bluuebunny/crossref_metadata_2025 huggingface dataset:
Tectonic setting of late Archean bimodal volcanism in the Michipicoten (Wawa) greenstone belt, Ontario
Authors: Sylvester Paul J. , Attoh Kodjo , Schulz Klaus J.
Published: February 2010

The tectono-stratigraphic relationships, depositional environments, rock associations, and major- and trace-element compositions of the late Archean (2744–2696 Ma) bimodal basalt–rhyolite volcanic rocks of the Michipicoten (Wawa) greenstone belt, Ontario, are compatible with an origin along a convergent plate margin that varied laterally from an immature island arc built on oceanic crust to a more mature arc underlain by continental crust. This environment is similar to that of the Cenozoic Taupo–Kermadec–Tonga volcanic zone. Michipicoten basaltic rocks, most of which are proximal deposits compositionally similar ([La/Yb]n = 0.63–1.18) to modern oceanic island-arc tholeiites, are interpreted as having formed along the largely submerged island arc. Voluminous Michipicoten rhyolitic pyroclastic rocks ([La/Yb]n = 4.3–18.7, Ybn = 5.7–15.9) probably erupted subaerially from the continental arc, with distal facies deposited subaqueously on the adjacent oceanic island arc and proximal facies deposited in subaerial and shallow subaqueous environments on, or along the flanks of, the continental arc. The compositional similarity between the lower (2744 Ma) and upper (2696 Ma) volcanic sequences of the belt suggests that this island- and continental-arc configuration existed for at least 45 Ma. The Michipicoten belt may be a remnant of a larger, laterally heterogeneous volcanic terrane that also included the Abitibi greenstone belt.
Geology of the Annieopsquotch Complex, southwest Newfoundland
Authors: Dunning G. R.
Published: February 2010

The Annieopsquotch Complex is an ophiolite that forms the Annieopsquotch Mountains of southwest Newfoundland. It contains rocks of the critical zone, gabbro zone (2.3 km thick), sheeted dyke zone (1.5 km thick), and pillow lava zone of a typical ophiolite. The zones trend northeast, face and dip southeast at approximately 50–70°, and are offset by faults.Cumulate rocks of the critical zone preserve graded layers, trough structures, and slump folds and locally are metamorphosed and deformed. The gabbro zone contains many textural varieties of gabbro, pegmatitic pods, layering, trondhjemite pods, and amphibolite near the base. It passes through a transition zone to a sheeted dyke zone that extends the full strike length of the ophiolite. Dykes trend northwest and are aphyric or plagioclase-phyric diabase. The pillow lava zone, besides pillow basalt, contains minor pillow breccia, hyaloclastite, and chert.The Annieopsquotch Complex is faulted against an Ordovician tonalite terrane to the northwest across the Lloyds River Fault and against the Victoria Lake Group to the southeast. It is cut by dykes and sills correlated with both these units. The complex is cut by two Late Ordovician gabbro–diorite intrusions and a granite of presumed Devonian age and is unconformably overlain by Early Silurian terrestrial sedimentary and volcanic rocks.Major-, trace-element, and clinopyroxene chemistry of the complex and other ophiolitic fragments between Buchans and King George IV Lake is typical of N-type MORB. These likely constituted one allochthon of Iapetus Ocean or marginal basin crust emplaced over the Ordovician continental margin of North America during the Taconic Orogeny.
The late Quaternary geomorphic and paleoclimatic history of the Cape Dyer area, easternmost Baffin Island, N.W.T.
Authors: Locke William W.
Published: February 2010

The Cape Dyer area of easternmost Baffin Island was isolated from the Laurentide Ice Sheet by the fiords of Cumberland Peninsula. Accordingly, the glacial chronology at Cape Dyer is that of local ice only and is indicative of the local climate throughout the late Quaternary. Six drift units, representing three periods of restricted glaciation and three of expanded glaciation, are present. Beyond the most distal drift is an area that has not been modified by glaciation.The expanded glaciations were dated through correlation on the bases of moraine morphology, soil development, and amino-acid racemization in marine mollusc shells incorporated in the drifts. No maximum age can be assigned to the earliest glaciation in the Cape Dyer area, but the last major glacial advance occurred about 70 000 years BP. The presence of extensive glaciofluvial features, faunal indicators of warm ocean water, and rapid soil development indicate that major glaciations of the Cape Dyer area accompanied winters warmer than at present but summers sufficiently cool to allow ice advance.The restricted ice advances were dated through correlation on the bases of moraine morphology, soil development, and lichen cover to the period between 9000 years BP and the present. They indicate ice extent similar to or less than at present throughout the past 60 000 years, in response to climatic conditions that were colder and dryer than the present until 9000 years BP, then slightly warmer than the present.Correlation with indicators of hemispheric and global climate indicates both in-phase and out-of-phase relationships. Glaciations at Cape Dyer are in phase with periods of high accumulation on Arctic ice caps, ice rafting of sediment in the Labrador Sea, and computed summer-insolation minima – winter-insolation maxima at 65°N latitude. This is as would be expected given the climatic interpretations of the drifts. Glaciation of the Cape Dyer area is out of phase with global ice volume as indicated by oxygen isotopes, suggesting the Antarctic dry valleys as a modem climatic analog for the Pleistocene eastern Canadian Arctic. The record of ice extent, climatic interpretations, and proposed model for climatic change are in agreement with most previously published reconstructions.
Chitinozoaires du Caradoc supérieur – Ashgill inférieur du Québec, Canada
Authors: Achab Aïcha
Published: February 2010

Chitinozoans from samples of the Trenton, Utica, and Lorraine groups of the St. Lawrence Lowlands are described.The studied assemblages contain well-known upper Caradocian and Ashgillian species and also new species, such as Conochitina pygmaea and Hercochitina cristata.The stratigraphic and geographic distribution of the microfossils allows identification of taxa with stratigraphic value.The assemblages so characterized also allow a link to be made between younger assemblages from the Ashgillian sequence of Anticosti Island, previously described by the author, and older ones described by Martin from Caradocian beds of the St. Lawrence Lowlands.
Secular variation of the Earth's magnetic field from 18.5 to 15.0 ka BP, as recorded in a Vancouver Island stalagmite
Authors: Latham A. G. , Schwarcz H. P. , Ford D. C.
Published: February 2010

A record of secular variation has been obtained from a stalagmite from Vancouver Island, British Columbia, Canada, covering the period 18.5–15.0 ka BP. The ages, obtained by the U–Th method, were not fully constrained because of the low U content of the sample. The record contributes to a regional type curve obtained from the sediments of Bessette Creek (31–19 ka BP), and to which it shows similar features. In particular, a 1600 year long signal of easterly bias and shallow inclinations is similar to three earlier such features, attributed by M. E. Evans to oscillating geomagnetic sources to the west of North America. The later part of the composite record correlates fairly well with other western North American lake records. There is no evidence for a geomagnetic excursion during this period for the western North American continent.
Polyphase late Paleozoic tectonothermal evolution of the southwestern Meguma Terrane, Nova Scotia: evidence from 40Ar/39Ar mineral ages
Authors: Dallmeyer R. D. , Keppie J. D.
Published: February 2010

40Ar/39Ar incremental-release ages of hornblende, muscovite, and biotite from a variety of granitic stocks and host metamorphic rocks suggest a complex late Paleozoic tectonothermal evolution for the southwestern Meguma Terrane. Regional D1 folding with cleavage formation under greenschist – lower amphibolite facies, M1 metamorphic conditions, occurred at ca. 400–410 Ma and was followed by emplacement of a series of granitic stocks ranging in age between ca. 375 and 315 Ma. These were emplaced at relatively shallow crustal levels and developed contact metamorphic aureoles of variable grade. These are locally superposed on M1 regional metamorphic assemblages and result in a complex isograd pattern. 40Ar/39Ar mineral ages suggest episodes of contact metamorphism occurred at (1) 360–375 Ma (possibly related to emplacement of the South Mountain Batholith or temporal equivalents), (2) 350–356 Ma around the Port Mouton Pluton and northeastern Shelburne Pluton, (3) ca. 315–325 Ma near the Wedgeport Pluton and in several other isolated localities, and (4) ca. 287 Ma along the northern margin of a large, low gravity anomaly located off the southwestern coast of Nova Scotia (inferred to reflect a subsurface pluton). Dextral shear deformation was locally associated with all of these thermal events. It is suggested that the Meguma Terrane experienced a similar stress system throughout the Late Devonian – Permian, with shear deformation localized in areas where increased temperatures resulted in decreased viscosity.
Structural history of the metamorphic sole of the Bay of Islands Complex, western Newfoundland
Authors: Fergusson C. L. , Cawood P. A.
Published: February 2010

Displacement of the Early Ordovician ophiolitic Bay of Islands Complex was accompanied by the development of a metamorphic sole in underlying accreted gabbro, mafic pillow lava, pelite, and psammite. The metamorphic sole contains up to 130 m of amphibolite, underlain by up to 80 m of mafic and pelitic–psammitic schist, which, in turn, overlies chlorite-bearing rocks that overlie mudstone-matrix mélange. A major foliation, locally mylonitic and (or) isoclinally folded, is pervasively developed in the greenschists and amphibolites. An extension lineation is widely developed and plunges north in amphibolite and trends east–west in greenschist, consistent with a changing direction of thrust transport from northerly to westerly as the mantle wedge cooled over time. Shear sense criteria in greenschist facies pelitic–psammitic schist indicate thrusting towards the west. In the southwestern Blow-Me-Down massif, two sets of folds postdate development of accretion-related S-L fabrics and resulted in a substantial widening of the metamorphic sole. Late disruption by foliation-parallel, low-angle extensional and steep faults have excised parts of the metamorphic sole, resulting in a marked discontinuity of units along strike. Extensional faults were induced by gravitational spreading as the Coulomb thrust wedge, containing the ophiolite, metamorphic sole, and underlying mélange unit, became supercritical. This was probably due to a combination of two factors: (1) development of a substantially weakened basal mélange layer and (2) lowering of the basal slope of the wedge as it was thrust over the Ordovician slope onto the shelf.
Structural evolution and tectonic significance of the Eastern Highlands shear zone in Cape Breton Island, the Canadian Appalachians
Authors: Lin Shoufa
Published: February 2010

The Eastern Highlands shear zone in Cape Breton Island of the Canadian Appalachians is characterized by an amphibolite-facies deformation zone over 5 km wide overprinted by a greenschist-facies mylonite zone about 1 km wide. Deformation zones in both metamorphic grades dip steeply to the southeast with movement direction pitching steeply to the southwest, and shear sense indicators indicate the same sense of shear, that is, an east-over-west dip-slip movement with minor sinistral strike-slip component. Deformation in both conditions is constrained to the Late Silurian to Early Devonian (mainly Late Silurian). It is suggested that the greenschist-facies deformation represents the last stage of a single episode of deformation that occurred initially under amphibolite-facies conditions. The west-vergent shearing along the shear zone is antithetic to the westward subduction that led to the Silurian continent-continent collision, which is interpreted by tectonic wedging in this part of the Canadian Appalachians.
Paleomagnetism of tills and associated paleosols in southwestern Alberta and northern Montana: evidence for Late Pliocene–Early Pleistocene glaciations
Authors: Cioppa M. T. , Karlstrom E. T. , Irving E. , Barendregt R. W.
Published: February 2010

Sequences of pre-Wisconsinan till and intercalated paleosols were sampled for paleomagnetic study. The tills were deposited during successive glaciations and the paleosols formed during interglacial intervals. Paleoargillic horizons of the paleosols and the carbonate cement (calcrete) found in some till–paleosol units generally yielded excellent data. Magnetizations of paleosols probably were acquired during the formation of the paleosols rather than during initial deposition of the tills in which they were developed. At Mokowan Butte (Alberta), the lowest paleosol has normal polarity, two of the middle tills have reversed polarity, and the uppermost till–paleosol unit has normal polarity. At Saint Mary Ridge (Montana), three of the lower tills have reversed polarity, and the upper two till–paleosol units have normal polarity. At Two Medicine Ridge (Montana), the lowest three tills are reversed, but the paleoargillic horizon on the uppermost (fourth) till is normal. Magnetostratigraphic correlation indicates that at least six glacial and six interglacial episodes are represented in the Kennedy Drift. The upper normal polarity units are interpreted as having been developed during the Brunhes Normal Chron, the underlying reversed polarity sediments during the Matuyama Reversed Chron, and the lowest normal polarity unit at Mokowan Butte during the Gauss Normal Chron. The oldest glaciations here extend into the Pliocene (2600 ka), making these sediments among the oldest glacial deposits in North America. Alternatively, the lowest normally magnetized paleosol at Mokowan Butte may have formed during either the Jaramillo or the Olduvai subchrons, although this is considered less likely.
Little Ice Age glacial activity in Peter Lougheed and Elk Lakes provincial parks, Canadian Rocky Mountains
Authors: Smith Daniel J. , Mccarthy Daniel P. , Colenutt Margaret E.
Published: February 2010

Dendrochronological, lichenometric, and 14C studies at 14 glacier sites in Peter Lougheed and Elk Lakes provincial parks were used to develop a chronology of Little Ice Age glacial events. The earliest indications of glacial activity are represented by moraines deposited prior to the 16th century. A major glacial expansion in the 17th century is recorded at three sites, where I4C dates show glaciers reached their maximum down-valley positions. Lichenometric dates and tree growth suppression records show a phase of glacial activity early in the 18th century, for which there is only sparse morainic evidence. Most moraines in the area date from a glacial advance culminating in the mid-19th century, and moraine formation was complete everywhere by the late 1800's. Recessional moraines are rare in the study area and indicate that ice-front retreat has been relatively continuous since the 19th century. The glacial chronology developed in this work is comparable to that reconstructed for both the Main Ranges of the Canadian Rockies and the Coast Ranges of the southern Cordillera.
The near-surface geology of St. Georges Bay, Nova Scotia: implications for the Hollow Fault
Authors: Durling P. , Howells K. , Harvey P.
Published: February 2010

A formline contour map, which depicts the near-surface, structural configuation of the strata underlying St. Georges Bay, northeastern Nova Scotia, was made from bedding attitude data compiled in the coastal areas; apparent dips measured from single-channel seismic reflection data; and true strikes and dips calculated at survey track intersections. The geology interpreted from the formline map is characterized by northeast-striking faults and fold axes. The folds in the bay comprise broad, open synclines and narrow, tightly folded or faulted anticlines. Gravity and deep seismic reflection data suggest that the faulted anticlines are intruded by salt. Correlations from offshore to onshore suggest that the structures mapped offshore in the bay extend onshore. The onshore extensions of the faulted anticlines are mapped as faults, and their antiformal nature is subdued. They are locally associated onshore with Carboniferous Windsor Group outcrop. The offshore extension of the Hollow Fault, which is interpreted as a major northeast-striking, Carboniferous strike-slip fault, was mapped as a 1500–2500 m wide deformation zone, using deep seismic reflection data. Gravity lows coincident with the deformation zone are interpreted as being caused by salt intrusions. The trend of the Hollow Fault Zone suggests that this fault complex (and its associated strike-slip movement) continues on land near Mabou, Cape Breton Island. However, it does not appear to continue offshore along the northwest coast of Cape Breton Island, as previously suggested.
Systematics and taxonomy of soft-shelled turtles (Family Trionychidae) from the Judith River Group (mid-Campanian) of North America
Authors: Gardner James D. , Russell Anthony P. , Brinkman Donald B.
Published: February 2010

Four valid species of trionychine trionychid turtles are recognized from the Upper Cretaceous (mid-Campanian; Judithian) Judith River Group, western North America. Cladistic analysis of extant and Judith River Group trionychines supports referral of three fossil species to Aspideretoides gen. nov. and one fossil species to Apalone, the genus of extant North American trionychines. The taxonomic diversity of Judith River Group trionychids is less than that of younger Maastrichtian and Paleocene assemblages from the Western Interior, largely because of the absence of plastomenine trionychids in the Judith River Group assemblage.
Tectonic and metamorphic events in the westernmost Grenville Province, central Ontario: new results from high-precision U–Pb zircon geochronology
Authors: Bussy F. , Krogh T. E. , Klemens W. P. , Schwerdtner W. M.
Published: February 2010

The U–Pb isotopic ages of metamorphic zircons from deformed amphibolitized metadiabase dykes and associated unstrained anatectic pegmatites have been determined to constrain the times of postdyke ductile flow related recrystallization and deformation. Samples from the Central Gneiss Belt of the Grenville Province in the southern Georgian Bay region provide a means of linking areas formed during common episodes of ductile flow. Three zircon fractions from one attenuated dyke in the Moon River domain gave identical concordant ages of 1062, 1065, and 1064 ± 2 Ma, while those from another gave identical concordant ages of 1052, 1051, and 1050 ± 2 Ma for the time of metamorphism. Zircons from a folded dyke from the Go Home domain gave identical concordant ages of 1049, 1047, and 1046 ± 2 Ma, while a single overgrowth fragment from an unstrained anatectic pegmatite in the fold hinge gave a concordant age of 1047 ± 2 Ma, as if folding, metamorphic zircon growth and postfolding pegmatite are part of the same process. An anatectic pegmatite in a metadiabase boudin neck in the Ahmic domain gave two zircon fractions with identical concordant ages of 1079 and 1080 ± 2 Ma that match the concordant 1078 ± 2 Ma age of a single overgrowth type grain from the host migmatite. Zircons from the metadiabase have similar but less precise ages due to a low level of uranium and a low abundance. U–Pb results for the Love Lake granite situated at the Parry Sound–Ahmic domain boundary are equivocal but may imply folding of this structure after 1068 Ma, the age of contained titanite. Either the upper or lower end of the ca. 1050–1372 Ma zircon discordia may correspond to granite emplacement. Zircons from a dyke that postdates a granulite-grade migmatization in the Parry Sound domain record a metamorphism at 1114 ± 2 Ma but older inherited grains are present in other fractions. Ductile flow in the Go Home and Moon River domains occurred in the interval 1047–1064 Ma during which the latter was probably emplaced, whereas earlier (1080 Ma) ductile flow in the Ahmic domain may relate to the time of overthrusting of the Parry Sound domain. Parry Sound domain dyke metamorphic ages imply a lack of post 1114 Ma migmatization, and a predyke migmatization consistent with a more exotic derivation of this domain. A [Formula: see text] Ma age for a postmigmatite crosscutting pegmatite dyke sets an upper limit on the age of a late buckling event in the Ahmic domain.
Geochemical and isotopic characteristics of Early Silurian clastic sequences in Antigonish Highlands, Nova Scotia, Canada: constraints on the accretion of Avalonia in the Appalachian – Caledonlde Orogen
Authors: Murphy J. Brendan , Keppie J. Duncan , Cude Mary Pat , Dostal Jarda , Waldron John W. F.
Published: February 2010

Avalonia is a terrane that accreted to Laurentia–Baltica during the development of the Appalachian–Caledonide Orogen. Interpretations of the timing of accretion have been constrained by comparing faunal affinities, overstep sequences, age and kinematics of inferred accretionary deformational events, and controversial paleomagnetic data. We show that the time of accretion of Avalonia may also be constrained by contrasts in the geochemical and isotopic signatures of its igneous rocks (which reflect the characteristics of the underlying continental basement and mantle) and sedimentary rocks (which reflect provenance). Early Silurian clastic sedimentary rocks of the Beechill Cove Formation, Antigonish Highlands, Nova Scotia, were deposited on Avalonian crust. The formation predominantly consists of approximately 80 m of siltstones and shales deposited in a nearshore environment and derived from the northeast. Their age is constrained by paleontological data and by directly underlying Late Ordovician – Early Silurian bimodal volcanic rocks that have typically Avalonian geochemical signatures. In comparison with typical Avalonian rocks, the Beechill Cove sediments are characterized by high SiO2, Ce/Yb, and initial 87Sr/86Sr, low Fe2O3, MgO, and TiO2, and strongly negative εNd(ur). These characteristics cannot be attributed to erosion of underlying Avalonian basement or coeval volcanic rocks and are consistent with derivation via significant transport from radiogenically enriched continental crust. εNd data are typical of Grenvillian basement compositions and suggest that the Beechill Cove sedimentary rocks were derived from an adjacent landmass with Grenvillian crust. The data, in conjunction with paleocontinental reconstructions and recent geochronological and structural data from the northern Appalachians, suggest that the Caledonide orogenic belt is the most likely source. Deposition of the Beechill Cove Formation is inferred to have occurred in an intracontinental basin associated with strike-slip tectonics during the oblique collision of the Avalon with Laurentia–Baltica.
Late Quaternary sea level history in the Paulatuk to Bathurst Inlet area, Northwest Territories
Authors: Kerr Daniel E.
Published: February 2010

The Paulatuk – Bathurst Inlet region experienced rapid deglaciation in response to marine incursion across isostatically depressed terrain during high relative sea level stands. Marine limits, frequently defined by ice-contact deltas, range from 10 m asl in the west to 228 m asl in the east and were formed from approximately 12.5 to 9 ka BP, respectively. Seven relative sea level curves demonstrate that the mainland coast has shown initial rapid emergence, then progressively less emergence, and finally submergence from Paulatuk to Bernard Harbour during the late Holocene. Regions to the east (Richardson Bay to Bathurst Inlet) continue to experience emergence. Sea level curves have shown persistently higher rebound from west to east. The pattern and magnitude of observed postglacial sea level changes are in accord with theoretical predictions. In areas outside the glacial limit, as well as close to but within the glacial limit, relative sea level initially falls during the early and middle Holocene, and then begins to rise due to the migration of the forebulge in late Holocene times. Submergence becomes progressively younger from west to east. Closer to the centre of ice loading, emergence has progressed since deglaciation.
Upper Lower Cambrian depositional sequence in Avalonian New Brunswick
Authors: Landing Ed , Westrop Stephen R.
Published: February 2010

The Hanford Brook Formation (emended) is a thin (up to 42+ m), upper Lower Cambrian depositional sequence that is unconformably bounded by the lower Lower Cambrian (Random Formation) and the middle Middle Cambrian (Fossil Brook Member of the Chamberlain's Brook Formation). These stratigraphic relationships of the trilobite-bearing Hanford Brook Formation indicate deposition on the Avalonian marginal platform in the Saint John, New Brunswick, region and provide more evidence for a uniform, latest Precambrian–Cambrian epeirogenic history and cover sequence in Avalon. The Hanford Brook Formation is a deepening–shoaling sequence with (i) lower, transgressive sandstone deposited in episodically high-energy environments (St. Martins Member, new); (ii) highstand–regressive, dysaerobic mudstone – fine-grained sandstone with volcanic ashes (Somerset Street Member, new); and (iii) upper, regressive, planar and hummocky cross-stratified sandstone (Long Island Member, new). Trilobites are common in the distal Somerset Street Member, and ostracodes and brachiopods dominate the St. Martins and Long Island members. Condensation of the St. Martins Member and absence of the Long Island Member where the Random Formation and Fossil Brook Member are thinnest suggest onlap of the Hanford Brook and pronounced, sub-Middle Cambrian erosion across epeirogenically active blocks in southern New Brunswick.
A new Palaeocene genus and species of percopsiform (Teleostei: Paracanthopterygii) from the Paskapoo Formation, Smoky Tower, Alberta
Authors: Murray Alison M. , Wilson Mark V. H.
Published: February 2010

A new genus and species of teleostean fish, Lateopisciculus turrifumosus (fossil taxon), from the Palaeocene Paskapoo Formation at Smoky Tower, Alberta, is described. This new species is classified in the Family Percopsidae (Paracanthopterygii: Percopsiformes), based on the presence of a dorsal process on the maxilla. The presence of this fish extends the earliest known age of this family from the Eocene (Amphiplaga and Erismatopterus (fossil taxa)) to the Late Palaeocene. The fossil assemblage at the Smoky Tower locality includes pike (Esocidae), an osteoglossomorph, and two salamanders as well as the new species of percopsid. The site was likely an oxbow lake or shallow swamp. A mass-death event is indicated by the multiple species and size- and age-class distribution of the specimens.
Hydrothermal alteration of volcanic rocks at the McLaughlin gold deposit, northern California
Authors: Sherlock Ross L.
Published: February 2010

The Plio-Pleistocene McLaughlin mine is a large hot-spring gold–silver–mercury deposit, located in the northern Coast Ranges of California. Two distinctly different suites of volcanic rocks host mineralization: an Upper Jurassic basalt, part of the Coast Range ophiolite; and an upper Cenozoic basaltic andesite, part of the Clear Lake Volcanic Field. The two suites of volcanic rocks range from least altered rocks showing primary igneous mineralogy, to intensely altered rocks composed of an assemblage of quartz, montmorillonite, sericite, and adularia. Mass balance calculations indicate almost total loss of Na, Ca, Mg, and Sr and large gains in Κ and Ba as a result of the hydrothermal alteration. The mass flux corresponds to the replacement of plagioclase feldspar with sericite and adularia, and mafic minerals with montmorillonite. Trace elements show no evidence for mobility. Rocks adjacent to the hydrothermal system have the greatest δ18O values and the highest calculated mass flux, suggesting the greatest degree of chemical exchange with the hydrothermal fluid. Rocks peripheral to the hydrothermal system have lower δ18O values that are a hybrid of primary magmatic values and values imposed by the hydrothermal alteration assemblage. These rocks also have calculated mass fluxes that reflect only partial exchange with the hydrothermal fluid.
Influences of principal stress direction and intermediate principal stress on the stress–strain–strength behaviour of completely decomposed granite
Authors: Kumruzzaman Md. , Yin Jian-Hua
Published: February 2010

The measurement and study of the stress–strain–strength behaviour of soils in general stress states involving the change of magnitudes and direction of the principal stresses are necessary and important. To investigate the strength behaviour under such conditions, consolidated undrained tests on remoulded hollow cylinder specimens of completely decomposed granite (CDG) were carried out using a hollow cylinder apparatus. Tests were conducted by maintaining a fixed principal stress direction with angle α from the vertical direction together with a fixed value of intermediate principal stress coefficient b. It is observed that the value of the friction angle decreases with an increase in α and the failure surface is anisotropic. There is an increase in friction angle with an increase in b value up to b = 0.25, and the friction angles are almost the same for b > 0.25. In addition, the behaviour of the soil in an undrained simple shear condition was examined. The simple shear condition is very near to the condition of α = 45° and b = 0.25. After having analyzed the test results of all hollow cylinder specimens, it was found that the strength anisotropy is very strong and is dependent on the principal stress direction and intermediate principal stress coefficient.
Description and numerical modelling of the October 2000 Nora debris flow, Northwestern Italian Alps
Authors: Pirulli Marina , Marco Federica
Published: February 2010

The Nora alluvial fan, which is located in the Orco River valley (Piedmont region, Italy), was affected by a debris flow of approximately 10 000 m3 in October 2000. The event was triggered by heavy rainfall that affected the whole Piedmont region at that time. The mobilization of the water-satured altered gneissic bedrock and colluvium in the upper zone of the Nora basin resulted in the detachment of a debris slide, which rapidly evolved into a channelized noncohesive debris flow. As information from post-event surveys and two pre-event digital elevation models (DEMs), with different resolutions, were available for the study site, the dynamics of the event has been numerically back-analyzed using the numerical code RASH3D. The obtained results have shown both the capability of the code to simulate the dynamics of a noncohesive debris flow, including the final deposit depth distribution, and the importance of on-site surveys and digital elevation model (DEM) resolution in interpreting numerical results and the associated calibrated rheological parameters.
Thrust and bending moment of rigid piles subjected to moving soil
Authors: Guo Wei Dong , Qin H. Y.
Published: February 2010

An experimental apparatus was developed to investigate the behaviour of vertically loaded free-head piles in sand undergoing lateral soil movement (wf). A large number of tests have been conducted to date. Presented here are 14 typical model pile tests concerning two diameters, two vertical pile loading levels, and varying sliding depths with the movement wfdriven by a triangular loading block. Results are provided for driving force as well as for induced shear force (T), bending moment (M), and deflection ( y) along the piles with wf/ normalized sliding depth. The tests enable simple expressions to be proposed, drawn from the theory for a laterally loaded pile. The new expressions well capture the evolution of M, T, and y with soil movement observed in current model tests, and the three to five times difference in maximum bending moment (Mmax) from the two modes of loading. They further offer a good estimate of Mmaxfor eight in situ pile tests and one centrifuge test pile. The study quantifies the sliding resistance offered by a pile for the given wfprofiles, pile location (relative to the boundary), and vertical load. It establishes the linear correlation between the maximum thrust (resistance T) and Mmax, regardless of the magnitudes of wf.
EVIDENCE FOR THE POSSIBLE EXISTENCE OF A LONG-LIVED SUPERHEAVY NUCLEUS WITH ATOMIC MASS NUMBER A = 292 AND ATOMIC NUMBER Z ≅ 122 IN NATURAL Th
Authors: MARINOV A. , RODUSHKIN I. , KOLB D. , PAPE A. , KASHIV Y. , BRANDT R. , GENTRY R. V. , MILLER H. W.
Published: February 2010

Evidence for the possible existence of a superheavy nucleus with atomic mass number A = 292 and abundance of about 1×10-12 relative to 232 Th has been found in a study of natural Th using inductively coupled plasma-sector field mass spectrometry. The measured mass is different from any species with molecular mass of 292, but it matches the predictions for the mass of an isotope with atomic number Z = 122 or a nearby element. Its deduced half-life of t1/2 ≥ 108 y suggests that a long-lived isomeric state exists in this isotope. The possibility that it might belong to a new class of long-lived high spin super- and hyperdeformed isomeric states is discussed.
THE SOLUTION OF THE SECOND PÖSCHL–TELLER LIKE POTENTIAL BY NIKIFOROV–UVAROV METHOD
Authors: MIRANDA M. G. , SUN GUO-HUA , DONG SHI-HAI
Published: February 2010

The bound states of the Schrödinger equation for a second Pöschl–Teller like potential are obtained exactly using the Nikiforov–Uvarov method. It is found that the solutions can be explicitly expressed in terms of the Jacobi functions or hypergeometric functions. The complicated normalized wavefunctions are found.
PERFORMANCE DIAGRAMS FOR CERAMIC MATRIX COMPOSITE COMPONENTS SUBJECTED TO CYCLIC THERMO-MECHANICAL LOADING
Authors: COCKS A. C. F. , LECKIE F. A.
Published: February 2010

Ceramic matrix composites (CMCs) are candidates for pressurized tubes which operate under conditions of severe cyclic thermal loading. Simple models describing the properties of CMCs are used to estimate the behaviour of a pressurized tube subjected to cyclic thermal loading and to establish shakedown and failure conditions. Analytical procedures are described which evaluate the component response in the cyclic state. The approach is illustrated by analysing the classical Bree problem assuming material properties which are representative of a SiC/SiC composite. Performance diagrams are presented which identify safe operating conditions and the extent of damage in the component.
EVALUATION OF DAMAGE DEVELOPMENT IN STEELS SUBJECTED TO PRIOR DEFORMATION: DESTRUCTIVE AND NONDESTRUCTIVE TECHNIQUES
Authors: KOWALEWSKI ZBIGNIEW L. , MACKIEWICZ SŁAWOMIR , SZELĄŻEK JACEK , PIETRZAK KRYSTYNA , AUGUSTYNIAK BOLESŁAW
Published: February 2010

Creep damage due to constant loading at elevated temperatures and damage due to plastic deformation at room temperature are assessed using destructive and nondestructive methods in steels (40HNMA and P91). In the destructive methods the standard tension tests were carried out after prestraining and variations of the selected tension parameters were taken into account for damage identification. In order to assess damage development during the creep and plastic deformation the tests for both steels were interrupted for a range of selected strain magnitudes. Ultrasonic and magnetic techniques were used as the nondestructive methods for damage evaluation. The last step of the experimental programme contained microscopic observations. The results show that ultrasonic and magnetic parameters can be good indicators of material degradation and can help to locate the regions where material properties are changed due to prestraining. A good correlation of mechanical and selected nondestructive parameters identifying damage was achieved for both tested steels.
Apical Recycling of the Gastric Parietal Cell H,K-ATPase
Authors: Forte John G. , Zhu Lixin
Published: February 2010

The gastric parietal cell was the first system where a regulated membrane recycling hypothesis was proposed as the principal means for moving molecular transporters between cellular compartments. Upon stimulation, massive membrane flow from an endosomal compartment of tubulovesicle membranes to the apical secretory surface places the ATP-driven pumps in position to secrete a solution of strong acid in collaboration with several other membrane transporters. This review focuses on the membrane recycling pathway and proteins that support the recruitment and redistribution of H,K-ATPase-rich membranes, including those involved in signal transduction, membrane targeting, docking, and fusing, in addition to the integral role of the actin cytoskeleton and its associated proteins in the process of membrane recycling. Although much of the evidence discussed here comes from parietal cell studies, other physiological transport systems, as well as less complex cellular and in vitro models, are examined and cited for generality of principle.
Autophagy During Cardiac Stress: Joys and Frustrations of Autophagy
Authors: Gottlieb Roberta A. , Mentzer Robert M.
Published: February 2010

The study of autophagy has been transformed by the cloning of most genes in the pathway and the introduction of GFP-LC3 as a reporter to allow visual assessment of autophagy. The field of cardiac biology is not alone in attempting to understand the implications of autophagy. The purpose of this review is to address some of the controversies and conundrums associated with the evolving studies of autophagy in the heart. Autophagy is a cellular process involving a complex orchestration of regulatory gene products as well as machinery for assembly, selective targeting, and degradation of autophagosomes and their contents. Our understanding of the role of autophagy in human disease is rapidly evolving as investigators examine the process in different tissues and different pathophysiological contexts. In the field of heart disease, autophagy has been examined in the settings of ischemia and reperfusion, preconditioning, cardiac hypertrophy, and heart failure. This review addresses the role of autophagy in cardioprotection, the balance of catabolism and anabolism, the concept of mitochondrial quality control, and the implications of impaired autophagic flux or frustrated autophagy.
Intrarenal Purinergic Signaling in the Control of Renal Tubular Transport
Authors: Praetorius Helle A. , Leipziger Jens
Published: February 2010

Renal tubular epithelial cells receive hormonal input that regulates volume and electrolyte homeostasis. In addition, numerous intrarenal, local signaling agonists have appeared on the stage of renal physiology. One such system is that of intrarenal purinergic signaling. This system involves all the elements necessary for agonist-mediated intercellular communication. ATP is released from epithelial cells, which activates P2 receptors in the apical and basolateral membrane and thereby modulates tubular transport. Termination of the signal is conducted via the breakdown of ATP to adenosine. Recent far-reaching advances indicate that ATP is often used as a local transmitter for classical sensory transduction. This transmission apparently also applies to sensory functions in the kidney. Locally released ATP is involved in sensing of renal tubular flow or in detecting the distal tubular load of NaCl at the macula densa. This review describes the relevant aspects of local, intrarenal purinergic signaling and outlines its integrative concepts.
Genomic Analyses of Hormone Signaling and Gene Regulation
Authors: Cheung Edwin , Kraus W. Lee
Published: February 2010

Many cellular signaling pathways ultimately control specific patterns of gene expression in the nucleus through a variety of signal-regulated transcription factors (TFs), including nuclear hormone receptors (NRs). The advent of genomic technologies for examining signal-regulated transcriptional responses and TF binding on a genomic scale has dramatically increased our understanding of the cellular programs that control hormonal signaling and gene regulation. Studies of TFs, especially NRs, using genomic approaches have revealed novel and unexpected features of hormone-regulated transcription, and a global view is beginning to emerge. In this review, we discuss the genomic methodologies that have been applied to the study of hormone-regulated gene expression, the results that have been obtained from using them, and the future prospects for these approaches. Given the wealth of information about hormone-dependent gene regulation by NRs, we have focused this review on the knowledge gained from genomic studies of their function.
Macrophages, Inflammation, and Insulin Resistance
Authors: Olefsky Jerrold M. , Glass Christopher K.
Published: February 2010

Obesity induces an insulin-resistant state in adipose tissue, liver, and muscle and is a strong risk factor for the development of type 2 diabetes mellitus. Insulin resistance in the setting of obesity results from a combination of altered functions of insulin target cells and the accumulation of macrophages that secrete proinflammatory mediators. At the molecular level, insulin resistance is promoted by a transition in macrophage polarization from an alternative M2 activation state maintained by STAT6 and PPARs to a classical M1 activation state driven by NF-κB, AP1, and other signal-dependent transcription factors that play crucial roles in innate immunity. Strategies focused on inhibiting the inflammation/insulin resistance axis that otherwise preserve essential innate immune functions may hold promise for therapeutic intervention.
It's Not All Smooth Muscle: Non-Smooth-Muscle Elements in Control of Resistance to Airflow
Authors: Bossé Ynuk , Riesenfeld Erik P. , Paré Peter D. , Irvin Charles G.
Published: February 2010

To achieve gas exchange, inspired air must pass through an intricate and dynamic tracheobronchial tree. The tree offers resistance to airflow, and increased resistance is the most important functional change in lung disease. Numerous mechanisms contribute to increased resistance by causing airway narrowing, closure, occlusion, and/or obliteration. Although airway smooth muscle (ASM) contraction and shortening are an important cause of increased resistance, non-ASM elements can also contribute. Nonmuscle elements can modify the amount of airway narrowing for any given level of ASM shortening and the amount of shortening for a given level of ASM activation. In this review, we outline the physiological basis for airflow resistance and describe how changes in the lung parenchyma, the airways, and their luminal contents can contribute to increased airflow resistance. A detailed understanding of the mechanisms and consequences of increased airway resistance is vital to our attempts to alleviate the enormous burden of suffering caused by obstructive lung diseases.
Living in the Now: Physiological Mechanisms to Tolerate a Rapidly Changing Environment
Authors: Hofmann Gretchen E. , Todgham Anne E.
Published: February 2010

Rising atmospheric carbon dioxide has resulted in scientific projections of changes in global temperatures, climate in general, and surface seawater chemistry. Although the consequences to ecosystems and communities of metazoans are only beginning to be revealed, a key to forecasting expected changes in animal communities is an understanding of species' vulnerability to a changing environment. For example, environmental stressors may affect a particular species by driving that organism outside a tolerance window, by altering the costs of metabolic processes under the new conditions, or by changing patterns of development and reproduction. Implicit in all these examples is the foundational understanding of physiological mechanisms and how a particular environmental driver (e.g., temperature and ocean acidification) will be transduced through the animal to alter tolerances and performance. In this review, we highlight examples of mechanisms, focusing on those underlying physiological plasticity, that operate in contemporary organisms as a means to consider physiological responses that are available to organisms in the future.
Inducible Innate Resistance of Lung Epithelium to Infection
Authors: Evans Scott E. , Xu Yi , Tuvim Michael J. , Dickey Burton F.
Published: February 2010

Most studies of innate immunity have focused on leukocytes such as neutrophils, macrophages, and natural killer cells. However, epithelial cells play key roles in innate defenses that include providing a mechanical barrier to microbial entry, signaling to leukocytes, and directly killing pathogens. Importantly, all these defenses are highly inducible in response to the sensing of microbial and host products. In healthy lungs, the level of innate immune epithelial function is low at baseline. This is indicated by low levels of spontaneous microbial killing and cytokine release, reflecting low constitutive stimulation in the nearly sterile lower respiratory tract when mucociliary clearance mechanisms are functioning effectively. This contrasts with the colon, where bacteria are continuously present and epithelial cells are constitutively activated. Although the surface area of the lungs presents a large target for microbial invasion, activated lung epithelial cells that are closely apposed to deposited pathogens are ideally positioned for microbial killing.
Structural Overview of the Nuclear Receptor Superfamily: Insights into Physiology and Therapeutics
Authors: Huang Pengxiang , Chandra Vikas , Rastinejad Fraydoon
Published: February 2010

As ligand-regulated transcription factors, the nuclear hormone receptors are nearly ideal drug targets, with internal pockets that bind to hydrophobic, drug-like molecules and well-characterized ligand-induced conformational changes that recruit transcriptional coregulators to promoter elements. Yet, due to the multitude of genes under the control of a single receptor, the major challenge has been the identification of ligands with gene-selective actions, impacting disease outcomes through a narrow subset of target genes and not across their entire gene-regulatory repertoire. Here, we summarize the concepts and work to date underlying the development of steroidal and nonsteroidal receptor ligands, including the use of crystal structures, high-throughput screens, and rational design approaches for finding useful therapeutic molecules. Difficulties in finding selective receptor modulators require a more complete understanding of receptor interdomain communications, posttranslational modifications, and receptor-protein interactions that could be exploited for target gene selectivity.
Suprachiasmatic Nucleus: Cell Autonomy and Network Properties
Authors: Welsh David K. , Takahashi Joseph S. , Kay Steve A.
Published: February 2010

The suprachiasmatic nucleus (SCN) is the primary circadian pacemaker in mammals. Individual SCN neurons in dispersed culture can generate independent circadian oscillations of clock gene expression and neuronal firing. However, SCN rhythmicity depends on sufficient membrane depolarization and levels of intracellular calcium and cAMP. In the intact SCN, cellular oscillations are synchronized and reinforced by rhythmic synaptic input from other cells, resulting in a reproducible topographic pattern of distinct phases and amplitudes specified by SCN circuit organization. The SCN network synchronizes its component cellular oscillators, reinforces their oscillations, responds to light input by altering their phase distribution, increases their robustness to genetic perturbations, and enhances their precision. Thus, even though individual SCN neurons can be cell-autonomous circadian oscillators, neuronal network properties are integral to normal function of the SCN.