bluuebunny/crossref_metadata_2025 huggingface dataset:
Post-glacial ungulates (Cervus and Bison) from Three Hills, Alberta
Authors: Shackleton D. M. , Hills L. V.
Published: April 2011

Remains of wapiti and bison are reported from a Holocene (9630 ± 300 years BP, and 9670 ± 160 years BP) deposit at Three Hills, Alberta. The wapiti, although slightly larger, is assignable to the extant Cervus elaphus nelsoni. The bison is conspecific with the extinct Bison occidentalis. Detailed morphologic comparisons are made with extant and extinct species of both.
Orthoquartzite pebbles in Archean conglomerate, North Spirit Lake, northwestern Ontario
Authors: Donaldson J. A. , Ojakangas Richard W.
Published: April 2011

An Archean conglomerate in the North Spirit Lake area of northwestern Ontario contains rare orthoquartzite pebbles. Detailed study of these pebbles shows that mineralogically they are very mature, consisting of as much as 99.8 percent quartz and a heavy mineral suite of zircon, tourmaline, and apatite. Textures are typically bimodal, characterized by rounded sand-sized quartz grains set in a 'matrix-cement' of thoroughly recrystallized finer quartz grains. These orthoquartzite pebbles provide the first definite evidence for local tectonic stability of the Canadian Shield before deposition of the immature sedimentary rocks that form part of an Archean (>2.6 Ga) greenstone belt of the Superior Province.
Stratigraphy and tectonic setting of early Paleozoic sedimentary rocks of the Wirral–Big Lake area, southwestern New Brunswick and southeastern Maine
Authors: Ruitenberg A. A. , Ludman Allan
Published: April 2011

The rocks of the Wirral – Big Lake area occupy a transitional zone between a Silurian – Lower Devonian volcanic sequence of the Coastal and Mascarene–Nerepis Belts and turbiditic rocks of the Fredericton Trough. Most of the rocks of the Wirral – Big Lake area were included by previous workers in the "Pale and Dark Argillite Divisions of the Charlotte Group." It is proposed that the term Charlotte Group be discontinued because the subdivisions of this group do not conform with and locally cut across formational boundaries. Moreover, both Ordovician and Silurian strata were included in the Charlotte Group.The Coastal and Mascarene–Nerepis volcanic belts probably represent an ensialic island arc sequence that developed simultaneously with the deposition of sedimentary strata of the same age in the Wirral – Big Lake area and in the Fredericton Trough. It is suggested that these turbiditic sediments represent a behind-the-arc basin. The stratigraphic succession and structure of the map-area reflect several distinct stages in the closing of this basin.
A hypothesis concerning the origin of barite in Devonian carbonate rocks of northeastern British Columbia
Authors: Morrow D. W. , Krouse H. R. , Ghent E. D. , Taylor G. C. , Dawson K. R.
Published: April 2011

The sulphur isotope ratios of barite in many syngenetic barite deposits are shown to be approximately the same as those of the seawater from which they were deposited. Although the stratiform replacement barite-fluorite deposits of northeast British Columbia are epigenetic, their barite sulphur isotope ratios (δ34S) of +24.2 to +30.1‰ may indicate a late Middle Devonian time of mineralization if the sulphur in these deposits was derived from seawater.A model for barite mineralization is proposed in which mixing of euxinic (i.e., reducing) seawater with meteoric groundwater near the seaward edge of a large coastal aquifer, similar to the present-day Floridan Aquifer, caused solution of the shelf carbonates and induced low-temperature precipitation of barite in the resultant solution cavities. The extensive solution collapse that accompanied mineralization, and the coarse crystallinity and low manganese content (< 65 ppm) of the barite in northeastern British Columbia support this interpretation. The postulated Devonian paleoaquifer in northeastern British Columbia coincided with the regional distribution of solution-collapse breccias in the Stone Formation dolomite. The karsted upper surface of the Sulphur Point Formation may have been the landward recharge area for this aquifer.The variation in the mole percent SrSO4 along barite blades suggests that during precipitation there were changes in the rate of circulation of the mineralizing solution. In some places up to 30% of the barium in solution may have been precipitated. The δ34 values of later formed, strontium-enriched barites tend to be lower suggesting an isotope effect during crystallization favouring 34S in the crystalline phase.
Spatial relations of andesitic and alkaline provinces in Mexico and Central America
Authors: Robin Claude , Tournon Jean
Published: April 2011

Alkaline lavas and intrusions are extensively developed along the eastern Mexican coastal plain. A series of traps, mostly of alkali basalt parentage, occur in a faulted zone that limits the altiplano on the east. The essentially alkaline association is present along the entire Gulf Coast, and could be a southward prolongation of the Trans-Pecos province of Texas.In southern Central America, alkaline intrusive and extrusive rocks have been discovered along the Caribbean coast.This study defines the situation in time and space of the alkaline-type associations with respect to the better known andesitic series.
Lower Ordovician trilobites of the Oxford Formation, eastern Ontario
Authors: Ludvigsen Rolf
Published: April 2011

The only Lower Ordovocian trilobites known to occur in Ontario are a small collection of generally poorly preserved asaphid, bathyurid, and pliomerid trilobites from the Oxford Formation in the area between Ottawa and Brockville. This fauna consists of Bolbocephalus convexus (Billings), Gignopeltis rarus (Billings), Goniotelina subrectus (Bradley), Strotactinus salteri (Billings), and Isoteloides sp. This fauna is late Canadian and early Arenigian in age. The trilobite, conodont, and mollusk faunas indicate correlations of the Oxford Formation with the Phillipsburg 'Series' of Quebec, Fort Cassin Formation of New York and Vermont, mid- to upper St. George Group of Newfoundland, and mid-Fillmore Formation of Utah. A neotype is chosen for Strotactinus salteri.
Growth and decay of palsas and peat plateaus in the Macmillan Pass–Tsichu River area, Northwest Territories, Canada
Authors: Kershaw G. P. , Gill Don
Published: April 2011

Macmillan Pass, at 1350 m asl (above sea level), is located in the Selwyn Mountains at the Yukon–Northwest Territories border (63 °15′N, 130°02′W). This area lies within the discontinuous but widespread permafrost zone. Palsa–peat plateau complexes cover 0.7% of the 235 km2 study area and are found in bog and fen depressions at elevations from 1285–1690 m. Palsa heights range from 0.15–9.75 m and diameters from 3.25–75.0 m; peat plateaus have maximum heights of 2.5 m and maximum diameters of 225 m. Both features are vegetated by Cladina-Betula glandulosa, Cladina-Polytrichum-Cetraria, and crustose lichens-Polytrichum plant communities.Palsas and peat plateaus are windswept during winter. On surfaces which support recumbent (5–15 cm tall) plant communities there was an average of only 7.5 cm of snow during late winter 1978. Snow cover was thinner by a ratio of 1:4 compared to control areas.These permafrost features have formed since the White River volcanic ash fall of 1220 BP. On palsas and peat plateaus this ash occurs at an average depth of 21 cm and has an average thickness of 11.6 cm.Shrinkage and (or) total decay of palsas and peat plateaus has occurred during the past 34 years. In one palsa field this represents a 34% reduction of area whereas in two others, 100%. The areal extent of some peat plateaus has also been reduced.
Polyframboidal pyrite in the tills of southwestern Alberta
Authors: Stene Larry P.
Published: April 2011

This investigation shows that older tills in southwestern Alberta contain polyframboidal pyrite which is of in situ origin.
Paleomagnetism of igneous rocks from the Belcher Islands, Northwest Territories, Canada
Authors: Schmidt P. W.
Published: April 2011

Paleomagnetic results from igneous rock units on the Belcher Islands, Hudson Bay, are described. Fold tests for all units studied, as well as a contact test for the intrusive bodies, indicate that both primary (initial), and secondary (post-folding) magnetizations are present.The paleomagnetic pole position from primary directions of the oldest unit studied, the Eskimo volcanics, is situated at 40°S, 002°E (A95 = 12°) and is similar to that derived from equivalent volcanics on the mainland. The younger volcanic unit studied, the Flaherty volcanics, yielded a pole position from primary directions at 0°, 244°E (A95 = 7°). The Haig intrusions, associated with these younger volcanics, yields an almost identical pole position at 1°N, 247°E (A95 = 6°), being derived from directions which are shown to be not only pre–folding but also date from initial cooling. The Eskimo volcanics, which have been more deeply buried than the Flaherty (upper) volcanics, carry substantial components of secondary (post-folding) magnetization which yield a pole position at 19°N, 243°E (A95 = 15°), about 20° north of the pole positions derived from the youngest units.It is argued that the apparent polar wander path (APWP) constructed for the Belcher Islands is representative of the mainland Ungava Craton. Comparison with the equivalent APWP from elsewhere in North America shows that the two APWP's are at variance. Although a two-plate model could be advanced, perhaps a more conservative interpretation is to extend the existing North American APWP eastward to include the Belcher–Ungava APWP, that is, to favour a one-plate model.
Glacial Lake Coppermine, north-central District of Mackenzie, Northwest Territories
Authors: St-Onge Denis A.
Published: April 2011

Field observation along the Coppermine River valley has revealed extensive deposits related to the presence of a major lake in late-glacial time. Numerous deltas determine a water level at approximately 360 m above sea level (asl). It is proposed that this former lake be called Glacial Lake Coppermine. Air-photo interpretation indicates that the valley was dammed by a glacial lobe covering the lowlands north of Coppermine Mountains and Dismal Lakes. During a high phase, the lake drained westward through the Dismal Lakes system to a high-level Great Bear Lake. Organic material, found in sediments infilling a river channel cut into deltaic sediments resting on top of a thick varve sequence, has yielded two 14C dates: 8400 ± 80 (GSC-2959) on wood at the base of the channel and 3210 ± 60 (GSC-2998) on peat at the top of the fill.
A model for P-wave nodal solutions
Authors: Geuer J. W. , Hasegawa H. S.
Published: April 2011

A three-dimensional modelling tool has been constructed to facilitate the study of P-wave nodal solutions. This model consists of two basic interrelating parts: a fixed hemispherical basin that represents the lower half of the focal sphere and a cursor consisting of three orthogonal components, one plane representing the fault, another representing the auxiliary plane, and a third containing the (deviatoric) stress vectors. This model displays clearly all the important parameters associated with P-wave nodal solutions, in contrast to conventional (e.g., equal-area) two-dimensional projections that have inherent limitations. In addition this model is useful as a pedagogical tool; this model can also be used as a check on theoretical calculations, which, depending on the technique used, may be nonunique, for the case where surface-wave data are incorporated with body-wave data to place more stringent restrictions on fault plane solutions.
Analyse structurale et relations déformation–métamorphisme, Groupe d'Oak Hill, région du mont Sainte-Marguerite, Appalaches du Québec
Authors: Charbonneau J.-M. , St-Julien P.
Published: April 2011

Stratigraphic units in the Mount Sainte-Marguerite area belong to the Oak Hill Group and form a complex allochthonous syncline northwest of the Notre-Dame anticlinorium. These units were folded three times. The first two phases of folding (attributed to the Taconic Orogeny) produced domes and structural basins flattened and stretched along their plunge. These structures plunge with an average angle of 30° to the northwest. The first two phases of folding also produced interference patterns in the form of hooks and crescents along with complex multilobate forms. A third deformation slightly affected the interference patterns.Each phase of deformation was accompanied by low-grade dynamothermal metamorphism. The second metamorphic episode reached the quartz–albite–muscovite–chlorite grade of the greenschist fades. This event was active for some time after the end of the second phase of deformation. [Journal Translation]
Detrital mineralogy and petrology of deep-water continental margin sediments off Newfoundland
Authors: Alam Mahmood , Piper David J. W.
Published: April 2011

Seventeen long piston cores have been examined from the continental slope and rise off the Grand Banks and from nearby seamounts. Most cores penetrate Holocene and late Wisconsinan sediment. Four main facies groups are distinguished: A — red terrigenous sediment; B — gray terrigenous sediment (including turbidite sands); C — calcareous (mostly biogenic) sediment; and D — diatomaceous sediment. Facies C and D characterize the Holocene and interstadials; facies A and B were developed during stadials.Three suites of ice-rafted debris are distinguished: (i) a metamorphic-dominated suite, derived either from Greenland and Baffin Island or from local Labrador and Newfoundland ice; (ii) a carbonate-dominated suite, derived from the Arctic Islands; and (iii) a red sandstone – siltstone suite, derived from the Gulf of St. Lawrence and its environs.Three heavy mineral assemblages are recognized: on the Grand Banks slope — pyroxene, opaques, amphiboles, and garnet; in Flemish Pass — opaques, pyroxene, garnet, and tourmaline; and on the western Grand Banks rise — opaques, pyroxene, tourmaline, and garnet.In the biogenic facies C and D, which have slower rates of sedimentation and more ice-rafting corresponding to high stands of sea level, there is little geographic variation in clay mineral assemblage, with montmorillonitic minerals dominant. In the terrigenous facies A and B, which accumulated during glacio-eustatic lower sea-level stands, there is considerable geographic variation, suggesting derivation from local sources on the shelf through wave or glacial erosion.
Queen Charlotte fault zone: heat flow measurements
Authors: Hyndman R. D. , Lewis T. J. , Wright J. A. , Burgess Margaret , Chapman D. S. , Yamano M.
Published: April 2011

The heat flow pattern from the deep sea across the Queen Charlotte Terrace to the west coast of the Queen Charlotte Islands has been determined through 20 marine heat flow measurements and by 11 borehole measurements at one land site. There is a continuous transition from very high deep sea heat flow, through intermediate values on the terrace, to low continental heat flow. The deep sea values are scattered, probably reflecting hydrothermal circulation in the crust, but their mean is in agreement with the theoretical value for the 7 Ma deep sea oceanic crust. The mean heat flow at the land site of 47 mW m−2 is similar to the average for the coast Insular Belt to the south and east. The measurements on the 30 km wide 2 km deep terrace are less scattered and much lower than those on the deep sea floor. The main thermal contrast is at the seaward edge of the terrace rather than near the coast where the earthquakes of the main plate boundary are located. Numerical models suggest that no reasonable steady state ocean–continent boundary can explain the observed heat flow transition. The data are consistent with a model of oblique underthrusting of the deep sea floor beneath the terrace. The continental margin heat flow transition will tend to mask any thermal anomaly generated by fault motion, but the results imply that there is no large frictional heat generated by motion on the Queen Charlotte fault.Nine marine heat flow measurements were made at the southwestern end of Queen Charlotte Sound south of the Queen Charlotte fault zone to test the hypothesis that the sound is a zone of recent crustal extension or rifting. The measurements were limited to isolated pockets of soft sediment and to sea floor depths greater than 800 m where bottom water temperature transients are negligible. The heat flow values are fairly uniform with an average of 86 mW m−2, which is about double the mean of other Insular Belt values. The Queen Charlotte Sound values could be affected by a nearby ocean spreading centre or by sediment erosion, but they are consistent with the rift hypothesis.
Further observations on North American Tertiary orthopteroids (Insecta: Grylloptera)
Authors: Kevan D. Keith McE. , Wighton Dennis C.
Published: April 2011

The hitherto unknown female fore wing (tegmen) of the Paleocene orthopteroid, Albertoilus cervirufi Kevan and Wighton (Grylloptera; Hagloidea), has been discovered at the type locality of the species. This has facilitated a more critical assessment of the systematic affinities of Albertoilus. The relationships of the genus appear to lie, on the one hand, with the central Asiatic Late Jurassic prophalangopsine genus Aboilus (as had previously been indicated) and, on the other, with the western North American Oligocene genus Palaeorehnia. The type species of the latter, P. maculata Cockerell, 1908, is shown to be a junior synonym of "Cymatomera" maculata Scudder, 1890, described earlier from the same site. This has led to the new nominal combination Palaeorehnia maculata (Scudder) and a more definite taxonomic assignment of that species. The family group name Palaeorehniinae falls as a junior synonym of Prophalangopsinae. A new subfamily name Zeuneropterinae (Stenopelmatoidea, Gryllacrididae) is proposed for the genus Zeuneroptera Sharov. It is concluded that recent North American Prophalangopsidae (Cyrtophyllitinae) are derived directly from eastern Asiatic forebears that crossed the Beringian land bridge, and that the earlier North American members of the family (Prophalangopsinae) became extinct in the Tertiary. The family Phasmomimidae was recently indicated by us as having been previously unrecorded for North America, or later than the Early Cretaceous. It had in fact been reported erroneously as a member of the order Plecoptera from lower Upper Cretaceous strata of Labrador in 1969 (undescribed material of the same approximate age is also known from the eastern U.S.S.R.). The species in question, Palaeopteron complexum Rice, is very similar to Phasmomimella paskapoensis Kevan and Wighton, and it is possible that their respective genera might be synonymized, despite a long time interval separating their known occurrences.The tettigoniid subfamily name Pseudotettigoniinae should be attributed to Sharov, not to Kevan and Wighton. It is conceivable that the unnamed Paleocene tettigoniid described by the latter authors may be in some way related to the Oligocene pseudottigoniine genus Lithymnetes Scudder.
Un lac glaciaire dans la région du lac Minto—Nouveau-Québec
Authors: Lauriol Bernard , Gray James T.
Published: April 2011

The presence of raised beaches around Lake Minto, northern Quebec, and the washing of till in the upper part of the Leaf River valley are attributed to the existence of a glacial lake. It drained westward into the Tyrrell Sea and was dammed in the east by glacial ice that occupied the main part of the Leaf River valley. The disappearance of this ice prior to 5200 years BP led to rapid drainage of the glacial lake into an arm of the D'Iberville Sea. Postglacial isostatic rebound has subsequently led to warping of the highest water plane associated with this glacial lake, as well as those of the postglacial seas.
A new look at the stratigraphy of the Yellowknife Supergroup at Yellowknife, N.W.T. — implications for the age of gold-bearing shear zones and Archean basin evolution
Authors: Helmstaedt H. , Padgham W. A.
Published: April 2011

Based on recent detailed mapping, a revised stratigraphic column is proposed for the rocks of the Archean Yellowknife Supergroup in the Yellowknife greenstone belt. The mafic volcanic rocks of the Kam Formation, previously thought to represent the oldest supracrustal rocks of the belt, overlap remnants of an earlier volcanic–sedimentary sequence, here referred to as the Octopus Formation. As its enormous thickness makes it too unwieldy to be described as a single formation, the Kam Formation is raised to group status and subdivided into four formations. It is proposed that the Kam Group should replace the Beaulieu Group in the Yellowknife area. The Chan Formation, at the base of the Kam Group, consists of multiple gabbroic intrusions that were emplaced into a carapace of pillowed flows. The intrusions locally resemble sheeted mafic dyke complexes in Phanerozoic ophiolites, thought to represent evidence for sea-floor spreading. The Crestaurum Formation, which overlies the Chan Formation, is characterized by massive and pillowed flows interlayered with a number of laterally continuous cherts and felsic tuffs. The Townsite Formation consists of rhyodacite breccias interbedded with felsic tuffs and pillowed dacites. The Yellowknife Bay Formation, at the top of the Kam Group and comprising massive and pillowed flows with pillow breccias and numerous interflow sediments, contains all the important gold deposits mined at Yellowknife. The Banting Formation, directly overlying the Kam Group and consisting of mafic to felsic volcanics, is also given group status and subdivided into two formations. Conglomerates and sandstones of the Jackson Lake Formation, formerly thought to separate the Kam and Banting groups, are considered to represent the youngest rocks of the Yellowknife Supergroup near Yellowknife. Gold-bearing shear zones clearly postdate deposition of the Banting Group, making the rocks of this group a potential target for gold exploration. The presence of remnants of a possible spreading center at the base of the Kam Group suggests that plate-tectonic processes were active during the formation of Archean supracrustal basins in the Slave Province.
Ground-ice investigations, Klondike District, Yukon Territory
Authors: French H. M. , Pollard W. H.
Published: April 2011

Massive bodies of ground ice, 2.0–4.0 m thick, are regularly exposed in small placer mining operations in the Klondike District, Yukon. At Mayes claim, Hunker Creek, the ice is underlain by 2.0–3.0 m of creek gravels and overlain by 10.0–15.0 m of organic-rich and ice-rich muck deposits. The crystallographic and petrographic characteristics of the ice and its stratigraphic occurrence suggest that the ice body either had a segregation origin or was a residual snowbank subsequently buried by muck deposits and recrystallized.
A mammoth (Mammuthus primigenius) tooth from late Wisconsin deposits near Embden, North Dakota, and comments on the distribution of woolly mammoths south of the Wisconsin ice sheets
Authors: Harington C. R. , Ashworth Allan C.
Published: April 2011

A well-preserved third molar of a woolly mammoth (Mammuthus primigenius) was recovered from sand and gravel forming the highest (Herman) prominent strandline of Lake Agassiz near Embden in western Cass County, North Dakota. The Herman strandline is estimated to have formed about 11 500 years BP, and presumably the tooth is of similar age. Perhaps the animal lived in a tundra-like area near the Lake Agassiz shoreline.Additional evidence suggests that woolly mammoths occupied a tundra-like range south of the Wisconsin ice sheets extending from southern British Columbia to the Atlantic continental shelf off Virginia.
On the effects of thermal properties structure and water bottom temperature variation on temperature gradients in lake sediments
Authors: Wang K. , Shen P. Y. , Beck A. E.
Published: April 2011

In heat flow determinations, it is customary to treat the surface temperature variation as a finite sum of Fourier components. The medium is assumed to be homogeneous or horizontally stratified with each layer having a constant conductivity and diffusivity. This allows the effect of each periodic component to be calculated analytically. We extend this formulation to include cases where thermal conductivities in some layers of a stratified medium may vary linearly with depth as have been found in the sediments of some continental lakes. The application of this formalism to temperature measurements in Lake Greifensee and Lac Leman shows that even with excellent records of bottom temperature variations over several years, failure to take into account the conductivity variation leads to errors as high as 20% in heat flow density values, depending on the depth interval used. The combined effects of lack of detailed knowledge of conductivity structure and the use of too short and (or) inaccurate records of bottom temperature variations, leading to very significant errors, are also discussed, with particular reference to the problems arising from a lack of recognition of the existence of nonannual terms in the bottom temperature variation and the use of probes that do not penetrate the sediments deeply enough.
An Early Pleistocene proglacial succession in south-central British Columbia
Authors: Mathews W. H. , Rouse G. E.
Published: April 2011

A succession of conglomerates, sandstones, siltstones, and tills, herein named the Dog Creek Formation, is sandwiched between flat-lying basalts along Dog Creek (lat. 51°36′N, long. 122°02′–122°12′W) for about 15 km east of Fraser River. The sedimentary succession rests disconformably on underlying basaltic lavas (herein referred to as the Harpers Creek Formation), which have yielded K–Ar dates of 1.3–2.9 Ma, and in one place, on a glaciated surface carved in metavolcanic rocks of Permian(?) age. The sedimentary succession is capped by basalt flows yielding K–Ar whole-rock ages of 1.1 Ma. The occurrence of proglacial beds and a glaciated surface in south-central British Columbia, 70 km away from any high mountains capable of supporting glaciers today, testifies to a major glacial stage in Early Pleistocene time. The record of sedimentation and volcanism sheds light on early incision of the nearby valley of Fraser River.
Rubidium–strontium age and origin of uraniferous granite, Molson Lake – Red Sucker Lake area, northwestern Superior Province, Manitoba
Authors: Clark G. S. , Weber W.
Published: April 2011

Late Archean, post-kinematic, uraniferous granite and alaskite occur as several discrete large and small bodies in the 250 km long Molson Lake – Red Sucker Lake batholithic belt, in the western Gods Lake subprovince. Sampled over this length, this unit gave a Rb–Sr whole-rock age of 2495 ± 30 Ma with an initial 87Sr/86Sr ratio of 0.7053 ± 0.0023. The excellent fit of the data points suggest a common, isotopically homogeneous source of magma for the analyzed granite bodies. The initial ratio is consistent with an origin from partial melting of older calc-alkaline rocks, and evidence suggests this event accompanied granulite-facies metamorphism. Based on recent U–Pb zircon ages, this event could have occurred as much as 200 Ma prior to closure of the Rb–Sr isotopic system.An older, monzonite–quartz diorite unit gives a less well-defined age of 2690 Ma, consistent with a U–Pb zircon age from the same unit. This pluton is intrusive into older, tonalitic gneisses and is part of a widespread suite of granitoid plutonic rocks in this subprovince. This pluton gives a low, mantle-like initial ratio, indicating juvenile additions to the crust during this period of batholithic development, consistent with findings for calc-alkaline granitoids in Archean shield areas elsewhere in the world.
Pycnocrinus altilis, a new Late Ordovician channel-dwelling crinoid from southern Ontario
Authors: Eckert James D.
Published: April 2011

Pycnocrinus altilis n. sp. is described from the Upper Ordovician Georgian Bay Formation of Ontario. Closely related to P. dyeri (Meek), 1872, the cup of P. altilis is characterized by stellate ornamentation of plates comprising ridges bounded by deep subtriangular pits. Pycnocrinus altilis inhabited submarine channels in the prodeltaic regime of the Queenston deltaic complex and is inferred to have been anchored to the substrate by a distally coiled column.
U/Pb geochronology of the Coney Head Complex, Newfoundland
Authors: Dunning G. R.
Published: April 2011

The Coney Head Complex, White Bay, Newfoundland, comprises allochthonous plutonic rocks and deformed equivalents emplaced over the continental margin during the Ordovician Taconic Orogeny. A U/Pb zircon age of 474 + 2 Ma for tonalite considered as having formed by partial melting in an island arc, indicates that it crystallized in Arenig time. A microgranite dated by U/Pb (zircon + titanite) at 432 ± 2 Ma cuts the tonalite Inherited Proterozoic zircon in the microgranite indicates that the rock formed from magma generated in part by melting of continental crust or sediments derived from such crust. These relationships indicate that the microgranite was emplaced in Silurian time, after Ordovician transport of the tonalite above a continental substrate.
Changes in mass balance, velocity, and surface profile along a flow line on Barnes Ice Cap, 1970–1984
Authors: Hooke Roger LeB. , Johnson Gerald W. , Brugger Keith A. , Hanson Brian , Holdsworth Gerald
Published: April 2011

On a number of occasions between 1970 and 1984, measurements of mass balance, surface velocity, and surface elevation were made along a 10.2 km flow line extending from the divide to the margin on Barnes Ice Cap, Baffin Island, Canada. The average mass balance rate on this Arctic ice cap appears to be controlled principally by summer temperature. Years of negative mass balance dominated during the 14 year period of the study; according to our measurements, this should have resulted in a thinning of an average of 2.65 m along the flow line. Surface-elevation measurements, however, suggest that the glacier thinned only ~ 1.7 m during this time period. The slightly compressive mean transverse strain can account for ~ 0.20 m of the discrepancy between these two figures. The rest is attributed to errors in mass balance. In particular, increases in density of old firn and freezing of water in crevasses could not be evaluated adequately from our measurements.The thinning was not uniform. Near the margin the glacier thinned ~ 5 m and near the divide, ~ 2.5 m, but between 3.5 and 5.5 km from the divide there seems to have been no substantial change in thickness. Thus, along the down-glacier half of the flow line the decrease in thickness was accompanied by an increase in slope.Within 4 km of the margin the decrease in thickness resulted in a decrease in horizontal velocity of up to ~ 15%, despite the increase in slope. Higher on the glacier, however, the horizontal velocity increased ~ 5%. These changes are broadly consistent with those estimated from the changes in shear stress calculated using the hydrostatic approximation.
Paleomagnetism of Carboniferous diabase dykes from Gaspé, Quebec
Authors: Seguin Maurice K.
Published: April 2011

The reported paleomagnetic study was carried out on 53 oriented samples (156 specimens) at 10 sites in the eastern Gaspé Peninsula. All sampled geological units are composed of sub vertical diabase dykes that cut the sedimentary formations of late Early Devonian – early Middle Devonian age. The radiogenic (whole-rock K/Ar) age of these and similar dykes ranges from Late Devonian to early Middle Carboniferous (mean whole rock K/Ar age = 310 Ma). Two components were isolated. The most common component, A (D = 152°, I = +41°), is normal, whereas the second component, B (D = 315°, I = −44°), is reverse. Both components may be considered as a single one; alternatively, component A may be considered slightly older than component B. Unblocking temperatures, median destructive fields, relative frequency of occurrence of the components, and various degrees of alteration are arguments favouring the first or the second situation. The case of a single component is more probable, representing an Early Carboniferous time of acquisition of remanence (thermoremanent magnetization (TRM) probably corresponding to the time of intrusion and resetting of surrounding sedimentary rocks). The corresponding paleopole position in 148°E, 11°N. This pole position is located some 25 °to the southeast of the cluster of Carboniferous poles (mainly Middle to Late Carboniferous) for the North American craton. The significance of this discrepancy is not well understood, but it is worth noting that very recent paleomagnetic results from western Newfoundland and central New Brunswick are located closer to the paleomagnetic results of this study. The age and direction of the dyke system suggest a short period of extension following the compressive pulse of the Acadian orogeny and preceding the Alleghenian orogeny. For these reasons, the dyke system is unrelated to the initial opening of the present Atlantic Ocean.
Contrasting metamorphic terranes near Chéticamp, Cape Breton Highlands, Nova Scotia
Authors: Currie K. L.
Published: April 2011

Two contrasting metamorphic terranes can be recognized in northwestern Cape Breton Island. One terrane (Pleasant Bay complex) consists of biotite gneiss and quartzite with minor calc-silicate lenses that were metamorphosed in Late Precambrian time (about 550 Ma) and were subsequently intruded by Silurian salic and mafic plutons that were, in turn, deformed and intruded by granite in Devonian time. The other terrane (Jumping Brook complex) consists of volcanogenic and sedimentary schists of probable Silurian age that were metamorphosed in Devonian time. P–T estimates indicate that the older parts of the Pleasant Bay complex were metamorphosed at about 790 °C and 7 kbar (1 kbar = 100 MPa) at low to moderate water fugacities during a major intrusive episode. The Jumping Brook complex exhibits a single progressive metamorphic sequence now disrupted by faulting. P–T conditions during this Devonian (370–390 Ma) metamorphism varied from greenschist (300 °C at <3 kbar) to amphibolite (650 °C at 4 kbar) facies. Metamorphism probably occurred in a thermal dome. The data suggest a moderately deformed basement–cover relation between the Pleasant Bay and Jumping Brook complexes.
Rubidium–strontium ages of Archean and Proterozoic rocks in the Nejanilini and Great Island domains, Churchill Province, northern Manitoba, Canada
Authors: Clark G. S. , Schledewitz D. C. P.
Published: April 2011

Rubidium–strontium whole-rock ages are reported from the Nejanilini – Great Island area in northeastern Manitoba. This area is part of an extensive zone of Archean basement that was metamorphosed and intruded by granitic magma during the Proterozoic; it extends into Saskatchewan and southern District of Keewatin, Northwest Tertitories. An age of 2577 ± 42 Ma (1σ error) for the extensive Nejanilini granulite massif (Nejanilini domain), considered one of the oldest rock units in the area, is interpreted as a minimum age for late Archean granulite-facies metamorphism. A minimum age of 2052 ± 41 Ma (initial ratio 0.7150) for quartz–feldspar porphyry that intrudes the Seal River volcanic suite constrains the age of these volcanics and could represent a partially reset Archean age. Early Proterozoic quartzite and metagreywacke of the Great Island Group unconformably overlies the quartz–feldspar porphyry. These metasedimentary rocks, which are probably correlative with the Daly Lake Group (Saskatchewan) or the Hurwitz Group (southern District of Keewatin), give an age of 1885 ± 85 Ma, with an initial ratio of 0.7093. The age records the time of closure of the Rb–Sr isotopic system subsequent to early Proterozoic metamorphism. The age and initial ratio are consistent with published results for other, possibly correlative, metasedimentary rocks in this zone. Modelling the Rb–Sr isotopic data constrains the time of sedimentation to between ca. 2100 and 2000 Ma ago. Syn- to late-kinematic, early Proterozoic granite to granodiorite batholiths, which intruded metasedimentary rocks of the Great Island Group, may largely be the product of melting of Archean basement, based on field evidence and high initial 87Sr/86Sr ratios. The Caribou Lake porphyritic quartz monzonite gives an age of 1795 ± 35 Ma, with an initial 87Sr/86Sr ratio of 0.7084. High initial ratios seem to typify early Proterozoic granitic rocks in this remobilized craton.
Paleomagnetism and K–Ar isochron dates of Early Jurassic basaltic flows and dikes of Atlantic Canada
Authors: Hodych J. P. , Hayatsu A.
Published: April 2011

K–Ar isochron dates of 193 ± 2, 189 ± 3, and 191 ± 2 Ma are reported for the Shelburne dike of Nova Scotia, the Avalon dike of Newfoundland, and the Caraquet dike of New Brunswick, respectively. These major tholeiitic dikes agree in radiometric date with the North Mountain Basalt of Nova Scotia and with other tholeiitic flows of the Newark Supergroup that have been paleontologically assigned to the Hettangian. However, further work is needed to resolve the discrepancy between the Triassic–Jurassic boundary date of 193 ± 6 Ma suggested by the Newark Supergroup flows and the boundary dates of 204–213 Ma adopted in recent time scales.The North Mountain Basalt flows at nine sites on the north shore of the Bay of Fundy are shown to have likely magnetized during initial cooling, yielding an Hettangian virtual paleopole at 66°N, 72°E (dp = 9°, dm = 14°). New paleomagnetic results are also reported for the Caraquet and Avalon dikes.The virtual paleopoles from Hettangian flows and dikes of Atlantic Canada lie on average ~11 °north of the virtual paleopoles from Hettangian flows of the northeastern United States. This discrepancy is likely due to insufficient averaging out of paleosecular variation and demonstrates that caution is needed in paleomagnetically correlating among the Early Jurassic flows and intrusions of eastern North America.
Évènements tectoniques d'origine compressive dans le Protérozoïque du nord de la Cordillère canadienne (montagnes Ogilvie, Yukon)
Authors: Mercier Éric
Published: April 2011

The oldest Proterozoic strata of Coal Creek Dome (Ogilvie Mountains, Yukon) have been affected by syntectonic and decimetre- to kilometre-scale folds. These folds were eroded, then sealed by other Proterozoic strata. This is the first record of a Proterozoic compressive tectonic event in the northern Canadian Cordillera. It is named the Fifteenmile orogeny and may be correlated either with the Wernecke Mountains Racklan orogeny (usually dated at about 1200 Ma) or with an older event, perhaps Hudsonian (1750 Ma).
Application of section-balancing techniques to deep seismic reflection data from offshore eastern Canada: preliminary observations
Authors: Dentith M. C. , Hall J.
Published: April 2011

The application of section-balancing techniques to the analysis of deep seismic sections requires account be taken of isostasy and ductile-deformation processes. Structures imaged by deep seismic reflection profiling across the southern Grand Banks, offshore eastern Canada, are analyzed in this way. Correlations of dipping events in the deep crust, interpreted as shear zones, with faults recognized in the shallow part of the section are tested by attempting to restore the sections to their undeformed state by reversing the displacements on the faults. This process tests the geometric compatibility of the interpreted fault and the structures in its hanging wall. Our models suggest that the faults bounding the Whale and Horseshoe basins detach at the Mohorovičić discontinuity. In contrast, the fault bounding the Jeanne d'Arc Basin detaches within the lower crust.
Relative age of Otto stock and Matachewan dykes from paleomagnetism and implications for the Precambrian polar wander path
Authors: Buchan Kenneth L. , Neilson Douglas J. , Hale Christopher J.
Published: April 2011

North-trending diabase dykes within and near the Otto syenite stock of the Kirkland Lake area of the Superior Province carry a stable paleomagnetic remanence identical to that of 2454 ± 2 Ma Matachewan dykes far from the stock. A positive baked contact test for the remanence of a dyke within the stock demonstrates that the remanence is primary. Thus, (1) these dykes belong to the Matachewan swarm, (2) the Otto stock has not magnetically overprinted Matachewan dykes in its contact aureole as previously reported, and (3) the stock must be older than 2454 Ma.The magnetic remanence associated with the Otto stock, previously thought to be primary, must now be considered of uncertain age. Nevertheless, the positive baked contact test for the remanence of the Matachewan dyke within the stock demonstrates that the remanence associated with the stock predates intrusion of the Matachewan swarm.The conventional polar wander path for Precambrian North America decreases in age from the Matachewan paleopole to the Otto stock paleopole. Since this study demonstrates that the Otto stock pole is older than the Matachewan pole, there is a serious problem with the conventional path.
Evidence for the intra-Glenwood (Mackinaw) low-water phase of glacial Lake Chicago
Authors: Monaghan G. William , Hansel Ardith K.
Published: April 2011

A 14C age estimate of 13 470 ± 130 BP (ISGS-1378) from organic material at the base of transgressive lake deposits exposed in a southern Lake Michigan shore bluff near Riverside, Michigan, confirms that an intra-Glenwood low-water phase occurred in the Lake Michigan basin during the Mackinaw (Cary – Port Huron) Interstade. The altitude of organic material at Riverside suggests that the water plane was at or below modern lake level during the intra-Glenwood low-water phase. This observation indicates that drainage from the Lake Michigan basin was eastward, probably through the Straits of Mackinac into the Lake Huron basin. Such a drainage pattern implies that the correlative lake occupying the Lake Huron basin (Arkona low-water phase) must have had a level either congruent with or below that of the Lake Michigan basin. This lake system ultimately drained from the Lake Huron basin through a low eastern outlet (probably the Trent River lowland). The existence of low-level lakes at this time also indicates that the ice margin of the Lake Michigan lobe must have retreated at least as far north as the Straits of Mackinac region during the Mackinaw Interstade.
Upper Ordovician stratigraphy of Southampton Island, Northwest Territories
Authors: Dewing Keith , Copper Paul
Published: April 2011

The middle to late Caradoc Bad Cache Rapids Formation of Southampton Island consists of three "members": a locally present thin siliciclastic unit, overlain by a highly fossiliferous wackestone, capped by a mudstone, all deposited in a broad, shallow shelf setting. This formation is, possibly unconformably, overlain by the early Ashgill Boas River Formation, comprising a lower carbonate mudstone and an upper oil shale, deposited in a local, shallow subtidal, restricted basin during a transgression. Early to middle Ashgill strata of the Churchill River Formation are made up of a lower unit with coral-bearing wackestone, representing a return to normal marine conditions, and an upper unit of noncoralliferous wackestones, indicating a regional shallowing. The latter is capped by the Sixteen Mile Brook oil shale. The middle to late Ashgill Port Nelson Formation contains evaporite casts and algal laminites, suggesting a sabkha environment. Mound-like structures in this formation may have resulted from solution collapse brought about by the removal of evaporites after lithification.
Significance of a molluscan fauna to the physiographic history of the Calgary area, Alberta
Authors: Osborn Gerald , Thomas Richard , McCoy William , Miller Barry , Smith Alison
Published: April 2011

A newly discovered molluscan fauna provides an approximate age for a previously undated gravel sequence capping Nose Hill, a relict plateau adjacent to the Bow River in Calgary, Alberta, and constrains the age of the physiographic relief in the area. The fauna consists of a mixed terrestrial–aquatic assemblage whose composition indicates a paleoclimatic regime similar to that of the area today. The fossiliferous sediment, interpreted as a pond deposit, is a pebbly mud within a thick braid-plain gravel sequence. Isoleucine epimerization in the molluscs is not inconsistent with an Early Pleistocene or older age for the deposit. The Nose Hill gravels and an equivalent sequence capping another outlier (Broadcast Hill) located on the other side of the Bow River define an originally extensive paleo-plains surface. Fluvial dissection of the surface, including 175 m of incision by the Bow River and resultant separation of the two outliers, occurred within the last one to two million years.
Nd isotopic compositions of felsic igneous rocks in Cape Breton Island, Nova Scotia
Authors: Barr Sandra M. , Hegner Ernst
Published: April 2011

Nd isotopic data from 18 felsic plutonic and volcanic units in Cape Breton Island show variations consistent with other geological and geophysical evidence for at least three distinct terranes. A ca. 1.2 Ga syenite considered to be part of Grenvilleage basement exposed in the northwestern part of the island yields an initial εNd value of +0.4 and a depleted-mantle model age (TDM) of 1.66 Ga, suggesting substantial involvement of older (Archean or Early Proterozoic) crust in its petrogenesis. A TDM of 1.38 Ga indicated by Nd isotopic data for a Devonian granite spatially associated with the syenite is also consistent with the presence of older crust in that part of Cape Breton Island. In contrast, Silurian rhyolite and Devonian granites from the Aspy terrane have TDM ranging from 0.7 to 1.1 Ga and initial εNd between +2.8 and −1.2, and overlap in isotopic characteristics with late Precambrian and Early Ordovician plutons in the Bras d'Or terrane that yield TDM of 0.9–1.1 Ga and initial εNd of +1.4 to −1.8. The relatively small variation in εNd and TDM in these terranes suggests that old crust like that under the Blair River Complex may not be present. Granitic plutons and rhyolite in the Mira terrane of southeastern Cape Breton Island have a range in TDM (0.8–1.2 Ga) similar to that of the Aspy and Bras d'Or terranes, but initial εNd values ranging from +0.8 to +5.0 indicate more juvenile crust. This juvenile crust also appears to be present under southern New Brunswick and eastern Newfoundland and may be characteristic of the Avalon terrane.