bluuebunny/crossref_metadata_2025 huggingface dataset:
Illinoian to Late Wisconsinan stratigraphy at Woodbridge, Ontario
Authors: Karrow P F , McAndrews J H , Miller B B , Morgan A V , Seymour K L , White O L
Published: April 2011

Near Woodbridge, northwest of Toronto, Ontario, a 15 metre-high railroad cut and associated borrow pit, first excavated in 1962, exposed a multiple till sequence and intervening fossiliferous sediments. Work over the next 35 years revealed that Illinoian York Till, early Wisconsinan Sunnybrook Till, and late Wisconsinan Humber till, Halton Till, and Wildfield Till are interbedded with fossiliferous sediments equivalent to the Sangamonian Don Formation, early Wisconsinan Scarborough Formation (>50 ka BP), and middle Wisconsinan Thorncliffe Formation (45 ka BP). A complex periglacial record displays multistage fossil frost wedges, indicating intervals of severe climate in late Illinoian and early Wisconsinan time. Cored boreholes indicate deep gravel below and a till on Ordovician shale bedrock (Georgian Bay Formation). Vertebrates, molluscs, ostracodes, insects, and plants (diatoms, wood, seeds, pollen) indicate mostly cool conditions (boreal to tundra) for interstadial sediments. Interglacial conditions are represented by vertebrates, molluscs, and plants above York Till. Many taxa are new to the Quaternary of the Toronto area.
Palaeoenvironmental reconstruction of the Port Moody Interstade, a nonglacial interval in southwestern British Columbia at about 18 000 14C years BP
Authors: Lian Olav B , Mathewes Rolf W , Hicock Stephen R
Published: April 2011

New palynological data from peaty sediments deposited during the Port Moody Interstade, at about 18 000 14C years, indicate that the environment in the western Fraser Lowland of British Columbia consisted of subalpine forest and parkland with abundant fir and spruce that grew under a temperate and moist climate, similar to the wetter subzones of the present-day Engelmann Spruce  Subalpine Fir biogeoclimatic zone. The moist conditions interpreted for the Port Moody Interstade are consistent with recent computer modelling and earlier palynological data from unglaciated western Washington State, but appear to contradict regional Cooperative Holocene Mapping Project (COHMAP) reconstructions and some earlier palaeoenvironmental studies that support dry conditions. Strong seasonality is suggested as part of the explanation, with Pacific storms in summer following the southern margin of the last Cordilleran ice sheet, bringing abundant moisture to the study area during the growing season, but probably not in winter, when storm tracks were displaced to the south. The cold and dry anticyclonic winds postulated by COHMAP were probably also relatively weak in summer, resulting in stronger expression of moist Pacific air masses than previously thought. The timing of the Port Moody Interstade coincides with that of a short climatic fluctuation reported from several other sites in both the northern and southern hemispheres. These events, if causally related, suggest a rapidly propagated atmosphericoceanic signal.
The geochemical nature of the igneous rocks of the Sharbot Lake domain, Central Metasedimentary Belt, Ontario
Authors: Smith T E , Harris M J , Huang C H , Holm P E
Published: April 2011

Two bimodal mafic-silicic suites of igneous rocks, the Sharbot Lake volcanic rocks and the Lavant Igneous Complex, are identified geochemically in the Sharbot Lake domain of the Central Metasedimentary Belt in Ontario, and their genesis and thermotectonic environment are evaluated. The Sharbot Lake volcanic rocks comprise a series of basalts characterized by light rare-earth element (LREE) depletion and relatively high concentrations of Σ Fe2O3, TiO2, MnO, V, and Y, together with rhyolites and silicic pyroclastic rocks. They are intruded by rocks of the Lavant Igneous Complex, which comprises tholeiitic gabbros characterized by LREE enrichment and low concentrations of Σ Fe2O3, TiO2, MnO, V, and Y, and granitoid rocks. The trace element signatures of the mafic rocks of the Sharbot Lake volcanic sequences are most like those of back-arc tholeiitic basalts, and those of the Lavant Igneous Complex are comparable to those of low-K tholeiitic basalt suites. The trace element signatures of the silicic rocks associated with both suites are typical of those formed by crustal melting. Volcanic sequences with trace-element signatures very similar to those of the Sharbot Lake suites have been previously described in the Belmont and Grimsthorpe domains of the Central Metasedimentary Belt, suggesting that the three domains all belong to the Bancroft  Elzevir  Mazinaw  Sharbot Lake superterrane. The lithological, structural, and igneous characteristics of this superterrane suggest that it represents part of a complex back-arc basin underlain by areas of rifted and attenuated continental crust and oceanic crust.
Eocambrian granite clasts in southern British Columbia shed light on Cordilleran hinterland crust
Authors: Erdmer Philippe , Heaman Larry , Creaser Robert A , Thompson Robert I , Daughtry Ken L
Published: April 2011

The Spa Creek assemblage is a distinctive thin pericratonic succession that crosses the Okanagan Valley in the hinterland of the southern Cordilleran Orogen in Canada. The succession was ductilely deformed and metamorphosed before deposition of overlying Triassic dark metaclastic strata. A metaconglomerate within the succession, locally composed of more than 90% biotite granite clasts, yielded five fractions of euhedral zircon that define a precise UPb upper intercept of 555.6 ± 2.5 Ma, inferred to be the age of a nearby pluton. Other clasts in the metaconglomerate are generally more abundant, consisting of quartzite, amphibole schist, chlorite schist, sericite schist, biotite schist, and quartzfeldspar porphyry. They are likely host rocks of the pluton and, if so, are Late Proterozoic or older. The granite is interpreted as a terminal product of the Eocambrian rifting that preceded Paleozoic miogeoclinal sedimentation farther inboard. The continuity of pericratonic rocks west of the miogeocline and the occurrence of Proterozoic cratonic rocks at the surface west of the Okanagan Valley show that the ancient continental margin extends into a region where most of the crustal lithosphere was until now thought to consist of accreted Phanerozoic arc and accretionary complexes.
Apatite fission-track evidence of widespread Eocene heating and exhumation in the Yukon-Tanana Upland, interior Alaska
Authors: Dusel-Bacon Cynthia , Murphy John M
Published: April 2011

We present an apatite fission-track (AFT) study of five plutonic rocks and seven metamorphic rocks across 310 km of the YukonTanana Upland in east-central Alaska. Samples yielding ~40 Ma AFT ages and mean confined track lengths > 14 µm with low standard deviations cooled rapidly from >120°C to <50°C during a 35 Ma period, beginning at about 40 Ma. Data from samples yielding AFT ages >40 Ma suggest partial annealing and, therefore, lower maximum temperatures (~90105°C). A few samples with single-grain ages of ~20 Ma apparently remained above ~50°C after initial cooling. Although the present geothermal gradient in the western YukonTanana Upland is ~32°C/km, it could have been as high as 45°C/km during a widespread Eocene intraplate magmatic episode. Prior to rapid exhumation, samples with ~40 Ma AFT ages were >3.82.7 km deep and samples with >50 Ma AFT ages were >3.32.0 km deep. We calculate a 440320 m/Ma minimum rate for exhumation of all samples during rapid cooling. Our AFT data, and data from rocks north of Fairbanks and from the Eielson deep test hole, indicate up to 3 km of post-40 Ma vertical displacement along known and inferred northeast-trending high-angle faults. The predominance of 4050 Ma AFT ages throughout the YukonTanana Upland indicates that, prior to the post-40 Ma relative uplift along some northeast-trending faults, rapid regional cooling and exhumation closely followed the Eocene extensional magmatism. We propose that Eocene magmatism and exhumation were somehow related to plate movements that produced regional-scale oroclinal rotation, northward translation of outboard terranes, major dextral strike-slip faulting, and subduction of an oceanic spreading ridge along the southern margin of Alaska.
Hidden Cretaceous basins in Nova Scotia
Authors: Stea Rudolph R , Pullan Susan E
Published: April 2011

Early Cretaceous unconsolidated quartz sand and kaolinitic clay deposits in the lowlands of Nova Scotia are preserved in narrow half-grabens obscured by glacial drift. The Chaswood Formation sediments can be subdivided into three members; upper and lower members dominated by cyclical sandmud facies of fluvial origin and the middle member with lignitic clay of lacustrine origin. Ferruginous oxisols are common in the fine-grained facies of the upper and lower members. Seismic data indicate that Chaswood Formation strata in the Elmsvale Basin are deformed into steeply dipping faults and fault-related folds (Rutherford Road fault zone). An AptianAlbian age for this tectonic event is inferred from synsedimentary deformation and from the angular unconformity spanning the Late Cretaceous and Tertiary that truncates the Chaswood Formation. Exhumation of a thick cover of Mesozoic sediment (12 km) is needed to account for the preservation of Chaswood Formation outliers after ~80 Ma of erosion. The half-grabens that host the Chaswood Formation were formed in the Mesozoic and were antecedent to the present-day structurally controlled lowlands.
New species of Silurian acanthodians from the Mackenzie Mountains, Canada
Authors: Hanke Gavin F , Wilson Mark VH , Lindoe L Allan
Published: April 2011

Two new acanthodian taxa are described. The ischnacanthid Xylacanthus kenstewarti is based on large, dentigerous jaws, and Granulacanthus joenelsoni is based on isolated spines. The isolated remains of these species are similar in that they both possess pustulose denticles or tubercles, either on the mesial ridge (X. kenstewarti) or on the fin spines (G. joenelsoni). Jaws of X. kenstewarti are similar in size to those of Xylacanthus minutus, Ischnacanthus kingi, and I. wickhami and smaller than those of X. grandis. The jaws of X. kenstewarti are most similar to those of X. minutus, but are distinguished from this and other ischnacanthid species by a tapering patch of pustulose denticles that is widest midway along the jaw, mesial denticles that are simple blisterlike structures, the monocuspid, striated primary teeth that are subcircular in cross section, and a posterodorsal process that is enlarged. The spines of G. joenelsoni have distinctive tubercular ornamentation. Tubercles, or nodular ornaments on fin spines, are characteristic of primitive acanthodians, but the slender shape of the spines, the low number of spine ribs, and the fine striations posterior to the main ribs of each spine suggest that G. joenelsoni is a relatively advanced acanthodian. Xylacanthus kenstewarti and G. joenelsoni are from the Silurian (Wenlock or Ludlow) of the southern Mackenzie Mountains. Xylacanthus kenstewarti represents the earliest representative of the genus, the earliest unequivocal remains of a gnathostome from the Mackenzie Mountains, and extends the known geographical range of the genus from the Mackenzie Mountains east to Spitsbergen.
A condensed Lower to Middle Ordovician graptolite succession at Matane, Quebec, Canada
Authors: Maletz Jörg
Published: April 2011

The highly condensed Lower to Middle Ordovician deep-water succession from the Cap-des-Rosiers Group at Matane bears three conspicuous graptolite faunas of late Tremadoc to mid-Darriwilian age. The Tremadoc fauna belongs to the Aorograptus victoriae Zone. In the Castlemainian Isograptus victoriae maximodivergens Zone fauna the earliest Pseudisograptus species, Pseudisograptus initialis n. sp., appears together with the ancestral Arienigraptus gracilis. A Darriwilian fauna with Holmograptus spinosus and Bergstroemograptus crawfordi represents the youngest pre-Nemagraptus gracilis Zone fauna described from the Quebec Appalachians.
ORIGIN OF GYPSUM-ANHYDRITE DEPOSITS AT FALKLAND, BRITISH COLUMBIA
Authors: Baird D. M.
Published: April 2011

An unusual occurrence of gypsum-anhydrite at Falkland, British Columbia, that supplied more than 1 250 000 tons of commercial gypsum between its opening in 1926 and its closing in 1956, has been considered to be of hydrothermal replacement origin. Evidence is here presented to show that the gypsum-anhydrite bodies were originally deposited as part of a sedimentary sequence and that they have "intruded" into their present positions as lenses and smears by plastic mobility along well-marked fault zones that supplied avenues of migration rather than conduits for sulphate-rich solutions.
THE ROCKY MOUNTAIN TRENCH: A PROBLEM
Authors: Crickmay C. H.
Published: April 2011

The Rocky Mountain Trench is defined as the 1 000-mile valley which marks the west side of the Canadian Rocky Mountains. The background of the Trench as a problem is examined, and descriptions, geographical and geological, are given. Previous work on Trench origin is reviewed and note is taken of the seeming inapplicability of accepted erosion theories to the making of the erosion-made Trench. An hypothesis is offered in which the combined action of drainage hemmed in by bordering uplifts, guided headward erosion, lateral corrasion, and streams repeatedly reversed by continuing diastrophism is suggested as the excavator of the Trench, a valley characterized by the puzzling peculiarity of continuous depth without a consistent gradient.
THE PROBLEM OF THE WILLOW CREEK FORMATION
Authors: Russell Loris S.
Published: April 2011

The Willow Creek formation of south western Alberta is known to include both Upper Cretaceous and Paleocene deposits in the disturbed belt of the foothills. On the plains to the east, however, the Cretaceous portion may be absent, and the formation may rest unconformably on the underlying late but not latest Cretaceous St. Mary River formation.
COMPARISON OF CHEMICAL COMPOSITION OF SOILS AND BEDROCK OF MONT ST. HILAIRE, QUEBEC
Authors: Webber G. R. , Jellema J. U.
Published: April 2011

Soil samples from Mont St. Hilaire, one of the Monteregian Hills of Quebec, were analyzed by X-ray fluorescence for the elements Fe, Ca, K, Ti, Mn, Sr, Zr, Nb, Zn, and Rb. The samples were taken below the surface organic-rich horizon.The composition of the parent material was calculated by comparing the soils with local rocks having similar Ti/Zr ratios, assuming that the Ti/Zr ratio has not changed appreciably during the soil-forming process. This comparison indicates that there has been little change in the concentration of most of the elements during weathering. Average ratios of concentration in soils to concentration in calculated parent material for the elements were Fe 1.25, Nb 1.11, Ca 1.08, Rb 1.07, Zn 1.02, Zr 0.96, Ti 0.94, Mn 0.82, Sr 0.69, K 0.54; that is, Fe showed a tendency to accumulate, and K, Sr, and possibly Mn showed a tendency to be depleted in the soils.The areal distribution of elements in the soils is in general agreement with what is known of the distribution of syenitic and essexitic intrusive rocks which make up most of the mountain.
ARCHAEAN VOLCANISM IN THE CANADIAN SHIELD
Authors: Wilson H. D. B. , Andrews Peter , Moxham R. L. , Ramlal K.
Published: April 2011

Chemical compositions of Archaean volcanic rocks in the Superior province of the Canadian shield have been determined from 261 new analyses from 10 volcanic belts. The analyses are compared with those of the various volcanic associations. This comparison shows that the volcanic rocks of all belts belong to the basalt andesite rhyolite association typical of continental orogenic belts or island are systems. A primitive continent with continental rocks must, therefore, have existed in early Archaean time.The Keewatin lava sequences in the various belts are remnants of a great volcanic sequence that covered the southern half of the Superior province of the Canadian shield.
DEFINITION AND MEASUREMENT OF LOSSES IN HYDRAULIC HEAD AROUND A WELL BORE
Authors: Nind T. E. W.
Published: April 2011

A differentiation is made between two types of loss in head. The first results from the alteration in the transmissibility of the permeable formation in the immediate vicinity of the well bore. This alteration is caused by the process of drilling and completing the well. The skin factor is a measure of resultant head loss, and methods for evaluating this well parameter are discussed. The second type of well loss is caused by turbulent flow in the formation close to the well, and is commonly evaluated by a step-drawdown test. The interpretation of such tests is investigated, and a method of analysis is proposed which is believed to have a theoretically sounder basis than that commonly employed.
STRUCTURE, STRATIGRAPHY, AND PALEONTOLOGY OF AN UPPER TRIASSIC SECTION ON THE WEST COAST OF BRITISH COLUMBIA
Authors: Carlisle Donald , Susuki Takeo
Published: April 2011

The highly deformed section at Open Bay is one of the few good exposures of a thick sedimentary unit within the prebatholithic rocks along coastal British Columbia. It provides new structural information relating to emplacement of a part of the Coast Range batholith and it contains an important Upper Triassic fauna unusually well represented. Structural and paleontological analyses are mutually supporting and are purposely combined in one paper.Thirteen ammonite genera from 14 localities clearly substantiate McLearn's tentative assignment to the Tropites subbullatus zone (Upper Karnian) and suggest a restriction to the T. dilleri subzone as defined in northern California.Contrary to an earlier view, the beds are lithologically similar across the whole bay except for variations in the intensity of deformation and thermal alteration. Their contact with slightly older relatively undeformed flows is apparently a zone of dislocation. Stratigraphic thicknesses cannot be measured with confidence, and subdivision into "Marble Bay Formation" and "Open Bay Group" cannot be accepted. Open Bay Formation is redefined to include all the folded marble and interbedded pillow lava at Open Bay. Lithologic and biostratigraphic correlation is suggested with the lower middle part of the Quatsino Formation on Iron River, 24 miles to the southwest. Basalt flows and pillowed volcanics west of Open Bay are correlated with the Texada Formation within the Karmutsen Group.The predominant folding is shown to precede, accompany, and follow intrusion of numerous andesitic pods and to precede emplacement of quartz diorite of the batholith. Structural asymmetry is shown to have originated through gentle cross-folding and emplacement of minor intrusives during deformation.
GEOMAGNETIC "DEPTH-SOUNDING" AND THE COAST EFFECT IN WESTERN CANADA
Authors: Lambert A. , Caner B.
Published: April 2011

During 1964 an east–west geomagnetic recording profile was operated in western British Columbia to investigate the "coast effect" in geomagnetic variations. The profile extends earlier work by Hyndman in central and eastern British Columbia. Results of the survey are described and interpreted. The restraints imposed on the choice of models have been based primarily on compatibility with other geophysical information, rather than on agreement with idealized theoretical conductivity structures.The "coast effect" has been interpreted as being due to two different effects: the land–sea interface at periods of less than 10–15 minutes, and an associated upper mantle structure at periods of more than 30 minutes. The latter has been tentatively identified with the discontinuity of the seismic low-velocity layer under continental and oceanic regions.On the basis of additional geophysical information, the interpretation has been extended to include the anomalies in the southwest United States reported by Schmucker in 1964. The inland anomalies in western North America have been interpreted on the basis of a moderately conducting zone at the top of the mantle, tentatively identified with the anomalous seismic low P velocity zone. If confirmed by further observations, these results imply temperature rather than density effects as the cause of the low P velocities.
VARIATIONS IN SHORT-PERIOD RECORDS FROM CANADIAN SEISMOGRAPH STATIONS
Authors: Ichikawa M. , Basham P. W.
Published: April 2011

A study of the relative recording ability of some of the Canadian seismograph stations has indicated a pattern of P-wave amplitude anomalies varying from station to station and, at any one station, showing a significant regional variation which does not seem to be entirely produced by source mechanism effects. Rather local crustal effects appear important, and spectral studies indicate that significant effects can be produced in low velocity upper crustal layers. The initial investigation of early P-wave trains and theoretical models suggests that these crustal effects can best be examined by the use of apparent incident angles, and that spectral amplitude decrements change significantly from station to station, although this is unexplained.It appears that the different recording ability of stations can be explained by a combination of shallow crustal effects operating on the signal amplitude and the local noise properties.
GLACIAL HISTORY OF NORTHEASTERN ONTARIO: I. THE COCHRANE–HEARST AREA
Authors: Boissonneau A. N.
Published: April 2011

Surficial deposits, ice movements, and glacial lakes are described for an area of 42 000 square miles in northeastern Ontario. Field studies and air photograph interpretation suggest the following sequence of events. A major fan-shaped advance of an ice mass over the study area. This was followed by the withdrawal of the ice mass from the area and the formation of proglacial lakes. This ablation phase was followed by a minor readvance. Two phases are postulated for this 'Cochrane' readvance. Within the study area, the extent of the glacial lakes and the limits of extension of the Cochrane readvance are postulated. A maximum water plane, location, and maximum elevation of outlet and amount of differential uplift of sediments are postulated for glacial Lake Barlow–Ojibway.
VARIATIONS IN SPECTRA OF P WAVES RECORDED AT CANADIAN ARCTIC SEISMOGRAPH STATIONS
Authors: Utsu Tokuji
Published: April 2011

To investigate the effects of location of a seismograph station on the records obtained, P waves from seismograms of Alaskan earthquakes recorded at four Canadian Arctic stations, Coppermine, Mould Bay, Resolute, and Alert have been analyzed spectrally. Differences in spectral amplitude at very low frequencies among the stations and between earthquakes can reasonably be explained by a consideration of earthquake magnitude, epicentral distance, and mechanism. Differences in the shape of the spectral curves between stations result mainly from local crustal structures beneath the station. Increased absorption of waves is observed beneath Resolute. Use of the vertical to radial-horizontal spectral amplitude ratios gives an approximate estimate of the thickness of the crust and surface layer beneath these stations, although some phenomena noted cannot be explained by the theory of signal reverberation in a horizontally layered system with perfect elasticity. This analysis suggests that the crust thins toward the Arctic Ocean: the best estimates of crustal thickness are about 45 km at Coppermine, about 33 km at Resolute, about 23 at Alert, and about 18 km at Mould Bay. The latter depth is the most uncertain. There is a low velocity surface layer with a thickness of several hundred meters at Mould Bay, Resolute, and Alert.
MAPPING GLACIER TERMINI IN SOUTHERN ALASKA, 1931–1964
Authors: Field William O.
Published: April 2011

A program to map changes in the positions of glacier termini in the coastal mountains of southern Alaska was initiated by the author in 1931, and since 1941 has been sponsored by the American Geographical Society. Wherever possible, stations previously used for surveys or photography were reoccupied, including a few established as early as the 1880's. After nine field trips, 50 triangulation networks have been established to cover 76 different termini of large and small glaciers, of which 26 are tidal. Photographs were taken from the principal stations to record changes in the topography and vegetation cover. The principal glaciers of Glacier Bay in southeastern Alaska and of Prince William Sound in southcentral Alaska have been surveyed five times.The surveys, supported by the photographic record, have documented pronounced advances of 8 termini and appreciable recession of 37; the remaining glaciers have either oscillated or remained virtually unchanged. The reason for the program, the instrumentation and procedures, and the field problems encountered are discussed, and recommendations are made for the future.
ANALOGUE MODEL MEASUREMENTS FOR ELECTROMAGNETIC VARIATIONS NEAR A COASTLINE
Authors: Dosso H. W.
Published: April 2011

An analogue model for studying the behavior of the natural geomagnetic and telluric field variations for the coastline problem is discussed. Measurements of amplitudes and phases for the horizontal electric, the horizontal magnetic, and the vertical magnetic field components for sloping earth–sea interfaces and for a sea over an upwelling conducting zone within the mantle in the form of a step are discussed for both the E and the H polarizations.
EFFECTS OF SURFICIAL GEOLOGY ON STREAMFLOW DISTRIBUTION IN SOUTHERN ONTARIO
Authors: Ayers H. D. , Ding John Y. H.
Published: April 2011

The monthly streamflow distribution on four pairs of watersheds in southern Ontario was investigated. The dominant parent geological materials on the four pairs of watersheds were as follows: A, coarse-textured soils; B, moderately fine-textured soils formed on very fine sands and silts; C, medium-textured soils formed on till; D, fine-textured soils formed on till. The March–April runoff from the watersheds of fine-textured soils (D) was 56% of the annual runoff over a 9-year period, and from the watersheds of coarse-textured soils (A) it was only 34% of the annual runoff during the same time period. Larger amounts of groundwater recharge on watersheds of coarse-textured soils resulted in higher summer flows, more uniform seasonal flow, and reduced spring runoff extremes.The groundwater daily recession constant was likewise higher for the streams draining coarse-textured soils. The average estimated equivalent groundwater storage remaining when the monthly discharge was at a rate that was exceeded for 90% of the time, was as follows for the four geological classes: A, 0.267 in.; B, 0.090 in.; C, 0.035 in.; D, 0.007 in.
THE PALAEOMAGNETISM OF THE SUDBURY DIABASE DYKE SWARM
Authors: Larochelle A.
Published: April 2011

Previously published results on the palaeomagnetism of the Sudbury diabase dyke swarm had indicated that these dykes were formed at low palaeomagnetic latitude. A new and independent set of data described in the present study confirms this view and suggests further that the dykes were not disturbed significantly since the time of their intrusion, over 1 000 m.y. ago. It is also suggested that the dykes sampled were intruded intermittently over a period extending for less than 10 000 years.
PALEOMAGNETIC EVIDENCE ON THE GENESIS OF THE HARD HEMATITE ORE DEPOSITS OF THE VERMILION RANGE, MINNESOTA
Authors: Symons D. T. A.
Published: April 2011

Paleomagnetic measurements using standard methods were made on 55 samples of hard hematite iron ore and associated host rocks that were collected from along the surface exposure, and from underground in the Pioneer Mine at Ely and in the Soudan Mine at Soudan, on the Vermilion Range, Minnesota, U.S.A. The unaltered host rocks have a stable pre-folding remanence of probable Keewatin age, whereas the ore and adjacent altered host rocks have a stable post-folding remanence of possibly Early to Middle Keweenawan age. This result indicates that the ore originated as a post-folding epigenetic deposit.
EXAMPLES OF NATURAL PHOTOGRAPHY FROM RENFREW COUNTY, ONTARIO
Authors: Saull V. A.
Published: April 2011

Blue-green algae grow on water-covered carbonate bedrock in the Bonnechere River 2 miles (3.2 km) northwest of Eganville, Renfrew County, Ontario. The algal growth is sunlight-controlled, and the growth patterns are photographic records of present-day solar radiation at the field site. Equivalent patterns may be identifiable in ancient rocks, and if so, could be used to determine paleodirections, and possibly paleolatitudes as well.
ANALYSES OF SILICATE ROCK AND MINERAL STANDARDS
Authors: Goldich S. S. , Ingamells C. O. , Suhr N. H. , Anderson D. H.
Published: April 2011

Bulk chemical analyses including some minor constituents are reported for six standard silicate rocks available from the U.S. Geological Survey. In addition to the conventional rock analyses, determinations of a number of constituents have been made by various instrumental methods. Three new standard mineral samples are available from The Pennsylvania State University. These include albite from Amelia County, Virginia; adularia from Val Cristallina, Switzerland; and pyroxene from near Libby, Montana.
UPPER MANTLE STRUCTURE IN CANADA FROM SEISMIC OBSERVATIONS USING CHEMICAL EXPLOSIONS
Authors: Barr K. G.
Published: April 2011

Long-range seismic observations at the standard Canadian seismic stations, from chemical explosions in Hudson Bay and Lake Superior, are used to derive a P-wave velocity structure for the upper mantle. The coordinates of observed cusps are used to define the structural discontinuities. These discontinuities are at depths of 126 and 366 km, which agree closely with the depths of the S-wave velocity discontinuities deduced from surface-wave observations. The observations do not require a low velocity layer in the upper mantle.
STRUCTURAL IMPLICATIONS OF THE GRAVITY FIELD IN HUDSON BAY AND VICINITY
Authors: Innes M. J. S. , Goodacre A. K. , Weber J. R. , McConnell R. K.
Published: April 2011

The results of underwater gravity measurements of a reconnaissance nature in Hudson Bay and of regional gravity surveys over adjoining regions of the Canadian Shield and Hudson Bay Lowlands are presented in the form of a Bouguer anomaly map. The general anomaly pattern is discussed and an interpretation is presented. Analysis of anomaly profiles crossing Hudson Bay using seismic data for control, shows (1) that Paleozoic and recent sediments have little overall effect on the gravity field, and (2) that variations in depth to the crust-mantle boundary have little or no correspondence with variations in the gravity field. It is believed that the gravity variations are largely due to systematic density differences in the Precambrian basement rocks. An important conclusion is that the more positive gravity field over the northern part of Hudson Bay marks a major change in structure and that the Churchill crustal block does not extend uninterruptedly eastward; it is suggested that the positive anomalies reflect high-density metamorphic gneiss or basic volcanic rocks underlying the sedimentary veneer. Evidence is presented which strengthens the hypothesis that the Kapuskasing gravity anomaly and its northern and southern extensions mark an ancient zone of crustal rifting of continental proportion.
OXYGEN AND CARBON ISOTOPIC COMPOSITION OF CARBONATES FROM THE JURA OF SOUTHERN GERMANY
Authors: Fritz Peter
Published: April 2011

The 18O/16O and 13C/12C ratios of about 250 dolomite and limestone samples from the Malm of Southern Germany were measured and the results have been compared with information obtained from microscopic studies.The dolomites were formed by dolomitization of marine limy sediments, more or less penecontemporaneously with the precipitation of the calcitic sediments, i.e. during Jurassic time. During post-Jurassic time these dolomites were partly dedolomitized. The distinction between a centrifugal and centripetal dedolomitization was possible and both occurred under the influence of circulating fresh-water. Centripetal dedolomitization leads very often to the formation of saccharoidal limestones, a process which probably is still going on today.
The tracing of hinge-line ore bodies in areas of repeated folding
Authors: Stauffer Mel R.
Published: April 2011

The location and depth to ore bodies lying along the hinge of either refolded or superposed folds can be determined by using simple geometric constructions. Methods are presented here for tracing hinge-line ore bodies for several common multiple fold situations.
Flood basalts, dike swarms and sub-crustal flow
Authors: Clifford Paul M.
Published: April 2011

A review of published data on flood basalts and diabase dike swarms suggests that they are related in origin, typically being developed in zones of crustal tension induced by sub-crustal flow. Perhaps, therefore, these basaltic effusions may be used to map convective cells in the mantle for various periods during geologic time. The inferred pattern of sub-crustal movements, particularly for the southern continents, is seen to be complicated, both temporarily and spatially, and is strongly suggestive of unsteady motion. Dikes of the Canadian Shield permit inferences about the site of convective cells back to 2150 million years.
Ephedralean pollen from the Upper Cretaceous Edmonton Formation of Alberta (Canada) and their paleoecological significance
Authors: Srivastava Satish K.
Published: April 2011

Four form-genera viz. Equisetosporites, Gnetaceaepollenites, Steevesipollenites, and Singhia are distinguished from each other and seven new species belonging to three of these genera are described. A new genus Singhia is erected to accommodate polyplicate ephedralean pollen having branched ridges.An ephedralean affinity with the four form-genera mentioned above is discussed. The modern species of Ephedra are mostly distributed in arid zones but their habitat varies considerably. Ephedra being anemophilous, its pollen can be carried long distances by wind. The fossil occurrence of ephedralean pollen may not be of significance in interpreting local paleoecology.
Geology and geochemistry of the Blue Mountain nepheline syenite
Authors: Payne John G.
Published: April 2011

The Blue Mountain nepheline syenite sill was formed from a nepheline syenite magma that intruded metasediments and syenite gneiss about 1300 m.y. ago. The magma was fractionated during emplacement into several zones, distinguished by their chemistry, mineralogy, and texture. Pegmatites were formed from late-stage fluids. Mafic bodies in the sill represent slabs of metasediments which were stoped from the roof of the sill by the magma, and which were plasticized and strung out into narrow sheets parallel to the direction of flow of the magma. Strong contortion of some sheets was produced by non-laminar flow of the magma around the included material. A contact aureole was developed above and to a minor extent below the sill; alkalies, alumina, water, and carbon dioxide were added to the metasediments from the magma.The sill and surrounding rocks were folded into their present positions during the Grenville orogeny about 1000 m.y. ago. Country rocks were recrystallized, but the rocks of most of the sill were only slightly affected by the metamorphism accompanying the orogeny.
A radiocarbon-dated marine algal bed of the Champlain Sea episode near Ottawa, Ontario
Authors: Mott R. J.
Published: April 2011

A bed of marine algae (seaweed) in a sand pit in Champlain Sea sediments southwest of Ottawa, Ontario, was dated by the radiocarbon method and gave an age of 10 800 ± 150 years (GSC-570). Marine shells from above and below the algal bed gave radiocarbon ages of 10 620 ± 200 years (GSC-587) and 10 880 ± 160 years (GSC-588) respectively.The algae and underlying shells have been excellently preserved as a result of rapid burial following deposition and remaining beneath a high water table. The similarity of the radiocarbon dates on the algae and on the shells above and below, and with previous dates on shells from other Champlain Sea deposits indicates the reliability of these shell dates.
The densities of Precambrian rocks from northern Manitoba
Authors: Gibb R. A.
Published: April 2011

To assist in the interpretation of gravity anomalies in northern Manitoba and northeastern Saskatchewan, a part of the western Canadian Shield, the average densities of 2004 Precambrian rock samples, grouped according to rock type, are tabulated. Relatively positive anomalies may be expected over greenstone belts (2.85 g/cm3), sedimentary gneisses (2.79 g/cm3), granulites (2.73 g/cm3), and mafic to ultramafic intrusions—diorite (2.77 g/cm3), gabbro (3.00 g/cm3), and peridotite (3.19 g/cm3), whereas negative anomalies may be expected over granitic rocks (2.64 g/cm3). These results are consistent with results from other areas.The average composition of a slab of surface rock in this part of the western Canadian Shield is shown to be granodioritic with an average density of 2.67 g/cm3.
Effects of diabase dike intrusion on sulfide minerals at Manitouwadge, Ontario
Authors: Graham R. A. F.
Published: April 2011

A diabase dike intruding a Cu-Zn massive sulfide orebody has caused a migration of copper and sulfur in the orebody towards the dike, but neither element penetrated the glassy chilled margins of the dike. This resulted in the development of a chalcopyrite-rich zone along the contact and a much broader zone of sulfur enrichment within which pyrrhotite was firstly sulfur enriched and then converted to pyrite and where the iron content of sphalerite was decreased.
A study of the isotopic abundance of boron from various sources
Authors: Agyei E. K. , McMullen C. C.
Published: April 2011

The absolute ratio of 11B/10B has been determined for boron from different terrestrial sources with a precision of 0.2% (two standard errors) and a reproducibility of 0.2% (half-range). Values fall in the range 4.108 to 3.987 (i.e. 3% variation) and give a corresponding range in the boron atomic weight of 10.814 to 10.810 (0.04% variation). The absolute ratios are 7% lower than those reported by early workers, but are in accord with the results of recent investigations. Igneous rocks and boric acid are found to have high isotopic ratios, whereas Tokyo Bay water possesses a value for 11B/10B near the mean.
Isotopic ages from the Appalachians and their tectonic significance: Reply to J. G. Dennis
Authors: Harper C. T.
Published: April 2011

The K–Ar isotopic data indicate that two major periods of post-metamorphic uplift and cooling occurred in the Northern Appalachians, the first during Late Ordovician and Silurian times, the second during the Late Devonian Epoch. These recorded events were separated by the Acadian magmatic episode.
The paleomagnetism of the Michikamau anorthositic intrusion, Labrador
Authors: Murthy G. S. , Fahrig W. F. , Jones D. L.
Published: April 2011

Twenty-nine oriented cores have been collected from six sites in the Michikamau Intrusion in Labrador. This had previously been well dated at 1400 m.y. by the potassium–argon method. A fold test has been applied to the paleomagnetic results after alternating magnetic field demagnetization. The results suggest that the magnetization was acquired with the rocks in their present attitudes. The stability of the magnetization has been well tested and it is concluded that the observed magnetization is thermo-remanent and represents the direction of the earth's field at the intrusion at the time of its formation. The paleomagnetic pole position for the intrusion lies at 0.5° S, 144.7° W, with A95 = 5.6°. It is difficult to compare this result with most other Precambrian results from North America due to uncertainties in age equivalences. However, a comparison with recently published results from well-dated rocks from Colorado–Wyoming suggests there have been no large relative movements between this region and Labrador for the last 1400 million years.
A Pleistocene muskox (Symbos) from Dease Lake, British Columbia
Authors: Harington C. R.
Published: April 2011

A Symbos skull fragment from Pleistocene deposits of northern British Columbia constitutes the first record of that genus for the province. In Canada, remains of this large muskox have been collected previously in western Yukon and southeastern Saskatchewan. Most of the other known specimens have been found in Alaska and the central United States, and the Canadian occurrences help to link these two areas of Symbos range. Symbos was adapted to warmer surroundings than Ovibos—perhaps a steppe or parkland environment.
Magneto-telluric determination of upper mantle conductivity structure at Victoria, British Columbia
Authors: Caner B. , Auld D. R.
Published: April 2011

Magneto-telluric data were obtained at Victoria over a very wide range of periods (2 s to 86 400 s). Only the data up to 15 000 s periods were used for interpretation of conductivity structure, since telluric data at longer periods were dominated by ocean-tidal effects; spectral analysis of one year's data was used to demonstrate the tidal effects. The telluric signals are strongly polarized in the whole frequency range, indicating an anisotropy in surface conductivity.The data indicate the existence of a finite conducting layer 10 ± 3 km thick and resistivity 100–125 ohm-meters, at a depth of 65 ± 5 km. A high resistivity zone (of the order of 4000–5000 ohm-meters) lies below this layer. There is no evidence for any further conducting zones down to a depth of at least 750 km.
Isotopic ages from the Appalachians and their tectonic significance: Discussion
Authors: Church W. R.
Published: April 2011

The interpretation of the tectonic history of the Northern Appalachians made by Harper (1968), largely on the basis of K–Ar age determinations, and its favorable comparison with the chronology of folding established by Woodward (1957) for the Central and Southern Appalachians is not substantiated by the field evidence.
Model of evolution of the Bella Coola – Ocean Falls Region, Coast Mountains, British Columbia
Authors: Baer A. J.
Published: April 2011

Granitic rocks and metavolcanics underlie most of the Coast Mountains of British Columbia between the fifty-second and the fifty-third parallel, about half-way between Vancouver and Prince Rupert. The age of most rocks is unknown. The area has been involved in at least two orogenic cycles. The oldest known supracrustal rocks (Upper Paleozoic?) have been metamorphosed to gneisses, deformed along northeasterly trends, and intruded by granitic plutons, probably early in the Mesozoic Era. These rocks formed the basement of disconformable Mesozoic sediments and volcanics. The basement and its Mesozoic cover were metamorphosed and deformed along northwesterly trends in the early Tertiary. In the late Tertiary (Pliocene?) post-kinematic granites were emplaced and basalts were extruded for a period extending to postglacial times. The model is possibly applicable to all of the Coast Mountains in Canada.
Crustal structure of Northwestern Ontario: Refraction seismology
Authors: Hall Donald H. , Hajnal Zoltan
Published: April 2011

Deep seismic sounding of the earth's crust has been carried out between latitudes 49°30′ N and 51°30′ N, from longitude 93 °W to longitude 96 °W, by means of a refraction survey, using energy from underwater explosions. A two-layer crust was found, with velocities uniform both laterally and vertically within the layers. Velocities found were: Pg = 6.05 ± 0.05 km/s; Sg = 3.46 ± 0.05 km/s; P* = 6.85 ± 0.05 km/s; S* = 4.00 ± 0.05 km/s; Pn = 7.92 km/s; Sn = 4.60 ± 0.08 km/s. The discontinuity separating the crustal layers (called the Intermediate discontinuity) is believed to be similar to the Conrad discontinuity. Contour maps of depths to this discontinuity and the Mohorovicic discontinuity were produced. Average depths (below surface) are: Intermediate = 18.25 km; Mohorovicic = 34.28 km. Average surface elevation is 0.33 km. Velocity averaged vertically through the crust has a mean value over the area of 6.36 km/s. Structures on the discontinuities are related to at least one major surface geological feature. A form of the time-term method called the station-pair method was designed during the survey and is recommended for the interpretation of seismic crustal refraction surveys.
Cordierite–gedrite rocks and associated gneisses of Fishtail Lake, Harcourt Township, Ontario
Authors: Lal R. K. , Moorhouse W. W.
Published: April 2011

The cordierite–gedrite rocks and associated gneisses on the north side of Fishtail Lake, Harcourt Township, Ontario, occur within the Grenville gneiss complex of the Haliburton Highlands. The investigation comprises a petrographic study, based on geologic mapping, and supplemented by new chemical analyses of gedrites, cordierites, garnets, biotites, and typical rocks. Comparison with compositional data from other metamorphic environments shows that the compositions of associated cordierite, garnet, and anthophyllite (gedrite) and garnet–cordierite–biotite have lower FeO/(MgO + FeO) ratios in high-grade regional metamorphic environments such as exemplified at Fishtail Lake than in contact metamorphic associations. The chemical composition of the rocks is characterized by high MgO and FeO and low lime and alkalies, compared with argillaceous rocks and metamorphic rocks derived from them. It is suggested that this unusual composition results from the removal of an anatectic granite fluid from the parent rock during partial melting associated with high-grade metamorphism. Pegmatites and aplites associated with the gneisses may represent a part of this granite fluid. This hypothesis is shown to be consistent with published experimental data, field observations, and the composition of the cordierite–gedrite rocks compared with hypothetical argillaceous parents.The rocks of the area were metamorphosed initially to the staurolite–almandine subfacies, as indicated by the occurrence of inclusions of staurolite in garnet. With increasing intensity of metamorphism, in the sillimanite–almandine–orthoclase subfacies, the staurolite became unstable, and apart from relicts, is now represented by garnet and sillimanite. Partial anatexis and removal of a melted fraction of granite composition took place, leading to the crystallization of cordierite–gedrite assemblages. Subsequent retrograde metamorphism altered some of the cordierite to kyanite–andalusite–chlorite and pinite. This secondary generation of kyanite and andalusite has resulted, in two samples studied, in the association of kyanite, andalusite, and sillimanite.
New K–Ar age determinations on rocks from the east coast of Labrador
Authors: Grasty R. L. , Rucklidge J. C. , Elders W. A.
Published: April 2011

In a search for Tertiary dikes, rocks were collected along part of the east coast of Labrador. K–Ar age determinations on some of these rocks suggest that the Grenville Front passes out to sea along the north side of Groswater Bay.
Erosional sand columns in dune sands, Cape Sable Island, Nova Scotia, Canada
Authors: Gees Rudolf A. , Lyall Anil K.
Published: April 2011

Miniature sand columns eroded into crossbedded dune sands are described. Apparently the columns formed after the spring thaw by wind and water erosion.