bluuebunny/crossref_metadata_2025 huggingface dataset:
Rb–Sr Isotopic Age of the Kunavaram Series — A Group of Alkaline Rocks from India
Authors: Clark G. S. , Subbarao K. V.
Published: April 2011

A Rb–Sr isochron age of 1265 ± 85 m.y. has been obtained for a group of alkaline rocks (Kunavaram series) which intrude highly folded, metamorphosed igneous and sedimentary rocks of the Eastern Ghats belt of South India. The initial 87Sr/86Sr ratio is 0.7051 ± 0.0013. This age is believed to be the time of intrusion of these rocks. Assuming an initial ratio of 0.710, two mica samples from the nepheline syenite (a biotite and a muscovite) gave an age of 620 m.y. One sample of the country rock (garnet–biotite gneiss) gave an age of 2100 m.y., which agrees with prior estimates for the age of the principal orogenic activity in the Eastern Ghats belt.
Appalachian Structural Style in Southern New Brunswick
Authors: Brown Richard L.
Published: April 2011

The strain geometry of southern New Brunswick can be analyzed in terms of four major structural sub-divisions, which mark a variation in style from tilting and translation of rigid strata, single-phase cylindrical folding by flexural slip, polyphase folding by flexural flow, to extreme cataclastic flow with attendant transposition of early planar fabrics. Shallow dips of planar elements and shallow plunges of hinge lines occur in distinct zones, Maximum strain occurred along the northeast-trending Lubec-Belleisle zone, where vertical attitudes of planar and linear elements prevail. Cataclastic fabrics are regionally developed together with narrow mylonitic zones.Rock heterogeneity in part influences structural style, with early granitic plutons tending to act as rigid buttresses, but the major sub-divisions are not controlled by lithologic boundaries. The structural sub-divisions transgress the present position of fault boundaries.Southern New Brunswick is probably a relict continental margin. If regional folding, cataclasis, and later faulting can be attributed to the closing of the Proto-Atlantic seaway in Middle Devonian to Carboniferous times, the localization of intense strain in southern New Brunswick and particularly along the Lubec-Belleisle zone may be accounted for by assuming that stress concentrations would occur in the region of the shelf slope margin.
Two Assemblages of Marine Algae from Post-Glacial Deposits in the Eastern Canadian Arctic
Authors: Illman W. I. , McLachlan J. , Edelstein T.
Published: April 2011

The marine algae of the post-glacial deposits from the Ottawa Islands, Hudson Bay and Broughton Island off East Baffin Island were examined. A total of 15 non-calcareous species were identified, of which the most abundant at both sites were Sphacelaria plumosa and Desmarestia aculeata. The species assemblages are characteristic of present-day arctic and subarctic floras.
Regional Magnetic Anomalies and Geology in Fennoscandia: A discussion
Authors: Riddihough R. P.
Published: April 2011

A contoured magnetic anomaly map constructed from aeromagnetic profiles reflects the established tectonic patterns of the Fennoscandian region and permits speculations about such features as continental discontinuities colinear with oceanic fracture zones. An interpretation of the most outstanding magnetic anomaly of the region, in west-central Sweden, shows that its source is associated with a Precambrian anorogenic complex and has an unusually high magnetization. Magnetic similarities between the Baltic and Canadian shields are briefly discussed.
Geophysical Studies in Baffin Bay and some Tectonic Implications
Authors: Keen C. E. , Barrett D. L. , Manchester K. S. , Ross D. I.
Published: April 2011

A recent seismic refraction experiment in the deep central region of Baffin Bay showed that it is underlain by oceanic crust. This paper describes the results of gravity, magnetic, and seismic reflection profiling measurements in the bay. There is no definitive evidence for a buried ridge or for magnetic lineations in the center of the area. The magnetic and gravity anomaly fields have been used to define the boundary between the oceanic and continental crust around the bay and therefore the extent of oceanic crust presumed to have been formed by sea-floor spreading. Some of the characteristics of the seismic reflection lines across the continental margins, perhaps typical of this area, are also discussed. The results have been used to reconstruct the history of opening of Baffin Bay in conjuction with geophysical measurements in the Labrador Sea to the south and over the Alpha Ridge in the Arctic Ocean to the north. An attempt has been made to reconcile the geometry of opening with continental geology. Two phases of spreading are suggested. The first involves openings, in both the Labrador Sea and in Baffin Bay, about a pole in the Canadian Arctic Islands. The second, most recent stage of opening, requires that the Nares Strait was once a transform fault, perhaps connecting a Baffin Bay spreading center to the Alpha Ridge to the north.
Late Early Devonian Dacryoconarid Tentaculites, Northern Yukon Territory
Authors: Ludvigsen Rolf
Published: April 2011

The late Early Devonian succession in northern Yukon Territory contains a well-preserved dacryoconarid tentaculite fauna dominated by Turkestanella acuaria (Richter) in the upper part of the Road River Formation and T. acuaria and Nowakia parabarrandei Churkin and Carter in the overlying Michelle Formation. Based on the dacryoconarid tentaculite fauna the bulk of the Michelle Formation in the Ogilvie to Hart Rivers area is dated as late Pragian (early Emsian), and based on the graptolite and dacryoconarid tentaculite fauna the uppermost Road River Formation in the Blackstone River area is dated as Pragian (early Emsian or late Siegenian or both). The appearance of species of Nowakia in northern Yukon considerably earlier than in Bohemia is documented. It is concluded that some genera of the Dacryoconarida were influenced in their occurrence by environmental factors. New species described are Turkestanella minuta, Viriatellina michellensis, Guerichina lenini, Styliolina blackstonensis, and Metastyliolina conica.
The Mid-Atlantic Ridge near 45 °N, XVII: Al, As, Hg, and Mn in Ferruginous Sediments from the Median Valley
Authors: Cronan D. S.
Published: April 2011

Iron-rich sediments similar to those forming on other active mid-oceanic ridges have been found in the Median Valley of the Mid-Atlantic Ridge near 45 °N. The sediments are enriched in arsenic and mercury, and are thought to have formed largely as a result of submarine hydrothermal activity associated with the generation of new ocean floor at the ridge crest.
Rotated Power Spectra of Microseisms
Authors: Chandra N. N. , Cumming G. L.
Published: April 2011

Cross-power and coherency as a function of period and azimuth have been calculated for several seismic stations during the course of a microseismic storm in the north Pacific. These data indicate that in addition to the predicted Rayleigh waves, a large fraction of the observed ground motion must be due to other wave types, most of which have predominantly vertical motion. The data indicate that the angle subtended by the source of the waves increases with distance, suggesting that wave interactions at the coastline may be a major factor in the observed disturbances on the continent.
The Quaternary History of the Northern Cumberland Peninsula, Baffin Island, N.W.T. Part III: The Late Glacial Deposits of Sulung and Itidlirn Valleys and Adjacent Parts of the Maktak-Narpaing Trough
Authors: Dugdale R. E.
Published: April 2011

Four moraine systems are recognized within the area. The oldest was deposited at the margin of a major outlet glacier about 600 m a.s.1 Local corrie glaciers in the Sulung and Itidlirn Valleys show three and two moraine systems respectively, which in part have over-ridden the lateral moraine. Studies of the degree of boulder weathering and the rounding of pebble edges on the four units allows cross-correlation between Itidlirn and Sulung Valleys. Weathering ratios are used to tentatively date the moraines as follows: lateral moraine of the outlet valley glacier, 43 000± years old; Phase 1 corrie moraine in Sulung Valley 35 000± years old; Phase 2 corrie moraines 23 000± years old and the youngest corrie moraines (Phase 3) 12 500± years old, as determined from weathering studies in adjacent valleys.
The Quaternary History of Northern Cumberland Peninsula, Baffin Island, N.W.T. Part I: The Late- and Neoglacial Deposits of the Akudlermuit and Boas Glaciers
Authors: Carrara P. , Andrews J. T.
Published: April 2011

Moraines of local glaciers predating the Neoglacial occur in sections of northern Cumberland Peninsula. A study of these deposits is reported for the area between the heads of Quajon and Narpaing Fiords. A chronology is developed based on lichenometry, percent of lichen cover, and the weathering of boulders and pebbles. Initial dating is done by lichenometry and dates older than about 6000 BP are attempted by establishing rates of weathering. About 12 500 BP glaciers existed in both south- and north-facing corries with an equilibrium line at 850 m a.s.1. During the next 5000 years the south-facing glaciers retreated and disappeared. About 7000 BP, moraines were deposited in front of the Akuldermnit and Boas glaciers— these moraines are no longer ice-cored. The equilibrium line lay between 850 and 975 m a.s.1. A 'warm' interval followed and the ice cores melted. This was followed by an early Neoglacial advance, dated about 3800 BP for the period of moraine stabilization; after a 2000 year interval four younger readvances are recorded. All Neoglacial moraines are ice-cored. During the last few decades the equilibrium line has risen.
The Isocolid Trilobites Cyphoniscus Salter, 1853 and Effnaspis Gen. Nov. in the Appalachian Region of Canada and U.S.A.
Authors: Dean W. T.
Published: April 2011

Trilobites from the Appalachians of Virginia and Gaspé, Québec, that were attributed previously to the Swedish Ordovician genus Isbergia Warburg, 1925 are described and shown to belong to the Family Isocolidae. Isbergia virginica B. N. Cooper, 1953 is made the type species of a new genus Effnaspis. Cyphoniscus Salter, 1853, previously reported only from southern Ireland, northern England, and Kazakhstan, is described from eastern Gaspé.
Geology, Paleoecology, and Palynology of some Oligocene Rocks in the Rocky Mountain Trench of British Columbia
Authors: Hopkins Jr. W. S. , Rutter N. W. , Rouse G. E.
Published: April 2011

Mildly deformed sedimentary rocks of the Northern Rocky Mountain Trench were analyzed for their spore and pollen content. From these it was deduced that the rocks were of Early Oligocene (Chadronian) age. Two conclusions were reached: (1) at least mild deformation occurred in this portion of the Trench following the Early Oligocene and (2) Early Oligocene climate appears to have been essentially subtropical of a summer-wet, winter-dry type. These add further evidence to the theory that the Rocky Mountains were already of considerable elevation by Early Oligocene time.
The Mid-Atlantic Ridge Near 45 °N. XVIII. Heat Flow Measurements
Authors: Hyndman R. D. , Rankin D. S.
Published: April 2011

Eighteen heat flow measurements on the Mid-Atlantic Ridge, in the detailed study area between 45 and 46 °N, have a pattern of low values up to 20 km from the median valley, high heat flow 30 to 40 km away, low values again 50 to 100 km away, finally increasing to normal heat flow at great distances. The smoothed heat flow profile is everywhere lower than that predicted by theoretical cooling plate models.It is concluded that convective water flow in the fractured, porous crustal rocks of the ridge is responsible for the low heat flow near the crest. Higher values (at 30 to 40 km from the crest) occur when the sediment cover is sufficient to cut off communication between the crust and seawater. The low heat flow zone at 50 to 100 km from the crest can be explained by heat required to warm the convectively cooled crust when the rocks are sealed and circulation stops, and by the heat absorbed in lower crustal metamorphic reactions.
The Mid-Atlantic Ridge Near 45 °N. XIX. An Electron Microscope Investigation of the Magnetic Minerals in Basalt Samples
Authors: Evans M. E. , Wayman M. L.
Published: April 2011

Basalt samples from the vicinity of the Mid-Atlantic Ridge near 45 °N have been examined by electron microscopy, since many of the magnetic properties could be due to the fine structure of the titanomagnetites present. The observed remanence of axial material cannot be accounted for by multidomain or pseudo-single domain models. Furthermore, an explanation in terms of submicroscopic unmixing of titanomagnetite grains is shown to be untenable. However, electron microscopy did reveal the presence in all samples of a finely dispersed phase believed to be single-domain titanomagnetite grains. These will inevitably contribute to the remanence and may well be the dominant factor. The decay in remanence with distance from the ridge axis, which could similarly be associated with fine structure, is also discussed.
Geophysical and Geological Studies in Eastern and Northern Baffin Bay and Lancaster Sound
Authors: Keen M. J. , Johnson J. , Park I.
Published: April 2011

Baffin Bay is a small ocean basin. The northern continental slope of the bay has an anomalously gentle gradient because a greater quantity of sediment has been deposited on this margin, unlike those to east and west. The sedimentary rocks of the bay can be divided into two distinctive groups; deformed sediments are seen shoreward, associated with rise in (acoustic) basement, folding and faulting, and large magnetic anomalies. There is some evidence for deformed sediment underlying undeformed sediment in the central deep part of northern Baffin Bay, and some slight suggestion of a basement ridge in this area. Undeformed sediment overlies deformed sediment close to the margin off Lancaster Sound and Bylot Island. The volcanic province of western Greenland extends offshore and appears to be fault-bounded on its eastern margin. Precambrian gneisses lie to the east of this offshore volcanic province. The basalts are overlain by relatively young sediments to the west. There is a suggestion that the basalts are fault bounded to the west. We have not established continuity of Tertiary basalts between western Greenland and Baffin Island. There is no evidence for or against the existence of magnetic lineations in northern Baffin Bay.
Lower Carboniferous Algal Microflora, Southwestern Alberta
Authors: Petryk A. A. , Mamet B. L.
Published: April 2011

A diverse and relatively prolific Lower Carboniferous algal microflora has been encountered in the Rocky Mountains and Foothills of southwestern Alberta. The algae occur in the Banff, Livingstone, Pekisko, Shunda, Turner Valley, Mount Head, and lower Etherington Formations. They are generally conspicuous throughout the Banff Formation, scarce in the Livingstone Formation, but are rather abundant in the upper parts of the Pekisko and Shunda Formations, and in the Loomis, Opal, Marston, and Carnarvon Members of the Mount Head Formation.The most favorable facies for algae are mixed skeletal and oolitic-skeletal packstones—grain-stones representing shallow, open sea shoals. Lagoonal deposits also yield a very rich microflora. The most unfavorable facies are echinoderm-bryozoan packstones, and sandy, silty mudstones and wackestones found in relatively deeper, offshore lithofacies.Twenty genera and at least 22 species are recognized, of which 6 genera and 9 species are new taxa. The new forms are: Orthriosiphonoides salterensis, n. gen., n. sp., Intextulella agglomerata n. gen., n. sp., Pseudokamaena armstrongi n. gen., n. sp., P. boulderensis n. sp., Stacheoides ? spissa n. sp., S. tenuis n. sp., Epistacheoides nephroformis n. gen., n. sp., Pseudostacheoides loomisi n. gen., n. sp., and Asphaltina cordillerensis n. gen., n. sp.The present study indicates that the associated Foraminifera offer a better detailed zonation of the Lower Carboniferous than the algae, although the latter appear to be more sensitive to facies change and, therefore, may be more useful to reconstruct paleoenvironments. However, five local algal assemblages, based on the succession of genera, seem stratigraphically consistent in Alberta.
Sedimentology of Archean Turbidites at Yellowknife, Northwest Territories
Authors: Henderson John B.
Published: April 2011

The Burwash Formation is a major formation of the Archean Yellowknife Supergroup at Yellowknife. It consists of about 15 000 ft (4572 m) of interbedded graywackes and mudstones and shows many of the features characteristic of turbidites. Analysis of the internal sedimentary structures and paleocurrent data on the sediments indicate that the sediments were derived from the west, possibly from an area now occupied by an extensive granitic terrain, and accumulated in depositional fan valleys on a submarine fan complex near the margin of a large Archean sedimentary basin that lies to the east of Yellowknife. The high proportion of volcanic rock fragments, particularly silicic–volcanic lithic clasts, along with abundant quartz and feldspar and the minor but ubiquitous granitic rock fragments in the graywackes, indicates a mixed silicic–volcanic and granitic provenance. The modal and chemical composition, and volumetric abundance, of these sediments denotes the presence, and considerable extent, of sialic crust prior to the deposition of the Burwash Formation.
Magnetic Measurements Over Darnley Bay, N.W.T.
Authors: Riddihough R. P. , Haines G. V.
Published: April 2011

Five high level, 3-component, magnetic profiles outline a large magnetic anomaly approximately coincident with the previously observed, 130 mgal, positive gravity anomaly. Three-dimensional interpretations of the magnetic data establish the major dimensions of the source body but do not distinguish between a normal and inverted conical shape. Directions of magnetization derived from the interpretations suggest that the body is geologically related to the Precambrian Franklin Diabases.
New Radiocarbon Dates from the Yale Area of the Lower Fraser River Canyon, British Columbia
Authors: Mathewes R. W. , Borden C. E. , Rouse G. E.
Published: April 2011

Three new radiocarbon dates from two lakes near Yale, B.C. establish that ice-free conditions existed in parts of the Lower Fraser Canyon as early as 11 430 ± 150 B.P. A volcanic ash layer found in both lakes is considered to have come from the Mount Mazama eruption, based on a radiocarbon date from Squeah Lake. Mention is made of the problematic relationship of the three new dates to post-Vashon chronology in this area.
Geology of the Clachnacudainn Salient Near Albert Canyon, British Columbia
Authors: Gilman Richard A.
Published: April 2011

The nature of the Clachnacudainn Salient of the Shuswap Metamorphic Complex has been investigated in the vicinity of Albert Canyon, British Columbia. A concordant, folded sheet of granodiorite to quartz–diorite gneiss lying between two contrasting panels of metasedimentary rocks is exposed along the Illecillewaet Valley between Albert Canyon and Revelstoke. The lower panel, consisting predominantly of quartzo–feldspathic schist, is exposed in the Woolsey Creek Window in the core of the Lauretta Dome, and in an adjacent antiform at Clachnacudainn Creek. The upper panel, comprised in part of quartzo–feldspathic schist and migmatite, contains, in addition, thick beds of white marble and white or light gray quartzite. Marble and quartzite of the upper panel are correlated with the Badshot limestone and the Hamill quartzite found east of Albert Canyon in the Selkirk Mountains. Within the granodiorite gneiss, axes of broad open folds trend northwest–southeast as do the mineral lineations. Folding within the metasediments is complex and has not been resolved into a systematic pattern. Crosscutting bodies of diorite, granite, and pegmatite are abundant in many parts of the area, cutting both the granodiorite gneiss and the metasedimentary rocks.
Petrography of the Tombstone Stock, Nova Scotia
Authors: Wray E. M.
Published: April 2011

The Tombstone stock is the largest of several small Devonian granodiorite intrusions near Nictaux, Nova Scotia. Mapping and petrological studies indicate that the present exposure of the stock is close to the original roof of the intrusion. The distance of the present exposure to the original roof is estimated to be greatest at the western end of the stock. Three small stocks to the east and the extreme eastern end of the Tombstone stock consist of a finer grained, more biotite rich granodiorite. This rock is believed to represent a roof facies of the Tombstone granodiorite. It is proposed that a much larger intrusion underlies these relatively small granodiorite stocks.
The Camsell River–Conjuror Bay Area, Great Bear Lake, N.W.T.
Authors: Badham J. P. N.
Published: April 2011

Roof pendants of a late Aphebian (~1800 m.y.) volcano–sedimentary complex, within Hudsonian granites, outcrop on the eastern shore of Great Bear Lake. The volcano–sedimentary complex is similar to, and may be correlated with, the Echo Bay Group which outcrops farther to the north.The volcanic rocks are interbedded with immature volcanoclastic sedimentary rocks and with thinner units of calcargillite and dolomite. A unit of conglomerate, tuff, and siltstone, previously correlated with the Cameron Bay Group, is assigned to the 'Balachey Unit', until its relationships with other groups in the area are more clearly understood.Hudsonian granitic stocks and batholiths (~ 1750 m.y.) intruded the complex. Sharp contacts and narrow aureoles characterize these as high level intrusions. Zones of sulfide replacement are common in the aureoles. Porphyry dikes and stocks of similar age to the granites and rare, pegmatitic magnetite–apatite–actinolite bodies, also intrude the volcano–sedimentary complex.Three sets of diabase intrusions are identified, and related to three distinct fault directions. Giant quartz veins and mineralization of the U–Ag–Ni, Co arsenide – Bi type are found in zones of northeast-striking dextral faults.The volcano–sedimentary complex is interpreted as the molasse phase of the rising orogen of the Coronation Geosyncline, and is related to earlier deposits (the Snare and Epworth Groups) closer to the craton in the eastern part of the geosyncline.
Potassium–Argon Ages of Igneous Rocks from the Area near Hedley, Southern British Columbia
Authors: Roddick J. C. , Farrar E. , Procyshyn E. L.
Published: April 2011

K–Ar ages are reported for 19 samples collected from the Hedley, Okanagan, and Similkameen Complexes located in the vicinity of Hedley, British Columbia. Although the zoned nature of amphiboles collected from the Hedley Complex makes interpretation of their radiometric ages difficult, it is suggested that the Hedley Complex was intruded at least 165 m.y. ago and was a part of the same magmatic activity that gave rise to both the Okanagan and Similkameen batholithic complexes. These latter complexes yield ages ranging from 141 m.y. to 184 m.y.
The Precambrian Gneisses and Supracrestal Rocks of the Western Shore of Kaipokok Bay, Labrador, Newfoundland
Authors: Sutton J. S.
Published: April 2011

In the Kaipokok Bay area the amphibolite facies Hopedale Complex is overlain by the English River Greenstones. The Hopedale Complex is formed of gneisses, amphibolites, and associated granites and shows indications of being polycyclic, possibly derived from an older (Aphebian?) granulite facies terrane. The English River Greenstones are a supracrustal sequence of dominantly metavolcanic rocks and are the equivalents of the Aillik series. Hudsonian orogenic effects were superimposed on both rock units and caused locally intense refoliation of the gneisses and the development of a strong foliation in the greenstones. During this orogenic cycle an early period of intense zonal flattening was followed by a more regionally developed folding and weak tectonite fabric development. All of these rocks were cut by later acidic and basic intrusions. The geological history of the area shows a general similarity to that of southwestern Greenland.
Evidence for "Caribooan Orogeny" in the Southern Okanagan Region of British Columbia
Authors: Ross John V. , Barnes William C.
Published: April 2011

A sequence of non-metamorphosed, little deformed, fossiliferous, sedimentary rocks, near Keremeos, southern British Columbia, unconformably overlies rocks having a history similar to that of the Vaseaux Formation, the most westerly exposed part of the Shuswap Complex of the southern Okanagan Valley. Fossils from the younger sequence have a late Mississippian – early Pennsylvanian age.This part of the southern Okanagan region has a deformational history that is pre-mid-Carboniferous and likely related to the Caribooan orogeny. This is in contrast to Late Paleozoic rocks at northern Okanagan localities and elsewhere in British Columbia that have under-gone strong deformation of probably Mesozoic age.
Age of Molybdenum and Tungsten Mineralization in Northern British Columbia
Authors: Christopher P. A. , White W. H. , Harakal J. E.
Published: April 2011

A K–Ar mean age of 49.8 ± 0.7 m.y. was determined for four biotite concentrates from granite porphyry on the Mt. Haskin Mo and Mt. Reed Mo–W properties east of Cassiar, British Columbia.Biotite K–Ar ages of 71.7 ± 2.6 m.y. and 68.3 ± 2.7 m.y. obtained from a young phase of the Cassiar intrusions, occurring along the eastern margin of the Cassiar Batholith, place an upper limit on the age of the molybdenum mineralization on the Cassiar Molybdenum property. A 62.0 ± 2.2 m.y. age, determined for a biotite concentrate from the coarse alaskite phase of the Mt. Leonard Boss, dates the molybdenum mineralization on the Adanac property.These ages suggest that the early Tertiary metallogenic epoch, documented in central British Columbia and southeastern Alaska, can be extended through northern British Columbia.
Seismic Refraction Measurements in Southeast Alaska and Western British Columbia
Authors: Johnson S. H. , Couch R. W. , Gemperle M. , Banks E. R.
Published: April 2011

Crustal thickness determinations were made from seismic refraction measurements along two profiles extending north–northwest along the Inside Passage of Southeast Alaska and western British Columbia. The source for the seismic waves was a series of 10 explosions detonated by personnel of the Earth Physics Branch, Department of Energy, Mines and Resources of Canada. Arrivals recorded in Southeast Alaska from explosions in Bird Lake on Graham Island indicate a 26 km thick crust over a mantle with a Pn velocity of 7.9 km/s. Measurements of Pn wave attenuation suggest that the uppermost mantle has a Q value of 650 ± 120. Arrivals recorded along the mainland coast of British Columbia from explosions in Ripley Bay indicate a 30 km thick crust over a mantle with a Pn velocity of 8.1 km/s. On the basis of compiled gravity and seismic refraction data, the crust of the Inside Passage region from Queen Charlotte Sound to Cross Sound is believed to be anomalously thin. Crustal thickening from ocean to continent appears to occur in a stepwise, rather than continuous, fashion in the vicinity of the Inside Passage.
Origin of a Diopside–Tremolite Assemblage near Tweed, Ontario
Authors: Cermignani C. , Anderson G. M.
Published: April 2011

An occurrence of silicated dolomitic marble is described in which diopside zones are separated from the host dolomite by symmetrical zones of tremolite and calcite with interstitial quartz. Zoned tremolite–calcite veinlets are also found in the dolomite. The origin is ascribed to the introduction of water under open-system conditions after the formation of diopside.
Volcanic History and Tectonics of the North Langjökull Region, Central Iceland
Authors: Piper J. D. A.
Published: April 2011

The geology of the area around the northern part of the Langjökull ice sheet in central Iceland is outlined. This area includes the termination of the western neovolcanic zone, two silicic centers, and basaltic interglacial, intraglacial, and postglacial volcanoes. The lava succession becomes older to the northwest of the area where the zone of young volcanoes gives away to a pile of lavas of pre-Bruhnes epoch age which dip at low angles towards the active zone.This active zone undergoes a change in strike from NE–SW to north–south near latitude 64 °55′N and the volcanoes north of this are smaller in volume than those on the southern extension of the zone. The area of Bruhnes epoch activity dies out above latitude 65 °10′N but much of the area between here and the north coast of Iceland was a line of volcanic activity during the preceding Matuyama epoch.The northern part of the western active zone in Iceland became inactive in late Pleistocene times, and the southern part of the zone is an area of continuing crustal growth. The zone of active volcanism does not terminate against a transform fault and crustal growth is accommodated by deformation of the crustal plate. Lines of crustal growth which subsequently die out can be invoked to explain the anticline and syncline structures in the lava pile and the currently-active Snaefellsnes zone in western Iceland.
Late Precambrian Volcanic Rocks of Avalon, Newfoundland – a Spilite/Keratophyre Province: Recognition and Implications
Authors: Hughes Charles J.
Published: April 2011

On the basis of their mineralogy and chemistry, the late Precambrian volcanic rocks of Avalon, southeast Newfoundland, are shown to be spilite and keratophyre. A metasomatism, operative at least on the scale of analyzed samples, accompanied this metamorphism. The effects of this metasomatism cannot be ignored in assessing analytical data for purposes of igneous petrogenesis. This and other difficulties arising from penological investigation of spilite/keratophyre terrain are discussed.
Proposal of a Code for the Nomenclature of Trace-Fossils
Authors: Sarjeant William A. S. , Kennedy W. James
Published: April 2011

In order to legalize binomial trace-fossil names, a draft code (independent of the existing international codes of botanical and zoological nomenclature) is presented, for possible consideration at a future international meeting. It is essentially morphographic and allows the inclusion under a single name of similar traces made by taxonomically different animals, as well as the retention of different names for dissimilar products of the activity of the same animal. At the same time it allows any classification or order (alphabetic, taxonomic, ethologic, preservational, etc.) to be used, according to the particular purposes for which such groupings are advantageous.
New Geophysical Data on the Continental Shelf of Central and Northern West Greenland
Authors: Ross D. I. , Henderson G.
Published: April 2011

Recent geophysical work on the continental shelf of central and northern West Greenland has enabled the known onshore geology of the West Greenland Basin to be extended into the offshore region and the major graben running the length of the continental shelf in Melville Bugt to be defined in some detail. Two zones are observed within the offshore extension of the West Greenland Tertiary basalts. The eastern zone corresponds to dipping basalts at shallow depth similar to those occurring onshore on Hareøen, outermost Nûgssuaq, Ubekendt Ejland, and southwestern Svartenhuk. The more westerly zone corresponds to sub-horizontal to horizontal basalts whose top occurs at a depth of up to 1 km, the depth increasing towards the west and south. In the upper part of this offshore sequence the basalts are believed to be interlayered with Tertiary sediments. The Melville Bugt graben is shown to be a major continuous feature parallel to the coast of northwestern Greenland with sediment thicknesses of 7–10 km. The graben is believed to have been formed at the time of initial rifting of Canada and Greenland.
Nature and Origin of Salic Pyrociastic Rocks at Kakagi Lake, Northwestern Ontario
Authors: Smith D. R. , McNutt R. H. , Clifford P. M.
Published: April 2011

At Kakagi Lake, a sequence of basaltic rocks is overlain by about 2000 m of pyroclastic rocks. These rocks lack mesoscopic layering, and are very poorly sorted. Most fragments are accessory in nature. Analysis of variation of maximum fragment size, matrix percent, and sorting imply vent areas to the west and south of the Kakagi Lake area.The rocks are calc-alkaline rather than tholeiitic in lineage, poor in K2O, particularly the most silicic. Fragments are more salic and depleted in FeO and MgO relative to their matrix.Thickness and lack of layering, coupled with poor sorting, suggest several ash flows. Chemical differences between accessory fragments and matrix suggest differentiation of magma between eruptions, such that the upper portion of the magma chamber became more salic than the lower portion; hence the products of each eruption vary in composition.
Petrology of Metavolcanic Rocks in the Bishop Corners – Donaldson Area, Grenville Province, Ontario
Authors: Sethuraman K. , Moore Jr. John M.
Published: April 2011

A calc-alkalic suite, with an apparent thickness of 7 km, varies from alkali basalt and tholeiite composition in the lowest part exposed, through andesite flows and pyroclastic rocks, to rhyodacite pyroclastics at the top. Sixty-two chemical analyses demonstrate a single volcanic cycle. Volcanism was succeeded by carbonate sedimentation and intrusion of granodiorite plutons. After deposition of clastic rocks, the entire succession was deformed and metamorphosed in the amphibolite facies.Isograds divide the metavolcanic rocks into five mineral zones: chlorite, biotite, blue-green hornblende, green hornblende, and diopside. Equivalent zones in the pelites are: chloritoid–staurolite, kyanite–staurolite, and sillimanite–muscovite.Fe in epidote, Ca in plagioclase, K and Na in hornblende, and ferric/ferrous ratio in rocks, biotite, and hornblende all increase in mafic and intermediate rocks, with increasing metamorphic grade. In biotite and hornblende, octahedral Al decreases with grade, whereas other chemical variables are related to bulk composition. Mineral assemblages and hornblende compositions indicate metamorphic conditions between Abukuma and classical Barrovian facies series.
Gravity Anomalies, Crustal Structure, and Plate Tectonics in the Canadian Cordillera
Authors: Stacey R. A.
Published: April 2011

Bouguer values are presented for a strip across the southern part of the Canadian Cordillera (49 °N to 51 °N and from 112 °W to 132 °W). The Bouguer anomalies outline density variations in the surface rocks, but where there are regional changes in the topography, these anomalies are distorted by the relationship between Bouguer values and elevation. A Bouguer anomaly profile at 50 °N has been interpreted in terms of Woollard's average crustal model which assumes Airy-type compensation for the topography. Residual anomalies are related to lateral density variations in first the crust and then the upper mantle. Comparison between these models and other geophysical data suggests there is a decrease in the density of the crust and of the upper mantle west of the Rocky Mountains; the transition is related to the western edge of the Precambrian basement. The large residual anomalies in the vicinity of Vancouver Island are attributed to either very dense crustal material or low density mantle material. It is concluded that the anomalous density distribution below Vancouver Island is due to the presence of a remnant plate of oceanic lithosphere below the island which extends eastwards below the central part of the Cordillera. The suggested northern limit of this plate is 51 °N and arguments are presented for the plate being a relic of late Cenozoic convergence between the Juan de Fuca and American plates.
Pleistocene Mammals from Gold Run Creek, Yukon Territory
Authors: Harington C. R. , Clulow F. V.
Published: April 2011

Remains of thirteen species of mammals are reported from Pleistocene deposits at Gold Run Creek near Dawson, Yukon Territory. Eight of the thirteen species are extinct and two are no longer living in the Yukon. The most common elements of the fauna are Equus (Asinus) lambei (Yukon wild ass), and Bison crassicornis (large-horned bison). Taxidea (badger) and Bison alaskensis (Alaskan bison) are reported for the first time from the Yukon Pleistocene. A kiang-like horse is also reported from deposits at Gold Run Creek.These mammals may have inhabited a cool grassland or open parkland during late Wisconsin time. Bison crassicornis and mammoth bone from deposits at Gold Run Creek have yielded radiocarbon dates of 22 200 ± 1400 yr B.P. and 32 250 ± 1750 yr B.P. respectively. Bison alaskensis is evidently older than the remainder of the fauna as bone from the specimen yielded a radiocarbon date of over 39 900 yr B.P.
Comparison of the Composition of Porphyroblastic and Fabric-forming Biotite in Two Metamorphic Rocks
Authors: Kamineni D. C. , Carrara A.
Published: April 2011

Porphyroblastic and fabric-forming biotite crystals in two metamorphic rocks (samples examined) show significant differences in Fe, Mg, Al, and Ti content. These differences can be explained in terms of a depletion model.
Fission-track Dating of Late Tertiary and Quaternary Volcanic Glass from the Mount Edziza Volcano, British Columbia
Authors: Aumento F. , Souther J. G.
Published: April 2011

Seventeen specimens of Pliocene to Recent volcanic glass from Mount Edziza, British Columbia, were dated by the fission-track method. Results agree well with paleomagnetic, potassium–argon, carbon-14, and stratigraphic data, offering accurate dates with closer limits of confidence than can be obtained by other methods.The age data supports the petrological evidence for three principal stages of activity, each beginning with eruption of basalt and culminating with eruption of more acid magma.
Radiometric Ages of Granitic Rocks, Southwestern Nova Scotia
Authors: Cormier R. F. , Smith T. E.
Published: April 2011

Granitic rocks comprising the eastern half of the main batholith of southwestern Nova Scotia have been studied. The granitic rocks intrude Lower Paleozoic metasediments of the Meguma Group. Field work, the chemistry and petrology of the granitic rocks, and Rb–Sr whole-rock isochron dates indicate that there were at least two episodes of granite emplacement, the earlier about 415 m.y. ago and the later about 350 m.y. ago. Samples from a much smaller pluton some 65 mi (104 km) away from the study area were also dated and are correlated with rocks in the main batholith.
Schistosity and Penetrative Mineral Lineation as Indicators of Paleostrain Directions
Authors: Schwerdtner W. M.
Published: April 2011

Field evidence indicates that the progressive deformation of most schistose rocks consists of two principal phases: (1) the anisotropy-creating phase, during which schistosity and mineral lineation develop and (2) the anisotropic phase, during which numerous translational-slip surfaces are generated parallel to schistosity. This discontinuous deformation may be regarded as simple shear on a scale that is much larger than the average spacing of neighboring slip surfaces.Schistosity and mineral lineation can be produced normal to the direction of greatest finite shortening and parallel to the direction of greatest finite extension, respectively. Subsequent simple shearing tends to change this relationship such that both structural features become oblique to the principal directions of finite strain, although the mineral lineation remains parallel to the major axis of the finite-strain ellipse on the schistosity plane. Thus the lineation rather than the schistosity may be a reliable indicator of a (non-principal) direction of total strain, for a given period of progressive deformation.
Composition of Garnet in Anorthosite–Charnockite Suites: Bias and Precision in Electron-Probe Microanalysis
Authors: Schrijver K.
Published: April 2011

The composition of garnet in each of 11 specimens from anorthosite–charnockite suites (Marcy Massif, Morin Complex, Lac-Croche Complex) has been determined by electron-probe microanalyzer. All analyses include Si, Al, Fe, Mn, Mg, and Ca. The range of FeO (total iron as Fe2+) is from 26.5 to 34 wt.%; MnO from 0.5 to 2, MgO from 0.5 to 5, and CaO from 7 to 9.5 wt.%. TiO2 is present in very small amounts at most ([Formula: see text]?). The major end member molecule in all specimens is almandine.Bias and precision of the analysis have been estimated: (1) by replicate determination of the composition of a garnet standard in each analytical run on each of the unknown species and (2) by duplicate determination of the garnet species in each rock specimen.In general, inclusion of a known species, similar in composition and physical state to the unknown species, in each analytical run on an unknown will provide estimates of bias applicable to individual analyses as well as an overall estimate of bias applicable to the mode and circumstances of the particular series of runs on the electron-probe microanalyzer. The reliability of the estimates of bias so obtained depends mainly on the compositional homogeneity of both known and unknown species.
A Primitive Clupeomorph Fish from the Middle Cenomanian of Hakel, Lebanon
Authors: Forey Peter L.
Published: April 2011

A primitive clupeomorph fish Ornategulum gen. nov. sardinioides (Pictet) is described from the middle Cenomanian of Hakel in the Lebanon. The caudal skeleton shows a free first hypural, a fusion between the second hypural and the reduced first ural centrum, and a complete neural spine associated with the second preural centrum. The cranial anatomy shows this genus to be the most primitive clupeomorph yet known, lacking a temporal foramen, a well-defined pre-epiotic fossa, frontal fontanelles, a pterotic bulla, and a recessus lateralis. The fish is too primitive to be placed in either suborder of the Clupeomorpha and there is no firm evidence to suggest that it belongs to a separate clupeomorph lineage; the genus is placed as Clupeomorpha incertae sedis.
Relations Stratigraphiques entre le Groupe de Pontiac et le Sillon Métavolcanique de Baby au Témiscamingue, Québec
Authors: Imreh L.
Published: April 2011

The pre-Kenoran Archean stratigraphy has always been of prime interest to geologists working in the Superior Province. However, one must realize that the problems raised have remained, for the most part, without satisfactory solution. Thus, the respective age relation of the thick lithostratigraphic metavolcanic and metasedimentary units (Pontiac), forming respectively the Baby Rift and its northern flank to the northeast of Ville-Marie in Temiscaming, has not been defined with certainty to date.During a geological mapping project on a scale of 1:12 000, covering the township of Baby and adjacent parts of the townships of Guérin and Guigues, it has become possible for us to remove the uncertainty and to define the age relation of the two units mentioned. We can now state that the metasedimentary unit (Pontiac) forms the stratigraphic base of the metavolcanic unit.To arrive at this conclusion it was first necessary to determine the size of the main folded structures in the region of Rapide des Quinze, then to uncover and let weather the outcrops over several kilometers, in order to define the actual contact of the two units. [Translated by the Journal]
Quantitative Unspiked Argon Runs in K-Ar Dating
Authors: Baksi A. K.
Published: April 2011

The radiogenic 40Ar contents of three whole-rocks less than 1.5 m.y. old have been determined using 38Ar as the tracer and also from unspiked runs. The agreement in results between the two methods is excellent.
An Interpretation of Vertical Crustal Movement Observations in the Area of Lac St. Jean, Quebec
Authors: Nyland E.
Published: April 2011

The observed vertical movements of the ground near Lac St. Jean, Quebec imply, if real, a fairly deep-seated driving mechanism and a localized area of low shear strength in the near surface layers. An analysis of the observation by means of body force equivalent theory also rules out the existence of localized fault slip and suggests a degree of structural control.This work is an application of an interpretation technique developed for the study of permanent changes near earthquakes. The limited conclusions are a consequence of the limited data available.
Paleomagnetism of the Precambrian Martin Formation, Saskatchewan
Authors: Evans M. E. , Bingham D. K.
Published: April 2011

Oriented samples of the Martin Formation were collected from 23 sites, both sediments and igneous rocks being represented. Detailed laboratory treatment yields an overall mean direction corresponding to a paleomagnetic pole at 9 °S, 72 °W (dp = 6.3°, dm = 11.5°). Strong evidence for the primary nature of the magnetization involved is provided by a positive fold test. The paleomagnetic pole obtained provides further evidence for a major eastward loop in the polar wandering path for North America during late Aphebian – early Helikian times. The exact age of Martin Formation deposition is the subject of debate, but extreme limits given by various authors are 1930 to 1490 m.y. However, the paleomagnetic results themselves somewhat restrict this range, and are of use in setting up a regional chronology, since they enable stratigraphic correlations between isolated sedimentary basins of the Canadian Shield to be made.
Analysis of Heat-Flow Data—Several Boreholes in a Sedimentary Basin
Authors: Judge A. S. , Beck A. E.
Published: April 2011

For the Western Ontario and Michigan basins, which overlie the Grenville and Central geological provinces, temperature gradients in more than 30 boreholes and thermal conductivities of several hundred specimens from several formations have been determined. It is found that characteristic gradients and conductivities can be assigned to certain formations and to geological periods. There may also be a real variation (< 20%) of heat flow between some formations, which is qualitatively correlated with variations in heat producing elements.With the exception of one value of 1.3 μcal cm−2 s−1, which involved extrapolation of data to a great distance, all 'whole borehole' heat-flow values, uncorrected for glaciation effects, lie between 1.0 ± 0.2 μcal cm−2 s−1; a correction for the Wisconsin stage of the Pleistocene glaciation would increase these values by 0.3 ± 0.1 μcal cm−2 s−1.
Evidence of a Surge on Barnes Ice Cap, Baffin Island
Authors: Holdsworth G.
Published: April 2011

It is shown that a previous hypothesis for a surge on Barnes Ice Cap is strongly supported by several independent sources of evidence.
Wisconsin Glacial Chronology and Relative Sea-level Movements, Narpaing Fiord Broughton Island Area, Eastern Baffin Island, N.W.T.
Authors: Pheasant D. R. , Andrews J. T.
Published: April 2011

Three distinct glacier advances and four major periods of adjustment of relative land and sea levels are recognized in the Wisconsin age stratigraphic and geomorphologic record of the Northern Cumber-land Peninsula. The coast, which is presently undergoing submergence, is close to an isostatic equilibrium position following rapid land emergence during post-Cockburn time (ca. 8000–1000 BP). Laurentide ice advances during two earlier stades—the Alikdjuak ca. 115 000 BP and the Napiat > 40 000 BP—were more extensive than the Cockburn glacier advances and a positive relationship between ice load and amount of crustal deflection at the ice margin is demonstrated. Computations based on synchronous raised marine features and known extent of the ice load indicate a crustal flexural parameter (α) of > 80 km and perhaps > 135 km for this area. The date of the Alikdjuak stade suggests the time transgressive nature of the early-Wisconsin maximum position of the continental ice sheet margin and supports the hypothesis that continental glaciation may well have originated in the climatically sensitive uplands of the eastern Canadian arctic/sub-arctic.