bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Heat Flow Data—in situ Thermal Conductivity Measurements
Authors: Beck A. E. , Anglin F. M. , Sass J. H.
Published: April 2011

The electrically heated cylindrical probe has often been used to measure the thermal conductivity of materials which allow the contact layer to be small enough to have negligible thermal resistance and negligible thermal mass. The probe method is not widely used in boreholes, mainly because the increased complexity of the theory required by the boundary conditions encountered in typical field situations makes it difficult to design appropriate probes and to interpret the data.This paper deals with the results of a comprehensive series of laboratory and field experiments, using cased and uncased boreholes, to investigate the importance of various design parameters and to compare the relative merits of the many proposed methods of reducing the data.It has been found that there is a surprising degree of latitude in probe design provided an uncertainty of 10% in conductivity values can be tolerated.
Petrology and Sedimentation of Huronian Arenites, South of Espanola, Ontario
Authors: Casshyap S. M.
Published: April 2011

The five arenaceous lithostratigraphic units of the Huronian sequence recognized in the Espanola–Willisville area are the Mississagi, Espanola, Serpent, and the Lorrain Formation, as also the intercalated zone which forms the uppermost subdivision of the Gowganda Formation.The bulk of the Huronian arenites is a mixed assemblage of fine, medium, and coarse subarkose, and arkose which are either poorly sorted, muddy fine-to-medium grained (Mississagi, calcareous Espanola, lower Serpent) and muddy medium-to-coarse grained (lower and middle Lorrain), or, moderately well-sorted, medium-to-coarse grained (middle and upper Serpent and intercalated zone). There is, however, one unit in the upper part of the Huronian sequence (uppermost Lorrain) which is a brilliant white supermature quartzarenite. Among the notable petrographic features are a lower quartz – feldspar ratio, rock fragments of metasedimentary and metavolcanic origin, and occasionally occurring rounded quartz. The feldspathic debris for these arenites was derived largely from the older granitoid rocks similar to the 'Algoman granite' of the Canadian Shield to the north of the study area and partly from the supracrustal rocks infolded in the granitoid terrain. Dominance of plagioclase (oligoclase ?) over potassic feldspar and their overall freshness in the arenites may suggest that the source rocks by and large were not deeply weathered,An integrated analysis of lithologie association and sedimentary characters, including texture and mineralogy of the arenites, possibly indicates a near-shore depositional environment (? fluviatile-deltaic) for several Huronian arenites (Mississagi, Serpent, intercalated zone, and middle and upper Lorrain); some may be deltaic-marine (lower part of lower Lorrain). Calcareous Espanola was perhaps deposited beyond the shoreline partly in deeper waters and partly in shallow turbulent environment. Likewise, clean white quartzarenite of top Lorrain may represent deposition in the turbulent fore-shore zone (beach or shelf).
Evolution of Mt. St. Joseph—an Archaean Volcano
Authors: Clifford Paul M. , McNutt Robert H.
Published: April 2011

A 6650-m thickness of volcanic rocks at Lake St. Joseph is here interpreted as an Archaean composite strato-volcano. Despite severe deformation, primary mesoscopic fabrics are well-preserved. They permit the inference of a physical eruptive history, to which the chemistry can be related.The lowermost 2700-m of flows, pillow breccias, and autobreccias are exclusively basaltic, and indicate quiet, probably semi-continuous activity. Interruption of this activity is shown by an intraformational conglomerate developed on a metadiorite, which has thermally metamorphosed argillite lenses intercalated with the flows. Subsequently, activity became more episodic and violent, yielding, first, 750-m of mixed flows and fragmental rocks, substantially andesitic; and then 3200-m of fragmental rocks, substantially salic. Basaltic dikes ramify through the volcanic pile. Several rhyolitic or dacitic flows are regarded as flank eruptions.Generally, these volcanic rocks have trends somewhat similar to trends for other Archaean volcanics. However, there is an iron enrichment trend which we suggest indicates an initially low pO2 increasing as the volcano ages. This increase may indicate an increase in total gas pressure, compatible with the change from quiet to violent eruptive mode.
Hexanchid and Orthacodontid Shark Teeth from the Lower Tertiary of Vancouver Island, British Columbia
Authors: Waldman M.
Published: April 2011

Teeth of the sharks Heptranchias and Orthacodus are described from beds of Upper Eocene—Lower Oligocene age on the west coast of Vancouver Island. This represents the youngest known geological occurrence of Orthacodus and is the first record of either genus in Canada.
Digital Recording of Mass Spectra in Geologic Studies. I
Authors: Stacey J. S. , Wilson E. E. , Peterman Z. E. , Terrazas R.
Published: April 2011

A paper-tape digital recording system is described which has been used to determine the isotopic abundance ratios of strontium from geologic samples. The system costs less than $10 000 and has proved to be highly reliable during its three years of operation. More than 600 analyses have been recorded and the results processed by an IBM-360 computer. This procedure has improved the precision of analyses from this laboratory by a factor of two. Over a period of 11 months, 16 measurements on the M.I.T. strontium carbonate standard gave a mean value for (87Sr/86Sr)n = 0.70797 ± 0.017%. The uncertainty En the results is the standard deviation of the analyses with the 86Sr/88Sr value normalized to 0.1194. Over shorter periods of time considerably better precision is indicated.
The Mid-Atlantic Ridge Near 45° N. XV. Thermal Conductivity of Dredge and Drill Core Samples
Authors: Hyndman R. D. , Jessop A. M.
Published: April 2011

Thermal conductivities have been measured on dredge samples and drill core from the Mid-Atlantic Ridge near 45° N. On the basis of these measurements and published heat flow values, crustal temperatures near the ridge are estimated.
Multiple Deformation in Archean Rocks of the Vermilion District, Northeastern Minnesota
Authors: Hooper P. R. , Ojakangas R. W.
Published: April 2011

The structure of the Precambrian rocks of the Vermilion district is critically examined. It is demonstrated that two significant deformations (F1 and F2) have affected the area in addition to a later set of faults, joints, and kink-bands (F3). The F1 folds are tight to isoclinal with gently plunging axes and vertical axial planes trending west–northwest and containing iron formation and greenstones in anticlinal cores. The second deformation forms a series of open to close asymmetric folds (F2) with steep axes and vertical axial planes trending east–west. Of these, F1 has the more significant effect on the pattern of rock outcrop and it is suggested that it is directly related to the diapiric rise of the batholiths lying immediately to the north and south. The F2 folds may be accounted for by further compression between the two granite bodies.
A Study of Potash Fenitization around the Brent Crater, Ontario,—A Paleozoic Alkaline Complex
Authors: Currie K. L.
Published: April 2011

Fractured and brecciated granitoid gneisses around and within the Brent Crater display progressive chemical and mineralogical changes due to metasomatism, culminating in potassic, silica-undersaturated metasomatic rocks. In the metasomatized rocks, potash feldspar increases in amount and degree of triclinicity with increasing metasomatism, while quartz and plagioclase decline in amount. Calcite of carbonatitic isotopic character is found in some of the breccia matrices. Alkaline ultrabasic dikes, identical in chemistry, petrography, and radiometric age to those of the Nippissing alkaline petrographic province, cut the breccia. Potassic trachyte, which appears to form dikes and lenses within the crater, may be the result of anatexis of potassic metasomatites. The geometric form, petrography, and chemical trends of the metasomatized rocks are virtually identical to those of the fenite aureole of the Callander Bay alkaline carbonatite complex, 42 miles (67.6 km) to the west, suggesting that they result from a fenitization process in which potassium rather than sodium is enriched.
Advances in the Geochronology of the Rice Lake – Beresford Lake Area, Southeastern Manitoba
Authors: Turek Andrew , Peterman Zell E.
Published: April 2011

The Rice Lake – Beresford Lake area consists of an easterly trending Precambrian greenstone belt which is flanked on the north by granitic rocks and on the south by granitic and metamorphic rocks. Analyses of an intrusive, late tectonic quartz monzonite at Black Lake, yield an isochron age of 2735 ± 55 m.y. with an initial 87Sr/80Sr composition 0.7019 ± 0.0008. This age is a minimum for the granitic rocks to the south of the greenstone belt and is the oldest age obtained in this area. On the other hand, analyses of a quartz diorite pluton intrusive into the greenstones give a metamorphic age of 2555 ± 70 m.y. with an initial 87Sr/86Sr of 0.7016 ± 0.0012. Mylonite zones are developed along the northern and southern boundaries of the greenstone belt. Analyses of whole-rock samples from these zones yield an age of 2345 ± 100 m.y. with initial 87Sr/88Sr 0.7044 ± 0.0024, and is the youngest age obtained in the area.These new data, combined with our previous work, indicate three major events. The first and oldest event is 2730 ± 50 m.y. and is interpreted as a period of regional metamorphism, granite emplacement, and the emplacement of gold–quartz veins which postdate the greenstones. A second period of metamorphism and granite emplacement occurred at 2530 ± 40 m.y. and it affected the area as a whole, as evidenced by updated mineral ages. The third and youngest event, 2345 ± 100 m.y., is recorded by the mylonites and may represent epeirogenic movement in the area.
A Revision of Precambrian Structural Provinces in Northeastern Quebec and Northern Labrador
Authors: Taylor F. C.
Published: April 2011

Recent mapping in northeastern Quebec and northern Labrador has shown no structural discontinuity between areas forming parts of the Churchill and Nain structural provinces. Structural trends and geological map-units pass directly from the Churchill province into the area known as Western Nain sub-province. Only one period of folding and metamorphism has been recognized in both areas. Therefore, the concept of the Western Nain sub-province is refuted.The area previously known as Eastern Nain sub-province forms a discrete structural and geological unit and therefore is considered to form a structural province renamed Nain. A more southerly location of the Grenville Front adds approximately 3500 sq. miles (9060 sq. km) to the redefined Nain province. This wedge-shaped area, lying north of the Grenville Front, shows northeasterly to easterly trends as opposed to northerly trends in most of the redefined Nain province. This structural discordance indicates a new sub-province, the Mak-kovik, immediately north of the Grenville Front.
Least-squares Analysis of Fabric Data: A Note on Conical, Cylindroidal and Near–cylindroidal Folds
Authors: Venkitasubramanyan C. S.
Published: April 2011

A cylinder and a plane may be considered as special limiting cases for a right circular cone as the semi-apical angle approaches 0° and 90° respectively (Loudon 1964, Kelley 1966). If these forms are viewed as surfaces generated by an array of lines in space, the rotation axis for the array (the axis of the "cone") can be determined from the orientations of the surface-generating lines by a single computational procedure, using least-squares criterion. The mean angle between the rotation axis and the surface-generating lines will be the semi-apical angle of the cone. However, if this method for determination of the semi-apical angle of the cone, and therefore the best-fitting small circle, is extended to fabric diagrams, in which an array of lines may only statistically describe a great circle or small circle on a stereographic projection, ambiguities arise in certain cases and the semi-apical angle obtained may not be the true semi-apical angle. The difficulty arises because the poles to foliation surfaces are arbitrarily assigned "senses".
The Aston Formation (? Proterozoic) on Prince of Wales Island, Arctic Canada
Authors: Dixon Owen A. , Williams S. Ridgeley , Dixon James
Published: April 2011

Substantial exposures of a thick basal sedimentary sequence, the Aston Formation of Somerset Island, occur on eastern Prince of Wales Island and incorporate at least 2600 ft (793 m) of arkose, subarkose, and orthoquartzite, with minor dolostone, chert, and mudstone. The detrital sediments, derived from contemporary uplands on the site of the present Boothia Arch, accumulated in shallow marine to lagoonal environments. A thin, extensive, and distinctive stromatolitic dolostone in the two major exposures of the formation has an environmental and possibly a regional time–stratigraphic significance. Gabbro dikes and sills, some of them exceeding 1000 ft (305 m) in thickness, intrude the Aston Formation.
Qualitative Petrographic Interpretation of Potsdam Sandstone (Cambrian), Southwestern Quebec
Authors: Lewis D. W.
Published: April 2011

The Cambrian Potsdam Group in southwestern Quebec comprises the quartzo-feldspathic Covey Hill Formation (up to 2000 ft (610 m) thick), and the unconformably overlying and overlapping Chateauguay Formation, which is subdivided into the lower Cairnside Member (up to 500 ft (152 m) thick) of pure quartz sandstone and the Upper Theresa Member of interlayered quartz sandstone and dolostone. Petrographic study concentrated on Covey Hill and Cairnside lithologies from three deep cores near Montreal. Traditional interpretation of Potsdam Sandstone as a pure quartz blanket deposited by transgressing seas applies only to the Cairnside Member.The Covey Hill Formation comprises subround-round sands, sparse rounded gravels, scattered penecontemporaneous clay clasts, and rare thin mud layers. Juxtaposition of well and poorly sorted laminations of different sand sizes, mica-clay, and heavy mineral concentrations, attests fluctuating depositional energies. Presence of silt-free clayey matrix and scattered coarse grains set amongst much finer sands attests marked predepositional eolian activity. Composition of quartz, fresh and partly weathered K-feldspar, micas, and stable heavy minerals is inferred to reflect a prolonged predepositional history during which unstable minerals were destroyed. Hematitization of biotite flakes, and other diagenetic modifications, are inferred to result from pedogenesis in an alluvial environment of deposition.
Local Equilibrium in a Two-Pyroxene Amphibolite
Authors: Fletcher C. J. N.
Published: April 2011

Six mineral assemblages have been defined within a small portion of a layered two-pyroxene amphibolite. The relationships between bulk composition, mineral composition, and mineral assemblage were determined from X-ray fluorescence, electron microprobe, and optical data. It is shown that the layer assemblages and the mineral compositions are, in general, directly related to the bulk compositions of the layers. Graphical representation of the phase assemblages is impossible, due to the number of determining components; however, an attempt is made to tabulate the phase relation-ships in 9-space. Linear regression analysis has been used to show that the six mineral assemblages owe their differences purely to different bulk compositions, and that no isochemical reactions can be written between them. The computed equations relating the mineral assemblages indicate that water was immobile during metamorphism.
A Postglacial Freshwater Drum (Aplodinotus grunniens) from Ontario, and Comments on the Zoogeography of the Species
Authors: Harington C. R.
Published: April 2011

A freshwater drum (Aplodinotus grunniens) specimen from postglacial deposits of northern Ontario indicates the species former presence in Lake Barlow–Ojibway. The fact that the species survives in Lakes Abitibi and Timiskaming may be best explained by its having entered Lake Barlow–Ojibway from the west during the Gimli phase of Lake Agassiz about 8000 years ago, but this hypothesis cannot be confirmed with the existing evidence.
Zoned Margarite from the Badshot Formation (Cambrian) near Kaslo, British Columbia
Authors: Jones J. W.
Published: April 2011

Electron microprobe analysis of margarite crystals shows that they are zoned from Ca1.13Na0.74K0.05(Al4.01Ti0.02Fe0.13Mg0.05)[Si4.78Al3.12O20](OH)4 in their centers to Ca1.63Na0.26K2.005 (Al3.98Ti0.02Fe0.13Mg0.05)[Si4.10Al3.90O20](OH)4 at their margins. The crystals occur in the disequilibrium assemblage calcite – phengite (2M1) – margarite – quartz – kaolinite – epidote –apatite found in Badshot marble from the almandine garnet zone of regional metamorphism.
Variations in Lithospheric Thickness in Canada
Authors: Wickens A. J.
Published: April 2011

Surface wave phase velocities between stations of the Canadian seismic network were combined with crustal refraction data to obtain crust and upper mantle models for a number of regions of Canada. Both Rayleigh and Love wave dispersion were used. After fixing model crustal thicknesses and Pn velocities from refraction measurements, the fit to surface wave phase velocities was obtained primarily by variation of the shear velocities and the thickness of the lithosphere.Striking differences are found in the depth to the upper mantle low velocity layer with a minimum lithospheric thickness in the Cordillera and the thickest in the central Shield area. In addition the low velocity contrast is most prominent in the Cordillera. The base of the low velocity layer is less well defined from the study, but may be deepest in shield areas.The results obtained indicate the potential of the methods for determining more detail about boundaries between different lithospheric units, and appear to be generally concordant with flexural rigidity studies of the lithosphere.
Lapis Lazuli near Lake Harbour, Southern Baffin Island, Canada
Authors: Hogarth D. D.
Published: April 2011

Two lapis lazuli occurrences are present in marble near the cores of synforms near Lake Harbour, southern Baffin Island. The main occurrence covers an area of 3500 m2 and contains 4 zones, the longest traced for 168 m. The lapis lazuli consists mainly of haüyne, diopside, plagioclase, and calcite in varying proportions. Phlogopite, nepheline, tremolite, and scapolite are locally abundant. The rock could have originated during metamorphism through an exchange of elements between evaporites and interbedded shales. Blue haüyne has an absorption maximum at 600 nm, green haüyne maxima at 400 and 600 nm. On heating in air the 600 nm peak is greatly extended and both green and blue haüyne become deep blue. At the main occurrence, the longest zone could possibly supply commercial grade gem and ornamental stone, although the fractured nature and pale color are handicaps.
Analysis of Fracturing in Precambrian Volcanics North of Madoc, Ontario
Authors: Robin P.-Y. , Currie J. B.
Published: April 2011

This paper presents a study of joints and other systematic fractures in Precambrian metavolcanic rocks. Although the mechanism that created the complex array of joints is not clear, one can deduce that they served as pre-existing planes of weakness during a later period of deformation in which slip occurred along both joints and systematic fractures. One consequence of this movement was an adjustment of rock material at the junction of intersecting fractures. An 'adjustment surface' was created at specific fracture intersections by movement of adjacent joint blocks toward one another. This 'adjustment feature' is a structural element, which can be utilized in reconstructing the principal stress directions of the later period of deformation.
Vesicularity of Mid-Oceanic Pillow Lavas
Authors: Aumento F.
Published: April 2011

In contrast to pillow lavas from the marine environment around Iceland and Hawaii, tholeiitic pillow lavas from the Mid-Atlantic Ridge at 45° N do not show a correlation between vesicle size and depth of recovery. Post-eruptive vertical block faulting may have displaced the lavas from their original extrusion depth by as much as 1500 m, explaining in part the lack of correlation. Calculation of the original depth of extrusion by compensation for these vertical movements indicates that many of the basalts now high on the Crest Mountains were extruded in deep water (2900–3500 m), possibly within the floor of the Median Valley. Nevertheless, they were able to produce numerous, comparatively large vesicles, permitting the basalts to outgas radiogenic argon trapped in the magmas.Bulk chemical differences between the 45? N basalts and those of Iceland and Hawaii cannot explain why those from 45? N are able to outgas under high hydrostatic pressure. Different histories prior to extrusion may contribute to these varying characteristics.
Algal Bioherms of the Upper Gull River Formation (Middle Ordovician) near Kingston, Ontario
Authors: Greggs Robert G. , Sargent M. Wayne
Published: April 2011

Twelve stratigraphic sections, that lie within a 15 to 20 ft section (4.6 to 6 m) of upper Gull River limestone, were measured within an area of 400 square miles (1000 km2) near Kingston, Ontario.Sedimentation was cyclic and a series of recessive, clastic layers alternating with resistant carbonate units was deposited. Two carbonate units, low in the measured section, contain here and there stromatolites of the LLH-S variety. Above these, a third carbonate layer contains LLH-S stromatolites which appear to persist throughout the area. A fourth carbonate unit above these includes scattered occurrences of stromatolites developed about colonies of Tetradium cellulosum.A brief description of the algal stromatolites occurring in the measured stratigraphic section is presented, and from adjacent lithologies an environment of growth in shallow, semi-restricted marine waters is postulated.
Submarine Sand Dunes in the St. Lawrence Estuary
Authors: d'Anglejan B. F.
Published: April 2011

Areas of sand dunes and ripples have been observed in the estuary of the St. Lawrence River below Quebec City. A train of dunes 18 km long is present in the channel of Ile-aux-Coudres. Symmetrical dunes as high as 12 m and reaching 120 m in wave-length are abundant. Symmetrical subsurface crests are also revealed by seismic reflection profiling. The mode of origin of these dunes is not yet established. However, because of the high degree of stratification present in the water column, the possible role played by internal water waves in their formation should be considered.
Old K–Ar Mineral Ages from the Grenville Province, Ontario
Authors: Dence M. R. , Hartung J. B. , Sutter J. F.
Published: April 2011

Hornblende-rich concentrates from quartz–feldspar gneisses of the Grenville Province near Brent Ontario, have yielded K–Ar apparent ages of 1570 to 1480 ± 80 m.y., while coexisting biotite- and feldspar-rich separates give 'normal' Grenville K–Ar ages near 900 ± 40 m.y. Comparison with the nearest Rb–Sr isochron dates suggests that the indicated hornblende K–Ar age represents a minimum age for time of crystallization of the gneisses in the Brent area and that the younger ages for minerals with lower blocking temperatures indicate a later thermal event in the metamorphic history of the Grenville Province.
Quelques Caractéristiques Géologiques et Minéralogiques des Dépôts d'Argile du Nord-Ouest du Québec
Authors: Ballivy Gérard , Pouliot Gaston , Loiselle André
Published: April 2011

The clay deposits of Northwestern Quebec (from Matagami to Rupert House) were formed during the retreat of the Laurentian ice sheet. The oldest deposits are varved clays formed when the region was submerged by glacial Lake Barlow – Ojibway; the varved clays have been traced northward to Rupert House. A minor glacial surge (Cochrane stadial) extending southward to Matagami, partly covered and reworked the lacustrine clays; evidences of this glacial readvance were observed on the left bank of Rupert River near Rupert House. Following this glacial stage, the land was invaded by sea water (Tyrrell Sea) from which were deposited the silty clay that underlies much of the Hudson Bay Lowlands.The mineralogical composition of the marine clay differs from that of the lacustrine clay by its carbonate content: 30% against 2% or less for the lacustrine clay. The clay fraction of the two types of clays is made up of similar minerals which, in order of decreasing importance are: illite, chlorite, vermiculite, and kaolinite. The marine clay is coarser grained than the lacustrine clay and, locally, gives rise to important flow-slides. The slides are subcircular in shape and have a typical bottle-neck opening; they have never been observed to develop in the varved clays. Their occurrence in the marine clays would seem to depend principally on the microstructure of the material, a silty clay that is fissured at the surface. The flow-slides occur specially during the spring thaw when the ground is oversaturated with water.
Application of Geophysical Logging to Groundwater Studies in Southeastern Saskatchewan
Authors: Dyck J. H. , Keys W. S. , Meneley W. A.
Published: April 2011

Single-point resistance and spontaneous potential logs in fresh-water filled rotary-drilled test-holes provide data useful in geohydrologic studies in Saskatchewan. These geophysical logs are made by many of the water well drilling contractors in Saskatchewan on a routine basis. The logs provide good resolution of various lithologic units and provide data required to estimate the salinity of water in sand beds prior to constructing a well.Caliper logging offers a potentially useful method for evaluating hole conditions and the effect of drilling techniques on the formation in completion zones. The casing collar locator log run in a previously constructed well near Estevan demonstrates that this device can provide an accurate and objective measurement of the position and length of each joint of casing, the position of the screen assembly, and the location of screened and blanked intervals within the screen assembly. This tool should find general application in water well construction and maintenance practice.The neutron-epithermal neutron log provides a method of measuring the porosity of sand and gravel beds. The response of the gamma log is similar to that of the spontaneous potential log and the neutron-epithermal neutron log deflects in a fashion similar to the resistance and resistivity logs. Nuclear logs offer the advantage that they can be run in cased or uncased boreholes which may be filled with any type of fluid. They require more complicated and expensive instrumentation and slow-speed logging to obtain the required resolution. The normal resistivity logs offer the possibility of determining the concentration of dissolved solids in the formation water. The gamma-gamma log is a poor alternative to the natural gamma and neutron log for stratigraphic correlations.
The Petrology and Paleomagnetism of the Coronation Sills
Authors: Robertson W. A. , Baragar W. R. A.
Published: April 2011

The Coronation Sills and their extrusive equivalents of the Franklin Magnetic Division form a major basaltic province of Hadrynian age in the northwestern part of the Canadian Shield. The sills are saturated or slightly undersaturated, undifferentiated tholeiites. They are similar in composition to tholeiitic plateau basaltic provinces elsewhere, particularly to the Karroo Province. Most of the paleomagnetic samples contain secondary components that are much reduced by magnetic cleaning.The optimum cleaning field determined by the precision method is 105 Oe, but by the endpoint method it is in the 200–400 Oe range. Sites may be separated by thermal cleaning into a stable group with a dominant discrete blocking temperature above 500 °C, and a less stable group with blocking temperatures distributed in the 50–550 °C range. The pole position calculated from samples cleaned in 210 Oe is 1 °S, 163 °E (α95 = 9°). The position of the revised pole for the Franklin Magnetic Interval, incorporating the Coronation Sills data, is at 5 °N., 168 °E. (α95 = 5°).
Paleomagnetism of Igneous Rock Units from the Coast of Labrador
Authors: Murthy G. S. , Deutsch E. R.
Published: April 2011

Paleomagnetic results are reported for the first time from the coast of Labrador. The rocks are from (1) 20 sites of gently folded basalts of the Mugford Series, dated 948 ± 90 m.y., near Cape Mugford, and (2) 12 gabbroic dikes in a swarm dated 2080 ± 42 m.y., near Indian Harbour. Both dates are from preliminary, published K–Ar determinations. After partial alternating-field (AF) or thermal demagnetization, nearly all samples from both rock units revealed a stable thermoremanence that is most probably of primary origin. For the Mugford basalts, a mean remanence direction relative to bedding planes was calculated, after AF treatment, from 16 stably magnetized sites ([Formula: see text] flows). The corresponding pole is 49 °N, 143 °W, with dp = 9°, dm = 11°, which is northeastward of most North American poles from rocks dated 1200-1000 m.y. The pole calculated from the 12 Indian Harbour dikes, after AF treatment, is 6 °S, 117 °W, with dp = 6°, dm = 12°.
Plagioclase-Garnet-Epidote Equilibria in Hornblende-Plagioclase Bearing Rocks from the Esplanade Range, British Columbia
Authors: Ghent Edward D. , DeVries C. D. S.
Published: April 2011

Hornblende-plagioclase bearing rocks occur as layers and lenses within metasedimentary rocks of the Esplanade Range, British Columbia (51°31′ N, 117°27′ W). A typical assemblage in the hornblendic rocks is quartz-plagioclase-garnet-epidote-ilmenite ± sphene ± calcite. Plagioclase from the beginning of the garnet zone has an average composition near An35, whereas plagioclase from well within the staurolite-kyanite zone has an average composition near An95. Garnet and epidote also show variation in composition with increasing metamorphic grade.From structural and stratigraphic arguments and from the presence of kyanite in pelitic rocks, we estimate a minimum load pressure during metamorphism of about 4 kb.Using thermochemical and experimental data on the following reactions:1) 4 Zoisite + quartz = 5 anorthite + 1 grossular + 2 water;2) 2 Zoisite + CO2 = 3 anorthite + calcite + water;3) Calcite + rutile + quartz = sphene + CO2;4) Calcite + quartz = wollastonite + CO2, andassuming an ideal solution model for the solids, we can construct a set of curves for the above reactions on a [Formula: see text] diagram, each curve representing a different set of solid compositions.A temperature variation of approximately 150 °C from the beginning of the garnet zone to well within the staurolite-kyanite zone and a fluid composition of [Formula: see text] seems adequate to account for the increase in anorthite content in plagioclase with increasing metamorphic grade.
Digital Recording of Mass Spectra in Geologic Studies. II
Authors: Stacey J. S. , Wilson E. E. , Terrazas R.
Published: April 2011

The digital system described herein can record data from several mass spectrometers on a single magnetic tape. Programs have been written for isotopic abundance calculations of lead, thorium, uranium, strontium, and argon analyses. The programming techniques successfully recognize and reject spurious data. Both chart and digitally recorded data are presented for seven analyses of the U.S. National Bureau of Standards common lead standard SRM 981. Standard deviations of the ratios of the digital data range from 0.018% for the 207Pb/206Pb to 0.038% for the 208Pb/204Pb. The equivalent hand-processed values are 0.044 and 0.066%, respectively. The measured ratios are offset from their absolute values almost entirely by a fractionation component of about 0.16% per mass unit. Other bias introduced by the system is shown to be very small and probably not greater than 0.01% for the digital data and 0.05% for chart-read data. Calibration of the vibrating reed electrometer amplifier with current flowing through the feedback resistor has considerably improved the analytical precision and reduced the system bias.
Seiches of Sydney Harbor, N.S.
Authors: Easton A. K.
Published: April 2011

The periods and responses of the free oscillations are calculated for one-dimensional models of Sydney Harbor. In particular, after Rayleigh's mouth correction is taken into account, it is evident that the prominent wave often recorded at North Sydney is the fundamental seiche. The seiche is induced by the passage of weather systems along the coast of Nova Scotia. Its response could be reduced by building a dam across the North West Arm.
Weathered Interstadial Green Clay at Port Talbot, Ontario
Authors: Quigley R. M. , Dreimanis A.
Published: April 2011

The geologic origin of a distinctive layer of green, weathered clay belonging to the lower part of the Port Talbot Interstadial sediments (Port Talbot I) on the north shore of Lake Erie has been reinterpreted in relation to its clay mineralogy, carbonate content, and pollen data.In addition to illite and chlorite, both characteristic of all clayey glacial sediments in the area, the green clay contains abundant smectite probably produced by oxidation weathering of chlorite in the Bradtville Till. Carbonate contents, normally less than 1% in the green clay compared to values of 15 to 45% in the overlying and underlying sediments, indicate extensive solution weathering.The green clay layer is interpreted to be an accretion gley, weathered in a soil profile during the early part of the Port Talbot Interstadial and subsequently eroded and deposited in poorly drained depressions under reducing conditions. An abundance of oak, pine, and spruce pollen indicate a fairly temperate climate at the beginning of Port Talbot I, becoming cooler towards the deposition top of the green clay, as suggested by low percentage or absence of oak pollen.
The Estimation of Plate Motions by Astronomical Methods
Authors: Tanner R. W.
Published: April 2011

Some of the problems involved in the detection of plate motions by astronomical methods are discussed with particular reference to a Herstmonceux–Calgary cooperative program using photographic zenith tubes. Analysis of the observations obtained in 1969 and 1970 shows that several decades of continued observation may suffice with present techniques to demonstrate and measure the relative motion of the North American – Eurasian plates.
The Continental Margin Off Labrador and Eastern Newfoundland–Morphology and Geology
Authors: Grant A. C.
Published: April 2011

Seismic profiler surveys have defined the landward limit of presumed Mesozoic–Cenozoic deposits on the continental shelf off Labrador and eastern Newfoundland. Along the Labrador coast the contact of these deposits with Precambrian rocks coincides with a pronounced 'marginal channel'; off eastern Newfoundland their contact with rocks of the Appalachian System is marked by a landward-facing escarpment. The physiographic relief characterizing this contact zone reflects erosional exploitation of the associated contrast in erosional susceptibility. The chief erosional agent is considered to have been the Quaternary glaciers. The marginal channel off northern Labrador is indicated as a zone of major faulting, which probably further enhanced the erosional vulnerability. The transverse depressions cutting the outer shelf off Labrador and Newfoundland are likewise considered to be zones of structural dislocation, which have been physiographically emphasized through processes of erosion.Integration of the seismic profiler results with other geophysical and geological data from the study region consistently supports the concept that the morphology of the continental margin expresses fundamental elements of geologic structure. Available evidence can apparently be reasonably synthesized in terms of a structural model based upon differential vertical movements of segments of continental crust. By this approach the structure of the continental margin north of the Grenville Front off Labrador may be very different from that of the continental margin bordering the western Atlantic Ocean to the south. In addition, the continental fragments represented by Orphan Knoll and Flemish Cap are indicated as having experienced only vertical displacements during postulated episodes of late and post-Cretaceous sea-floor spreading.
Geophysical Investigations East of the Magdalen Islands, Southern Gulf of St. Lawrence
Authors: Watts A. B.
Published: April 2011

Detailed gravity and magnetic surveys confirm seismic refraction evidence of a deep (8–10 km) Carboniferous infilled sedimentary basin (the Magdalen basin) between the Magdalen Islands and Newfoundland. The basin margins are associated with gravity and magnetic 'highs' indicating shallow depths (1–3 km) to pre-Carboniferous basement rocks east of the Magdalen Islands and between Cape Breton Island and Newfoundland. The central Magdalen basin is associated with a large amplitude gravity 'low' (50–60 mgal). This can be partly explained by a 2–4 km thickness of low density Late Mississippian sediments overlain by 1–2 km of Upper Pennsylvanian or younger sediments. The western Magdalen basin is associated with large amplitude (20–40 mgal) circular and elongate gravity 'lows'. Detailed interpretations suggest they are caused by low density evaporite structures. The circular 'lows' are interpreted as salt diapirs. The elongate 'lows' are interpreted as structures in the crest of Mississippian/Pennsylvanian anticlines similar to occurrences of Windsor Group evaporites in northern Nova Scotia. The western Magdalen basin may represent one of the largest areas of salt accumulation in Eastern Canada.
New Fossil Localities in the Lush's Bight Terrane of Central Newfoundland
Authors: Strong D. F. , Kean B. F.
Published: April 2011

Three new fossil localities have been discovered in the Cutwell Group on Long Island in western Notre Dame Bay, Central Newfoundland. Conularids, crinoids, ostracodes, and cephalopods occur in small limestone lenses within pillow lavas and pyroclastics. These fossils tentatively suggest a middle Ordovician age for the Cutwell Group in this area.
Development of the Early Continental Crust. Part 1. Use of Trace Element Distribution Coefficient Models for the Protoarchean Crust
Authors: Shaw Denis M.
Published: April 2011

The original continental crust developed as the residue from fractional crystallization of the mantle–crust system. Using measured distribution coefficients for K, Rb, Ba, Sr, La, Ce, Eu, Yb, and Ni, several crystallization models are tested for conformity with regional geochemical estimates of continental crustal composition.In spite of the uncertainties and approximations the predicted concentrations agree reasonably well with observation, except in the case of Yb.
Ore Mineralogy of the Louvem Copper Deposit Val d'Or, Quebec
Authors: Guha Jayanta , Darling Richard
Published: April 2011

Microscopic study of samples from the Louvem copper deposit shows that the principal ore minerals are pyrite, chalcopyrite, and sphalerite and the accessory ore minerals are rutile, tetradymite, two unidentified tellurides, cobaltite, molybdenite, galena, and four optically distinct phases having compositions along the digenite–bornite tie line.The Louvem ore body is a pipe-shaped mass of mineralized rhyolitic tuff and agglomerate that is conformable with enclosing volcanic and pyroclastic rocks. The ore body is zoned, with a copper-rich core and pyrite-rich margins. Wall-rock alteration spatially related to the ore deposit suggests that it was formed by replacement of porous tuffaceous host rocks by a hydrothermal fluid. Textural features of the ore indicate that it was subjected to post-emplacement thermal metamorphism.
Correlation of Major Aphebian Rock Units in the Northeastern Canadian Shield
Authors: Jackson G. D. , Taylor F. C.
Published: April 2011

Several groups of Aphebian layered rocks in the northeastern Canadian Shield have been correlated because of lithologic and stratigraphic similarities and alignment of groups and structural trends. Most of these layered rocks lie in three distinct fold belts which from south to north have been named the Dorset, Foxe, and the Committee Fold Belts.The widespread occurrence of Aphebian outliers between the fold belts indicates that Aphebian strata probably originally covered the entire area from the Circum–Ungava Geosyncline or Fold Belt east to the Dorset Fold Belt and north to the Committee Fold Belt. The name Baffin Geosyncline is proposed for this depositional zone. Aphebian layered rocks in the two last-named fold belts were probably deposited in marginal mio-eugeosynclinal zones of the main geosyncline and are mainly meta-shale, meta-graywacke, and metamorphosed basic volcanic rocks and associated basic and ultrabasic intrusions. The Aphebian rocks of the Dorset and Foxe Fold Belts were deposited in the central shelf zone of the Baffin Geosyncline and are mainly meta-shale, meta-graywacke, rusty quartz-rich gneiss, marble, and quartzite.The Aphebian layered rocks have been intruded by large granitic plutons and have been metamorphosed to amphibolite and granulite facies of regional metamorphism. Age determinations and structural data indicate that a mid-Aphebian orogeny affected much of the northern part of this region 2000–2200 m.y. ago, and that the whole region was strongly affected by the Hudsonian orogeny.
The Stratigraphy, Mineralogy, and Trace Element Concentrations of the Quaternary Sediments of the Northern Lake Superior Basin
Authors: Mothersill John S. , Fung Patrick C.
Published: April 2011

The late Pleistocene sediments of the northern Lake Superior basin consist of a basal reddish till, deposited during the Valders substage, unconformably overlain by a sequence grading upwards from grayish red, silty clay interbedded with thin sand laminae to grayish red and then gray calcareous varves. Holocene sediments consisting of a clay–silt sequence in the topographic lows, or a thin veneer of sands along the lake-shelf area, unconformably overlie the gray varves. The basal contact of the clay–silts or sands with the gray varves marks the time when glacial ice receded from the Lake Superior basin. Radiocarbon dating indicates that this event occurred more than 11 000 years B.P.The best, though fairly low, positive correlations of pairs of elements in the lake-bottom sediments occur between iron and chromium, zinc and nickel, iron and zinc, and iron and nickel. Different upward migration patterns of elements during syndiagenesis probably is the cause of the low correlation between the elements. Strontium shows negative correlations with the elements of the first transition series of the periodic table; however, a strong correlation of strontium with calcium in the Pleistocene gray varved section probably results from isomorphism of strontium for calcium in the precipitated carbonate minerals.
Postglacial Rates of Denudation by Soil Movement, Free Face Retreat, and Fluvial Erosion, Mont St. Hilaire, Quebec
Authors: Pearce Andrew J. , Elson J. A.
Published: April 2011

Average rates of denudation over periods ranging from 11 800 years to 12 800 years at sites on Mont St. Hilaire, Quebec were estimated as follows:[Formula: see text]The rates of fluvial denudation at Mont St. Hilaire are lower by a factor of one-half than published short term fluvial denudation rates in areas of similar relief and climate. The rates of free face retreat at Mont St. Hilaire are similar to the lowest rates recorded in Spitsbergen, northern Sweden, and in the Yukon Territory.The polygenetic geomorphic history of Mont St. Hilaire and the low rates of denudation estimated in this study together indicate that existing slope and valley forms cannot be explained adequately by the present processes operating at the observed rates.Talus accumulation has obscured some Pleistocene features but other processes have not.
Geological Evidence on the Extinction of some Large Terrestrial Vertebrates
Authors: Russell Loris S.
Published: April 2011

Various stratigraphic sections, from New Mexico to Saskatchewan, reveal in their fossil record the disappearance of the sauropod dinosaurs, the extinction of dinosaurs generally, and the end of the brontotheres. In each case there is no evidence of drastic changes in the depositional environment at the time of the extinction. Rather, the sequence indicates a long period of gradually changing environment, at one moment in which the extinction occurred. Such extinctions appear to be a kind of breaking-point phenomenon, in which the adaptive powers of the animals to the slow changes abruptly reached their limits.
The Distribution of Mercury in the Surficial Sediments of Lake Huron
Authors: Thomas R. L.
Published: April 2011

Total mercury has been determined in 163 samples of the topmost 3 cm of sediment taken from Lake Huron during 1969. Total mercury values range from 54 to 805 p.p.b. with a mean of 222 p.p.b. and a standard deviation of 162 p.p.b. The mercury distribution in the lake sediments shows a trend for increasing concentration from nearshore and mid-lake shallow water, coarse sediment deposits outwards into the fine-grained sediments in the deeper water basins. The application of a quartz correction to compensate for the dilution by an inert constituent reveals two major anomalies of higher mercury concentration. The Saginaw anomaly occurs in the southern basins of the lake and is believed to be due to the input of industrial mercury from Saginaw Bay; the Bruce anomaly in the northeastern part of Manitoulin basin is believed to be due to the weathering of sulfide deposits with subsequent concentration in the lake sediments being related to major water circulation patterns in the lake. From statistical analysis the mercury is believed to be bound in the sediments predominantly adsorbed or complexed by organic matter with subsidiary adsorption by the surfaces of iron sulfides and hydrated iron oxide – inorganic phosphorus complexes.
Chemical Evolution of the System Calcite–Gypsum–Water
Authors: Wigley T. M. L.
Published: April 2011

The effect of the addition of gypsum to a solution of calcite in water (or the addition of calcite to a solution of gypsum in water) is determined theoretically for arbitrary temperature, carbon dioxide content, and degree of saturation with respect to calcite (or gypsum). The results can be used to study the chemical evolution of waters flowing through alternating gypsum and limestone strata, to predict conditions which will lead to the precipitation of calcite and/or gypsum, and to predict the chemical evolution of evaporating calcite–gypsum solutions. It is shown that under some circumstances, simultaneous gypsum (or calcite) precipitation and calcite (or gypsum) solution may occur. Coprecipitation of gypsum and calcite is found to be unavoidable if a solution is evaporated to dryness, although the initial precipitate will be a single mineral. The methods used and many of the conclusions drawn are applicable to other systems of two or more minerals.
Calcium Diffusion in a Mugearite Melt
Authors: Medford G. A.
Published: April 2011

The diffusion rate of calcium in a mugearite melt is determined to vary between 1.07 × 10−7 and 3.36 × 10−7 cm2/s for a temperature range of 1230 to 1423 °C. The activation energy of the process is 29.5 kcal per mole. Diffusion curves are measured with an electron microprobe.