bluuebunny/crossref_metadata_2025 huggingface dataset:
Paleomagnetism and its Relationship to Till Deposition
Authors: Gravenor C. P. , Stupavsky M. , Symons D. T. A.
Published: April 2011

Field observations and theoretical studies on temperate glaciers suggest that there is a layer of water at the ice–sediment interface. If this condition existed under continental glaciers it is reasonable to assume that rock and mineral particles were released from the base of the ice through a water or slurry medium.In order to test this hypothesis, samples of clay till from Port Alma, Ontario, were tested and shown to have a strong component of detrital remanent magnetization (DRM) which resists alternating field demagnetization. The possibility that the remanence alignment was caused by glacier movement has been ruled out by anisotropy of magnetic susceptibility measurements. Thus the results demonstrate that a water or slurry layer existed at the base of continental glaciers at the time of till deposition. The basal water layer may explain the very rapid advance of the glacier lobes through the basins of the Great Lakes. The paleomagnetic data and available radiocarbon dates suggest that the till at Port Alma was deposited in a relatively short period of about 100 to 400 yr. The potential usefulness of DRM in clay-rich tills for stratigraphic studies is being further investigated.
Petrology of Alkaline Rocks from Cuttingsville and the Shelburne Peninsula; Vermont
Authors: Laurent R. , Pierson T. C.
Published: April 2011

The Cuttingsville composite stock has feldspathoid-bearing and quartz–bearing alkaline rocks emplaced in Precambrian schists of the Green Mountains. The main intrusions are, from oldest to youngest: (1) hastingsite foyaite and biotite foyaite, (2) diorite, (3) essexite, porphyritic essexite, plagifoyaite, and sodalite foyaite, (4) alkaline quartz syenite, (5) dikes of tephritic phonolite porphyry, phonolite porphyry, and microplagifoyaite. The K–Ar ages of 100 m.y. on the hastingsite foyaite and of 96.4 m.y. on the essexite indicate that this intrusion is perhaps the youngest manifestation of magmatic activity in New England.In the Shelburne peninsula, the alkaline rocks are intrusive into the Paleozoic sedimentary sequences of the Champlain Valley; they crop out on opposite sides of Lake Champlain. Intrusions consist of small stocks of alkaline syenite grading from a coarse-grained core to a fine-grained quartzose margin, which is cut by dikes of alkaline granite aplite, and of sills of trachyte porphyry. The alkaline rocks of the Shelburne peninsula are analogous to the alkaline syenites of unit 4 in Cuttingsville.We conclude that the rocks described did not originate through differentiation of an alkaline olivine basalt magma. Instead, partial and progressive melting of gabbroic phases in the uppermost mantle is proposed to account for the chemical relationships suggesting a source within the mantle. The absence of large amounts of mafic rocks, the order of emplacement which does not correlate with fractionation trends, and the presence of two syenitic melts of contrasted composition are evidences to support the proposal. Partial melting could have been caused by passage of the lithosphere over thermal "plumes" in the lower mantle.
The Paleomagnetism of Seal and Croteau Rocks from the Grenville Front, Labrador: Polar Wandering and Tectonic Implications
Authors: Roy J. L. , Fahrig W. F.
Published: April 2011

Some of the red beds of the Seal Group contain at least two CRM (chemical remanent magnetization) components. The dominant one has a direction of 275°, +05 °(pole position 205 °E, 05 °N). The less pronounced component has a direction which is about 55 °clockwise from this. It is suggested that the dominant (westerly) component is the younger one and was developed after the block containing these rocks was rotated clockwise.The igneous rocks of the Seal and Croteau Groups are reversely magnetized relative to the red beds and yield a pole (152 °E, 05 °N) about 50° away from that indicated by the major component of the red beds. The magnetization of the igneous rocks is thought to contain a primary TRM (thermoremanent magnetization) but the igneous pole is 65 °of arc away from poles derived from rocks of similar age in the Superior Province. If, however, a correction of 55 °rotation (as suggested by the red-bed results) is applied to the block, the igneous pole then lies in the southern hemisphere (197 °E, 22 °S) close to poles for rocks of similar age from the Superior Orogen. It is then suggested that the primary magnetization of the igneous rocks was acquired before rotation. Because of its pole position, it appears that the dominant CRM (post-rotation) was acquired less than 400 m.y. after the initial magnetization of the igneous rocks. This places an upper limit to the interval of time during which the rotation occurred. It is suggested that the rotation is perhaps related to early Grenvillian orogenic and thermal events (1200–1500 m.y.).Paleomagnetic evidence when coupled with geological evidence suggests that not only was the N.E. Grenville Orogen rotated, but that in the interval 1550–1200 m.y. ago, the paleopole relative to this part of the crust (and to the Superior) underwent an excursion, referred to as the "Grenville Loop", deep into the Southern hemisphere.
Upper Cretaceous Marine Strata on Somerset Island, N.W.T.
Authors: Dixon James , Hopkins Jr. William S. , Dixon Owen A.
Published: April 2011

Upper Cretaceous marine shale and limestone beds are present in a faulted outlier in the vicinity of Creswell Bay, Somerset Island. The contained microflora indicates a Senonian age and the strata are correlated to the Kanguk Formation of the Arctic islands.
A Note on the Most Recent Ichthyosaur Known: an Isolated Coracoid from the Upper Campanian of Saskatchewan (Reptilia, Ichthyosauria)
Authors: McGowan C.
Published: April 2011

The geologically youngest ichthyosaur specimen is described: an isolated, partial coracoid from the Bearpaw Formation of the South Saskatchewan river valley (Upper Campanian) near Stewart Valley, Saskatchewan. The final extinction of the Ichthyosauria is briefly discussed, and the possibility that it may not have been brought about by competition from the mosasaurs is examined.
Age and Correlation of the Kobau Group, Mount Kobau, British Columbia
Authors: Okulitch Andrew V.
Published: April 2011

The Kobau Group, found in south-central British Columbia, consists of highly deformed, low-grade metamorphic rocks derived from a succession of sedimentary and basic volcanic rocks of pre-Cretaceous, likely post-Devonian age. Deformation began in Carboniferous times and recurred with decreasing intensity up to the Tertiary Period. Possible correlative successions are found surrounding Mount Kobau. These include possibly late Paleozoic formations west and northwest of Mount Kobau, the Carboniferous to Permian Anarchist Group found south of the 49th parallel and east of the Okanagan Valley, the pre-Upper Triassic, possibly Mississippian Chapperon Group west of Vernon, and parts of the Shuswap Metamorphic Complex east of the Okanagan Valley. Prior to deposition of the Kobau Group, part of the Shuswap Complex was subjected to deformation, presumably in mid-Paleozoic time.
Rb-Sr Isotopic Age for the Precambrian Lavas of the Seton Formation, East Arm of Great Slave Lake, Northwest Territories
Authors: Baadsgaard H. , Morton R. D. , Olade M. A. D.
Published: April 2011

Spilitic basalts from the Proterozoic Seton Formation at the type locality of Seton Island in the East Arm of Great Slave Lake, Northwest Territories, have a Rb–Sr isotopic age of 1872 ± 10 m.y. The age, representing either the time of eruption or a subsequent metasomatic (spilitization) event, provides a minimum age for the Great Slave Supergroup of the district. An initial 87Sr/86Sr ratio of 0.7018 ± 0.0005 for the lavas is, together with their age, in accordance with previously proposed theories on continental separation and mantle derived magmatism during Aphebian times.
Oil, Climate, and Tectonics
Authors: Irving E. , North F. K. , Couillard R.
Published: April 2011

We identify four sets of factors governing oil occurrence—climate (especially temperature), mineral nutrients, tectonic factors controlling initial basin formation, and tectonic factors controlling preservation of the oil. We argue that all factors are themselves subject to the framework imposed by plate tectonics. If we are to consider all Phanerozoic oil deposits, the only factor capable of quantitative comparison for all the periods is the first one, in that it is partly a function of latitude.A paleolatitude analysis has been made for both reservoir rocks and preferred source rocks for all petroliferous basins, with results weighted according to total reserves. No statistically satisfactory relationship was found between oil and paleolatitude that would embrace all Phanerozoic deposits. Most Paleozoic oil was formed in rocks deposited in low latitudes, but this may be an accident of preservation. The much larger Mesozoic deposits were similarly related to low paleolatitudes, but this result is heavily biased by the huge reserves of the Persian Gulf. If these are excluded, Mesozoic oil occurs with equal probability in high and in low paleolatitudes. Cenozoic oil is uniformly distributed with respect to paleolatitude.The distribution of oil with time reveals that 71% of all known oil was probably formed in the late Mesozoic, most of it (60%) in the mid-Cretaceous. The first requirement in any general theory of oil occurrence, therefore, is to understand why so much oil was formed near the present Persian Gulf, and to a lesser extent in Middle America, during such a short interval of geological time. We attempt to show that all four controlling factors were optimized in these two places for this brief time-span. In the timetable of plate tectonics, two large marine embayments opened astride the equator in the late Mesozoic, and these may or may not have been connected through the western Mediterranean. One embayment contained the Persian Gulf, and the other, Middle America. The renewal of mantle convection at about −100 m.y. activated these embayments, abruptly increased the rate of sea-floor spreading, and enlarged the oceanic ridges, causing maximum development of warm, shallow seas and releasing, through igneous activity, greatly increased quantities of mineral nutrients.The geometry of subsequent plate activity was such that the Persian Gulf was tectonically protected by the rapid northward movement of the Indian plate (which absorbed most of the impact with the Eurasian plate), and the Gulf of Mexico was protected by the northeastward movement of the Antillean arc.
Paleomagnetism of the Mealy Mountain Anorthosite Suite and of the Shabogamo Gabbro, Labrador, Canada
Authors: Fahrig W. F. , Christie K. W. , Schwarz E. J.
Published: April 2011

Two stable, ancient, N.R.M. components were isolated by a.f. demagnetization of samples from 29 sites in the Helikian (Middle Proterozoic) anorthosite and adamellite suites of the Mealy Mountains. The directions of the two components are chiefly to the northwest, 20° upward (northwest component) and to the east, 65 °downward (east component). The northwest direction is thought to be the primary igneous T.R.M. and no reversely magnetized sites with this direction were encountered in the Mealy suite. The 11 sites from which the northwesterly component was isolated yielded a mean pole at 179 °W, 8 °N, α95 = 12°. This is some distance away from poles derived from rocks of comparable age from elsewhere in the Canadian Shield and may reflect a 50° clockwise rotation of this section of the Grenville Orogen relative to the Superior after the initial magnetization of the Mealy rocks. Evidence of a second stable component was found in 14 sites (east component); 11 of these are reversely magnetized and three are normally magnetized. The 14 sites with easterly (and reversed easterly) magnetization yielded a combined pole for this component at 182 °W, 38 °S, α95 = 9°. This pole position suggests that the east component was acquired after the rotation of this part of the Grenville Orogen. The cores from 3 sites exhibited two clear end-points during a.f. demagnetization and thus contain both the northwest and the east component.The Helikian Shabogamo Gabbro at the south end of the Labrador Trough was sampled at 13 sites on a line extending 80 km north from the Grenville Front. After a.f. cleaning these sites yielded a pole at 171 °W, 10 °N, α95 = 12°. This pole lies about 20° northwest of poles for rocks of similar age in the Superior Orogen so it is suggested that the rocks of the sample area, though lying a bit north of the line generally accepted as the 'Grenville Front', have been rotated clockwise (about 20°) since intrusion of the gabbro.
Seasonal Variations in the Isotope Ratios of Carbon in Maple Leaves and Other Plants
Authors: Lowdon J. A. , Dyck W.
Published: April 2011

A seasonal cycle in δ13C, varying between −22‰ in early spring and −28‰ in late fall, has been observed in maple leaves growing under natural conditions. A similar δ13C cycle, varying between −25‰ and −30‰ is indicated for grass growing in the same location as the maple leaves. The seasonal cycle appears to be analogous to the diurnal δ13C cycle.14C/12C ratios of various plants from different parts of Canada show that the 14C produced by thermonuclear bombs has approximately a half-life of eleven years in the atmosphere over Canada. When due allowance is made for the isotope fractionation effect produced by plants, no significant variations in the 14C content in plants from different localities across Canada can be detected. The reported 14C peak observed in atmospheric CO2 in late summer also shows up in maple leaves but with reduced intensity. 14C levels show clearly that the first leaves in spring are composed primarily of carbon assimilated in the previous fall.
The Sheeted Dike Layer of the Betts Cove Ophiolite Complex does not Represent Spreading
Authors: Brock P. W. G.
Published: April 2011

Dikes of the sheeted dike layer are conspicuously chilled against the underlying mafic and layered ultramafic rocks, indicating that the older rocks were relatively cool when the dikes were intruded. Cool mafic rocks could spread only by brittle fracture and infilling by dike material. Near-surface, cool ultramafic rocks could spread by brittle fracture or, possibly, by plastic deformation. The absence of significant infilling, and the preservation of cumulate textures in the extensive layering indicate that spreading did not take place.
The Origin of the Norwegian Channel—A Discussion based on Seismic Measurements
Authors: Sellevoll Markvard A. , Sundvor Eirik
Published: April 2011

A seismic reflection and refraction survey has been carried out in the Norwegian Channel between 59.5 °N and 63 °N. The measurements and recent data from other parts of the channel show that the Norwegian Channel is mainly a result of sedimentation and glacial erosion during the Quaternary.The seismic refraction measurements indicate that the Tertiary sediments on the west coast of Norway extend closer to the coast than previously suggested.
Results of Ethylene Glycol Swelling Test on Argillaceous Limestone
Authors: Dolar-Mantuani Ludmila , Laakso Ray
Published: April 2011

Rocks which contain significant amounts of swelling-type clay minerals disintegrate when they are exposed to drying and wetting or to freezing and thawing. The ethylene glycol immersion test is used as a standard test to simulate the breakdown of rocks, containing harmful amounts of expanding clay minerals, when they are used as construction materials in wet and freezing conditions.The glycol test was assessed for petrographic evaluation of argillaceous carbonate rocks intended for use in the construction industry. This was done by conducting the test on 61 small cylinders of a Paleozoic–Verulam argillaceous limestone which contained minor amounts of an expanding clay mineral interstratified with illite and subordinate chlorite. The development and propagation of cracks located in clay concentrations, as seen under a microscope, were used as assessment criteria. Cracks developed very slowly, therefore the test is considered unsuitable for industrial acceptance testing and for petrographic assessment of argillaceous carbonate rocks when quick test results are needed.
The Magnetization Process of Certain Red Beds: Vector Analysis of Chemical and Thermal Results
Authors: Roy J. L. , Park J. K.
Published: April 2011

A vector analysis of chemical leaching and thermal demagnetization results of 179 specimens of the Hopewell Group shows that three magnetizations were acquired in a nearly parallel direction but at different times as indicated by polarity. Field evidence indicates that magnetization occurred within 35 m.y. of deposition. It is suggested that these red beds were magnetized in three stages during a magnetization process which began at the time of deposition; hence producing one detrital (DRM) and two chemical (CRMA and CRMB) remanent magnetizations in that order. The two CRMs can be successively removed chemically to uncover the DRM. The CRMB is demagnetized by thermal treatment at 600–674 °C, but, the DRM and the CRMA cannot be separated thermally. This accounts for apparently aberrant directions obtained after thermal demagnetization at 674 °C, because the resultant vector of the remaining (and sometimes oppositely directed) DRM and CRMA is not directed along the direction of the magnetizing field. However, by vector analysis of the combined chemical and thermal results, the directions of the three magnetizations can be determined and an accurate field direction (174°, + 15°; α95: 3°; pole: 36 °N, 123 °E) is thus obtained. More of the information contained in the rocks can also be retrieved from the within-specimen magnetization observed by cutting specimens at some stage during chemical or thermal treatment. For example, the results indicate the following about field reversals: Several of them occurred at the Pennsylvanian–Mississippian boundary; the intensity of the field may remain constant at the beginning of a reversal; reversals may be rapid, and, in some instances, of short duration, leading to the suggestion that, at reversal time, the field may be subjected to an oscillatory motion before stabilizing in the same or opposite polarity.
Revised Stratigraphy of the Hunting Formation (Proterozoic), Somerset Island, Northwest Territories
Authors: Dixon James
Published: April 2011

In a revision of the stratigraphy of the Hunting Formation three members are recognised in the vicinity of the lower reaches of the Hunting River, northwestern Somerset Island. Member 1 rests conformably upon the Proterozoic Aston Formation and consists of sandstone, sandy dolostone, and dolostone; member 2 consists of alternating dolostone and cherty dolostone; and member 3 contains a variely of dolostone types. Depositional environments ranged from supratidal to shallow subtidal and much of the deposition may have been on a tidal flat complex.An unconformity is present at the top of the Hunting Formation and is equated to the regional unconformity at the base of the Paleozoic succession. The strata overlying the Hunting Formation have been correlated with Middle Cambrian rocks on the Boothia Peninsula, south of Somerset Island. A K–Ar date of 702 ± 25 m.y. for a diabase intrusion stratigraphically close to the contact between the Aston and Hunting Formations favors a Proterozoic age for the Hunting Formation.
The Geochemistry of the Granitic Rocks of Halifax County, Nova Scotia
Authors: Smith T. E.
Published: April 2011

Studies of part of a large batholith in southwest Nova Scotia show that granitic rocks of two different ages penetrate the Lower Palaeozoic metasediments of the Meguma Group. They are distinguished by their field relationships, mineralogy, and petrology from an older series, varying from biotite granodiorite through quartz monzonite to muscovite biotite granite, which is penetrated by younger large dikes, up to 1.5 km wide, of alaskite. Rb–Sr whole rock isochron ages show that the older series was emplaced approximately 415 m.y. ago and that the younger alaskite dikes were emplaced about 350 m.y. ago. Major and trace element chemistry shows that the older series of granitic rocks were formed by differentiation of a calc-alkali magma in situ. The younger dikes are all highly silicic, show limited major element variation, and have been affected by hydrothermal metasomatism.
The Chestnut Pollen Decline as a Time Horizon in Lake Sediments in Eastern North America
Authors: Anderson T. W.
Published: April 2011

Chestnut [Castanea dentata (Marsh.) Borkh.] was a dominant tree of the upland forests of eastern North America until its elimination by the blight fungus, Endothia parasitica Anders. The blight originated in New York City in 1904, and within 50 years, it spread throughout the entire range of Castanea dentata. The chestnut destruction is documented in lake sediments by a corresponding decline of chestnut pollen as illustrated in examples from Lakes Ontario and Erie, and Woodcliff Lake, New Jersey. According to the data from Woodcliff Lake, the decline can be assigned an age equivalent to the time of the chestnut die-out for the area. Thus, dates of 1930 A.D. and 1935 A.D. are taken to represent times of the chestnut pollen decline in Lakes Ontario and Erie, respectively. The Castanea pollen decline provides an excellent and very recent time horizon (above the Ambrosia pollen boundary) for determining sedimentation trends since the time of European settlement as well as recent sedimentation rates.
Aphebian Halite and Sulphate Indications in the Belcher Group, Northwest Territories
Authors: Bell R. T. , Jackson G. D.
Published: April 2011

Cubic casts interpreted as indications of halite crystals and slit-like gashes interpreted as molds of sulphate crystals have been found in the Belcher Group.
The Origin of Chemical Variations in Groundwaters from a Small Watershed in Southwestern Ontario
Authors: Schwartz Franklin W.
Published: April 2011

A very striking and unique feature of the groundwater system within the Upper Kettle Creek watershed is the marked concentration decrease of nearly all ionic species in the direction of flow. The conceptual model proposed here attributes this decrease to selective ion filtration by the Port Stanley till. Ionic constituents generated in the shallow groundwater zone by dissolution of the porous medium either pass through the till or accumulate depending upon their relative mobilities. Other important processes that influence the composition of the groundwaters are cation exchange within the Port Stanley till, CO2 gas generation within the soil zones of recharge areas, and the upward leakage of H2S gas from deeper in the Paleozoic section.
Deep Drill 1972. Potassium–Argon Dating of the Bermuda Drill Core
Authors: Reynolds P. H. , Aumento F.
Published: April 2011

The numerous lamprophyric sheet units which make up a substantial portion of the Bermuda Seamount appear to have been intruded about 33 m.y. ago. The pre-existing pile of tholeiitic submarine lavas may be substantially older, possibly as old as the surrounding sea floor (that is, they were formed as early as 110 m.y. ago).
A Late Jurassic Mafic Pluton in Newfoundland
Authors: Helwig J. , Aronson J. , Day D. S.
Published: April 2011

A small alkaline ultramafic intrusion in central Newfoundland is dated as 135 ± 8 m.y. old and 139 ± 9 m.y. old by the K–Ar method on biotite. This is the first known Mesozoic pluton (aside from dikes) in Newfoundland. The occurrence, composition and age of the pluton and associated igneous rocks is similiar to, and perhaps related in origin to, igneous rocks found in the Monteregian Hills of Quebec and other areas in eastern North America.
Ice-Wedge Cracks, Garry Island, Northwest Territories
Authors: Mackay J. Ross
Published: April 2011

Observations made on winter ice-wedge cracks at Garry Island, N.W.T., for the 1967–73 period show that cracking tends to occur between mid-January and mid-March. On the average, nearly 40% of the ice wedges crack in any given year. The crack frequency varies inversely with snow depth. Medium sized ice wedges, about 1 m wide, crack more often than smaller or larger wedges, ice wedges crack preferentially near the center and often year after year at nearly the same place. The cracks average about 1 cm wide at the surface and taper downwards to depths which may exceed 5 m. The cracks partially close in spring before a new ice veinlet forms in them. Evidence provided by multiple wedges suggests that cracking may be initiated at times within the wedge rather than at the ground surface, and thus the cracks propagate both upwards and downwards.
Graptolites with Multiple Genicular Spines from the Upper Ordovician of Western North America
Authors: Riva John
Published: April 2011

A careful restudy has been made of the types of Climacograptus innotatus var. pacificus Ruedemann from the topmost Ordovician of western North America and of topotype material of Climacograptus innotatus Nicholson from the Lower Silurian of Scotland. The study shows that these two forms are morphologically unrelated, the former being represented by short, stubby individuals with complex spinose growths, including double genicular spines, and the latter by slender, lanceolate individuals apparently provided with genicular flanges. Var. pacificus is here recognized as a distinct species, Climacograptus pacificus, and typifies and is restricted to Late Ordovician graptolite faunas of western North America and the Pacific Faunal Province.A deformed individual from Idaho characterized by three or four genicular spines is distinguished as Climacograptus pacificus pilosus, subspec. nov.
Iron Compounds in Lake Sediments
Authors: Coey J. M. D. , Schindler D. W. , Weber F.
Published: April 2011

Dried surface sediment from various Canadian lakes was characterized by X-ray diffraction and Mössbauer spectroscopy. At most two quadrupole doublets were found at room temperature, one ferrous, the other largely ferric. Their intensity ratio is related to the crystallinity of the sediments. It is also correlated with oxygen content, and inversely correlated with ferrous iron content of the overlying water. The major iron phase in the sediments is X-ray amorphous ferric hydroxide. Chlorite is the major ferrous mineral.
Teleseismic Response of a Multi-layered Dipping Media using Asymptotic Ray Theory
Authors: Kanasewich E. R. , Hron F. , Alpaslan T.
Published: April 2011

A plane wave solution in a multi-layered dipping medium with arbitrary dips is not available in practical form, but we show that algorithms based on a partial ray expansion using asymptotic ray theory presents no difficulties. The selection of multiple and converted phases is done automatically by the computer to minimize the error in the partial ray expansion below any desired level. For modest dips, the peak positions in the ratio of the vertical to the horizontal crustal transfer functions do not shift significantly. However, the relative peak amplitudes are modified considerably. Therefore, it seems feasible to use the ratio of transfer functions to obtain a suitable layered model, and dip determinations may be carried out as a secondary stage of iteration to improve the agreement between field experiment and model theoretical computations. As an example we obtain a crustal model, 35 km thick, near the Edmonton observatory with a steeply dipping sill, 2 km thick, at a depth of about 19 km and most likely made up of high-velocity material.
A Mid-Mesozoic Breccia from the Coast of Labrador
Authors: King A. F. , McMillan N. J.
Published: April 2011

A unique occurrence of Mesozoic breccia cut by lamprophyric-carbonatite dikelets, near Makkovik, Labrador is interpreted to relate to the opening of the Labrador Sea. The breccia has been dated by nannofossils; vitrinite reflectance studies show that some time during or after deposition the rock was heated to at least 170 °C. It is suggested that shallow seas extended westward beyond the present Labrador Marginal Trough during early Jurassic time and that the period of late alkaline igneous activity is related to the rifting between Greenland and Labrador that commenced about the middle of the Mesozoic Era.
Silurian Graptolites from Eastern Gaspé, Quebec
Authors: Lenz Alfred
Published: April 2011

Eight species of graptolites not recognized in a previous study (Lenz 1972) are described from the Gaspé region. These comprise Monograptus bouceki, of Late Pridolian age from the Roncel-les Formation; M. cf. M. galaensis and M. communis rostratus of mid-Llandoverian age from the Burnt Jam Brook and White Head Formations respectively; Pristiograptus auctus of latest Wenlockian or earliest Ludlovian age, and P. tumescens and Saetograptus chimaera semispinosus of early Ludlovian age, from the St. Léon Formation; P. dubius dubius of Wenlockian or early Ludlovian age from the Laforce and St. Léon Formations; and P. ludensis of latest Wenlockian age from the Gascons Formation.To date thirty species of graptolites have been recognized from the stratigraphic units studied.The low diversity of the Wenlockian-Ludlovian faunas is considered indicative of a shallow water community setting. It is tentatively suggested that the latest Wenlockian P. ludensis zones fauna might be the shallow water equivalent of the deep water M. testis zone.
Whole-Rock Rb/Sr Ages of Metamorphic Rocks from Northern Ellesmere Island, Canadian Arctic Archipelago. I. The Gneiss Terrain between Ayles Fiord and Yelverton Inlet
Authors: Sinha A. K. , Frisch Thomas
Published: April 2011

The first Precambrian ages from the Northern Ellesmere Fold Belt are reported. Six rocks from the largest gneiss terrain in northern Ellesmere Island yield a Late Precambrian age (minimum 742 ± 12 m.y.) of regional metamorphism. Relatively high initial 87Sr/86Sr suggests that the rocks were derived from crustal materials.
Lower and Early Middle Cambrian Formations near Mount Robson, British Columbia and Alberta
Authors: Fritz W. H. , Mountjoy E. W.
Published: April 2011

Five formations and part of a sixth were examined in order to resolve conflicting reports as to their age and lateral relationship. The formations are redescribed at their type sections and equivalent strata are described at a control section. It is concluded that the Lower Cambrian Mural, Mahto, and Hota Formations and the Middle Cambrian Chetang Formation are valid and that the Tah (= Mural) and Adolphus (= Hota) Formations should be suppressed. The boundary between the Nevadella and Bonnia-Olenellus Zone falls within the middle unit of the Mural. The Lower – Middle Cambrian boundary is located at or very near the contact between the Hota and overlying Chetang Formation. This is a sharp lithologic contract, but no physical evidence of an unconformity was noted.
Man-Induced Thermokarst, Sachs Harbour Airstrip, Banks Island, Northwest Territories
Authors: French H. M.
Published: April 2011

The disturbed terrain adjacent to the airstrip at Sachs Harbour is an example of man-induced thermokarst processes operating within the High Arctic environment. An irregular topography of mounds and linear depressions has appeared and evidence indicates preferential subsidence along ice wedges. The underlying sands and gravels are ice-rich with approximately 20–35% excess ice and natural water (ice) contents of between 50 and 150%. Examination of air photographs indicates that the terrain developed within three years of the initial disturbances. Detailed levelling in 1972 and 1973 suggests that subsidence and permafrost degradation is still active, over 10 years later. Gullying of the airstrip is a problem partly associated with the thermokarst activity. A comparison is made with man-induced thermokarst terrain in Siberia.
The Reorientation of the Kangâmiut Dike Swarm, West Greenland
Authors: Escher A. , Escher J. C. , Watterson J.
Published: April 2011

The Nagssugtoqidian belt in West Greenland is formed mainly of Archaean rocks which were strongly reworked during the early Proterozoic. Investigation of the southern boundary region has resulted in a model for the tectonic reworking based on the geometry of homogeneous simple shear deformation. Two differently oriented swarms of mainly pre-kinematic dikes are used as strain indicators at the deformation boundary. Gneiss tectonite fabrics have been used to determine that the shear plane dips northwest at 20–40° and that the shear direction along this plane is towards the southeast. The average amount of simple shear strain (S = 6) has been determined from the degree of dike reorientation. This mechanism has resulted in a ductile overthrusting of the reworked rocks over the Archaean foreland, giving a crustal shortening of ca. 66%. The area investigated represents a deep tectonic level. At higher levels ductile deformation would be expected to give way to thrust and fold nappe development. The displacements demonstrated are those which might be expected in the deformed margins of colliding continental plates.
Occurrences and Origin of the Ophiolites of Southern Quebec, Northern Appalachians
Authors: Laurent Roger
Published: April 2011

The ophiolites of southern Quebec are thrust sheets. Prior to their folding with the country-rock. they were emplaced as solid masses into the thick metasedimentary and metavolcanic geosynclinal prism of Notre Dame Trough, in Early Ordovician time. The occurrence of the ophiolites is controlled by their structural and stratigraphic position. Complete ophiolites occur as stratified sheets lying structurally above the Cambrian Caldwell Group, and they are overlain by a mélange assumed to be of Early Ordovician age. Dismembered ophiolites consist of peridotite sheets and lenses which may have been attached originally to the basal peridotite of the larger stratified sheets; they are tectonically intruded into Cambrian rocks.The stratified sheets have a simple, regularly-layered structure with no well developed sheeted-dike complex. Other feature s include a thin upper unit of gabbroic and basaltic rocks with a relatively thick ultramafic cumulate at the base and a thicker lower unit of Alpine peridotite. There is apparently no transition zone between the upper and lower units. All these features suggest that the ophiolites of southern Quebec represent possible fragments of an oceanic crust formed on a rapidly spreading ridge. It is assumed that they have been emplaced on the Early Ordovician continental margin by obduction and contemporaneously with the development of a subduction zone, which may have caused the magmatism that generated the adamellitic granites intruded into the ophiolitic complexes, and the calcalkatline volcanic rocks of the Lower to Middle Ordovician Ascot and Weedon Groups.
The Properties and Origin of an Apparently Deeply Weathered Soil Profile near Gould Lake, Ontario
Authors: Rutherford G. K. , Churchward M. H.
Published: April 2011

An apparently deeply weathered soil profile on well foliated amphibolite is described from the Gould Lake area, Ontario, although such residual soils developed on country rock have not been previously recorded. The evidence from a variety of analyses indicates that this deep soil profile, typical of a very limited area, has been developed on a saprolite-like, probably hydrothermally altered, rock material. Similar crumbly rock material preserving rock structures has been reported from several areas in the Canadian Shield.
Uranium–Xenon Dating by Thermal Neutron Irradiation
Authors: Gopalan K. , Rao M. N.
Published: April 2011

A new approach to the dating of uranium minerals using the spontaneous fission of uranium is proposed. The method involves thermal neutron irradiation of samples followed by mass spectrometric analysis of the xenon fractions released from them during stepwise heating. The potential advantages of the technique are the following: no separate explicit measurement of uranium is required, the error in age measurement due to inhomogeneous uranium distribution in samples is eliminated, and any diffusive loss of spontaneous fission xenon from less retentive sites is allowed for.
Sédimentation sur la Ride de Terre-Neuve
Authors: Pastouret L. , Auffret G. A. , Hoffert M. , Melguen M. , Needham H. D. , Latouche C.
Published: April 2011

The stratification, in part more or less rhythmic, of a fifteen metre long core of predominantly hemi-pelagic sediment from the northern slope of the Southeast Newfoundland Ridge reflects changing distribution patterns of different water masses during the late Quaternary. In particular, the lithological and microfaunal characteristics of the sediments indicate that, in the area of the core, the cold Labrador Current from the north and the continental slope water have had a permanent influence on the sedimentation pattern, whereas the paths of the Gulf Stream water have shifted intermittently. The influence of the Gulf Stream is clearly identifiable during the Holocene and during the last interglacial (faunal zone X). Ice-rafted debris and relatively coarse turbidite-type beds are more prominent in sequences deposited under a glacial régime, notably in those that accumulated near the end of the late Pleistocene and the beginning of the Holocene. The upper limit of faunal zone X (Sangamon-Würm) is placed close to 1000 cm depth in the core on the basis of the disappearance at this level of Globorotalia tumida flexuosa (Koch). The resulting estimate of the subsequent mean sediment accumulation rate is of the order of 10 cm/1000 y.
Global Distribution and Character of Permian Biomes Based on Brachiopod Assemblages
Authors: Waterhouse J. B. , Bonham-Carter G. F.
Published: April 2011

We present data on the occurrences of Permian brachiopod families comprising the genera of 54 families, plus corals and fusulinids, at 343 stations. Geographic coordinates, age range, sampling index, lithology where possible, and data sources are given for each station. Q-mode cluster analysis based on presence or absence of brachiopod families reveals three distinct groups of localities, separable by a modified type of linear discriminant function. Discriminant scores for each group, calculated for every station, give sensitive measures of diversity that partially overcome deficiencies due to incomplete collecting. Localities with group A characteristics are found to have low diversity. They occur mainly in Australia – New Zealand and Siberia, are conspicuously devoid of fusulinids and corals, and are often in near association with glacial deposits. Group C localities are characterized by having high diversity, are usually associated with fusulinids and corals, but never with glacial deposits, and occur mainly in a sinuous belt roughly parallel to modern 30°N latitude. Group B localities are intermediate in diversity, sometimes associated with corals and fusulinids, and occur particularly in northern North America, parts of Russia, and much of South America. Group C is interpreted as indicative of a tropical biome, Group B of a temperate biome, and Group A as a subpolar to polar biome. Detailed regional analysis is made, age by age. A crude overall geographic distribution, independent of age, is made by taking average discriminant scores for each 10 degree block of latitude and longitude, to partially overcome uneven distribution of stations. Maps showing the resulting global distribution of biomes (and inferred paleoclimate and paleolatitude) indicate that the Dietz–Holden Permian reconstruction, based on bathymetry and paleomagnetics, provides a more logical continental framework than the present distribution of continents. Due to high-diversity faunas, and steep diversity gradients across the Baikal geosuture, we propose that the Chinese segment lay further south than in the Dietz–Holden model. Previous work on Permian brachiopod diversity gradients, which showed that the present continental configuration fitted the data better than Permian reconstructions, was based on too few data, lack of age control, and a faulty procedure to correct for incomplete sampling. Preliminary comparison of paleomagnetic data with brachiopod-paleoclimate data indicates general agreement, although this needs further study.
A Late Cretaceous Microfossil Assemblage from the Buffalo Head Hills, North-Central Alberta
Authors: Wall John H. , Singh Chaitanya
Published: April 2011

A small outcrop belonging to an unnamed shale unit in the Buffalo Head Hills of north-central Alberta has yielded marine microfossils of Senonian, most probably Campanian, age.The foraminiferal fauna, including Haplophragmoides fraseri, Verneuilinoides bearpawensis, Praebulimina carseyae and Cassidella tegulata, suggests equivalence with that of the upper Campanian Bearpaw fauna of southern Alberta.The radiolarian assemblage includes Spongurus (Spongurantha) sp., Spongodiscus (Spongodisus) sp. cf. S. (S.) renillaeformis, Spongostaurus sp., Spongotripus (Spongotripus) sp. cf. S. (S.) morenoensis and Dictyomitra (Dictyomitra) multicostata, which are present in the Bearpaw Formation of southern Alberta, and in an interval of the Schrader Bluff Formation of northern Alaska, considered middle Senonian in age.Among the dinoflagellates recorded from the outcrop, three species of Dinogymnium – D. acuminatum, D. longicornis and D. sibiricum, and four species of Deflandrea – D. granulifera, D. minor, D. spectabilis and D. victoriensis are restricted to strata of Senonian age (inclusive of Maestrichtian Stage). Of this group, Dinogymnium longicornis, Deflandrea granulifera and D. spectabilis are present in the Bearpaw Formation of southern Alberta. The dinoflagellate assemblage has four species in common with that of the Senonian or younger beds in western Siberia.The pollen assemblage is dominated by species of Aquilapollenites – A. dolium, A. trialatus and A. turbidus – strongly indicative of a Campanian age. A megaspore, Balmeisporites rarus, suggests a Senonian age.The microfossil assemblage provides corroborative evidence in support of J. A. Jeletzky's hypothesis that a marine connection existed between the Arctic and Western Interior regions through northern Alberta during the Santonian and Campanian.
K/Ar Age of Lower–Upper Cretaceous Boundary at Orphan Knoll (Labrador Sea)
Authors: Hinte J. E. Van , Adams J. A. S. , Perry D.
Published: April 2011

The Albian–Cenomanian of Orphan Knoll yielded unrecrystallized, unheated, autochthonous glauconite. K/Ar ages for the Lower Cenomanian samples are 100, 91, and 105 Ma (average 99), and the K/Ar age for one Upper Albian (Vraconian) sample is 96 Ma. The non-sequential results do not allow for great confidence in a precise boundary age. However, the data can be read to support the widely used assumption of −100 Ma as the age for the Albian-Cenomanian = Early-Late Cretaceous boundary.
Timing and Development of the Orthotectonic Zone in the Appalachian Orogen of Northwest Newfoundland
Authors: Bursnall John T. , Wit Maarten J. de
Published: April 2011

Examination of part of the Fleur de Lys Supergroup, within the orthotectonic zone of north-west Newfoundland, reveals that regional deformation and metamorphism may not have commenced prior to the Early Ordovician and was not completed until the Devonian. The onset of deformation could have been as young as Llanvirnian.Fleur de Lys metasediments are correlated to the west with moderately deformed and undeformed rocks of the western platform. To the east, they are shown to be in part the lateral age equivalent of ophiolitic rocks. The ophiolites may be fragments of an older foundation to the mafic volcanic and volcanoclastic Baie Verte Group.Polyphase-deformed and regionally metamorphosed terrains (orthotectonic zones) such as the Fleur de Lys, do not form 'instantaneously', but evidently result from a critical sequential and progressive development history, covering a recognizable time span, and probably display characteristics of paratectonic zones at an intermediate stage. Sequential or simultaneous opening and closing of marginal basins is suggested as a mechanism, not only to explain the formation of such zones, but also the regional timing variation that apparently exists within the Appalachian-Caledonian orogen. Such processes are known to have occurred consistently since the Early Tertiary, and can presently be observed along the Western Pacific margin.
Devonian Plutonism in South-Central British Columbia
Authors: Okulitch Andrew V. , Wanless R. K. , Loveridge W. D.
Published: April 2011

An apparently tabular body of granitoid gneiss, 3 to 5 km wide and more than 70 km long, that lies along the western margin of the Shuswap Metamorphic Complex between Shuswap and Admas Lakes, shows intrusive relationships with Palaeozoic and older rocks and has yielded zircons whose minimum age is 372 Ma. This intrusion, together with other granitoid plutons in the area that appear to be related to it, provide evidence of widespread plutonism during Middle Devonian time near the western edge of the Paleozoic Cordillera geosyncline and necessitate significant revisions in the interpretation of the crustal history of this region.
Archean Glomeroporphyritic Basalts
Authors: Green Nathan L.
Published: April 2011

Feldsparphyric basalts commonly occur as a distinctive 'marker horizon' 300 to 500 m below the felsic volcanic units of many Archean greenstone belts. Within the Knee Lake greenstone belt, northern Manitoba, glomeroporphyritic basalts, characterized by large irregularly-shaped aggregates of plagioclase phenocrysts, occupy this stratigraphic position within the two lower-most volcanic cycles. A major chemical and/or tectonic break does not occur within the volcanic cycles, but rather, the chemical affinities of the Knee Lake volcanic rocks changes gradually (at a silica content of approximately 55%) from tholeiitic to calc-alkaline with increasing stratigraphic height. The accumulation of plagioclase phenocrysts suggests extensive crystal fractionation of the Knee Lake magmas. The gradual transition in affinity of the Knee Lake lavas from tholeiitic to calc-alkaline can be explained by near-surface fractionation under constant fO2 conditions.
Granulite Facies Metamorphism in the Coast Range Crystalline Belt
Authors: Hollister Lincoln S.
Published: April 2011

Mineral assemblages diagnostic of the granulite facies of metamorphism occur between Terrace and Prince Rupert, British Columbia. The estimated pressure (5–8 kb) and temperature (750–850 °C) of metamorphism are important constraints in unravelling the geologic history of the Coast Range batholithic complex.
Archaeocyathids and the Lower Cambrian Continental Shelf of the Canadian Cordillera
Authors: Stelck C. R. , Hedinger A. S.
Published: April 2011

The geographic occurrences of archaeocyathids are plotted for the Cordilleran region of western Canada. The archaeocyathids are found both east and west of, and within the Rocky Mountain Trench in British Columbia and are found east and west of the Tintina Trench in the southern Yukon. The overall pattern of the occurrences indicates that the shallow neritic portion of the continental shelf in Early Cambrian time traces a pattern widely diverse from that of the later, superimposed, Laramide structural trend. Portions of the continental shelf were already in existence west of the Rocky Mountain Trench by Early Cambrian time.
Paleomagnetism of Steel Mountain and Indian Head anorthosites from western Newfoundland
Authors: Murthy G. S. , Rao K. V.
Published: April 2011

As part of studies of anorthosites from the northern hemisphere, the paleomagnetism of two anorthosite inliers at Indian Head and Steel Mountain in western Newfoundland is described. The six sites at Indian Head retain a stable remanent magnetization and yield a paleomagnetic pole at 8 °S, 157½° E(δp = 15°, δm = 20°). This is close to poles for anorthositic and other rock units from within the Grenville Province that represent magnetization of age 1000 m. y., suggesting that there is no relative rotation between western Newfoundland and the southeastern part of the Canadian Shield, at least since the time of the Grenville orogeny. The ten sites at Steel Mountain also retain a stable magnetization, which yields a paleomagnetic pole at 22½° S, 41 °W (δp = 8°, δm = 14°). This position is closer to lower Paleozoic poles from Newfoundland and thus probably represents a lower Paleozoic magnetization.