bluuebunny/crossref_metadata_2025 huggingface dataset:
The transition from dyke to sill in the Otish Mountains, Quebec; relations to host-rock characteristics
Authors: Chown E. H. , Archambault Guy
Published: April 2011

The Otish gabbro sills intrude Aphebian clastic rocks lying uncanformably on the Archean rocks of the Superior Province close to its juncture with the Grenville Province. The sills are undated but by inference may be ca. 1750 Ma. Two dyke swarms are known in the vicinity, the 1950 Ma, northwest-trending Mistassini dykes and a northeast-trending swarm of unknown age extending 600 km from Senneterre to the Otish Mountains and possibly another 300 km to the northeast. The trends of feeder dykes to the Otish sills are physically compatible with the dominant northeast dykes, which are therefore considered to be the feeders and should be called the Otish dykes.The Otish sills appear to be a unique occurrence along the 900 km dyke trend, possibly, but not entirely because of the chances of preservation. The general form of the Otish sill complex is a triangle bounded on the north by the east–west lip of the sedimentary basin, on the southwest by a northwest-trending Otish feeder dyke, and on the southeast by the underlying northeast feeder dykes. These dykes segment the sills into a series of four or five separate intrusive complexes, small in the northwest and becoming larger to the southeast. The regular inclination of tension fractures in the basal chilled margin of the sills suggests a crude pattern of flow from the feeder dykes inward to the centre of the sheets.Interpretation of the sedimentary sequence indicates that the Otish clastics were deposited higher on the paleoslope than the Mistassini carbonates. Although few dykes intrude the deeper basin, the magma rose and formed sills within the higher sequence. This variation may be explained by the different mechanical character of the two types of cover rock controlling the dyke behaviour. The relatively plasto-viscous Mistassini carbonate–shale sequence resisted the formation of tension fractures, whereas the brittle elastics opened easily, allowing the magma to rise into the stratified sequence, forming the sill complexes.
Late Wisconsin deglaciation and Holocene river evolution near Fort Nelson, northeastern British Columbia
Authors: Rampton V. N.
Published: April 2011

Glacial lakes were formed in the Fort Nelson area by eastward-retreating Laurentide glacier ice that dammed a number of streams. These lakes drained through spillways at progressively lower elevations as the ice retreated eastward. A terrace on the Muskwa River containing sediments dated ca. 9000 years BP indicates that the river had entrenched itself between 50 and 70 m below the surrounding upland by that time. Prior to final entrenchment by the Muskwa River to its present grade, a pause in downcutting ca. 9000 years BP occurred, resulting in the formation of the terrace.
Thermoluminescence dating applied to glaciolacustrine sediments from central British Columbia
Authors: Berger G. W. , Clague J. J. , Huntley D. J.
Published: April 2011

Glaciolacustrine and lacustrine sediments are important indicators of deglacial, interglacial, and nonglacial intervals within the Quaternary of Canada, yet there are no techniques for measuring their absolute deposition ages beyond the last ~ 50 000 years. In an attempt to develop an absolute dating tool for such sediments, we applied the partial bleach thermoluminescence (TL) dating technique to glaciolacustrine sediments of known age from central British Columbia. Samples were selected to represent both ice-proximal and ice-distal deposition and different modes of sedimentation.The results show clearly that both TL procedures and sedimentation processes, as reflected in the particle size and sedimentary structures of the samples, critically affected the accuracy of TL apparent ages. Specifically, care was required to isolate the effects of laboratory overbleaching, apparent glow-curve shifts, and inappropriate regression analysis. Clay-dominant layers lacking silt or sand interlayers produced expected ages, whereas sand- and silt-rich samples (with one exception) yielded excessive TL apparent ages. The single exception was a thin (9 mm), ice-distal, silt-rich layer.
The role of transiently fine-grained reaction products in syntectonic metamorphism: natural and experimental examples
Authors: Brodie K. H. , Rutter E. H.
Published: April 2011

It is proposed that one of the most important mechanisms of interrelationship between deformation and metamorphism is the facilitation of one of several grain-size-sensitive deformation mechanisms resulting from the formation of fine-grained products of a metamorphic reaction. During prograde metamorphism, such effects are likely to be transient, because grain coarsening and textural equilibration are likely in response to rising temperature conditions. Thus deformation mechanisms are often difficult to infer from such naturally deformed rocks.In localized shear zones exhibiting retrogressive metamorphism, evidence of enhanced deformability by such mechanisms is most likely to be preserved, because cooling conditions inhibit grain growth and both deformed and undeformed rocks are likely to be preserved.An experimental study has been made of the effects of deformation on serpentinite under conditions of progressive dehydration but with controlled pore pressure. A marked weakening (near-linear viscous rheology) at low strain rates was observed in association with the onset of dehydration to olivine. The enhancement of deformability is interpreted as due to the formation of thin, planar zones of ultrafine-grained but equiaxed (0.25 μm) olivine, which deform by diffusion-accommodated grain-boundary sliding. The experimental data therefore support the idea that a great deal of natural deformation during prograde metamorphism may occur in association with the transient existence of fine-grained reaction products, followed by grain growth and textural equilibration under essentially static conditions of relaxed stress.
Oriented growth of sillimanite in andalusite, Placitas – Juan Tabo area, New Mexico, U.S.A.
Authors: Vernon R. H.
Published: April 2011

In metapelitic schists near the Sandia granite in the Placitas – Juan Tabo area, New Mexico, nucleation sites for sillimanite are very variable, but growth of sillimanite in andalusite is common, either as bundles of fibrous ("fibrolitic") sillimanite crystals or as coarser grained parallel prisms or dendritic crystals of sillimanite. Optical relationships indicate a coaxial relationship between the andalusite and the sillimanite but with a and b axes interchanged. Stacking faults formed by dissociated screw dislocations in the andalusite may have provided nucleation sites for sillimanite. Some large sillimanite grains appear to have formed by coarsening of fibrous sillimanite, but others show no evidence of such coarsening. Some fibrous sillimanite occurs in folia in zones of inferred noncoaxial strain accumulation. Some occurs in radiating or crystallographically controlled aggregates in low-strain zones between sillimanite folia. These aggregates do not necessarily indicate postdeformation growth, except on a very local scale, and many of the fibrous sillimanite aggregates have been deformed. Hence, the sillimanite is a product of syndeformational rather than post-deformational metamorphism, as previously suggested, although regional metamorphism and granite emplacement may have been broadly synchronous. The andalusite–sillimanite microstructural relationships indicate a prograde P–T–time path similar to those occurring in other low-pressure (andalusite–sillimanite) metamorphic areas.
The role of fungi in the diagenetic alteration of spar calcite
Authors: Jones Brian , Pemberton S. George
Published: April 2011

Fungi may play a far more important role in carbonate diagenesis than has been previously suspected. This can be demonstrated by placing known species of fungi on crystals of Iceland spar calcite. Such experiments show that fungi can (1) cause sparmicritization through dissolution, (2) produce spiky calcite through dissolution, (3) trap and bind loose particles of calcite, and (4) promote the growth of new calcite crystals. Although not observed in this series of experiments, fungi can bore into substrates and cause sparmicritization. The activity of fungi involves a complex interplay of substrate destruction and construction without the intervention of vast quantities of fluid.
Depth trends in magnetic properties in an area of prolonged cold seawater drawdown in uppermost Troodos-type oceanic crust
Authors: Hall James M. , Walls Charles , Williamson Mark , Wang Bing-Xi
Published: April 2011

Study of the oxide minerals and measurements of the magnetic properties of about 100 samples distributed over a 475 m continuous drill-core section from the uppermost part of an extrusive sequence of the Troodos, Cyprus, ophiolite close to 35°02′N, 33°11′E, in the vicinity of Malounda, yields the following principal results: (1) Low-temperature alteration is intense to a depth of 260 m, below which it is relatively much subdued. (2) Saturation magnetization, natural remanence intensity, and initial susceptibility all increase continuously with depth throughout the section. (3) Curie temperature decreases with depth to 260 m, below which a change in the style of the thermal decay of magnetization behaviour takes place. (4) Pillowed and massive flows differ in their magnetic properties.The results are consistent with the downwards decrease in low-temperature alteration also noted by K. Gillis from the distribution of secondary minerals. The downwards variations in magnetic properties closely follow in both sense and magnitude the trends observed in DSDP hole 417A, where marked downwards decrease in low-temperature alteration also occurs. This comparison and the discontinuous nature of the lower units of the Troodos sedimentary cover in the vicinity of hole CY-1 support the interpretation of the upper, reddened facies of the Troodos extrusive sequence as being due to prolonged drawdown of cold seawater and suggest that the magnetization of at least the upper part of the Troodos ophiolite is a reliable guide to ocean crust magnetization.
West-southwest glacial dispersal of pillow-lava boulders, Philipsburg–Sutton region, Eastern Townships, Quebec
Authors: Elson John A.
Published: April 2011

Pillow-lava boulders, probably from Place Mountain in the Bolton valley east of the Sutton Mountains, occur in a narrow belt or fan 43 km long trending west-southwest (azimuth about 248°) from 10 km southwest of Place Mountains to Rosenberg, near Philipsburg, Quebec. Glacial striations with this direction are uncommon; the general glacial movement indicated by abundant striations and indicator erratics is southeastward. A southwestward flow in the axial part of the St. Lawrence Lowlands near Montréal is apparently the youngest direction there, of late Wisconsinan age. In the Eastern Townships of Quebec east and northeast of the study area and in adjoining northern Vermont there is evidence of a southwestward flow of mid-Wisconsinan age. Local southwestward flow in the study area at the beginning and end of a glacial cycle may have resulted from a mobile bed in the flooded St. Lawrence – Champlain lowland, but a hypothesis of flow from a major mid-Wisconsinan axis of accumulation in the northern Appalachians farther to the east is supported by much published field evidence.
Late Pleistocene depositional systems of Metropolitan Toronto and their engineering and glacial geological significance
Authors: Eyles N.
Published: April 2011

The municipality of Metropolitan Toronto (area 480 km2, population 2.15 million) is centrally located on the Late Pleistocene sedimentary infill of the Laurentian Channel, a broad bedrock low up to 115 km wide connecting the Huron and Ontario basins. This channel forms part of a relict (late Tertiary?) drainage network (the Laurentian River) modified by Pleistocene glacial erosion and infilled by over 100 m of glacial and interglacial sediments. The subsurface stratigraphy of the channel fill below Metropolitan Toronto has been established from many different data sources and is depicted, in this paper, as a series of cross sections with a total length of nearly 105 km.The subsurface stratigraphy has been divided, provisionally, into five depositional complexes, which have been mapped in the subsurface along several transects. These are (1) a glacial complex of Illinoian (?) age, (2) a lacustrine complex of Sangamon Interglacial and earliest Wisconsinan sediments (120 000 – 75 000 BP?), (3) a glaciolacustrine – lacustrine complex spanning the Early and Mid-Wisconsinan (75 000 – 30 000 BP?), (4) a Late Wisconsinan (> 30 000 BP) glacial complex, and (5) a postglacial lacustrine complex (ca. 12 000 BP).The data presented in this paper are significant for applied geological investigations in the heavily urbanized Toronto area and provide new insights into the glacial history of the Ontario Basin, in particular the regional extent of the Laurentide Ice Sheet margin prior to the Late Wisconsinan.
Clay mineralogy of late Cenozoic sediments in the CESAR cores, Alpha Ridge, central Arctic Ocean
Authors: Dalrymple Robert W. , Maass Oliver C.
Published: April 2011

The clay-sized (< 2 μm) fraction of the silty and arenaceous lutites constituting CESAR cores 14 and 103 (Alpha Ridge, central Arctic Ocean) is composed predominantly of mica (40–60%), with subequal percentages (10–20%) of kaolinite and chlorite and lesser amounts (< 5%) of smectite, quartz, plagioclase, and potassium feldspar. Calcite and dolomite also occur, but only intermittently in the upper 1.2 m; dissolution is probably responsible for their absence in other units. The silty lutites have a constant mineralogy throughout the 4.5 m long (~ 4.25 Ma) section, whereas some of the arenaceous intervals in the upper 2.1 m have markedly higher amounts of kaolinite, calcite, dolomite, and, to a lesser extent, smectite. The silty lutites were most likely derived from the Beaufort Sea shelf during nonglacial periods, whereas the distinctive components in the sandy layers suggest that they were transported from the Canadian Arctic Islands and Greenland by glacial ice. The absence of kaolinite peaks in the lower half of the core implies that the western Arctic Islands were not glaciated prior to 2.1 Ma, a conclusion supporting previous findings that the climate of the Arctic was warmer in the Pliocene.
Heat production and thermal conductivity of rocks from the Pikwitonei–Sachigo continental cross section, central Manitoba: implications for the thermal structure of Archean crust
Authors: Fountain David M. , Salisbury Matthew H. , Furlong Kevin P.
Published: April 2011

The Pikwitonei and Sachigo subprovinces of central Manitoba provide a cross-sectional view of the Superior Province crust. In cross section, the upper to mid-level crust is composed of synformal greenstone belts surrounded by tonalitic gneisses, both of which are intruded by granitoid plutons. This crustal structure persists downward into the granulite facies, where keels of the greenstone belts can be found. To constrain thermal models of the crust, we measured heat production and thermal conductivity in 60 rocks from this terrain using standard gamma-ray spectrometry and divided bar techniques. Large vertical and lateral heterogeneities in heat production in the upper crust are evident; heat production is high in granites and metasedimentary rocks, intermediate in tonalite gneisses, and low in the portions of greenstone belts dominated by mafic meta-igneous rocks. In the deeper granulite facies rocks, heat production decreases by a factor of two in the tonalitic gneisses and remains low in the high-grade mafic rocks. When applied to the Pikwitonei–Sachigo crust cross section, the laboratory data here do not support step function or exponential models of the variation of heat production with depth. However, estimates of surface heat flow and surface heat production for various sites in the crustal model yield the well-known linear relationship between surface heat production and surface heat flow observed for heat-flow provinces for both one- and two-dimensional models. This demonstrates that determinations of heat production with depth based on inversion of the linear heat-production–heat-flow relationship are nonunique.
The Northwest Atlantic Mid-Ocean Channel of the Labrador Sea. V. Sedimentology of a giant deep-sea channel
Authors: Hesse Reinhard , Chough Sung Kwun , Rakofsky Allan
Published: April 2011

The Northwest Atlantic Mid-Ocean Channel (NAMOC) is one of the largest deep-sea channels of the world's oceans. During the late Cenozoic glacial period, the channel played a major role in the depositional history of the Labrador Sea and northwest Atlantic in controlling sedimentation of a broad (approx. 500 m thick and 200 km wide) lens of turbidites. This sediment sequence interfingers laterally with the acoustically transparent pelagic and contourite facies found in the Labrador Basin. The meandering channel is a depositional–erosional feature formed by submarine mass flows, predominantly turbidity currents.The channel contains a meandering talweg that appears to be associated with a sequence of submarine point bars containing thick-bedded, coarse-grained turbidites and gravel layers (channel-fill facies). Old channel positions on seismic profiles indicate that the channel has migrated laterally up to 30 km both to the west and to the east.Natural levees flank the channel for its entire length, extending laterally into turbidite plains 60–100 km wide. The spill-over facies comprises thin-bedded, fine-grained turbidites dominated by thinly laminated muds. Individual units of parallel-laminated mud, which result from single turbidity currents overtopping the channel banks, average 3 cm in thickness. A layer by layer correlation of a sequence of spill-over turbidites is possible between two adjacent cores 70 km apart. Coarse-grained off-channel sediments recently discovered on both levees at distances up to 55 km from the NAMOC occur in tributary channels.Turbidity current activity in the channel probably started with the onset of glaciation at about mid-Pliocene time and ceased at about 7000 years BP, when deglaciation proceeded rapidly. The sedimentation rate for the last episode of overbank deposition on the levees, which probably occurred between 11 000 and 7000 years BP, is 13 cm/1000 years. Towards the end of glacial episodes the northwestern Labrador Sea was probably covered with sea ice.
Late Holocene solifluction lobe activity in the Mount Rae area, southern Canadian Rocky Mountains
Authors: Smith Daniel J.
Published: April 2011

Solifluction lobes are tongue-shaped accumulations of sediment resulting from localized periglacial mass wasting. Radiocarbon records from beneath two turf-banked lobes in the Mount Rae area of the southern Canadian Rockies indicate that solifluction processes have been continuously active for at least the last 2000 years. The long-term rates of frontal movement at both sites average 0.49 cm/year, but vary in magnitude from 0.35 to 1.50 cm/year.Both lobes terminate above soil pedons progressively overridden by their advance. Estimates of the apparent mean residence time of the contemporary soil ranges from 962 ± 100 years in one case to 1600 ± 100 years in the other. This information was used to reconstruct a chronology of lobe activity. Collectively, the radiocarbon records indicate that solifluction lobes in this area were advancing quite rapidly between 1900–1750 years BP but declined to a much slower, but relatively constant, pace up until the present.
Source requirements for the Golden Mile, Kalgoorlie: significance to the metamorphic replacement model for Archean gold deposits
Authors: Phillips G. Neil , Groves David I. , Brown Isobel J.
Published: April 2011

The Golden Mile at Kalgoorlie represents a giant Archean hydrothermal gold system localized by ductile shear zones and hosted mainly by a differentiated tholeiitic sill. Chlorite, carbonate, and pyrite alteration zones cover the whole mineralized area (1 km × 3 km), and calculations suggest that for the Golden Mile (production around 1200 t Au), the amounts of components added to these alteration zones are 340 Mt CO2, 20 Mt K, and 5 Mt S. If one adopts a metamorphic-replacement model for gold mineralization in which all ore components derive from devolatilization of greenstones at amphibolite facies or above, these data suggest that a source area involving a 5 km thick greenstone slab of area 8 km × 8 km could produce the necessary CO2, K, S, H2O, and Au. This is considered a reasonable volume of greenstone belt, and under such a model the minimum spacing of large gold deposits would be approximately 20 km along strike.Neither special Au-enriched source rocks nor unreasonably large volumes of greenstone belt are required to produce a giant gold deposit. Instead, the most critical parameters are suitable structural environments providing focussing of fluids and multiple channelways through specific Fe-rich, low-tensile-strength host rocks to ensure efficient depositional mechanisms.
Quebecius quebecensis (Whiteaves), a porolepiform crossopterygian (Pisces) from the Late Devonian of Quebec, Canada
Authors: Schultze Hans-Peter , Arsenault Marius
Published: April 2011

Quebecius quebecensis (Whiteaves 1889) is a porolepiform crossopterygian related to Glyptolepis. A large nariodal, a large tabular, a separate intertemporal, and a large fused nasosupraorbital are features of Quebecius that characterize it as a porolepiform. The small size of the operculum, median extrascapular larger than the lateral one, small lower squamosals, and deep maxilla are additional features separating Quebecius from Glyptolepis. As in Glyptolepis, the median fins are not lobed. The pectoral fin possesses a long fleshy lobe. The internal, ventral side of the broadly based pelvic fin suggests that the internal axis has shifted towards the body. Pectoral fins with a long fleshy lobe are a common feature of porolepiforms, but lobed bases in the pelvic and unpaired fins are a feature found in Holoptychius, and not in Glyptolepis and Quebecius. Quebecius quebecensis is conspecific with Quebecius williamsi Schultze 1973, mistakenly described as an onychodont crossopterygian.
A model for glacial and proglacial sedimentation in the shield terrane of southern Ontario
Authors: Kaszycki Christine A.
Published: April 2011

Zonal stagnation is an important element in the regional style of deglaciation in areas of moderate bedrock relief (50–150 m), such as the shield terrane of southern Ontario. Bedrock topography played a major role in the stagnation process, as ice blocks were trapped within bedrock basins of all sizes. Stagnation occurred subglacially as the ice sheet thinned and trapped basal ice became increasingly isolated from its source. Sediment–landform relationships support this model. Bedrock lakes are floored by highly faulted laminated sediment, often displaying large ice-block casts. The dominant depositional landforms are ice-contact terraces, which flank valley walls. Sediment forming the terraces is variable, depending upon ice-marginal depositional environment.Models for two depositional systems are developed: (1) localized ice-marginal and subglacial sedimentation in upland terrain, and (2) thick proglacial basin-fill sequences developed in major structural valleys. In upland areas, sediment cover is thin and discontinuous and is composed primarily of complex sediment-flow assemblages. Basal till is rare but occurs as two distinct lithofacies representing (1) meltout from beneath wholly stagnant ice, and (2) deposition by basal melting from thin slabs of stagnant, debris-rich ice lodged beneath an active shear zone. Thick proglacial basin-fill sequences exhibit complex facies relationships. Ice-contact lacustrine terraces comprise fining-upward subaqueous outwash sequences, developed as density underflows were funnelled between rock knobs and blocks of stagnant ice. Kettle lakes developed within large basins where ice blocks persisted for the longest period of time.
Nazko cone: a Quaternary volcano in the eastern Anahim Belt
Authors: Souther J. G. , Clague J. J. , Mathewes R. W.
Published: April 2011

Nazko cone, located in central British Columbia at the eastern end of the Anahim Volcanic Belt, is the product of at least three episodes of Quaternary volcanic activity. An eroded Pleistocene subaerial flow at the base of the pile is overlain by a subglacial mound of hyaloclastite that is, in turn, partly covered by a younger composite pyroclastic cone and associated lava flows. A whole-rock K–Ar date of 0.34 ± 0.03 Ma on the oldest flow is consistent with a hotspot model for the Anahim Belt and implies absolute late Neogene motion of 2.6 cm/year for North America. The hyaloclastite mound was erupted beneath the Cordilleran Ice Sheet during the Late Pleistocene, perhaps during the Fraser Glaciation (25 000 – 10 000 years BP). Radiocarbon dates from peat above and below Nazko tephra in a bog near the cone suggest that the volcano last erupted about 7200 years BP.Nazko basalt has 10–15% normative nepheline and is classified as basanite. This is significantly more undersaturated than basalts farther west in the Anahim Belt and may indicate an eastward shift toward a deeper or less depleted mantle source.
ESR dating of Pleistocene fossil teeth from Alberta and Saskatchewan
Authors: Zymela Steve , Schwarcz Henry P. , Grün Rainer , Stalker A. MacS. , Churcher C. S.
Published: April 2011

Teeth collected from Pleistocene surficial sediments in southeastern Alberta and western Saskatchewan have been dated by electron spin resonance (ESR). The dates generally agree with the previously determined temporal sequence of the deposits, largely based on studies of fossil vertebrates and supplemented by some absolute ages, but the absolute ages of the oldest deposits appear to be much younger than previously estimated. Absolute ages (ESR) have been compared with faunal ages (using nomenclature of Stalker and Churcher): the age of Aftonian – early Kansan deposits at the Maser–Frisch site is 450 ± 30 ka; Kansan deposits in the Medicine Hat region range from 410 to 250 ka; Sangamon deposits at Mitchell Bluff are 67 ± 12 ka; middle Wisconsinan deposits at Empress, Alberta, are 34 ± 4 ka; postglacial beds near Medicine Hat give ages of 11 ± 2 ka (in agreement with 14C ages). At Wellsch Valley, however, ESR dates (280 ± 35 ka) are much younger than the age of about 1.5 Ma obtained from fauna, fission track, and paleomagnetics. This discrepancy may be due to late introduction of U into the teeth.
Cretaceous (Albian–Turonian) foraminiferal biostratigraphy and paleogeography of northern Montana and southern Alberta
Authors: Lang Harold R. , McGugan Alan
Published: April 2011

In Albian–Turonian time, the interior of North America was flooded by a seaway extending from the present Gulf of Mexico to the Arctic Ocean. Detailed studies of this interval north and south of the Canada – United States international border have not usually been integrated. The present foraminiferal biostratigraphic study includes a 38 000 km2 area straddling the Alberta–Montana border from the Lewis thrust in the west to the Sweetgrass Hills in the east, including the Sweetgrass Arch.Stratigraphic cross sections and isopach maps of six Albian – early Turonian stratigraphic units prepared from 57 surface and subsurface sections demonstrate that sedimentation was controlled primarily by (i) sporadic volcanism to the west and (ii) tectonic activity coincident with the present location of the Sweetgrass Arch.The occurrence of the late Cenomanian planktonic foraminifer, Rotalipora cushmani, in association with three other keeled species, suggests an east–west marine connection between the eastern Pacific and Western Interior. This interpretation is consistent with the facies model described by Kauffman, the paleogeographic model developed in the present study, reported gastropod paleozoogeographic data, and reevaluation of pelecypod and ammonite paleozoogeographic interpretations.
Pingo collapse and paleoclimatic reconstruction
Authors: Mackay J. Ross
Published: April 2011

Long-term field studies of contemporary pingo growth, collapse, and rampart formation along the western Arctic coast of Canada provide criteria that may be helpful in the identification of pingo ramparts in nonpermafrost environments. Such criteria include the volume of the ramparts, which should approximate that of the enclosed depressions from which the rampart materials were derived; peripheral deposits associated with mass wasting, streamflow, and debris flow; casts of dilation crack ice trending across the ramparts; and high-angle peripheral normal faults. The conventional method of correlating the present mean annual air temperature with the present pingo distribution to establish warm-side limiting temperatures for paleoclimatic reconstruction is unsound, because most pingos in North America and the Soviet Union commenced growth hundreds to thousands of years ago under mean annual air temperatures that may have differed greatly from those of the present. Some other factors to be considered in paleoclimatic reconstruction are the thermal offset; site availability; the differing requirements for the growth of large pingos as compared with small pingos; and the long time required for pingos to grow to full size.
Sediment distribution and sea-floor morphology of Storbanken: implications for the glacial history of the northern Barents Sea
Authors: Solheim Anders , Milliman John D. , Elverhøi Anders
Published: April 2011

Acoustical (sparker, 3.5 kHz, and side-scan sonar) and sedimentological data from a local study on Storbanken in the northern Barents Sea support the concept of a late Weichselian ice sheet covering most of the Barents Sea. During a major halt in the retreat of the ice sheet, locally thicker (38 m) accumulations of ice-proximal glaciomarine sediments were deposited, after which rapid retreat took place. Sea-floor morphology indicates that the retreat across Storbanken most likely took place without surging or climatically controlled oscillations.Intense iceberg ploughing characterizes the sea floor down to water depths of 210–220 m. Most of this is relict, but occasional gouges in the shallowest regions may have had a more recent origin. The apparent lower limit of ploughing, interpreted in terms of relative sea level, indicates a rather moderate isostatic depression. This probably resulted from a thin ice sheet, fed from several ice source areas. Depth of the plough marks is largely dependent on thickness of the glaciomarine sediments. A thin and patchy layer of overcompacted till fills local depressions in the sedimentary bedrock surface and forms a flat base for iceberg ploughing.
Structural geology of the Blake River Group at the Bousquet mine, Abitibi, Quebec
Authors: Tourigny Ghislain , Hubert Claude , Brown A. C. , Crépeau Robert
Published: April 2011

In the Bousquet mining district, metamorphosed volcanic rocks of the Blake River Group (BRG) exhibit discrete strain features resulting from three generations of structures—D1, D2, and D3. Deformation D1 formed an east–west-trending, subvertical, penetrative schistosity that is coplanar with the axial plane of associated folds. This foliation contains a linear fabric plunging steeply westward, and mineral lineations are subparallel to fold axes and to intersection lineations.Defomations D2 and D3 formed a crenulation cleavage and a set of conjugate kink bands, respectively. The cleavage is oriented east–northeast, and the kink bands are oriented northeast–southwest and northwest–southeast. Both deformations distorted earlier-formed structures to a minor extent. A conjugate set of minor strike-slip faults with orientations similar to the kinks are the youngest structures found in BRG rocks.The volcanic sequence is composed of two lithotectonic domains juxtaposed along fault-related contacts. Each domain exhibits distinctive strain features attributed mainly to a broad network of anastomosing faults. This network of faults disrupted strata and destroyed many internal stratigraphic features, especially in domain 2; it relates to late stages of D1.Domain 1, occupying the northern half of the BRG in the mine area, represents a zone of weakly sheared tholeiitic basalts 750 m thick and is overlain by 150 m of felsic volcaniclastic rocks. Primary textures and structures indicate that this domain forms a south-facing homoclinal succession.Domain 2 is characterized by a strongly strained, 500 m wide belt of anastomosing faults adjacent to the southern margin of domain 1. Narrow bands of schist, mylonite, and phyllonite straddle fault zones and surround less-deformed, lozenge-shaped blocks of metamorphosed volcanic and (or) volcaniclastic rocks.The lack of syngenetic structures and textures, together with intense faulting and transposition, restricts stratigraphic correlations throughout the BRG as well as correlations between this volcanic succession and the adjacent sedimentary units. Structural evidence presented here complicates the original stratigraphic scheme commonly applied to volcano-sedimentary assemblages in the Rouyn–Val D'Or area. It is proposed that faulting is responsible for the spatial distribution of lithologies previously interpreted as resulting from folding phenomena in the Bousquet mining district. Gold mineralization is concentrated in bands of deformed rocks in the fault zones of domain 2 at the Bousquet mine.
Lower Devonian platform carbonates from Kasaan Island, southeastern Alaska, Alexander Terrane
Authors: Soja Constance M.
Published: April 2011

Facies representing shallow subtidal conditions, an open lagoon or shelf, offshore biostromal banks, and a restricted lagoon or shelf form the Lower Devonian (Emsian) sequence of rocks exposed on Kasaan Island in southeastern Alaska. This complex of carbonate environments developed in an island arc, which is now preserved within the accretionary Alexander Terrane. The lower part of the platform sequence represents the restricted shallow subtidal zone and consists of rhyolitic tuffs and lime mud-stones and wackestones containing low-diversity assemblages of leperditiid ostracodes and loxonematid-like gastropods. Following the end of volcanic activity, dendritic corals and branching stromatoporoids colonized the outer, deeper portions of the subtidal zone. Higher in the sequence, boundstones consisting of massive stromatoporoids are associated with brachiopod packstones that together represent the growth of biostromal colonies at the seaward edge of the platform and the diversification of normal marine biota within a lagoon or shelf. Restricted circulation eventually developed across vast portions of the lagoon or shelf, which resulted in the expansive growth of Amphipora and the decline in all other invertebrate populations.The sequence preserved in the rocks on Kasaan Island records a period of waning volcanic activity within the arc, which is marked by the relatively thick cover of lime sediments that accumulated on an evolving carbonate platform. The apparent lack of coeval limestones that exhibit identical stratigraphic successions in other parts of the Alexander Terrane probably reflects the evolution of isolated carbonate platforms adjacent to submarine or subaerial topographic highs that developed locally within the arc during or before the Early Devonian.
Lithostratigraphy of the Cambrian – Lower Ordovician Saint John Group, southern New Brunswick
Authors: Tanoli Saifullah K. , Pickerill Ron K.
Published: April 2011

The Cambrian – Lower Ordovician Saint John Group of the Saint John area, southern New Brunswick, has historically been subdivided into 11 formations. The existing scheme is inappropriate, however, as many of the supposed formations, particularly those of Middle Cambrian–Early Ordovician age, were distinguished on a biostratigraphic rather than lithostratigraphic basis. We suggest the sequence can be more appropriately subdivided into seven formations, each of which can be clearly and easily identified by the field geologist. Lower Cambrian formations comprise, from base to top, the Ratcliffe Brook, Glen Falls, and Hanford Brook formations, all of which are retained from the previous nomenclature. Middle Cambrian strata comprise the Forest Hills Formation (to replace the Fossil Brook and Porter Road formations) and Upper Cambrian strata the King Square Formation (to replace the Hastings Cove and Agnostus Cove formations) and Silver Falls Formation (to replace the Black Shale Brook and Narrows formations). Lower Ordovician strata are referred to as the Reversing Falls Formation (to replace the Navy Island and Suspension Bridge formations). Descriptions of each formation are given, major sections of each are included, and stratigraphic correlation of the sequence in different geographic areas is demonstrated.
Nonglaciogenic deltaic deposits in the early Proterozoic Gowganda Formation, Cobalt Basin, Ontario
Authors: Rainbird R. H. , Donaldson J. A.
Published: April 2011

The Gowganda Formation in the eastern part of the Cobalt Basin comprises the Coleman Member and the conformably overlying Firstbrook Member. The Firstbrook Member differs from the Coleman Member in that its lithofacies display (i) marked lateral continuity, (ii) abundant diagenetic red colouration, (iii) evidence of tidal deposition, and (iv) a lack of glaciogenic features. The Firstbrook Member is here divided into a mud-dominated lower facies, a silt-dominated middle facies, and sand-dominated upper facies. These are respectively equated with the prodelta, delta slope, and delta foreslope subenvironments of a prograding river-dominated deltaic wedge composed of coalescing deltas (probably braid deltas). The deltaic wedge was likely fed by a fluvial system analogous to the braidplain system that prevailed during deposition of the overlying Lorrain Formation. Uninterrupted delta progradation is suggested by a single coarsening-upward sequence up to 535 m thick. Deposition probably occurred within a marine rather than lacustrine basin.
Seal (Phoca sp.) from Champlain Sea deposits near Ottawa, Canada
Authors: Naldrett D. L.
Published: April 2011

The left tibia of a juvenile seal (Phoca sp.) was recovered from the interchannel sand and gravel facies of the Twin Elm ridge near Ottawa, Ontario. The sand and gravel were deposited in the Champlain Sea as subaqueous outwash, indicating the tibia must have been introduced after postmortem disarticulation and transport. The high degree of abrasion indicates either lengthy transport or high flow energy within the outwash channel.
A comparison of magnetic character and alteration in three granite drill cores from eastern Canada
Authors: Harding K. L. , Morris W. A. , Balch S. J. , Lapointe P. , Latham A. G.
Published: April 2011

Bulk magnetic susceptibility (BMS) measurements have been made on granite drill cores from the St. George batholith (New Brunswick), the South Mountain batholith (Nova Scotia), and the Wedgeport pluton (Nova Scotia). The primary magnetite concentrations of the two Nova Scotia cores are statistically indistinguishable, thus lending support to the hypothesis that the Wedgeport pluton, despite being 50 Ma younger, is a satellite of the South Mountain batholith.The St. George core has a primary magnetite concentration over 30 times greater than the Nova Scotia cores, but low-temperature alteration (attributable to subsurface weathering) has greatly reduced its magnetite content. The two Nova Scotia S-type granites are shown to fall into the ilmenite-series category, whereas the St. George granite, which is either S- or A-type, is transitional between the magnetite and ilmenite series.The general observation of intergranular hematite and reduced BMS in the outcrops of some granites is suggested to have important consequences for primary oxidation studies and aeromagnetic interpretation.
Stratigraphy of the Sixteen Mile Creek lagoon, and its implications for Lake Ontario water levels
Authors: Flint J. E. , Dalrymple R. W. , Flint J. J.
Published: April 2011

The sequence of units (from the base up) in the Sixteen Mile Creek lagoon (Lake Ontario) mimics the longitudinal sequence of surficial environments: pink silt—overbank (flood plain – dry marsh); bottom sand—stream channel and beach; orange silt—marsh; gyttja—wet marsh and very shallow (deltaic) lagoon; and brown and grey clay—open-water lagoon. This entire sequence accumulated over the last 4200 years under slowly deepening, transgressive conditions caused by the isostatic rise of the lake outlet. Land clearing by European settlers dramatically increased the supply of clastic sediment and terminated the deposition of the organic-rich silty clays (gyttja) that make up most of the lagoon fill.Because the gyttja and beach sand are interpreted to have accumulated in water depths of less than 0.5 m, the elevation–time plot of 14C dates from these units can be used to reconstruct a very closely constrained lake-level curve. The data indicate that water levels have risen at an average rate of 0.25 cm/a over the last 3300 years as a result of differential, isostatic rebound. Superimposed on this trend are water-level oscillations with amplitudes on the order of 1 m and periods of several hundred years. These oscillations are synchronous and in phase with water-level fluctuations in Lake Michigan, and with a variety of other climatic variations in North America and Europe. We propose, therefore, that the water-level oscillations are a result of long-term, climatically produced variations in precipitation in the Great Lakes drainage basin.
Glacial geology of the Torngat Mountains, Labrador
Authors: Clark Peter U.
Published: April 2011

Two late Quaternary alloformations are identifed throughout the Torngat Mountains by degree of soil profile development in till with a granitic composition, morphologic expression of deposits, and their relative areal distribution. The two alloformations are interpreted to represent two, successively limited glaciations of the Torngat Mountains by the Laurentide Ice Sheet. Deposits of the Shoal Cove Alloformation mantle hillslopes distal to deposits of the younger Saglek Alloformation. Deposits are primarily soliflucted till found around coastal regions. Soils developed in till of the Shoal Cove Alloformation are characterized by well-expressed Bw horizons ≥ 19 cm thick. Deposits of the younger Saglek Alloformation are characterized by prominent, well-preserved moraines, outwash fan surfaces, and ice-marginal channels. Soils described in till are poorly developed, with A horizons directly overlying Cox horizons, or separated from Cox horizons by thin, transitional (AC, CA) horizons or poorly expressed Bw horizons. During deposition of this alloformation, the Laurentide Ice Sheet was confined to major valleys and fiords, leaving large areas of the mountains ice free. Old radiocarbon dates on shells from diamictons on the Iron Strand coast do not provide a unique age for glacial events on the Labrador coast. Age of marine limit on the coast suggests deglaciation from the event depositing the Saglek Alloformation began 9 000 – 10 000 years BP.
Stratigraphy and tectonic significance of Cretaceous volcanism in the Queen Elizabeth Islands, Canadian Arctic Archipelago
Authors: Embry Ashton F. , Osadetz Kirk G.
Published: April 2011

Cretaceous volcanic rocks, which consist mainly of basalt flows and pyroclastic rocks, occur on northern Ellesmere Island, Axel Heiberg Island, and northernmost Amund Ringnes Island as part of the Sverdrup Basin succession. Volcanic rocks are associated with each of four regional transgressive–regressive (T–R) cycles that constitute the Cretaceous clastic succession of Sverdrup Basin and are of Valanginian – early Barremian, late Barremian – Aptian, latest Aptian – early Cenomanian, and late Cenomanian – Maastrichtian age; the volcanic component of each increases northward. The centre of volcanism appears to have been north of Ellesmere Island and is interpreted as the site of a mantle plume that was active throughout the Cretaceous.Most of the volcanic activity took place from Hauterivian to early Cenomanian (T–R cycles 1–3) and was accompanied by widespread sill and dyke intrusion. This activity coincided with the main rifting phase of the adjacent oceanic Canada Basin and with minor crustal extension in the Sverdrup Basin. From late Cenomanian to Campanian, volcanism was restricted to the extreme northeast, and trachytes and rhyolites were extruded along with basalts. This volcanic succession is interpreted as being the southern limit of Alpha Ridge, a major volcanic edifice that formed as a hot-spot track across Canada Basin during sea-floor spreading in Late Cretaceous.
An energy-budget snowmelt model for the Canadian Prairies
Authors: Gray D. M. , Landine P. G.
Published: April 2011

Meltwater released by shallow snow covers of the Canadian Prairies is an important water resource to the region. Therefore, many water-management agencies are interested in methods of forecasting streamflow and seasonal water yield from snowmelt. Reliable, accurate forecasts, however, require information of the time of melt and snowmelt rates and volumes. At the present time these quantities are usually estimated by simple temperature-index methods, which have not proven successful in open grassland environments.The paper describes the development and testing of a snowmelt model that uses the energy equation as its physical framework. Empirical procedures for evaluating radiative, convective, advective, and internal-energy terms from standard climatological measurements are presented. Algorithms for accounting for changes in the energy terms in a daily energy-balance model are described.The application of the energy-budget snowmelt model (EBSM) for predicting ablation and simulating streamflow from small and large watersheds is evaluated. It is demonstrated that the EBSM is workable in an operational forecast system and when incorporated within such a system leads to general improvement in synthesizing streamflow from snowmelt.
Late Pleistocene and Holocene vertebrates and palaeoenvironments from Charlie Lake Cave, northeast British Columbia
Authors: Driver Jonathan C.
Published: April 2011

Excavations outside Charlie Lake Cave, Peace River District, British Columbia, revealed deposits dating from ~10 700 BP to the present. The earliest fauna (10 700 – 10 000 BP) was deposited when the newly deglaciated landscape was largely unforested and included bison (Bison sp.), ground squirrel (Spermophilus sp.), a large hare (Lepus sp.), snowshoe hare (Lepus americanus), and a variety of birds, including the Cliff Swallow (Hirundo pyrrhonota). By 10 000 BP snowshoe hare (Lepus americanus) was the most numerous mammal, indicating the development of forested conditions. By 9000 BP the fauna resembled the modern Peace River fauna prior to European settlement, typical of a largely forested landscape, with wetland areas indicated by aquatic avian species. Subsequent Holocene climatic fluctuations are not evident in the faunal record.