bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature profiles in the Barnes Ice Cap, Baffin Island, Canada, and heat flux from the subglacial terrane
Authors: Hooke Roger LeB. , Alexander Jr. E. Calvin , Gustafson Robert J.
Published: April 2011

Temperature measurements were made in seven boreholes, ranging in depth from 50–276 m, in the Barnes Ice Cap. Holes B4, D4, and T0975 are approximately 1 km from the margin and an average of 8 km apart. Holes T091, T081, T061, and T020 lie along a 10.2 km flow line passing through T0975. Temperature profiles are convex upward in all holes except T020, reflecting the combined effects of longitudinal and upward vertical advection, and frictional heating. The profile in T020 is concave near the bottom of the hole, as a result of downward vertical advection, but convex above mid-depth, owing to a 2.5 °C cooling of the near-surface ice in the early 1940's.Modeling, using a finite difference scheme, suggests that the profiles are in equilibrium with slightly lower vertical velocities and longitudinal advection rates than exist at present, and that temperatures at the glacier surface have increased 0.1–0.5 °C over the last few decades. The modeling further suggests that the heat flux from the subglacial terrane beneath most holes is 0.5–0.8 heat-flow units (HFU), which is somewhat lower than the average geothermal flux on the Canadian Shield. The heat flux seems to decrease down-glacier along the flow line through T0975, apparently reflecting climatic warming of about 2 °at the end of the Little Ice Age. In contrast, the heat flux appears to increase southeastward from the flow line, reaching an anomalously high value of about 1.9 HFU at B4. This trend is unexplained.Measurements of U, Th, and K in rock samples collected near the margin suggest heat production rates of about 5 heat-generation units (HGU), which is slightly higher than previous measurements on Baffin Island.
Pleistocene peccary, Platygonus compressus Le Conte, from Yukon Territory, Canada
Authors: Beebe B. F.
Published: April 2011

A fragmented radius of a late Pleistocene peccary, Platygonus compressus Le Conte, has been recovered near Old Crow, Yukon Territory, Canada. The known northern limit of the species is thus extended approximately 3000 km, from the northeastern United States to north of the Arctic Circle in Pleistocene Beringia, and confirms the cold tolerance of the species. The small size of the specimen supports a theory that small size in P. compressus is correlated with periglacial environment. Although the age of the specimen is uncertain, a mid-Wisconsin age is inferred on the basis of availability of a route of dispersal to Beringia and palaeoecological evidence which suggest a largely treeless tundra dominated by sedges and grasses, but with a rich herb component.
Picopsis pattersoni, n.gen. and sp., an unusual therian from the Upper Cretaceous of Alberta, and the classification of primitive tribosphenic mammals
Authors: Fox Richard C.
Published: April 2011

A new therian mammal of primitive tribosphenic grade is described from the Upper Milk River Formation (Upper Cretaceous) of Alberta, Canada, and its relationships to other primitive tribosphenic therians are discussed. The new therian and its presumed nearest relatives form the basis of a new family within the Order Aegialodontia. A revised classification of the Infraclass Tribotheria is presented.
Experiments on the significance of flocculation in the settling of fine-grained sediment in still water
Authors: Kranck Kate
Published: April 2011

The changes in grain size and concentration with time were studied in relatively dilute settling suspensions of varying initial concentration and constituent grain size and composition. During single grain settling in distilled water and dispersant solution, i.e., in the absence of flocculation, a narrow range of sizes at a time were lost from suspension at a rate dependent on the initial size distribution. In salt water the importance of single grain settling relative to floe settling decreased with increase in concentration. The decrease in total concentration with time due to floe settling was proportional to the minus four-thirds power of the time. The overall sorting of the sediment had some effect on the flocculation rate but the effect of grain mineralogy appeared to be minor. Comparison between the size distributions of the settled sediment and textures of recent clastic sediments and experimental turbidites indicates that the relative effectiveness of single grain and floe settling largely determines the sorting of most fine-grained as well as many sandy sediments.
Sediment dynamics in the macrotidal Avon River estuary, Bay of Fundy, Nova Scotia
Authors: Lambiase Joseph J.
Published: April 2011

The Avon River estuary in central Nova Scotia is part of the northeastern arm of the Bay of Fundy. The estuary is macrotidal; tidal range is 15.6 m at lunar perigee. The large tidal range generates strong currents. Maximum current speeds increase from 0.6 m/s at the estuary mouth (seaward end) to 1.7 m/s at the estuary head (shoreward end). Every location in the system is either flood or ebb current dominant.There are six major intertidal sand bodies in the estuary. Three of these form an ebb tidal delta at the estuary mouth that resembles many mesotidal ebb tidal deltas. One of the sand bodies at the estuary head also is part of an ebb tidal delta, another is a flood tidal delta, and the third is a tidal point bar.Ripples, megaripples, and sand waves are the three major classes of bedforms. Flow regime increases in the onshore direction, and bed configuration reflects maximum flow conditions.Mean grain size decreases from the estuary mouth to the head, producing an inverse relationship between mean grain size and current velocity. Cumulative frequency curve analysis indicates that the inverse relationship is produced by hydraulic sorting, which excludes the coarsest grain population from the estuary head.
Stratigraphy, sedimentology, and regional correlation of the Horsethief Creek Group (Hadrynian, Late Precambrian) in the northern Purcell and Selkirk Mountains, British Columbia
Authors: Poulton T. P. , Simony P. S.
Published: April 2011

The Hadrynian Horsethief Creek Group in the northernmost Purcell Mountains and adjacent Selkirk Mountains is subdivisible regionally into grit, slate, carbonate, and upper clastic divisions in upward succession. The grit division represents a submarine fan assemblage and the slate division hemipelagic muds probably deposited in intermediate depths. The carbonate division comprises an interval of discontinuous lenses representing "bahamian" carbonate bank and off-bank assemblages, and the upper clastic division is a heterogeneous clastic wedge, which shows some evidence of northerly and westerly increasing depositional depths. Feldspathic quartz pebble conglomerate beds intercalated with the carbonates in both bank and off-bank facies indicate tectonic activation of granitic source areas like those from which similar rocks in the upper part of the Miette Group of the Rocky Mountains were derived.The upper part of the slate division, which can be differentiated in western localities as a distinct semipelite–amphibolite unit, and the upper clastic division each expand in thickness northwestward to dominate the Horsethief Creek outcrops in the Selkirk Mountains. These thickness variations, the increase of amphibolite northward in the semipelite–amphibolite unit, and the loss of grit beds northward in the slate division suggest deposition in a depocentre that received coarse sediment from southerly and easterly directions, and that became the site of mafic igneous activity.
Geochemical discriminators and the palaeotectonic environment of the North Mountain basalts, Nova Scotia
Authors: Wark J. M. , Clarke D. B.
Published: April 2011

The late Triassic – early Jurassic North Mountain basalts of Nova Scotia have been analyzed for various elements believed to be useful in determining the palaeotectonic environment of eruption. The discriminant diagrams show these basalts to have within-plate affinities, with a possible indication of oceanic chemical characteristics. An oceanic environment, however, is at variance with the field relations, which show the within-plate environment to be continental; thus the oceanic chemical characteristics may suggest eruption through a continental crust that was thinning prior to the onset of active sea-floor spreading later in the Jurassic.
Results of a seismic reflection survey across the fault zone between the Thompson nickel belt and the Churchill Tectonic Province, northern Manitoba
Authors: Green A. G.
Published: April 2011

Approximately 11 km of four-fold common reflection point data have been recorded across a region that spans the contact fault zone between the Thompson nickel belt and the Churchill Tectonic Province. From these data it is shown that the upper crust in this region and, to a lesser extent, the lower crust are characterized by numerous scattered events that originate from relatively small-scale features. Within the Thompson nickel belt two extensive and particularly high-amplitude reflection zones, at two-way travel times of t = 5.0–5.5 s and t = 6.0–6.5 s, are recorded with apparent northwesterly dips of 0–20 °C. These reflection zones, which have a laminated character, are truncated close to the faulted contact with the Churchill Province. Both the contact fault zone and the Churchill Province in this region have crustal sections that are relatively devoid of significant reflectors. The evidence presented here confirms that the crustal section of the Thompson nickel belt is fundamentally different from that of the Churchill Tectonic Province.
Sedimentation in proglacial Sunwapta Lake, Alberta
Authors: Gilbert Robert , Shaw John
Published: April 2011

The hydrologic and limnologic conditions of Sunwapta Lake, a small proglacial lake in the Canadian Rocky Mountains, were investigated with special reference to the sedimentology of this lake. Discharge and suspended sediment concentrations of the inflowing streams were measured to give estimates of sediment input. Distribution of large loads of fine glacial sediment is largely by an inflow- and wind-controlled circulation, which commonly fluctuates diurnally. The spatial distribution of sedimentation was determined by use of sediment-collecting pans placed on the lake bed. Turbidity currents are rare with only one event monitored in 2 years. This event was caused by a burst of highly sediment-charged inflow water. The rarity of turbidity currents is attributed to the high sediment concentration in the lake water, which results from the small size of the lake in relation to the inflow. Wind-generated water movement at the lake floor ranges from 0.0–0.03 m/s while the maximum recorded velocity of the turbidity currents was 0.32 m/s.Sedimentation rates are calculated and six cores from the lake bed, each containing sediment deposited over several years, are described. Although bedding and lamination are found in all cores, correlation between cores was not possible. Sedimentary characteristics are related to inflow and lake conditions: laminated and massive beds of medium to fine sand and silt are related to turbidity events, graded laminae in coarse and fine silt to diurnal variations in lake currents, and massive beds in silt to periods of continuous sedimentation without diurnal variation. Deformed beds result from subaqueous slumps.
Geochronology of Wabigoon belt granitoids, northwestern Ontario: Rb/Sr isochrons for seven late-tectonic plutons
Authors: Birk Dieter , McNutt Robert H.
Published: April 2011

Whole-rock Rb/Sr isochrons are presented for seven late-tectonic granitoid plutons intruded into supracrustal rocks of the Wabigoon volcanic–plutonic belt. Age estimates range from 2461 ± 78 Ma (Ottertail Lake stock) to 2645 ± 158 Ma (Bears Passage stock). A mean age estimate by weighted pooling of the isochrons gives 2555 ± 41 Ma, while pooling 39 samples into one regression gives 2568 ± 35 Ma. These ages concur with estimates for the duration of the Kenoran orogeny.Error limits on our isochrons incorporate the duration of polydiapirism, aplitic dyking, and deuteric metasomatism. Available ages indicate that syntectonic and late-tectonic granitoid plutonism spanned a geologically short time interval (centered at 2565 ± 62 Ma) that cannot be differentiated by the Rb/Sr technique. Consistently low initial Sr ratios of 0.7008 ± 0.0006 indicate a mantle or low Rb/Sr source.
A Lower Jurassic heteroporid bryozoan and associated biota, Turnagain Lake, British Columbia
Authors: Henderson C. M. , Perry D. G.
Published: April 2011

Late Early Jurassic heteroporid bryozoa occur in arenaceous carbonates near Turnagain Lake, north-central British Columbia. The occurrence of Heteropora tipperi n. sp. marks the first documentation of Early Jurassic cyclostome bryozoa in North America. The associated fauna, comprising the ammonite Harpoceras, the foraminifer Reinholdella, and the pelecypod Weyla, establish the age as Early Toarcian. Other associated biota include an endolithic green alga(e), which is demonstrated to have a commensal relationship with H. tipperi n. sp. Sedimentologic and biotic data from the host strata point to a shallow, temperate, high-energy, normal marine environment.
Stratigraphy and sedimentology of the Late Proterozoic Rock Harbour Group, Flat Islands, Placentia Bay, Newfoundland Avalon Zone
Authors: Hiscott Richard N.
Published: April 2011

The Late Proterozoic Rock Harbour Group, as exposed on the Flat Islands, Placentia Bay, consists of a 700 m thick fining-upward sequence of deep-water conglomerates, pebbly sandstones, and thinly-bedded siltstones, capped by a chaotic olistostrome. This sequence rests unconformably on sediments and pillowed tholeiitic basalts of the Burin Group, which were deformed, eroded, and then exposed on the sea floor before Rock Harbour deposition. The conglomerates, sandstones, and siltstones of the Rock Harbour Group may have been deposited within a deep slope canyon cut into the Burin Group, or in a perched slope basin at the margin of the rift system, which was initiated immediately before extrusion of the oceanic tholeiites that characterize the Burin Group. Remarkably good analogues for these two depositional settings can be found in the modern Gulf of California.Although the precise age of the Rock Harbour Group is uncertain, it may be a deep-water equivalent of mixtites found within the Conception Group in the eastern Avalon Zone. However, lithologically similar deep-water sandstones and conglomerates spanning the entire period of development of the Burin Rift Zone may be present in the vicinity of Placentia Bay. If so, then it is reasonable to expect a considerable range in the ages of these units from place to place.
Application de l'analyse factorielle des correspondances aux gaz adsorbés de l'off-shore du Labrador
Authors: Bertrand R. , Desjardins M. , Kübler B.
Published: April 2011

A zoneography of early maturation stages of organic matter, based on adsorbed gases (GA) interpretation, is confirmed by correspondence analyses (AFC) in seven offshore wells of Eastcan et al. of Labrador. Three major maturation stages are recognized: an immature biogenic methane stage (BIO), a superior (upper) methane stage (MES), and a superior (upper) condensate gas stage (CS). An immature (IM) and relatively sterile interval is intercalated between the BIO and the MES zones. The introduction of lithological variables in the correspondence analysis does not greatly influence the results for the well studies.
Conglomérats polygéniques ophiolitiques: anciens éboulis de talus de fond océanique?
Authors: Hébert Réjean
Published: April 2011

Field observations on the polygenetic conglomerates associated with the ophiolitic complexes in the Eastern Townships are comparable to those on the common slope facies in the present-day ocean bottom. Sedimentary processes (submarine erosion, deposition) are probably responsible for the internal structures of the conglomerates. This working hypothesis replaces the explosion-origin interpretation previously proposed. [Journal Translation]
The geochemistry of gold-bearing chemical sediments, Dickenson Mine, Red Lake, Ontario: a reconnaissance study
Authors: Kerrich R. , Fryer B. J. , Milner K. J. , Peirce M. G.
Published: April 2011

Auriferous sedimentary rocks at the Dickenson Mine, Red Lake, are characterized by large enrichments of rare elements (Au, Ag, Pd, As, Sb, B) and metals conventionally considered to be relatively immobile (Ni, W), with negligible concentrations of the abundant and mobile base metals. Based on a reconnaissance survey involving 12 rocks analysed for 42 elements, these sediments can be represented in terms of a mixture of two components―mafic volcaniclastic material and hydrothermal precipitates. The volcaniclastic component has a composition closely comparable to mafic volcanic rocks that conformably envelope the sediments, and contributes all of the Al, Ti, V, Sc, Zr, and F. The hydrothermal component donates Si, Fe, Mn, Mg, Ca, K, Si, and C, together with Au, Ag, Pd, As, Sb, B, W, and Ni. Chromium and nickel are contributed from both sources. Alteration of the mafic volcanic rocks that envelope the auriferous sediments involved fixation of Si, K, and CO2, in contrast to the typical patterns of metasomatism in footwall rocks to base metal massive sulphide deposits, which are characterized by Mg, Fe (Si, S) addition.Quartz isolated from chert within the auriferous sediments and volcanic rocks has a maximum δ18O of 19‰, which is within the range of δ values for marine cherts of ~2.8 Ga, and signifies precipitation in equilibrium with ambient marine water of ~−1‰ at ~70–90 °C. Mafic volcanic wall rocks to the sediments have whole-rock δ18O values of 16–17‰ and Δquartz–chlorite ≤ 2‰. The anomalously heavy whole-rock isotopic composition and small quartz–chlorite fractionation may result from the growth of chlorite from precursors such as zeolites and smectite. Alternatively, chlorite or its precursors may have become enriched in 18O by isotope exchange with metamorphic hydrothermal fluids that become ponded when discharge to the hydrosphere was capped by overlying basalts.Rare earth element (REE) distributions in sediments and mafic volcanic wall rocks are characterized by relatively flat normalized patterns up to Sm–Gd, followed by an abrupt continuous decline in abundance. This implies modification of the primary tholeiitic abundances by hydrothermal solutions capable of mobilizing heavy REE's relative to light REE's. The environment that would satisfy the geological observations and chemical data is one of metamorphic hydrothermal fluids emmanating onto the sea floor during a period of relatively quiescent mafic submarine volcanism, with subsequent capping of the discharge during emplacement of the overlying pillow basalts.
Revised stratigraphy of the Long Reach area, southern New Brunswick: evidence for major, northwestward-directed Acadian thrusting
Authors: McCutcheon S. R.
Published: April 2011

In the Long Reach area of southern New Brunswick, a new stratigraphic succession has been delineated; it consists of Precambrian (?) volcanic rocks, Cambrian sedimentary, volcanic and hypabyssal rocks, Silurian sedimentary rocks, and Devonian plus Precambrian (?) heterogeneous, granitoid rocks. The northern boundary of this succession is postulated to be a northwestward-directed thrust fault of Acadian age. Other Acadian thrust faults are interpreted in the area and major reverse movement of the same age occurred along the Belleisle Fault.Mafic and felsic volcanic rocks that were previously thought to be either Precambrian or Silurian are demonstrably part of the Lower Cambrian section. Some of the granitoid rocks intrude Silurian strata and therefore cannot be basement to the Cambrian succession. Other granitoid rocks appear to be older and may be Precambrian in age.
La séismicité provoquée au réservoir LG-2
Authors: Buchbinder G. G. R. , Anglin F. M. , McNicoll Roger
Published: April 2011

The construction of a rock and earth-filled dam in the La Grande River valley, Quebec has created a hydroelectric reservoir with a maximum depth of 145 m and a volume of 61.7 × 109 m3. No seismicity in this Precambrian Shield region above magnitude 0.1 was observed in the reservoir zone in the 27 months preceding the filling. Microearthquakes of magnitude less than 1 started under the reservoir when a water depth of 90 m was reached after 30 days and this activity continued for about 3 months. A second series of microearthquakes began in the same active zone when the rate of filling increased twofold. The seismically active area is confined to a zone 4 km × 7 km and no deeper than 5 km. The microearthquakes are considered to be the result of minor reactivation of old faults under the reservoir in response to the increased pore pressure.
Thermophysical characterization of oil sands: 3. Electrical properties
Authors: Das M. , Thapar R. , Rajeshwar K. , DuBow J.
Published: April 2011

The electrical behavior of oil sand samples from the Athabasca, N. W. Asphalt Ridge, P. R. Spring, and Circle Cliffs deposits was studied in the frequency range 50 Hz – 103 MHz at ambient temperature and up to 550 °C. Anomalously high dielectric constants (ε′) were measured for these samples at low frequencies (<1 kHz) and at elevated temperatures (>200 °C). Accumulation of mobile charges at the phase boundaries in the oil sand matrix was probably responsible for this effect. These mobile charges were presumably created by thermal fragmentation of oil sand bitumen. The anomalous increase in the low-frequency (50 Hz – 1 MHz) ε′ values at temperatures above 150 °C was also traced to interfacial polarization effects. Dipole relaxation behavior was observed for the various samples at frequencies below ~1 kHz and in the temperature range 150–470 °C. Two distinct relaxation processes were identified. The low-temperature (150–400 °C) process had activation energies for dipole orientation ranging from 4.0 to 9.0 kJ/mol depending on the oil sand specimen. The second relaxation process, which occurred at temperatures above 400 °C, had significantly higher activation energies (30–34 kJ/mol). The occurrence of these dipole relaxation peaks may be relevant in the use of electrical techniques to map the location of pyrolysis zones in in situ oil sand retorts. Measurements on the Athabasca samples in the high-frequency range (1–103 MHz) revealed distinct changes in the dielectric parameters associated with the loss of water from the oil sand matrix. The electrical behavior of oil sands is represented in terms of an equivalent circuit model comprising discrete RC elements corresponding to various components in the oil sand matrix. Such a representation was found to aid in an assignment of the observed changes in the electrical properties with frequency and temperature to distinct physical or chemical processes occurring in the oil sand matrix.
Experimental formation and significance of etch patterns on detrital garnets
Authors: Gravenor C. P. , Leavitt R. K.
Published: April 2011

The patterns found on the surfaces of etched detrilal garnets are formed by facets that resemble a series of elongated overlapping sharp-edged rectangular or rhombohedral building blocks, mammilla, or rounded hummocks that are gradational to facets and rhombohedral or triangular pits.Opinion on the origin of these surface features is split between those who have suggested that they are due to etching and those who believe they are due to overgrowth. In order to resolve this controversy, crushed garnets were subjected to three sets of experiments. The first involved leaching the crushed garnets in various strengths of acid (HF) and alkaline (NaOH) solutions. The second involved thin-sectioning of naturally etched garnets to determine if a nucleus could be seen under a petrographic microscope and the third involved electron microprobe and SEM X-ray analyses across cut sections of naturally facetted garnets to determine compositional variations through individual grains and between grains from a single sample.The results of the first set of experiments showed that etching starts immediately in all concentrations of HF and that within the first 24 h, facets, mammilla, and pits are visible on the surface of the grains removed from a 40% solution of HF. The second and third sets of experiments showed that, first, the garnets are chemically homogeneous from the inside to the outside of the grains and, second, that there is a wide variation in the chemical composition of the edges of garnets from a single sample.The chemical homogeneity of the garnets demonstrates that the surface patterns did not develop from growth over a pre-existing nucleus. This observation, and the variation in chemical composition of the edges of garnets within a single sample, indicate that the surface patterns on the detrital garnets are the result of etching by intrastratal solutions.
Queen Charlotte fault zone: microearthquakes from a temporary array of land stations and ocean bottom seismographs
Authors: Hyndman R. D. , Ellis R. M.
Published: April 2011

A temporary array of land and ocean bottom seismograph stations was used to accurately locate microearthquakes on the Queen Charlotte fault zone, which occurs along the continental margin of western Canada. The continental slope has two steep linear sections separated by a 25 km wide irregular terrace at a depth of 2 km. Eleven events were located with magnitudes from 0.5 to 2.0, 10 of them beneath the landward one of the two steep slopes, some 5 km off the coast of the southern Queen Charlotte Islands. No events were located beneath the seaward and deeper steep slope. The depths of seven of these events were constrained by the data to between 9 and 21 km with most near 20 km. The earthquake and other geophysical data are consistent with a near vertical fault zone having mainly strike-slip motion. A model including a small component of underthrusting in addition to strike-slip faulting is suggested to account for the some 15° difference between the relative motion of the North America and Pacific plates from plate tectonic models and the strike of the margin. One event was located about 50 km inland of the main active zone and probably occurred on the Sandspit fault. The rate of seismicity on the Queen Charlotte fault zone during the period of the survey was similar to that predicted by the recurrence relation for the region from the long-term earthquake record.
A new model for the acquisition of thermoremanence by multidomain magnetite
Authors: Sugiura Naoji
Published: April 2011

Isothermal remanence (IRM) induced in multidomain grains at a high temperature (T*) decreases on cooling in zero field. The intensity and stability (against temperature change) of the IRM depend on whether the temperature T* was reached from a higher temperature or from a lower temperature. These results cannot be explained by the existing multidomain theories. A new model of TRM (thermoremanence) acquisition mechanism in which domain wall interactions play the major role is proposed. This model explains the main features of the experimental results very well and predicts an almost linear relationship between TRM and the inducing field, up to relatively high fields.
Faulting and fracturing in part of the Duluth complex, northeastern Minnesota
Authors: Foose Michael P. , Cooper R. W.
Published: April 2011

Extensive faulting and fracturing have been documented by detailed field studies of a 48 km2 area in the upper Precambrian Duluth complex, northeastern Minnesota. Faults and fractures dip steeply, trend principally N35°E, N05°W, and N40°W, and were recognized by the displacement of plagioclase and plagioclase–olivine cumulate layers within the so-called South Kawishiwi intrusion. This work represents the first field documentation of extensive faulting in the Duluth complex and shows that fault offsets are an important complicating factor in understanding the geology of the complex. Further, faults of the type mapped are compatible with the structures predicted but not previously recognized by models that genetically link the Duluth complex to a major period of crustal rifting, and these faults have important economic implications, as offsets along them are certain to affect the continuity of important copper–nickel sulfides that occur along the basal part of the Duluth complex.
Correlation of Lower Silurian strata from the Michigan Upper Peninsula to Manitoulin Island
Authors: Johnson Markes E.
Published: April 2011

The same approach in using sea-level curves to refine time-rock correlations between widely separated regions also has an important application in resolving the tangle of dual stratigraphic nomenclature that often develops in neighboring regions divided by political boundaries. A good example is the Lower Silurian of the Michigan Upper Peninsula and Manitoulin Island, Ontario. Four peaks in sea-level fluctuation are recorded in both areas by coeval pentamerid communities stratigraphically intermixed with coral–algal and ostracode–vermiform communities indicative of shallower water conditions. Despite many similarities between the rock units containing these fossil communities, most are identified by different formation names on opposite sides of the U.S.–Canadian border. This study details the eastward thinning of strata across the boundary area. The Cordell dolomite of Michigan is extended to Manitoulin Island, but not the underlying Schoolcraft dolomite, due to the pinching out of beds that define its upper and lower contacts. The Fossil Hill Formation of Manitoulin Island is accordingly reduced but retained even though it contains some of the other subformational units represented in the Schoolcraft. Facies relationships between the Michigan Hendricks dolomite and its correlative Mindemoya and St. Edmund Formations argue for their valid maintenance. The relationship between the Byron and Wingfield Formations is less clear. Probably the Dyer Bay Formation should be extended to Michigan in place of the Lime Island dolomite.
The Pokiok batholith: a contaminated Acadian intrusion with an anomalous Rb/Sr age
Authors: McCutcheon S. , Lutes G. , Gauthier G. , Brooks C.
Published: April 2011

Samples of the stratigraphically placed (< 400 Ma) Pokiok batholith of New Brunswick give a Rb/Sr total-rock age of 431 ± 9 Ma. This age is some 40 Ma older than the estimated age of crystallization and is interpreted to result from the mixing of variable amounts of crustal strontium with mantle-like Sr at or about 390 Ma. The existence of inherited or crustal isochrons in the Pokiok batholith implies that all uncorroborated total-rock Rb/Sr ages for granitic plutons in the Appalachians of eastern Canada should be carefully appraised in view of their importance in estimating the timing and duration of the Acadian Orogeny.
A parallochthonous group of sedimentary rocks unconformable overlying the Bay of Islands ophiolite complex, North Arm Mountain, Newfoundland
Authors: Casey John F. , Kidd W. S. F.
Published: April 2011

This paper reports and documents the existence on the North Arm Mountain massif of a parallochthonous group of sedimentary rocks that overlie the Bay of Islands ophiolite complex with marked angular unconformity. Some of these rocks are those previously regarded as oceanic sediments lying conformably on top of the igneous rocks of the ophiolite complex, and some were mapped as part of the igneous rocks themselves. The name Crabb Brook Group is proposed for this sedimentary sequence and three new formation names are also put forward. Massive sedimentary breccias directly overlie and contain clasts from all units of the ophiolite complex. Evidence of intense predepositional weathering of the clasts and the underlying bedrock is common. Bedded shales and their disrupted equivalents in olistostromes containing sedimentary and igneous blocks overlie the breccias. Two fossil localities within the shales yield acritarchs of Llanvirnian age and inarticulate brachiopods probably not older than this. A small remnant of coarse red arenite caps the section. The sequence appears to overlie some thrust faults and to be cut by others. It is tightly folded on a large scale along with the thrusts and the ophiolite complex. We interpret the whole folded stack, including some underlying allochthonous sediments, to be truncated by gently inclined thrusts formed in the later stages of allochthon emplacement. The lithologies, facies, structural and tectonic relationships, and fossil age of this sedimentary group indicate that it is parallochthonous in the context of the regional geology. It was deposited on the Bay of Islands ophiolite complex during its obduction and cannot therefore be used to infer the tectonic environment of the spreading ridge and transform fault that formed the Bay of Islands complex.
A geomagnetic depth sounding profile across the northern Yukon and the Mackenzie Delta region, Canada
Authors: DeLaurier Jon M. , Plet F. C. , Drury M. J.
Published: April 2011

Geomagnetic depth-sounding data have been obtained along a profile across the northern Yukon and the Mackenzie Delta region that approximately parallels the east–west flow of the auroral electrojets near the geomagnetic latitude of 70°N. An internal conductive zone, in which electric currents are confined to a north–south direction, is defined by the large spatial variation of the vertical component of the time-varying geomagnetic field and of the horizontal component parallel to the profile. This conductive zone, with a half width of about 50 km, correlates with the Blow Trough, an element of the Beaufort–Mackenzie Basin, that contains at least 5 km of Mesozoic and Cenozoic clastic sediments. Model studies suggest that up to 10 km of conducting sedimentary materials occur within a basin-shaped structure and that a conducting zone (20 km wide) extends this basin to a depth of 20 km in the Earth's crust. This deeper conducting zone could be the result of movements along the Rapid Fault array, which dissects the Blow Trough and which may have fractured the materials beneath the basin or displaced sedimentary masses to greater depths. The observed negative Bouguer gravity anomaly is consistent with such a structure.
Paleomagnetism of Siluro-Devonian and Cambrian granitic rocks from the Avalon zone in Cape Breton Island, Nova Scotia
Authors: Rao K. V. , Seguin M. K. , Deutsch E. R.
Published: April 2011

As part of a major study of the Avalon zone in Cape Breton Island, we describe the paleomagnetism of radiometrically well-studied granitic rocks of two generations, representing the Acadian (350–450 Ma) and the Avalonian (520–580 Ma) Orogenies, respectively. Detailed alternating field (AF) and thermal experiments performed on the younger granites indicate that they are characterized by three different mean directions of magnetization in the 10–60 mT coercivity spectra: SE (D = 149°, I = +70°; K = 160, N = 4 sites); NE-1 (D = 72°, I = −70°; K = 320, N = 3 sites); and NE-2 (D = 31°, I = −24°; K = 67, N = 3 sites) with corresponding paleopole positions at CB-1 (16°N, 41°W; δp, δm = 6°, 7°); CB-2 (32°N, 97°W; δp, δm = 7°, 8°); and CB-3 (27°S, 96°W; δp, δm = 6°, 11°). The radiometric ages of these three remanence directions do not differ from each other by more than 50 Ma; these remanences are also present as low coercivity (5–25 mT) magnetizations in the Avalonian granites (10 sites). Antipole CB-3 agrees with other recently reported Early Devonian paleomagnetic results from the northern Appalachians. In contrast, the two other antipoles (CB-1 and CB-2) are located in southerly latitudes but do not differ significantly from poles of contemporaneous rocks in New Brunswick and Newfoundland. The "aberrancy" of southerly located Siluro-Devonian poles with respect to those in northern latitudes is discussed in the context of possible transcurrent motion of the "Acadia" displaced terrain with respect to cratonic North America. Presently available paleomagnetic data are not conclusive and cannot confirm or negate this possibility. The CB-1, CB-2, and CB-3 poles are interpreted as representing rapid apparent polar wander with respect to Cape Breton Island during Siluro-Devonian time.In the older Cambrian granites, pole CB (37°N, 176°E; δp, δm = 2°, 3°), derived from a high coercivity (20–70 mT) mean remanence direction NW (D = 318°, I = +15°; K = 298, N = 10 sites), probably corresponds to the Avalonian Orogeny. Further results are needed to interpret the paleogeographic setting of the Avalon microcontinent in early Paleozoic time.
The structure and relationships of the horned dinosaur Arrhinoceratops Parks(Ornithischia: Ceratopsidae)
Authors: Tyson Helen
Published: April 2011

Only the type specimen of Arrhinoceratops brachyops Parks can be assigned without question to the ceratopsid genus Arrhinoceratops. The original description, however, requires revision. Contrary to published accounts, a nasal horn core is present, the jugal cannot be characterized by an unusually long anterior process, and there is no nasal–rostral contact in this or any other known ceratopsian. Evidence for an interparietal is ambiguous. These and other observations necessitate a redefinition of the genus.Arrhinoceratops belongs to the long-squamosaled ceratopsids but is not closely related to any other genus in this lineage. With respect to characters of the frill, Torosaurus is the closest relative of Arrhinoceratops. Since the frills of Arrhinoceratops and Torosaurus form a graded series, the practice of automatically assigning isolated, fenestrated frills from Lance equivalent sediments to Torosaurus and from Horseshoe Canyon equivalent sediments to Arrhinoceratops should be abandoned.
A review of geomagnetic variation measurements in the eastern United States: implications for continental tectonics
Authors: Greenhouse J. P. , Bailey R. C.
Published: April 2011

Geomagnetic variation data for all available stations in eastern North America are presented here in the form of induction arrow maps at periods of 6, 20, and 64 min. The region is subdivided on the basis of the induction patterns revealed by these maps.The near-coastal stations are influenced by conductivity contrasts associated with the continent – ocean water interface, although the considerable variation in amplitude and in inland persistence of the coast effect reflects variations in the conductivity contrast across this transition. The predominantly southward-pointing arrows of the shield areas appear to reflect their source fields rather than subsurface conductivity. This pattern is disrupted by the high conductivity associated with the anomalously high crustal temperatures in the vicinity of the White Mountain heat flow anomaly and is terminated abruptly in the south by a well-defined reversal through northern New York State. We suggest that the conductivity boundary defined by this line of reversal continues southward to join a similar boundary observed near the Ohio – West Virginia border. These boundaries, with the crystalline Appalachians to the east, bound a segment of the crust (or upper lithosphere) whose conductivity structure is quite distinct from its surroundings.This region lies within the Central Geophysical Province of Diment et al.; however, if the poorly defined western and northern boundaries of that province are replaced by the line of reversal the two regions coincide. Some tentative models for its origins are discussed. We also suggest that the subdued geomagnetic coast effect in Virginia may be related to the extensive overthrusting of Paleozoic sediments by the crystalline Appalachians, which has been proposed on the basis of deep seismic reflection studies further to the south (Cook et al.).
The Shelburne dike, an early Mesozoic diabase dike in Nova Scotia: mineralogy, chemistry, and regional significance
Authors: Papezik V. S. , Barr Sandra M.
Published: April 2011

A diabase dike about 140 km long (the Shelburne dike) cuts in a northeasterly direction across the southwestern part of Nova Scotia. The dike, recently dated at 201 Ma, forms part of a major Appalachian system of diabase dikes and basaltic flows of early Mesozoic age, emplaced during the first stages of opening of the present Atlantic Ocean.The Shelburne dike is tholeiitic and quartz normative. Its chemistry resembles that of the Palisade sill of New Jersey, but differs substantially from the more primitive magnesian composition of a similar dike on the Avalon Peninsula of Newfoundland. A more advanced stage of differentiation is reflected also in the composition of its main minerals (augite, pigeonite, zoned orthopyroxene, calcic plagioclase). Such chemical variations among the roughly contemporaneous diabase dikes of the northern Appalachians complicate the existing petrogenetic and tectonic models of the development of the Appalachian dike swarm.
Snowmelt, glacier melt, and high arctic streamflow regimes
Authors: Marsh Philip , Woo Ming-ko
Published: April 2011

Most streamflow regimes in the high arctic have been distinguished as nival or proglacial according to the presence or absence of glaciers. A comparison of streamflow in glacierized and non-glacierized basins in a high arctic environment shows that runoff is sustained by various sources of water, including spring snowmelt, the melting of semi-permanent snow banks, glaciers, and rainfall. If spring melt dominates, a simple arctic nival regime results and if this is followed by summer glacier melt, a proglacial regime occurs. In some non-glacierized basins, however, if snowmelt is delayed until mid-summer or if semi-permanent snowbanks are abundant, a proglacial type of runoff pattern may be produced. The overall result is that various combinations of several sources of water will generate a suite of regimes that range from the simple nival to the typical proglacial pattern of flow.
Sedimentology and paleoecology of Upper Ordovician mounds of Anticosti Island, Quebec
Authors: Lake John H.
Published: April 2011

Relatively thin organic buildups in the Ellis Bay Formation of Anticosti Island developed in a shallow subtidal regressive marine shelf environment during the Late Ordovician. The Ellis Bay Formation has been subdivided into six members by Bolton. Two buildups, one in each of members 4 and 6, were studied in detail. The member 6 mud mound on the Salmon River (8 m thick) is bound by calcareous algae, stromatoporoids, and corals, and consists of a micritic bafflestone core capped by crinoidal lime grainstone. Early marine cementation permeated nearly all of the primary porosity. Cathodoluminescence indicates at least five stages of cementation of the mound. Constructive mound development was terminated by progressively shallowing, agitated marine conditions.The member 4 mound is a small coral (ecological) reef exposed on the Vaureal River.
Conodonts from the Cape Clay Formation (Lower Ordovician), southern Devon Island, Arctic Archipelago
Authors: Landing Ed , Barnes Christopher R.
Published: April 2011

As part of a program involving the Ordovician conodont faunas of southern Devon Island, Northwest Territories, 22 samples were processed from the Cape Clay Formation and lowest Nadlo Point Formation near Dundas Harbour. The Cape Clay Formation is 85 m thick and composed of bluff-forming mottled limestone and dolomitic limestone. A small but diverse conodont fauna of 229 elements was recovered in which 23 form and multielement species are represented. Several new taxa are described in open nomenclature, and multielement Utahconus? bassleri (Furnish) is discussed. The fauna is considered to represent Fauna C of the North American Midcontinent Faunal Province and is indicative of a late Tremadocian age. This fauna, in a unit with few macrofossils, indicates correlation of the Cape Clay Formation near Dundas Harbour with the upper Turner Cliffs Formation of the Foxe Basin, with the upper Copes Bay and (or) lower Baumann Fiord formations of Cornwallis, northwest Devon, and Ellesmere Islands of the Canadian Arctic, and with some portion of Ross–Hintze trilobite Zones A – lower D of the Great Basin.
Offset of an upper Pliensbachian geographic zonation in the North American Cordillera by transcurrent movement
Authors: Tipper H. W.
Published: April 2011

The north to south climatic zonation of upper Pliensbachian ammonites known in Europe has been recognized in the North American Cordillera. This simple geographic arrangement has been disrupted by northwest trending dextral transcurrent faults. With further documentation the amount of offset of these zones should provide a measure of the amount of movement on these faults since Pliensbachian time and further document the allochthoneity of the western part of the Cordillera.
The occurrence and origin of methane in some groundwater flow systems
Authors: Barker J. F. , Fritz P.
Published: April 2011

The origin of methane in selected groundwater flow systems is investigated through carbon isotope geochemical studies combined with hydrogeological and hydrogeochemical information. Methane is a common trace constituent in these groundwaters and occasionally constitutes a major carbon pool. Two modes of origin for methane are commonly recognized: microbial production (biogenic methane) and non-biological, chemical production (thermocatalytic methane). In the groundwaters sampled, the few thermocatalytic methanes encountered have δ13C values greater than about −45‰ whereas the more common normal biogenic methanes have δ13C values less than about −60‰. Biogenic methanes from sanitary landfill sites have intermediate δ13C values of about −38 to −56‰ and so can easily be distinguished from normal biogenic methane.The carbon source for biogenic methane is usually organic matter present in the aquifer materials. The carbon isotope ratios of dissolved methane and total inorganic carbon in sampled groundwaters are not controlled by equilibrium fractionation processes but by kinetic isotope effects. Secondary processes, such as microbial oxidation of methane, are important in establishing the carbon isotope ratio in some methanes.
Cambro-Proterozoic volcanism near Buckingham, Quebec
Authors: Lafleur Jean , Hogarth Donald D.
Published: April 2011

Grenvillian gneiss and marble of the Buckingham area, Quebec were intruded by a syenite–monzonite–diorite suite, overlain by trachyandesite, and, finally, intruded by diabase. The three igneous events are tentatively dated as late Proterozoic, Cambro-Proterozoic, and Cambro-Ordovician.The trachyandesites were extruded subaerially from en echelon vents or fissures. These rocks are highly oxidized and locally enriched in potassium, thought to be the result of late volcanic, gaseous, or hydrothermal transfer. They are preserved in a small, northeast-trending graben, part of the St. Lawrence Valley Rift System. This occurrence of Cambro-Proterozoic volcanic rocks is the first reported for the Canadian Shield of central Canada.
Late Quaternary paleoenvironments of the Morley Flats and Kananaskis Valley of southwestern Alberta
Authors: MacDonald Glen M.
Published: April 2011

A 3.1 m section of limnic sediment and peat from a bog on the Morley Flats and a 2.8 m section of limnic sediment from Wedge Lake in the Kananaskis Valley have yielded the first comprehensive late Quaternary biostratigraphic record from south-western Alberta. Both sections were analyzed for subfossil pollen, molluscs, and several sedimentary indices. Two distinct pollen zones were recognised. The basal zone, characterized by high relative abundancy of Artemisia–Salix–Juniperus, suggests that the Morley Flats were dominated by a sparse vegetation composed of aggressive pioneer species following deglaciation until prior to approximately 10 000 BP. Similarly, the mollusc fauna from this zone is dominated by northern ranging species. The second zone is typified by a predominance of Pinus and Picea. This reflects the expansion of coniferous forest into the region. Both the relative abundance of southern ranging mollusc species and the total carbonate concentration in the sediment increase in this zone. The vegetation of the region has remained generally stable since at least 9395 BP. However, increases in the abundance of Pinus relative to Picea and Abies in the mid-Holocene suggest that this period experienced an increase in fire frequency, possibly generated by climatic amelioration.