bluuebunny/crossref_metadata_2025 huggingface dataset:
Metallogeny and tectonics of porphyry copper–molybdenum deposits in British Columbia
Authors: Griffiths John R. , Godwin Colin I.
Published: April 2011

Metallogenic studies in British Columbia are based on data for over 1200 deposits that include metals and ore minerals recorded, age and lithology of sedimentary and volcanic host rocks, and the nature of any related granitoid intrusions. Analysis of these data defines a bimodal source of metals in porphyry deposits. Cu and Mo are derived from the primary granitoid melt, and the Cu/Mo ratio reflects the composition of that melt. Pb, Zn, Ag, and Au occur in veins peripheral to porphyry intrusions, and the metal content of these veins is controlled by the lithology of their wall rocks.Petrogenetic constraints imply that granitoids are predominantly anatectic crustal melts; thus we use the distribution of porphyries with varying metal ratios to define a map of the lower crust, which then constrains a tectonic model. Two major volcanic–plutonic arcs (Coastal: Jurassic – early Tertiary; Takla: Triassic) were generated above two subduction zones. Anatexis of the associated underplates produced Cu porphyries. The Cu–Mo porphyries of the Intermontane Belt were produced by anatexis of mixed volcanic, volcaniclastic, and clastic sedimentary rocks deposited on a fragment of oceanic crust trapped between the two magmatic arcs in the Jurassic.
Geochronology of the porphyry copper deposits and related mineralization of Mexico
Authors: Damon Paul E. , Shafiqullah Muhammad , Clark Kenneth F.
Published: April 2011

K–Ar dating demonstrates that all but eight of 41 dated porphyry copper and related ore deposits of Mexico were emplaced during the Laramide episode of maximum plate convergence. One older deposit is related to the Jurassic volcanic arc of western North America, one is pre-Laramide Cretaceous, four are Oligocene in age, and two late Cenozoic deposits are within the modern trans-Mexican–Chiapenecan volcanic arc. Thirty-three of the deposits lie within a long narrow belt that continues into Arizona and New Mexico, and widens from 100 km to over 300 km in the region of maximum extension in the southern Basin and Range Province. Eighty-five percent of the deposits were emplaced during the eastward transgression of the Cordilleran volcanic arc in middle Cretaceous through Eocene time.The occurrence of the porphyry copper deposits of Mexico appears to be independent of the terrane intruded and the copper content of the wall rocks where the wall rocks predate the volcanic arc, which is syngenetic with the porphyry stock. However, strontium is significantly more radiogenic where the host porphyry has intruded terrane having a Precambrian crystalline basement. Most frequently, the porphyry pluton can be observed to have intruded penecontemporaneous volcanic rocks or the batholith itself. The porphyries appear to be apophyses of the batholiths. The relationships suggest that the ore components are contained within the calc-alkaline batholiths and concentrated in the subvolcanic porphyries and wall rocks during transport of hydrothermal fluids to the volcanic orifice.The shape of the Cordilleran copper belt is controlled by magma composition, existence of a protective capping of dominantly volcanic rock, uplift, time, and erosion. As the continental volcanic arc that produced the porphyry copper deposits progressed eastward, the associated magma became more alkalic and copper poor. Thus, enrichment to ore grade became increasingly improbable to the east. Uplift and ample time for erosion prior to the return of the continental volcanic arc reduced the probability of ore preservation to the west. Optimum conditions for preservation were present within the belt where burial of calc-alkalic porphyry plutons under a thick volcanic cover occurred before removal of the ore zone by erosion. The broader width of the porphyry belt to the north is probably the result of both more extensive basin-and-range extension and basin-and-range taphrogeny that exposed some of the porphyries to relatively recent denudation and consequently made them available for economic exploitation.
Studies of burial metamorphism in the post-Taconic stage of the Appalachian orogen, southwestern Gaspé
Authors: Duba Daria , Williams-Jones Anthony E.
Published: April 2011

Illite crystallinity and organic matter reflectance techniques are applied to the evaluation of burial metamorphic conditions for lithostratigraphic groups accumulated during the post-Taconic stage of the Appalachian orogen in the southwestern Gaspé. The results of this work show that the metamorphic grade of the Paleozoic succession decreases upwards but is anomalously high in the youngest Fortin Group. A model is proposed in which the two parts of the succession were separately buried. The model envisages the lower part (Honorat, Matapedia, and Restigouche groups) being uplifted in the south whilst deposition of the Fortin Group continued in the north in a basin yoked by the Matapedia Fault. Burial is interpreted to have occurred under an average oceanic geothermal gradient in the early Paleozoic basin and under a high geothermal gradient in the Fortin basin.
Remote acoustic classification of marine sediments with application to offshore Newfoundland
Authors: Cochrane N. A. , Dunsiger A. D.
Published: April 2011

Shallow marine sediments can be remotely classified by the spatial correlation properties of their seismic reflection signatures provided one uses a highly repetitive broadband acoustic source. A classification scheme defined by three spatial coherence parameters is shown capable of automatically differentiating between several formations of unconsolidated sediments in a limited area of offshore Newfoundland. The consistency and generality of the technique are explored and comparisons with standard echogram interpretation are made.
Four Pleistocene formations in southwest British Columbia: their implications for patterns of sedimentation of possible Sangamonian to early Wisconsinan age
Authors: Hicock Stephen R. , Armstrong John E.
Published: April 2011

Semiahmoo and Dashwood drifts were deposited during the penultimate glaciation, and Highbury Sediments and Muir Point Formation during the last interglacial. These sediments are defined and described, and stratotypes are established for them.Based on arboreal pollen assemblages, lithologic similarity, and relative stratigraphic position, Semiahmoo Drift of the Fraser Lowland is tentatively correlated with Dashwood Drift of Vancouver Island. Stone provenance, till fabrics, glaciotectonic structures, cross-bedding, and stone imbrication indicate that regional ice and meltwater flowed out of major fiords in the Coast Mountains and into the ancestral Strait of Georgia during the penultimate glaciation. Ice flowed southeastward against the east coast of Vancouver Island, and down the axis of the strait. Pollen and molluscs in Semiahmoo and Dashwood fossiliferous muds give evidence of transition from glaciomarine to marine conditions at the close of the penultimate glaciation.Highbury Sediments of the Fraser Lowland perhaps correlate with the Muir Point Formation of Vancouver Island, based on lithologic similarity and relative stratigraphic position. Stone provenance and paleocurrent data indicate that stream flow during the last interglacial issued from nearby mountains and onto coastal floodplains that shelved into the ancestral Strait of Georgia and Juan de Fuca Strait. Abundant Pseudotsuga and Tsuga heterophylla pollen indicate that climate during that time was at least as warm as the present.
The geology of the New Insco copper deposit, Noranda district, Quebec
Authors: Meyers R. E. , MacLean W. H.
Published: April 2011

The New Insco copper deposit is an Archean volcanogenic massive sulfide orebody situated on the northwestern edge of the Noranda mining district, in the Superior Province of the Canadian Shield. The ore occurs near the base of a thin unit of pillowed and brecciated basalt that overlies rhyolitic volcaniclastic rocks. Both the basalt and rhyolite are heavily chloritized and sericitized and form a zone of alteration that is depleted in SiO2, Na2O, and CaO and enriched in FeOT, MgO, K2O, Cu, Zn, and S. The units are separated from an underlying massive rhyolite by a diorite intrusion and from an overlying series of pillowed basalts by a fault.The orebody is a pyrrhotite-rich lens of massive sulfide, containing conformable bands of disseminated chalcopyrite and pyrite, that is interlayered with lenses of pyrite–chalcopyrite-bearing siliceous ore. The massive ore is interpreted to have been deposited in a distal environment with pyrrhotite as a primary mineral. It was recrystallized during regional metamorphism, which imparted a polygonal–granular texture to the pyrrhotite and formed overgrowths on pyrite crystals. Following Pleistocene glaciation, pyrrhotite was extensively replaced by pyrite, marcasite, iron oxides, carbonates, and hydroxides.
Evolution of the south-central segment of the Archean Abitibi Belt, Quebec. Part II: Tectonic evolution and geomechanical model
Authors: Dimroth Erich , Imreh Lazlo , Goulet Normand , Rocheleau Michel
Published: April 2011

In this paper, we describe the relations between the paleogeographic and tectonic evolution of the southwestern part of the Archean Abitibi and Bellecombe belts. Volcanism in the Abitibi Belt created a very thick, anisotropic plate composed of competent volcanic rocks and broken by the Duparquet–Destor break. The depocenters of the upper division of diverse volcanic rocks subsided about 10 km relative to their surroundings, and some central volcanic complexes within this division were consolidated by synvolcanic plutons and their thermal metamorphic aureole. The Cadillac break, a normal fault, separated the Abitibi and Bellecombe belts. The latter consisted of comparatively incompetent sedimentary rocks on top of a basement composed of ultramafic–mafic flows.North–south compression of the volcanic terrain during the Kenoran Orogeny produced a set of flexure folds, F1, that curve around the consolidated cores of central volcanic complexes generally in an easterly direction. Synclinoria nucleated at the deeply subsident depocenters of the upper diverse division. Further north–south flattening and subvertical stretching produced the east-trending F2 folds, their axial-plane schistosity S2, and local superposed schistosities S3 and S4. Southward verging recumbent folds suggest that the Bellecombe Belt simultaneously was pulled northward below the Abitibi Belt. During the orogeny, the Duparquet–Destor and Cadillac breaks were transformed to thrust faults; the Duparquet–Destor break also shows minor (< 3 km) right-lateral strike slip. Diapiric rise of late- to post-kinematic plutons locally distorted earlier schistosities.
Evolution of the south-central segment of the Archean Abitibi Belt, Quebec. Part III: Plutonic and metamorphic evolution and geotectonic model
Authors: Dimroth Erich , Imreh Laszlo , Goulet Normand , Rocheleau Michel
Published: April 2011

Textural criteria permit distinction between the pre-Kenoran and Kenoran phases of plutonism and metamorphism. The pre-Kenoran plutons and pre-Kenoran metamorphic phases are directly related to the volcanic evolution. Synvolcanic tonalite–trondhjemite plutons and swarms of mafic and felsic dykes core central volcanic complexes. The volcanic rocks underwent three types of pre-Kenoran metamorphism, namely, a pervasive alteration, a thermal contact metamorphism that affected narrow aureoles around synvolcanic plutons, and a high-intensity hydrothermal alteration that affected cross-cutting pipes in central volcanic complexes.Synkinematic Kenoran metamorphism resulted in the growth of minerals (chlorite, actinolite, etc.) parallel to schistosities. Synkinematic metamorphic grade ranges form the pumpellyite–prehnite facies to the amphibolite facies. Late- to post-kinematic metamorphic phases resulted in the growth of minerals across schistosities. Syn- to post-kinematic plutons are not voluminous in the part of the Abitibi Belt described here, but they underlie vast areas in the Bellecombe Belt. They range from gneissose early synkinematic plutons to late-kinematic plutons that have well preserved igneous textures.The paleogeographic, tectonic, plutonic, and metamorphic histories of the Abitibi and Bellecombe belts are reviewed and we conclude that the belts are analogous to an island arc – fore-arc basin system.
Paleomagnetism of Late Proterozoic rocks, Victoria Island, Northwest Territories, Canada
Authors: Palmer H. C. , Baragar W. R. A. , Fortier M. , Foster J. H.
Published: April 2011

Late Proterozoic Natkusiak plateau basalts and associated dolerite dikes and sills of Victoria Island show paleomagnetic polarities that relate them to the Franklin diabases but are complicated by the effects of a downward component that cannot be wholly removed in all sites by AF and thermal demagnetization. In a preserved thickness of about 740 m of Natkusiak flows the polarity changes upward in roughly successive thirds of the section from east and slightly downward (reverse), to west and slightly downward (normal), to east and slightly upward (reverse). Thus there is a double reversal in the section but the lower reverse direction is badly contaminated by a downward directed overprint. At three sites this steep downward component persists after cleaning. Dolerite polarities, except for one that is normal, cluster in the east-down (reverse) direction close to the lower reverse direction of the lavas and steeply downward, similar to the overprint direction in the flows. The downward component can be correlated with evidence of low initial oxidation and more severe alteration in the corresponding samples and may be related to burial metamorphism. The reverse direction of the upper lavas, being from the freshest parts of the section and closest in direction to the exact reversals recorded in Franklin dikes from Baffin Island, is believed to be most reliable. Paleopole positions are: upper reverse lavas, 161°E, 2°N; middle normal lavas, 159°E, 9°N; combined middle–upper lavas, 159°E, 6°N (δp = 4°, δm = 8°).Reynolds Point shales from the Shaler Group underlying Natkusiak basalts and host to the dolerite sills yielded a paleopole position at 147°E, 6°S, significantly removed from the Franklin poles but probably not indicative of an age greater than Hadrynian.
Isotopic composition of lead from a paleo-island arc: Shasta, California
Authors: Slawson W. F.
Published: April 2011

Twelve new lead isotope analyses of samples from the West and East Shasta districts, California are presented. The measured isotopic ratios 206Pb/204Pb versus 207Pb/204Pb exhibit a good linear trend with a slope of 0.1794 ± 0.0066. Arguments are presented that the two-stage ages calculated from this slope are not real events. It is suggested the linear array is due to fortuitous addition of contaminants to the volcanogenic mineralizations. Thus common lead isotopes are possibly better geochemical tracers than they are geochronometers. This may be particularly true in cases where the total lead content is low.
Palynologie et morphogenèse récente dans le bassin du Grizzly Creek (Territoire du Yukon)
Authors: Bourgeois J. C. , Geurts M.-A.
Published: April 2011

Pollen analysis of three sections from the Grizzly Creek basin, Yukon Territory was undertaken in order to reconstruct the paleoecology of the region over the last two millennia.Diagrams for two sites show three well defined pollen zones, whose boundaries are based on fluctuation of pollen spectra. The oldest zone corresponds to vegetation comparable to that of the present and a climate similar to or a little colder than the present climate. In zone 2, the strong decline of Picea is interpreted as a break in pollen production caused by a decrease in precipitation and a warming of the climate. The forest survived for several centuries in a state of degeneration, which favoured the development of a stratum of shrubs and herbaceous plants. Zone 3 reflects a return to vegetation and to climatic conditions similar to those of zone 1.The positions of two layers of volcanic ash, dated at approximately 1230 and 1890 years BP and corresponding to two lobes of White River Ash, indicate the rhythm of sedimentation. The presence of loess in the sediments helps explain the great accumulation of sediment before 1250 years BP and supports an increase in aridity during this period. The pollen record also suggests that the deposition of volcanic ash had an influence on the geomorphological evolution of the area.
Stability monitoring of a stationary VLBI antenna
Authors: Teskey W. F. , Niemeier W. , Sideris M. , Lyall R. G.
Published: April 2011

The proposed Canadian Long Baseline Array (CLBA) and the use of several radio telescopes in the CLBA as very long baseline interferometry (VLBI) stations to determine possible movements of tectonic plates are briefly described. The need for a monitoring network surrounding each VLBI antenna is explained, and expected movement between two possible VLBI stations is estimated. The mathematical background of precision, reliability, and sensitivity analyses is outlined. These analyses are then applied to an actual monitoring network. The numerical results are discussed to show how these analyses are particularly useful for monitoring networks.
The effect of lateral deformation on heat flow – heat production relations
Authors: Cook Frederick A.
Published: April 2011

Deformation that takes place following the fractionation of heat-producing elements can cause the relationship of surface heat flow and heat production to deviate from a simple linear trend. Lateral transport by low-angle normal faulting or thrust faulting may place the near-surface rocks above rocks with different thermal properties. Even for a simple model, the relationships can be complex, but some constraints can be placed on the vertical distribution of heat generation and layer thickness. Measurements at many sites in a province could produce an overall linear trend of surface flux and heat production. Departures from linearity may be found at sites that were disturbed (transported) following the latest cycle of radioelement fractionation. The amount of departure from linearity is a function of the thickness of the transported layer and the thermal properties of underlying layers.
Digitizing outlines of fossil specimens using video frame capture
Authors: Wilson Mark V. H.
Published: April 2011

Recently developed techniques for the analysis of biological shapes require rapid digitization of specimen outlines. A technique is described for automated capture of coordinates of fossil specimen outlines using an inexpensive video frame-capture digitizer. The method is applicable to specimens that can be silhouetted against a background, and can easily be adapted to other forms of image analysis.
Paleomagnetism of Archean rocks from northwestern Ontario: Wabigoon gabbro, Wabigoon Subprovince
Authors: Dunlop David J.
Published: April 2011

The Wabigoon gabbro of the Archean Wabigoon greenstone belt in northwestern Ontario preserves a univectorial natural remanent magnetization (NRM) with D = 246°, I = 12° (k = 19.5, α95 = 10.5°, N = 11 sites). The precision is reduced if sample means are averaged, however (k = 9.3, α95 = 9.2°, N = 29 samples). The paleomagnetic pole falls either at 160°W, 11°S (δp = 5.3°, δm = 10.6°), corresponding to an age of ~1300 Ma on the Laurentian apparent polar wander path, or the reverse of this, 20°E, 11° N, corresponding to a late Archean age (~2800 Ma). No ~1300 Ma igneous or metamorphic event is known in the area; a major west-northwest-trending dike about 9 km south of the gabbro yields a virtual geomagnetic pole at 122°W, 45°N and seems to be of Abitibi age (~2150 Ma) rather than Mackenzie age (~1250 Ma). A few gabbro samples and some greenstones from the intrusive baked zone have hybrid remanences in which a higher blocking temperature Kenoran-age (~2600 Ma) NRM is superimposed on the gabbro characteristic NRM. However, the Kenoran component may be a younger chemical remanent magnetization (CRM) residing in hematite. The hypothesis that the gabbro characteristic remanence is itself a hybrid of Kenoran and Keweenawan (~1100 Ma) NRM's, which would explain both the high between-sample scatter and the lack of a ~1300 Ma remagnetizing event, is considered but rejected because fewer than 10% of the gabbro samples exhibit multivectorial swings during alternating field or thermal cleaning. Two geomagnetic field reversals are recorded at interior sites, but only one or none is recorded near the margin of the intrusion. The different cooling histories of margin and interior, as well as the bulk of the other evidence, favour magnetization during initial cooling in late Archean time.
Presentation of magnetic anomaly map data by stereo projection of magnetic shadowgrams
Authors: Broome John , Simard Réjean , Teskey Dennis
Published: April 2011

Coloured magnetic maps published at the 1:1 000 000 scale by the Geological Survey of Canada have been found to be useful aids in support of regional geological mapping and compilation projects. However, because of the quantization into colour intervals, some of the fine detail contained in the original magnetic data is lost. These smaller features can be brought out quite effectively with the shaded relief technique, although there is an attendant loss of amplitude information, which can be recovered by means of stereo-shadowgrams. A second shadowgram is produced by offsetting the original shadowgram by an amount proportional to the magnetic intensity of each data point and then the offset and original shadowgrams are viewed as a stereo pair. An example of the effectiveness of these techniques is the detail that can be seen on the shadowgrams and stereo-shadowgrams for the Lockhart River (IMW NP 12/13) and the Thelon River (IMW NQ 12/13/14) map sheets.
Tungsten–molybdenum skarn and stockwork mineralization, Mount Reed – Mount Haskin district, northern British Columbia, Canada
Authors: Gower Susan J. , Clark Alan H. , Hodgson C. Jay
Published: April 2011

In the Mount Reed – Mount Haskin area, intrusive- and calc-hornfels-hosted stockwork Mo(−W) mineralization, oxidized W–Mo and Zn–Pb–Cu skarn mineralization, and Ag–Zn–Pb vein mineralization are spatially associated with multiphase, epizonal, magnetite-bearing granite stocks of Eocene age, emplaced into the Lower Cambrian Atan Group of the Cordilleran miogeocline.Mo(>W)-stockwork mineralization partly predated the main exposed intrusions and was related to bodies of aplitic syenogranite, vestigially preserved. Two extensive, mineralogically and texturally distinctive, but probably coeval, zoned exoskarn systems constituting the main stage (stage I) are recognised at Mount Reed. The B- and F-rich inner system was controlled by fracture permeability in dolomitic marble. It is zoned from massive magnetite skarn, at the intrusive contact, through concentrically banded ("wrigglite"-textured), diopside–phlogopite–magnetite–chondrodite–vesuvianite–(Mo-rich) scheelite skarn, to stockwork veinlets with diopside cores and serpentine–chondrodite–humite–ludwigite–magnetite marginal zones. The calcic outer system was controlled mainly by bedding-plane permeability at a gradational marble – metapelitic hornfels contact and consists of banded skarn zoned from garnet-, through ferrosalite-, to wollastonite-dominant assemblages, with fluorite as a minor but persistent constituent.Superimposed on both systems are dykelike bodies of vesuvianite–garnet skarn (stage II) and amphibole–biotite–sulphide skarn (stage III) associated with quartz veins. Scheelite is markedly enriched in the latter, retrograde, skarn facies, which is, however, of only limited development. Because the main stage skarns appear to be truncated by the Mount Reed monzogranite, it is tentatively proposed that they formed adjacent to the early aplitic syenogranite and may thus have been coeval with the Mo-stockwork system.The unusually varied exoskarn assemblages at Mount Reed well illustrate the influence of protolith composition and structure and of fluid–rock interaction on skarn development.
Late Cretaceous – Tertiary sediments offshore central West Greenland: lithostratigraphy, sedimentary evolution, and petroleum potential
Authors: Rolle Flemming
Published: April 2011

Five dry exploratory wells were drilled through Upper Cretaceous and Tertiary sediments on the West Greenland shelf in 1976 and 1977. Two of these entered Precambrian basement, two bottomed in Paleocene or Upper Cretaceous basalt, and one in Campanian mudstone. On the basis of samples and logs supplied to the Geological Survey of Greenland the sedimentary sequence has been divided into seven new formations: the Campanian Narssarmiut Formation, consisting of coarse basement wash and black mudstone; the Campanian to Eocene Ikermiut Formation, consisting of marine organic-rich mudstone; the Upper Paleocene to Eocene Hellefisk Formation, comprising shallow-marine to paralic sandstone and mudstone; the Eocene Nukik Formation, consisting of turbiditic sandstone and mudstone; the Eocene to Oligocene Kangâmiut Formation of shelf to shallow-marine clean and argillaceous sandstone; the Oligocene to Neogene Manîtsoq Formation, consisting of coarse paralic to fan delta sandstone; and the Neogene Ataneq Formation, consisting of protected shallow-marine mudstone.The sedimentary evolution of the area fits well with earlier proposed models for the tectonic evolution of the Baffin Bay–Labrador Sea region.Potential petroleum source rocks are present in the Upper Cretaceous to Paleocene mudstone, and, even though they are largely immature in the drilled sections, they are expected to have entered the petroleum generation zone in the deeper parts of the basin. Their potential is mainly for gas, but some oil potential is also present. No reservoir rocks were encountered in the deeper parts of the sedimentary sequences, and the porous sandstones that occur higher in the sequence lack seals.
Discrimination of soil erosion and fluvial sediment areas
Authors: Dickinson W. T. , Rudra R. P. , Wall G. J.
Published: April 2011

A computer model has been used to estimate potential sheet and rill erosion and delivered sediment from field-sized areas of five selected agricultural watersheds. Consideration of these estimates in relation to defined tolerance levels of soil erosion and sediment yield has resulted in the mapping of (1) areas that exhibit erosion problems and serve as sediment sources; (2) areas that exhibit only erosion problems (but do not act as sediment sources); (3) areas that serve only as sediment sources (but do not exhibit erosion problems); and (4) areas that have no significant erosion problems or sediment sources. A simple approach has been developed for the preparation of such maps on the basis of a limited data base involving factors affecting erosion and fluvial sedimentation. This relatively simple yet accurate technique offers agricultural and conservation extension personnel a method for the identification of soil erosion problem areas and (or) sediment sources.
Classification multi-spectrale et apport de la bande TM7, dans la distinction des dépôts meubles de l'île d'Anticosti, Québec
Authors: Perras Sylvain , Bonn Ferdinand , Gwyn Hugh , Dubois Jean-Marie
Published: April 2011

The differentiation between various surficial deposits and bedrock on Anticosti Island is difficult because of the dense and homogeneous forest cover and because of the subdued topography. Remote sensing allows us to solve this problem by making use of the physical characteristics of Quaternary deposits and the weathered bedrock, which influence internal drainage and the availability of soil moisture to the vegetation. A spectral simulation of LANDSAT-4 was made using an airborne Daedalus 1260, 11-channel scanner. Several supervised classifications of the digital images were made using test sites studied in the field. Using the raw data from Thematic Mapper bands TM2, TM3, TM4, and TM7, the geologic environments and the ecodynamic units could be distinguished with 70% accuracy. However, the integration of bands TM2 and TM4 with the vegetation index (VI) = [(TM4 – TM3)/(TM4 + TM3)] and the algorithme (A) = [(TM7 − VI)/(TM7 + VI)] resulted in a classification accuracy of 80%. Band TM7 (2,08–2,35 μm) distinguishes itself from the other bands by having a strong reflection over bare bedrock and an absorption by water, which allow the characterization of modern alluvial deposits. The characteristics of TM7 can also be distinguished from those of the near-infrared wavelengths of TM4, which are absorbed by forest vegetation.
Simple-cone conodont taxa from the Cobbs Arm Limestone (Middle Ordovician), New World Island, Newfoundland
Authors: Fåhræs Lars E. , Hunter David R.
Published: April 2011

New and previously described conodont taxa are reported from the upper Chazyan (Llandeilian) Cobbs Arm Limestone of New World Island, north-central Newfoundland. In addition to Ansellidae n. fam., (the following new taxa are described: Ansella n. gen., with type species Belodella jemtlandica Löfgren, 1978, Goverdina alicula n. gen. n. sp., Serraculodus alveus n. gen. n. sp., and Walliserodus dolabellus n. sp. The conodont apparatus compositions of the following species are also described: Ansella nevadensis (Ethington and Schumacher), Scalpellodus cavus (Webers), Walliserodus ethingtoni (Fåhræs), and W. nakholmensis (Hamar).
Comparison of MAGSAT and low-level aeromagnetic data over the Canadian Shield: implications for GRM
Authors: Arkani-Hamed J. , Strangway D. W. , Teskey D. J. , Hood P. J.
Published: April 2011

Band-limited magnetic anomalies over the Canadian Shield, for wavelengths of ~500–2200 km, derived from the magnetometer satellite (MAGSAT) data correlate peak for peak with the corresponding anomalies derived from the aeromagnetic data. This suggests that the anomalies detected by MAGSAT are physically meaningful. A new potential field satellite, Geopotential Research Mission (GRM), has been proposed to fly at about 160 km altitude. The magnetic anomaly map that can be derived from the GRM data is expected to have a resolution about an order of magnitude higher than the one derived from MAGSAT data. A magnetic anomaly map of the Canadian Shield, which is expected to derive from the GRM data, is shown based on the aeromagnetic data. The map delineates many major geological features quite clearly and illustrates the importance of the GRM mission for global geological mapping.
The age and origin of felsic intrusions of the Thetford Mines ophiolite, Quebec
Authors: Clague David A. , Frani El Charles S. , Eaby Jacqueline S.
Published: April 2011

The Thetford Mines ophiolite in southern Quebec was obducted in Early Ordovician time during the closing of the proto-Atlantic. The tectonized peridotite lower unit of the ophiolite is intruded by felsic dikes and pods including isolated lenses of massive rodingite, small bodies of strongly deformed diorite, and younger, less deformed quartz monzonite. These intrusions are found only near the base of the ophiolite, do not intrude the surrounding country rock, and are rootless; for these reasons they are considered to have been emplaced in the ophiolite before it reached its present location.The younger group of intrusions consists of biotite–muscovite quartz monzonite and leuco–quartz monzonite. Analyzed samples have high K2O contents, high (K2O × 100)/(Na2O + K2O) ratios, and high initial strontium ratios (0.7171–0.7179), indicating that the magma source region was continental and that these felsic rocks formed by partial melting of continental sediments. Whole-rock and mineral isochron ages suggest that the felsic intrusions are about 456 ± 4 Ma old and that they were metamorphosed about 418 ± 7 Ma ago.The detachment of the ophiolite occurred about 491 ± 3 Ma ago and is recorded by the age of the metamorphic aureole beneath the ophiolite. The felsic dikes were intruded some 35 Ma years later during the Taconic Orogeny. The lengthy time between detachment and final nappe emplacement recorded by the felsic dikes may be a requirement for the formation of abundant asbestiform chrysotile.
Geological setting and age of the Flemish Cap granodiorite, east of the Grand Banks of Newfoundland
Authors: King L. H. , Fader G. B. , Poole W. H. , Wanless R. K.
Published: April 2011

Flemish Cap, a large isolated submarine knoll 600 km east of Newfoundland, consists of a central core of Hadrynian rocks and an onlapping sequence of undisturbed to disturbed Mesozoic–Cenozoic sediments. The central core of the cap, sampled with an electric rock-core drill, comprises pink, fine- to medium-grained granodiorite, dacite, and volcanic siltstone. The granodiorite samples, collected in six out of eight cores, are remarkably similar lithologically, despite a separation of up to 65 km, and probably represent a single pluton. The aphanitic dacite and laminated cherty volcanic siltstone have been metamorphosed to subgreenschist (prehnite) facies but show no evidence of contact metamorphism.U–Pb analyses of coarse and fine zircon fractions from a granodiorite core yielded upper intercepts of 751 and 833 Ma, respectively. Although not precise, these ages probably represent the age of intrusion sometime in the 750–830 Ma range and are older than those reported for similar Hadrynian granitic rocks of eastern Newfoundland. AK–Ar age of 657 ± 29 Ma on hornblende from the same core and a K–Ar age of 615 ± 20 Ma on biotite from a granodiorite core elsewhere in the body probably represent incomplete degassing during the superimposed subgreenschist metamorphism of uncertain age.Thus the Flemish Cap granodiorite and associated rocks are part of the Avalon Zone and may represent a much older part of the Avalon Terrane than parts toward the west on Avalon Peninsula and Burin Peninsula.
The Proboscidea from the Middle Miocene Wood Mountain Formation, Saskatchewan
Authors: Madden Cary T. , Storer John E.
Published: April 2011

Zygolophodon proavus (Palaeomastodontidae) and Gomphotherium osborni (Gomphotheriidae) occur in the Middle Miocene (Barstovian) Wood Mountain Formation, Saskatchewan. Wood Mountain specimens represent the northernmost occurrences of both species.
Inferences of lithospheric evolution in Italy from Pb isotopic compositions in northern Apennine cherts
Authors: Vollmer R.
Published: April 2011

Pb isotope data by Barrett on Upper Jurassic cherts and associated ophiolites in the northern Apennines form a mixing trend with only two end members. Oblique secondary trends in the data are most likely an effect of radiogenic growth since the Jurassic and not due to multiple end members as proposed by Thorpe in his criticism of Barrett. Implications of these data for the evolution of the lithosphere in this region have not been previously discussed: (1) the distinct Pb isotopic signature of the chert end member is shared by the Pb in the Cenozoic Tuscan anatectic magmas, which suggests the same crustal provenance for both leads, and (2) the Jurassic sea-floor basalts constrain the age of anomalous metasomatized mantle now underlying most of Italy to less than 140 Ma.
Solifluction and related processes, eastern Banks Island, N.W.T.
Authors: Egginton P. A. , French H. M.
Published: April 2011

Mean surface soil movement measured over the period 1972–1983 on eight relatively low angle (< 10°), well drained slopes on eastern Banks Island averaged 0.6 cm/year. Substantial variation in mean movement was recorded amongst the slopes. The variation relates to differences in soil moisture conditions, soil grain size, and the position of the measurement transect relative to the crest or base of the slope. The former two variables and therefore the rate of movement can change rapidly across any given slope, particularly when stripes are present.Three types of movement are identified in the study area: (1) mud burst and mud flow, (2) classic solifluction, and (3) pluglike flow. The latter occurs along discrete shear planes located both within and at the base of the active layer. The existence of episodic and relatively rapid mass movement on these slopes suggests that long-term monitoring programs are necessary to adequately assess and measure slope movement.
Oxygen- and sulfur-isotope geochemistry of acidic groundwater discharge in British Columbia, Yukon, and District of Mackenzie, Canada
Authors: Everdingen Robert O. van , Shakur M. Asif , Michel Frederick A.
Published: April 2011

The Paint Pots in Kootenay National Park (British Columbia) appear to derive the Fe, Zn, Pb, and [Formula: see text] contents of their water from sulfide mineralization in Lower and Middle Cambrian carbonates. The Fe, Zn, Ni, and [Formula: see text] contents of groundwater discharging into a tributary of Engineer Creek (Yukon) are likely derived from sulfide mineralization in Devonian or Ordovician black shales exposed in the area. The high Fe and [Formula: see text] contents of a natrojarosite deposit northeast of Fort Norman (Northwest Territories) are probably derived from pyritiferous Cretaceous shales in that area. Isotope analyses of water and of dissolved and precipitated sulfur species from these three sites where acidic, heavy-metal-bearing groundwater is being discharged revealed that between 38 and 74% of the oxygen used in the subsurface oxidation of metal sulfides is supplied by H2O molecules rather than by molecular (dissolved) oxygen. The available data also suggest that lower percentages of water oxygen in the secondary sulfates reflect increasing activity of Thiobacillus ferrooxidans or similar bacteria in the oxidation process.
The geometry of folded and thrusted rocks in the Rocky Mountain Foothills near Grande Cache, Alberta
Authors: Langenberg Willem
Published: April 2011

Lower Cretaceous clastic rocks make up the Inner Foothills of the Rocky Mountains along the Smoky River near Grande Cache, Alberta. Shortening of these rocks is accomplished by folding and thrusting and averages 33% over the area studied.Folds in the area are of the chevron variety. They are caused by shortening of a multilayered sequence of alternating competent and incompetent strata, where the thickness of the competent layers is fairly constant. The folds are generally cylindrical and maintain their shapes over distances of up to 2 km along trend. However, at their tapering ends they are conical.The majority of the faults are southwest-dipping thrusts, displaying ramps that cut up stratigraphic section and flats that are parallel to bedding. The best exposed fault in the area is the Mason Thrust. Displacements along this fault increase from 150 m in the northwest to 1500 m in the southeastern part of the area. A prominent anticline below the Mason Thrust diminishes gradually towards the southeast. A conical fold with a half apical angle of 7° describes this geometry. Shortening by this fold decreases from about 30% in the northwest to 10% in the southeastern part of the area. This indicates that a decrease in shortening by folding is compensated by an increase in thrust fault displacement. It is an example of fault-to-fold displacement transfer.
Estimation of hydrogeologic parameters and groundwater-balance components based on fluctuations of the water tables
Authors: Zaltsberg E.
Published: April 2011

The Wilson Creek experimental basin is located on the slope of the Manitoba Escarpment, southwestern Manitoba. Observations of groundwater regime, weather conditions, and stream discharge were carried out in this basin from 1965 to 1980. Using groundwater fluctuations in observation wells, it was found that the values of the specific yield of till range from 0.03 to 0.04 and the specific yield of shale is equal to 0.04. Calculated vertical hydraulic conductivity of till ranges from 2 × 10−4 to 3 × 10−4 m/day.On the basis of these determinations, groundwater balances for separate segments of the watershed and for the whole of the basin were calculated. Considering the basin as a whole, it was found that the average values of groundwater-balance components during spring–summer seasons were as follows: infiltration, 111 mm or 30% of precipitation; evaporation, 58 mm or 19% of precipitation; and groundwater runoff, 61 mm or 20% of precipitation.
Glacial dispersal train of Paleozoic erratics, central Baffin Island, N.W.T., Canada
Authors: Tippett Clinton R.
Published: April 2011

A glacial dispersal train of erratics derived from Paleozoic bedrock has been delineated stretching east-northeast–west-southwest across central Baffin Island. The lithologies of these erratics suggest a derivation from strata of member B of the Ordovician Ship Point Formation to the west, which are presently either submerged or covered by Quaternary sediment in the eastern part of Foxe Basin. These Paleozoic erratics were carried from Foxe Basin onto the Baffin Upland and the western edge of the Davis Highlands. They can be inferred to have reached at least Ekalugad Fiord and the eastern part of Home Bay.
In situ gasification of coal, a natural example: additional data on the Aldridge Creek coal fire, southeastern British Columbia
Authors: Bustin R. M. , Mathews W. H.
Published: April 2011

A burning coal seam at Aldridge Creek, southeastern British Columbia, has been monitored over a 3 year period to document the geometry of the fire front, subsidence history, and gas emissions. The fire front is advancing at about 13.5 m/year at an angle of about 45–70° to the strike of the coal seam. Based on near-surface temperature anomalies, the zone of combustion, carbonization, and gasification appears to extend down the dip of the coal seam about 40 m and to a depth below ground surface of 20 m. The geometry of the fire front is mainly the result of the insulation provided by the overburden, which facilitates higher temperatures in advance of the fire at depth. With advance of the fire front the upper 2–3 m of coal is coked and partly burnt, resulting in subsidence of the overlying strata along concentric faults. Heat is initially conducted and, with opening of fractures, convected with emission gases to the surface. In hotter zones, at temperatures approaching the melting point of the rocks, radiative heat transfer may occur.With advance of the fire front towards the sampling drill holes, a general, although not consistent, decline in O2 and N2 and an increase in CO2, CO, H2, and CH4 were observed in the emission gas. All the gasification products are highly diluted by air and are not in equilibrium. The product gas emissions do not reflect any distinct zonation of combustion, reduction, or pyrolysis–devolatilization accompanying advance of the fire front, such as has been observed in cocurrent in situ gasification experiments. Lack of such a zonation is likely a result of gas leakage and a large throughput of air resulting from the development of open fractures and faults, together with the shallow depth of cover.
A note on the glacial geology and postglacial emergence of the Lake Harbour region, Baffin Island, N.W.T.
Authors: Clark Peter
Published: April 2011

Ice-flow indicators in the Lake Harbour region of northern Hudson Strait define two flow directions affecting this area during the late Wisconsinan glaciation. A pronounced southward flow direction indicated by medium- and large-scale erosional and depositional features represents ice flow from an ice dome centered to the north, perhaps Foxe Basin and (or) Amadjuak Lake. Carbonate-rich till and striations represent eastward–southeastward ice flow down the axis of Hudson Strait. Convergence of ice-sheet flow with a rapidly moving ice stream has been observed and modelled for West Antarctic ice streams and involves sharp bending of flow lines at the point of convergence. A similar scenario is proposed for the Lake Harbour region to explain the two contrasting ice-flow patterns. Impingement of an ice stream in Hudson Strait onto the southern coast of Baffin Island suggests the influence of northerly flowing ice, perhaps from the Ungava plateau.Radiocarbon dates on marine shells and archeological samples are used to reconstruct the postglacial emergence of the Lake Harbour region. The marine limit (90 m aht) and deglaciation are dated by extrapolation at ca. 8300 years BP. Postglacial emergence is characterized by an initial uplift rate of 4.4 m/100 years, which decreased to 0.2 m/100 years over the last 3900 years. The initial rate (4.4 m/100 years) is nearly 50% lower than rates calculated elsewhere in the Hudson Strait region and is interpreted to reflect the influence of an ice load centered over Amadjuak Lake directly north of the Lake Harbour region.
Palynology of Indian and European forest clearance and farming in lake sediment cores from Awenda Provincial Park, Ontario
Authors: Burden Elliott T. , McAndrews John H. , Norris Geoffrey
Published: April 2011

Palynologic analyses of four short cores collected along shallow- to deep-water transects in Second and Gignac lakes indicate two periods of forest clearance for farming. The first deforestation was by Huron Indians between A.D. 1450 and 1650, when a maple (Acer), beech (Fagus), and oak (Quercus) forest was cleared and corn (Zea) planted. This disturbance is identified by decreased tree pollen and increased Pteridium, Artemisia, and other herbs and is confirmed by Zea pollen in Gignac Lake. From 1650 to 1875 there was a forest succession to oak, birch (Betula), and pine (Pinus). Following this recovery European loggers and farmers cleared this forest and attempted farming. Besides a reduction in tree pollen, a product of this deforestation includes the pollen of weedy Ambrosia, Gramineae, and introduced European Rumex and Plantago. During the last 25 years an increase in tree pollen indicates local forest recovery consistent with present land use.By relating upland vegetation successions to lacustrine algal assemblage changes, probable ecological controls on algae during the last 600 years are identified. Peridinium willei Huitfeldt-Kaas and Pediastrum respond to changes induced by forest clearance and agriculture. Aquadulcum awendae n. sp. and Peridinium wisconsinense Eddy prefer less alkaline water.Variations in palynomorph influx are related to basin morphology and water circulation. Gignac Lake, a steep sided and relatively deep lake, directs palynomorphs from shallow marginal banks to the deeper basin, whereas Second Lake, with a gently sloping shallow lake bottom, preferentially accumulates palynomorphs close to shore.
The terminal Cretaceous iridium anomaly in the Red Deer Valley, Alberta, Canada
Authors: Lerbekmo J. F. , Louis R. M. St.
Published: April 2011

Neutron activation analysis following fire-assay preconcentration in a nickel sulphide button allows processing of relatively large samples (25 g) for precision analysis of platinum group elements. Using this method, an iridium anomaly with maximum concentration of 3.36 ± 0.04 ppb has been located at the Cretaceous–Tertiary boundary at the base of the Nevis coal seam in the Red Deer Valley of Alberta. The iridium anomaly coincides with the disappearance of diagnostic late Cretaceous palynomorphs, including all but one species of Aquilapollenites.