bluuebunny/crossref_metadata_2025 huggingface dataset:
Some results of COCORP seismic reflection profiling in the Grenville-age Adirondack Mountains, New York State
Authors: Klemperer S. L. , Brown L. D. , Oliver J. E. , Ando C. J. , Czuchra B. L. , Kaufman S.
Published: April 2011

COCORP deep seismic reflection profiling in the Adirondack Mountains of northern New York State has revealed a prominent zone of layered reflectors in the lower crust of the east-central Adirondacks. The strong, layered reflectors (here termed the Tahawus complex) occur between 18 and 26 km depth, beneath the sparsely reflective, granulite-grade, surface terrane, which has been uplifted from depths greater than 20 km. The Tahawus complex apparently represents layered rocks of some type in the lower crust of the Adirondacks. Possibilities include gneissic layering, cumulate igneous layering, a layered sill complex, and underthrust sedimentary strata, The Tahawus complex may be spatially coincident with a previously detected, high-conductivity zone in the lower crust, suggesting that either unusual mineralogies or interstitial electrolytes are present in the Tahawus complex. In contrast to layered reflections discovered in the lower crust of the east-central Adirondacks and southeast of the Adirondacks, cross-cutting and discontinuous reflections are recorded from the upper crust on all the COCORP Adirondack lines, including lines in both the Adirondack Highlands and Lowlands. Available three-dimensional control suggests that reflections in the upper crust of the central Adirondacks are parallel to, and hence may be related to, the folded gneisses mapped at the surface. Shallow events are also observed on a COCORP profile close to the epicenter of the 7 October 1983 magnitude 5.2 earthquake in the central Adirondacks, but their relation to the earthquake is uncertain.
Encrinurids (Trilobita) from the Matapédia Group (Ordovician), Percé, Québec
Authors: Lbspérance Pierrb J. , Tripp Ronald P.
Published: April 2011

Three encrinurid species from the Ashgillian of the Percé area, Québec, are revised: Erratencrinurus (Celtenerinurus) perceensis (Cooper in Schuchert and Cooper), Erratencrinurus (s.l.) sp., and Atractopyge veneficus n. sp. Erratencrinurus (C.) perceensis closely resembles E. (C.) multisegmentatus (Portlock), probably indicating a Cautleyan age for the type locality, Priest's Road, and for unit 2 of the White Head Formation. Celtencrinurus is restricted to include only species closely resembling E. multisegmentatus, the type species. Atractopyge veneficus n. sp. resembles A. confusa Owen, from the Rawtheyan of the Oslo region, Norway, in cranidial characters, but the pygidium is distinctive.
Early Devonian volcanism in the eastern Klamath Mountains, California: evidence for an immature island arc
Authors: Lapierre H. , Albarede F. , Albers J. , Cabanis B. , Coulon C.
Published: April 2011

The Early Devonian volcanic sequence of the eastern Klamath Mountains (northern California) consists of the Copley Greenstone, a basalt–andesite series, overlain by the Balaklala Rhyolite. All the rocks are metamorphosed to the greenschist facies.The Copley Greenstone consists of massive flows and pyroclastic deposits in the lower part that are overlain by pillow lavas. No sediments are interlayered in the volcanic pile except in the easternmost outcrop area, where sandstones with granitic debris and shaly tuffs are interbedded in the uppermost flows. High-Mg andesites occur only near the top of the basic volcanic succession. The Balaklala Rhyolite is formed of massive flows, breccias, and tuffs.The Copley volcanic rocks, poor in titanium, belong to a low-K tholeiitic suite formed in an island-arc geodynamic environment. The occurrence of olivine with chromium spinels in almost all the lava types, the enrichment in magnesium, chromium, and nickel, and the depletion in hygromagmaphile elements suggest that magmatic differentiation was a marginal process. The Balaklala Rhyolite shows very homogeneous petrographic and geochemical features, characteristic of tholeittic products.From its characteristics here described (pillowed flows, lack of sedimentation, presence of high-Mg andesites and low-K rhyolites, bimodality of the volcanism) the Early Devonian volcanic sequence represents an immature island arc related to a back-arc basin, similar to the present-day Mariana island arc.
Delaciation of the Prince Rupert – Kitimat area, British Columbia
Authors: Clague John J.
Published: April 2011

Late Wisconsinan sediments in the Prince Rupert – Kitimat area of west-central British Columbia were deposited in an isostatically depressed marine environment affected by grounded tidewater glaciers. The most common sediments are (1) massive, bedded, and laminated muds, and (2) stratified sand and gravel. The former are accumulations of clay- and silt-size detritus transported in suspension from the mouths of meltwater streams and possibly in turbidity flows generated by submarine slope failures. The muds locally contain scattered ice-rafted stones, fossil marine molluscs, and foraminifera. The main sand and gravel deposits are elevated deltas, including both small incised fan-shaped forms at the margins of the main valleys and enormous ice-contact delta–sandur complexes on the floor of Kitsumkalum–Kitimat trough, the largest valley in the study area.Delaciation occurred by downwasting and complex frontal retreat between about 13 000 and 10 000 BP. The open outer coast became ice free first, in response to wholesale destabilization of the western periphery of the Cordilleran ice sheet by eustatically rising seas. Glaciers retreated rapidly by calving and soon were confined to fjords and mountain valleys; thereafter, they receded more slowly. The distribution of glaciomarine mud and raised deltaic deposits in Kitsumkalum–Kitimat trough indicates that retreat there was nonuniform, with intervals of catastrophic retreat separated by periods during which glacier snouts were relatively stable.Delaciation was accompanied and followed by rapid isostatic uplift. In Kitsumkalum–Kitimat trough, shorelines fell from about 200 m elevation at 10 500 BP to present sea level at about 8000 BP; about half of this fall occurred in perhaps as little as 500 years.
Observations of soil freezing and frost heave at Inuvik, Northwest Territories, Canada
Authors: Smith M. W.
Published: April 2011

Field observations of soil temperature, moisture regime, and frost heave in silty clay hummocks at Inuvik, Northwest Territories, over the fall and early winter reveal that a significant amount of moisture migration and frost heave occurs within frozen soil at temperatures down to −2.4°C. The field data are analysed using thermodynamic considerations, and the apparent hydraulic conductivity is determined as a function of negative temperature. The conductivity falls from near 7 × 10−9 m s−1 above 0 °C to about 3.5 × 10−12 m s−1 at −1 °C, then remains fairly constant down to −2.4 °C. The observed decrease in heave with time is explained in terms of a diminishing water supply at the base of the active layer.
Resetting of Nd and Sr whole-rock isochrons from polymetamorphic granulites, northeastern Alberta
Authors: Burwash R. A. , Krupicka J. , Basu A. R. , Wagner P. A.
Published: April 2011

At Mountain Rapids on the Slave River, mafic xenoliths are enclosed by a granodiorite host, which is, in turn, surrounded by a granitic migmatite complex. The mafic and granodioritic rocks are both metamorphosed to the hornblende granulite facies, and the migmatite has been metamorphosed to the upper amphibolite facies. The banding of the mafic granulites is truncated by sharply defined boundaries with the felsic granulites. The felsic granulites contain K-feldspar, the mafic rocks almost none. The mineral assemblages are otherwise identical: plagioclase–hypersthene–quartz–biotite–magnetite.A whole-rock Sm–Nd isochron of one felsic and six mafic granulites gives 2436 ± 44 Ma [Formula: see text]. This time is significantly younger than the Sm–Nd model ages. The same mafic samples give a Rb–Sr age of 1898 ± 5 Ma. These are interpreted as the times of reequilibration and closure of the Rb–Sr isotopic systems within the Mountain Rapids Granulite enclave. From cordierite–garnet barometry the indicated pressure of the younger event is 5.5 ± 0.7 kbar (550 ± 70 MPa). By analogy with hornblende granulite assemblages elsewhere, the older event probably occurred in the intermediate crust (~25–30 km depth). This event apparently effectively reset the Sm–Nd isotopic system; subsequent cooling closed it. Once established this system withstood the later, lower pressure event that reset the Rb–Sr geochronometer on a regional scale.
Provenance and sedimentary processes of ice-scoured surficial sediments, Labrador Shelf
Authors: Gilbert G. R. , Barrie J. V.
Published: April 2011

Sedimentological and geophysical studies of the surficial geology of the Labrador Shelf reveal evidence of sediment provenance and modern seabed dynamics. Analyses of lithic fragments of grab samples from southern Saglek Bank and Makkovik Bank indicate that a high proportion of the surficial cover is of ice-rafted origin. Fossilferous carbonate fragments of Paleozoic age suggest a northern Greenland or Arctic island provenance. Heavy-mineral analyses reveal minerals common to igneous and high-grade metamorphic rocks. The Precambrian terrains of Labrador are a possible early sediment source, although similar more northerly terrains could be more recent sources.The geologic environments of Saglek and Makkovik banks differ, as shown by sediment textures and the distribution and form of ice scours that are abundant over the Labrador Shelf. The contrasting environments result largely from differing degrees of postglacial sediment reworking, evidenced by mineral hydraulic equivalence of the sand fractions from both banks. Sediments on the Makkovik Bank undergo present-day transport as a result of a strong hydrodynamic regime. The deeper, broader Saglek Bank is a hydrodynamically quiet zone except near the seaward bank margin, where strong sediment reworking by currents has and is presently taking place.
A fossil fish of the family Saurichthyidae from the Lower Jurassic of western Alberta, Canada
Authors: Neuman Andrew G. , Wilson Mark V. H.
Published: April 2011

A partial skull of a fish belonging to the saurichthyid genus Acidorhynchus is reported from lower Toarcian black shales of the Fernie Group in western Alberta, Canada. This is the first North American record of the genus, which is otherwise known only from the Lower Jurassic of Europe. The synonymy and diagnostic features of the genus Acidorhynchus and its two included species are reviewed, and the new fossil is found to be most closely related to, and possibly conspecific with, the species A. acutus.
Heat flux measurements in southwestern British Columbia: the thermal consequences of plate tectonics
Authors: Lewis T. J. , Jessop A. M. , Judge A. S.
Published: April 2011

Measured heat fluxes from previously published data and 34 additional boreholes outline the terrestrial heat flow field in southern British Columbia. Combined with heat generation representative of the crust at 10 sites in the Intermontane and Omineca belts, the data define a heat flow province with a reduced heat flow of 63 mW m−2 and a depth scale of 10 km. Such a linear relationship is not found or expected in the Insular Belt and the western half of the Coast Plutonic Complex where low heat fluxes are interpreted to be the result of recent subduction. The apparent boundary between low and high heat flux is a transition over a distance of 20 km, located in Jervis Inlet 20–40 km seaward of the Pleistocene Garibaldi Volcanic Belt.The warm, thin crust of the Intermontane and Omenica Crystalline belts is similar to that of areas of the Basin and Range Province where the youngest volcanics are more than 17 Ma in age. Processes 50 Ma ago that completely heated the crust and upper mantle could theoretically produce such high heat fluxes by conductive cooling of the lithosphere. But it is more likely that the asthenosphere flows towards the subduction zone, bringing heat to the base of the lithosphere. Since the reduced heat flow is high but constant, large differences in upper crustal temperatures within this heat flow province at present are caused by large variations in both crustal heat generation and near-surface thermal conductivity. The sharp transition in heat flux near the coast is the result of the combined effects of convective heating of the eastern Coast Plutonic Complex, pronounced differential uplift and erosion across a boundary within the Coast Plutonic Complex, and the subducting oceanic plate.
Sedimentology and stratigraphy of the Cretaceous Virginian Ridge Formation, Methow Basin, Washington
Authors: Trexler Jr. James H.
Published: April 2011

The Cretaceous Methow Basin of north-central Washington is the southernmost of a series of Mesozoic successor basins in the Cordillera of western North America. The Albian–Campanian(?) Virginian Ridge Formation comprises three members, newly defined here, that gradationally interfinger with each other and grade laterally and upward into overlying strata. Detailed stratigraphic analysts of the Virginian Ridge Formation and of the intimately related parts of the Winthrop and Midnight Peak formations indicates that these units represent complexly interfingering facies derived from a variety of sources, both to the west and to the east of the basin and locally within the system. This study suggests a detailed model for the history of the Upper Cretaceous Methow Basin: generation of a restricted basin with a stable, roughly north–south-trending axis, filled by a stable, east-derived fluvial and deltaic system (Winthrop Formation) interfingering with a laterally amalgamated, west-derived northward and eastward transgressive fan-delta system (Virginian Ridge Formation). The sequence grades upward into, and finally is overwhelmed by, locally derived volcanics of the Midnight Peak Formation. Similar, and in part coeval, successor basin sequences throughout the North American Cordillera may have been generated in response to similar tectonic settings.
Foraminifera of a Joli Fou Shale equivalent in the Lower Cretaceous (Albian) Hasler Formation, northeastern British Columbia
Authors: Koke Kory R. , Stelck C. R.
Published: April 2011

The discovery of the arenaceous foraminifer Haplophragmoides gigas Cushman in the Hudson Hope area of northeastern British Columbia indicates that the Early Cretaceous (Albian) Joli Fou Sea flooded around the north side of the Peace River Arch, making an embayment that penetrated as far west as the Rocky Mountain Foothills. The microfauna of 25 genera and 46 species of arenaceous foraminifers is illustrated carrying Bathysiphon spp., Hippocrepina sp., Hyperammina spp., Lituotuba? sp., Psammosphaera spp., Reophax spp., Ammodiscus spp., Glomospira sp., Miliammina spp., Psamminopelta spp., Trochamminoides sp., Haplophragmoides spp., Ammomarginulina sp., Ammobaculites spp., Haplophragmium spp., Trochammina spp., Textulariopsis sp., Pseudobolivina spp., Plectorecurvoides sp., Verneuilina sp., Gaudryina sp., Uvigerinammina sp., Gravellina sp., and Eggerella sp.The suite occurs in the lower part of the Hasler Shale of the Fort St. John Group about 10–20 m above beds carrying a microfauna of the Ammobaculites wenonahae Subzone (= Stelckiceras liardense ammonite Zone) present in the basal portion of the Hasler Shale. The Haplophragmoides gigas Zone sensu stricto is overlain by a sequence of silty beds (Viking equivalent?), which in turn is succeeded by the Miliammina manitobensis Zone microfauna. The H. gigas assemblage has both boreal and southern aspects, suggesting a mixing of the waters from north and south as the first expression of the Colorado Sea in earliest late Albian time. The assemblage is a deep neritic one and lacks any calcareous component. Diagnostic megafauna are lacking.
Thermoluminescence dating applied to a thin winter varve of the late glacial South Thompson silt, south-central British Columbia
Authors: Berger G. W.
Published: April 2011

The partial bleach (R–Γ) procedure of thermoluminescence (TL) dating of unheated sediments has been applied to the 2–4 μm sized feldspar-dominated grains from two components of a 10–11 ka BP glaciolacustrine silt. A previous TL study of the 4–11 μm sized feldspars from a ~12 cm thick summer layer of this varved deposit did not produce the correct age. Here it is shown that the 2–4 μm feldspar grains from a contiguous, 5 mm thick clay-rich winter varve give a satisfactory TL apparent age of 14.2 ± 2.3 ka. On the other hand, and consistent with the previous results, the 2–4 μm feldspar grains from the thicker summer layer yield an incorrect high apparent age of 55 ± 13 ka. These results have implications for general TL dating of waterlaid sediments.
Temperature distributions at the Paleozoic and Precambrian surfaces and their implications for geothermal energy recovery in Alberta
Authors: Jones F. W. , Lam H.-L. , Majorowicz J. A.
Published: April 2011

A large number of bottom-hole temperature (BHT) data from Alberta (55 246 BHT from 28 260 wells) have been used to construct Paleozoic and Precambrian surface-temperature maps. A northward increase of average heat flow in Alberta results in higher subsurface temperatures at the Precambrian basement and at the top of the Paleozoic toward the north and northeast than at the same depths in the south and southeast. However, the temperature distribution at these surfaces is more depth dependent than gradient dependent, and so higher temperature values occur in the western part of the basin. As a result, good geothermal energy potential exists throughout the western half of the province, especially for regions west of the Calgary – Swan Hills – Grande Prairie – Rainbow Lake line. Through the central part of the basin, zones occur where the isotherms and the isopach lines of the Phanerozoic are parallel. These zones probably represent regions where little disturbance to heat transport by vertical water motion occurs. It is suggested that zones in the central part of the basin where such parallelism does not occur may represent areas where conductive transport of heat is perturbed by local, nonlateral fluid flow or zones with nonuniform heat contribution from the crystalline crust or upper mantle. The effect of hydrodynamics in the deeper sediments of the Paleozoic that lie below the BHT observations may also contribute to such zones.
Un mouvement glaciaire vers le nord-ouest dans la région de Saint-Godefroi, Gaspésie, Québec
Authors: Bail Pierre
Published: April 2011

The last glacial event in the Saint Godefroi area (Gaspé Peninsula) was a glacier from the southeast that was flowing towards the northwest before it stopped at the margin of the Saint Jogues Plateau. This interpretation is based on the following features: distribution of erratic boulders, till fabrics, a frontal moraine, and an outwash plain turned towards north. According to the study of the area located to the south of the Baie des Chaleurs, the glacier probably flowed at the beginning of the late Wisconsinan and disappeared before 14 000 years BP. [Journal Translation]
Uranium-bearing stratiform organic matter in paleoplacers of the lower Huronian Supergroup, Elliot Lake – Blind River region, Canada
Authors: Willingham Tylon O. , Nagy Bartholomew , Nagy Lois Anne , Krinsley David H. , Mossman David J.
Published: April 2011

The Elliot Lake – Blind River, Ontario, paleoplacer deposits in the basal Matineda Formation, lowermost member of the 2.25–2.45 Ga old Huronian Supergroup, contain organic matter chemically consistent with kerogen. This substance is also referred to as thucholite. Uranium ores and some gold occur here, and these minerals may be in close association with the kerogen. Two uraniferous and auriferous stratiform kerogens, obtained from the Denison Mines Limited's Denison mine and Rio Algom Limited's Stanleigh mine, have been analyzed by combined high-vacuum pyrolysis – gas chromatography – mass spectrometry and by neutron activation. The reflectances of these samples have also been determined. Related samples containing dispersed kerogen have been examined by backscattered scanning electron microscopy. The polymer-like matrix of the two stratiform kerogens consists of aromatic, alkyl aromatic hydrocarbon, and sulphur moieties and contains 20 and 32% uranium with gold abundances in the parts per billion range. The reflectances of the two stratiform kerogens are generally higher than those of the dispersed kerogens; the atomic H/C ratios of the former are −0.6 and −0.4. Backscattered scanning electron microscopy and petrographic observations reveal a complex diagenetic history. Stratigraphic position and supportive analytical data suggest that the stratiform kerogens were probably derived from ancient mats of cyanobacteria, subjected to various radiation-induced reactions, and, at least in part, were affected in a manner similar to the surrounding rocks. The latter experienced physical and chemical diagenetic reactions, which often caused repeated mineral fracturing and led to the local development of authigenic carbonates and feldspar. Some of the chemical nature and history of the stratiform kerogens resemble those of the Witwatersrand carbon seam kerogens.
Geochronology of the Big Spruce Lake alkaline intrusion
Authors: Cavell P. A. , Baadsgaard H.
Published: April 2011

A zircon age of [Formula: see text] has been determined for the silica-saturated syenites of the Big Spruce Lake alkaline complex. Pb–Pb whole-rock ages of [Formula: see text] and 2155 ± 16 Ma were obtained for the silica-undersaturated rocks of the complex and for the complex as a whole, respectively. The Sm–Nd whole-rock data yield an age of 2183 ± 75 Ma for the complex as a whole. By weighting the ages by the inverse square of the standard deviations, an average age for the complex of 2174 ± 20 Ma is determined. However, it is felt the zircon age is the most reliable for the time of crystallization of the complex. Minor contamination by country rock (Sm–Nd model ages of 2467–2595 Ma) and metasomatism contribute to scattered Sm–Nd data points and large errors in the ages obtained for the five individual units. The Pb–Pb data enable a limiting estimate of about 50 Ma for the maximum time span for the intrusion of centres 1–4.
Pollen stratigraphy of Eaglenest Lake, northeastern Alberta
Authors: Vance R. E.
Published: April 2011

Pollen analysis of a 7.65 m sediment core from Eaglenest Lake (57°46′N, 112°06′W) provides evidence of the postglacial development of vegetation in the mixedwood section of the Boreal Forest. From the time of deglaciation (approximately 12 000 – 11 500 years BP) to 11 000 BP the area was colonized by mainly nonarboreal flora dominated by Artemisia and Gramineae. Populus, the only tree taxon present, grew in sheltered areas, while Salix and Cyperaceae were common on poorly drained sites. Open parkland prevailed under a dry, windy climate. Summer temperatures were rising rapidly from glacial minima in response to increased solar insolation. By 11 000 BP Picea (initially P. glauca) and Betula (mainly tree Betula) migrated to the area. Forest prevailed, but the canopy was likely more open than at present. By 9000 BP peak warm and dry conditions had passed, although conditions warmer and drier than at present persisted. Alnus migrated to the area 8450 BP. Pinus reached the Birch Mountains about 7500 BP. No major changes in vegetation have occurred since that time, suggesting that modern climatic conditions were established by 7500 BP.
Ianthasaurus hardestii n. sp., a primitive edaphosaur (Reptilia, Pelycosauria) from the Upper Pennsylvanian Rock Lake Shale near Garnett, Kansas
Authors: Reisz Robert R. , Berman David S.
Published: April 2011

A new, small pelycosaur, Ianthasaurus hardestii, has been discovered in the well-known, richly fossiliferous locality in the Upper Pennsylvanian (Missourian) Stanton Formation, near Garnett, Kansas. It is represented by a partial, semi-articulated skeleton and scattered elements of at least three other individuals. The small, insectivorous Ianthasaurus possesses a number of primitive pelycosaurian features but also shares several derived characters with the large Early Permian herbivore Edaphosaurus, justifying its inclusion in the family Edaphosauridae and its recognition as the oldest and most primitive member of that group.
An alternative to exotic spore or pollen addition in quantitative microfossil studies
Authors: Ogden III J. Gordon
Published: April 2011

Uncertainties in availability and formulation of exotic microfossils (e.g., Lycopodium spp., Eucalyptus spp.) to be added to microfossil preparations may be resolved by the use of plastic microspheres (25.0 ± 1.0 μm), which are unaffected by standard pollen preparative treatments (KOH, HCl, HF, acetolysis, and organic solvents). The microspheres are sensitive to strongly oxidizing treatments (e.g., Schulze's reagent, H2O2: H2SO4 reflux for diatom preparation) but can be added following digestion of organic material.Preparation of microsphere suspensions in a suitable electrolyte (e.g., NaCl – formic acid – water) permits calibration by Coulter counter of suitable dilutions (e.g., 5000 ± 100 mL−1) for delivery by "Tipet" volumetric flasks.The uniformity and distinctive appearance of the microspheres not only facilitate recognition but also provide a constant reference for both size (25 μm) and volume 8180 μm3), as well as a reference standard for computerized microfossil scanning.The microspheres are inert (vinyl-coated styrene polymer), featureless, opaque, available in a variety of sizes, and of a density (SG = 1.3) similar to those of pollen grains.A stainless steel volumetric sediment sampler (0.5–5.0 cm3) that facilitates subsampling in core or bulk samples is described.
Palynostratigraphie et paléoenvironnements du Pléistocène supérieur dans la région du lac Bras d'Or, île du Cap-Breton, Nouvelle-Écosse
Authors: Vernal A. de , Mott R. J.
Published: April 2011

The East Bay and Castle Bay stratigraphic sections along the northeastern shore of Bras d'Or Lake, despite some discontinuities, represent an important part of the Upper Pleistocene. Pollen analysis of these deposits provides a record that can be subdivided into three main units: (1) The first unit reflects the spread of rich forests dominated by thermophilous species such as Quercus, Ostrya, and Pinus strobus. It indicates a warmer and certainly drier climate than the present one. Th/U ages of the order of 120 000 years support a correlation of unit I with the Sangamonian (sensu stricto) interglacial (substage 5 in oceanic climato-stratigraphy). (2) The lower part of unit II, characterized by Abies balsamea, Fagus grandifolia, Tsuga canadensis, and Pinus, reflects the predominance of a mixed forest in the regional landscape. A cool and humid climate, probably not dissimilar to that of present is inferred. Th/U ages of approximately 85 000 years permits correlation of this forest stage with a relatively warm interval of the last interglacial, probably substage 5a. The upper part of unit II reflects a cooler climate and is characterized by pollen assemblages of the coniferous species Abies balsamea and Picea. (3) The lower stratigraphic part of unit III represents the spreading of coniferous boreal forests dominated by Picea, Pinus, and Abies during a cooler interval than at present. An approximate Th/U age of 60 000 years was obtained. Unit III reflects several cycles interpreted as alternating successions of tundra–forest and coniferous boreal forest. It suggests minor climatic fluctuations during a relatively cold interval. The third polynostratigraphic unit covers a significant part of the middle Wisconsinan (stage 3).
Uncompressed specimens of Monograptus turriculatus (Barrande, 1850) from Cornwallis Island, Arctic Canada
Authors: Melchin M. J. , Lenz A. C.
Published: April 2011

Isolated specimens of Monograptus turriculatus (Barrande, 1850) have been recovered from calcite concretions of the turriculatus Zone (late Llandovery) from the Cape Phillips Formation, Canadian Arctic Islands. The sicula shows ventral as well as dextral lateral curvature, and the thecae show a pronounced lateral asymmetry. This asymmetry is manifest as a tear-shaped aperture, a long, laterally directed spine on the outer apertural margin, and a shorter, ventrally directed spine on the inner apertural margin. The latter spine is totally absent on the proximal thecae.Monograptus sedgwickii (Portlock, 1853) is suggested as a possible ancestor to M. turriculatus.
Anomalous paleomagnetism of the Crowsnest Formation of the Rocky Mountains
Authors: Irving E. , Wynne P. J. , Evans M. E. , Gough W.
Published: April 2011

The volcanic Crowsnest Formation of Albian age (late Early Cretaceous) from the Rocky Mountain fold and thrust belt of Alberta has a stable remanent magnetization with a mean direction of 349°, 59 °(α95 = 5°) and paleopole at 78°N, 108°E(dm = 7°, dp = 5°). The inclination is lower than, and the declination clockwise of, the expected mid-Cretaceous paleogeomagnetic field for cratonic North America. Taken at face value the result indicates that the Crowsnest Formation and the thrust sheet in which it occurs have been transported from the south relative to cratonic North America by 17 ± 6 °(about 1800 km) and rotated 24 ± 10° clockwise. It is also possible that flattening of inclination is caused by magnetic anistropy, but tests show this to be unlikely. A third possibility is that the magnetization is secondary and of latest Cretaceous age, but there are good reasons for believing this is not so. Lastly, it is possible that the unit could have been formed close to its present position relative to the craton but was deposited so quickly that the paleosecular variation was not adequately sampled, and the result is only a "spot" reading of the paleofield. The last is our preferred interpretation of the flattened inclination, but the clockwise deflection of the declination could reflect rotation. Other paleomagnetic data from the fold and thrust belt are generally consistent with the third interpretation.
Metamorphism of the Arseno Lake area, N.W.T., Canada: an Abukuma facies series of Aphebian age
Authors: Nielsen Peter A.
Published: April 2011

Progressive mineralogical and mineral–chemical changes are described for metapelitic rocks from an Abukuma-type metamorphic series ranging from greenschist to upper amphibolite – granulite facies in the Bear Structural Province, Northwest Territories, Canada.The first appearance of the following minerals defines six isograds: biotite; andalusite; cordierite (muscovite + chlorite out); sillimanite (andalusite out); sillimanite + K-feldspar (muscovite + quartz out); and almandine + K-feldspar ± cordierite (biotite + sillimanite + quartz out).Electron microprobe analyses of the Fe–Mg silicates, biotite, cordierite, and garnet, display two distinct trends of mineral chemistry with increasing metamorphic grade. In the almandine + K-feldspar ± cordierite zone, where garnet is present, Fe/(Fe + Mg) decreases in all of the Fe–Mg silicates observed. However, in the cordierite zone and in the higher grade rocks where garnet is absent, Fe/(Fe + Mg) increases in both biotite and cordierite. Ilmenite and rutile are involved in all continuous reactions and lead to increasing Fe/Mg with grade unless garnet is a product of reaction. There is also a displacement towards lower Fe content at the sillimanite + K-feldspar isograd.The scale of equilibration decreases to 1–2 mm in the almandine + K-feldspar ± cordierite zone, which is most probably a function of the decrease of [Formula: see text] and therefore [Formula: see text]in the metamorphic fluid with increasing metamorphic grade.The physical conditions of metamorphism in the Arseno Lake area range from [Formula: see text] at 2–2.5 kbar with[Formula: see text] in the chlorite zone to ≥650 °C at 3.5–4.0 kbar where [Formula: see text] in the almandine + K-feldspar ± cordierite zone.
Measuring glacier-motion fluctuations using a computer-controlled survey system
Authors: Clarke Garry K. C. , Meldrum Robert D. , Collins Sam G.
Published: April 2011

We describe a computer-controlled, distance-measuring system designed for glacier-motion surveys. A Sharp PC-1500 pocket computer is used to control an AGA Geodimeter 122 infrared laser ranger. Slope distance and vertical angle are automatically measured and plotted at preselected time intervals and recorded on magnetic tape. As a demonstration, three field experiments were performed on Trapridge Glacier, Yukon Territory. In the first experiment the position of a glacier flow marker was measured at 1 min intervals for 39 h. The average velocity (toward the instrument) was found to be 2.99 mm h−1. Subglacial water pressure was simultaneously measured at the flow marker site. For the duration of the survey, water pressure was low, and there is no clear relationship between pressure variations and glacier motion. In the second experiment the distance to a stationary target was measured at 1 min intervals for 9 h. The calculated motion of this target was −0.149 mm h−1, giving an indication of the magnitude of uncorrected distance errors. The third experiment lasted 35 h and again involved measurements of glacier flow. The calculated target motion was 1.80 mm h−1 toward the instrument.
Late Ordovician solitary rugose corals preserved in life position
Authors: Elias Robert J. , Buttler Caroline J.
Published: April 2011

Two Late Ordovician unattached solitary rugose corals from the Beaverfoot Formation in southeastern British Columbia were almost certainly preserved in life position. These unique specimens occur beneath large colonial corals and were thus shielded from high-energy events that overturned and transported other individuals. They confirm previous hypotheses that greatly curved solitary corals lay in the sediment with concave sides facing up and at least partly exposed, whereas slightly curved forms were oriented in more upright positions.
A new early Tremadoc (La1) graptolite faunule from western Newfoundland: its Australian affinity and biofacies relations
Authors: Erdtmann Bernd-D. , Botsford Jack W.
Published: April 2011

The biostratigraphic and depth-related ecostratigraphic significance of a newly discovered graptolite–phyllocarid faunule containing diminutive Rhabdinopora enigma and Anisograptus compactus of early to middle Tremadoc age from the Cooks Brook Formation (Humber Arm Supergroup) is described and discussed. The faunule is identical with the La1 (Lancefieldian) graptolite–phyllocarid-bearing black shale "band" of Victoria, Australia, which was until now only known from two or three outcrops in Victoria and a single bed in northern Norway. This graptolite faunule probably represents a very distal shelf-marginal or open-ocean correlative of the Cap des Rosiers (Quebec) and Green Point (Cow Head Group, Newfoundland) late early Tremadoc anisograptid graptolite biofacies realm.
Hydrochemical interpretation of groundwater flow systems in Quaternary sediments of southern Ontario
Authors: Howard K. W. F. , Beck P.
Published: April 2011

Shallow aquifer systems in surficial Quaternary sediments are geometrically complex, with highly variable hydraulic characteristics. Consequently these systems are extremely difficult to assess hydrogeologically using conventional investigation techniques and are often poorly understood. In a 500 km2 area of southern Ontario, hydrochemical techniques were used to investigate the hydraulic integrity and regional flow behaviour of 14 aquifer systems defined within 100 m of Quaternary overburden. This type of approach had been used successfully in more extensive bedrock aquifer systems but had not previously been applied on a regional scale to shallow Quaternary systems where sediment geochemistry and flow conditions are highly variable and rarely known. The study involved analysis of over 260 well waters for pH, major ions (Ca, Mg, Na, K, HCO3, Cl, and SO4) and subsidiary ions (NO3, I, Br, and F). Selected samples were analyzed for tritium.The groundwaters are classified into eight water types, two of which are sodium chloride in character and of bedrock origin. Of the remaining six, four are related by a chemical evolutionary sequence showing transition from a tritiated (> 30 TU), low-iodide (< 5 μg/L) CaHCO3 recharge water to an ion-exchanged, NaHCO3 water low in tritium (< 15 TU) and enriched in iodide (> 15 μg/L). The existence of this sequence implies a regional, composite flow system involving seven supposedly discrete aquifer systems.The two remaining water types are recent tritiated waters (> 20 TU) contaminated by road salt (Cl > 40 mg/L) and agricultural nitrate (NO3 > 10 mg/L). Together with the CaHCO3 waters these clearly delineate major areas of recharge and show that the covering of Halton Till is extensively permeable.
Geochemistry of the felsic metavolcanic rocks of the Wakeham Group: a metamorphosed peralkaline suite from the eastern Grenville Province, Quebec, Canada
Authors: Bourne James H.
Published: April 2011

The Wakeham Group is a suite of low-grade (greenschist facies) rocks located in the eastern Grenville Province. In order of volumetric importance, it consists of sandstones, acid volcanics, and gabbro dykes and sills. This report deals with the acid volcanic member of the group. Primary textural features have in large part been preserved. The minerals present include stilpnomelane, white mica, albite, titanite, and zircon. Calculations using 33 chemical analyses show that 29 of the compositions have normative corundum. The rocks would therefore appear to be predominantly peraluminous; however, incompatible trace-element data show affinities with other anorogenic, peralkaline suites. It is proposed that alkali loss, probably during the subsequent Grenvillian orogeny, imposed a peraluminous composition on originally peralkaline rocks. The Wakeham Group cannot be definitively correlated with other metavolcanic rocks found in the region.
Distribution of recent benthonic foraminifera near Sable Island, Nova Scotia
Authors: Medioli F. S. , Schafer C. T. , Scott D. B.
Published: April 2011

Sable Island is a 38 km long feature that is situated near the outer margin of the Scotian Shelf between George's Bank and the Laurentian Channel. Grab samples of the predominantly sandy substrate that surrounds the island's offshore areas were collected from water depths of 0 to ~55 m.Textural data indicate that winnowing processes are comparatively intense in offshore areas, especially on the north side of the island. A higher frequency of samples containing more than 2% clay-size particles occurs in an area lying off the southeastern coast of the island. The clay suggests that a pre-Recent source of fines is there or that wave energy conditions are somewhat reduced at this locality.Cluster analysis of foraminiferal percentage data defines several foraminiferal thanatotopes. The largest one is dominated by Eggerella advena, with large percentages of Elphidium and Trochammina. The second largest thanatotope is distinguished by its comparatively high porportion of miliolid species and by the highest mean percentage of E. advena.The offshore shelf environment around Sable Island appears to represent an area where several regional assemblage zones overlap. The factors controlling local assemblage distribution patterns in the shelf environment surrounding the island do not appear to be related directly to ambient water-mass characteristics. However, the occurrences of assemblages that include a large proportion of the lower estuarine – nearshore species E. advena may indicate the existence of an influx of groundwater from the island's aquifers to the surficial layer of offshore sediments.Foraminiferal barren zones are apparently related to resuspension and transport of tests to zones of reduced wave energy and to long-term effects of abrasion on the total indigenous thanatocoenoses.
The Hozameen fault system and related Coquihalla serpentine belt of southwestern British Columbia
Authors: Ray G. E.
Published: April 2011

The Hozameen Fault of southwestern British Columbia is associated with the Coquihalla serpentine belt and separates two distinct crustal units. Northeast of the fault are greenstones of the Early Triassic (?) Spider Peak Formation, which are unconformably overlain by Jurassic to Cretaceous turbidite and successor basin deposits of the Pasayten Trough. The oldest sedimentary rocks in the trough, the Ladner Group, contain a locally developed basal unit that hosts the Carolin mine gold orebody. Southwest of the fault, the Permian to Jurassic Hozameen Group represents a dismembered ophiolite succession comprising ultramafic rocks of the Petch Creek serpentine belt, overlain in turn by greenstone and chert units. The greenstones in the Hozameen Group and the Spider Peak Formation are geochemically distinguishable; the latter represent sodic, ocean-floor, subalkaline basalts formed in a spreading ridge environment, while the former include both arc tholeiites and oceanic island–seamount subalkaline basalts.Farther west, the major Petch Creek Fault separates the Hozameen Group from the Custer–Skagit Gneiss. This fault is locally associated with the Petch Creek serpentine belt and is considered to be a northern extension of the Ross Lake Fault of Washington State.The rocks in the Hozameen Group, Spider Peak Formation, and Pasayten Trough were probably deposited within a single basin that initiated as an extensive, multirifted, marginal back-arc basin and eventually evolved into the steadily narrowing Pasayten Trough.Following Early to Middle Cretaceous closure of the Pasayten Trough, oblique, easterly-directed movement along westerly-dipping thrusts caused the Custer–Skagit Gneiss to override the Hozameen Group, which in turn overrode rocks of the Pasayten Trough farther east; these boundary thrusts formed precursor structures for the Hozameen and Petch Creek faults. Ultramafic basement material underlying the Spider Peak Formation and the Hozameen Group was thrust up the bounding fractures, producing the Coquihalla and Petch Creek serpentine belts, respectively.Large-scale dextral transcurrent displacement, possibly related to movement along the Fraser Fault system, occurred subsequently along the Petch Creek and Hozameen faults. This wrench movement was preceded by the Mid-Eocene (?) intrusion of the Needle Peak pluton and was followed by emplacement of the 16–35 Ma Chilliwack batholith.
The axial skeleton of the Early Permian reptile Eocaptorhinus laticeps (Williston)
Authors: Dilkes David W. , Reisz Robert R.
Published: April 2011

Two articulated, partial vertebral columns of the Early Permian captorhinid Eocaptorkinus laticeps (Williston) exhibit the following serial changes in the axial skeleton: robust and unswollen neural arches on the First five presacrals gradually swell dorsally and laterally on presacrals 6–25; alternation of neural spine height of the presacrals with an interruption at presacral 9 is superimposed upon a gradual posterior decrease of spine height; slope of zygapophyseal articular surfaces changes from ventromedial on the first six presacrals to horizontal on the remaining presacrals; and spines for epaxial muscle attachment present on the neural arches of presacrals 6–14 decrease in size posteriorly. Midventral lips are present on the centra and intercentra of all presacrals. Fine cracks on the centra of caudal vertebrae 8–11 are evidence of caudal autotomy.The pattern of vertebral morphology suggests specializations in the cervical region for support of the massive head and in the dorsal region for increased lateral flexibility for locomotion and increased support of the rib cage and viscera.
The oldest chonetacean brachiopods (Ordovician–Silurian, Anticosti Island, Québec)
Authors: Racheboeuf Patrick R. , Copper Paul
Published: April 2011

Chonetes (Eodevonaria) primigenius Twenhofel 1914, from the Vaureal Formation (Ashgill: Richmondian) of Anticosti Island, is chosen as the type species for a new genus, Archeochonetes, the oldest chonetid brachiopod known. Specimens of Archeochonetes from the overlying Ellis Bay Formation (Ashgili: Gamachian, Himantian) are assigned to a new species, A. muirwoodae. A further, as yet unnamed, species of strophochonetid is also described and figured from the Silurian (Llandovery) Jupiter Formation. Detailed external and internal analysis of the shell reveals that the origin of Archeochonetes lies with the Strophomenacea, thus posing a new perspective to the problem of the mono- or polyphyletic origin of the chronetaceans.
Fission-track dating of the tectonic development of the San Juan Islands, Washington
Authors: Johnson Samuel Y. , Zimmermann Robert A. , Naeser Charles W. , Whetten John T.
Published: April 2011

The San Juan Islands of Washington State form a geologically complex province located between the north Cascades, Vancouver Island, and the Olympic Peninsula. We have obtained 53 fission-track dates from the San Juan Islands province that help constrain its late Paleozoic to early Cenozoic tectonic and sedimentary history and its relationship to neighboring geologic terranes. The San Juan Islands can be divided into two main blocks separated by the Haro fault. South of the Haro fault, complexly deformed, metamorphosed, and probably exotic early Paleozoic to early Late Cretaceous rocks form four imbricate thrust plates separated by south- and east-dipping late Early to Late Cretaceous thrust faults. Reset zircon fission-track dates indicate that thrusting may have produced an upside-down geothermal gradient in the uppermost plate, the Decatur terrane. If present, this gradient was probably produced by conductive or frictional heating associated with a now-eroded overlying thrust fault and hot thrust plate. Cretaceous thrusting in the southern San Juan Islands was accompanied by uplift and resetting of apatite fission-track dates. In contrast to correlative rocks of the southern San Juan Islands, Upper Triassic to Lower Cretaceous rocks in and north of the Haro fault zone are essentially unmetamorphosed and only broadly folded. Apatite dates from the Upper Triassic Haro Formation and the Upper Jurassic and Lower Cretaceous Spieden Group indicate they did not participate in Late Cretaceous uplift of the southern San Juan Islands. Together with their basement (the Wrangellia terrane?), these rocks probably acted as a backstop to thrusting. The synorogenic Late Cretaceous Nanaimo basin formed north of the Haro fault in front of the advancing San Juan Islands thrust system. The age of Nanaimo deposition matches uplift (apatite) dates in the southern San Juan Islands, and detrital zircons from the Nanaimo Group yield dates consistent with southern San Juan Islands sources. Burial led to resetting of apatite dates in what is probably the deeper part of the Nanaimo basin.