bluuebunny/crossref_metadata_2025 huggingface dataset:
Trace metal geochemistry in sediments from the Miramichi estuary, New Brunswick
Authors: Willey Joan D. , Fitzgerald Robert A.
Published: April 2011

Organic matter, mineralogy, and texturally-related qualities combine to control the total concentration and reactivity of trace metals in the sediments of the Miramichi estuary. Concentrations of lignin-rich organic matter, up to 10% of the total sediment weight in the central estuary, correlate with analytical results for trace elements which show that more than 40% of the total Mn, Zn, and Cu is held in the oxidizable and organically-bound form. Mineralogical influences are most obvious in the river portion of the system where total Mn concentrations average 695 μg/g, Zn averages 282 μg/g, Cu averages 32 μg/g, and Pb averages 200 μg/g in the less than 63 μm size fraction of the sediments. In the marginal marine Miramichi Bay, total concentrations of these four trace elements in the fine sediment fraction are diminished by 9–57%, with respect to the equivalent size fraction of the river sediments.The concentration of all trace elements in the coarse fraction (> 63 μm) is considerably less as compared with the fine fraction. In these sediments mineralogical associations are more pro nounced. Very high organic carbon content (up to 23%) is associated with sediments in which more than 25% of the Mn, Zn, and Cu is organically bound. Weak acid leachable Ca in the coarse sediments of the bay is 21 times higher as compared with the equivalent river sediment fraction and this CaCO3 indication is associated with a twofold increase in total Cu and Pb.When compared with sediments from other areas of eastern Canada, the Miramichi sediments have at least twice as much weak acid leachable Zn, and this higher level of reactive metal is associated with high organic carbon content in the top 15 cm of cored sediments. Suggested sources for this recent addition of metal in association with organic matter are the mining activities as well as urban and industrial effluents.
Zircon ages for the Pelly Gneiss and Klotassin granodiorite in western Yukon
Authors: Tempelman-Kluit Dirk , Wanless R. K.
Published: April 2011

Two samples of Pelly Gneiss with different field relations and post-crystallization histories give different U/Pb ages that are Devonian and Permian (375 and 276 Ma). A sample of Klotassin granodiorite gave an age of 192 Ma confirming its Early Jurassic age. These Devonian, Permian, and Jurassic plutonic rocks in Yukon Crystalline Terrane lack equivalents in the adjacent Omineca Belt where sedimentary strata accumulated at these times. This suggests that the Yukon Crystalline Terrane is allochthonous with respect to the Omineca Belt.
Some problems of late Wisconsin history and geochronology in southeastern Ontario
Authors: Terasmae J.
Published: April 2011

Palynological studies and radiocarbon dating of sediments from about 20 lakes and bogs in southeastern Ontario have been used to establish a palynostratigraphic sequence of six pollen zones extending to approximately 12 000 years BP and indicating that deglaciation occurred between 12 500 and 11 500 years BP, probably during the Two Creeks interstadial interval.The glacial Lake Iroquois existed in the Lake Ontario basin from about 12 500 – 11 800 years BP while the Lake Ontario ice lobe was retreating northeastward, and the Kirkfield – Fenelon Falls outlet from glacial Lake Algonquin (in the Georgian Bay – Lake Huron basin) to Lake Iroquois opened about 12 000 years ago when the Dummer Moraine was deposited as a stagnant ice disintegration feature south of the Algonquin and Haliburton Highlands.Most radiocarbon dates (about 25) on marine shells, whale bone, and algae from Champlain Sea beach deposits are in the range of 10 000 – 11 800 years BP, indicating that the Champlain Sea episode is younger than glacial Lake Iroquois. However, a few Champlain Sea dates are older than 12 000 years BP and present an unresolved problem in geochronological correlation because they conflict with proposed deglaciation histories for southeastern Ontario.Late Wisconsin ice marginal positions are poorly known in southeastern Ontario and comprise another problem for further study.The end of glacial Lake Algonquin phase (the main drainage event in the North Bay area) probably occurred between 10 800 and 10 500 years BP, after the Champlain Sea had reached its maximum western limit in the Pembroke area (upper Ottawa River valley) as indicated by stratigraphic relationships of surficial deposits.
The position of the Grenville Front in eastern and central Labrador
Authors: Gower C. F. , Ryan A. B. , Bailey D. G. , Thomas A.
Published: April 2011

Positions suggested for the Grenville Front in eastern and central Labrador span a 100 km wide belt. The criteria used by previous workers are reviewed and the conclusion drawn that the various attempts to define the Grenville Front as a single line are not in agreement because different field or laboratory parameters have been employed.On the basis of recent mapping, a Grenville Front Zone is proposed. The northern boundary is considered to be the northern limit of widespread brittle deformation. The southern boundary is located along a series of geological contrasts, generally the northern limit of well-banded gneisses. In places, the Grenville Front Zone has been telescoped by thrusts or high-angle reverse faults.
Fluid inclusion evidence for the transport of tungsten by carbonate complexes in hydrothermal solutions
Authors: Higgins N. C.
Published: April 2011

Fluid inclusion evidence from the Grey River Tungsten Prospect, Newfoundland, and other tungsten deposits indicates that CO2 is an important component of the hydrothermal fluid. Carbon dioxide is enriched in fluids evolved from granitic melts under high fluid pressure, while lower pressure fluids are chloride-rich. The association of tungsten deposits with these carbon dioxide rich hydrothermal fluids suggests that carbonate/bicarbonate complexes may be important in tungsten transport at very high fluid pressures.
Comparisons of magnetic anomalies of lithospheric origin measured by satellite and airborne magnetometers over western Canada
Authors: Langel R. A. , Coles R. L. , Mayhew M. A.
Published: April 2011

Crustal magnetic anomaly data from the Orbiting Geophysical Observatories 2, 4, and 6 (Pogo) satellites are compared with upward-continued aeromagnetic data between 50–85°N latitude and 220–260°E longitude. Agreement is good, both in anomaly location and in amplitude, giving confidence that it is possible to proceed with the derivation and interpretation of satellite anomaly maps in all parts of the globe. The data contain a magnetic high over the Alpha ridge suggesting continental composition and a magnetic low over the southern Canada basin and northern Canadian Arctic Islands (Sverdrup basin). The low in the Sverdrup basin corresponds to a region of high heat flow, suggesting a shallow Curie isotherm. A ridge of high field, with two distinct peaks in amplitude, is found over the northern portion of the platform deposits and a relative high is located in the central portion of the Churchill Province. No features are present to indicate a magnetic boundary between Slave and Bear Provinces, but a trend change is evident between Slave and Churchill Provinces. South of 60° latitude a broad magnetic low is located over very thick (40–50 km) crust, interpreted to be a region of low magnetization.
Multiple-stage hydrothermal alteration in porphyry copper systems in northern Turkey: the temporal interplay of potassic, propylitic, and phyllic fluids
Authors: Taylor R. P. , Fryer B. J.
Published: April 2011

The Bakircay and Ulutas Cu–Mo prospects represent the first occurrences of porphyry mineralization to be described in Turkey.Differences observed in the two prospects in terms of hydrothermal alteration (in particular, alteration overprinting), igneous textures, abundance of xenoliths, breccia phenomena, and style and intensity of fracturing may relate to different levels of exposure within a model porphyry system, Bakircay representing the deep root zone of such a system and Ulutas reflecting much higher levels close to the apex of such a system, or may simply reflect different levels of emplacement.The alteration assemblages present at the Bakircay prospect lend themselves to a geochemical study of the temporal variations in the hydrothermal fluids responsible for single- and multiple-stage alteration–mineralization. The chemical changes involved during single-stage potassic alteration are related to amphibole breakdown and the deposition of hydrothermal biotite (and chalcopyrite). These changes are manifested in light rare-earth element (LREE) enrichment and heavy rare-earth element (HREE) depletion reflecting the high K+ and Cl− activity of the hydrothermal fluids. During propylitic overprinting of potassic alteration changes in whole-rock geochemistry relate to the destruction of biotite (both igneous and hydrothermal) and the formation of chlorite, epidote, calcite, and apatite. These changes result in the loss of ail rare-earth elements (REE) due to increasing fluid/rock ratios and further changes within the HREE relating to zircon stability and the deposition of new mineral phases, e.g., epidote. Conversion of preexisting alteration types lo the quartz–sericite–pyrite ± rutile, calcite assemblages, typical of phyllic alteration, results in the loss of all elements not accommodated in these phases. The high fluid/rock ratios and low pH of the fluids cause progressive leaching of all REE, particularly the lightest (La and Ce).
L'alcalinité totale comme indicateur de mélange dans un milieu estuarien
Authors: Pelletier E. , Lebel J.
Published: April 2011

This paper proposes the use of total alkalinity as a mixing index at the mouth of Saguenay fjord on the St. Lawrence estuary. The large difference in the total alkalinity between the fresh waters from the St. Lawrence River (1.475 meq/kg) and those from the Saguenay River (0.134 meq/kg) allows us to define and calculate a dilution factor relative to total alkalinity (δAt), which is very sensitive to the presence of the fjord marine water in the estuarine mixing area both at the surface and at depth. The authors show the advantage of use of the dilution factor (δAT) in comparison to some other classical oceanographic parameters such as temperature, salinity, density, and dissolved oxygen.
Wenlockian graptolite reference section, Clearwater Creek, Nahanni National Park, Northwest Territories, Canada
Authors: Lenz A. C.
Published: April 2011

A sequence of 20 m of Wenlockian graptolite-bearing strata is described from southern Northwest Territories. The sequence is relatively rich in graptolites and represents the best Wenlockian graptolite interval yet known in the Canadian Cordillera, even though the fauna is notably lacking in many of the typical Wenlockian species. The following Wenlockian biostratigraphic units are recognized (from oldest to youngest): centrifugus Zone, "Beds with C. cf. perneri", rigidus Zone, "Beds with Monograptus firmus nahanniensis", testis-lundgreni Zone, and "Beds with Pristiograptus etheringtoni".Graptolites described in this study comprise Monograptus antennularius, M. firmus nahanniensis n. subsp., M. flemingii, Pristiograptus sardous, P. etheringtoni n. sp., Monoclimacis flumendosae, Cyrtograptus centrifugus, C. cf. hamatus, C. cf. perneri, and C. rigidus from Wenlockian strata, as well as the first report from outside China of the late Llandoverian genus Sinodiversograptus.
Pleistocene marine kettle-fill deposits near Ottawa, Canada
Authors: Hayward M. , French H. M.
Published: April 2011

Exposures at several localities in the Ottawa region reveal Champlain Sea deposits filling depressions on what were formerly submerged surfaces of Wisconsin sand and gravel ridges. The deposits, referred to as "kettle fill," constitute materials eroded from the ridges in a marine environment and redeposited in ice-melt depressions or kettle holes. Processes responsible for the deposition of the sediment appear to include debris flows and small turbidity currents initiated by wave washing and slope instability. The dimensions of the depressions, their depth in relation to the falling wave base, and the steepness of the flanks were important factors controlling sedimentation. The kettle-fill facies comprise diamicton (pebbly mud), gravel, sand, and lutite.
Archeomagnetism of a 19th century pottery kiln near Jordan, Ontario
Authors: Dunlop David J. , Zinn Murray B.
Published: April 2011

The Jordan pottery kiln near St. Catharines, Ontario, was last fired about 1840–1841. Bricks from the kiln floor have intense NRM's (natural remanent magnetizations) in the range 0.2 × 10−2 to 3.7 × 10−2 emu cm−3 which are directionally stable against alternating field (AF) demagnetization to 1000 Oe (7.96 × 104 A/m). Of 31 specimens tested by the modified Thellier double-heating method, 27 yielded reliable paleofield intensities averaging 1.166 ± 0.092 times the present field intensity. Natural remanent magnetization directions are "streaked" in inclination and shallower than expected. Their average, D = 359.4°, I = 71.3 °(α95 = 2.2°, k = 310, N = 15 samples), differs significantly from both 1845 and 1979 fields in the area. Upon thermal demagnetization to 520 or 540 °C, streaking disappears and remanence vectors systematically steepen. The thermally cleaned mean direction, D = 357.8°, I = 73.7 °(α95 = 1.5°, k = 635, N = 15 samples), is indistinguishable at the 95% confidence level from the 1845 field, but differs significantly from the 1979 field.Part of the "inclination error" and streaking of NRM directions could result from fabric anisotropy or tilting of the bricks, but the greater part probably results from shape anisotropy of the strongly magnetic kiln floor, which deflects the internal field away from the external field and into the plane of the floor during cooling. The internal field is also weaker than the external field as a result of this self-demagnetization. The stronger the NRM, the greater the inclination error and the weaker the apparent paleofield intensity recorded. Thus, high-blocking-temperature fractions of NRM should record a less magnetically refracted (i.e., a steeper) paleofield, as observed. Also observed is approximate correlation between the spatial variation of NRM intensity in the kiln floor and variations in inclination and apparent paleointensity. The shape anisotropy of strongly magnetized horizontal sheets is a probable source of shallow inclinations, scattered directions, and weak apparent paleointensities in many submarine lavas sampled by the Deep Sea Drilling Project.
Geothermal measurements in Newfoundland
Authors: Wright J. A. , Jessop A. M. , Judge A. S. , Lewis T. J.
Published: April 2011

We report heat flow values for ten holes at five sites in Newfoundland. The average observed heat flow is 43 ± 4 mW m−2. Corrected for Pleistocene surface temperature variations, the average becomes 50 ± 4 mW m−2, with a range from 38–82 mW m−2. The Dunnage zone (a vestige of the Iapetus Ocean) exhibits a heat flow lower than normal for Paleozoic orogenic belts. The highest heat flow is associated with the Carboniferous St. Lawrence granite intrusion. Heat production measurements were made at three of the sites. Those in the Dunnage zone are low (< 0.8 μW m−3), as expected for former oceanic rocks, while that for the St. Lawrence granite is high (4.9 μW m−3). A plot of heat flow versus heat production for these data and the data of Hyndman et al. for the Maritime Provinces demonstrates that Newfoundland belongs to the same heat flow province as the Maritimes and the eastern United States. The reduced heat flow for the Canadian Atlantic Provinces data is 32 ± 3 mW m−2, uncorrected, and 40 ± 3 mW m−2 when corrected for Pleistocene temperature effects. Computed geotherms for heat flows and heat productions corresponding to the upper and lower observed limits of the data yield temperatures at 30 km depth of about 575 and 475 °C respectively.
Anastomosed river deposits: modern and ancient examples in Alberta, Canada
Authors: Smith Derald G. , Putnam Peter E.
Published: April 2011

The anastomosed fluvial system is proposed as an environment of deposition for some over-bank deposits, coal, and coarse channel sediments (sandstone and conglomerate) in the Rocky Mountain molasse (Mesozoic–Tertiary) of Alberta and British Columbia. The system consists of rapidly aggrading channels and adjacent wetlands, caused by a rising local base level downriver (i.e., alluvial fans) or basin subsidence. Multiple, multi-storied anastomosed channel deposits generally have low gradients, variable sinuosities, and low width/depth ratios.Anastomosed fluvial facies are similar to some river-dominated low energy deltaic facies; therefore, many of the deposits and facies geometries are similar. Similarity occurs because the fluvial processes and morphologies are similar. For example, as with lower deltaic plains, stable anastomosed channels are related to gentle gradients and high amounts of silt, clay, and vegetation in the banks. Channel stability subsequently accounts for a stable deposition environment favourable for the accumulation of organic material. Wetland environments cover the largest area (estimated 60–90%) of anastomosed systems, while channels, levees, and crevasse splays are minor in extent.Modern and ancient examples of anastomosis are described to provide a basic depositional framework. The lower reach (valley fill) of the modern Alexandra River in Banff Park is the modern example described. In east-central Alberta and southwest Saskatchewan, the hydrocarbon-bearing channel sandstones of the upper Mannville subgroup (Vigrass) are interpreted as an ancient (Lower Cretaceous) anastomosed system of very large scale (80 km × 300 km).We believe that the interpretation of environments of deposition in some ancient fluvial sequences of molasse deposits has been limited. This is due to the fact that anastomosed systems have only recently been understood as a unique fluvial style related to specific causal conditions. We suggest that the rapid subsidence along the western margin of the molasse foreland, coupled with high sediment loads from nearby mountain building (i.e., Rocky Mountains), would represent suitable conditions for anastomosis as well as graded meandering or aggrading braided fluvial styles. These same conditions would also apply to molasse deposition in intermontane basins.
The geochronology of some stratified metamorphic rocks in northeastern Massachusetts
Authors: Olszewski Jr. William J.
Published: April 2011

Analyses of U and Pb in zircons and Rb and Sr in whole rocks have been made on stratified metamorphic rocks in northeastern Massachusetts. The Rb–Sr results show an age of about 450 Ma, which is interpreted as a resetting age. This would indicate the major period of metamorphism in the area. Zircons from the Fishbrook Gneiss give an upper intercept age of 730 ± 26 Ma, which is interpreted as the age of volcanism that produced the Fishbrook Gneiss sequence. The upper intercept of the Westboro Formation detrital zircons is 1511 ± 22 Ma and is interpreted as the age of the source for the Westboro sediments. The lower intercepts of the Fishbrook (289 Ma) and the Westboro (278 Ma) zircons suggest an episodic Pb loss correlated with the thermal event in southeastern New England recognized by other methods. The intercept ages of the Shawsheen Gneiss (2042 and 517 Ma) are more difficult to interpret, but also suggest an old source area. This source area is tentatively suggested to be northwest Africa.
Les anomalies gravimétriques de la boucle du Niger. Leur signification dans le cadre de l'orogenèse panafricaine
Authors: Lesquer A. , Moussine-Pouchkine A.
Published: April 2011

The eastern margin of the west African craton along the Niger River in Mali is characterized by long wavelength, positive gravity anomalies. One of these anomalies, the Gourma anomaly, corresponds to the Gourma basin, a gulf of northeast–southwest subsidence, perpendicular to the Panafrican belt which presents all the characteristics of an aulacogen. The gravity anomalies show, under the upper Precambrian sediments, a thick layer of dense rocks, probably associated with pre-Panafrican rifting that occurred ca. 800–850 Ma ago along the eastern margin of the West African craton with a triple point in Mali.The extension of this structure inferred from Bouguer anomaly maps can be traced southward along more than 200 km north-northeast–south-southwest (Mopti anomaly). The gravity pattern shows that the shape of the subsiding basins is linked to preexisting fractures which have been rejuvenated during geological time. The subsidence, in part due to the weight of effusive and intrusive rocks, probably caused a downward deflection of the crust, explaining the negative anomalies that edge the Gourma and Mopti positive anomalies.
Structural and metamorphic relationships of pre-Fleur de Lys and Fleur de Lys rocks of the Baie Verte Peninsula, Newfoundland
Authors: Wit Maarten J. de
Published: April 2011

A variable assemblage of remobilized and recrystaltized granites and supracrustal rocks, formerly regarded as metasediments within the stratigraphic succession of the Eocambrian – Early Paleozoic western division of the Fleur de Lys Supergroup, have been recognized to constitute a basement to the Fleur de Lys metasediments. The basement rocks are exposed in (1} a central domal complex and (2) tectonic inliers within the Fleur de Lys metasediments (the cover) as modified isoclinal anticlines. Both the basement and the cover have undergone intense Lower Paleozoic deformation and lower-amphibolite faciès metamorphism.There is a marked petrographic distinction between rocks from the basement and those from the cover. Textures from the latter tend to conform with generally accepted equilibrium textures. Porphyroblastic habit of index minerals is a rule. In contrast, textures from the recrystallized basement rocks are of disequilibrium type, manifested by poikiloblasts and symplectites which have relatively large surface areas. Dendritic, myrmititic, and widmanstatten-like textures are common. Only where fully reconstituted to schists within zones of intense deformation do textures in the basement rocks resemble those in the cover.Tholeiitic dykes, that cut both cover and basement prior to the tectono-metamorphic events, have recrystallized to eclogite – garnet amphibolite assemblages in the basement. These also display the disequilibrium textures. In the cover, the dykes recrystallized to plagiociase amphibolites with equilibrium and porphyroblastic textures. From this it is argued that progressive metamorphism of the cover rocks and retrogressive metamorphism of the basement rocks occurred under similar P–T conditions and that the variable petrography of the basement and cover rock assemblages merely reflects different nucleation and growth kinetics related to relative "dry" and "wet" conditions respectively. The formation of textures within the "dry" basement was kinetically controlled and their morphologies are compatible with those formed by exsolution reaction mechanisms in alloys.
First regular archaeocyaths from the northern Appalachians, Forteau Formation, western Newfoundland
Authors: James Noel P. , Debrenne Françoise
Published: April 2011

Archaeocyaths of the class Regulares have been discovered in the Devils Cove Member of the Forteau Formation in eastern and southern parts of western Newfoundland. The three species recovered are the first Regulares reported from the northern Appalachians, all archaeocyaths from the bioherms and biostromes to the west and north in Newfoundland and Labrador are Irregulares. This sparse, but well-preserved fauna is similar to the poorly-preserved fauna from the central and southern Appalachians, as well as the abundant and diverse Regulares fauna from the Cordillera, but unlike contemporaneous asiatic and australoantarctic faunas, lending support to the view that late Lower Cambrian archaeocyaths in North America were endemic.
Mélange development in the Boones Point Complex, north-central Newfoundland
Authors: Nelson K. Douglas
Published: April 2011

The Boones Point Complex in north-central Newfoundland is a narrow mélange belt separating Roberts Arm terrain volcanic and volcaniclastic rocks to the north from Upper Ordovician westerly derived clastic rocks to the south and east. The mélange has a sedimentary matrix and contains a polymict assemblage of blocks. Limestone blocks have yielded Llanvirn–Llandeilo conodont faunas. Sedimentologic and structural analyses indicate that the complex is composed of subaqueous debris flow deposits, which are the proximal facies equivalent of the Late Ordovician clastics to the south. This debris flow material was tectonically deformed prior to the Medial Devonian 'Acadian' orogeny, probably as a result of earlier 'Taconic' thrusting.
Late Quaternary paleomagnetic record of the Goderich Basin, Lake Huron
Authors: Mothersill John S.
Published: April 2011

Paleomagnetic analysis of two cores taken of the Late Quaternary sequence of the Goderich Basin, Lake Huron, resulted in high resolution declination, inclination, intensity of magnetization (J), magnetic susceptibility (k), and Q-ratio (J/k) curves. There was a consistent, relative relationship of the features along the curves of all five parameters for both cores studied, which confirms the reproducibility of the method and suggests that paleomagnetic curves can be used for time-parallel correlation of the Late Quaternary sequence of the Goderich Basin.
Characteristics of residual and colluvial soils developed on granite and of the associated pre-Wisconsin landforms in north-central New Brunswick
Authors: Wang C. , Ross G. J. , Rees H. W.
Published: April 2011

An area in north-central New Brunswick of approximately 20 km2, where tors are common, was found to be undisrupted by glaciation. The soils in this area are developed on grus and appear to be of pre-Wisconsin age. In both residual Podzolic and colluvial Brunisolic soils, gibbsite was found to be present in significant amounts. The gibbsite content in the clay fraction of the residual soil increased with depth whereas the reverse occurred in the colluvial soil.The evidence indicates that gibbsite could have formed in a climate similar to the present one and that it is not stable in the present soil environment due presumably to the presence of organic matter.Except for the presence of gibbsite in the clay fraction, the characteristics of the residual soil are similar to those of soils of similar texture of late Wisconsin age from the same province.
Stress orientations from oil-well fractures in Alberta and Texas
Authors: Gough D. I. , Bell J. S.
Published: April 2011

Many oil wells in Alberta exhibit spalling of the walls (known as breakouts), which elongates the holes with the longer axis aligned northwest–southeast. This alignment is observed over an area in excess of 4 × 105 km2, in siltstones, sandstones, carbonate sediments, and one shale formation, through the stratigraphic column from Devonian to Cretaceous. It is unrelated to dip of the beds. We have elsewhere suggested that these breakouts are produced through stress concentration near the hole walls, in a stress field having large, unequal horizontal principal stresses and with the larger compression oriented northeast–southwest. It is probable that this northeast–southwest principal stress is σ1. This paper adds new data from oil wells in Alberta and northern British Columbia and shows that the breakouts, and by inference the stress orientations, are consistent through much of the western Canadian sedimentary basin. It also uses evidence from hydraulic fracturing in west-central Alberta and from steam-injection fracturing in eastern Alberta to support the view that σ1 is aligned northeast–southwest. The breakouts are consistent with either a thrust stress field or a strike–slip stress field, but the fractures formed by excess pressures in wells favour the latter. Recently Schafer has reported oil wells systematically elongated with a mean azimuth of N39°E in the Austin Chalk of southern Texas. We regard these elongations as formed by breakouts in a stress field with greater horizontal stress near N51°W, and this view is supported by overcoring measurements by Hooker and Johnson in granite of the Llano Uplift, 225 km from Schafer's wells, that reveal large horizontal compressions at the surface with the larger oriented N33°W.
Gravity and magnetic anomalies of the Sutton Mountains region, Quebec and Vermont: expressions of rift volcanics related to the opening of Iapetus
Authors: Kumarapeli P. S. , Goodacre A. K. , Thomas M. D.
Published: April 2011

Prominent, nearly coincident, positive gravity and magnetic anomalies occur in the Sutton Mountains region, centered about 100 km east of Montreal, Quebec. Several lines of evidence indicate that the gravity anomaly stems from two principal sources: a deep (mid and lower crustal) source of speculative origin and a shallow source identifiable with a narrow belt of late Precambrian – early Cambrian metavolcanic rocks, the Tibbit Hill volcanics. The magnetic anomaly seems to be produced mainly by the metavolcanic rocks. Three-dimensional modelling of a residual gravity anomaly, supplemented by two-dimensional modelling of the magnetic anomaly, shows that the seemingly minor belt of metavolcanic rocks constitutes the surface expression of a thick (maximum thickness ~8 km) pile of dominantly mafic volcanics, which are only slightly exposed at the present level of erosion.The Tibbit Hill volcanics are regarded as products of rift-related volcanism that occurred at an rrr triple junction developed during the early stages of the opening of the Iapetus Ocean. The Ottawa graben is probably the failed arm of this triple junction. The emplacement of the Grenville dike swarm whose trend is nearly coincident with that of the Ottawa graben was probably coeval with the volcanism in the Sutton Mountains region. The present work shows that the volcanism in the region was on a much larger scale than hitherto recognized.
First record of late Bajocian (Jurassic) ammonites in the Fernie Formation, Alberta
Authors: Hall R. L. , Stronach N. J.
Published: April 2011

An ammonite fauna near Frank, Alberta represents the first record of upper Bajocian strata in the Fernie Formation. The fauna consists of Megasphaeroceras cf. M. rotundum Imlay, Spiroceras cf. S. orbignyi Baugier and Sauzé, and fragmentary stephanoceratids and is correlated with the zone of Megasphaeroceras rotundum (Subfurcatum standard zone; early late Bajocian), which is also known in southern Alaska, eastern Oregon, western interior U.S.A., central Peru, and the Andes of Chile and Argentina. A fragment of Leptosphinctes cf. L. talkeetnanus (Imlay), which is latest Bajocian to early Bathonian in age, occurs 21 m above the Megasphaeroceras rotundum fauna.
A comparison of mineral grain fabrics and finite strain in amphibolites from eastern Finland
Authors: Gapais Denis , Brun Jean-Pierre
Published: April 2011

Fabrics in amphibolite rocks from the Kuopio area (eastern Finland) are described and compared with results of finite strain analysis. The area consists of mantled gneiss domes, which are deep-seated diapiric structures. Results concern the cover rocks of the domes. Strain ellipsoids range in shape from prolate to oblate (−0.67 ≤ v ≤ 0.52). Strain intensities vary strongly [Formula: see text].Preferred orientations of hornblende have been measured by X-ray texture goniometry and corresponding fabric ellipsoids calculated using an eigenvalue method. The same has been done for biotite where present. Fabric ellipsoids obtained for biotite are all oblate (0.04 ≤ vf ≤ 0.76). Those obtained for hornblende range from prolate to oblate (−0.60 ≤ vf ≤ 0.73). Intensities of hornblende fabric [Formula: see text] are weaker than those of biotite fabric [Formula: see text]. Local variations of results are induced by grain-scale factors, such as grain size, or original fabrics. No simple correlation is found between intensities of fabric and strain. In general, increasing strains are probably accompanied by an increase of the oblateness of biotite fabric ellipsoids. Hornblende fabrics are found to give a good approximation of the prolateness of the finite strain ellipsoid. The resulting L–S tectonite pattern is consistent with the general strain pattern and with the development of domal structures in the Kuopio area.
The structural geometry and geological history of Archean rocks at Kenora, north-western Ontario—a proposed type area for the Kenoran Orogeny
Authors: Gower Charles F. , Clifford Paul M.
Published: April 2011

The Kenora area, at the south margin of the English River Subprovince, consists of polydeformed gneisses intruded by granitoid plutons, some of which are also deformed. The gneisses are mainly tonalites of igneous origin, but contain remnants of an earlier, dominantly mafic, supracrustal sequence and severely deformed pegmatites.Within the gneissosity are intrafolial F1 folds subsequently refolded by tight-to-open F2 folds. Major F2 folds can be delineated from the geometry and distribution of minor F2 structures. During deformation the area was subjected to upper amphibolite facies metamorphism (650–750 °C, 4–7 kbar (400–700 MPa)) with K-feldspar megacrysts and garnet developed in the deeper levels. Major F2 folds are refolded in a rim synform (F3), which developed synchronously with the emplacement of the Dalles granodiorite, an event that also created a plunge culmination uplifting part of the deeper K-feldspar megacryst – garnet structural level. Cumulative apparent dextral displacement of 6 km in two periods of movement, related partly to the emplacement of the Dalles granodiorite, is suggested for a major fault 1.5 km north of, and parallel to, the English River – Wabigoon Subprovince interface. Open, upright F4 folds caused buckling of dioritic dikes and pegmatites. Later deformation involved minor faulting and joint development.Rb–Sr isotopic studies indicate that this geological history took place within about 150 Ma with most activity over by 2600 Ma. It is proposed that this should be selected as the type area for the Kenoran Orogeny.
Age and origin of the Dover Fault: tectonic boundary between the Gander and Avalon Zones of the northeastern Newfoundland Appalachians
Authors: Dallmeyer R. D. , Blackwood R. F. , Odom L.
Published: April 2011

The Dover Fault forms a tectonic boundary between northern portions of the Gander and Avalon Zones of the Newfoundland Appalachians. A systematic geochronological investigation across the mylonitic fault zone has been carried out to clarify the origin and history of tectonic activity along this important Appalachian structure.Zircon fractions from the mylonitic Lockers Bay Granite (Gander Zone) record individually discordant U–Pb dates, but yield a well-defined upper concordia intercept age of 460 ± 20 Ma. Hornblende (1 sample) and biotite (11 samples) from variably mylonitic Gander Zone lithologies (plutonic and metamorphic) adjacent to the fault zone record undisturbed 40Ar/39Ar age spectra with plateau ages of 395 and 365–383 Ma, respectively. Together with field and petrographic characteristics, the new geochronologic data suggest that the Lockers Bay Granite originated as an anatectic melt during high-grade regional metamorphism of the country rock terrane at approximately 460 Ma. The crystal-rich magma was subsequently emplaced into its present position thereby producing local discordance with small-scale structures in host gneisses.Following its emplacement, the Lockers Bay Granite and country rock terrane were maintained at elevated postmetamorphic temperatures for a prolonged interval until they underwent rapid strain during Acadian (Devonian) juxtaposing of the northern Gander and Avalon Zones along the Dover Fault. Sudden Acadian uplift along the fault is suggested because of the rapid cooling of the northern Gander Zone through temperatures required for argon retention in hornblende and biotite. Post-mylonite brecciation may have locally affected argon isotopic systems of phyllitic lithologies adjacent to the fault zone in the study area.
Petrology and geochemistry of the Kamloops Group volcanics, British Columbia
Authors: Ewing Thomas E.
Published: April 2011

The Kamloops Group is an alkali-rich calc-alkaline volcanic suite of Early to Middle Eocene age, widespread in south-central British Columbia. Rock types in the suite range from high-K basalt through andesite to rhyolite. The suite is characterized by relatively high K2O, Sr, and Ba, but low Zr, Ti, and Ni concentrations, only moderate Ce enrichment, and little or no Fe enrichment. Initial ratios 87Sr/86Sr are about 0.7040 in the western half, and about 0.7060 in the eastern half of the study area. No difference in chemistry or mineralogy marks this sharp transition. Chemically similar suites include the Absaroka–Gallatin suite in Wyoming and the lower San Juan (Summer Coon) suite in Colorado. The content of K2O at 60% SiO2 increases regularly eastward across southern British Columbia. The chemical data support the subduction-related continental arc origin of the Kamloops Group volcanics.The volcanic rocks consist in the main of augite–pigeonite andesites ranging from 52 to 62% silica, with subordinate quantities of olivine–augite–pigeonite basalt and biotite rhyodacite and rhyolite. The andesites and basalts were derived by a combination of low-pressure fractional crystallization, higher pressure fractional crystallization, and variable parental magmas, whereas low-pressure fractional crystallization of plagioclase, biotite, and apatite from parental basalt and andesite produced the rhyolites. The parental magmas were basalts and basaltic andesites with high K, Sr, and Ba. The primary source of these magmas is inferred to have been an alkali-enriched hydrous peridotite with neither plagioclase nor garnet present in the residuum.
Ostracodes and paleoenvironments of the late Quaternary Don and Scarborough Formations, Toronto, Ontario
Authors: Poplawski S. , Karrow P. F.
Published: April 2011

Type section exposures at the Don Valley brickyard and Scarborough Bluffs were studied for ostracode occurrences. In all, 12 species were identified from the Don Formation, with Candona rawsoni and Candona caudata being most abundant. A deltaic environment, with a mixture of fluvial and lacustrine species, is indicated at the brickyard, whereas a more dominantly lacrustrine environment, with fewer ostracode species, is evident at the bluffs. Climatic indications are consistent with those of other fossil groups in suggesting conditions rather like the present.The Scarborough Formation has yielded only four species of ostracodes, with Candona caudata the most abundant. A much colder lacustrine environment is indicated for the Scarborough than for the Don Formation.
Crustal structure, seismic stratigraphy, and rift processes of the continental margin off eastern Canada: ocean bottom seismic refraction results off Nova Scotia
Authors: Keen C. E. , Cordsen A.
Published: April 2011

Two crustal seismic refraction profiles were obtained on the continental margin of eastern Canada. These lines were located on the upper continental rise and on the outer continental shelf off Nova Scotia. A large air gun and explosive charges provided the sound sources, and ocean bottom seismometers were used to receive the signals. The travel time data were analyzed using the tau–p extremal inversion method and ray tracing techniques. This analysis allowed velocity–depth models to be constructed that included low-velocity zones and velocity gradients, as well as abrupt velocity contrasts at layer interfaces.The results show that about 7 km of sediments lies beneath the upper continental rise, beneath which oceanic layers 2 and 3 have been identified. Layer interfaces at depths of 0.39, 1.79, and 2.80 km below the sea floor correspond to strong, regional seismic reflectors, perhaps correlative with horizons Au, A*, and β. The top of oceanic layer 2 is associated with a velocity of 5.3 km s−1 and there is no difficulty in distinguishing between basement and high-velocity sediments in this region.The crust beneath the outer shelf includes 9–16 km of sediments. A layer with compressional wave velocity of 6.3 km s−1 constitutes the main crustal layer, below which the mantle is estimated to lie at total depths of 26–30 km. Within the sediments the velocity–depth model for the upper 5 km agrees well with sonic log velocities measured in deep wells. A seismic stratigraphy for the sediments can be deduced by comparing the refraction result with sonic log velocities and with the regional stratigraphy. The total thickness of the mid-Jurassic and older sediments, not sampled in the wells, is at least 4.5 km. The total thickness of crustal rocks of pre-rift age is between 14 and 21 km, which is significantly thinner than the 35–38 km values measured beneath mainland Nova Scotia in earlier studies. Both the thin crust and the high rate of subsidence during the Early Jurassic are consistent with extention of the lithosphere during initial rifting of this margin in Late Triassic time.
Upper Permian and Lower Triassic palynomorphs from eastern Yunnan, China
Authors: Shu Ouyang
Published: April 2011

In eastern Yunnan the Upper Permian Lungtan and Changhsing Formations and the Lower Triassic Kayitou Formation each contain a characteristic assemblage of spores and pollen.The Torispora gigantea – Patellisporites meishanensis assemblage in the Lungtan Formation contains abundant pteridophyte and pteridosperm spores and few gymnosperm pollen. Some genera are known from the Carboniferous and Lower Permian of Europe but most are Cathaysian. The Yunnanospora radiata – Gardenasporites assemblage in the Changhsing Formation has a Paleozoic aspect but characteristic Mesozoic genera and species occur. The Lundbladispora–Aratrisporites–Pteruchipollenites assemblage in the Kayitou Formation contains numerous pteridophyte and pteriodosperm spores and gymnosperm pollen; some Paleozoic genera occur (Crassispora, Lycospora?, Stellisporites, Thymospora, Torispora, Triparites, Triquitrites, and Waltzispora), but Mesozoic genera predominate. Thirty metres above the base of the Kayitou Formation gymnosperm pollen, especially that of conifers, becomes dominant.It is suggested that the Carboniferous and Lower Permian species in the Changhsing Formation and the Paleozoic genera in the Kayitou Formation are not reworked but are indigenous and that the composition of the resulting microflora reflects the parent flora. The presence of this microflora in Lower Triassic rocks suggests that, at least locally, sedimentation was essentially continuous across the Permian–Triassic boundary.
Isograds and mineral assemblages in the eastern axial zone, Montagne Noire (France): implications for temperature gradients and P–T history
Authors: Thompson Peter H. , Bard Jean-Pierre
Published: April 2011

Detailed petrography across a metapelitic sequence in the eastern axial zone of the Montagne Noire, France, is the basis for a sequence of isograds marking the first appearance of biotite–cordierite, staurolite, andalusite, and sillimanite. The juxtaposition of low-grade biotite-free rocks against medium-grade rocks at the gently dipping biotite–cordierite isograd is attributed to tectonic telescoping of the metamorphic sequence. Study of mineral assemblages with respect to an AFM reaction sequence indicates the staurolite isograd is related to changes in rock composition, and complex assemblages in the sillimanite zone may be the result of unstable persistence of minerals formed when metamorphic grade was lower. These assemblages are interpreted to contain a record of part of the P–T history during which pressure decreased as temperature increased. P–T profiles show that temperature gradients of 200–300 °C/km suggested by previous workers are not required to explain the isograd pattern; gradients of 37 °C/km or less are sufficient.
Skeletal and dermal armor reconstruction of Euoplocephalus tutus (Ornithischia: Ankylosauridae) from the Late Cretaceous Oldman Formation of Alberta
Authors: Carpenter Kenneth
Published: April 2011

Previously life reconstructions of ankylosaurid dinosaurs are incorrect in that they show uniformly shaped keeled plates arranged in neat longitudinal and transverse rows, and large spines projecting laterally from the flanks of the body. Articulated armor of Euoplocephalus tutus (previously described as the types "Scolosaurus cutleri" Nopsca and "Dyoplosaurus acutosquameus" Parks) from the Late Cretaceous Oldman Formation shows that armor shape and size varied considerably along neck, back, and tail. An attempt is made to reconstruct the skeleton and arrangement of the dermal armor of Euoplocephalus.
Pollen distribution in recent marine sediments, eastern Canada
Authors: Mudie P. J.
Published: April 2011

Analysis of 90 samples from coastal and continental shelf areas off eastern Canada between 42 and 69°N shows that Quaternary pollen and spores are present in recent marine muds throughout this region. Pollen and spore concentrations range from 50 000 to 100 grains per cm3 and they decrease both offshore as a function of distance from vegetation sources and northwards as a function of lower vegetation density north of the summer Arctic Frontal Zone. Isopercentage contours show that maximum relative abundances of most palynomorphs occur in marine sediments adjacent to their regions of highest vegetation representation onshore. However, Pinus and Picea pollen tend to increase in percentage abundance with distance offshore. Presence of these tree pollen in marine sediments off Baffin Island implies that wind transport is an important pathway by which bisaccate pollen types enter the ocean, in addition to fluvial transport.Q-mode factor analysis shows that four major factors account for 89% of the variance among the marine palynomorph samples, while two other factors (6% of the variance) apparently reflect selective transport of Pinus pollen or local over-representation of Gramineae. The major factor assemblages are: (1) Boreal Forest Assemblage, with high weightings of Picea and maximum loadings adjacent to the boreal forest, 48–54°N; (2) Arctic Assemblage, weighted by Rosaceae, Gramineae, and Cyperaceae, with maximum loadings off Baffin Island, 60–69°N; (3) Mixed Forest Assemblage, weighted by Betula tree pollen, Picea glauca, Pinus strobus, Tsuga, and temperate trees (e.g., Quercus, Acer), with maximum loadings in the southeast, 42–48°N; (4) Subarctic Assemblage, with high weightings of Sphagnum, Alnus, and Lycopodium, and maximum loadings adjacent to forest–tundra and low arctic tundra, 54–60°N. These regional marine pollen assemblages are empirically related to contemporary climatic parameters, thus indicating the potential value of pollen analysis for direct correlation between Quaternary paleoclimatic records onshore and in marine areas bordering eastern Canada.
Fractures and fracture infillings of the Eye–Dashwa Lakes pluton, Atikokan, Ontario
Authors: Stone Denver , Kamineni D. Choudari
Published: April 2011

Fractures in the Eye–Dashwa pluton near Atikokan, Ontario can be subdivided on the basis of their filling materials. These materials include aplite, epidote, chlorite, and gypsum–carbonate–clay, listed in order of decreasing age established from crosscutting relations. Textures indicate that infilling occurred during fracture growth. Continuous cooling of the pluton during fracturing is inferred from the expected crystallization temperatures of fillings. Fracturing began before the pluton was completely solidified (650–600 °C) and continued to temperatures below 100 °C. Many fractures appear to have been sealed by the filling materials after initiation but were subsequently sheared and filled by lower temperature materials. Apparently the majority of fractures formed during or immediately after pluton solidification and new fractures became smaller and more restricted in location as cooling progressed. Fractures and filling materials are seen as important features in assessing the possibility of movement of radionuclides in aqueous solutions away from a nuclear fuel waste repository.