia broeggeri Zone, first appear more than 1000 m above the proposed Precambrian–Cambrian boundary.
Adsorption of uranium from groundwater by common fracture secondary minerals
Authors: Milton G. M. , Brown R. M.
Published: October 2008

Laboratory studies have been performed on the uptake of uranium by the chief secondary minerals identified on fracture surfaces in groundwater flow systems of the Canadian Shield. The extent of adsorption from prepared solutions onto these materials, i.e. ferric oxyhydroxide uptake > chlorite uptake > calcite uptake, was similar to that previously observed in place on field samples.Although adsorption on the oxyhydroxide proceeds rapidly to near equilibrium in about 3 weeks, slower, two-stage processes have been postulated for uranium uptake by both chlorite and calcite. In some cases the times required to reach equilibrium are greater than 1 year.
Thermal regime of peatlands in subarctic eastern Canada
Authors: Moore T. R.
Published: October 2008

Temperatures were measured to 2 m depth at six peatland sites in the Schefferville area, northern Quebec, from July 1982 to September 1984. The sites varied in their plant cover, type of peat, and depth of snow, and two sites represented string and flark morphology. During the summers, the surface layers (5 – 10 cm) reached temperatures of 15–20 °C and the 10 °C isotherm reached depths of 50–150 cm, depending on the site characteristics and the influence of the preceding winter conditions. The progression of the 10 °C isotherm downwards could be predicted from climatic variables, such as cumulative thawing degree-days. During the winter, the 0 °C isotherm reached depths of between 20 and 90 cm, based primarily on the thickness of the insulating snowpack and its development during the winter. The surface layers (5 – 20 cm) of the peat remain close to freezing (−1 to −3 °C), despite the very cold air temperatures (−20 to −30 °C). Examination of a cooling and a warming sequence at the string and flark sites reveals that the string near the surface is about 2 °C colder than the flark during the winter, and that during the early summer it can be 8 – 14 °C warmer than the flark. Differences in thermal regimes between sites and between seasons are interpreted in terms of the major climatic factors and the characteristics of the sites.
Advance and retreat glacigenic deformation at Williams Lake, British Columbia
Authors: Broster Bruce E. , Clague John J.
Published: October 2008

Glacigenic deformation structures at Williams Lake, British Columbia, occur within stratified Quaternary sediments that both overlie and underlie lodgement till of the last (Fraser = Late Wisconsinan) glaciation. The main structures in sediments below the lodgement till are faults, joints, and clastic dikes produced by glacier overriding during Late Wisconsinan time. The orientation of these structures is closely related to the direction of glacier flow at Williams Lake. Their character and stratigraphic position suggest that the substrate in this area was partly frozen and partly unfrozen when covered by ice during the Fraser Glaciation.A different suite of glacigenic deformation structures is found in sediments above the lodgement till. These include complex folds, load casts, and high-angle faults formed during deglaciation as a result of loss of ice support and collapse. These structures yield information on the local pattern of ice decay, but bear no relationship to the regional direction of Late Wisconsinan glacier flow.
Cenozoic deformation and Mesozoic abandoned spreading centre in the Tagus Abyssal Plain (west of Portugal): results of a multichannel seismic survey
Authors: Mauffret A. , Mougenot D. , Miles P. R. , Malod J. A.
Published: October 2008

The seismic stratigraphy of the sedimentary section that fills in the Tagus Abyssal Plain is specified by means of new multichannel seismic data. Six sedimentary sequence units are identified. These, ranging from Late Jurassic to Recent, have been dated by extrapolation of Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) drilling results and from sampling by dredging and submersible surveys. Based on this stratigraphic calibration and other geophysical data, a geodynamic evolution can be established for the Tagus Abyssal Plain. Faulting and folding in these sedimentary units clearly indicate that both the Portuguese Margin and the adjacent oceanic crust were deformed by a Miocene compressive event. An Oxfordian–Kimmeridgian rifting in the Lusitanian Basin and on the Portuguese Margin may herald a sea-floor spreading in the Tagus Abyssal Plain. The continent–ocean boundary is marked by landward-dipping reflectors similar to those observed along the Canadian margin. The oceanic structure of the Tagus Abyssal Plain is compared with those of the small oceans and (or) slow-spreading-rate centres. The eastern Tagus Abyssal Plain could be underlain by a Latest Jurassic (M-21)–Earliest Cretaceous (M16) spreading centre that was abandoned in Earliest Cretaceous (142 Ma), whereas the western Tagus Abyssal Plain could be underlain by a younger crust (from M10 to J) formed after a ridge jump. This younger oceanic domain may have a western complement in the Newfoundland Basin.
Late Proterozoic arc–continent and continent–continent collision in the pan-African trans-Saharan belt of Mali
Authors: Caby Renaud , Andreopoulos-Renaud Uranie , Pin Christian
Published: October 2008

The Tilemsi magmatic arc, preserved along the suture zone of the pan-African trans-Saharan belt of northern Mali, crops out as a series of northeast- to north-northeast-trending strips along the Tilemsi Mesozoic trough and is about 100 km in width. The volcanic arc series includes pillowed metabasalts of tholeiitic character and associated with rhyodacites. Overlying sedimentary rocks are turbiditic volcanic greywackes. They are progressively recrystallized into grey gneiss in the vicinity of gabbro-noritic and dioritic intrusions. U/Pb zircon dating of a crosscutting metaquartz diorite gives a nearly concordant age of [Formula: see text], while that of a plagiogranite mobilizate associated with the grey gneiss is [Formula: see text]. Initial Nd and Sr isotopic compositions of two metaquartz diorites (εNd730 = +6.6, +6.3; (87Sr/86Sr)i = 0.7024) are in a agreement with a depleted mantle source similar to modern intraoceanic arcs. Isotopic compositions of two Tilemsi metagreywackes (εNd730 = +5.8, +4.3; 87Sr/86Sr ≈ 0.7027) exclude any significant derivation from an older sialic source and support the ensimatic origin of the magmatic arc. A U/Pb zircon age of 635 ± 5 Ma has also been obtained on a pretectonic granodiorite batholith at the eastern margin of the arc. Isotopic composition of this intrusion (εNdi = −6.0, −6.4; (87Sr/86Sr)i = 0.7046) illustrates the lack of a genetic link between the 730 Ma old, mantle-derived magmas and these granitoids, which originated from a crustal reservoir. This change in magmatic source is interpreted as the result of accretion of the ensimatic arc along the eastern continent, preceding continent–continent collision during the pan-African event.
Constructional features of the Troodos ophiolite and implications for the distribution of orebodies and the generation of oceanic crust
Authors: Hall James M. , Walls Charles C. , Yang Jing-Sui
Published: October 2008

The map pattern of the Troodos ophiolite in Cyprus is an expression of a simple, elongate anticlinal structure. The cross-sectional form of the anticline can be described by a sinusoidal dip model. On the northern flank of the anticline, the thickness of various units, number of gossans, etc., were measured along profiles, at 2.5 km intervals normal to strike, using existing maps supplemented by new observations. Profiles are approximately perpendicular to the spreading direction during crustal construction, and uncertainties in unit thickness are smaller than the range of unit thicknesses.Data on the profiles were analyzed quantitatively by harmonic analysis using the Fourier transform method. The harmonic analysis discloses cyclic variation in the thickness of major units, number of gossans, etc., that provides a link with the regular spacing of five groups of Cu–Fe–Zn orebodies. Groups of orebodies occur preferentially where sheeted dikes are at a shallow crustal depth, sheet and massive flows and dikes are common in the extrusives, the sediment–extrusive interface is at a relatively low elevation, and gossans and umbers are well developed. This association has the potential for providing an exploration tool in Cyprus and elsewhere. It can be accounted for in terms of the regular arrival in the crust of batches of mantle-derived magma. Arrival of a batch of magma in the crust would have been followed by voluminous sea-floor eruptions (which often formed sheet or massive rather than pillowed flows), rapid extension and subsidence, and enhanced hydrothermal circulation, a combination of circumstances leading to an increased probability of formation and preservation of orebodies.The thickness variations provide context for the few measured thickness values for in situ oceanic crust. The wide range in thickness values for the Cyprus ophiolite and the elevation of the sediment–extrusive interface suggest that the ophiolitic ocean crust was probably formed in a low-spreading-rate environment.