bluuebunny/crossref_metadata_2025 huggingface dataset:
The significance of multiple causes and coincidence in the geological record: from clam clusters to Cretaceous catastrophe
Authors: Tsujita Cameron J
Published: April 2011

Specific causes of unusual events recorded in the geological record are commonly difficult to distinguish and isolate; in some instances, event strata contain features that cannot be explained by a single causal mechanism. Unicausal hypotheses, when applied to complex problems, can lead to the misidentification, misinterpretation, and force-fitting of observations ("great expectations syndrome"). The close timing or temporal overlap of significant events, although statistically improbable on short time scales, becomes possible on long time scales. Event coincidence may occur on a wide range of scales, from local to global. On the local scale, a multiple-event interpretation is offered for both the concentration and clustering of bivalves at specific levels within the Upper Cretaceous Bearpaw Formation of southern Alberta. For this example, the relative timing of fluctuations in benthic substrate texture, oxygen concentration, abundance of planktotrophic larvae, and degree of sea-floor scouring was crucial to the formation and preservation of shell concentrations. On the sharply contrasted global scale, the implications of multiple events warrant much closer consideration than they have received hitherto in terms of major proposed causes for the CretaceousTertiary (KT) mass-extinction event: bolide impact, sea-level change, climatic change, and flood-basalt volcanism. By considering the predictable effects of these synchronous factors, both individually and in combination, a multiple-cause explanation of the KT mass extinction emerges as entirely plausible. Certainly it needs to be considered in all future investigations of this important issue.
Crustal geometry and tectonic evolution of the Archean crystalline basement beneath the southern Alberta Plains, from new seismic reflection and potential-field studies
Authors: Lemieux Sophie , Ross Gerald M , Cook Frederick A
Published: April 2011

Deep seismic reflection profiling of the southern Alberta crystalline basement, namely the Archean Medicine Hat block (MHB), has revealed that the crust is characterized by west- and southwest-dipping reflection fabrics, a layered lower crust, and geometric cutoffs that are interpreted to be remnants of a complex tectonic history. Upper to middle crustal dipping reflections are interpreted to be associated with Archean rocks drilled below the Western Canada Sedimentary Basin and their geometry is consistent with east- and northeast-verging imbrication. Layered lower crustal reflections of the MHB are interpreted as Early Proterozoic delaminated Loverna block crust and injected mafic material, based on geometric relationships, xenolith dating, and gravity modelling. The reflection Moho is diffuse below the MHB at ~15 s two-way time (~47 km). This is similar to estimates based on adjacent seismic refraction data and is up to ~8 km deeper than regions north of the MHB. The MHB crust is interpreted to have undergone two episodes of crustal deformation in the Precambrian: (1) Late Archean formation of the MHB crust by continental collision of two Archean domains along a crustal-scale ramp; and (2) Early Proterozoic crustal shortening associated with the formation of the Vulcan structure, the delamination of the Loverna block crust, and postcollisional injection of mafic melts beneath the MHB crust. Radiometric dating of lower crustal xenoliths suggests a significant Early Proterozoic thermal event in the deep crust beneath the MHB that is coeval with orogenic activity in the Trans-Hudson Orogen and the East Alberta Orogen.
Nd and Pb isotopes from the Lake of the Woods greenstone belt, northwestern Ontario: implications for mantle evolution and the formation of crust in the southern Superior Province
Authors: Ayer John A , Dostal Jaroslav
Published: April 2011

Nd and Pb isotopes from the Lake of the Woods greenstone belt indicate the presence of three distinct reservoir sources: old enriched crust (>3.0 Ga); pre-2.7 Ga, homogeneous depleted mantle; and post-2.70 Ga heterogeneous mantle. EpsilonNd values of +1.1 to +2.3 for ultramafic to felsic metavolcanic rocks (2.742.72 Ga) indicate derivation from depleted mantle. The εNd value of 0.9 for younger turbidite (2.71 Ga), in conjunction with detrital zircon ages ranging from 2.72 to 3.0 Ga, indicates detritus from local greenstone belt sources (depleted mantle) mixed with an older crustal source. Post-2.70 Ga heterogeneity is demonstrated by εNd values ranging from 0.4 to +0.4 in shoshonitic to calc-alkaline metavolcanic rocks and +2.1 in a coeval ultrapotassic pluton. Pb isotopes from the pluton indicate derivation from a depleted mantle reservoir with an initial 207Pb/204Pb of 14.52, an initial 206Pb/204Pb of 13.29, and µ1 of 7.86. Isotopic comparison with post-2.70 Ga potassic suites from across the Superior Province indicates widespread mixing between depleted mantle and enriched end members. The enriched end member has isotopic characteristics of rocks derived from old crustal terrains, such as the Winnipeg River and Opatica subprovinces. This type of isotopic heterogeneity could be the result of crustal contamination or derivation from metasomatized mantle. Contamination of the mantle wedge by influx of fluids derived from partial melting of isotopically evolved, subducted sediments is favoured for the Superior Province potassic suite, because elevated concentration of Sr, Nd, and Pb in conjunction with primitive Mg#s suggest only limited crustal contamination has occurred.
Integrated chitinozoan, conodont, and graptolite biostratigraphy from the upper part of the Cape Cormorant Formation (Middle Ordovician), western Newfoundland
Authors: Albani Roberto , Bagnoli Gabriella , Maletz Jörg , Stouge Svend
Published: April 2011

The Cape Cormorant Formation of the Table Head Group exposed on the Port au Port Peninsula, western Newfoundland, is composed of dark-brown to black shales with interbeds of thin calcareous silty and sandy distal turbidites. Distinctive carbonate conglomerates and breccias derived from the foundering shelf are occasionally found in the formation. The sediments accumulated in the foreland basin formed during the early stage of the Taconic orogeny. The faunas from the upper part of the Cape Cormorant Formation include graptolites, conodonts, and chitinozoans. The graptolites are well preserved, but are of low diversity and are referred to the Darriwil Pterograptus elegans Zone. Conodonts recorded from the distal turbidites are rare and fragmented. The faunas include taxa that are known from the St. George and Table Head groups. The conodont fauna is tentatively assigned to the Histiodella kristinae Phylozone and to the younger, unzoned interval. The chitinozoans are well preserved and the yield is high. The fauna is assigned to the Cyathochitina jenkinsi Zone and to an undefined interval. The abundance and diversity of the chitinozoan assemblages display a cyclic pattern, which is related to changes of the oceanic watermass in the foreland basin. The new chitinozoan species Belonechitina nevillensis n. sp., Belonechitina uniformipunctata n. sp., and Cyathochitina cormorani n. sp. are described.
Sequence stratigraphy, biotic change, 87Sr/86Sr record, paleoclimatic history, and sedimentation rate change across a regional late Cenozoic unconformity in Arctic Canada
Authors: McNeil D H , Duk-Rodkin A , Dixon J , Dietrich J R , White J M , Miller K G , Issler D R
Published: April 2011

Eustasy, tectonics, and climate contributed to a remarkable MiocenePliocene regional unconformity in the BeaufortMackenzie area of Arctic Canada. The unconformity extends from beneath deep basin turbidites on the continental rise, upslope across an erosional paleocontinental shelf, onto the cratonic margin as a regional paleosurface (peneplain) in the Mackenzie Delta area, and into pediment surfaces cut into the orogenic highlands of the Richardson Mountains. The unconformity was initiated by shelf exposure during latest Messinian or earliest Pliocene eustatic lowstand and was accentuated by tectonic uplift from the culmination of a major Late Miocene compressional pulse on the basin margin. Palynomorph, benthic foraminiferal, strontium isotopic, paleomagnetic, and radiometric data document the climatic and chronological events surrounding the unconformity. A widespread hardground (K-59 limestone) occurs at the unconformity and caps the Late Miocene Akpak Sequence. The hardground yields the benthic foraminifera Cibicides grossus, a regional marker in the Arctic Pliocene, and the bryozoan Adeonella sp. aff. A. polystomella, previously known from temperate North Atlantic environments. The 87Sr/86Sr data and new biostrati gra phic data indicate that the C. grossus Zone in the BeaufortMackenzie area may be younger than previously estimated, ranging into the earliest Pleistocene. Late Miocene regional uplift across the cratonic margin, coupled with eustatic lowstand followed by Early Pliocene tectonic quiescence and dry cool climatic conditions, combined to produce widespread erosion (pediments and peneplanation). Rapid erosion contributed to the >4 km-thick, PliocenePleistocene Iperk Sequence and a 23-fold increase in sedimentation rates relative to the Early and Middle Miocene.
New UPb age constraints on latest Cretaceous magmatism and associated mineralization in the Fawnie Range, Nechako Plateau, central British Columbia
Authors: Friedman R M , Diakow L J , Lane R A , Mortensen J K
Published: April 2011

New UPb ages and KAr dates, primarily for rocks proximal to mineral occurrences in the Fawnie Range of central British Columbia, document latest Cretaceous (ca. 7466 Ma) continental-arc igneous activity and date associated base and precious metal mineralization. UPb ages of ca. 7369 Ma for the Capoose pluton and hypabyssal to extrusive garnet rhyolites at the Capoose prospect demonstrate a latest Cretaceous age for mineralization and a likely plutonic source for mineralizing fluids. A UPb age of ca. 67 Ma for a late mineralized felsic dyke and two KAr dates (ca. 70 and 68 Ma) for hornfelsed Jurassic volcanic rocks at the BlackwaterDavidson prospect constrain a latest Cretaceous age for mineralization. A UPb age of ca. 74 Ma for a fine grained diorite sill that cuts a significant epithermal gold vein at the Tsacha prospect places a minimum age on mineralization at this probable Jura-Cretaceous deposit and documents latest Cretaceous magmatism. Latest Cretaceous KAr dates are reported for an andesite flow adjacent to the Eocene Holy Cross deposit (ca. 66 Ma), about 35 km north of the Fawnie Range, and a Kasalka Group rhyolite (ca. 68 Ma) exposed near the western margin of the Nechako Plateau. Latest Cretaceous magmatism and mineralization in the Fawnie Range represent the waning stages of Bulkley suite magmatism and porphyry-style mineralization, which was concentrated along the western margin of the Nechako Plateau at circa 8870 Ma. The distribution of latest Cretaceous arc igneous rocks along the North American Cordilleran is reviewed and tectonic implications discussed.
Time-frequency analysis of deep crustal reflection seismic data using Wigner-Ville distributions
Authors: Vasudevan Kris , Cook Frederick A
Published: April 2011

One important component of deep crustal reflection seismic data in the absence of drill-hole data and surface-outcrop constraints is classifying and quantifying reflectivity patterns. One approach to this component uses a recently developed data-decomposition technique, seismic skeletonization. Skeletonized coherent events and their attributes are identified and stored in a relational database, allowing easy visualization and parameterization of the reflected wavefield. Because one useful attribute, the instantaneous frequency, is difficult to derive within the current framework of skeletonization, timefrequency analysis and a new method, empirical mode skeletonization, are used to derive it. Other attributes related to timefrequency analysis that can be derived from the methods can be used for shallow and deep reflection seismic interpretation and can supplement the seismic attributes accrued from seismic skeletonization. Bright reflections observed from below the sedimentary basin in the Southern Alberta Lithosphere Transect have recently been interpreted to be caused by highly reflective sills. Timefrequency analysis of one of these reflections shows the lateral variation of energy with instantaneous frequency for any given time and the lateral variation of energy with time for any instantaneous frequency. Results from empirical mode skeletonization for the same segment of data illustrate the differences in the instantaneous frequencies among the intrinsic modes of the data. Thus, timefrequency distribution of amplitude or energy for any signal may be a good indicator of compositional differences that can vary from one location to another.
Introduction to the special issue of Canadian Journal of Earth Sciences: The Nechako NATMAP Project of the central Canadian Cordillera
Authors: Struik Lambertus C , MacIntyre Donald G
Published: April 2011

The Canadian Cordillera in central British Columbia has seen the Mesozoic subduction of an oceanic terrane; the amalgamation of volcanic-arc terranes; continued intermittent Mesozoic compression and magmatism; and Tertiary wrenching, extension and magmatism. Except in its northernmost mountain ranges, the area is extensively covered in glacial drift and thin veneers of Tertiary volcanic rocks. In 1994, a group of scientists and technologists believed they could understand that cover, see through it, and discover the components of that collision and extensional orogen. They would apply modern techniques of isotopic and paleontological geochronology; lake-sediment, till, and plant geochemistry; detailed gravity, magnetic, radiometric, paleomagnetic, and electromagnetic surveys; and isotopic and trace element lithochemistry, as they conducted extensive bedrock and surficial mapping. This special issue summarizes a cross-section of the scientific contributions derived from that mapping conducted under the auspices of the Nechako NATMAP Project. It demonstrates the absolute necessity of applying modern isotopic and paleontologic geochronology to understand the Phanerozoic geology of the Cordillera. It emphasizes the necessity of detailed aeromagnetic surveys (500 m or less line spacing) in looking through covered terranes at anything more than 1 : 250 000 scale. And, it shows the immense utility of applying various geochemical techniques to solve geological problems and establish baselines for future research and economic development. Bedrock and surficial mapping in the central Cordillera, using these and other techniques, have established the nature and timing of Mesozoic crustal growth, Tertiary crustal thinning, and the associated formation of mineral deposits.
Paleomagnetism of the Quottoon plutonic complex in the Coast Mountains of British Columbia and southeastern Alaska: evidence for tilting during uplift
Authors: Butler Robert F , Gehrels George E , Crawford Maria Luisa , Crawford William A
Published: April 2011

The Quottoon plutonic complex (part of the great tonalite sill) was emplaced into eastern parts of the Coast shear zone along the west flank of the Coast Mountains. UPb crystallization ages range from 72.3 to 55.5 Ma. A regional compilation of KAr hornblende dates from the tonalite sill indicates a west to east decrease from ~60 Ma to ~54 Ma across the intrusive suite. Paleomagnetic samples were collected at 160 sites ([Formula: see text] 8 samples per site) along six transects across the Quottoon complex between the Skeena River and Willard Inlet. Directions of characteristic remanent magnetization (ChRM) were successfully determined by principal component analysis of thermal demagnetization data for about half of the samples collected. Site-mean ChRM directions were determined for 56 sites from the Skeena River, Quottoon Inlet, Steamer Passage, and Wales Island transects, using criteria of [Formula: see text] 4 sample ChRM directions per site and 95% confidence limit (α95) [Formula: see text] 25°. For Filmore Island and Willard Inlet, few sites provided adequate determinations of site-mean ChRM directions, but many sample ChRM directions were well determined and consistent. The mean direction from the Skeena River  Quottoon Inlet collection is nearly concordant with the expected Eocene direction. Mean directions from other transects have clockwise-rotated declinations and inclinations that are shallower than the expected direction by up to 23°. Consistent with expectations for east-side-up tilting of crustal panels, sites from the western part of each transect have mean directions farther from the Eocene expected direction than do sites from the eastern part of the transect. The magnitude of east-side-up tilt varies along strike: the Skeena River to Quottoon Inlet segment experienced little or no tilt; Steamer Passage south of Portland Inlet records 15° tilt; north of Portland Inlet, tilts are 40° for Wales Island and 35° for Filmore Island; farther north, tilt decreases to 12° for Willard Inlet. Tilting was driven by Eocene extension of the Coast Mountains, with tilted crustal panels bounded by northwest-striking, east-side-down normal faults and northeast-striking transfer faults or shear zones. The ACCRETE seismic transect imaged east-dipping reflectors down to ~15 km depth, which likely correspond to the east-side-down normal faults. The most significant of the northeast-striking transfer structures must underlie Portland Inlet. Based on a tilting domino model, about 30% extension is required to produce the 40° tilt of crustal blocks at Wales and Filmore islands.
Holocene eruptive history of Mount Baker, Washington
Authors: Kovanen D J , Easterbrook D J , Thomas P A
Published: April 2011

New radiocarbon dates associated with volcanic ashes and lahars improve our understanding of the volcanic activity of Mount Baker, a 3284 m-high, andesitic stratovolcano in the North Cascades, Washington. The geologic record shows that during the Holocene, four ashes and at least seven lahars were deposited on the flanks of Mount Baker and in the nearby North Cascades. Here, we document the ages of three previously undated ashes, the Schriebers Meadow scoria, the Rocky Creek ash, and the Cathedral Crag ash. Because Mount Baker lies at the head of the Nooksack drainage, eruptive activity may influence areas downstream. Understanding the timing and characteristics of volcanic eruptions from Mount Baker is useful from volcanic hazard and paleoclimatological perspectives.
Late Neoproterozoic cap carbonates: Mackenzie Mountains, northwestern Canada: precipitation and global glacial meltdown
Authors: James Noel P , Narbonne Guy M , Kyser T Kurtis
Published: April 2011

The 3-27 m-thick cap carbonate overlying "Marinoan" Ice Brook Formation glacigene sediments and Keele Formation carbonate and terrigenous clastic rocks consists of two distinctive stratigraphic units. A lower, splintery, buff-weathering, microcrystalline dolostone of extensive lateral uniformity comprises mm-laminated peloidal sediment with local, low-angle, hummocky-like cross-stratification, micro-ridges, and synsedimentary tepees, all elongated perpendicular to depositional strike. This dolostone is unconformably overlain by an upper limestone that exhibits pronounced facies variation from inboard peloidal lime grainstone and mudstone to shelf-edge cementstone to outboard lime wackestone and mudstone. Calcite cementstones range from isolated crystal fans in laminated limestone to huge, decimetre-scale crystal arrays, to hemispherical and elongate crystal stromatolites wholly composed of acicular crystals that form decametre-scale reeflike structures. Crystal stromatolites are precipitates and replaced microbiolites that constructed biostromes and bioherms, like those on many flat-topped, reef-rimmed platforms. The calcite crystals have all the physical and chemical attributes of neomorphosed aragonite. This aragonite extensively replaced sediment and microbiolite just below the sea floor and grew upward into the overlying water column. Such interpreted massive synsedimentary replacement is rare in geological history and attests to the highly saturated state of the immediate postglacial ocean. All sediment is interpreted to have been CaCO3 originally. Low and constant δ18O values reflect diagenetic modification of these carbonates, although chemical attributes, such as Sr and C isotopes in some lithologies, are near pristine. Lower dolostones, virtually identical to most other coeval Marinoan caps worldwide, were part of a global precipitation event of remarkable similarity. Upper limestones are a more local phenomenon, deposited during sea-level rise in an aragonitic sea returning to equilibrium after global glaciation. Low 87Sr/86Sr ratios and varying δ13C values with carbonate sedimentary facies indicate that both units must have formed relatively rapidly, prior to significant fluvioglacial runoff, or that the influence of this runoff on the chemistry of seawater along continental shelves was minimal. The cap carbonate is thus interpreted to have formed in two steps: (1) during initial marine ice melting accompanied by oceanic overturn and upwelling, preceding continental margin rebound, and (2) during initial stages of sea-level rise accompanying continental deglaciation. While confirming brief, but extensive, carbonate precipitation from an ocean highly perturbed by global glaciation, the rocks also suggest that this event did not permanently affect either late Neoproterozoic ocean chemistry or the contained marine biosphere.
A new crocodylian (Archosauria) from the basal Paleocene of the Red Deer River Valley, southern Alberta
Authors: Wu Xiao-Chun , Brinkman Donald B , Fox Richard C
Published: April 2011

Borealosuchus griffithi, sp. nov., is described on the basis of an incomplete skeleton from the basal Paleocene, southern Alberta. This new species records one of a few basal Cenozoic occurrences of Crocodylia so far known. B. griffithi is most distinctive in having a markedly laterally concavo-convex snout; a deep, elongate recess or fossa on the anteroventral surface of the jugal; and a large, nearly rectangular incisive foramen. Within Borealosuchus, B. griffithi probably takes a "more crownward" position than does B. sternbergii of the late Late Cretaceous. With additional information from the new species, the diagnosis of Borealosuchus is revised.
Cranial anatomy of a new crocodyliform (Archosauria: Crocodylomorpha) from the Lower Cretaceous of Song-Liao Plain, northeastern China
Authors: Wu Xiao-Chun , Cheng Zheng-Wu , Russell Anthony P
Published: April 2011

Rugosuchus nonganensis, a new genus and species of crocodyliform, is erected on the basis of its peculiar cranial features. This late Early Cretaceous species represents the second, and most complete, crocodyliform known from northeastern China. Its discovery is significant for our understanding of both the local vertebrate fauna and its stratigraphical correlations, and the paleobiogeography of the Crocodyliformes. The palatine contribution to the anterior border of the choana excludes the new form from the Eusuchia, and evidence from osteoderms (not detailed in the present paper) suggests that the new form appears to be phylogenetically closer to the Eusuchia than to the Goniopholididae. Therefore, comparisons are made primarily with those taxa which have a closer relationship to the former than the latter. The unsculpted, depressed, and lobe-like posterolateral process of the squamosal is further demonstrated to be ontogenetically variable and thus inappropriate for use as a character in phylogenetic analyses.
INTERPRETATION OF THE ALERT ANOMALY IN GEOMAGNETIC VARIATIONS
Authors: Rikitake T. , Whitham K.
Published: April 2011

The theoretical basis for the interpretation of the Alert anomaly in geomagnetic variations has been reexamined. Under the uniform horizontal inducing field approximation, the electromagnetic response of an infinite elliptical cylinder of infinite conductivity has been derived, and from this the response for the upheaval of a half-elliptical conductor from a highly conducting mantle. The results have been extended to an asymmetric upheaval of the conducting mantle. A theory has also been developed of the electromagnetic response of an elliptic cylinder which is useful for application to the finite conductivity case.The electromagnetic coupling between an infinite circular cylinder and an underlying conducting layer has been investigated as far as the second-order approximation. An exact solution has then been obtained for the infinite conductivity approximation, and useful examples calculated.The situation at Alert has been reexamined following this work which reduces one of the difficulties of the earlier interpretation. An upheaval of about 100 km of the 1400–1500 °C isotherm to within 25–30 km of the surface appears capable of accounting for the gross characteristics of the response but the solution is certainly not unique and may be in error by as much as 60%. The asymmetry in the response is difficult to explain quantitatively. The response parameters thought to be most useful have been clearly defined and the ambiguity in the electromagnetic response solutions illustrated. Suggestions for further progress are made. Brief mention is made of preliminary magnetotelluric and gravitational studies at Alert.
POSSIBLE MECHANICAL FUNCTION OF SHELL PLICATION IN A TRIASSIC BRACHIOPOD
Authors: Westermann Gerd E. G.
Published: April 2011

A sample of 100 Spiriferina stracheyi (Salter) from a single chronodeme of the Anisian Whitehorse formation, Alberta Rocky Mountains, is the subject of covariation studies (individual allomorphosis) in the parameters half width + length mean ("size"), half width/length ratio, thickness, apical angle of fold and sulcus boundaries (fold–sulcus angle), plicae frequency, and apical angle between second right and left plicae from the median (plicae angle). Changes of growth rates for half width/length and plicae frequency at a mean "size" of 10 mm suggest the attainment of maturity; parameters vary nearly independently from "size" in the sample of mature specimens. The variation in the parameters is unusually great. Significant correlation of −0.36 exists between half width/length and plicae angle, i.e. the plicae are more widely spaced in long ("rounded") valves than in wide ("alate") valve variants. A corresponding correlation of +0.61 exists for plicae frequency, wide valves averaging double as many plicae as narrow valves. The same correlations are present in a Himalayan sample of this species.Although, usually, shell plication of bivalved filter-feeders with accretionary growth may simply result from ecologic–physiologic functions of a plicate commissure, in the species here studied the plicae themselves might have had a mechanical function, i.e. the shell forming a corrugated membrane surface in which the "wavelength" increases with the axial growth of the membrane.
SOME OBSERVATIONS ON THE INFLUENCE OF CLIMATIC AND TERRAIN FEATURES ON PERMAFROST AT NORMAN WELLS, N.W.T., CANADA
Authors: Brown R. J. E.
Published: April 2011

During the summers of 1959 and 1960, field observations of the influence of some climatic and terrain features on permafrost were carried out at Norman Wells, N.W.T. Five sites, all underlain by perennially frozen ground, were selected for investigation. One site was a Thornthwaite potential evapotranspiration site with a vegetation cover of Kentucky bluegrass growing on clayey silt. The four remaining sites included the various types of vegetation growing naturally in the Norman Wells region. The tree growth was predominantly spruce with some tamarack. Sphagnum and other mosses, lichen, and sedge comprised the ground cover. The peat layer varied in thickness from 7 in. to 2 ft and the mineral soil was predominantly clayey silt. At each site, measurements were taken of evaporation (including potential evapotranspiration), net radiation at the ground surface, depth of thaw, and ground temperatures in the thawed layer and the permafrost. Although field conditions dictated the use of crude measuring devices, some quantitative information was obtained on the relative importance of these climatic and terrain features in the permafrost environment. Potential evapotranspiration was higher in the Kentucky bluegrass at the Thornthwaite site than in Sphagnum and in other mosses, in lichen, and in sedge at the other sites. Net radiation values appeared to be slightly higher for moss than for lichen. The depth of thaw under moss and lichen was less than in areas supporting other types of plant growth. Ground temperatures in the thawed layer and in the permafrost showed the same characteristics, being lower in the moss and lichen areas.
HEAT FLOW DETERMINATIONS IN THE CANADIAN ARCTIC ARCHIPELAGO
Authors: Law L. K. , Paterson W. S. B. , Whitham K.
Published: April 2011

Three heat flow determinations a were made in M'Clure Strait between Prince Patrick and Banks Islands in the northwestern part of the Arctic Archipelago of Canada. The three stations lie within 55 km of a point some 130 km SSW. of Mould Bay, Prince Patrick Island, and yield a weighted mean heat flow of 0.84 ± 0.09 μcal cm−2 s−1, or 57% only of the worldwide continental average. The measurements were made from sea ice in water depths of some 430 m using a thermal probe and portable equipment carried in a fixed-wing aircraft.Instrumental limitations and errors are discussed, together with environmental factors. The uncertainties in interpreting this result as a truly subnormal equilibrium heat flow are outlined but it is concluded that the calculated systematic errors are unlikely to exceed 25%. Consequently in the absence of any known major perturbing effect, it must be concluded that the structure responsible for the suppression of vertical magnetic held variations at Mould Bay observatory does not extend 130 km to the south, is not produced by an anomalously high near-surface temperature, or is of late-Quaternary origin.
AN OCCURRENCE OF CORVASPIS (OSTRACODERMI) IN CANADA
Authors: Dineley D. L.
Published: April 2011

The heterostracan ostracoderm Corvaspis has been discovered in rocks possibly of marine origin and Silurian age in the northern Yukon, Canada. The specimens indicate a form very closely similar to C. kingi but no other specifically identifiable vertebrate remains occur with them to resolve the problem of their age.
ALLUVIAL CONE CONSTRUCTION BY ALPINE MUDFLOW IN A HUMID TEMPERATE REGION
Authors: Winder C. G.
Published: April 2011

In a humid, temperate area of central-western Alberta, a mudflow occurred along Hell's Creek, a short tributary of the Smoky River in July, 1962, during a heavy rainstorm. Flows had not occurred during the previous 3 years, even though rains of comparable intensity had fallen. The source area is a steep-sided rock amphitheater, cut in deformed shales and siltstones, and almost devoid of vegetation. The mud moved over a mile in a narrow stream valley and spread across the lower part of an alluvial cone. The exposed lithology of the cone suggests that mudflow is the principal agent in construction of this and other cones of the region. Deposition of the cone has diverted the course of a large river.
PALAEOMAGNETISM OF DIABASE DYKES OF THE CANADIAN SHIELD
Authors: Fahrig W. F. , Gaucher E. H. , Larochelle A.
Published: April 2011

Some areas of the Canadian Shield are profusely intruded by swarms of subparallel basaltic dykes. These typically have a diabasic texture and formerly were considered to be strictly the intrusive equivalents of tholeiitic flood basalt.About 650 oriented samples were collected from about 25 dyke swarms and preliminary palaeomagnetic data from six of them are presented here. The Mackenzie swarm has a K–Ar age of 1 295 million years, occurs throughout the western Canadian Shield, and is the most extensive swarm of basic dykes known anywhere in the world. The other swarms are the Molson dykes (1 445 m.y.) in northeastern Manitoba, the Marathon dykes (1 810 m.y.) just north of Lake Superior, the Sudbury dykes (1 285 m.y.) of southeastern Ontario, the Matachewan dykes (2 485 m.y.) of western Quebec and northeastern Ontario, and the Abitibi dykes (1 230 m.y.), which occur from Sault Ste. Marie, Ontario, to Lake Mistassini, Quebec.The palaeomagnetic virtual pole positions of six swarms were derived from the mean of their measured remanent magnetization directions. These directions of magnetization were determined from the samples after they were magnetically washed in an a-c. field of 80 or 130 oersteds. The reasons for the dispersion within the individual swarms are discussed. The pole positions of the Sudbury and Mackenzie dykes are almost identical and the two swarms are the same age within the limits of analytical uncertainty. However, basalt of the Sudbury swarm is alkalic and more undersaturated than basalt of the Mackenzie dykes.No evidence was found to contradict the usual assumption that unaltered basic igneous rocks of this type acquire and generally retain a stable magnetization which was parallel with the earth's magnetic field at the time of the dyke intrusion.
INFLUENCES OF ABSOLUTE AND PARTIAL HYDROLOGIC BARRIERS ON PUMP TEST RESULTS
Authors: Nind T. E. W.
Published: April 2011

A review is presented of the method of images as used in situations in which there is an absolute hydrologic barrier, and possible sources for misinterpretation of pump test results are stressed. The method is then applied to the case of non-equilibrium flow in the presence of a partial hydrologic barrier, under certain limitations. It concluded that the presence of such a barrier may not be reflected in any discernible way in drawdown–time curves resulting from pump tests, or, if it is reflected, may easily be overlooked.
THE PETROLOGY OF TWO ZONED SCAPOLITE SKARNS
Authors: Shaw Denis M. , Schwarcz Henry P. , Sheppard Simon M. F.
Published: April 2011

A spheroidal skarn body at Gib Lake, Pontiac County, Quebec, occurs in phlogopite marble, and shows concentric zones several centimeters thick. The zonal sequence is (a) core of blue scapolite; (b) pargasite–albite intergrowth; (c) pure phlogopite; (d) serpentinized forsterite–dolomite marble. The minerals have been analyzed. A zoned skarn with a similar sequence was found 15 miles south on Calumet Island.Phase assemblages are consistent with upper amphibolite facies metamorphism. The zonal sequence is explained by reaction between a spheroidal quartzo-feldspathic mass and an enveloping dolomitic marble through radial diffusion of Mg (inward) and Si, Al (outward), establishing local equilibrium between adjacent phases. Mg, Al, and Si behaved as phase-determining inert components, Ca was probably in excess, while Na, K, H, Cl, C, F, S were perfectly mobile.
LATTICE PARAMETERS OF MELILITE SOLID SOLUTIONS AND A RECONNAISSANCE OF PHASE RELATIONS IN THE SYSTEM Ca2Al2SiO7 (GEHLENITE) – Ca2MgSi2O7 (AKERMANITE) – NaCaAlSi2O7 (SODA MELILITE) AT 1 000 kg/cm2 WATER VAPOR PRESSURE
Authors: Edgar A. D.
Published: April 2011

The extent of melilite solid solutions has been determined for the systems gehlenite–soda melilite, akermanite–soda melilite, and gehlenite–akermanite–soda melilite at 800 °C and 1 000 kg/cm2[Formula: see text] Approximately 50 weight % NaCaAlSi2O7 will form melilite solid solutions with both gehlenite and akermanite but the extent of complete solid solutions in the gehlenite–akermanite–soda melilite system is very limited at this temperature. Lattice parameter determinations of melilite solid solutions indicate that there is a small but significant change in both a and c parameters with increasing soda melilite in the gehlenite–soda melilite system. In the gehlenite–akermanite–soda melilite system, although the range of complete solid solution is very limited, melilites form more than 90% of the products in most compositions and their lattice parameters can be correlated approximately with their bulk compositions, A rapid X-ray method has been developed to determine the approximate compositions of melilites in this system. Comparison is made between the synthetic samples and natural melilites.A reconnaissance of subsolidus phase relations indicates that phase relations are very complex and that only over a very small compositional range can these systems be considered binary or ternary. These studies also indicate that the relations reported by Nurse and Midgley in 1953 should probably be modified. Although the composition NaCaAlSi2O7 does not synthesize only a melilite under the conditions used in this study, it is believed that this is the correct composition of the sodium-bearing end-member.
GEOCHEMISTRY OF THE YELLOWKNIFE VOLCANIC ROCKS
Authors: Baragar W. R. A.
Published: April 2011

Results of rapid-method chemical analyses of samples taken at about 500-ft stratigraphic intervals through two sections of Yellowknife Group volcanic rocks are presented in graphical and composite form. The Yellowknife section is about 40 000 ft thick with the base undefined; the Cameron River section, about 45 mi northeast, is about 7 000 ft thick and may be complete.Two aspects of the volcanic chemistry considered are (1) variation in composition with stratigraphic height; (2) bulk composition of the volcanic rocks.Chemical data of the Yellowknife section define two volcanic cycles in each of which mafic lavas show a small but significant increase in sialic components with stratigraphic height culminating abruptly in acidic layers. The Cameron River section shows a similar but less well-defined trend. Iron–magnesium ratios stage a succession of systematic increases, each persisting for a few thousand stratigraphic feet, but no overall systematic variation. The two types of chemical variation correspond to calc-alkali and tholeiitic differentiation trends respectively. The tholeiitic trend is attributed to fractionation in high-level magma chambers, demonstrated for Yellowknife magma by the Kam Point sill, and the calc-alkali trend to contamination of tholeiitic magma by sialic crust.Frequency distribution diagrams show Yellowknife volcanic rocks to be similar to Chayes' circumoceanic basalts in TiO2, CaO, and MgO and to his oceanic basalts in Al2O3. The characteristic rock type is basalt.
SILURIAN STROMATOPOROIDS OF THE MATAPEDIA–TEMISCOUATA AREA, QUEBEC
Authors: Stearn Colin W. , Hubert Claude
Published: April 2011

Stromatoporoids are abundant in parts of the Sayabec, St. Leon, and Mont Wissick formations of Wenlock and Ludlow age in eastern Quebec, Canada. The fauna is a mixture of species from Wenlock strata of northern Europe, the Wenlock and Ludlow beds of Baie des Chaleurs, Quebec, and Niagaran rocks of the Great Lakes region. Clathrodictyon crickmayi and Stromatopora prima show the affinity of the fauna to that described by Parka from Baie des Chaleurs. Densastroma astroites indicates a close connection of the fauna with the rocks of Wenlock age in England and the Baltic area. Stromatopora antiqua shows the affinity of the fauna to that of central North America. Ecclimadictyon fastigiatum is a widespread species in all these regions. A new species of Actinodictyon (A. quebecense) is described. Two unnamed species of Stromatopora and Clathrodictyon cf. podolica make up the rest of the fauna.
A RE-EXAMINATION AND RE-INTERPRETATION OF TIDE GAUGE DATA FOR CHURCHILL, MANITOBA
Authors: Barnett D.M.
Published: April 2011

Tide gauge data from Churchill, Manitoba, for the period 1928–1939 are reviewed and rejected as inaccurate. The rate of uplift proposed by Gutenberg on the basis of these data therefore is rejected also. Data from 1940 to 1964 are subjected to statistical analysis, which indicates an apparent lowering trend of water level. Linear regression suggests a rate of 2 ft per century.
MINERALOGY AS AN INDICATOR OF LONG-TERM CURRENT FLUCTUATIONS IN BAFFIN BAY
Authors: Marlowe J. I.
Published: April 2011

A study of core samples from Baffin Bay indicates that gravel and coarse sand occur in all parts of the bay. Fragments in this size range are considered to have been transported into the area by floating ice. This coarse-grained sediment is rich in granitic detritus, but samples from an area within approximately 200 km of the Canadian coast also contain limestone fragments. The distribution of limestone fragments on the bottom coincides closely with the track of the Baffin Land current, in which icebergs originating in areas of limestone outcrop move southward through the bay. The distribution of limestone detritus in subbottom samples, however, suggests that the Baffin Land current has in the past flowed over a wider area than it does at present.
LANCASTER SOUND SHIPBORNE MAGNETOMETER SURVEY
Authors: Barrett D. L.
Published: April 2011

The total magnetic field and the depth of water were measured along a ship's track of about 1 000 nautical miles during a shipborne magnetometer survey in Lancaster Sound and Baffin Bay in the eastern part of the Canadian Arctic Archipelago.Several magnetic anomalies on the extreme northern and southern boundaries of Lancaster Sound as well as to the east of Devon Island in Baffin Bay are characteristic of near-surface features. There is little magnetic relief in the center of the sound. The intensity of the total field decreases from south to north and then rises sharply immediately south of Devon Island. This sharp rise trends northeasterly in Baffin Bay.Several features are indicated by these data; (1) a near-surface basement on Devon and Baffin Islands, (2) a basement flexure north of Baffin Island, the whole of Lancaster Sound being downwarped with vertical movement of as much as 8 km in the north, (3) a regional fault extending along the south coast of Devon Island and trending northeast in Baffin Bay.It is concluded that this half-graben structure in. Lancaster Sound may be associated with a postulated median ridge between Greenland and North America.
MIDDLE DEVONIAN SALT FORMATIONS AND THEIR BROMIDE CONTENT, ELK POINT AREA, ALBERTA
Authors: Wardlaw N. C. , Watson D. W.
Published: April 2011

The Prairie Evaporite formation, or First Salt, of the Elk Point area contains three types of halite: chevron, clear, and brown. The chevron halite is thought to be primary and to have grown upwards from the Devonian sea floor. The origin of the clear and brown varieties is not known. Where these types occur together, the clear halite has a tendency to contain more bromide than either chevron halite or brown halite. The total range for bromide in halite from the Prairie Evaporite is from 0.004 to 0.02 weight percent (wt.%).The Cold Lake and Lotsberg formations, the lower two salts, consist of clear halite which is so low in bromide (0.0004 wt.%) that it could not have crystallized from sea water, neither could this halite have crystallized from sea water previously saturated by dissolving halite. It is probable that the lower two salts resulted from solution of halite in fresh water, with subsequent crystallization. Solution may have occurred during discharge of meteoric groundwater, while the basin was structurally low, subsequent surface evaporation having promoted crystallization. In this way, salt could have been recycled without removal from the area. Alternatively, surface runoff, and downward movement of surface runoff, may have been important in the recycling of halite.Groundwater in Devonian formations of central Alberta, and spring waters from Devonian formations in Manitoba, are saline and relatively high in bromide (0.001–0.10 wt.% Br). The bromide content cannot be explained simply by solution of halite in meteoric waters. Either these brines are modified remnants of seawater, or else there is some undefined source of bromine causing enrichment.
S-WAVE FOCAL MECHANISM STUDIES OF THE HINDU KUSH EARTHQUAKE OF JULY 6, 1962
Authors: Stevens Anne E.
Published: April 2011

The mechanism of energy release at the origin or focus of the Hindu Kush earthquake of July 6, 1962, was studied by comparing recorded and theoretical P (longitudinal) and S (transverse) ground displacements produced at large distances from the focus by a system of forces acting at the origin. S-Wave polarization angles were used to solve a set of S-wave mechanism equations for the orientation of the two focal models considered, a single-couple and a double-dipole force system acting at a point focus. These models may be interpreted tectonically in terms of faulting and stress release, respectively, in the focal region. The double-dipole focal model gave the better fit to the S data and was also consistent with P-wave and surface-wave data for this earthquake. The mechanism type and force orientation of the 1962 Hindu Kush earthquake were shown to characterize 56 previous earthquakes in the same focal region. Hence the focal mechanism of all intermediate focus Hindu Kush earthquakes may be considered to be the double-dipole type with pressure and tension axes dipping at about 45°, roughly perpendicular to the trend of the Hindu Kush mountain system, and with the intermediate stress axis lying horizontally along the trend.
A BIOSEQUENCE OF SOILS OF THE ROUGH FESCUE PRAIRIE – POPLAR TRANSITION IN SOUTHWESTERN ALBERTA
Authors: Dormaar J. F. , Lutwick L. E.
Published: April 2011

A biosequence of soil profiles, ranging from Black through various stages of Dark Gray to Eluviated Dark Gray Chernozems and a Degraded Brown Wooded soil, is found under a sequence of vegetation ranging from rough fescue prairie (Festuca scabrella association) to encroaching poplar (Populus spp.) and fir trees (Pseudotsuga taxifolia (Poir.) Britt.) in the Porcupine Hills of southwestern Alberta. Samples were gathered to establish the differential physical and chemical changes that have occurred in the soils over an 80-year period.Increased eluviation accompanied a reduction in the percentage of exchangeable calcium but it remained the dominant exchangeable cation in all horizons. Most of the exchange capacity arises from the organic matter. The exchange sites are mainly pH-dependent. The changes in the organic matter, because of the encroachment of trees, are more strikingly evident than are the changes in the mineral matter.Infrared absorption spectra of electrodialyzed humic acids display a conspicuous change in spectral pattern between 2 500 and 1 800 cm−1. There are indications of increased acidity and increased aromaticity in the humic acids of the B horizon as eluviation progresses.
THE EXTERNAL APICAL CAVITY OF STROPHOMENACEAN BRACHIOPODS
Authors: Crickmay C. H.
Published: April 2011

Large collections of strophomenacean brachiopods from many Ordovician and Silurian localities have been searched for specimens with uneroded beaks. A few have been found, and these have been prepared in sagittal section. The apical cavity is found to have no primal exterior opening. Therefore it cannot be interpreted as a vestigial pedicle foramen. It seems, rather, to be a vacuity formed for no special function but merely incidentally during the early stages of shell making.
EXPERIMENTS ON DENSITY AND TURBIDITY CURRENTS: II. UNIFORM FLOW OF DENSITY CURRENTS
Authors: Middleton Gerard V.
Published: April 2011

The basic theory for the average velocity of uniform flow of a density current is now well established. The resistance at the bottom may be estimated from reasonable assumptions regarding the roughness of the bottom and the size of the current. The principal problem remaining is quantitative estimation of the resistance of the upper (fluid) interface. A review of the literature suggests that this resistance increases with increase in Froude number and decreases with increase in Reynolds number, and the writer's experiments support this hypothesis.As many turbidity currents are large scale and flow over low slopes of relatively small roughness it seems probable that both the bottom resistance and the resistance at the upper interface are small.