bluuebunny/crossref_metadata_2025 huggingface dataset:
Chitinozoaires du Silurien inférieur dans la région de la baie des Chaleurs en Gaspésie, Québec, Canada
Authors: Asselin E. , Achab A. , Bourque P. A.
Published: October 2008

A palynological study of a Llandoverian – lower Wenlockian sequence at Chaleurs Bay (Quebec) has revealed six distinct chitinozoan assemblages whose stratigraphic positions are well known on the basis of brachiopod and conodont data. A comparison of these microfaunas with those described from sequences of the same age in Europe and North America shows that the association Conochitina acuminata, Conochitina flamma, Conochitina cf. C. proboscifera, and Angochitina aff. A. longicollis is the most interesting one. This association is dated as late Llandoverian – early Wenlockian.
New petrological and geochemical data on mid-Paleozoic island-arc volcanics of northern Sierra Nevada, California: evidence for a continent-based island arc
Authors: Rouer O. , Lapierre H. , Coulon C. , Michard A.
Published: October 2008

The mid-Paleozoic volcanics of northern Sierra Nevada consist of the Sierra Buttes rhyolites, the Taylor basalts and andesites, and the Keddie Ridge basalt–latite–rhyolite suite. The Sierra Buttes calc-alkaline rhyolites display strong light rare-earth element enrichment and negative εNd values. The Taylor basalts and andesites in the northern Hough and Genesee blocks exhibit calc-alkaline affinities (REE rare-earth element patterns highly enriched in LREE), whereas in the southern Hough block they are tholeiitic (flat rare-earth element patterns). The abundance of silicic lavas, the low εNd values of both the Sierra Buttes and Taylor volcanics and the δ18O values of the Sierra Buttes rhyolite and Bowman Lake trondjhemite provide evidence that the northern Sierra Nevada island arc was continent based. The Keddie Ridge differentiated volcanics, characterized by high Zr, Y, Nb, K, and light rare-earth elements, are geochemically similar to a shoshonite suite. Their eruption at the end of the mid-Paleozoic volcanic episode suggests a reversal of subduction, uplift, and block faulting in the island arc.The mid-Paleozoic volcanics of the northern Sierra Nevada are thought to represent the remnant of a mature island arc because calc-alkaline rocks predominate over tholeiitic ones, the lavas display a K enrichment with time, and the volcanics are evolved in their isotopes, compared with rocks erupted in young or primitive island arcs.
Rb–Sr geochronology of the Archaean Maggo gneiss from the Hopedale block, Nain Province, Labrador
Authors: Finn Gregory C.
Published: October 2008

The Maggo gneiss, a typical grey gneiss from the Hopedale block of coastal Labrador (southern Nain Province), preserves structures of two major Archaean tectonothermal events, the Hopedalian and the younger Fiordian. Rb–Sr whole-rock analyses of four suites representing the Hopedalian event (3140 ± 95 Ma (1σ), 3125 ± 43 Ma, 3028 ± 199 Ma, and 3025 ± 163 Ma) fall within the early middle Archaean and represent a period of cratonization of the Hopedale block.Two suites with a younger Fiordian structural fabric (2899 ± 116 Ma and 2804 ± 100 Ma) fall within the late middle Archaean and are interpreted as dating a period of reworking that locally reset the Rb–Sr isotopic systematics of the Maggo gneiss. Fiordian ages were also determined from four suites (2927 ± 50 Ma, 2884 ± 86 Ma, 2854 ± 83 Ma, and 2764 ± 89 Ma) that do not display the Fiordian structural fabric, indicating that chemical and mechanical components of the Fiordian event did not occur simultaneously. Age determinations of the Fiordian do not date specific geologic events but seemingly reflect varying degrees of protracted isotopic homogenization during chemical and mineralogical reequilibration.One suite of analyses yields an age of 3305 ± 75 Ma and is interpreted as dating a pre-Hopedalian event. This older age supports field evidence as to the existence of old crust in the Hopedale block, typical also of rocks of the North Atlantic Craton.
Modelling of single-grain and floc settling
Authors: Lau Y. L.
Published: October 2008

An analytical model of time-dependent settling in a suspension of finite depth is presented. The model correctly predicts the decrease in total concentration of three suspensions of fine sediments undergoing single-grain settling. The changes in grain-size spectra, in which decrease in concentration occurs mainly in sizes larger than the modal size, are also predicted. The model is used with data from the settling of flocculated suspensions to show that the rate of flocculation is approximately proportional to the second power of the concentration.
Metallogenesis of the Abitibi greenstone belt of Canada: a contribution from the analysis of trace lead in sulfide minerals
Authors: Deloule Etienne , Gariépy Clément , Dupré Bernard
Published: October 2008

Pb-isotopic compositions are reported for 12 ore localities within the late Archean Abitibi greenstone belt. The studied samples carry massive or disseminated sulfides hosted in a variety of materials, including mafic–ultramafic igneous rocks, felsic lavas, porphyries, and sedimentary iron formations. Repeated leaching experiments on these sulfides frequently revealed the presence of a radiogenic Pb component, which is attributed to in situ decay of U and Th. The leaching experiments make it possible, in some cases, to separate the radiogenic Pb from the initial Pb included in the minerals. Six Pb–Pb isochrons formed by the analyses on leachates and residues show little evidence of secondary perturbations and yield ages that are, within error, similar to those determined for the supracrustal assemblage. This implies that the ores were concentrated synchronously with the main phases of magmatic activity, close to 2.7 Ga.The initial isotopic compositions of the sulfide specimens point to the existence of two different sources of metals: (i) juvenile, mantle-derived igneous rocks and (ii) older recycled supracrustal series. Ore formation frequently involves mixing of metals from these two sources in variable proportions. The initial isotopic composition of these two reservoirs is best evaluated by examining the composition of sulfides associated with komatiitic lava flows and with sedimentary iron formations, respectively.
Paleomagnetism of pre-Grenvillian mafic intrusions from the Grenville Province, southeast Labrador
Authors: Murthy G. , Gower C. F. , Tubrett M. , Pätzold R.
Published: October 2008

Paleomagnetic results are reported for Middle Proterozoic layered intrusions and dykes from within the Grenville Province of coastal southeastern Labrador. Rock units studied include the Little Grady Island layered norite intrusion, crosscutting mafic dykes from Little Grady Island, the dated Michael Gabbro from Double Island, and other miscellaneous mafic intrusions. On the basis of mineralogy and composition, it is concluded that the Little Grady Island layered mafic intrusion, the crosscutting dykes from Little Grady Island, and the miscellaneous mafic intrusions belong to the same period of magmatism (ca. 1650 Ma), in contrast with the Michael Gabbro, which belongs to a later event (ca. 1426 Ma).All rock units (except two dykes from the Hawke River Terrane) yield similar directions of magnetization. The remanence is extremely stable and has a characteristic direction of declination (D) = 321.7 °and inclination (I) = −49.3 °(N = 20, k = 24.1, α95 = 6.8°), with corresponding paleopole at 0.1°N, 155.1°E. This paleopole is interpreted as being representative of Grenvillian remagnetization. Based on an earlier age-calibrated Grenville track of the North American apparent polar wander path, this magnetization is correlated with a 900 Ma event, probably a (heating) pulse superposed on the general Grenvillian cooling. In contrast with this regional behaviour, two dykes from the Hawke River Terrane (Earl Island) yield a characteristic remanence of D = 285.7 °and I = 6.6°, with corresponding pole at 12°N, 158°W, interpreted as acquired during pre-Grenvillian, probably Elsonian, resetting.
Microearthquake survey of the Miramichi, New Brunswick, epicentral region, 1985
Authors: Burke Kenneth B. S. , Wetmiller Robert J. , Lamontagne Maurice , Carr M. Jeffrey , Hickey Craig
Published: October 2008

A survey of the continuing microearthquake activity in the 1982 Miramichi earthquake epicentral region of central New Brunswick took place between July 3 and August 19, 1985. MEQ-800 analog seismographs were deployed at six recording stations for the 47 day period of the survey. Three BakPak digital seismographs were added to the network on July 23, two at the same locations as analog units and one at a seventh site.Three hundred and twenty-five microearthquakes were recorded during the survey. The activity was episodic, with days of few earthquakes being followed by periods when events clustered together in miniswarms. Coda-magnitude relationships for five stations were established from regression analysis of scaled coda lengths of events on the MEQ 800 records and Nuttli magnitudes determined at an Eastern Canadian Telemetered Network station KLN. Only 21 of the events had coda magnitudes (Mc) greater than 0, the largest being 2.0. The larger magnitude earthquakes occurred in zones where there had been little preceding activity. The highest rate of activity was associated with the northeastern corner of the 1982 aftershock zone. Sporadic activity was also recorded from the western side of the zone.Composite P-nodal solutions for three subzones are consistent with the conjugate pattern of thrust faulting obtained in previous studies, except for rotation of fault-plane strikes from northerly to northwesterly directions for two of the subzones. It is remarkable that the pattern of activity first mapped by the 1982 aftershock surveys has remained relatively stationary over the subsequent 3½ year period.Un levé microséismique de l'activité courante dans la région épicentrale du tremblement de terre de Miramichi au Nouveau-Brunswick de janvier 1982 a été effectué entre le 3 juillet et le 19 août 1985. Des séismographes portatifs (MEQ 800) furent installés à six stations pendant une période de 47 jours. Trois séismographes numériques (BakPak) furent ajoutés au réseau le 23 juillet : deux sur sites de MEQ 800's et l'autre sur un septième emplacement.
The last glaciation of Marvin Peninsula, northern Ellesmere Island, High Arctic, Canada
Authors: Lemmen Donald S.
Published: October 2008

The limit of the last glaciation on Marvin Peninsula, northernmost Ellesmere Island, is recorded by extensive ice-marginal landforms and early Holocene glaciomarine sediments. While glaciers occupied most valleys on the peninsula, other areas remained ice free, as did most of the adjacent fiords. Beyond the ice limit, sparse erratics and degraded meltwater channels within weathered bedrock are evidence of older, more extensive glaciation(s). Shorelines and marine shells 50 m above the limit of the Holocene sea along the north coast relate to these older glacial events.Thirty-four new radiocarbon dates provide a chronology of ice buildup and retreat. Glaciers reached their limit after 23 ka, and locally as late as 11 ka. This was achieved by both expansion of existing glaciers and accumulation on plateau and lowland sites, which are presently ice free. Late Wisconsinan climate was characterized by cold and extreme aridity. Five dates ranging from 11 to 31 ka BP on subfossil bryophytes suggest that ice-free areas were biologically productive throughout the last glaciation. Ice retreat and postglacial emergence had begun by 9.5 ka and was associated with a marked climatic amelioration. The deglacial chronology confirms a pronounced disparity in the timing of ice retreat on the north and south sides of the Grant Land Mountains.
Temperature effects and their geological consequences at transform margins
Authors: Todd B. J. , Keen C. E.
Published: October 2008

A thermal model of transform-margin evolution, including both shear heating and lateral conduction of heat from hot oceanic to colder lithosphere, was developed to gain insight into transform-margin crustal structure. Results indicate that over 2 km of crustal uplift may occur at the fault trace for a modelled transform fault 500 km in length with spreading half-rates of 1.0 and 4.0 cm/year. This uplift decreases away from the fault over a distance of 60–80 km. The viscosity of the lower continental crust and upper mantle adjacent to the transform margin is reduced by a factor of more than 100. In response to plate motion and asthenospheric upwelling at the spreading ridge, flow of this thermally weakened material may also play a role in continental crustal thinning.Thermal model predictions are compared with geological observations and crustal structure across transform margins. In particular, we show that the geology of the Southwest Newfoundland Transform Margin, eastern Canada, and the Cape Range fracture zone, Western Australia, supports the model predictions of uplift, erosion, and crustal thinning.
The structure and geological development of the Erickson gold mine, Cassiar District, British Columbia, with implications for the origin of mother-lode-type gold deposits
Authors: Anderson P. G. , Hodgson C. Jay
Published: October 2008

The Erickson gold mine is a typical gold quartz vein deposit. The veins are hosted by a thrust-imbricated, gently dipping, synformal allochthon of low-grade metamorphic, Devonian to Upper Triassic basalts, argillites, and peridotites of oceancrustal origin belonging to the Sylvester Group, part of the Slide Mountain assemblage. The Sylvester allochthon lies concordantly on Devonian miogeoclinal sedimentary rocks of the North American continental margin and was emplaced in the Middle Jurassic as a result of the collision of the Quesnel arc with North America. The veins in the mine are hosted mainly by a moderately dipping system of shear zones with approximately orthorhombic symmetry, indicating a triaxial bulk, inhomogeneous strain pattern superimposed on the earlier formed, gently dipping thrusts. Steeply dipping extension veinlets, rotation of schistosity, and downdip slickenlines indicate the maximum shortening axis was subvertical. The veins display complex superimposed ribbon and breccia textures, indicating incremental growth. Most of the gold occurs in association with tetrahedrite, sphalerite, and chalcopyrite in steeply dipping, late, grey quartz veinlets localized within and striking perpendicular to the main veins. The vein-forming event, dated at 130 Ma, appears to have been related to extension and high heat flow associated with the rise of the Omenica geanticline, in turn the result of crustal thickening caused by the collision of the amalgamated Quesnel arc – North America plate with Stikinia in the Middle Jurassic.
Internal structure of the Cadillac tectonic zone southeast of Val d'Or, Abitibi greenstone belt, Quebec
Authors: Robert François
Published: October 2008

The Kirkland Lake – Larder Lake – Cadillac Break is a major fault zone of the Abitibi greenstone belt, well known for its spatially associated gold camps. A detailed structural analysis of this fault zone in the Val d'Or area has shown the presence of a 200 – 750 m wide zone of high strain, defined here as the Cadillac tectonic zone (CTZ), which includes the narrower schist zone generally regarded as the Cadillac Break. The boundaries of the CTZ, which coincide with major lithologic contacts, strike approximately east–west and dip 80° to the north.The internal structure of the CTZ is best analysed in terms of two increments of the same progressive deformation. The D1 strain increment is characterized by an east–west-striking, subvertical S1 foliation, at low angle in strike to the bound aries of the CTZ and containing subvertical elongation lineation. Primary lithological contacts have been transposed into S1 and folded by F1a folds. F1b intrafolial folds of S1 ranging from noncylindrical, subhorizontal folds to subvertical sheath folds, indicate dip-slip movements within the CTZ. The D1 strain increment records synchronous dextral transcurrent shearing, as required by the obliquity of S1 to the CTZ boundaries, and subvertical elongation, as indicated by elongation lineations and F1b folds. The D2 strain increment is chiefly characterized by the development of moderately to steeply plunging asymmetric Z-shaped F2 folds with associated S2 cleavage, recording dextral transcurrent shearing.The studied segment of the CTZ is best interpreted as a zone of dextral transpression, evolving from a zone with a significant shortening component (D1) into a zone increasingly dominated by a transcurrent shearing component (D2).
Shear-wave splitting and anisotropy in the Charlevoix seismic zone, Quebec, in 1985
Authors: Buchbinder Goetz G. R.
Published: October 2008

During the month of October 1985 a second experiment was undertaken in the Charlevoix seismic zone to further test the hypothesis that shear-wave splitting could be observed in a seismically active region. The first experiment had been undertaken in 1984 and yielded only a very limited amount of data. Seismograms recorded by digital three-component seismographs located very close to the epicentres of seven earthquakes showed shear-wave splitting over 15 different paths. The amount of [Formula: see text] wave variation varied from about 24 to 160 ms or from 0.4 to 8.7% of the [Formula: see text] wave velocity. The largest value occurred over the shortest path of about 7 km, for which essentially the whole path may be anisotropic, leading to a crack density (ε) of less than 0.09. For the rest of the data, all with less than 3% shear-wave-velocity variation, ε varies from 0.005 to 0.03, if whole-path anisotropy is assumed. These values of ε are not significantly different from those obtained in 1984. The average azimuth of the initial shear-wave polarization is 37°, also similar to that observed in 1984. All the data in the zone can be explained by the presence of saturated vertical cracks striking 37 °east of north.
Petrochemical and stratigraphic aspects of North Mountain basalt from the north shore of the Bay of Fundy, Nova Scotia, Canada
Authors: Greenough John D. , Jones Lois M. , Mossman David J.
Published: October 2008

Early Jurassic quartz-normative tholeiitic basalts occur in a series of fault blocks at four localities (Cap d'Or, Parrsboro, Five Islands, and Bass River) along the north shore of the Bay of Fundy. Major-element and trace-element data show that they represent outliers of the North Mountain basalt (NMB), which from the south shore of the Bay of Fundy are well-known. Diagnostic 87Sr/86Sr ratios (≈0.70609) indicate that a thick (>90 m) flow at Five Islands and Cap d'Or represents the lower unit of NMB, thus extending this single flow's lateral extent to 230 km. Thin flows overlying the thick flow at Cap d'Or suggest that the middle unit of NMB also occurs on the north shore. A thick flow at McKay Head (Parrsboro area) shows a variable Sr isotopic composition that is probably a result of metasomatism (with Rb addition) along the Cobequid fault. The average composition (0.70656) is similar to that of the upper unit of NMB. If the flow does represent the upper unit, then four thinner flows above it form an "overlying unit" not recognized along North Mountain. Although the nature of contacts between the middle and upper units was not observed, a lack of sedimentary rocks between all other flow units indicates that little or no sedimentation occurred between basalt eruptions. North shore basalts appear less mafic (more evolved) than south shore basalts, providing support for the hypothesis of differentiation during northeasterly magma migration through dykes that fed 230 km long fissure eruptions.
Early Silurian orogenic andesites from the central Quebec Appalachians
Authors: David Jean , Gariépy Clément
Published: October 2008

The Pointe aux Trembles Formation is a deep- to shallow-water volcaniclastic apron with massive lava flows deposited in Early Silurian time. The apron deposits extend laterally to a deep-water accumulation of finer grained siliciclastic and tuffaceous material intruded by gabbroic sills, defined as the Lac Raymond Formation. The suite has most of the characteristics of high-K orogenic andesites. The lavas are highly porphyritic, with plagioclase and augite as major phenocrysts, subordinate orthopyroxene (chlorite pseudomorph), and rare hastingsitic hornblende. They form a continuous series that is intermediate in composition, hypersthene normative, and high in Al2O3 (> 16%), low in TiO2 (< 1.5%), and without iron enrichment. The Lac Raymond gabbroic sills have geochemical features closely related to those of the lavas, suggesting their cogenetic origin. With magmatic differentiation, the suite becomes depleted in most major and trace elements, indicating crystal fractionation of plagioclase, pyroxene, amphibole, apatite, and oxides. Negative Nb and Ta anomalies and clinopyroxene geochemistry confirm that the magmatism occurred in a volcanic-arc environment. It can then be inferred that plate convergence and subduction were still active in Early Silurian time. The petrographic features of the suite also led to the conclusion that a thin rather than a mature continental crust was involved in the genesis of the volcanism. The earliest portion of the Taconian–Acadian interlude was thus an orogenic period in continuation with the early tectonic activity of the Taconian. Consequently, tectonic reconstruction of that part of the Appalachian orogen should not be viewed in terms of isolated events.
Billings' second operculum: a late Early Ordovician Maclurites (Gastropoda) from western Newfoundland and the Canadian Arctic
Authors: Yochelson Ellis L.
Published: October 2008

An operculum of Maclurites, first described by Billings in 1865, is redescribed from the original material collected at Cape Norman, northwestern Newfoundland, and from additional specimens from Ellesmere Island, Canadian Arctic. Based on indirect evidence, a very late to latest Early Ordovician age is assigned to the strata of the St. George Group that contains this fossil. This operculum has a paleoequatorial distribution. On the basis of its geometry, the operculum is interpreted as having a "concentric" growth pattern rather than a spiral one. If so, the complex coiling pattern assumed for Maclurites may be in error. Speculation on functional morphology explains the shape of the operculum without recourse to any assumed coiling during growth and reinforces the interpretation of Maclurites as an exceedingly sedentary animal.
The occurrence of pop-ups in the Québec City area
Authors: Wallach Joe , Chagnon Jean-Yves
Published: October 2008

Pop-ups, which form in response to high horizontal surface and near-surface stresses, were recognized on the floors of two quarries in metropolitan Québec City. This note constitutes the first published documentation of pop-ups in the Québec City area.The orientation of most of the pop-ups is consistent with the stress system affecting eastern North America; however, pop-ups with other orientations have also been recognized. The origin of the latter may reflect local stress conditions.
Stratigraphy and tectonic setting of the upper part of the Cadwallader terrane, southwestern British Columbia
Authors: Umhoefer Paul J.
Published: October 2008

The Upper Triassic to Middle Jurassic Cadwallader terrane lies on the northeastern edge of the Coast Plutonic Complex in southwestern British Columbia. Previous work on the Cadwallader Group, the basal unit of the terrane, suggested it was an Upper Triassic (Carnian to middle Norian) volcanic arc and related clastic rocks. Volcanism ceased in early Norian time. A detailed study of the upper part of the Cadwallader terrane (Tyaughton Group and overlying Last Creek formation) shows that it is a sedimentary sequence deposited on the fringe of the inactive Cadwallader magmatic arc. The Upper Triassic (middle to upper Norian) Tyaughton Group consists of nonmarine to shallow-marine clastic rocks and limestones that show sudden changes in depositional setting. The Lower to Middle Jurassic Last Creek formation, a transgressive sequence of clastic rocks, disconformably overlies the Tyaughton Group. The clastic rocks in the two units were derived from a mixed volcanic and plutonic source region that also included a minor metamorphic component and local lower Norian limestones. The stratigraphy of the upper part of the Cadwallader terrane records long-term thermal subsidence of the basin caused by cooling of the magmatic arc after volcanism ceased in the early Norian. The detailed stratigraphy of the upper Cadwallader terrane supports correlation of the Cadwallader with the Stikine terrane, along which it is currently structurally juxtaposed.
The Stampede tephra: a middle Pleistocene marker bed in glacial and eolian deposits of central Alaska
Authors: Begét James E. , Keskinen Mary
Published: October 2008

A deformed block of silt incorporated in a push moraine of the Lignite Creek drift of the Nenana River valley in central Alaska contains the 10 cm thick Stampede tephra. The silt block and tephra are folded, sheared, and cut by multiple fault planes and appear to have been entrained by a glacier and deformed by glaciotectonic processes while frozen. The Stampede tephra is also found in a paleosol preserved within a sequence of eolian sediments near the Tanana River some 175 km to the northeast, allowing direct tephrochronologic correlations between the depositional record of Quaternary glaciations in the Alaska Range and eolian sediments in unglaciated central Alaska. The Lignite Creek drift predates deposits of the late Wisconsin Riley Creek and penultimate Healy glaciations but postdates the Stampede tephra, indicating that it dates to the middle Quaternary, and is not part of the Tertiary Nenana Gravel Formation.
Thermal maturation of organic matter in the Middle Devonian to Tertiary section, Fort Norman area (central Mackenzie Plain)
Authors: Feinstein S. , Williams G. K. , Snowdon L. R. , Goodarzi F. , Gentzis T.
Published: October 2008

The Fort Norman area is marked by a complex structural and depositional history with temporally and spatially variable temperature and maturity gradients. Maturity of the Middle Devonian Canol – Hare Indian unit indicates two terrains of markedly different paleotemperatures and thermal gradients, roughly coinciding with the Palaeozoic Keele Arch (north) and Root Basin (south), with a sharp transition (lateral discontinuity) between them. Maturity of the unconformably overlying Cretaceous to early tertiary section is lower and laterally continuous across the entire study area, showing no relation to the sub-Cretaceous structures. The vertical maturity profile in the southern terrain is unique in that two discontinuous segments record markedly different thermal histories, neither of which is related to present burial conditions. Maturity of the Devonian formations was established some time prior to the sub-Cretaceous erosion, whereas that in the Cretaceous to Tertiary section postdates Palaeocene but predates a major part of the later Tertiary deformation and erosion. In contrast, the continuous maturity profile recorded in the northern terrain reflects a significant effect of the Tertiary thermal conditions, indicating much lower thermal gradients in the Keele Arch than in the Root Basin during the early phase of maturation. Along with the structural pattern and sedimentary history, the striking differences indicated in the thermal gradients between the Root Basin and the Keele Arch suggest a strike-slip-related pull-apart or another stretching mechanism for the Root Basin in contrast to the compression in the Keele Arch. In addition to the characterization of the regional thermal history and its variation with time, the maturity pattern obtained allows some estimate to be made of the thickness of the eroded section and timing of the major erosional phases.
Maturation thermique de la matière organique dans un bassin du Paléozoïque inférieur, basses-terres du Saint-Laurent, Québec, Canada
Authors: Héroux Y. , Bertrand R.
Published: October 2008

The organic matter (OM) sampled in 15 oil exploration wells and 102 outcrops of Cambrian-Ordovician rocks in the St. Lawrence Lowlands consists of zooclasts (chitinozoans, graptolites, and scolecodonts) and solid bitumen (mainly pyrobitumen). The reflectance of pyrobitumen, transformed in vitrinite-equivalent (Ro-Std-B), indicates that the upper part of the platform sequence is mature (condensate zone) in the Québec area, but overmature in the Montréal area.The platform is divided into three domains based on optical texture of OM and types of bitumen: domain 1, south of Montréal, contains a highly reflecting and coked pyrobitumen showing alteration rims; domain 3, east of Trois-Rivières, contains low-reflecting, late solid bitumen commonly associated with oil impregnations; domain 2, located midway, contains a pyrobitumen with moderate reflectance and, locally, fine mosaic texture. The thermal maturation in the autochthonous sequences of the St. Lawrence Lowlands and in the Appalachian allochthons increases from the north-east toward the south-west and in the direction of the Appalachian belt. In wells, the gradient of Ro-Std-B with depth decrease from the autochthonous zone toward the Appalachian belt, and is inversely related with thickness of the sequences. Isoreflectance values parallel the outline of the Chambly–Fortierville Syncline in the central and eastern parts of the basin. Consequently, thermal maturation predates folding. Reflectance jumps observed between the Lowlands and the first Appalachian overthrusts, and observed when crossing Logan's Line, demonstrate that the maximum burial of Appalachian sequences predates the tectonic transport. The Ro-Std-B in allochthonous zones shows higher values in the St-Francis River cross-section than in structural equivalent units of the Québec area. Therefore the increase of thermal maturation observed from the northeast toward the southwest, in the St. Lawrence Lowlands, is also developed in the Appalachian allochthonous units. A post-Taconic regional thermal event explains this similarity in both autochthonous and allochthonous sequences, with the sequences of the Connecticut Valley – Gaspé Synclinorium being the most thermally mature.Zones of highest thermal maturation, locally observed in the Montréal area, are explained by (i) hydrothermal activity (Ro-Std = 3–4%), accounted for by sulfate and sulfide mineralization (Ba, Zn, Pb) and by (ii) contact metamorphism, related to alkaline intrusions (Ro-Std-B = 13%). The contact metamorphism is restricted to aureoles less than 5 km wide around the Monteregian alkaline intrusions, but the hydrothermal alteration, apparently not related to contact metamorphism, covers an area of 10 km around mineralized domains.
Geochemistry of the Île Cadieux monticellite alnöite, Quebec, Canada
Authors: Harnois Luc , Mineau Raymond
Published: October 2008

The Île Cadieux alnöite, a small Cretaceous intrusion, is a member of the Monteregian Hills Petrographic Province. Mineral chemistry was determined for olivine, spinel, clinopyroxene, melilite, and a potassium–iron–nickel sulphide akin to djerfisherite. Whole rocks were analysed for major elements and 24 trace elements (including rare-earth elements). The Île Cadieux alnöitic rocks have greater MgO/Al2O3 ratios than most alnöites but are otherwise similar to typical alnöites with respect to major and trace elements. Comparison of spinel and whole-rock chemical compositions from the Île Cadieux and Île Bizard (located 15 km to the northeast) alnöitic intrusions suggests that these magmas were generated under different physicochemical conditions of melting, or alternatively that they are fractions of a single magma which crystallized under different conditions.
Persistent mafic igneous activity in an A-type granite pluton, Cobequid Highlands, Nova Scotia
Authors: Pe-Piper G. , Piper D. J. W. , Clerk S. B.
Published: October 2008

The West Moose River pluton is one of a series of latest Devonian – Early Carboniferous plutons of granite and gabbro–diorite in the Cobequid Highlands (southern edge of Avalon zone). Intrusion of minor gabbro preceded emplacement of the granite, which is fractured and cut by later mafic dykes, of which some predate and others postdate a Namurian compressive deformation. Minor hybrid phases reflect mixing of mafic and felsic magmas, which are also represented by basalt and rhyolite in the synchronous Fountain Lake Group. The mafic rocks are continental tholeiites reflecting regional Early Carboniferous extension. Later dykes are more fractionated, with high P2O5, TiO2, and other high-field-strength elements. The dykes are pervasively altered, probably by residual fluids from the granite hydrothermally circulated by the hot mafic rocks. Higher Ga/Al, Hf, and Zn content in basalts than dykes suggests upward increase in halogen complexing in the mafic plumbing system. Late-stage fluids concentrated K, Rb, and Cs in the dykes but not the lavas. Alteration in granite includes mafic partings (biotite and Fe–Ti oxides) along fractures, particularly near dykes, and local albitization. Such alteration hinders determination of granite protolith from geochemistry, but mineral composition and the regional enrichment of the granite in Nb, Y, and Ga/Al is similar to that in A-type granites. Alteration associated with the mafic dykes continued for tens of millions of years after pluton emplacement.
The nature of sialic basement to the Dunnage Zone, northern Newfoundland: evidence from crustal xenoliths
Authors: Owen J. Victor , Greenough John D. , Fryer Brian J.
Published: October 2008

Quartzofeldspathic xenoliths representing the probable structural basement to the northern Dunnage Zone occur in lamprophyre dykes on Alcock Island and vicinity, Notre Dame Bay. The dykes occur close to the boundary between seismically defined lower crustal blocks (LCB) below the Dunnage Zone, so the assignment of the xenoliths to a specific subsurface source is equivocal. The xenoliths include (i) clinopyroxene-bearing meta-(quartz) diorite to tonalite; (ii) plagioclase + quartz-rich rocks; and (iii) garnetiferous gneiss, including granulite. Paragneiss is absent, so the gneissic xenoliths do not appear to be direct analogues of Gander Zone metasediments thought to underlie parts of the Dunnage Zone farther to the southeast. The xenoliths also differ from Grenvillian crust exposed in western Newfoundland: the granulites are mineralogically distinct (contain clinopyroxene + garnet rather than orthopyroxene + garnet) and yield higher metamorphic P (approx. 8–10 kbar versus approx. 3–7 kbar) (1 kbar = 100 MPa), and the granitoid xenoliths are dioritic–tonalitic rather than granitic. Consequently, we propose that the xenoliths are derived from a non-Gander, non-Grenville source that may include Central LCB and (or) exotic basement material. We cannot, however, exclude the possibility that the xenoliths represent deeper structural levels of Grenvillian or Gander Zone crust than are presently exposed in outcrop.
Deep seismic reflection data from the Bay of Fundy and Gulf of Maine: tectonic implications for the northern Appalachians
Authors: Keen C. E. , Kay W. A. , Keppie D. , Marillier F. , Pe-Piper G. , Waldron J. W. F.
Published: October 2008

Three deep-penetration seismic reflection profiles were collected off southwest Nova Scotia to determine the crustal structure and geometry beneath the Avalon and Meguma zones of the Appalachian Orogen in Canada. Onshore geological features have been traced seawards using new gravity and magnetic anomaly maps. The seismic data can also be correlated with the previous United States Geological Survey profile in the central Gulf of Maine.Two seismically distinct lower crustal blocks are identified: the Avalon and Sable lower crustal blocks, separated by a major north-dipping reflection zone that cuts the entire crust. The recognition of the Sable block adds a fourth block to the three already identified in the Canadian Appalachians. The Sable block is overlain by the Meguma Zone. The Avalon Zone overlies at least the northern part of the Avalon lower crustal block. Although offshore extension of geological features is not unequivocal, it appears that a north-dipping reflection zone southwest of Nova Scotia marks the site of Devonian thrusting of Avalon Zone over Meguma Zone. In the Bay of Fundy to the north, two south-dipping reflection zones are interpreted as major thrusts, possibly placing Avalon lower crust over a unit with different tectonic affinities. The Fundy Fault is a Carboniferous thrust within the Avalon block along the coast of New Brunswick; this was reactivated during Mesozoic extension as a transtensional fault. Extensional displacement farther southwest was probably accommodated along east-west-trending faults and small rift basins associated with them.
A deep seismic reflection profile across the Nova Scotia continental margin, offshore eastern Canada
Authors: Keen C. E. , MacLean B. C. , Kay W. A.
Published: October 2008

Results from two deep seismic reflection lines are presented. When combined, these lines span the rifted continental margin off Nova Scotia, from crust unaltered by rifting to the ocean basin. These data provide crustal and upper mantle reflection geometry to depths of over 50 km and elucidate the rifting process on this margin which occurred during the Mesozoic breakup of Pangaea. The continental crust below the continental shelf and slope becomes progressively thinner toward the ocean–continent boundary. In the upper crust, normal faults accommodated Mesozoic extension, and these flatten and terminate at 5–6 s (two-way time). In the lower crust and upper mantle Mesozoic rifting may be reflected in dipping events, which are interpreted to be normal faults. All Mesozoic extensional faulting could be controlled by the preexisting fabric of the crust, which in this region would be related to Appalachian compression within the Meguma Terrane. Below the continental rise, there is some evidence for magmatic underplating of the thinned continental crust, but the presence of synrift diapiric salt prevents clear definition of deeper structure. The extreme seaward end of the profile lies in a region interpreted in most other, earlier studies to be oceanic in nature. However, the seismic profile described here shows that relief on basement is associated with listric normal faults, which flatten in decollement, and that linear, landward-dipping intrabasement reflections characterize the area. These features can be explained in either a continental or an oceanic context.
SEMICLASSICAL GRAVITATIONAL EFFECTS AROUND GLOBAL MONOPOLE IN BRANS–DICKE THEORY
Authors: RAHAMAN F. , GHOSH P.
Published: October 2008

Recently, W. A. Hiscock4studied the semi classical gravitational effects around global monopole. He obtained the vacuum expectation value of the stress–energy tensor of an arbitrary collection of conformal mass less free quantum fields (scalar, spinor and vectors) in the spacetime of a global monopole. With this stress–energy tensor, we study the semiclassical gravitational effects of a global monopole in the context of Brans–Dicke theory of gravity.
ON THE CLASSICAL CONFINEMENT OF TEST PARTICLES TO A THIN 3-BRANE IN THE ABSENCE OF NON-GRAVITATIONAL FORCES
Authors: LA CAMERA M.
Published: October 2008

The classical confinement condition of test particles to a brane universe in the absence of non-gravitational forces is transformed using the Hamilton–Jacobi formalism. The transformed condition provides a direct criterion for selecting in a cosmological scenario 5D bulk manifolds wherein it is possible to obtain confinement of trajectories to 4D hypersurfaces purely due to classical gravitational effects.
COLLIDING NEUTRINO BEAMS
Authors: SCHWIENHORST REINHARD
Published: October 2008

From several neutrino oscillation experiments, we understand now that neutrinos have mass. However, we really do not know what mechanism is responsible for producing this neutrino mass. Current or planned neutrino experiments utilize neutrino beams and long-baseline detectors to explore flavor mixing but do not address the question of the origin of neutrino mass. In order to begin answering that question, neutrino interactions need to be explored at much higher energies. This paper outlines a program to explore neutrinos and their interactions with various particles through a series of experiments involving colliding neutrino beams.
THE NEUTRINO SELF-ENERGY IN A MAGNETIZED MEDIUM
Authors: GARCÍA ALBERTO BRAVO , BHATTACHARYA KAUSHIK , SAHU SARIRA
Published: October 2008

In this work we calculate the neutrino self-energy in the presence of a magnetized medium. The magnetized medium consists of electrons, positrons, neutrinos and a uniform classical magnetic field. The calculation is done assuming that the background magnetic field is weak compared to the W-boson mass squared, as a consequence of which only linear order corrections in the field are included in the W-boson propagator. The electron propagator consists of all order corrections in the background field. Although the neutrino self-energy in a magnetized medium in various limiting cases has been calculated previously, in this paper we produce the most general expression of the self-energy in the absence of the Landau quantization of the charged gauge fields. We calculate the effect of the Landau quantization of the charged leptons on the neutrino self-energy in the general case. Our calculation is specifically suited for situations where the background plasma may be CP symmetric.
PREDICTION OF ANTISENSE OLIGONUCLEOTIDE EFFICACY USING AGGREGATE MOTIFS
Authors: SIPES TAMARA B. , FREIER SUSAN M.
Published: October 2008

Antisense oligonucleotide technology allows the targeted reduction of mRNA expression through the in vitro application of short (~20 nt) DNA molecules. Oligonucleotides are valuable both in the study of gene regulation and for having potential therapeutic effects. In theory, a base sequence complementary to a region of the transcript would hybridize to its mRNA target. Nevertheless, in practice some complementary antisense oligonucleotides are more active and more potent than others in suppressing specific gene expression. We present a novel computational approach to modeling oligonucleotide efficacy that uses aggregate motifs, which are flexible tetramotifs that expand the predictive ability of the data descriptors and the attribute space. We also demonstrate our findings on the largest dataset yet reported in the literature. It was shown that the prediction accuracy was significantly enhanced, offering more than eightfold improvement compared to the traditional methods.
FINDING ALTERNATIVE SPLICING PATTERNS WITH STRONG SUPPORT FROM EXPRESSED SEQUENCES ON INDIVIDUAL EXONS/INTRONS
Authors: WONG THOMAS K. F. , LAM TAK-WAH , YANG WANLING , YIU S. M.
Published: October 2008

We consider the problem of predicting alternative splicing patterns from a set of expressed sequences (cDNAs and ESTs). Some of these expressed sequences may be errorous, thus forming incorrect exons/introns. These incorrect exons/introns may cause a lot of false positives. For example, we examined a popular alternative splicing database, ECgene, which predicts alternate splicing patterns from expressed sequences. The result shows that about 81.3%–81.6% (sensitivity) of known patterns are found, but the specificity can be as low as 5.9%. Based on the idea that errorous sequences are usually not consistent with other sequences, in this paper we provide an alternative approach for finding alternative splicing patterns which ensures that individual exons/introns of the reported patterns have enough support from the expressed sequences. On the same dataset, our approach can achieve a much higher specificity and a slight increase in sensitivity (38.9% and 84.9%, respectively). Our approach also gives better results compared with popular alternative splicing databases (ASD, ECgene, SpliceNest) and the software ClusterMerge.
SPATIAL ASSIMILATION AND SELF-EMPLOYMENT: THE CASE OF BLACK AMERICANS
Authors: FAIRCHILD GREGORY B.
Published: October 2008

Residential segregation has played a central role in theories of minority entrepreneurship. This study integrates two theories in the extant literature on minorities and urban areas (spatial assimilation theory and labor market disadvantage theory); and tests a hypothesis on the self-employment likelihood of black Americans. Descriptive statistics indicate a negative relationship between black-white segregation and increasing socioeconomic status (SES), although blacks remain considerably residentially segregated from whites of similar SES. The model results indicate that, after controlling for a number of factors, segregation of high SES blacks and whites in a metropolitan area is associated with higher likelihood of black self-employment.
ROLE DEMANDS, DIFFICULTY IN MANAGING WORK-FAMILY CONFLICT, AND MINORITY ENTREPRENEURS
Authors: SHELTON LOIS M. , DANES SHARON M. , EISENMAN MICKI
Published: October 2008

By exploring difficulty in managing work-family conflict for minority entrepreneurs, this study considers work-family issues for business persons who have received little attention in the literature, yet form new businesses at rates exceeding the national average. We employ a role theory perspective to examine two major research questions using a nationally representative sample of African-American, Mexican-American, Korean-American, and White business owners. Specifically, we ask: do minority business owners experience greater difficulty in managing conflicts between work and family roles when compared to White entrepreneurs? And does difficulty in managing work-family conflict negatively impact business performance? Empirical results show that Korean-American and Mexican-American entrepreneurs have greater role demands, and subsequently, higher levels of difficulty in managing work-family conflict than African-Americans and Whites. Furthermore, difficulty in managing work-family conflict negatively impacts business performance whether performance is measured through the perception of the business owner, or through more objective financial measures. We contribute to the literature on minority entrepreneurs as well as expand the work-family conflict literature by shifting the focus from employed individuals to entrepreneurs, and by emphasizing the effect of such conflict on performance rather than well-being.
INFLUENCE OF FAMILY'S SOCIAL RELATIONSHIPS ON THE DEBT STRUCTURE OF MEXICAN-AMERICAN AND KOREAN-AMERICAN SMALL BUSINESSES
Authors: HAYNES GEORGE W. , ONOCHIE JOSEPH I. , LEE YOON
Published: October 2008

This study utilizes the Korean-American and Mexican-American samples in the National Minority Business Survey to examine the debt structure of small businesses owned by individuals from these ethnic groups. Small business owners with higher household net worth were more likely to borrow from finance companies, friends, and credit card companies. When controlling for business, business owner and family characteristics, Mexican-American small business owners with high net worth were significantly more likely to borrow from commercial banks than Mexican-American small business owners with low net worth are. Korean-American small business owners with high net worth were significantly more likely to utilize family loans than Korean-American small business owners with low net worth are. Korean-American small businesses appeared to be more financially dependent on the financial strength of their community, while Mexican-American small businesses owners appeared to be more financially independent.
THETA CONSTANT IDENTITIES AT PERIODS OF COVERINGS OF DEGREE 3
Authors: KOPELIOVICH YAACOV
Published: October 2008

We derive relations between theta functions evaluated at period matrices of cyclic covers of order 3 ramified above 3k points.
BOUNDS FOR THE GENUS OF NUMERICAL SEMIGROUPS
Authors: LEHER ELI
Published: October 2008

We introduce a method to find upper and lower bounds for the genus of numerical semigroups. Using it we prove some old and new bounds for it and for the Frobenius number of the semigroup.