bluuebunny/crossref_metadata_2025 huggingface dataset:
The Amisk Group: An Aphebian(?) Island Arc Deposit
Authors: Stauffer Mel R. , Mukherjee A. C. , Koo J.
Published: April 2011

The Amisk Group (Aphebian?) near Flin Flon, Manitoba, consists dominantly of andesitic lava flows and pyroclastic rocks, with minor basalt, dacite, rhyolite, and epiclastic rocks. These have undergone regional metamorphism ranging from chlorite to garnet zone, and locally have been sheared intensely.Major element chemical analyses indicate that intensely sheared Amisk rocks near the Flin Flon and Schist Lake Cu–Zn ore bodies have undergone considerable metasomatism. The unsheared, regionally metamorphosed rocks have undergone significantly less metasomatism, and the compositions of the least-altered of these suggest an island arc tholeiite chemical affinity.The lithology, primary structures, and major-element compositions of lavas within the Amisk Group suggest deposition may have been in an island arc environment.
Precambrian Weathering in Acid Metavolcanic Rocks from the Superior Province, Villebon Township, South-Central Québec
Authors: Vogel D. E.
Published: April 2011

Chloritoid- and kyanite-bearing acid metavolcanic rocks of the Abitibi Greenstone belt have acquired an aluminum surplus by weathering prior to metamorphism. The weathering increases from the top of the volcanic unit downwards, as shown by increasing values for both Niggli-t and the Zr/P ratio. The depositional environment of these rocks is postulated to be either shallow marine or terrestrial.
Generation of metal deposits on the sea floor
Authors: Fryer B. J. , Hutchinson R. W.
Published: April 2011

Recent studies of volcanogenic base metal sulfide deposits and of metalliferous sediments in the Red Sea indicate precipitation of iron and base metals under conditions varying from reducing to oxidizing, at or near sites of fumarolic brine emission onto the sea floor. Differing lithofacies of iron-rich sediments were apparently deposited penecontemporaneously, mainly in response to changing chemical, biological, and sedimentary lithofacies conditions.Iron-rich sediments associated with the cupriferous pyrite bodies of Cyprus have been studied to determine the behavior of Fe, Mn, Cu, Zn, Pb, Ni, Co, Cr, Sn, Mo, Ag, and Au, when these fumarolic brines enter the sea bottom environment. Variations in metal abundances and ratios indicate that rapidly changing Eh is a major factor controlling metal deposition on the sea floor. The Fe/Mn ratio in these sediments is a useful indicator of the amount of interaction of these fumarolic brines and normal oxygenated sea water. Results suggest that zinc, copper, and gold are concentrated in the high Fe/Mn ratio proximal sediments; nickel is concentrated in the low Fe/Mn ratio distal sediments; and lead, silver, tin, and molybdenum are relatively unaffected by oxidation of the fumarolic brine solution by normal sea water.These concepts of sea floor deposition controlling the distribution of metals may also be applicable to other types of stratabound metalliferous deposits, like certain skarn, greisen, and gold ores, heretofore considered to be of epigenetic origin.
Ordovician geology of Akpatok Island, Ungava Bay, District of Franklin
Authors: Workum Robert H. , Bolton Thomas E. , Barnes Christopher R.
Published: April 2011

The Paleozoic sequence of Akpatok Island consists of a least 800 ft ([Formula: see text]) of exposed limestone, underlain by 1098 ft (334.7 m) of limestone, shale, and sandstone, as recognized in Premium Homestead Akpatok L-26 drill hole located on the west-central coast. The exposed carbonate rocks contain a megafaunal sequence and a limited conodont fauna ranging in age from late Middle (Barneveld) to early Upper (Maysvillian) Ordovician; a similar sequence is present within the upper Bad Cache Rapids – Churchill River Groups of Southampton Island, Hudson Bay. A conodont fauna present in the core 119 to 231 ft (36.3–70.4 m) above the Precambrian is of early Middle (Whiterockian) Ordovician age; a similar fauna is reported from the upper Ship Point Formation of Foxe Basin.One new species of the colonial coral Crenulites from the Maysvillian exposures and two new species of conodonts from the subsurface Whiterockian carbonate interbeds are erected.
Additional note on the origin of the Sudbury structure
Authors: Beales F. W. , Lozej G. P.
Published: April 2011

It has been suggested that the Sudbury Basin could be compared with the Brent meteorite impact crater and that Sudbury may also have developed a relatively flat crater floor at a very early stage. More recent paleomagnetic interpretations appear to fit an original, subhorizontal, sill-like form for the Nickel Irruptive at Sudbury. These suggestions in turn permit formulation of a more satisfying model for the early stages of Sudbury basin evolution.
Archean variolites—quenched immiscible liquids
Authors: Gélinas L. , Brooks C. , Trzcienski Jr. W. E.
Published: April 2011

Variolitic lavas from Archean tholeiitic series north and south of Rouyn–Noranda (Abitibi Metavolcanic belt, Canada) contain large, sharply defined, spheroidal to subspheroidal felsic varioles (up to 5 cm in diameter) set in a ferruginous matrix of more mafic composition. Quench texture and flow differentiation studies indicate that the variolites were produced by rapid cooling of a two-liquid magma, and that these liquids were in contact and chemically discrete prior to extrusion. Physical mixing models do not adequately account for these contiguous magmas, yet a liquid immiscible model demonstrably satisfies almost all variolite field, microscopic, microprobe, and chemical data. We conclude Archean variolites are formed by immiscible splitting of a magma of tholeiitic composition.
Magnetite–apatite intrusions and calc-alkaline magmatism, Camsell River, N.W.T.
Authors: Badham J. P. N. , Morton R. D.
Published: April 2011

The Camsell River area comprises a roof pendant of volcanic rocks within an Aphebian (~1800 m.y.) orogenic belt. Magnetite–apatite intrusions and related bodies are common and are closely associated with plutons of intermediate composition. The magnetitic intrusions are interpreted as immiscible liquids that separated from a magma of intermediate composition. The immiscible fractions were predominantly crystalline when they reached their present higher levels, and final emplacement was facilitated by volatile-streaming and fluidization. Their presence in the orogenic belt is taken as further support for the hypothesis that the orogen was of Andean type.
Geothermal measurements in five small lakes of northwest Ontario
Authors: Allis R. G. , Garland G. D.
Published: April 2011

The heat flow through the floors of five small lakes of known thermal history on the Canadian Shield was measured with a modified Bullard probe. A small correction for seasonal bottom water temperature variations was applied to temperature gradient measurements, and the heat flows are corrected for glaciation, lateral temperature gradients, sedimentation rates, and lateral thermal conductivity changes. Four lakes have an average heat flow of 49 ± 4 mW/m2 (1.2 ± 0.1 μcal/cm2 s). A high heat flow in the fifth lake is thought due to unusual refraction effects. The heat generation–heat flux combination yields a point that falls near accepted lines for the Canadian Shield.
Geological and geochronological relationships of the Thompson nickel belt, Manitoba
Authors: Cranstone Donald A. , Turek Andrew
Published: April 2011

The Pikwitonei province is an early Precambrian inlier of retrograded granulite and amphibolite facies gneisses that separates the Superior and Churchill provinces in Manitoba. The granulites are unconformably overlain by rocks of the Superior province along the southeast boundary, and are in contact with rocks of the Wabowden subprovince to the northwest. Whole rock Rb–Sr isochron analyses for the Wabowden migmatitic gneisses give an age of 2820 ± 135 m.y. (87Rb decay constant = 1.39 × 10−11 y−1). We interpret this age as representing the formation of these migmatitic gneisses by remobilization of the Pikwitonei basement either during an early stage of the Kenoran orogeny or during an orogeny earlier than the Kenoran. An additional two samples of the migmatitic gneiss give an age of 1720 m.y., which reflects updating by the Hudsonian orogeny. Similarly, whole-rock Rb–Sr analyses for an argillaceous metasedimentary rock in the Wabowden subprovince yield an age of 1640 ± 170 m.y. It is postulated that the metasedimentary and metavolcanic members of the Wabowden subprovince were deposited on, and infolded with, the migmatitic gneisses.Granitic rocks belonging to the Churchill province yield typically Hudsonian ages. A pink quartz monzonite gives an age of 1730 ± 90 m.y., while an augen quartz monzonite gives an age of 1805 ± 190 m.y. Both plutons have low initial ratios, that are, however, significantly distinct at the 5% level. Churchill province sedimentary rocks yield an age of 1975 ± 155 m.y. This age may simply be a Hudsonian overprinting or it may be the age of deposition, in which case it places a maximum age for the Setting Lake – Assean Lake fault in the area. A minimum age for one branch of the fault, is 1806 m.y. This is the age of a post-cataclastic pegmatite dyke.
Relict iceberg furrows on the Laurentian Channel and western Grand Banks
Authors: King Lewis H.
Published: April 2011

A side-scan sonar survey along the western bank of the Laurentian Channel and on the western Grand Banks revealed the occurrence of iceberg furrows that are probably of Late Pleistocene age. The occurrence of furrows in the Gulf of St. Lawrence is significant in that it helps to date iceberg furrows along the northeast Newfoundland–Labrador margin of the northwest Atlantic, provides data on the history of deglaciation of the offshore area of the Atlantic Provinces, provides a means of evaluating sea level curves, and provides additional evidence for the broad regional extent of the Late Pleistocene shoreline at 115 to 120 m.
Additions to the mammalian local fauna from the Upper Milk River Formation (Upper Cretaceous), Alberta
Authors: Fox Richard C.
Published: April 2011

New mammalian fossils from the Upper Cretaceous Upper Milk River Formation, Alberta, document the occurrence of a possibly new triconodontid species, and of an unnamed therian of metatherian–eutherian grade. The second discovered specimen of the Upper Cretaceous triconodontid Alticonodon lindoei Fox 1969 is described, and Alticondon is classified in a new subfamily. A new genus and species of spalacotheriid symmetrodont represented by lower molars at five positions and apparently not descended from the previously known spalacotheriids Spalacotherium Owen 1854 or Spalacotheroides Patterson 1955 is named and described. A lower molar is referred to the primitive therian of metatherian–eutherian grade Potamotelses aquilensis Fox 1972, The structure, size, and apparent position ([Formula: see text]) of the molar suggest relationship of Potamotelses with the Asiatic Upper Cretaceous Deltatheridiidae and the Lower Cretaceous Aegialodon Kermack, Lees, and Mussett 1965. Kielantherium Dashzeveg 1975 is a junior synonym of Aegialodon.
The palynology and palaeoclimatic significance of a dated core of Holocene peat, Okanagan Valley, southern British Columbia
Authors: Alley N. F.
Published: April 2011

Holocene vegetation and climatic changes of the Okanagan Valley, British Columbia, are inferred from fossil pollen assemblages recovered from Kelowna Bog in the central part of the valley. Broad climatic changes inferred from relict postglacial landforms in the valley are correlated with the above changes.The Okanagan Valley was ice-free and Glacial Lake Penticton drained before 8900 yr BP. A forest consisting mainly of pine (Pinus) and stands of spruce (Picea) had colonized the valley sides prior to draining of the lake. Soon after 8400 yr BP, moist conditions gave way to aridity during which grass (Gramineae) and sagebrush (Artemisia) predominated. This warm, dry interval is correlated with the Hypsithermal. Bare areas in the valley bottom were exposed to wind erosion; sand dunes formed in some areas, whereas in others, a veneer of aeolian sediment was laid down. At approximately 6600 yr BP, the climate became cooler and moister, aeolian activity diminished, and the dunes became stabilized by vegetation. During the ensuing latest climatic interval, three moister phases affected Kelowna Bog and were characterized by large increases in birch (Betula), alder (Alnus), and hazel (Corylus). These phases, which were related to increased runoff from the adjacent uplands, are tentatively correlated with the stades of the Neoglaciation recognized in southcentral British Columbia and neighbouring United States.
Precambrian atmospheric oxygen: evidence in the sedimentary distributions of carbon, sulfur, uranium, and iron
Authors: Dimroth Erich , Kimberley Michael M.
Published: April 2011

The sedimentary distributions of carbon, sulfur, uranium, and ferric and ferrous iron depend greatly upon ambient oxygen pressure and should reflect any major change in proportion of oxygen in the atmosphere or hydrosphere. The similar distributions of these elements in sedimentary rocks of all ages are here interpreted to indicate the existence of a Precambrian atmosphere containing much oxygen.Organic carbon contents and distributions are similar in Precambrian and Quaternary sedimentary rocks and sediments, although distributions in both would have been sensitive to variations in rates of organic productivity and atmospheric oxygen pressure. Sedimentary pyrite is almost invariably closely associated with organic carbon, suggestive of formation by sulfate reduction, in sedimentary rocks of any age. Archean and Middle Precambrian cherty iron formations and uranium ores resemble Phanerozoic ores and probably formed similarly by diagenetic concentration. In general, we find no evidence in the sedimentary distributions of carbon, sulfur, uranium, or iron, that an oxygen-free atmosphere has existed at any time during the span of geological history recorded in well preserved sedimentary rocks.
Cretaceous mammals (Meniscoessus intermedius, new species, and Alphadon sp.) from the lowermost Oldman Formation, Alberta
Authors: Fox Richard C.
Published: April 2011

The first mammals discovered in the Upper Cretaceous Oldman Formation, Alberta, at horizons below the upper part of the unit, can be referred to a new species of the taeniolabidoid multituberculate Meniscoessus Cope and a species of the didelphid marsupial Alphadon Simpson. The new species of Meniscoessus appears to have been the direct ancestor of M. major (Russell) from the upper Oldman and Judith River formations, and could have been directly descended from M. ferox Fox, from the Upper Milk River Formation, Alberta. The species of Alphadon most closely resembles A. wilsoni Lillegraven, from the Upper Edmonton Formation, Alberta.
New evidence from offset aeromagnetic anomalies for transcurrent faulting associated with the Bathurst and McDonald faults, Northwest Territories
Authors: Thomas M. D. , Gibb R. A. , Quince J. R.
Published: April 2011

Sinistral offsets of aeromagnetic anomalies in the Churchill Province near its boundary with the Slave Province indicate that the Bathurst fault extends some 130 km into the Churchill Province, and that it is attended by previously unrecognized major sinistral splay faults, which extend up to 160 km into the Churchill Province. The offset across the master fault is 18 km, and the cumulative offset across all the faults is 48 km. Linear aeromagnetic anomalies are offset by the McDonald fault and alternative possible correlations of the anomalies across the fault suggest dextral displacements of 125 km and 70 km.
Post-glacial paleo-oceanography of Emerald Basin, Scotian Shelf
Authors: Vilks Gustavs , Rashid M. A.
Published: April 2011

Two sediment cores taken from Emerald Basin, Nova Scotia are discussed in terms of organic geochemistry and foraminifera. The analytical results are used to infer changes in the marine environment in Emerald Basin during the last 15 000 y.The fine sediments contained relatively low amounts of organic carbon, plant pigments, sulphides with respect to total sulphur, and only background values of methane. The data indicate that the bottom of the Basin has been well oxygenated since the Late Wisconsin, including the times of lowest sea level. The foraminiferal assemblages varied from estuarine–nearshore fauna in the older sediments to the outer shelf-normal marine faunas in the surface sediments. Planktonic foraminifera were found in all levels of the cores.The faunal evidence indicates that during the Late Wisconsin sea-level minimum and the period of glacial waning, the bottom salinities of the Basin were in the order of 20‰. Emerald Basin was connected to the ocean via a wide but shallow sill that allowed the exchange of Basin waters with only relatively diluted surface waters of the ocean.
Geomorphic and hydrologic consequences of vegetation destruction, Sudbury, Ontario
Authors: Pearce Andrew J.
Published: April 2011

Near-complete destruction of vegetation over 125 km2 near Sudbury, Ontario has increased denudation rates by two orders of magnitude and caused substantial changes in hydrologic regime. Denudation by channeled and unchanneled flow, measured with erosion pins on small plots (2–1000 m2) and a small drainage basin (0.09 km2), averaged 6000 m3/km2 (maximum 24 700 m3/km2) during summer and fall in 1971 and 1972. Maximum denudation occurred during late August to October. Snowmelt runoff in 1972 yielded 1000 m3/km2 of sediment. The weighted average denudation rate, including rates of bedrock disintegration (60–170 m3/km2/y; mean 120 m3/km2/y) is 3700 m3/km2/y.Runoff coefficients average 0.88 for events with return periods between 2 and 10 years; 25% of the May–October rainfall runs off as Hortonian overland flow. Estimated sedimentation rates for three flood-control structures indicate 25% storage depletion over a 50 year period; the return period of floods then able to be retained is reduced to 50 years, compared to the design parameters of 100 year 6 h rainfall (smaller structures) and 100–200 year 12 h rainfall, 6 h P.M.P. (largest structure).
Evidences of multiple glaciation in South Nahanni National Park, Mackenzie Mountains, Northwest Territories
Authors: Ford D. C.
Published: April 2011

South Nahanni National Park transects the southern Mackenzie Mountains from a position close to the continental divide to their eastern limit. In the context of glaciation it displays three distinct zones: I, in the west, a cordilleran glacial zone with evidence of two or more phases of valley glaciation; II, in the east, a Laurentide glacial zone with evidence of invasion by three successive Laurentide ice sheets; III, a central unglaciated zone. Lacustrine deposits of two distinct phases extend into all three zones and are attributed to ice damming during the last two Laurentide glacial incursions.Stratigraphic studies of caves of the area, incorporating 230Th/234U age determinations of calcite speleothems, indicate that the earliest Laurentide incursion occurred before (350) 320 000 y BP, the others after 190 000 y BP. Events of the two glacial zones are correlated and it is suggested that there was only one major glacial event in each zone during the Illinoisan Glacial and Wisconsinan Glacial.
Strontium isotope study of the composite batholith between Princeton and Okanagan Lake
Authors: Petö Peter , Armstrong Richard Lee
Published: April 2011

Twenty-seven whole-rock samples of granitic rocks and associated mafic inclusions define a Rb–Sr ispchron of 156 ± 6 m.y. with an initial ratio of 0.70415 ± 0.00017 (95% confidence limits). K–Ar and Rb–Sr data for granodiorite, quartz monzonite, and granite are concordant with this Upper Jurassic age. K–Ar dates suggest that diorite and quartz diorite are distinctly older, 165 to 185 m.y. old. The Rb–Sr data for these more mafic rocks alone (166 ± 53 m.y.) is not accurate enough to confirm this, but is not in conflict. Country rock samples are generally similar to the batholith in Sr-isotopic composition, and nearly all mafic inclusions are equilibrated with their enclosing granitic host. The Cordilleran transition zone between relatively low initial Sr isotope ratios (0.704 and less) and relatively high ratios (0.706 and greater) appears to lie just east of the batholith studied.
Characterization of iron oxide compounds in soils by Mössbauer and other methods
Authors: Kodama H. , McKeague J. A. , Tremblay R. J. , Gosselin J. R. , Townsend M. G.
Published: April 2011

Iron oxide compounds in 12 selected Canadian soil samples have been characterized by Mössbauer, X-ray, chemical, infrared absorption, and differential thermal methods. Chemical differentiation provides useful information about the forms of iron compounds present such as crystalline, amorphous, inorganic, and organic complexed iron compounds. X-ray diffraction methods can generally identify mineral species of crystalline iron compounds. However, detection limits of goethite and hematite, which are iron oxide minerals commonly present in soils, are about 7% and 10%, respectively. The Mössbauer method is especially useful for identification of small amounts of these iron oxide compounds which are far beyond X-ray detection limits. In addition, information about grain size of hematite and goethite, the Fe3+/Fe2+ ratio and characterization of the 'amorphous' fraction are also available from Mössbauer spectra. Infrared absorption and differential thermal analyses provide supplementary data concerning organic complexed iron compounds.Hematite content in the soils examined is always lower than 10%, but goethite content varies widely and coexistence of both minerals appears to be common.
Late Hadrynian and Helikian pole positions from the Spokane Formation, Montana
Authors: Vitorello Icaro , der Voo Rob Van
Published: April 2011

The natural remanent magnetizations of Beltian argillites from the Spokane Formation (formerly Grinnell Formation) have been analyzed with alternating field and thermal demagnetization techniques. Two groups of magnetic directions have been observed. One is assumed to be the primary magnetization, representative of the Helikian (approx. 1300 Ma) geomagnetic field: D = 201.5°; I = +40°; k = 61; and α95 = 5.1° for N = 14 sites (51 samples), yielding a pole position at 15.5 °S. 134.5 °W, dp = 3.7°, dm = 6.2°. Comparisons with contemporaneous pole positions reveal good agreement. The other direction of magnetization corresponds to a Late Hadrynian age (approx. 600 to 750 Ma) and resulted from low-grade metamorphism. It is speculated that this thermal event resulted from enhanced heat flow during continental breakup in the Late Hadrynian. This direction (D = 267.5°; I = +17; k = 10; α95 = 9.1° for N = 28 specimens) yields a pole position at 5°N, 163.5°E, with dp = 4.9°, dm = 9.4°. Both groups of directions of magnetization are pre-folding, which occurred during the Laramide orogeny. Laramide deformation was only moderate, however, and the eastward thrusting of the Beltian sediments over the Lewis thrust was probably not accompanied by significant structural rotation.
Shock-produced mosaicism in plagioclase, Charlevoix structure, Quebec
Authors: Walawender Michael J.
Published: April 2011

The Charlevoix structure, Quebec, Canada, is generally accepted as a Paleozoic meteorite impact site. Plagioclase grains from samples in and around this structure were examined via X-ray (oscillation) techniques to determine the maximum range of angular misorientation between crystal subdomains (mosaicism) within a given sample (ηmax), and its usefulness as an index of shock metamorphism at Charlevoix. The complex morphological character of the impact crater can be divided into five concentric zones, which exhibit alternately high and low values of ηmax. This distribution appears to be the result of differential uplift and subsidence that followed the impact event, in that blocks which have undergone different shock histories during the impact event have been brought into juxtaposition. The wide range in ηmax within as well as between samples attests to the complex nature of the shock process and the hazards of using mosaicism as the sole index of shock metamorphism.
Palynofloral evidence for terrestrial Middle Jurassic in the Moose River Basin, Ontario
Authors: Norris Geoffrey
Published: April 2011

Miospore assemblages from a drill hole in the western Moose River Basin comprise 26 species, coniferalean pollen being numerically dominant. Some species are common to putative Middle Jurassic horizons in the western Canadian plains, and comparisons can also be made with the British and French Middle Jurassic. A large hiatus exists between the terrestrial Middle Jurassic sediments and overlying terrestrial Albian (Lower Cretaceous) strata comprising the Mattagami Formation, and may parallel a similar hiatus in southeast Saskatchewan.
A suite of alkali basalts and gabbros associated with the Hare Bay Allochthon of western Newfoundland
Authors: Jamieson R. A.
Published: April 2011

The Hare Bay Allochthon of northwestern Newfoundland consists of a series of sedimentary, volcanic, metamorphic, and ultramafic rocks which was emplaced over a Cambro-Ordovician continental margin as several thrust sheets. It probably represents a continental margin sequence overridden by oceanic crust and upper mantle. The Partridge Point gabbro, Cape Onion volcanics, and Ireland Point Volcanics, which now occur in the Maiden Point, Cape Onion, and St. Anthony tectonic slices respectively, appear to be closely related on petrographic and chemical grounds. Olivine, titanaugite, kaersutite, and plagioclase indicate that these rocks formed as a single suite of hydrous alkali basalts, possibly as part of a seamount near a continental margin. This relationship provides a link between the lower sedimentary and the upper igneous-metamorphic structural slices of the allochthon and implies that most of the transported rocks in the Hare Bay area evolved in close proximity to each other.
Wascana Creek Ash (Middle Pleistocene) in southern Saskatchewan: characterization, source, fission track age, palaeomagnetism and stratigraphic significance
Authors: Westgate J. A. , Christiansen E. A. , Boellstorff J. D.
Published: April 2011

Wascana Creek Ash, located close to Regina in Saskatchewan, is correlated with Pearlette ash, type O (classification of Izett et al. 1972) on the basis of its mineral assemblage, shard habit, composition of glass, titanomagnetite and chevkinite. Directions of magnetization and normal polarization of clay immediately below Wascana Creek ash further support this correlation, which is essentially confirmed by the fission track age of volcanic glass and zircon that show Wascana Creek Ash to be 0.6–0.7 Ma.Pearlette ash, type O, is derived from vents in Yellowstone National Park in Wyoming and Idaho, situated about 800 km southwest of Wascana Creek in Saskatchewan. Its air-fall tephra is widely distributed in the form of isolated lentils over the midcontinent region of the United States where stratigraphic relationships suggest a late Kansan, Yarmouth, or early Illinioan age.Wascana Creek Ash and its host clay occupy an intertill position; they rest directly on sandy till, interpreted as part of the Floral Formation, and are covered by till of the Battleford Formation. Thus, the Floral Formation in Saskatchewan may well be as old as the Kansan—that is, decidedly older than most current estimates, which favour an early Wisconsin age.The horizontal disposition and palaeomagnetic characteristics of the host clay, uniformity of carbonate content of the underlying till, and absence of local glaciotectonic features strongly suggest that the tephra and clay are in situ and not glacial erratics that have been transported as blocks from an older deposit. Furthermore, extensive reworking of the tephra from an older horizon is considered unlikely in view of minor detrital contamination, fresh glass, and conspicuous crop of glass-sheathed heavies. However, the stratigraphic position of Wascana Creek Ash should not be considered as firmly established for these observations of necessity pertain to just one locality; further occurrences must be found and studied before its stratigraphic position can be confidently defined.
The geochronology of some granitic bodies from eastern Newfoundland and its bearing on Appalachian evolution
Authors: Bell Keith , Blenkinsop John , Strong D. F.
Published: April 2011

Whole-rock Rb–Sr isochron ages from nine granitic plutons that intrude the Central Mobile Belt and the Avalon Zone of Newfoundland are consistent with the view that most of the magmatic activity for this segment of the Appalachian Orogen is related to the Acadian Orogeny. Most of the granites are between 400 Ma and 340 Ma old, although two from the Avalon Zone are significantly different. One, the foliated Swift Current granite, is late Cambrian – early Ordovician (500 ± 30 Ma), whereas the other, the peralkaline St. Lawrence granite, is Carboniferous (315 ± 5 Ma).Several foliated granites from the Gander Zone of the Central Mobile Belt, formerly considered to be older than Mid-Ordovician, are Silurian or Devonian in age. Five megacrystic biotite granites have ages ranging between 420 ± 20 Ma and 340 ± 10 Ma, and a leucocratic granite, the Middle Ridge Pluton, gives an age of 370 ± 15 Ma. None of the granites from the Gander Zone is older than 420 ± 20 Ma, and geochronological evidence for a Precambrian basement in the Central Mobile Belt has still to be found.The initial 87Sr/86Sr ratios show no correlation with age, although the initial ratio of 0.722 for the St. Lawrence granite is much higher than the ratios of between 0.704 and 0.709 for the other granites; this high ratio is consistent with derivation of the granite by partial melting of the continental crust.The isotopic data impose certain constraints on models proposed for the evolution of Newfoundland, the most important being: (i) extensive Devonian magmatism; (ii) intense post-400 Ma cataclasis; (iii) generation of petrographically similar granites at different times; and (iv) Carboniferous magmatism.
An analytical representation of the geomagnetic field in Canada for 1975. Part I: The main field
Authors: Dawson E. , Newitt L. R.
Published: April 2011

Approximately 51 000 observations made between 1955 and 1973 were used to produce the magnetic charts of Canada for 1975. A least-square method was used to derive sixth degree polynominals for the rectangular components X(north), Y(east), and Z(vertical). Cubic time terms were included to eliminate the customary laborious method of updating the data to the desired epoch.To reflect desired wavelengths of approximately 1000 km it was necessary to divide the map area of 31 × 106 km2 into quadrants with a unifying overlap of 10%. For consistency, X and Y were analysed together using Maxwell's curl-free relation (curl F)Z = 0. All data were weighted according to type and age.From the derived polynomials, values of D (magnetic declination), H (horizontal intensity), and Z were computed at 2° geographic grid intervals. These values were used to derive the final charts using a standard contouring package.The overall root mean square (rms) fit of the model to the input data is 174 nT. In the auroral zone, an area of high magnetic activity, the fit is generally poor. The fit to over 8500 supplementary observations is 170 nT, confirming the reliability of the model.
Rejet net probable de la faille de LG-3 et identification de structures en domes et bassins, territoire du Nouveau-Québec, Québec
Authors: Grenon Alain , Roy Denis W. , Sharma Kamal N. M.
Published: April 2011

A fault with an orientation of 327/84 NE and more than 100 km in length traverses the site of the LG-3 dam. North of the dam site, it cuts an antiform in the Archean metasedimentary rocks which are folded into domes and basins. The average net slip along this fault is 500 m ± 200 m with a normal but slighty dextral movement. The fault affects the lower Proterozoic Sakami Formation and thus is later than it. There is no indication of recent movement along the fault.
Petrology of the Blue Mountain and Bigwood felsic alkaline complexes of the Grenville province of Ontario
Authors: Duke N. A. , Edgar A. D.
Published: April 2011

The Blue Mountain, Methuen Township, and Bigwood, District of Sudbury, alkaline gneiss complexes of the southwestern Grenville province occur in areas of medium to high grade regional metamorphism equivalent to temperatures between 550 °C to 700 °C and [Formula: see text] to 7 kb (350 to 700 Mega Pascals (MPa)) total pressure. Textures of the undersaturated alkaline gneisses of both complexes are predominantly characteristic of metamorphic–metasomatic processes. Compositions of the major (feldspar, nepheline) and minor (biotite, muscovite, amphibole, pyroxene, garnet) minerals in these rocks, when compared to known stability relations and minimum melting curves of the Blue Mountain nepheline-bearing gneiss, indicate equilibration at temperatures and pressures below the maximum values for the regional metamorphism.Textures and mineral compositions in the rocks of both complexes also suggest that extensive metasomatism has taken place. Consequently these rocks must now be regarded as metamorphic metasomatic rocks produced during one or more periods of regional metamorphism. Age relationships in both complexes are in agreement with this hypothesis. The ultimate origins of the rocks of both complexes are unknown but, in the case of the Blue Mountain complex, partial melting of alkali olivine basalts, or of an unknown and possibly mantle derived source in the Bigwood complex, may have produced liquids of nepheline syenite compositions from which the present rocks were derived by metamorphic and metasomatic processes.
Timing of geological events in the circum-Pacific region
Authors: Matsumoto Tatsuro
Published: April 2011

Two aspects of the timing of geological events in the circum-Pacific area are treated here. First, the tectonic history is considered on the basis of regional correlation. The circum-Pacific belt has been mobile in various ways since the late Precambrian and orogeny proceeded poly-cyclically without showing stabilized termination in any cycle. A major evolutionary development with an adolescent stage in late Mesozoic times is recognized.Second, the timing of the late Mesozoic events is examined in more detail, using Japan as an example. Tectonic movements proceeded for long periods of time, with several intermittent impulses or stepwise accelerations of major or minor degree. Minor movements are compatible with the tectonic displacement at the time of earthquakes. Igneous activity, including emplacement of granitic bodies and some associated volcanism, was long-lasting, and episodic in space and time.
Permafrost: electrical properties of the active layer measured in situ
Authors: Wong J. , Rossiter J. R. , Olhoeft G. R. , Strangway D. W.
Published: April 2011

The dielectric constant and apparent conductivity of the active layer on Involuted Hill near Tuktoyaktuk, N.W.T., were measured in situ for both summer and winter. Measurements were made using resonating antennas near 100 MHz. The apparent values for the dielectric constant were 26 to 64 in the summer, and about 7 in the winter; for the conductivity, values of 0.012 to 0.12 mhos m−1 (0.012–0.12 S m−1 in summer, and about 10−4 mhos m−1 (10−4 S m−1) in winter, were obtained. The low losses observed in winter indicate that EM sounding should be possible in the area when the active layer is frozen. It is concluded that the antenna method is a quick and inexpensive means of making in situ electrical measurements near 100 MHz.
Petrology and alteration of selected units of Mid-Atlantic Ridge basalts sampled from sites 332 and 335, DSDP
Authors: Baragar W. R. A. , Plant A. G. , Pringle G. J. , Schau Mikkel
Published: April 2011

Closely spaced samples spanning 'flow units' at sub-bottom depths of 500 and 590 m in the drill hole at site 332B and a pillow at depth of 460 m, site 335, as well as a few individual samples at various depths in these holes and in the hole at site 332A, were studied with a view to determining compositional changes effected by submarine alteration. The rocks are predominantly plagioclase-olivine phyric tholeiitic basalts, with the exception of the lower unit of 332B, which is a picrite formed by the concentration of olivine megaphenocrysts in olivine tholeiitic basalt, is markedly flow-differentiated, and is assumed to be a sill. Three generations of plagioclase and olivine evident in some of the samples as corroded megaphenocrysts (An86−78, Fo89), euhedral microphenocrysts (An76−72, Fo85−84), and groundmass crystals (An72−61, Fo85−84), record a crystallization history that begins at depth, continues en route to the surface, and ends with quenching on the sea floor. Filling interstices of the groundmass are intergrowths, commonly submicroscopic, of pyroxene–plagioclase and dark, poorly resolved titanomagnetite-charged magmatic residue. The pyroxenes arc augites, ranging to subcalcic and ferroaugite. In places, particularly near pillow and flow unit margins, magma residue partially or completely in-fills vesicle cavities (segregation vesicles). Volatile-bearing phases (notably chlorophaeites, saponite, palagonite, amorphous silica-bearing hydrous iron oxides, and carbonates) tend to be characteristic of the three principal sites in which they are found: palagonite in the glassy margins of pillows and (or) flow units, complex hydrous mineraloids adjoining veins, and chlorophaeites and saponites in the interstices of the crystalline matrix of rocks remote from veins. The latter have the aspect of primary minerals. Palagonitization results in gains in K, Fe, Ti, and Cl, and losses in Ca, Mg, and Na, but net gains and losses in the other sites are less certain. Hydration and oxidation of iron invariably accompany development of volatile-bearing phases, but there is no correlation between these parameters and variation in content of the other analysed elements. Principal component analysis shows that the major part of the compositional variation can be explained by primary factors. In these samples chemical exchange with seawater appears to be limited, possibly because of their rapid isolation by burial from the main body of ocean water.
Basalts from DSDP Leg 37 and the FAMOUS area: compositional and petrogenetic comparisons
Authors: Bryan W. B. , Thompson G.
Published: April 2011

Basalts from the DSDP Leg 37 sites can reasonably be supposed to have originated at or near the present-day spreading center (FAMOUS area) investigated and sampled in detail by surface vessels and submersible vehicles in the median valley. Nevertheless, the Leg 37 samples show a more restricted range of compositions than those presently observed in the median valley. Basalt glasses from DSDP Leg 37 contain 0.6 to 1.3 wt.% TiO2, with FeO*/MgO ranging between 0.8 to 1.5. In contrast, basalt glasses from the median valley range from 0.5 to 2.0 wt.% TiO2, and FeO*/MgO varies from 0.7 to 1.8.The low-TiO2 basalts at site 332B can be compared to similar very young basalts that characterize the central volcanic extrusive hills such as Mt. Pluto and Mt. Venus in the median valley. The more iron-enriched basalts can be compared with certain FAMOUS basalts dredged from the rift mountains south of fracture zone A. The major- and minor-element variation trends among Leg 37 basalt glasses parallel trends within the FAMOUS data set, which are compatible with high level fractional crystallization. Overall, the best parent for site 332 basalts is a 'low-olivine' candidate parent magma type, which has been found in fracture zone B and in the median valley south of fracture zone B, and which resembles basalt at site 334. Compared to some parent–residual pairs tested in the FAMOUS area, the fractionation calculations for site 332 variations show good fits for TiO2 and K2O, and show little excess LIL-element enrichment. In all calculations, pyroxene dominates olivine as the most important mafic phase. This is consistent with the observed slight relative enrichment in light rare-earth elements in the 332A glasses compared to their inferred parents, but cannot be reconciled with light rare-earth depletion at site 335.A possible interpretation of the lava sequence at site 332B is that it represents a rapid accumulation of basalts extruded over a relatively short time span in the center of the median valley. Fractionation may have taken place in a stagnating chamber isolated by collapse of the valley walls. In this chamber there was not sufficient time or space to develop the thermal gradients and marginal enrichment in LIL-elements and volatile components which may have generated the high TiO2 basalts in the FAMOUS area. Geochemically unique basalt at site 335 shows depleted light rare earths combined with LIL-element and TiO2 enrichment. This basalt could have been a flank eruption unrelated to processes in the median valley.
Metagabbronorite from DSDP hole 334: an example of high-temperature deformation and recrystallization near the Mid-Atlantic Ridge
Authors: Helmstaedt Herwart , Allen John M.
Published: April 2011

Five gabbros and three peridotites from hole 334 were examined for postmagmatic deformational changes and metamorphic recrystallization. The condition of the gabbros ranges from unaltered, to slightly altered and deformed, to highly deformed and metamorphosed, the latter type being confined to narrow shear zones. Petrofabric studies and electron microprobe analyses of mineral phases of a foliated metagabbronorite from such a shear zone suggest the following post-magmatic history: (1) strong plastic deformation and anhydrous synkinematic recrystallization of igneous plagioclase (An90−85), clinopyroxene, and orthopyroxene to the granulite facies mineral assemblage of strongly zoned plagioclase (An80−65), diopside, and orthopyroxene; relics of the igneous minerals survived as highly strained porphyroclasts; (2) synkinematic growth of amphibole consisting of a patchy intergrowth of tremolite and actinolitic hornblende; the amphibole fabric is compatible with strain estimates by the centre-point method; (3) mainly static hydrous alteration — growth of (?) vermiculite and sericitization.Penetrative deformation probably initiated shortly after intrusion and took place during cooling of the rocks from approximately 800 °C to 300 °C. The bulk of the strain in the metagabbronorite of the shear zone predates the serpentinization of the peridotites. Many textural and fabric features in alpine-type gabbro–peridotite complexes that are ascribed to regional metamorphism and deformation during orogenic emplacement may originate shortly after intrusion near or at an accreting plate margin.
Middle and Upper Ordovician graptolites from the St. Lawrence Lowlands, Quebec, Canada
Authors: Walters Martin
Published: April 2011

Eleven species of Middle and Upper Ordovician graptolites are described and illustrated, a lectotype is selected for Orthograptus reudemanni (Gurley) and the occurrence of eighteen other species is recorded. The specimens were collected from sections along the Bécancour, Nicolet, Nicolet Sud-Ouest, and St. François Rivers of the St. Lawrence Lowlands, Quebec. The graptolite zonal scheme proposed by Riva for eastern North America is reviewed and adopted in the present study.
Ophiolitic mélange and its significance in the Fleur de Lys Supergroup, northern Appalachians
Authors: Williams Harold
Published: April 2011

Ophiolitic mélange consists of a chaotic mixture of sedimentary rocks and igneous rocks derived from the ophiolite suite of rock units. Its formation involves surficial mass wastage, gravity sliding, and tectonism at consuming plate boundaries. Most worldwide examples relate to ophiolite obduction and the destruction of stable continental margins.The Fleur de Lys Supergroup of the northern Appalachians consists of polydeformed and metamorphosed, mainly clastic sedimentary rocks that accumulated at the Hadrynian to early Paleozoic stable continental margin of eastern North America. Greenschists at or near the top of the succession in the east (Birchy Complex) contain zones of typical ophiolitic mélange. These contain large blocks of serpentinized ultramafic rocks, actinolite–fuchsite alterations of smaller ultramafic blocks, altered gabbro, a variety of clastic sedimentary blocks, and marble. All of the rocks are multideformed and metamorphosed so that the mélange was subjected to the full range of Fleur de Lys deformations.The presence of polydeformed and metamorphosed ophiolitic mélange in the Fleur de Lys Supergroup implies an early disruption or imbrication of its rock units. This disruption and mélange formation are interpreted to be related to transport of ophiolite complexes such as the Bay of Islands Complex across an initially undisturbed continental rise prism, the Fleur de Lys Supergroup. Later polyphase deformation and metamorphism of the Fleur de Lys Supergroup are possible results of continued structural submergence and telescoping of the continental margin beneath a thick cover of transported ophiolite rock units.
Rare earths in the Marcy and Morin anorthosite complexes
Authors: Seifert K. E. , Voigt A. F. , Smith M. F. , Stensland W. A.
Published: April 2011

Instrumental neutron activation analysis (INAA) of rare earth element (REE) abundances for a northern portion of the main Adirondack (Marcy) anorthosite and the adjacent Tupper–Saranac mangerite indicates they are genetically unrelated. Marcy anorthosite characteristically has low REE abundances and a positive europium (Eu) anomaly and a thin discontinuous border facies with no Eu anomaly. Tupper–Saranac mangerite has a lower mafic-rich portion with a relatively low REE abundance and a positive Eu anomaly, and an upper quartz-rich portion with a higher REE abundance and a negative Eu anomaly. A thin border facies of basal mangerite has an intermediate REE abundance and no Eu anomaly. These data are best interpreted in terms of separate magmas and differentiation within the mangerite body. Rare earths were also determined for some Morin Complex rocks.The Sm/Eu ratio from our INAA data agrees well with that calculated from individual minerals for the early crystallized, lower mafic-rich portion of the Tupper–Saranac mangerite, but poorly for the later crystallized, upper quartz-rich portion. The poor agreement between calculated and experimental Sm/Eu ratios in the quartz mangerite is probably due to depletion of Eu relative to Sm during crystallization of the magma, and supports a differentiative relationship between the mafic and quartz mangerite units.