bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of naphthaleneacetic acid on the formation of lateral roots in the adventitious root of Allium cepa: number and arrangement of laterals along the parent root
Authors: Lloret Pedro G. , Pulgarín Antonio
Published: October 2008

The exogenous application of an auxin (α-naphthaleneacetic acid) to the adventitious root of Allium cepa L. promotes lateral root formation and inhibits main root elongation. If the adventitious roots are released from the influence of this auxin, they may resume elongation after 10−5 M but not after 10−4 treatment. Auxin leads to the appearance of late-forming root primordia intercalated between previously formed laterals. The arrangement of laterals along the adventitious root is another feature altered by treatment, i.e., control roots develop the same number of laterals throughout the length of the zone in which laterals appear, whereas in treated roots the number of laterals rises steadily as the distal end of this zone is approached. In 10−5 M auxin-treated roots, no increase in the number of laterals occurs in basal zones of the parent root, whereas treatment with 10−4 M naphthaleneacetic acid leads to a sharp rise in the number of laterals formed at these zones. Our results suggest that the basal part of onion roots is less sensitive than the apical portion of the effects of naphthaleneacetic acid. This chemical seems to have a rejuvenating effect on cells of the pericycle, enabling them to initiate lateral primordia when under normal conditions they would no do so. Key words: Allium cepa, auxin, lateral root, naphthaleneacetic acid, onion.
Participation du métabolisme glucidique à l'orientation organogène de tissus du Cichorium intybus cultivés in vitro
Authors: Lefebvre R. , Vasseur J. , Backoula E. , Couillerot J.-P.
Published: October 2008

6-Benzylaminopurine and α-naphthaleneacetic acid each stimulate inulase and invertase activities in Cichorium intybus, although these two hormones induce different organ formations. Unlike auxin, however, cytokinin allows a partial elaboration of sucrose reserves without changing callus growth. Furthermore, addition of an external source of glucose inhibits inulase and invertase activities, which results in an increase in sugar reserves (sucrose and starch) in the bulky callus. This activity differs from that observed with α-naphthaleneacetic acid, which is characterized by an increase in protein synthesis and water absorption in the tissues. Root initiation also requires additional sugars with α-naphthaleneacetic acid; gibberellic acid improves these results by promoting the catabolism of external sugars rather than a conversion into tissue reserves. Key words: organogenesis, Cichorium intybus, carbohydrates, in vitro cultures.
L'Aphanomyces euteiches des luzernières du Québec: isolement, morphologie et variabilité de la croissance et du pouvoir pathogène
Authors: Beghdadi Abdellatif , Richard Claude , Dostaler Daniel
Published: October 2008

Sixteen strains of Aphanomyces euteiches were obtained from alfalfa seedlings by a baiting technique. They were found in the soil of 10 out of the 12 alfalfa fields sampled. In spite of some morphological variabililty, these strains were not taxonomically distinguishable from one another. They had different cultural characteristics (minimal, maximal, and optimal growth temperatures). Their pathogenicity was tested on alfalfa, garden pea, green bean, and garden beet. The green bean was lightly affected and a wide spectrum of pathogenicity was observed on alfalfa. Four pathogenicity groups were distinguished: (i) 13% of the strains were nonvirulent to the four hosts, (ii) 25% were specific to alfalfa, (iii) 25% were more virulent to alfalfa than to garden pea, and (iv) 37% were slightly pathogenic to both alfalfa and garden beet. The last group was characterized by a reduced mycelial growth at temperatures above 24 °C and the symptoms noticed on garden beet were similar to those caused by Aphanomyces cochlioides. Key words: Aphanomyces euteiches, alfalfa, garden beet, garden pea, green bean, pathogenicity.
A positive allelopathic effect of corn cockle, Agrostemma githago, on wheat, Triticum aestivum
Authors: Søgaard Bodil , Doll Hans
Published: October 2008

The effect of corn cockle on wheat was studied during germination and on adult plants in a growth chamber. Seedling length of wheat germinated together with corn cockle for 5 days increased 13%. Wheat growing together with corn cockle in pots to maturity had a statistically significant higher wheat biomass and grain production than wheat growing alone. However, two other experiments with adult plants harvested before wheat maturity showed no effect of corn cockle on wheat production per pot. Within the pots the presence of corn cockle influenced wheat in all three experiments. Wheat plants growing at the same position as a corn cockle plant were 20 to 50% larger than wheat plants standing alone. Key words: growth stimulation, allelopathy, competition, interference.
The Terrace earthquake of 5 November 1973
Authors: Rogers Garry C.
Published: October 2008

On 5 November 1973 at 12 h 36 m 17 s UT, a shallow focus earthquake (ML = 4.7, mb = 4.2) occurred about 20 km southwest of Terrace, British Columbia near 54.4 °N and 128.8 °W. The area has been aseismic in historic time. The earthquake appears to have no relation to nearby hot springs or to the geologically recent volcanism in the area. It was felt to distances of 120 km and the maximum intensity observed was V on the Modified Mercalli scale. Only minor damage was reported. The inclusion of this earthquake in seismic risk calculations slightly elevates the risk computed for Terrace.
Volcanogenic cherts in the late Precambrian Conception Group, Avalon Peninsula, Newfoundland
Authors: Hughes Charles J.
Published: October 2008

Bedded rocks of cherty appearance are locally abundant and conspicuous in the late Precambrian Conception Group of the Avalon Peninsula, southeast Newfoundland. Structural, petrographical, and chemical data from a well exposed locality near St. John's indicate that these beds are tuffaceous, predominantly of acid vitric composition, formed by pyroclastic material derived from contemporaneously active subaerial volcanic sources accumulating in sea water, and subjected to submarine transport. Appreciable quantities of acid material were thus erupted in 'Conception time.'
K–Ar ages of amphiboles from the Bay of Islands ophiolite and the Little Port Complex, western Newfoundland, and their geological implications
Authors: Archibald D. A. , Farrar E.
Published: October 2008

Over 20 K–Ar ages and one 40Ar/39Ar incremental heating analysis of amphiboles from the Bay of Islands ophiolite complex and the Little Port Complex, western Newfoundland, are reported. Amphiboles were obtained from granitic rocks and amphibolites which outcrop in the northern part of the Little Port Complex, and from the sheeted dykes and gabbros and from the basal metamorphic aureole of the ophiolite. The results indicate that obduction of the ophiolite took place approximately 470 m.y. ago and that movement, associated with the emplacement of the Humber Arm allochthon, ceased after 455 m.y. BP. It is postulated that initial argon in amphiboles taken from the basal metamorphic aureole of the ophiolite has resulted in some anomalously high ages.Since the stratigraphic and paleontological relationships in the Bay of Islands are are well known, the dates for obduction and final movement represent additional geochronological reference points in the lower to middle Ordovician time scale.
Early deformational history of Archean rocks in the Vermilion district, northeastern Minnesota
Authors: Hudleston Peter J.
Published: October 2008

Precambrian sedimentary and volcanic rocks of the Vermilion district in northeastern Minnesota were deformed and weakly metamorphosed during batholith emplacement about 2700 m.y. ago. Two main episodes of folding and deformation. F1 and F2 have previously been recognized in the Tower area. The F2 folds are open to tight, and for the most part plunge steeply to the east in near-vertical axial surfaces. The major F1 folds are isoclinal, with near-horizontal hinge lines. A metamorphic fabric consists of a slaty cleavage parallel to the axial surfaces of the F2 folds and a mineral lineation sub-parallel to the fold hinges.Finite strain was determined using clasts in the coarser sedimentary/volcanoclastic units. The maximum extension (λ1) direction is parallel to the mineral lineation and the minimum extension (λ3) direction is normal to the cleavage. The strain is of constrictional type where the mineral lineation is dominant and of flattening type where the cleavage is dominant. The strain data can best be accounted for in terms of a single deformation, that producing the F2 folds. This is paradoxical because fold style indicates that the F1 deformation was at least as intense as the F2. The problem can be resolved if the F1 folds were of soft sediment origin, resulting from downslope slump movements, such that the clasts remained internally unstrained during this deformation. A single tectonic deformation, involving lateral compression and vertical extension between the two intruding batholiths, satisfactorily accounts for the strain data, the development of the F2 folds, and the present overall structural configuration.
Focal parameters of four Sverdrup Basin, Arctic Canada, earthquakes in November and December of 1972
Authors: Hasegawa H. S.
Published: October 2008

Fault plane solutions are derived for the four largest magnitude (Ms 5.1–5.7) earthquakes which occurred during the months of November and December, 1972, and which are part of the Byam Martin Channel earthquake swarm. The preferred fault plane solutions of all four have dextral strike-slip motion in a northeasterly direction on steeply dipping (approximately 80°) fault planes. For the December 27 earthquake, which has the largest Ms (5.7), the fault motion is almost pure strike slip and the focal depth is shallow, being just below the base of the Sverdrup Basin. Forthe November 19, 21, and December 28 earthquakes which have smaller Ms (5.1–5.2), the fault plane solutions have an appreciable dip-slip component (normal faulting) and the foci are at intermediate crustal depths. The two known active tectonic processes in the Arctic do not correlate with the fault plane solutions: active spreading at the Arctic mid-oceanic ridge (Gakkel or Nansen Ridge) cannot account for the orientation of the stress vectors from fault plane solutions; postglacial uplift predicts opposite dip-slip motion to what is derived from fault plane solutions. The proposed triggering mechanism for the earthquake swarm in the Byam Martin Channel is attributed to remanent stresses (predominantly horizontal and of unknown origin) acting upon a (heterogeneous) source region that is weakened by reactivated localized intrusions.
Resedimented conglomerates of Huronian (lower Aphebian) age, from the north shore of Lake Huron, Ontario, Canada
Authors: Long Darrel G. F.
Published: October 2008

Conglomeratic rocks are present near the top of a dominantly arenaceous sequence, previously ascribed entirely to the Huronian Mississagi Formation, in a belt extending for about 60 km east of Blind River, on the north shore of Lake Huron. These conglomeratic rocks and the massive and planar laminated sandstones which overlie them are herein named the Lauzon member, after the thickest exposed development of the sequence at Lauzon Lake in Striker Township. The presence of dropstones in the sequence at Lauzon Lake suggests that the member is best considered as part of the Bruce Formation. Conglomeratic rocks within the Lauzon member include granule-supported boulder, cobble, and pebble conglomerate; sand-supported cobble and pebble conglomerate; intact framework graded and non-graded pebble and cobble conglomerates; stratified conglomerates and conglomeratic sandstones; and disrupt framework conglomerates. These conglomeratic rocks lack abundant mud-grade matrix material and, hence, are readily distinguished from (glaciogenic?) mixtites of the Ramsay Lake, Bruce, and Gowganda Formations. Conglomerates of the Lauzon member were probably deposited from sediment gravity flows within a series of subaqueous fans or fan head valleys which may have been initiated by contemporaneous movements along a precursor to the Murray Fault system at the onset of the Bruce glaciation.
Silurian stratigraphy and oppositional environments: Charlo – Upsalquitch Forks area, New Brunswick
Authors: Lee H. J. , Noble J. P. A.
Published: October 2008

Seven distinctive lithologie units are recognized and described from the Charlo – Upsalquitch Forks area, northern New Brunswick. Four of these units are equated with the Matapedia Limestone and the Limestone Point, La Vieille, and Bryant Point formations of adjacent areas. In addition three new units are defined, described, and placed in the local and regional stratigraphic framework. These are the informally named Siltstone Unit, Grit Unit, and Conglomerate Unit.Although the lithofacies and biofacies changes of the area are rapid and complex the sedimentologic and paleoecologic evidence indicates a dominantly shallowing trend throughout the Late Ordovician to at least Middle Wenlock times. A reversal of this trend during the Early Wenlock in the northeast part of the area is indicated by the deeper water facies of the lower La Vieille Formation.
Wrangellia—A displaced terrane in northwestern North America
Authors: Jones David L. , Silberling N. J. , Hillhouse John
Published: October 2008

A large terrane extending along the Pacific margin of North America, from Vancouver Island, British Columbia, to south-central Alaska, is characterized throughout by similar sequences of Triassic rocks. These rocks, including a thick pile of tholeiitic flows and pillow lava (Nikolai Greenstone and Karmutsen Formation) capped with inner-platform carbonates (Chitistone Limestone, Whitestripe Marble, Kunga Formation, and Quatsino Limestone), overlie an upper Paleozoic andesitic arc sequence and Permian argillite and limestone. This coherent terrane, herein named Wrangellia, is juxtaposed against unlike sequences of Triassic and older rocks throughout its extent and is interpreted to be allochthonous. Paleomagnetic data obtained from the Nikolai Greenstone and published in a companion article by Hillhouse indicate that Middle and (or) Upper Triassic rocks in southern Alaska formed in low paleolatitudes, probably within 15° of the paleo-equator.A possible southeastern extension of Wrangellia occurs in the Hells Canyon region of eastern Oregon and western Idaho. This area contains the typical Triassic sequence of Wrangellia and has been interpreted by other geologists as allochthonous. Paleomagnetic data are lacking, however, to document its original latitude.
Paleomagnetism of the Triassic Nikolai Greenstone, McCarthy Quadrangle, Alaska
Authors: Hillhouse J. W.
Published: October 2008

Paleomagnetic evidence indicates that the extensive early Mesozoic basalt field near McCarthy, south-central Alaska, originated far south of its present position relative to North America. Results obtained from the Middle and (or) Upper Triassic Nikolai Greenstone suggest that those basalts originated within 15° of the paleoequator. This position is at least 27° (3000 km) south of the Upper Triassic latitude predicted for McCarthy on the basis of paleomagnetic data from continental North America. The Nikolai pole, as determined from 50 flows sampled at 5 sites, is at 2.2° N, 146.1° E (α95 = 4.8°). The polarity of the pole is ambiguous, because the corresponding magnetic direction has a low inclination and a westerly declination. Therefore, the Nikolai may have originated near 15° N latitude or, alternatively, as far south as 15° S latitude. In addition to being displaced northward, the Nikolai block has been rotated roughly 90° about the vertical axis. A measure of the reliability of this pole is provided by favorable results from the following tests: (1) Within one stratigraphic section, normal and reversed directions from consecutive flows are antipolar. (2) Consistent directions were obtained from sites 30 km apart. (3) Application of the fold test indicated the magnetization was acquired before the rocks were folded. (4) The magnetizations of several pilot specimens are thermally stable up to 550 °C. The stable component is probably carried by magnetite with lamellar texture, a primary feature commonly acquired by a basalt at high temperature during initial cooling of the magma. Geologic and paleomagnetic evidence indicates that the Nikolai is allochthonous to Alaska and that, together with associated formations in southern Alaska and British Columbia, it is part of a now disrupted equatorial terrane.
Identification and significance of late Holocene tephra from Otter Creek, southern British Columbia, and localities in west-central Alberta
Authors: Westgate J. A.
Published: October 2008

Three thin, light-coloured, ash-grade tephra beds occur within the uppermost metre of peat at Otter Creek bog in southern British Columbia. The youngest tephra is related to the ~2600 year old Bridge River tephra but is probably the product of a younger and weaker eruption that directed tephra to the southeast of the vent, believed to be located in the Meager Mountain district of southwestern British Columbia. The middle unit is ~2100 years old and is tentatively correlated with one of the upper beds of set P tephra of Mount St. Helens in Washington. The lowermost tephra is equivalent to the Yn bed of set Y, derived from an eruption of Mount St. Helens about 3400 years ago.The Yn tephra has been located as far north as Entwistle in west-central Alberta but mineralogically and chemically similar tephra elsewhere in this region is ~4300 years old and thus represents an older part of the Y set. Significant compositional differences between these two extensive members of the Y set have not yet been recognized.
Thick, layered peridotite–gabbro lava flows in Munro Township, Ontario
Authors: Arndt N. T.
Published: October 2008

Two unusually thick (120 m) lava flows in Munro Township, Ontario, are differentiated from peridotite at the base to gabbro near the top. One flow is komatiitic and contains the following units (from top to bottom): ultramafic flow-top breccia (19.5% MgO); olivine and pyroxene spinifex-textured rocks (17–10% MgO); gabbro (7% MgO); pyroxene cumulates (10–25% MgO); olivine cumulates (32–35% MgO); and a basal border zone. The composition of the lava at the time of eruption is believed to be represented by the ultramafic flow-top breccia. Following eruption, this lava differentiated to produce ultramafic cumulate rocks, and liquid of quartz-normative basaltic composition that solidified as gabbro.The other flow is tholeiitic and has a picritic hyaloclastite flow top (14% MgO) underlain successively by an aphanitic pyroxenite zone (but no spinifex texture), a gabbro zone, a thick clinopyroxene-rich cumulate unit, and a thin basal veneer of cumulate olivine.
Source parameters of the June 13, 1967 earthquake near Lake Ontario, New York State
Authors: Hashizume Michio , Tange Nagakoto
Published: October 2008

Source parameters of an earthquake with magnitude mb = 4.4 were determined by using surface waves. Small but clear surface wave signals were observed on long period records gathered from seismograph stations within an epicentral distance of about 2000 km. The focal mechanism was determined to be of strike-slip type with the maximum and the minimum compression axes trending NNW–SSE and ENE–WSW, respectively. The focal depth was determined to be near either 3 or 20 km.
A new Middle Ordovician sponge from western Newfoundland
Authors: Rigby J. Keith
Published: October 2008

Two specimens of the new sponge Epiplastospongia coactilis. n.gen., n.sp., have been collected from the Middle Ordovician Long Point Group of western Newfoundland. The massive sponge has a three dimensional skeletal net composed of ascending and of roughly horizontal, discontinuous, structural elements, all composed of laminated to concentrically layered, unsculptured, monaxial spicules overgrowing a core of monaxons. The Newfoundland sponge appears to be most closely related to Saccospongia from the Ordovician of Tennessee.
Hydrogen—a reducing agent in some uranium deposits
Authors: Levinson A. A.
Published: October 2008

Hydrogen, a strong reducing agent, may have been active in certain uranium deposits for which no other reducing agent has been found or may be inferred. The mechanisms that produce hydrogen in several geological environments are described. These include hydrogen generated near the surface by hydrogen-producing bacteria, at depth from magmatic sources, and from metamorphism of graphite-containing rocks.
An improved technique for the determination of rock porosity
Authors: Melnyk T. W. , Skeet A. M. M.
Published: October 2008

A modified technique for the determination of the connected porosity of rocks by the water immersion method has been developed and tested. The technique is recommended for rocks with porosity less than 0.05. The major modifications to the technique include saturation of the sample under vacuum conditions and determination of the water-saturated but surface-dry weight from a drying curve.Porosity measurements on 48 granitic samples showed that the technique is reproducible within a 95% confidence range of ±4% of the mean value. However, the possibility of spatial variation of porosity must be taken into account in assigning uncertainties to the measured values.
The timing of coalification in relation to structural events in the Grande Cache area, Alberta, Canada
Authors: Kalkreuth Wolfgang , Langenberg C. Willem
Published: October 2008

Lower Cretaceous coals from the inner Foothills of the Rocky Mountains were sampled for a study of the relationships between coal rank and folding and faulting. The coals were collected from laterally continuous seams in a highly folded and faulted area near Grande Cache, Alberta. Rank of the coals as determined by measuring mean maximum vitrinite reflectances ranges from medium- to low-volatile bituminous.The results indicate that the degree of coalification was established during burial from Albian to Late Paleocene times, before folding and faulting started. "Isoreflectance" lines run parallel to the bedding of the folded strata, and there are no significant changes in reflectances in the same seam from one thrust sheet to the other. However, in the footwall of the Mason Thrust, the mean maximum reflectances and bireflectances are locally increased above regional values.Regionally there appears to be a trend to slightly lower reflectances in the southeast of the study area. It is suggested that the lower reflectances are related to a somewhat lesser former depth of burial of the coals, probably of the order of 50 m.
Paleoclimatic implications of middle Wisconsinan pollen and a paleosol from the Purcell Trench, south central British Columbia
Authors: Alley Neville F. , Valentine Keith W. G. , Fulton Robert J.
Published: October 2008

A paleosol and organic-rich horizons occur in Bessette Sediments near Meadow Creek, south central British Columbia. The paleosol is at least 42 000 years old and formed on a paleoslope adjacent to some precursor to Meadow Creek. On higher parts of the paleoslope, the soil developed under locally dry conditions and influxes of eolian material; a regosol formed near the base of the paleoslope marginal to a floodplain. Pollen assemblages from the organic-rich horizons are grouped into two assemblage zones. MC 1, approximately 42 000 years old, is dominated by arboreal pollen, mainly Picea. MC 2 (approximately 34 000 years old) is dominated by Picea in conjunction with significant amounts of Tsuga heterophylla. Paleoclimatic implications of the assemblages are that temperatures 42 000 years ago were approximately 3 °C cooler than present but by 34 000 years ago had ameliorated and were similar to or slightly cooler than present.
Quantification of outlines in Frasnian (Upper Devonian) platform conodonts
Authors: Klapper Gilbert , Foster Jr. C. T.
Published: October 2008

The outline of the platform in Pa elements of conodont genera such as Palmatolepis is commonly one of the most heavily weighted taxonomic characters. But a taxonomy based only on visual discrimination of Pa elements of Frasnian species of Palmatolepis has resulted in widespread misidentification. Although their Pa elements can be confused, Palmatolepis subrecta, Palmatolepis hassi, and related species from the Frasnian of the Montagne Noire and Iowa can be separated consistently by use of features displayed by other elements of the apparatus, especially the Pb and M elements. To determine if significant differences exist among the Pa elements of these multielement species, digitized outlines of the Pa elements were analyzed using an orientation function similar to the tangent-angle function of F. L. Bookstein. A multielement classification based on the Pb and M elements was tested by a discriminant analysis of the outlines of the Pa elements. The results show that there is close agreement between the two procedures and that systematic differences exist among the Pa elements of groupings based on the Pb and M elements. Unquestionably, quantification of the outlines of platform conodonts will substantially improve taxonomic methods, with consequent enhancement of biostratigraphy.
Saffordophyllum and evidence for thrusting in the Cobbs Arm sequence, Newfoundland
Authors: Williams P. F. , Noble J. P. A.
Published: October 2008

A new occurrence of the tabulate coral Saffordophyllum is described from turbidites in the Cobbs Arm sequence of Notre Dame Bay. The age of the fossil is interpreted as Ashgillian, and its presence indicates repetition in the stratigraphic column. The repetition is explained by postulating a thrust, and this interpretation is supported by the presence of a pebbly mudstone that resembles olistostromes, associated with thrusting, elsewhere in the Cobbs Arm Zone.
Geochronological constraints on the timing of magmatism, deformation, and gold mineralization in the Red Lake greenstone belt, northwestern Ontario
Authors: Corfu F. , Andrews A. J.
Published: October 2008

The paper presents U–Pb ages on zircon, baddeleyite, titanite, rutile, and monazite from volcanic and plutonic rocks of the Red Lake greenstone belt in the northern Superior Province. The purpose of the study was to refine a previously outlined time frame for the volcanic evolution of the belt, define the time of major plutonism and deformation, and constrain the age of formation of gold deposits.Volcanism spanned at least 270 Ma between 3000 and 2730 Ma. New ages of 2989 ± 3 and 2894 ± 2 Ma for units of a lower volcanic sequence and [Formula: see text] and 2744 ± 1 Ma for units of an upper volcanic sequence corroborate and refine the previously established relationships. Local gabbroic and felsic intrusions cutting through the lower sequence yield ages of 2870 ± 15 and [Formula: see text], respectively.Volcanism was succeeded by major plutonism, deformation, alteration, and metamorphism between about 2730 and 2700 Ma. These processes were interrelated and progressed as a relatively continuous sequence of events accentuated by major activity during two phases at about 2720–2715 and 2705–2700 Ma. Early plutonism recorded at 2731 ± 3 Ma in the northern batholith complex was succeeded in the eastern part of the belt by a major tectonic – plutonic phase that includes intrusion of the McKenzie Stock at 2720 ± 2 Ma, the Dome Stock at 2718 ± 1 Ma, alteration and deformation of the Abino dyke at [Formula: see text], and emplacement of a late tectonic dyke at 2714 ± 4 Ma. A subsequent phase is recorded at 2701 ± 1.5 Ma in the Wilmar dyke. Major deformation and metamorphism in the western part of the belt is constrained by an age of 2729 ± 1.5 Ma for the deformed Red Crest Stock and a titanite age of 2705 ± 8 Ma for an undeformed crosscutting mafic dyke at Rowan Lake. Peak activity was probably coeval with emplacement of the adjacent batholithic phases at 2717 Ma. In the central part of the belt the deformation is constrained by ages of 2718 ± 1 Ma for the Dome Stock and 2699 ± 4 Ma for titanite of a crosscutting, undeformed diorite dyke and probably peaked during intrusion of the main phase of the Killala–Baird batholith at 2704 ± 1.5 Ma.Gold mineralization, which is spatially related to zones of intense shear deformation and alteration, is constrained within the time interval of 2720–2700 Ma by U–Pb ages on several felsic to mafic intrusive rocks that both pre- and post-date deformation and mineralization in different sections of the belt. These data indicate that mineralization occurred significantly later than the termination of volcanism.
Tectonic setting of the Tetagouche Group in northern New Brunswick: implications for plate tectonic models of the northern Appalachians
Authors: Staal C. R. van
Published: October 2008

A regional compilation and reinterpretation of geochemical analyses of mafic igneous rocks from the Ordovician Tetagouche Group in northern New Brunswick indicates the presence of at least three mafic assemblages: two groups of basalts and gabbros and one group of gabbros only. The three groups can be separated on the basis of TiO2 and trace-element content. Group A basalts generally have mid-ocean-ridge basalt (MORB)-like compositions, whereas group B basalts indicate a "within-plate" setting (WPB). Group C gabbros intrude into silicic volcanics that underlie the basalts but are rare or absent in the areas underlain by group A and B basalts. The group C gabbros probably represent the earliest stages of mafic igneous activity and have MORB-like compositions or represent a transition between MORB and arc basalts.The association of group A and B basalts with abundant marine sediments, such as thinly bedded turbidites and black and red shales, and the fact that they erupted locally on top of continental-crust-derived silicic volcanics suggest that they represent a marginal-sea or back-arc-basin environment rather than true oceanic (Iapetus) eruptives as has been suggested.The proposed back-arc environment and existing structural data are inconsistent with previously proposed tectonic models and large-scale correlations. Evidence for penetrative pre-Late Ordovician (Taconic orogeny sensu stricto) deformation is lacking in the northern part of the Miramichi Zone. Instead the earliest folding and related thrusting (D1) is ascribed to deformation associated with closure of the back-arc basin in post-middle Caradocian times.
Geology and geochemistry of Huronian rhyolites and low-Ti continental tholeiites from the Thessalon region, central Ontario
Authors: Jolly Wayne T.
Published: October 2008

Bimodal volcanism associated with early phases of Huronian rifting in central Ontario, dated about 2450 Ma, produced low-Ti tholeiitic basalts and two varieties of crustally derived calc-alkaline rhyolite. Early tholeiites are characteristically highly evolved, have Mg* values from 30 to 50, and display pronounced enrichment in large-ion lithophile elements (LILE) and light rare-earth element (LREE) in comparison with modern oceanic basalts, fractionated heavy rare-earth element (HREE) patterns, and low Ti, Zr, P, Nb, Ba, and K abundances. Ti/Zr ratios rise progressively in early basalts and associated basaltic andesite fractionates from about 35 in early flows to 55 in central units. Late basalts also carry enriched LILE and LREE, but, in contrast to early types, have average Mg* values greater than 50 and lower rare-earth element (REE) abundances with flat HREE patterns. They also display negative Ba, Nb, and P anomalies on chondrite-normalized distribution diagrams, but lack low K, Zr, and Ti contents. Their Ti/Zr ratios of about 80 approach chondritic levels. Melting models suggest the differences are explained by lower degrees of fusion (as low as 10%) in a hydrated, LILE- and LREE-enriched peridotite during generation of the early basalts, leaving a residue containing appreciable garnet, amphibole, Ti oxides, zircon, and apatite.Erupted simultaneously with the basalts were two distinctive rhyolite types: (1) a low-LILE, high-LREE group (25% of analysed specimens), derived by −20% melting of granulitic siliceous tonalitic gneiss, presumably at deep crustal levels, and (2) a high-LILE, low-LREE group (75%), derived, probably at shallower levels, by ≤ 30% melting in granitic rocks with pegmatitic or leucogranitic compositions. Mutual magma mixing of basalts and rhyolites during early stages of volcanism produced abundant hybrid andesites, but the frequency of contamination is much lower in later units.Hypothetical subcontinental source compositions, calculated from the Raleigh equation, suggest that the Huronian mantle had already undergone a complex history. Low Ba, Nb, P, Ti, and depleted HREE abundances compared with abundances for modern oceanic basalts suggest that a basaltic melt had already been withdrawn from this source during Archean time. Subsequently, an episode of hydrous metasomatism enriched the source in LILE and LREE. The latter event resulted from (1) subcontinental mantle metasomatism by previous Archean subduction, (2) mantle metasomatism during the terminal Archean Kenoran Orogeny, or (3) a wave of hydrous metasomatism accompanying Huronian mantle convection immediately preceding volcanism.
Influence of sediment source and type on the magnetic susceptibility of fiord and shelf deposits, Baffin Island and Baffin Bay, N.W.T.
Authors: Andrews John T. , Jennings Anne E.
Published: October 2008

Volume and mass magnetic susceptibility are measured on Recent and late Quaternary sediments from the fiords and shelf of eastern Baffin Island, Baffin Bay, and the northern Labrador Sea. Major changes in hinterland bedrock geology are associated with order of magnitude changes in magnetic susceptibility. The fiords that head into the Proterozoic Foxe Fold Belt have mass magnetic susceptibilities (MS) of ~ 2–4 × 10−7 m3/kg, compared with 25–60 × 10−7 m3/kg in sediments derived from Archean gneisses and granites. Another low-MS region is the middle reach of Frobisher Bay. MS studies in Cambridge, McBeth, and Itirbilung fiords included analyses of surface samples and samples from Lehigh (< 3 m) and piston (< 11 m) cores. Lehigh cores had higher MS values on average than the piston cores, suggesting a coarsening in texture or an increase in the flux of magnetic minerals during the last 0.3–3 ka. An analysis of the MS logs of 17 piston cores indicated that six broad patterns of MS can be recognized based on a combination of the MS trend with depth and the number of MS modes in the frequency distribution. Specific comparison of lithofacies logs and the MS signal indicates that variations in MS are frequently associated with changes in texture, but in some cases significant changes are independent of texture and represent major fluctuations in source materials.
Biogenic structures and micrite in stalactites from Grand Cayman Island, British West Indies
Authors: Jones Brian , Motyka A.
Published: October 2008

Stalactites from modern and old caves developed in the Bluff Formation of Grand Cayman Island contain laminae and bulbous masses of micrite intercalated with sparry calcite. The micrite, as well as some of the sparry calcite around it, contains small (up to 25 μm long) ovate to spherical bodies that have a high concentration of either manganese or iron. Such bodies may be of bacterial origin. The micrite contains numerous calcified filaments that are probably of algal origin. Calcification of the filaments occurred either during life or shortly after death of the algae. The algae played an important role in trapping and binding the micrite. Furthermore, the algae may be directly or indirectly responsible for the formation of much of the micrite.
A paleomagnetic study of the layered mafic intrusion at Sept-Îles, Quebec
Authors: Tanczyk E. I. , Lapointe P. , Morris W. A. , Schmidt P. W.
Published: October 2008

A paleomagnetic study of gabbroic and anorthositic members of the Sept-Îles layered mafic intrusion has isolated a remanence with direction D = 333°, I = −29 °(remanence A) and a corresponding pole of 141 °E, 20°N. The rocks are cut by numerous diabase dykes of unknown age. The remanence carried by the dykes has direction D = 188°, I = −85 °(remanence B), with a corresponding pole of 116°E, 59°S. Another remanence, statistically identical to B (D = 186°, I = −85°), is found at dyke contacts and in the local host rock; its associated pole, 115°E, 61°S, is identical to the one derived from the dykes. This overprint is significantly different from remanence A, and is obviously related to dyke emplacement. The location of the pole derived from remanence A is in excellent agreement with many other Cambrian poles from a variety of locations throughout cratonic North America. The rocks at Sept-Îles have been previously dated radiometrically at 540 Ma. Thus, all evidence indicates that remanence A is an original thermochemical remanent magnetization, acquired during initial cooling of the intrusion in the Cambrian and prior to the emplacement of the dykes.
Description and correlation of Late Ordovician conodonts from the D. ornatus and P. pacificus graptolite zones, Road River Group, northern Yukon Territory
Authors: McCracken Alexander D.
Published: October 2008

Upper Ordovician carbonate beds within clastic strata of the Road River Group, northern Yukon Territory, have yielded 403 conodont elements representing 25 species; 19 of these are illustrated. Genera present are Amorphognathus, Belodina, Besselodus, Drepanoistodus, Eocarniodus?, Gamachignathus, Icriodella, Noixodontus, Oulodus, Panderodus s.l., Paroistodus?, Plectodina, Protopanderodus, Pseudobelodina s.l., Scabbardella, Strachanognathus, and Walliserodus. The apparatus of new genus A new species A includes a symmetrical and bifurrowed rastrate element.Sparse conodont faunas from Rock River occur in strata below a level bearing graptolites of the D. ornatus Zone and between this zone and the succeeding P. pacificus Zone. These conodonts have a range of "Trentonian" –Gamachian (upper Caradoc –Hirnantian).The fauna from Blackstone River is from a single bed that is 3 m below the G. persculptus Zone? and 13.7 m above the P. pacificus Zone. Although stratigraphically closer to the former, this fauna may be equivalent to a level within the P. pacificus Zone; the conodonts suggest correlation with the late Richmondian Fauna 12 and the lower G. ensifer Zone of Anticosti Island, Quebec. A similar fauna (G. ensifer Zone) occurs in one horizon within the P. pacificus Zone at upper Peel River. One metre above this is the informal D. cf. D. mirus graptolite biohorizon (P. pacificus Zone).The Blackstone and Peel faunas equate to a level within the Ordovician Anceps bands C and D of the Ordovician–Silurian boundary stratotype at Dob's Linn, Scotland. The interval of Fauna 13 and the Gamachian Stage may correspond to Anceps Band E and the C.? extraordinarius Band (and contiguous strata) at Dob's Linn. The base of the G. ensifer Zone and the higher base of the Gamachian are probably late Rawtheyan.
Structure et microstructure de Favosites cylindrica Michelin 1847, espèce-type de Ohiopora n. gen. (Tabulata, Dévonien)
Authors: Lafuste Jean , Plusquellec Yves
Published: October 2008

The holotype of Favosites cylindrica Michelin 1847 is a fragment of corallum completely silicified and poorly preserved.Some specimens, regarded as topotypic (Falls of the Ohio), allow a detailed study of internal characters, wall, pores, and tabulae. Development of horizontal ridges results from folding of the wall. The abundance of these ridges is generally associated with the final stage of growth of the corallum. In ultra-thin sections with polished faces (LFP thin sections), parts of the skeleton not affected by silicification show the microstructural features of the wall. The median "dark line" is composed of granules, sometimes elongated; the stereozone is made of lamellae approximately parallel to the intramural coenozone.A biometric study of the so-called "topotypic" specimens and of the holotype of F. cylindrica shows the conspecificity of all this material.A new genus, Ohiopora, is proposed for F. cylindrica. The new genus is very close to Michelinia sensu stricto, from which it probably was derived but from which it may be distinguished by the presence of horizontal ridges, which form an original feature within the Tabulata.Several old species may be assigned to the new genus, and probably all are synonymous with O. cylindrica.Occurrence: Emsian?, lower and "middle" Eifelian. Ohiopora is endemic of eastern North American province.
Some new measurements of heat flow in the Superior Province of the Canadian Shield
Authors: Drury Malcolm , Taylor Alan
Published: October 2008

Borehole heat-flow measurements are reported from six new sites in the Superior Province of the Canadian Shield. Values adjusted for glaciation effects, but not for Holocene climatic variations, range from 42 to 56 mW/m2. When these new values are combined with 21 previously published borehole values the mean is 42 mW/m2 with a standard deviation of 11 mW/m2. The data for a site on the Lac du Bonnet batholith suggest that the batholith has a thin veneer, less than 3 km, of rock of high radiogenic heat production at the surface.
Geochemistry and isotope hydrogeology of the Mount Edziza – Mess Creek geothermal area
Authors: Clark Ian D. , Fritz Peter , Souther Jack G.
Published: October 2008

The Mount Edziza volcanic complex, a Recent volcano within British Columbia's northern Intermontane Belt, and the adjacent Mess Creek valley are investigated to evaluate the origin, geothermal history, and age of associated thermal waters. Samples of thermal and cold groundwaters, runoff, and glacier ice were collected for chemical and environmental isotope (18O/2H, 3H, [Formula: see text], [Formula: see text]) analysis.Mount Edziza thermal waters, discharging at 36 and 46 °C from extensive travertine formations at the base of the volcanic pile, originate as glacier meltwater on the summit of the complex. Their Na(Ca,Mg)–HCO3 chemistry is a product of alteration reactions with alkali basalts under a high CO2 partial pressure. Chemical and isotopic geothermometers suggest that subsurface temperatures are less than about 100 °C. Carbon-13 data show that the high carbon dioxide contents (close to 1 bar (100 kPa) pressure) likely originate through high-temperature decarbonation of marine carbonates at depth, and manifest a deep geothermal component in an essentially high-level geothermal flow system.Mess Creek thermal waters discharge at 43 °C from a fault-controlled flow system unrelated to the Mount Edziza complex, showing evidence of equilibrium with local basement rocks at temperatures less than about 100 °C. Deep circulation within a region of slightly higher than normal geothermal gradients is given as the mechanism for heating.The low 3H contents suggest that the thermal waters are tritium free (> 30 years old) and are mixing with between 10 and 40% nonthermal groundwater in the discharge areas.
Stratigraphy of the Ordovician of the Lac Saint-Jean and Chicoutimi outliers, Quebec
Authors: Desbiens Sylvain , Lespérance Pierre J.
Published: October 2008

Four previously defined formations within the Chicoutimi outlier are extended to the Lac Saint-Jean outlier; these formations are gradational into one another. The lowest of these formations, the Tremblay, is restricted to siliciclastic strata (predominantly coarse-grained sandstones); the overlying Simard, to micritic limestones. This last-named formation is succeeded by the highly fossiliferous Shipshaw Formation, composed of alternating limestones and shales, whereas the youngest of the previously named carbonates, the Galets Formation, is made up of echinodermal calcarenites. Graptolitic shales, herein assigned to the new Pointe-Bleue Shales, overlie in sharp contact the Galets; the youngest limestones of the area, previously assigned to the Richmondian, are different from the other Ordovician limestones. Trilobite faunas from the Shipshaw (and Galets) are correlated with the Edenian; the same correlation is probable for the uppermost of the four informal units recognized within the Simard Formation. The lowest three informal units of the Simard Formation are assigned to the Kirkfieldian; Shermanian strata have not been identified but are probably present. The Pointe-Bleue Shales were previously assigned to the Maysvillian. The Simard Formation contains an "Arctic" fauna, also present in the Manicouagan outlier but yielding in this last case a Shipshaw–Galets trilobite fauna. The Simard fauna, previously correlated with the "Black River," is thus interpreted as significantly time transgressive and of limited stratigraphic use. Depositional environments present in the Lac Saint-Jean and Chicoutimi outliers, but absent in southern Ontario during the Shermanian and Edenian, account for the necessity of significantly increasing the biozones of numerous taxa.
Silurian (Wenlock) brachiopods from the southern Mackenzie Mountains, Northwest Territories
Authors: Lenz Alfred C.
Published: October 2008

Twelve species of brachiopods of probable Wenlock age are described from a fauna of approximately 39 species from the upper part of the Whittaker Formation of the southern Mackenzie Mountains. The fauna is probably from the near-platform-edge benthic setting and is numerically dominated by smooth-shelled pentamerids.Species described are ?Dolerorthis sp. 1, Epitomyonia triseptata Lenz, Leangella sp., Rugolepyros latispondylus n.gen., n.sp. (a probable pentamerid), Reveroides sp., Harpidium (Lissocoelina) sp., Lissidium erugata n.gen., n.sp. (pentamerinid), Gracianella lissubmra Johnson, Boucot and Murphy, ?Reticulatrypa sp. 1, Whitfieldella cf. upsilon (Barrande), Atrypina (Atrypinopsis) cf. biconvexa Rong and Wang, and Glassia biloba n.sp. (lissatrypid).
Multielement species of Misikella Kozur and Mock, 1974 and Axiothea n.gen. (Conodonta) from the Mamonia Complex (Upper Triassic), Cyprus
Authors: Fåhræus Lars. E. , Ryley C. Christopher
Published: October 2008

The conodont genus Misikella Kozur and Mock, 1974 has previously been considered unimembrate and a possible junior synonym of Neospathodus Mosher, 1968. In the present study, Misikella is considered a valid genus with a tetramembrate conodont apparatus. Only one species, Misikella longidentata, is recognized as belonging in that genus. Other species previously brought to Misikella are considered as having had a bimembrate apparatus and are referred to Axiothea n.gen.
The Topsails igneous suite, western Newfoundland: an Early Silurian subduction-related magmatic suite?
Authors: Whalen Joseph B.
Published: October 2008

The Topsails igneous suite contains several Late Ordovician to Early Silurian volcanic and intrusive sequences, which overlie and intrude Early to Middle Ordovician oceanic and arc rocks. The oldest components of this suite may represent calc-alkaline, continental-arc magmatism. The younger components are bimodal, with felsic compositions vastly predominating, and include a major (> 2200 km2) alkaline (A-type) granite complex. These felsic components have similarities to peralkaline suites formed in unusual subduction-related settings. Younger mafic components resemble within-plate basalts emplaced in a continental setting.Silurian magmatic activity in the Canadian Appalachians is widespread, includes diverse magmatic types, and has contrasting metamorphic and tectonic overprinting, even in contiguous areas. These features and the probability of major post-Silurian displacements in the orogen render correlation and interpretation difficult. Tectonic models that consider basin closure and major plate movements to be complete by Middle Ordovician time fail to adequately explain the Silurian activity. Available data best fit a model that relates Late Ordovician to Silurian magmatic activity to the opening and closing of small, discontinuous basins, portions of which may have been floored by oceanic crust.