bluuebunny/crossref_metadata_2025 huggingface dataset:
Relative risks of fungal rot for temperate ericaceous fruits: effects of seasonal variation on selection for chemical defense
Authors: Cipoluni Martin L. , Stiles Edmund W.
Published: October 2008

To quantify factors influencing the risk of fungal rot for vertebrate-dispersed fruits and to refine predictions concerning antifungal defense patterns, we examined physical, chemical, and phenological characteristics of ericaceous plants in New Jersey. In the field, three summer-ripening species had shorter persistence in the ripe state, shorter total retention times, and lower fungal resistance than three fall-ripening species. Summer fruits also had higher pulp carbohydrate content, lower fiber content, and (or) lower seed/pulp ratios. Whereas fungal colonization rates were somewhat lower during the ripening periods of summer species, fungal growth rates were higher owing to higher summer temperatures. In vitro fungal growth tests indicated only small effects of pulp nutrient content on fungal growth. We suggest that seasonal and chemical nutrient factors influencing risk of fungal rot for our study species are of minor significance relative to the degree to which these factors affect fruit removal by dispersers. We predict that owing to selection for high palatability, summer species should exhibit antifungal defenses with little or no antifrugivore effects (microbe-specific defenses). We also predict that because of consistently high removal rates (lower apparency), summer fruits should exhibit antifungal defenses less effective than those of fall species. Key words: antifungal defense, coadaptation, fruit rot, fruit nutrients, secondary chemistry, seed dispersal.
Evidence for geomagnetic field excursions and secular variation from the Wrangell Volcanics of Alaska
Authors: Bingham D. K. , Stone D. B.
Published: October 2008

Paleomagnetic studies have been made on 36 late Tertiary lava flows (3–4 m.y.) from the Wrangell Volcanics. Final flow mean remanent magnetization directions show excursions of the geomagnetic field away from a mean corresponding to a geocentric axial dipole field. They also point to the possibility that such excursions may have been a more common occurrence at the time of extrusion of these lavas than appears to have been the case in Quaternary times. These excursions may be due to increased non-dipole field activity. Calculation of the paleosecular variation including field excursion data leads to high values of PSV which do not agree with existing models. Exclusion of field excursion data gives a result that is consistent with current PSV models, but does not allow differentiation between them.
Paleomagnetism of the Great Slave Supergroup, Northwest Territories, Canada: the Tochatwi Formation
Authors: Evans M. E. , Bingham D. K.
Published: October 2008

The Tochatwi Formation comprises some 800 m of fine-grained red to buff sandstone in the upper part of the Great Slave Supergroup. Recent geological work indicates an age of 1700 m.y., but this is not yet known with certainty. Results from 29 sampling sites stratigraphically covering the Tochatwi Formation are presented. Standard paleomagnetic techniques indicate that post-folding remagnetization is common, and this is confirmed by analysis of the magnetic vectors removed as partial thermal demagnetization proceeds. Two phases of remagnetization are recognized, one of which can be attributed to nearby Mackenzie-age intrusions. The other phase is equivalent to a remagnetization observed by other workers in Kahochella Group strata at localities 70 km away. As yet, the source of this remagnetization event cannot be identified. Eight sampling sites have escaped total remagnetization and an earlier, pre-folding remanence has been isolated from these (D = 030, I = −11, k = 14, α95 = 15°). The corresponding pole position (144W, 18S) is remote from those deduced from North American rocks of similar age, and possible explanations of this problem are discussed.
Thermoluminescence as a potential means of dating siliceous ocean sediments
Authors: Huntley D. J. , Johnson H. P.
Published: October 2008

The natural thermoluminescence of siliceous shell separated from two North Pacific deep-sea cores has been measured. The thermoluminescence shows a single peak at ~240 °C, the intensity of which increases with depth up to a limiting value. Measurements of sample radiation-sensitivity and the determination of radiation dose rates are also presented. It is concluded that thermoluminescence dating is a potentially viable dating technique for such material.
Paleomagnetic study of lower Mesozoic diabase dikes and sills of Connecticut and Maryland
Authors: Smith Timothy E.
Published: October 2008

Paleomagnetic results from 61 sites on diabase dikes and sills in Connecticut and Maryland yield a mean pole of position of 100.9 °E. 68.6 °N, α95 = 1.6°. These results combined with those from 7S sites on four diabase sills in the Gettysburg Basin of Pennsylvania produce a mean pole position of 101, 6 °E. 65.4 °N, α95 = 1.3 °from 139 VGPs. These rocks arc probably of Early to early Middle Jurassic age by stratigraphic and inferred stratigraphic position. The paleomagnetic results indicate that the Gettysburg and Hartford Basins did not subside simultaneously.The dispersion of virtual geomagnetic poles about the mean pole of the Connecticut, Pennsylvania, and Maryland intrusive rocks is probably the result of 'homogenization' of magnetic directions during low-temperature oxidation of titanomagnetite to titanomaghemite over a period long enough to erase a considerable amount of dispersion due to secular variation.Rotation of Europe against North America in the prerifting configuration causes good convergence of European Jurassic mean poles and the pole of the Connecticut. Maryland, and Pennsylvania intrusive rocks. This is evidence that separation of the two continents had not begun by Early to early Middle Jurassic time, which is in agreement with earlier findings based on sea-floor magnetic anomalies and faunal assemblages.
Longshore sediment transport and a sediment for the Malpeque barrier system, southern Gulf of St. Lawrence
Authors: Armon J. W. , McCann S. B.
Published: October 2008

Wave hindcasting and refraction techniques were used to establish inshore wave conditions and longshore sediment transport rates along a 43 km barrier island shoreline at Malpeque, Prince Edward Island, in the southern Gulf of St. Lawrence. Net longshore sediment transport is directed southeastwards, at rates varying from 40 000 m3 year−1 to greater than 200 000 m3 year−1. The information on longshore transport was combined with volumetric estimates of shore normal sedimentary exchanges to define the sediment budget of the barrier sands at Malpeque. The results of the budget analysis indicate that subtidal erosion in the shoreface zone is the principal source of sand for the longshore transport system.
The geochemistry of possible metavolcanic rocks and their relationship to mineralization at Montauban-Les-Mines, Quebec
Authors: Stamatelopoulou-Seymour Karen , MacLean Wallace H.
Published: October 2008

Base metal and gold ores in thin calc-silicate and cordierite gneiss units at Montauban-Les-Mines have historically been described as pyrometasomatic deposits related to granitic intrusions. They are stratigraphically overlain by quartzo–feldspathic gneiss and amphibolite, the uppermost amphibolite unit being a pillowed metabasalt.Chemical analysis shows all the amphibolites to be derived from basic igneous rocks, probably basaltic flows or shallow intrusives. Some analyses of quartzo–feldspathic gneisses follow igneous trends on variation diagrams and plot closely with those of indisputable volcanic rocks associated with massive sulfide deposits from the Kuroko District, Japan, and Noranda, Quebec. They appear to be metamorphosed intermediate to acidic volcanic tuffs and associated sediments, and are thus termed 'leptites'.The volcanic environment of the ore deposits, their general conformability to stratification, and other distinguishing features, strongly suggest they may be exhalite deposits formed in the overlapping carbonate–sulfide facies.
The South Mayo Trough: a possible Ordovician Gulf of California-type marginal basin in the west of Ireland
Authors: Ryan Paul D. , Archer Jean B.
Published: October 2008

The South Mayo Trough, an early Ordovician sedimentary basin, was developed at the southern margin of the Laurentian plate. It controlled deposition of 12.8 km of sediment. Basic vulcanism accompanied the opening of the trough. This was followed by the deposition of turbidites and finally of fluvio-deltaic sediments. Initial island arc vulcanism was replaced by a bimodal basalt–rhyolite suite during sedimentation. The trough was bounded to the north and south by metamorphic source areas, of which the southerly, the Connemara Cordillera, was the more important. The Connemara Cordillera, comprised of Dalradian continental margin sediments, was deformed and metamorphosed before the trough's formation. Uplift and erosion of Connemara, opening of the trough, and change in vulcanism all occurred during late Tremadoc – early Arenig times. These events are related to the collision of the Iapetus ridge with a trench to the south of Connemara, which initiated a Gulf of California-type marginal basin, the South Mayo Trough. Comparisons between the morphology and sedimentary history of the trough with that of the Gulf of California and the geology of their adjacent source areas support this hypothesis.
Dépôts et phénomènes éoliens sur l'île de Banks, Territoires du Nord-Ouest, Canada
Authors: Pissart A. , Vincent J.-S. , Edlund S. A.
Published: October 2008

At the present time, eolian processes are active in many localities on Banks Island. Sediments of alluvial and outwash plains, as well as previously stabilized areas of eolian sands and areas where sandy Mesozoic and Tertiary deposits crop out, are subject to deflation. Locally ventifacts have been faceted.The vegetation cover of surfaces subject to eolian activity is described, as well as the main species observed on these surfaces.The eolian deposits of lower Thomsen River are described in detail. The study of a section has shown that ice-wedge polygons developed during periods of sand accumulation. The formation of segregation ice at the top of the permafrost, when it is raised because of the accumulation of eolian sands on the surface, is outlined.Two radiocarbon age determinations from two different sites along Thomsen River show that the deposition of eolian sands began 3790 ± 90 years BP (GSC-2119) and 3460 ± 80 years BP (GSC 2124). Ages of 5800 ± 180 years BP (GSC-2242) and 8430 ± 120 years BP (GSC-2419) were obtained respectively for the start of eolian sedimentation along Bernard River and on the outwash surface situated southeast of Sachs Harbour. The hypothesis that the initiation of eolian activity around 4000 years ago may have been the result of a drier and cooler climate on Banks Island is put forward.
Paleocontinental slopes of East Coast Geosyncline (Canadian Atlantic margin)
Authors: King Lewis H. , Young Ian F.
Published: October 2008

A study of processed seismic reflection profiles along the eastern Canadian continental margin indicates the occurrence at depth of paleocontinental slopes of Cenozoic–Mesozoic age, generally in the vicinity of the present continental slope. The paleoslopes are of two general types, constructional and destructional, formed respectively by progradational processes and mass wasting. The inclined beds of the progradational sequence (clinoform beds) represent the constructional slopes and were probably formed at times when deposition was simultaneous on the shelf, slope, and rise. Conditions leading to the establishment of a relatively deep shelf edge would favor constructional slope formation and preservation. A relatively shallow shelf edge, common during times of low sea level, would promote cutback at the shelf edge and upper slope and lead to the formation of destructional slopes. The depth of the shelf edge is mainly established by the balance between rates of sedimentation and subsidence in conjunction with the processes arising from variations in sea level.The sequence of constructional and destructional paleocontinental slopes varies widely along the Canadian Atlantic margin. On the western Scotian Shelf adjacent to the LaHave Platform the paleoslopes are mainly destructional and are in proximity, with only fragmental expression of former constructional slopes remaining. On the eastern Scotian Shelf and Grand Banks destructional paleoslopes are widely spaced in section between thick areas of constructional slope development. Paleoslopes along the northeast Newfoundland and Labrador Shelves are mainly constructional. The differences may be related to age of opening of the Atlantic Basin.The type and distribution of paleocontinental slopes along a margin could influence the migration of hydrocarbons from the eugeocline to the miogeocline.
The use of paleomagnetic data to delineate the history of the development of the Connemara Antiform
Authors: Morris W. A. , Tanner P. W. G.
Published: October 2008

The tectonic evolution of the Connemara Gabbro Suite as deduced from careful tilt correction of the initial remanence directions, and interpretation of locally reset magnetizations is substantially in agreement with that based on purely geologic criteria. Fold tests of remanence suggest the gabbro bodies acquired their remanence after the F3 folding phase but before the F4, Connemara Antiform folding phase, sometime between 440–490 Ma. After unfolding both limbs of the antiform so that the remanences of the two limbs coincide, an antiformal structure still remains. Therefore, the F3 hinge surfaces were not coplanar at the time of gabbro intrusion, and the Connemara Antiform had already begun to develop before the members of the gabbro suite had had sufficient time to cool below the Curie point. During the development of the F4, localized remagnetization occurred at two particular periods.It was not possible to obtain a unique remanence direction by 'unfolding' the limbs of the F4 antiform about its eastward plunging axis; a virtual geomagnetic pole cannot be quoted. Much of current paleomagnetic research is aimed at defining paleopole positions, so that in cases where they are required extreme care must be exercised in applying geologically appropriate tilt corrections, and where more than one correction is required, they must be applied in the correct sequence.
The probable extent of Classical Wisconsin ice in southern and central Alberta
Authors: Stalker A. MacS.
Published: October 2008

The margin of a former Laurentide ice sheet is traced through southern and central Alberta, from the Saskatchewan border southeast of Medicine Hat to beyond Rocky Mountain House, southwest of Edmonton. This margin, which marks the limit of a significant glacier advance or readvance, is thought to represent the maximum extent of Laurentide ice on the Canadian prairies during Classical Wisconsin time. In the south this margin follows a well-developed hummocky moraine; in the north it is indicated mainly by a discordance in trend of ice-flow markings, a disruption of drainage, and a change in maturity of topography on either side.
Glacier-caused slide near Pylon Peak, British Columbia
Authors: Mokievsky-Zubok O.
Published: October 2008

A glacier-initiated land–ice slide occurred on the southwestern side of Devastation Glacier near Pylon Peak in the Coast Mountain Range, British Columbia, in July 1975. An estimated 2.5 × 106 m3 of ice and about 26 × 106 m3 of debris descended 1150 m over a distance of 6.5 km and blocked Meager Creek, forming a small lake. The slide claimed the lives of four people on a sand bar at Meager Creek.
Imbricated terranes of the Cariboo gold belt with correlations and implications for tectonics in southeastern British Columbia
Authors: Struik L. C.
Published: October 2008

The Cariboo gold belt of east-central British Columbia is divided into four fault-bounded sequences of distinct stratigraphy. They are, from east to west, the Cariboo (continental-shelf sediments), Barkerville (continental-shelf sediments and intercalated volcanics), Slide Mountain (rift-related submarine pillow basalt, chert, and diorite) and Quesnel (island-arc sediments and subaqueous volcanics) terranes. Each is separated from others by thrust faults. Grit, phyllite, limestone, and volcanics of the Barkerville terrane may be correlative with the Eagle Bay Formation near Adams Lake and the Lardeau Group near Kootenay Lake. Barkerville terrane may be part of a more regional rock package, Selkirk terrane, which is defined to include Kootenay terrane, Badshot Formation, and Horsethief Creek and Hamill groups. Selkirk terrane is (i) separated everywhere by a low-angle fault from the overlying age-equivalent but stratigraphically and structurally different Cariboo terrane and (ii) separated by a system of faults in the general location of the Southern Rocky Mountain Trench from the age-equivalent but stratigraphically and structurally different North American terrane of the Rocky Mountains.
Relocation of the north magnetic dip pole
Authors: Newitt L. R. , Niblett E. R.
Published: October 2008

An analysis of data gathered between May 13 and May 18, 1984, gives a new position for the north magnetic dip pole of 77.0°N, 102.3°W. The pole has moved an average of 11.6 km per year approximately northwest during the past decade. Data used in the analysis consisted of absolute observations of the magnetic declination, inclination, and total intensity for seven sites in the vicinity of the pole. Variometer data from King Christian Island were used in conjunction with the absolute observations to calculate mean values for the quietest 6 h interval during the survey period. Additional data from Resolute Bay observatory allowed further reduction of the observations to representative annual mean values, centred at 1983.9, from which the pole position was determined using the novel method of spherical cap harmonic analysis.
U–Pb ages for late magmatism and regional deformation in the Shebandowan Belt, Superior Province, Canada
Authors: Corfu F. , Stott G. M.
Published: October 2008

Five precise U–Pb zircon (and titanite) ages from different lithologic units of the Shebandowan greenstone belt in the western Wawa Subprovince of the Superior Province put tight constraints on the time of late Archean magmatism and of two major deformation events.A porphyry sill from the older supracrustal sequence has an age of 2733 ± 3 Ma. Another porphyritic rock, a trondhjemite occurring as a clast in a conglomerate of the unconformably overlying Timiskaming-type supracrustal sequence, formed 2704 ± 2 Ma ago and defines a maximum age for the deposition of the Timiskaming-type sequence. An alkalic volcanic rock from this sequence has been directly dated at [Formula: see text], in accord with the above constraint and with another probable maximum age of deposition given by the date of 2696 ± 2 Ma for the Shebandowan Lake Pluton. A first deformation event (D1) was related to a predominantly vertical tectonic regime and occurred during or before intrusion of the Shebandowan Lake Pluton at 2696 ± 2 Ma. The second deformation event (D2) was caused by northwesterly-directed compression and occurred after [Formula: see text] ago, the age of the Timiskaming-type volcanic rocks. A minimum age for the D2 deformation event, which also affected the adjacent Quetico metasedimentary belt and was probably related to the development of major transcurrent fault systems throughout the Superior Province, is provided by an age of [Formula: see text] for the undeformed, late-kinematic Burchell Lake Pluton.
Precambrian basement geology of North and South Dakota
Authors: Klasner J. S. , King E. R.
Published: October 2008

Combined analysis of drill-hole, gravity, and magnetic data indicates that the buried Precambrian basement rocks of the Dakotas can be divided into several lithotectonic terranes. Eastern North Dakota and northeastern South Dakota are underlain by Archean gneiss. Except for the Black Hills region of South Dakota, where Archean rocks are also exposed, the western third of both Dakotas is underlain mainly by Early Proterozoic gneiss and metasedimentary rocks. Part of this region is underlain by Archean crust with an Early Proterozoic tectonic overprint. A broad transition zone of strongly overprinted Archean crust occurs between the Proterozoic rocks to the west and the Archean rocks to the east. South central South Dakota is underlain by an Early Proterozoic batholith. Early Proterozoic felsic volcanic rocks occur in southeast South Dakota. The bootheel portion of South Dakota contains a diverse assemblage of basement rocks that are partly Archean in age.Churchill Province rocks of the Trans-Hudson foldbelt project into the western Dakotas. The Thompson nickel belt and the Pickwitonei gneiss belt correlate with the western and eastern halves, respectively, of the transition between Archean and Proterozoic crust, and the Archean Glennie – Hanson Lake microcontinent of the Churchill Province likely extends into western North Dakota. Archean rocks of Minnesota extend into the eastern Dakotas, and the Wyoming craton extends to the Black Hills region. The Cheyenne foldbelt projects into southwest South Dakota. The Penokean foldbelt of Michigan and Wisconsin does not extend into the Dakotas, but it most likely extends into northwest Iowa.Tectonic evolution of the Early Proterozoic terrane in the Dakotas was most likely similar to plate tectonic models for the evolution of the Trans-Hudson foldbelt in the Churchill Province. As in the Churchill Province, the western Dakotas are underlain by Early Proterozoic rocks, but it is not known whether these rocks formed as a result of rifting and subsequent closure of a once extensive Archean crust or as a result of collision of once widely separated blocks of Archean crust.
Contrasting secondary mobility of Ti, P, Zr, Nb, and Y in two metabasaltic suites in the Appalachians
Authors: Murphy J. Brendan , Hynes Andrew J.
Published: October 2008

Substantial mobility of high-field-strength (HFS) elements (Ti, Y, P, Zr, and Nb) during greenschist facies metamorphism of two metabasaltic suites from the Appalachians, the Ascot Formation of southeastern Quebec and the Arbuckle Brook Formation of Nova Scotia, is attributed to the presence of CO2 in the fluid phase during metamorphism. The style of the mobility exhibited by these two suites is different. In the Ascot Formation, metasomatism affected rocks rich and poor in carbonates; it led to enrichment in some HFS elements and depletion in others. In contrast, in the Arbuckle Brook Formation there was depletion in CO2-rich rocks of all HFS elements and consequently much less fractionation between HFS elements.These differences may be explained by the relative effectiveness of [Formula: see text] buffering in the two suites. In the Ascot Formation, buffering was ineffective, and several different mineral assemblages were developed, reflecting a range in [Formula: see text]. Mobility of HFS elements was controlled by chemical potential differences between these mineral assemblages. In the Arbuckle Brook Formation, [Formula: see text], was externally buffered, and all rocks have the same mineral assemblage, varying only in modal calcite. Mobility of the HFS elements was controlled by the partitioning of these elements between the mineral assemblage and the fluid.Depletion of HFS elements in the Arbuckle Brook Formation is well correlated with the amount of calcite in the rocks. The systematics of the depletion allow an estimate of the relative proportions of HFS elements removed in the fluid. They are different from those in the rocks and lead to changes in the interelement ratios with progressive carbonation. However, low-carbonate rocks provide reasonably reliable estimates of primary concentrations. In certain circumstances, low-carbonate rocks (i.e., rocks that appear to be relatively fresh) do not provide reliable estimates of primary concentrations. A careful examination of the systematics of carbonation is required in metabasaltic suites for which HFS-element concentrations are the major indicator of magmatic and (or) tectonic affinity.
Pétrologie des roches volcaniques de sillon de roches vertes archéennes de Matagami–Chibougamau à l'ouest de Chapais (Abitibi est, Québec), 2. Le groupe hautement potassique d'Opémisca
Authors: Picard Christian , Piboule Michel
Published: October 2008

In the western part of the Chapais syncline (Abitibi East, Quebec), the Opemisca Group unconformably overlies the Roy Group at a low angle. It consists of a thick turbidite sequence covered by an interdigitated sequence of lavas and alluvial cone sediments. The subaerial lavas include two sequences evolving from porphyric metabasalts to metatrachyandesites and porphyric metatrachytes (lower sequence) or to K-rich aphanitic meta-andesites (upper sequence). These lavas, with calc-alkaline to shoshonitic affinity, have high K2O, Ba, Sr, and Th contents and show highly enriched LREE spectra.The behaviour of major elements, trace elements, and lanthanides suggests an origin from partial melting of a mantle source consisting of a garnet lherzolite enriched in K, Sr, Rb, Ba, and Th by volatile elements and also by crustal contamination and by fractional crystallization mechanisms. The evolution of the lavas of the lower sequence, progressively deficient in Y, seems to have been controlled by fractional crystallization of a plagioclase, clinopyroxene, and olivine mixture; this was followed for the metatrachyandesites and metatrachytes by high H2O activity of a feldspar, amphibole, titanomagnetite, and apatite mixture. The evolution of lavas enriched in Y in the upper sequence seems to have been controlled by weak H2O activity of the anhydrous plagioclase, clinopyroxene, and olivine assemblage.The petrographic and geochemical data suggest an emplacement similar to that occurring on the active continental margins of the central Andes and implies the existence of a late-stage ensialic arc. [Translated by the journal]
Neoglacial history of the Stikine–Iskut area, northern Coast Mountains, British Columbia
Authors: Ryder J. M.
Published: October 2008

Information about Neoglacial features was obtained from aerial photograph interpretation, observations during low-level flights, ground checking, and historical records. Terminal moraines at Great, Flood, and Mud glaciers date from the late seventeenth to early eighteenth centuries, and recessional moraines at these glaciers and terminal moraines at glaciers farther east date from the late nineteenth to early twentieth centuries. These late Neoglacial terminal moraines appear, in general, to mark the greatest post-Pleistocene extent of the glaciers. Radiocarbon dates from overridden trees and soil indicate that 500–600 14C years BP glaciers were considerably more extensive than they are at present and were advancing. Preservation of a 3800 14C year old caribou antler in a snowbank that is now rapidly shrinking suggests that climate has been relatively cool and moist for the past four millennia.
The geological structure and distribution of Paleozoic rocks on the Avalon Platform, offshore Newfoundland
Authors: Durling P. W. , Bell J. S. , Fader G. B. J.
Published: October 2008

Single-channel seismic reflection profiles obtained across the Avalon Platform, offshore Avalon Peninsula, Newfoundland, have been studied for seismic reflections and interpreted in conjunction with lithologic and biostratigraphic data. Formline structural mapping revealed a 4000 m thick Ordovician–Silurian marine shale sequence that is gently folded about north-northwest–south-southeast axes and is unconformably overlain by a synclinal outlier of Devonian(?) redbeds approximately 700 m thick.The Avalon Platform on the Grand Banks may represent a mildly deformed Acadian terrane, which is contiguous with onshore Avalonian sequences, or it may be part of a foreland zone adjacent to an overthrust belt, or both.
Blueschist and eclogite in mylonitic allochthons, Ross River and Watson Lake areas, southeastern Yukon
Authors: Erdmer Philippe
Published: October 2008

Two new occurrences of eclogite associated with mylonitic rocks are documented. The first, near Ross River, is in a quartz-rich metasedimentary host that includes glaucophane schist. The host forms part of a belt of high-pressure rocks more than 50 km long and several kilometres wide between Ross River and Faro. In the second occurrence, north of Watson Lake, eclogite is associated with mafic and ultramafic rocks occurring in a klippe more than 100 km2 in area that rests on unmetamorphosed Triassic rocks of the North American miogeocline. Geothermobarometry shows that the eclogites were metamorphosed at 10–15 kb (1 kb = 100 MPa), between 470 and 750 °C. These peak conditions are comparable to those for other eclogites in the Yukon and adjacent Alaska. The age of metamorphism and mylonitization is Triassic or older.The high-pressure rocks occur at the leading edge of the most inboard accreted terrane, along its boundary with North American miogeoclinal strata, over a length of several hundred kilometres. Their extensive distribution makes these rocks regionally mappable units. This supports other evidence that both the Yukon–Tanana terrane and mylonite sheets obducted on North American foreland rocks are composed in part of trench and subduction-zone material.
Origin and paleoecology of post-Lake Agassiz raised beaches in Manitoba
Authors: Nielsen Erik , McNeil David H. , McKillop W. Brian
Published: October 2008

Post-Lake Agassiz raised beaches have been identified 6 m above the present level of Lake Winnipegosis. The level, termed the Dawson level, is radiocarbon dated at 4870 ± 80 years BP (GSC-4138) and 4900 ± 70 years BP (GSC-4139) at Dawson Bay and at 5050 ± 100 years BP (BGS-1126) at Denbeigh Point. The dates are estimated to be 350 years too old due to the hard-water effect and the Dawson level is believed to have formed about 4550 years ago. The 6 m drop in the level of the northern part of Lake Winnipegosis is attributed to isostatic tilting. The fossil assemblages of the beaches are the same and are dominated by the extinct gastropod Marstonia gelida. Two marine invertebrates, the foraminifer Elphidium gunteri and the ostracod Cytheromorpha fuscata, are present in the samples. These marine animals are believed to have been brought into the area by migrating waterfowl and to have survived because of the high salinity of the lake.
Preliminary paleomagnetic results from the Permian Asitka Group, British Columbia
Authors: Irving E. , Monger J. W. H.
Published: October 2008

Tuffs, rhyolites, and basalts collected at seven sites (25 samples) in the Early Permian Asitka Group of Stikinia have similar paleomagnetic inclinations, and corresponding paleolatitudes of 23 ± 6, 21 ± 4, and 23 ± 5 °respectively. Both polarities occur, so the paleolatitudes could be either north or south of the paleoequator, although the polarity bias favours the former option. The paleolatitude expected for the sampling region is 27 ± 4°N. Adopting the paleomagnetically more probable northern option, the mean displacement relative to the North American craton is 5 ± 6°, indicating that Stikinia was in much the same latitudinal position relative to the craton during the Early Permian as it is at present, although possibly somewhat to the south. The declinations are in poor agreement, indicating that relative rotations occurred in this faulted terrane.
Stratigraphy and depositional environments of the Upper Mississippian Codroy Group: Port au Port Peninsula, western Newfoundland
Authors: Dix George R. , James Noel P.
Published: October 2008

Upper Mississippian (middle Viséan) biohermal limestones, siliciclastics, evaporites, and red beds of the lower Codroy Group (correlative with the lower Windsor Group in Nova Scotia) bevel a rugged paleokarst of Late Devonian – Early Mississippian age on the Port au Port Peninsula, western Newfoundland. Laminated limestones (Ship Cove Formation) and overlying evaporites (Codroy Road Formation) are similar to the sequence in the Bay St. George Subbasin, southwestern Newfoundland. In the Port au Port region, this sequence is laterally equivalent to biohermal limestones and plant-bearing siliciclastics of the proposed Big Cove Formation and red beds of the Lower Cove Formation. Lithostratigraphic correlation is supported by miospore and conodont biostratigraphies. Use of macrofaunal subzones is cautioned because there is evidence for the need to reevaluate the ranges of fossils that have previously been considered key indicators (e.g., Martinia galataea Bell) for parts of the Codroy and Windsor groups.The nature and lateral changes in Late Mississippian depositional environments and biofacies in the Port au Port region were the result of partial submergence of a complex predepositional topography and differential freshwater runoff (from the exposed Port au Port Ridge) creating fluctuating salinities and varying influx of siliciclastics. Limestone–evaporite sequences developed in broad, flat basins, carbonate buildups and siliciclastics accumulated in partially submerged paleokarst valleys adjacent to a rocky shoreline, and red beds formed part of the adjacent terrestrial landscape.
Grenville orogenic affinities in the Red Mountain area, Llano Uplift, Texas
Authors: Carter Karen E.
Published: October 2008

The Red Mountain area in the southeast corner of the Llano Uplift contains evidence of a Grenville-age, polyphase, non-coaxial deformational history. Four synmetamorphic deformational phases affected the Precambrian Click Formation of the Packsaddle Group, and a single shear-related deformation is observed in the Big Branch and Red Mountain gneisses. The first phase of deformation produced tight folds with an axial–planar metamorphic foliation. The second, and most intense, pervasive deformational phase produced the regional metamorphic layering, isoclinal folds, transposition of bedding, and mylonitic textures in the gneisses. The third deformation is characterized by tight to isoclinal, north-verging folds with an axial–planar differentiation crenulation cleavage. The fourth phase of deformation resulted in a north-northwest-trending differentiation crenulation cleavage that is axial–planar to small east-northeast-verging folds. The growth of cordierite over all foliations indicates that low-pressure metamorphism postdated all four deformational phases.The second deformation had begun at the latest by 1167 ± 2 Ma, the age of metamorphism of the gneisses, and before the intrusion of melarhyolite dikes dated at 1080 ± 30 Ma. Thus, the orogenic event(s) responsible for the complex deformational and metamorphic history is Grenvillian in age.
Kennedy Channel Formation: key to the early history of the Franklinian continental margin, central eastern Ellesmere Island, Arctic Canada
Authors: Long D. G. F.
Published: October 2008

The Franklinian sequence in the Canadian Arctic Islands may have been initiated by rifting in Late Proterozoic or Early Cambrian times. Unfortunately, no record of this early phase of basin evolution is exposed; the oldest known strata are weakly metamorphosed mudstones, limestones, and sandstones of the Kennedy Channel Formation. Although these have previously been considered late Precambrian in age, the presence of minor trilobite and brachiopod debris indicates an Early Cambrian age, possibly corresponding to a pre-Olenellus trilobite zone. Strata of the Kennedy Channel Formation reflect repeated progradation of shallow-water facies into a slowly subsiding basin that developed in response to subsidence at a late stage of rift development along the Franklinian shelf margin. The first two cycles involve storm- and tide-influenced clastics derived from the Precambrian Shield to the southeast, whereas the third and fourth cycles involve progradation of carbonate ramp and rimmed platform facies. The contact with overlying dolostones of the Ella Bay Formation represents a depositional and diagenetic facies boundary and not an unconformity.
Ceraurus and related trilobites from the Middle Ordovician Bobcaygeon Formation of south-central Ontario, Canada
Authors: Hessin William A.
Published: October 2008

Four cheirurine trilobite species belonging to three closely related genera are described from the Middle Ordovician Bobcaygeon Formation (Rocklandian–Kirkfieldian) of the Lake Simcoe area in south-central Ontario. Bufoceraurus is a new genus characterized by its large size, profuse, wart-like tubercles over the entire exoskeleton, short posterior border spines on the cephalon, short thoracic pleural spines, and large pygidium with two pairs of prominent posterior spines. The genus is represented by Bufoceraurus bispinosus (Raymond and Barton 1913). Gabriceraurus hirsuitus (Ludvigsen 1979b), Ceraurus plattinensis Foerste, 1920, and Ceraurus cf. globulobatus Bradley, 1930 are other species documented. Complete dorsal exoskeletal reconstructions are presented for all species based on well-preserved material. Hypostomes are known for all species.
Pareiasaurs from the Upper Permian of north China
Authors: Keqin Gao
Published: October 2008

Fossils from the lower part of the Shihtienfeng Formation, Upper Permian of north China, include the type specimen of a new genus and species of pareiasaur and less complete materials identified as Shansisaurus sp. and Pareiasauridae gen. et sp. indet.Based on the distribution of pareiasaurian fossils in the Upper Permian of north China, the upper part of the Shihtienfeng Formation can be correlated with the Daptocephalus Zone, the lower part with the Cistecephalus Zone, and the upper part of the Upper Shihezi Formation with the Tapinocephalus Zone of South Africa.
Exemples de mélange de magmas en contexte plutonique: les enclaves des tonalites–granodiorites du massif de Bono (Sardaigne septentrionale)
Authors: Cocirta C. , Orsini J. B. , Coulon C.
Published: October 2008

In calc-alkaline orogenic plutons, the dark xenoliths and their host rocks must be considered the expression of partial mixing of magma.Three associations of this type have been investigated and are illustrated by the Bono pluton (northern Sardinia)— a composite pluton including three intrusives of different nature (tonalitic to granodioritic) and containing a very large number of basaltic xenoliths of magmatic origin. Detailed mineralogical analysis of the two end members in each association, coupled with geochemical data, has determined the major petrogenetic mechanisms intervening in the mixing process in a plutonic setting: temperature equilibration, mechanical exchanges of crystals, chemical exchanges, etc. The most important result of this article, however, is to show that each intrusion is related to a specific group of xenoliths that is characterized by constant FeOt/MgO. The latter reflects the different composition of basaltic components, and it is concluded that each intrusive event is associated with a unique mixing episode. As in volcanic settings, the mixing process may have initiated the intrusion.The extreme compositional variations in the magmatic xenoliths, recognized in several series of orogenic plutons, is explained here by different initial basaltic end members and by variation in the intensity of the interaction mechanisms. [Journal Translation]
The age and significance of Carboniferous plutons of the western Cobequid Highlands, Nova Scotia
Authors: Pe-Piper Georgia , Cormier R. F. , Piper David J. W.
Published: October 2008

A series of granite plutons with minor gabbro–diorite phases outcrops immediately north of the Cobequid Fault in the western Cobequid Highlands, Nova Scotia. The plutons were cut by numerous dykes, and parts of some plutons and some dykes subsequently underwent ductile deformation. Four Rb–Sr whole-rock–K-feldspar isochron dates ranging from 338 to 356 Ma have been obtained from these plutons and the dykes that cut them. The ages of these plutons are indistinguishable from an age of 341 Ma obtained for the nearby Fountain Lake Group volcanic rocks, within estimated uncertainties. Measured Carboniferous granite ages are uncommon in the Appalachian Orogen of eastern Canada. The geochemical character of these plutons indicates that they result from crustal extension. This extension and the compression observed in the granites with ductile deformation are related to transcurrent motion between the Avalon and Meguma terranes along the Minas fault zone.Preliminary Rb–Sr whole-rock data from poorly exposed plutons in the northern part of the Cobequid Highlands suggest a Middle to Late Devonian or older age. These plutons may represent an earlier phase of crustal extension.
Ice-thrust terrains and glaciotectonic settings in central Alberta
Authors: Tsui Po C. , Cruden D. M. , Thomson S.
Published: October 2008

Airphoto analyses, geologic field mapping, and study of borehole logs and surficial topographic maps in ice-thrust terrains in central Alberta suggest that all these techniques are needed to identify ice-thrust terrains that may or may not have topographic expressions.Three geomorphological settings susceptible to glaciotectonic deformation are described as escarpment, valley, and plains settings. The bedrock slopes in the escarpment setting ranged from 19 to 51 m/km. The bedrock slopes in the valley setting ranged from 23 to 32 m/km, and the valley was 8.5 km wide between crests and 4 km at the bottom. The bedrock slopes of the plains setting ranged from 2 to 5 m/km.Ice-thrust features are found in topographic troughs in front of an ice sheet where water bodies were impounded. These proglacial water bodies thawed the permafrost in front of the glacier. The disintegration of proglacial permafrost decreased the resistance of subglacial strata to ice thrusting.Ice-thrust features can be expected in areas where local slopes are inclined upglacier toward the former glacier margin, where proglacial water bodies could be impounded, rather than in areas where slopes inclined downglacier away from the glacier margin, where the existence of a proglacial water body is unlikely.
The first records of Elmisaurus (Saurischia, Theropoda) from North America
Authors: Currie Philip J.
Published: October 2008

The discovery of a fused tarsometatarsus in the Upper Cretaceous (Campanian) strata of Dinosaur Provincial Park shows that Elmisaurus, previously known only from Mongolia, also lived in North America. Reexamination of the type specimen of "Ornithomimus" elegans (Parks 1933) confirms the identification and provides a species name. Elmisaurus elegans is more gracile than Elmisaurus rarus, has a weaker longitudinal ridge on the fourth metatarsal, and has a pair of distal processes on metatarsals II and IV. Although six theropod families had representatives in both North America and Asia during Cretaceous times, the degree of genetic similarity is poorly understood. Analysis of the Elmisaurus material suggests that faunal interchange was still underway during the Late Cretaceous.
Le Complexe d'Ascot des Appalaches du sud du Québec: pétrologie et géochimie
Authors: Tremblay Alain , Hébert Réjean , Bergeron Mario
Published: October 2008

This paper reviews new geochemical data obtained from Ordovician volcanics in the Ascot Complex of the Quebec Appalachians. The Ascot Complex is divided into three distinctive lithotectonic assemblages: the Sherbrooke, Eustis, and Stokes domains. The Sherbrooke Domain includes basalts, pyroclastic breccias, and felsic tuffs. The Eustis Domain is composed of volcanoclastic and pyroclastic rocks. The Stokes Domain is an assemblage of rhyolitic tuffs and basalts. The geochemical composition of the volcanics varies between basaltic and rhyolitic end members. Basaltic rocks are arc tholeiites (La/Yb = 0.5–2). Some basalts found in the Sherbrooke Domain show a composition very close to that of frontal-arc boninites (La/Yb = 1–2) and are depleted of rare-earth elements. Felsic rocks from the Sherbrooke Domain are poorer in light rare-earth elements (La/Yb = 0.5–0.7) than those from the Stokes Domain (La/Yb > 2). All of the felsic rocks are characterized by a negative Eu anomaly (Eu*/Eu = 1.3–3). The Stokes felsites are derived from an enriched magma contaminated by a continental crust component. The Sherbrooke Domain felsites are derived from a source impoverished in incompatible elements and enriched in high-partition-coefficient elements. Volcanic rocks from Sherbrooke and Eustis are thought to represent an incipient intra-oceanic arc. The rocks of the Stokes assemblage represent a more mature section of the same arc, explaining the contamination of generated magmas by continental crust components. The modern architecture of the Ascot Complex is essentially tectonic and may not correspond to the initial internal structure of this Ordovician arc. [Journal Translation]
Progressive hydrothermal alteration associated with gold mineralization of the Zone 1 intrusion of the Callahan property, Val-d'Or region, Quebec
Authors: Jenkins Cecilia L. , Trudel Pierre , Perrault Guy
Published: October 2008

The Zone 1 intrusion of the Callahan property, Val-d'Or, Quebec, is a relatively small (0.045 km2), pretectonic to syntectonic trondhjemitic mass that has been altered to varying degrees by progressive hydrothermal alteration. The entire intrusion is gold enriched, and the degree of mineralization is proportional to the degree of alteration. Examination of drill core reveals that visible colour variations are related to mineralogic and chemical alteration. Three degrees of alteration are identified: least, medium, and most-altered. The least-altered facies has a green–grey colour, whereas the medium-altered facies has a pale grey colour and the most-altered facies has a cream–white colour. As the intensity of alteration increases, the amount of albite, carbonate, and pyrite increases and the amount of phengite decreases. These progressive, mineralogic changes are correlated chemically to increases in Na2O, CO2, and S and to a decrease in K2O. The median gold values for least-, medium-, and most-altered trondhjemite are 42, 148, and 158 ppb, respectively, and the average gold values (excluding highly anomalous values) are 85, 172, and 188 ppb, respectively, indicating that gold enrichment is already advanced at the medium intensity of alteration. Despite its weak enrichment, tungsten is the most anomalous trace element of the typically gold-associated elements in lode deposits and is, therefore, of special interest. Gold, found principally in the medium- and most-altered facies, is most commonly observed as free grains in the gangue. It may also be associated with pyrite and, to a much lesser extent, with tellurides. The majority of the free gold grains have an estimated diameter between 20 and 60 μm, and their average composition is 95 wt.% Au and 5 wt.% Ag. This study and comparisons of the Zone 1 trondhjemitic intrusion with other gold-enriched, felsic intrusions in the Abitibi greenstone belt suggest that elevated sodium (i.e., albitization) and anomalous gold values, relative to barren felsic rocks, should be used to target ore-grade zones within pretectonic to syntectonic felsic intrusions.