bluuebunny/crossref_metadata_2025 huggingface dataset:
Upper Callovian and Lower Oxfordian Ammonites from Southeastern Bowser Basin, British Columbia
Authors: Frebold Hans , Tipper H. W.
Published: April 2011

Ammonites of the Late Callovian Lamberti zone and of the Early Oxfordian Mariae and Cordatum zones are described from sedimentary sections on the south and southeastern margins of the Bowser Basin. They date a regressive sequence of Hazelton Group sedimentary rocks older than the main clastic sediments of the Bowser Basin. This is the first record of Upper Callovian rocks in Canada.
Paleomagnetism of the Whitestone Anorthosite and Diorite, the Grenville Polar Track, and Relative Motions of the Laurentian and Baltic Shields
Authors: Ueno H. , Irving E. , McNutt R. H.
Published: April 2011

The Whitestone anorthosite and diorite are situated in the Grenville Structural Province north of Parry Sound, Ontario. They are intruded into sediments and igneous rocks, the whole being metamorphosed to amphibolite facies. Aside from soft magnetizations due to the present field four magnetizations are present, two owing to hematite, the third mainly to magnetite, and a fourth of uncertain source. It is argued that these are thermoremanent magnetizations acquired during very slow cooling following regional metamorphism in the interval 1100 to 1000 m.y. A single-stage cooling model based on Neel's single domain theory is developed, which suggests that the hematite magnetizations were acquired during slow cooling at about 240 °C and the magnetite magnetizations at about 200 °C. The poles from Whitestone rocks fall among a group of poles from elsewhere in the Grenville Province. There are serious problems in integrating these Grenville poles with those from other parts of the Canadian Shield, and three possible ways of relating them are evaluated. Poles from Grenville-type rocks from the Baltic Shield are near to the Grenville poles after correction is made for the late Phanerozoic opening of the Atlantic, showing that the relative positions of Laurentian and Baltic Shields before and after the Caledonian orogeny were very similar. There is however a small but significant difference, and this is attributed to Caledonian diastrophism.
Influence of White Spruce Trees on Permafrost-Table Microtopography, Mackenzie River Delta
Authors: Gill Don
Published: April 2011

The topography of the permafrost table in the Mackenzie River Delta is remarkably uniform. However, differences in active layer thickness are characteristically found around the stems of white spruce trees where conical depressions occur in the permafrost table. The locally increased active layer thickness appears to result from the interaction of the following factors, all of which cause greater heat diffusivity into the soil near tree stems: (1) some 25% of the gross rainfall is intercepted by individual spruce crowns, which causes a corresponding decrease in soil moisture below the tree; (2) accelerated sediment deposition around spruce stems during the spring flood creates small alluvial deposits that provide a locally better drained site; (3) the growth of insulative mosses around tree stems is also retarded by the increased sediment deposition; and (4) the low-albedo slopes of alluvial deposits surrounding tree stems intercept more solar radiation than the normal flat surfaces away from trees.
Stratigraphical Studies on the Shoreline Displacement of Lake Superior
Authors: Saarnisto Matti
Published: April 2011

Shoreline displacement in the Lake Superior basin was followed, independently of morphological data, by studying sediments of small lake basins at different elevations in the vicinity of Sault Ste. Marie, Wawa, and Marathon, Ontario. Emergence of small lakes, resulting from water level changes in the main basin, is documented in bottom sediments, and can be dated by radiocarbon and pollen analyses. The new stratigraphical findings were correlated with the earlier established morphological shorelines, and thus the Late Wisconsinan and Holocene history of lake levels was worked out.High post-Main Algonquin glacial lakes formed the highest shorelines along the east shore from Sault Ste. Marie up to Alona Bay between approximately 11 000 and over 10 100 B.P. Contemporaneously a series of Post-Duluth glacial lakes occupied the western Superior basin, subsequent to Glacial Lake Duluth. As the ice retreated to the north shore at 9500 B.P., Lake Minong came into existence. Its level was apparently controlled by a threshold higher than the present at Sault Ste. Marie. The water level of Lake Superior fell to the low water Houghton stage by 8000 B.P. The transgression which resulted in the Nipissing Great Lakes reached the Superior basin about 7000 B.P. and culminated 5500 B.P. Land uplift on the east shore of Lake Superior was very rapid immediately after the deglaciation, followed by decreasing rates up to the present, and there are all indications that the process has been continuous.
Microfossils from the Dismal Lakes Group (Neohelikian), District of Mackenzie
Authors: Donaldson J. A. , Delaney Gary
Published: April 2011

Microfossils have been discovered in thin sections cut from a sample of black, laminated, nodular chert collected from the Neohelikian Dismal Lakes Group of the Dismal Lakes area, District of Mackenzie. Two distinct morphological forms are differentiated: filaments and spheroids. The filaments are further subdivided, on the basis of morphology, into four basic varieties: (1) septate, unbranched, uniseriate filaments composed of chains of spheroidal to ellipsoidal cells showing marked constriction between cells, (2) septate, unbranched, uniseriate filaments characteristically lacking constrictions between cells, (3) nonseptate, unbranched filaments of large diameter (> 1.8 μm), (4) nonseptate, unbranched filaments of small diameter (< 1.3 μm). The spheroidal structures occur singly, in pairs and in clusters, and some of them contain blebs of carbonaceous matter which may represent remnants of organelles, reflecting eucaryotic affinities.
Molar Structure and Function in the Early Cretaceous Mammal Pappotherium: Evolutionary Implications for Mesozoic Theria
Authors: Fox Richard C.
Published: April 2011

Aspects of structural and functional features of molar dentitions in Mesozoic Theria are interpreted in relation to recently discovered mammalian taxa of primitive tribosphenic grade. Single-rank, oblique prevallum-postvallid shear and occlusion between the paracone and distal metacristid characteristic of Triassic and some Jurassic pretribosphenic therians are shown to be retained after the origin of a true protocone, as exemplified in the primitive therians Aegialodon (Early Cretaceous) and Potamotelses (Late Cretaceous). By contrast, double-rank, transverse, prevallum-postvallid shear and loss of contact between the paracone and distal metacristid, are first seen in Cretaceous metatherians and eutherians, including the Albian Pappotherium and Holoclemensia. Aegialodon, Potamotelses and the Cretaceous Deltatheridiidae may be members of a high level taxon of therians of primitive tribosphenic grade that included the ancestors of Metatheria and Eutheria.
The Fracture Porosity of Glacial Till
Authors: Grisak G. E.
Published: April 2011

The effective porosity of fractured till is obtained using two independent methods. The first method is based on tritium tracer studies, hydraulic head measurements and digital model simulations, while the second method is the mathematical evaluation described by Snow (1968) for fracture porosities of consolidated rock. The results are remarkably similar, suggesting an effective porosity of fractured till of about 0.0002.
Paleontologic Evidence of Marine Sediments in the Eureka Sound Formation of Ellesmere Island, Arctic Archipelago, N.W.T., Canada
Authors: West Robert M. , Dawson Mary R. , Hutchison J. Howard , Ramaekers Paul
Published: April 2011

Paleontologic investigation of the early Tertiary Eureka Sound Formation on Ellesmere Island, N.W.T., demonstrates the presence of well developed marine beds in that unit, which was previously considered almost completely terrestrial. This new interpretation is based largely upon the occurrence of remains of foraminifers and fish at four localities.
Stratigraphy of the Ordovician St. George Group in the Port-Au-Choix Area, Western Newfoundland
Authors: Kluyver H. M.
Published: April 2011

Stratigraphic sections were measured in the very complete coastal exposures around Port-au-Choix village in western Newfoundland. A formal stratigraphic subdivision of the Ordovician St. George Group into three formations is proposed. They are, from oldest to youngest: the Barbace Point Formation, a 21 + m thick unit of dense dolostone, showing diagenetic solution features; the Catoche Formation, 100 m thick, consisting of well bedded limestones with shallow-water indications; the Port-au-Choix Formation, 35 m thick, massive sugary dolostones grading into silty dolostones, with diagenetic solution features. Detailed descriptions of all new formations are given, as well as the rationale behind this new nomenclature. The Early Ordovician depositional history of the area is seen as a succession of two erosional and depositional cycles, not completely preserved in the record, whereby the Barbace Point Formation was subjected to subaerial erosion, creating a hiatus between this formation and the overlying Catoche Formation; the latter represents the beginning of a new depositional cycle which was possibly interrupted before the youngest Port-au-Choix Formation was deposited. After Port-au-Choix times, renewed erosion took place before the Table Head Group was formed.
Permafrost Features under Arctic Lakes, District of Keewatin, Northwest Territories
Authors: Shilts William W. , Dean Walter E.
Published: April 2011

In the District of Keewatin, west of Hudson Bay, numerous shallow lakes occupy depressions on the perennially frozen, glaciated terrain north of the treeline. Many lakes in the vicinity of Kaminak Lake have extensive shallow areas that are characterized by features of probable periglacial origin. Some features, such as polygonal patterns, frost-heaved boulders, and mudboils, are similar to those of the subaerial landscape.Digitate, cobble-covered ribs and boulder-filled troughs that commonly form a crenulate pattern on the shallow shelves adjacent to till-covered shores are thought to be the subaqueous equivalents of mudboils that are common on the adjacent till plains. They are composed of till and are underlain by an undulating frost surface that is raised beneath troughs and depressed under ribs.Holes with or without raised rims often occur singly or in clusters on loose, sandy silt bottoms in water depths less than 2.5 m. A frost table underlies the bottoms of these holes at depths of 30 to 50 cm in early August. Holes may be either sites of strudel scour or sites of final points of attachment of winter ice to the frost table, just before the buoyancy of the ice caused it to break free from the bottom in the spring, extracting frozen sediment from the surrounding unfrozen sediment, leaving a hole.The features described are restricted to water depths that are probably equivalent to the average maximum thickness of winter ice. Thus, they represent areas where the lake is seasonally frozen to the bottom, and may be restricted to portions of lake basins underlain by perennially frozen ground.
Data Capture in the Construction of MINDEP's Computer-Based, Mineral Deposits Files
Authors: Montgomery J. H. , Sinclair A. J. , Wynne-Edwards H. R. , Fox A. C. L. , Giroux G. H.
Published: April 2011

MINDEP is a computer-processable mineral deposits filing system being developed in the Department of Geological Sciences, University of British Columbia. At present, information for 6500 mineral deposits in British Columbia is being coded and entered into the system. A major problem facing any such file construction is the mechanical one of systematizing information, verifying it, entering it in computer-processable form and, in doing so, eliminating errors—a process termed 'data capture'. We have adopted an interactive data entering system using an off-line minicomputer with CRT display and auxiliary disk storage. Since a geologist can collect, enter, and check his own data without intermediaries, the system is virtually error-free. We commend it as an efficient, economical, and advanced routine for many related applications.
Near-bottom Currents in the Mid-Atlantic Ridge Rift Valley
Authors: Keller George H. , Anderson Susan H. , Lavelle J. William
Published: April 2011

Near-bottom current measurements during a 46 day period (October to December 1973) in the rift valley of the Mid-Atlantic Ridge just south of the Azores reveal a mean flow at two stations of 2.6 and 8.2 cm/s, predominantly trending parallel to the northeast orientation of the valley. Maximum velocities recorded at the sites were 14.4 and 24.2 cm/s. Semi-diurnal tidal currents appear to strongly influence the flow within the valley causing current reversals, except in areas where local topography and constrictions in the valley apparently result in a unidirectional flow to the northeast.
Remanent Magnetization and Magnetic Susceptibility Anisotropy Measurements in Lac des Mille Lacs Area of Northwestern Ontario
Authors: Nwachukwu S. O. , Currie J. B.
Published: April 2011

Remanent magnetic studies in the Lac des Mille Lacs area of northwestern Ontario have revealed unstable remanence directions in foliated Archean metavolcanics. Instabilities are of such a magnitude that remanence directions are unsuitable for the application of a fold test toward resolving the attitude of fold limbs in the highly deformed sequence of volcanic flows in this area.Measurements of magnetic susceptibility anisotropy indicate a slight preponderance of magnetic foliation over lineation. Anisotropy is due to shape effect and to stringing together of magnetic particles. A close correlation appears to exist between the attitude of structural foliation and that of susceptibility anisotropy and suggests a potential use for this property in structural mapping of metavolcanics within outcrops where foliation is scarcely visible. Distribution of the prolateness factor may be useful in deriving qualitatively, the pattern of strain distribution.
Geology, Magnetic Expression, and Structural Control of the Central Somerset Island Kimberlites
Authors: Mitchell Roger H.
Published: April 2011

The Somerset Island kimberlite field is composed of three diatremes Peuyuk, Korvik, and Selatiavak. The largest diatreme, Peuyuk, an enlarged fissure, is a composite intrusion; three petrographically distinct phases (A, B, and C) being recognized on the basis of oxide mineralogy and the presence or absence of immiscible carbonate: (A) spinel and perovskite with no zonations or reaction rims, no immiscible carbonate, (B) epitaxially zoned chrome spinels, magnetite and perovskite with reaction rims, no immiscible carbonate, (C) oxides as in B, but with no magnetite and abundant immiscible carbonate. Selatiavak and Korvik are each composed of two small oval intrusions and are petrographically similar to Peuyuk C. All the kimberlites are characterized by a positive (500–2000γ) magnetic anomaly. Emplacement of the kimberlites has been controlled by structures in the Precambrian basement gneisses, the diatremes being developed from hidden dikes at depth at points of crustal weakness.
Diagenesis of Postglacial Carbonate Deposits in Saskatchewan
Authors: Rostad H. P. W.
Published: April 2011

Two postglacial carbonate deposits in Saskatchewan were studied to determine diagenetic changes occurring under different chemical and physical environments. The presence of aragonite and calcareous shells suggests that the dominant source of the carbonates was biologic precipitation. The well drained Sturgeon Lake site contains predominantly aragonite. Percolating rainwater is converting aragonite to calcite in the upper 69 cm. The poorly drained and saline Debden site contains a mixture of aragonite, calcite and dolomite. The dolomite content increased with depth, particularly in the fine silt (2–5 μm) and clay fractions (<2 μm). X-ray diffraction patterns indicate that the calcite contains approximately 5 mol percent MgCO3 and that the dolomite is enriched with Ca. High concentrations of magnesium and sulfates in the interstitial water is preventing the transformation of aragonite to calcite, instead the aragonite is being converted to dolomite.
40Ar/39Ar Spectrum Ages on Logan Intrusions, a Lower Keweenawan Flow, and Mafic Dikes in Northeastern Minnesota—Northwestern Ontario
Authors: Hanson Gilbert N.
Published: April 2011

The 40Ar/39Ar method using stepwise heating has been applied to 11 Precambrian mafic rocks in Minnesota and Ontario to test the technique on samples varying from extremely altered to essentially unaltered and to date some of the Lower and Middle Keweenawan igneous rocks. Four essentially unaltered samples give plateau ages which appear to be reliable and may date the time of intrusion. One strongly metamorphosed sample gives a plateau age which may date the time of metamorphism. The altered mafic rocks give patterns which are inconsistent, difficult to interpret, and have higher ages for the higher temperature fractions. Essentially unaltered samples may also give inconsistent patterns. For the Keweenawan igneous activity along the northwest shore of Lake Superior near the Minnesota–Ontario border and a Logan sill near Lake Nipigon, the plateau ages suggest that three Lower Keweenawan Logan intrusions occurred 1150 to 1170 m. y. ago, although it is possible that the sills near the Minnesota–Ontario border are older; that the Keweenawan igneous activity ended about 1135 m.y. ago, based on one late dike analysis; and that a basal Keweenawan basalt flow was metamorphosed and cooled enough to retain argon by 1095 m.y. ago.
Variation in Trace Element Concentrations along the length of the Ottawa River
Authors: Merritt W. F.
Published: April 2011

Water samples taken at seven locations along the length of the Ottawa River in July, 1972, have been analyzed for 35 elements using thermal neutron activation and high resolution Ge(Li) detectors. Despite major sources of pollution on the river most macrocomponents (> 1 μg/l) are relatively unaffected. An anomalous decrease in concentration is found at one of the sampling stations for elements < 1 μg/l. Abnormal fractionation of most elements between water and suspended material was observed in a section of the river where large quantities of fresh wood fibres were being produced by a fluming operation.
Etude geochronologique des granitoïdes de la Mancellia, Massif Armoricain, France
Authors: Jonin Max , Vidal Philippe
Published: April 2011

Geochronological investigations have been carried out for the Mancellia granitoïdes by the Rb–Sr whole rock isochron method (λ 87Rb = 1.47 10−11 y−1). It appears that three periods of magmatism have occurred: 596 ± 12 m.y. for the main massif, 507 ± m.y. for the leucogranites, and 487 ± 15 m.y. for the Lanhélin blue granodiorite. These data, very similar to those obtained in eastern North America, should prove useful in the attempts to correlate circumatlantic basement rocks.
Analysis of Heat Flow Data–Vertical Variations of Heat Flow and Heat Producing Elements in Sediments
Authors: Hamza V. M. , Beck A. E.
Published: April 2011

Gamma ray spectrometric techniques have been used for the determination of uranium, thorium and potassium contents from cores selected at 3 to 4 m intervals from a 600 m deep borehole in sedimentary formations and the results compared with a similarly detailed examination of heat flow, and some physical properties, from the same borehole.The results indicate a broad positive correlation between thermal resistivity and some of the radio-element parameters and between heat flow and heat production. The heat production variations down the borehole are not quantitatively sufficient to explain the observed heat flow variations. The uranium series appears to be in radioactive equilibrium even in those sections where the uranium content is low, the porosity relatively high and the heat flow low; it is therefore concluded that the depletion of uranium is due to an ancient rather than a recent leaching process and that it is unlikely that the heat flow variations along the borehole are due to existing or recent underground waterflows. Long term geochemical reactions are now thought to be the most likely explanation of the heat flow variations.
Factors Influencing Desorption of Mercury from Bed Sediments
Authors: Kudo Akira , Mortimer D. C. , Hart J. Sanford
Published: April 2011

The desorption rate of mercury from bed sediments was determined by a 10 week experiment. The rates ranged from 0.1 ng/cm2/day to 1.0 ng/cm2/day for Ottawa River bed sediments, depending on the environmental conditions. The rates decreased with an increase of exposure period to the water, but increased with an increase in the depth of bed sediments. The amount of mercury desorbed from bed sediments to overlying water was highly dependent on the volume (depth) of bed sediments. Calculations based on the experiment showed the half-lives of total mercury associated with bed sediments from as short as 2.1 years to as long as 1.8 × 102 years, depending on the depth of the bed sediments.
Paleopathology: Exostoses of the Third Metacarpal in Pleistocene Horses from the Yukon Territory
Authors: Choquette L. P. E. , Harington C. R. , Archibald J.
Published: April 2011

Two third metacarpals from extinct Yukon Pleistocene horses display pathological exostoses. One specimen is from the Yukon wild ass (Equus (Asinus) lambei) of probable late Pleistocene age; the other is from a large horse like Equus (Plesippus) verae, which may be of early middle Pleistocene age or somewhat later.
A. Rare Case of Articulated Transverse Processes in a Lumbar Vertebra of the Pleistocene Horse Equus scotti
Authors: Harington C. R.
Published: April 2011

Articulated transverse processes are noted on the first lumbar vertebra of a mounted skeleton of a Pleistocene horse Equus scotti from Rock Creek, Texas. This unusual situation is attributed to aberrant genetic programming.
Convention for Reporting Magnetic Anisotropy of Till
Authors: Gravenor C. P. , Stupavsky M.
Published: April 2011

The determination of the fabric of a till is usually carried out by measuring the orientation of the principal axes of a number of pebbles in a till or by measuring the orientation of the principal axes of smaller particles under a microscope.The measurement of magnetic susceptibility of anisotropy of till provides an alternative method to determine the fabric of a till. As this technique has not been used extensively by glacial geologists, the purpose of this note is to provide a framework for sampling and reporting of results.
Le traçage automatique de cartes d'isovaleurs: un algorithme simple en FORTRAN IV.
Authors: Davaud Eric
Published: April 2011

A very short mapping program in FORTRAN IV is proposed and discussed employing geological and topographical examples with regularly and irregularly spaced data. Interpolation procedure is based on a local first degree polynomial function. Maps are obtained on a line printer and are comparable to those drawn manually.
Determination of Magnetic Polarities of Dredged Basalts: A Limitation of the Method
Authors: Barr Sandra M.
Published: April 2011

Magnetic polarity determinations were attempted on 17 unoriented specimens of basalt dredged from 11 locations on Juan de Fuca Ridge and adjacent Heck and Heckle Seamount Chains (Northeast Pacific Ocean). Irving's method involving comparison of NRM and ARM demagnetization curves appears to work consistently only when the NRM has been demagnetized to about 2% or less of its initial intensity and when the ratio of intensity of initial ARM to intensity of residual NRM is high (in the order of 50). For 11 samples meeting these requirements, the polarity determined matches that predicted from the magnetic anomalies in the area of the dredge station. For the other specimens, it is shown that the position of the ARM demagnetization curve was not stabilized under the conditions of the experiments and normally magnetized samples cannot be reliably distinguished from reversed rocks.
Petrology of the South Mountain Batholith, Nova Scotia
Authors: McKenzie C. B. , Clarke D. B.
Published: April 2011

Approximately one-third of western Nova Scotia is underlain by granitic rocks of the South Mountain batholith. The pi u ton is an epizonal complex of granodiorite, adamellite and alaskite which was emplaced after the folding and metamorphic events of the Acadian orogeny. Chemical and petrographic data suggest that the rocks comprise a single comagmatic suite related by the fractional crystallization of biotite and plagioclase. The magma for the batholith may have been produced by partial fusion of the lower crust, or through a hybridization of mantle and crustal melts.
Paleomagnetism of the Mesozoic Coast Parallel Dolerite Dikes of West Greenland
Authors: Fahrig W. F. , Freda G.
Published: April 2011

Paleomagnetic measurements on 61 drill cores from eight sites of the Coast Parallel dikes of west Greenland (Fiskenaesset area) have yielded a pole position at 169°E, 54°N, α95 = 5.9°. When these data are combined with those from the Nunarsuit-Tornarssuk area (Ketelaar 1963) the pole is 168°E, 56°N, α95 = 6°. Reversely magnetized dikes are present in both areas.The Coast Parallel dike pole lies close to the Triassic pole position for North America if corrected for Bullard's fit. The dikes were therefore intruded prior to the Mesozoic separation of Greenland and North America.
Geochemistry and Petrology of the Loon Lake Pluton, Ontario
Authors: Dostal Jaroslav
Published: April 2011

The Precambrian Loon Lake pluton, Ontario, consists of two main zones—a core of monzonite with a rim of younger quartz monzonite. Several isolated bodies of older diorite and syenodiorite occur within the pluton. The variations in the chemical and mineralogical composition of diorites and syenodiorites are due to both magmatic differentiation and hybridization. The trends of the variations of major elements, Rb, Tl, Sr, Ba, and rare earth elements in monzonite are consistent with fractional crystallization mainly of feldspars; this fractionation probably involved flowage differentiation. Fractional crystallization and contamination of monzonitic magma by anatectic granitic melt probably played a dominant role in the genesis of quartz monzonite. Monzonite and quartz monzonite are believed to have formed from a magma of lower crustal or upper mantle origin. While part of this magma intruded as monzonite, another part which evolved further generated quartz monzonite.
Late Precambrian Shallow Water Deposits, Banks and Victoria Islands, Arctic Archipelago
Authors: Young G. M. , Jefferson C. W.
Published: April 2011

The upper Precambrian succession of the southern tip of Banks Island comprises about 900 m of sedimentary rocks intruded by thick gabbro sills. The lowest unit exposed is a cherty stromatolitic carbonate. This is overlain by a thicker unit of sandstones and mudstones. Most of the sequence is considered to be correlative with the Glenelg Formation, which is the basal formation of the late Precambrian Shaler Group of the Minto Arch on Victoria Island. A thick shale unit at the top of the Banks Island Precambrian succession may be correlative with the basal part of the Reynolds Point Formation on Victoria Island.Paleocurrent measurements from the Banks Island rocks indicate transport essentially to the northwest. An abundantly cross-bedded sandy limestone unit in the upper part of the Reynolds Point Formation in the Minto Inlet area of Victoria Island gives a polymodal paleocurrent pattern. This unit was probably deposited in a shallow marine environment under tidal influence. Tidalites have been recognized in the lower clastic unit of the Reynolds Point Formation at several localities in the Minto Arch. Stromatolites form the lower part of the Shaler Group suggest that these rocks are early Upper Riphean (latest Helikian to early Hadrynian). The stromatolite forms appear to occur in a non-repetitive sequence that provides a powerful means of intrabasinal correlation.The depositional area is envisaged as a large embayment of the sea, comparable in scale, shape, and sedimentary fill, to the younger Michigan Basin. The northwest margin of the basin is tentatively interpreted as a breached arch, shedding terrigenous clastics to the NW in the Banks Island area, and to the east at the north end of the Minto Arch. Northeasterly elongation of stromatolites in the upper Glenelg Formation at the north end of the Minto Arch may reflect tidal currents. Circulation in the basin became progressively restricted, culminating in deposition of the evaporite-bearing sequence of the upper part of the Shaler Group.
Use of Factor Analysis in Interpreting Genetic Processes in Lacustrine Soils of Ontario, Canada
Authors: Martini I. P. , Acton C. J.
Published: April 2011

A multivariate statistical technique, Q-mode factor analysis, was applied to 120 samples collected from five lacustrine soils of southwestern Ontario. In each sample, 23 variables were measured: 11 chemical, and 12 particle size classes. Three factors were found to account adequately for the variation in the original data, i.e. 120 samples × 23 variables. The factors can be interpreted as indicators of depositional and weathering environments. To simplify such an interpretation and to try and separate the effects of the depositional environment from the pedogenic processes, the chemical data was treated separately from the grain size data. Two factors were found to describe adequately the variation in chemical data and three factors accounted for the variation in the grain size data. The chemical factors were interpreted to represent the processes of weathering occurring in the soil profile. The grain size factors were postulated as representing energy levels in the environment of deposition of the parent materials, i.e. a low energy environment where the sediments were formed predominantly through settling from suspension, a relatively higher energy environment where a significant portion of the sediments were deposited from traction currents, and an intermediate energy level where both settling and traction were important processes. These interpretations were arrived at considering only laboratory data and they agree with morphological information obtained from the field.In the exploratory or preliminary stages of research, factor analysis is a useful tool for manipulating a large amount of data. This type of analysis can complement morphological studies that are still needed for a full understanding of the genesis and classification of soils.
Morphology and Structure of the Southern Labrador Sea
Authors: Egloff J. , Johnson G. L.
Published: April 2011

Geophysical surveys since 1971 and sounding data reveal the morphology and structures of the southern Labrador Sea. Ran Ridge and older mid-Labrador Sea crustal basement are well-defined. The West Thulean Rise (pre-60 Ma BP), counterpart to the Thulean Rise of the Northeast Atlantic, extends between the Charlie Fracture Zone and Ran Ridge {anomaly 24). Topographic and basement structural relief along a fault (herein called the Leifur Eiriksson Fracture Zone), offsetting the Ran Ridge crest (60–45 Ma BP) at 57 °N, 45 °W, is correlated with magnetic anomaly trends. The pre-Thulean and Thulean time structures of the mid-ocean ridge and magnetic data isochrons define the initial spreading orientations of the Ran/Reykjanes Triple Junction. Seismic data extend the known area of the transparent, kilometre-thick sedimentary body in the southern central Labrador Sea, and a circular trend of elongate crests surrounding a vortex region lend definition to the proposed name, Gloria Drift. Dunal morphology is characteristic of the surface of the entire Gloria Drift, and is also revealed in the mid-layer (35 Ma BP) extending throughout the entire sediment blanket. Terrigenous clay deposits sculpted by the Northeast Atlantic Deep Water form the elongate drift crests. The crests mark the paths or perimeters of the moving and still water masses of the bottom water gyre and probable anticlockwise paleocirculation that developed the Gloria Drift. The Imarssuak Mid-Ocean Channel is controlled by mountains and lies within the presumed relic rift valley of Ran Ridge. The Deep Sea Drilling Project at site 113 on the flood plain of Imarsuak Channel recovered cores consisting of turbidite silts and sands, mixed with volcanogenic (Iceland?) materials, and heavy minerals and clay. At this site, the commencement of transport in the channel is correlated with the onset of glaciation in early Pliocene. North of the junction with Imarssuak Channel, the Northwest Atlantic Mid-Ocean Channel lacks the high reflectivity indicative of recent (Pleistocene) turbidite deposition; hence, we conclude that the main source for highly reflective turbidite silts and sands in the lower Northwest Atlantic channel is the Imarssuak Channel. Meanders in the Northwest Atlantic Channel between 52 °N and 56 °N compare almost equally in proportions of channel widths and meander wavelengths, to the northeast Atlantic's Maury Channel at the same latitude.
Lake Agassiz deposits in the main offshore basin of southern Manitoba
Authors: Teller James T.
Published: April 2011

The lowlands adjacent to the Red River Valley were flooded whenever Quaternary glaciation dammed the northward-draining river systems of the region. The most recent impoundment, referred to as Lake Agassiz, began shortly before 13 500 years BP, as late Wisconsinan ice retreated northward in the Valley for the last time. In southern Manitoba, three fine-grained lacustrine units, numerous beach deposits, and an extensive area of fluvio-lacustrine (deltaic) sediment were deposited in and around the main depositional center of the Lake Agassiz basin during the life of the lake.The oldest offshore deposit of Lake Agassiz (Unit 1) is a silty clay containing ice-rafted clasts of till, clayey silt, and rock. Most of the silty and sandy sediment of the Assiniboine Delta also was deposited at this time. A readvance of ice into the northern and eastern Lake Agassiz basin, about 9800 years ago, caused a new influx of ice-rafted sediment into the offshore silty clays of southern Manitoba. Clast-rich Unit 2 was deposited at this time along the northern and eastern margins of the basin. When the ice retreated from the area shortly after 9800 years BP, lake levels dropped, and siltier, better laminated, and relatively clast-free Unit 3 was deposited. Units 1, 2, and 3 in southern Manitoba are correlated, respectively, with the Brenna Formation, lower part of the Sherack Formation, and upper part of the Sherack Formation of Lake Agassiz in North Dakota and Minnesota. Lake Agassiz deposition continued in southern Manitoba until after 8700 years BP.
Fold structures, southern Stoke Mountain area, Eastern Townships, Québec: Taconic or Acadian?
Authors: Robinson S. D. , Fyson W. K.
Published: April 2011

Fold structures in Cambro-Ordovician schists of the Stoke Mountain complex are compared with similar structures in adjacent Middle Ordovician and Siluro-Devonian slaty rocks. Schistosity in the complex lies parallel to the axial surfaces of obscure F1 folds. F2 isoclines in the schistosity and first generation isoclinal folds in bedding within the Siluro-Devonian rocks are essentially coplanar and coaxial; both are steeply inclined and plunge dominantly northeast. Parallel folds in Middle Ordovician and younger rocks apparently pass upward into Siluro-Devonian strata. Hence the F2 folds are plausibly correlated with those in the Siluro-Devonian rocks, which are of Acadian (mid-Devonian) age. Nevertheless, the steeply inclined F2-type folds in the Middle Ordovician rocks can be traced northeast along the Appalachians to localities where they are truncated by an angular unconformity beneath Siluro-Devonian rocks. It is evident that here the folds are not Acadian but late Ordovician (Taconic) structures.The conflicting evidence as to the age of the F2-type folds, which is not resolved by radiometric data, casts doubt on both local and regional correlations based on fold form and orientation.
The Eastport Formation (Lower Devonian) in the northern Passamaquoddy Bay area, southwest New Brunswick
Authors: Pickerill R. K. , Pajari Jr. G. E.
Published: April 2011

Previous interpretations of the stratigraphic position of a series of volcanic and sedimentary strata along the northern coast of Passamaquoddy Bay, New Brunswick, are somewhat enigmatic. Recent fieldwork has indicated that the sequence is a lithostratigraphic, biostratigraphic, and most probably a chronostratigraphic equivalent to the Eastport Formation (Gedinnian) of Maine, located a few kilometres to the west. It is proposed that henceforth, the succession be termed the Eastport Formation.
Submerged drainage patterns in Barrow Strait, Canadian Arctic
Authors: Bornhold Brian D. , Finlayson Nancy M. , Monahan David
Published: April 2011

Recent detailed bathymetric maps of Barrow Strait enabled a reconsideration of the Tertiary fluvial erosion model used to account for the physiography of the Canadian Arctic Archipelago. Five distinct drainage basins were distinguished within Barrow Strait, including both dendritic and rectangular drainage patterns. The latter were controlled by normal faults along the Precambrian–Paleozoic contact in Peel Sound and Barrow Strait.Several changes in the original model are proposed, including the placement of the main east–west drainage divide through Somerset Island and across Barrow Strait and southern Wellington Channel to Devon Island.
Kelp, methane, and an impenetrable reflector in a temperate bay
Authors: Keen M. J. , Piper D. J. W.
Published: April 2011

St. Margaret's Bay is one of the bays of the Atlantic coast of Nova Scotia, which owes its present form to flooding as sea level rose following deglaciation. It has a central, rather flat, deep basin, separated from the shelf by a sill. Two metres or so below the central basin floor lies a prominent acoustic reflector, not due to lithological changes within the sediment. We suggest that this is caused by gas, in part at least methane. Methane content increases with depth in sediment cores, and could be present in gaseous form (not just dissolved). There is a concomitant decrease in organic carbon with depth, and it appears that a part of this carbon is responsible for the generation of methane under reducing conditions below 2 m or so. The source of the organic carbon could be kelp, produced in abundance in the Bay, which has a very high primary productivity.
A grizzly bear from the Middle Wisconsin of Woodbridge, Ontario
Authors: Churcher Charles S. , Morgan Alan V.
Published: April 2011

The distal end of the left humerus of a grizzly bear, Ursus arctos, has been recovered from above the Early Wisconsin Sunnybrook Till at Woodbridge, Ontario, from the same horizon that previously has yielded remains of the woolly mammoth, Mammuthus primigenius. The age of these specimens is estimated at 40 000–50 000 years BP, within the mid-Wisconsin, Port Talbot Interstadial. The only other recognized Canadian record of a grizzly bear east of Manitoba is from a gravel sequence at Barrie, near Lake Simcoe, Ontario, dated from a bone fragment to 11 700 ± 250 years BP. A specimen recovered in Toronto in 1913 from an Early Wisconsin horizon is also considered to represent the grizzly. Bears of the grizzly type, Ursus arctos-horribilis were present in Ontario before and after the Early and Late Wisconsin ice advances.
Crossitic amphibole and its possible tectonic significance in the Richmond Area, southeastern Quebec
Authors: Trzcienski Jr. W. E.
Published: April 2011

Crossitic amphibole suggesting blueschist-type metamorphism has been found in the Richmond area, southeastern Quebec. Prehnite facies metamorphism to the northeast of Richmond and greenschist facies metamorphism to the south along with the blueschist-type metamorphism and geophysical data suggest that the Richmond area may represent a partially eroded Ordovician subduction zone.
Cryostatic pressures in nonsorted circles (mud hummocks), Inuvik, Northwest Territories
Authors: Mackay J. Ross , MacKay D. K.
Published: April 2011

Experiments were carried out during the 1967–1972 period in an attempt to measure cryostatic (frost-induced) pressures by means of soil pressure cells installed in nonsorted circles (mud hummocks) at Inuvik, N.W.T. Although slight soil pressure increases were measured in the hummocks during the freeze-back period, the field evidence shows that the hummock centers became desiccated, overconsolidated, and immobile rather than saturated, underconsolidated, and mobile, because of water loss to growing ice lenses at the top and bottom of the active layer. Cryostatic pressures during the freeze-back period are considered to be no more important than thaw displacement in the summer. The Inuvik mud hummocks appear to maintain considerable stability and individual identity over a time span of hundreds of years.
Coastal environments and oil spill residues in Chedabucto Bay, Nova Scotia
Authors: Owens E. H. , Rashid M. A.
Published: April 2011

Investigations following the oil spill from the tanker ARROW in Chedabucto Bay, Nova Scotia, in 1970 have focussed on the physical and chemical degradation of the Bunker C oil in different littoral environments and on the effects of sediment removal to restore polluted beaches. Natural processes have restored the beaches effectively on coasts exposed to wave activity. In sheltered, low-energy areas, the oil has undergone relatively little change over the 3-year period and is still present in the littoral zone. The removal of contaminated sediments from exposed beaches has not caused major changes but has resulted in permanent retreat of the beach crest in areas of limited sediment supply.
Early Aphebian basaltic volcanism in the southern District of Keewatin, Northwest Territories
Authors: Beavon Roy V.
Published: April 2011

A thin formation of folded mafic flows resting unconformably on Archean basement is informally named the Spi Lake basalt. Stratigraphic, structural, and textural evidence suggests that these lavas were probably fed from a diabase dike swarm dated at 2250+ m.y. by the Geological Survey of Canada. The Spi Lake basalt is overlain by conglomerate that may represent the base of the Hurwitz Group.
Ring complexes of the Peruvian Coastal Batholith: a long-standing subvolcanic regime
Authors: Bussell M. A. , Pitcher W. S. , Wilson P. A.
Published: April 2011

A special feature of the composite Coastal Batholith of Peru is the presence of ring complexes, which suggests a very high-level crustal environment and a direct connection between the magmas of the constituent plutons and caldera-centred volcanicity. The nature of four such complexes is commented on in detail, especially the high degree of structural control of emplacement, the association of mylonites and tuffisites with ring-fractures, the roles of stoping, fluidization and entrainment during the intrusion of ring-dykes, the co-existence of highly mobile magmas, their pulsatory injection, and the connection between these and volcanics of the same general age. Such mechanisms of cauldron subsidence located at the plutonic–volcanic interface operated throughout much of the 70 m.y. history of the batholith.
Further paleomagnetic results from the Michikamau Intrusion, Labrador
Authors: Emslie R. F. , Irving E. , Park J. K.
Published: April 2011

Newly available isotopic age measurements and paleomagnetic results on rocks of the Michikamau Intrusion and its surroundings have made possible more precise estimates of the position and age of the paleomagnetic pole. Results from six new collecting localities, when combined with results from six different collecting localities reported earlier, provide a pole position at 1½° S, 142 °W(A95 = 4½°). The age of crystallization of the intrusion is about −1460 Ma and the age of the pole is shown to be about −1450 Ma. The remanence is caused by fine grained, titanium-free magnetite and hematite.
Gravity study of an Archean granitic area northwest of Ignace, Ontario
Authors: Szewczyk Z. J. , West G. F.
Published: April 2011

A gravity survey has been made over a predominantly granitic terrain in the Wabigoon volcanic–plutonic subprovince of the Superior Province of the Canadian Shield. To supplement the preexisting regional coverage, 410 new gravity stations were established with an accuracy in the Bouguer gravity of about one milligal. The main feature of the area is a large negative anomaly that occurs over the Basket Lake granodiorite-to-quartz-monzonite intrusion. Suprisingly, no similar anomaly is found over a somewhat similar pluton (the Indian Lake intrusion) which is located about 20 km southeast of the Basket Lake body.Density studies show that both intrusions are lighter than the surrounding gneissic rocks. Gravity model studies indicate that the density contrast at the edge of the Basket Lake intrusion must extend to a depth of about 8 km, whereas the density contrast associated with the Indian Lake intrusion extends only to about 2 km depth. The difference between the intrusions can be correlated with their geological characteristics, the latter being more potassic and more uniform than the former, and sometimes feldspar porphyritic. The Indian Lake intrusion is thus interpreted as a relatively late, post-kinematic intrusion, exposed near its laterally expanded top. The Basket Lake intrusion is interpreted as a synkinematic, mezozonal to catazonal batholith of typical Archean type.
Single-domain theory for the reversible effect of small uniaxial stress upon the initial magnetic susceptibility of rock
Authors: Hodych J. P.
Published: April 2011

The phenomenon of small uniaxial stress changing the magnetic susceptibility of rock is of current interest as a possible aid in earthquake forecasting.In this paper, theoretical expressions are derived (using rigorous energy-minimization, but ignoring thermal activation) for reversible susceptibility change parallel to the stress axis for samples containing single-domain grains of a ferromagnet with cubic magnetocrystalline anisotropy (K1, positive or negative) and anisotropic magnetostriction. The grains are assumed to be non-interacting and randomly oriented spheres or ellipsoids of revolution elongated along [Formula: see text], [Formula: see text] or [Formula: see text]. Also, approximate expressions are given for samples containing multidomain grains with very strongly pinned walls.For susceptibility change perpendicular to the stress axis, one expects −½ the above expressions, which is proven for spherical single-domain grains with isotropic magnetostriction using a magnetometer analogy.The expressions predict that for magnetite-bearing rock the decrease in susceptibility along a 100 bar compression axis should be 4.7% for spherical single-domain grains (coercive force ~100 Oe), 1.6% for 1.4 to 1 elongation along [Formula: see text] (coercive force ~500 Oe), and 0.6% for great elongation along [Formula: see text]. The decrease for equidimensional multidomain grains with strongly pinned walls (coercive force ~100 Oe) should be ~1.2%—less at smaller coercive force according to some theoreticians, possibly more according to my experiments.
Transcurrent motion determined paleomagnetically in the Northern Appalachians and Caledonides and the Acadian Orogeny
Authors: Morris W. A.
Published: April 2011

After correction for Mesozoic and Tertiary opening of the Atlantic, Ordovician and Silurian – Lower Devonian paleomagnetic poles from Britain are significantly different to contemporaneous results from North America. Upper Devonian poles from the two regions are similar. The discrepancy observed in the Ordovician and Silurian – Lower Devonian data is interpreted as due to major sinistral transcurrent faulting during the Middle Devonian concurrent with the short lived Acadian Orogeny. Rate of motion on this fault (or faults) was approximately 9 ± 4 cm/y. A consequence of this interpretation is that the Caledonide ocean was apparently narrow during the interval Ordovician to Devonian. However, inaccuracies in the paleomagnetic data permit the opening and closing of small ocean basins (≤ 1000 km), which may be related to the more extended Taconic Orogeny.