Geomorphology of unique reefs on the western Canadian shelf: sponge reefs mapped by multibeam bathymetry     

Kim W. Conway  J. Vaughn Barrie  Manfred Krautter 《Geo-Marine Letters》2005,25(4):205-213

Multibeam imagery of siliceous sponge reefs (Hexactinellida, Hexactinosida) reveals the setting, form, and organization of five reef complexes on the western Canadian continental shelf. The reefs are built by framework skeleton sponges which trap clay-rich sediments resulting in a distinctive pattern of low intensity backscatter from the reefs that colonize more reflective glacial sediments of higher backscatter intensity. Bathymetry and backscatter maps show the distribution and form of reefs in two large complexes in the Queen Charlotte Basin (QCB) covering hundreds of km², and three smaller reef complexes in the Georgia Basin (GB). Ridges up to 7 km long and 21 m in height, together with diversely shaped, coalescing bioherms and biostromes form the principal reef shape in the QCB whereas chains of wave-form, streamlined mounds up to 14 m in height have developed in the GB. Reef initiation is dependent on the distribution of high backscatter-intensity relict glacial surfaces, and the variation in reef complex morphology is probably the result of tidally driven, near seabed currents.  相似文献   

Submersible observations of an iceberg pit and scour on the Grand Banks of Newfoundland     

J. V. Barrie  C. F. M. Lewis  D. R. Parrott  W. T. Collins 《Geo-Marine Letters》1992,12(1):1-6

An elongated sea bed depression (pit), 80 by 125 m and 10 m deep located on the Grand Banks of Newfoundland was identified on high resolution surficial geophysical survey lines and investigated using a manned submersible. The pit occurs at the termination of a long (greater than 3 km) iceberg scour, 1.5 m deep, and 80 m wide in 91 m of water. It is similar to other depressions in the region that indent the sea bed up to seven times deeper than the surrounding deepest iceberg furrows. The pit is interpreted to be the sea bed response to impact and loading by a rolling and grounding iceberg. The iceberg scour and pit appear to be of recent origin.  相似文献   

Global comparison of the regional rainfall results of enhanced greenhouse coupled and mixed layer ocean experiments: Implications for climate change scenario development     

Peter H. Whetton  Matthew H. England  Siobhan P. O'Farrell  Ian G. Watterson  A. Barrie Pittock 《Climatic change》1996,33(4):497-519

The extent of agreement amongst current global climate models (GCMs) on the global pattern of rainfall change simulated under enhanced greenhouse conditions is assessed. We consider the results of five experiments which use a simple mixed layer ocean formulation and five which use a fully dynamic ocean model (coupled experiments). For many regions of the northern hemisphere there is strong agreement amongst both mixed layer and coupled experiments on the sign of simulated rainfall change. However, in the southern hemisphere there are large, and apparently systematic, differences between the coupled and mixed layer experiments. In particular, whereas the mixed layer experiments agree on simulated rainfall increase in summer in the tropics and subtropics of the Australian sector, the coupled experiments agree (although more weakly) on rainfall decreases. These differences appear to relate to the much reduced warming simulated by the coupled experiments in the high latitudes of the southern hemisphere. However, recent oceanographie evidence suggests that this suppressed warming may be considerably overestimated. We conclude therefore that despite the in-principle advantages of coupled models, it may be too soon to base some regionally specific climate change scenarios solely on the results of coupled experiments.  相似文献   

The Port Mouton Shear Zone: intersection of a regional fault with a crystallizing granitoid pluton   总被引：2，自引：0，他引：2  

D. Barrie Clarke  Krista L. McCuish  Ron H. Vernon  Victor Maksaev  Brent V. Miller   《Lithos》2002,61(3-4):141-159

The peraluminous tonalite–monzogranite Port Mouton Pluton is a petrological, geochemical, structural, and geochronological anomaly among the many Late Devonian granitoid intrusions of the Meguma Lithotectonic Zone of southern Nova Scotia. The most remarkable structural feature of this pluton is a 4-km-wide zone of strongly foliated (040/subvertical) monzogranites culminating in a narrow (10–30 m), straight, zone of compositionally banded rocks that extends for at least 3 km along strike. The banded monzogranites consist of alternating melanocratic and leucocratic compositions that are complementary to the overall composition of that part of the pluton, suggesting an origin by mineral–melt and mineral–mineral sorting. Biotite and feldspar are strongly foliated in the plane of the compositional bands. These compositional variations and foliations originated by a process of segregation flow during shearing of the main magma with a crystallinity of 55–75%. Subsequent minor brittle fracturing of feldspars, twinning of microcline, development of blocky sub-grains in quartz, and kinking of micas demonstrate overprinting by a high-temperature deformation straddling the monzogranite solidus. Small folds and late sigmoidal dykes indicate dextral movement on the shear zone. This Port Mouton Shear Zone (PMSZ) is approximately co-linear with the only outcrops of Late Devonian mafic intrusions in the area, two of which are syn-plutonic with well-developed mingling textures in the marginal tonalite of the Port Mouton Pluton. Also closely co-linear with the mafic intrusions are a granitoid dyke that extends well beyond the outer contact of the Port Mouton Pluton, a swarm of large aligned angular xenolithic slabs, a zone of thin wispy schlieren banding, a large Be-bearing pegmatite, and a breccia pipe with abundant garnetiferous metapelitic xenoliths. In various ways, the shear zone may control all of these features. The Port Mouton Shear Zone is parallel to many other NE-trending faults and shear zones in the northern Appalachians, probably related to the docking of the Meguma Zone along the Cobequid–Chedabucto Fault system.  相似文献   

Earth-mass planets in exoplanetary systems     

Barrie W Jones 《Astronomy& Geophysics》2003,44(2):2.10-2.14

No exoplanets with masses anywhere near as small as that of the Earth have yet been found. Barrie Jones considers whether they could, nevertheless, exist.  相似文献   

Geology and Metal Contents of the Ruttan volcanogenic massive sulfide deposit, northern Manitoba, Canada     

C. Tucker. Barrie  Craig Taylor  Doreen E. Ames 《Mineralium Deposita》2005,39(8):795-812

The Paleoproterozoic Ruttan Cu–Zn volcanogenic massive-sulfide (VMS) deposit is a large, relatively low grade, bimodal-siliciclastic type deposit in the Rusty Lake volcanic belt of northern Manitoba. The deposit contained over 82.8 million tonnes of massive sulfide, of which 55.7 million tonnes were mined from 1973 to 2002. The deposit consists of a series of moderately to steeply dipping, south-facing lenses that extend along strike at the surface for 1.1 km and to a depth of 1.0 km. These lenses occur within a steeply dipping, bimodal volcanic, volcaniclastic and siliciclastic sequence. In the immediate mine area, transitional calc-alkalic to high-silica (tholeiitic), felsic, and intermediate volcanic/volcaniclastic rocks of the Mine Sequence are host to, and intercalated with, the massive-sulfide lenses. Transitional tholeiitic to calc-alkalic basalt and andesite are present in the footwall sequence, approximately 500 m down-section from the ore horizon. The overlying rocks are predominantly fine-grained volcaniclastics and siliciclastics, but include polyfragmental agglomerate that contains mafic bombs and scoriaceous felsic fragments. Syn-depositional felsic and mafic dikes, sills, and apophyses are ubiquitous throughout the Mine Sequence, including the ore lenses, indicating continued, near-vent magmatism, and volcanism during ore formation. Fabrics in altered hostrocks have consistent, down-plunge stretching lineations to the SSE that suggest the deposit has been elongated by a factor of ~1.2–1.5; otherwise, the deposit is remarkably undeformed. Syn- and post-depositional faults in the mine area have relatively minor displacements up to tens of meters. Proximal (within 200 m) footwall rocks exhibit moderate to strong chloritization, characterized by the upper greenschist to lower amphibolite facies assemblages that include cordierite–almandine–andalusite–sillimanite–biotite ± staurolite ± anthophyllite ± talc, and local silicification. The proximal hanging wall rocks are characterized by sericite ± gahnite alteration, which is restricted to within approximately 75 m of the uppermost lenses. Additional gangue minerals are anhydrite and carbonate minerals (siderite, dolomite, ankerite, and calcite), as well as chlorite, sericite, biotite, talc, and quartz. Carbonate (excluding siderite), potassium feldspar, silicification and epidotization are common distal alteration zones in the footwall to the Mine Sequence several kilometers to the northeast. There are three principal groups of massive sulfide lenses; the East lenses, the West lenses, and the Western Anomaly lenses to the far west. In general, Cu is relatively enriched at the stratigraphic base and in the center of the deposit, whereas Zn is enriched upsection and at the outer margins. Some of the Zn-rich ore exhibits primary mineralogical layering. Parts of the West and Western Anomaly lenses show two layers with Cu-rich bases and Zn-rich tops. The massive sulfide is typically 10–40-m thick; one area along the margin of the main lenses is over 130-m thick and may represent deposition adjacent to a syn-depositional fault. The main sulfide phases are pyrite, pyrrhotite, chalcopyrite, sphalerite, and galena, with tetrahedrite as the most abundant trace phase. Gahnite is ubiquitous in the chlorite-rich assemblages adjacent to the ore lenses. The average base, precious and trace metal contents estimated from Cu and Zn concentrates, and from millhead grades and recoveries. Metals easily transported as chloride and bisulfide complexes in hydrothermal fluids including: Pb, Ag, In, Cu, Cd, Au, and Zn are enriched by 1.5–2.5 orders of magnitude in comparison to the bulk continental crust. Other elements such as Sn, Mo, and As are at near-crustal concentrations, whereas Mn, Ga, and Co are significantly depleted in comparison to the crust. Calculated metal concentrations in the average hydrothermal fluid based on the average metal contents are comparable to, or higher than those measured at sediment covered ridge hydrothermal systems, which precipitate much of their metal budget in the subsurface. Average rare earth element contents for the sulfide are light rare earth element enriched (La_N/Yb_N=22) and range from 0.45 to 0.02x chondritic values, with a moderate negative Eu anomaly (Eu*=0.51). Metal and trace element contents in the Ruttan exhalite horizon, and in proximal (within 1–2 km) exhalites along strike from the 0.6 million tonne Dar-2 Cu–Zn deposit 12 km south of Ruttan, have positive Eu anomalies, whereas negative Eu anomalies are present at distance. The positive Eu anomalies reflect high temperature paleoseafloor hydrothermal venting and precipitation of Eu²⁺-enriched clays and possibly carbonates, and indicate proximity to base-metal deposits. Silver and lead are also enriched in the exhalites near the deposits, whereas Mn is enriched at ~1–3 km along strike, but not consistently. Editorial handling: B. Gemmel An erratum to this article is available at .  相似文献   

Characterization of dissolved organic matter across the Subtropical Convergence off the South Island,New Zealand     

Michael Gonsior  Barrie M. Peake  William T. Cooper  David C. Podgorski  Juliana D'Andrilli  Thorsten Dittmar  William J. Cooper 《Marine Chemistry》2011,123(1-4):99-110

Dissolved organic matter (DOM) was investigated along a gradient across the Subtropical Convergence (STC) off the South Island, New Zealand. Ultrahigh resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), excitation emission matrix fluorescence (EEM) spectroscopy, and molecular lignin analysis techniques were used to study this DOM. The analysis revealed a group of compounds found only in the coastal DOM samples, which were also characterized by an elevated terrestrial DOM fluorescence pattern and elevated lignin content if compared to the offshore samples. This group exhibited a high degree of carbon unsaturation, as evident from high double bond equivalence minus oxygen values (DBE-O > 9) and maximum fluorescence intensity. Sulfur-containing molecular formulae for summer DOM samples were much more abundant across the entire transect of the STC compared to winter and exhibited distinctly different hydrogen:carbon and oxygen:carbon elemental ratios, suggesting a possible correlation between biological activity and sulfur compounds. The molecular formulae common to all STC samples were compared with those calculated for DOM extracted from freshwater collected from a stream discharging into Doubtful Sound (West Coast, New Zealand). ESI-FT-ICR-MS measurements undertaken in negative electrospray ionization (ESI?) mode indicated that 30% of the molecular formulae were present in both types of DOM, while in positive ESI mode (ESI+) over 90% of the formulae were present in all samples. Hence, a significant portion of the molecular formulae assigned to the solid-phase extractable DOM pool (SPE-DOM) appear to be identical in oceanic and freshwater samples.  相似文献   

Pyrite—‘fool's gold’ or misunderstood mineral?     

Craig D. Barrie 《Geology Today》2010,26(1):28-33

Pyrite (FeS₂) is the most abundant sulphide mineral in the Earth's crust, and with its characteristic shape and appearance, is easily one of the most recognizable. Yet, pyrite has a somewhat tarnished reputation with many considering it to be waste material and of little economic importance, never-mind interest. This assessment however, is misleading and a considerable volume of current research focuses upon the unique characteristics and formation of pyrite. Indeed, with its potential for revealing the very foundations of life, as well as maximizing the discovery and exploitation of society's future metallic resources, pyrite may be of much greater interest and benefit than many geologists realize.  相似文献   

Process length variation of the cyst of the dinoflagellate Protoceratium reticulatum in the North Pacific and Baltic‐Skagerrak region: calibration as an annual density proxy and first evidence of pseudo‐cryptic speciation     

Kenneth Neil Mertens  Manuel Bringué  Nicolas Van Nieuwenhove  Yoshihito Takano  Vera Pospelova  Andre Rochon  Anne De Vernal  Taoufik Radi  Barrie Dale  R. Timothy Patterson  Kaarina Weckström  Elinor Andrén  Stephen Louwye  Kazumi Matsuoka 《第四纪科学杂志》2012,27(7):734-744

Process length variation of cysts of the dinoflagellate Protoceratium reticulatum (Claparède et Lachmann) Bütschli in surface sediments from the North Pacific was investigated. The average process length showed a significant inverse relation to annual seawater density: σ_{t annual} = ?0.8674 × average process length + 1029.3 (R² = 0.84), with a standard error of 0.78 kg m^?3. A sediment trap study from Effingham Inlet in British Columbia revealed the same relationship between average process length and local seawater density variations. In the Baltic–Skagerrak region, the average process length variation was related significantly to annual seawater density: σ_{t annual} = 3.5457 × average process length ? 993.28 (R² = 0.86), with a standard error of 3.09 kg m^?3. These calibrations cannot be reconciled, which accentuates the regional character of the calibrations. This can be related to variations in molecular data (small subunit, long subunit and internal transcribed spacer sequences), which show the presence of several genotypes and the occurrence of pseudo‐cryptic speciation within this species. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Monitoring,causality, and uncertainty in a stratospheric context     

A. Barrie Pittock 《Pure and Applied Geophysics》1980,118(1):643-660

Our increasingly complex understanding of stratospheric chemistry and transport processes leaves us with various theoretical possibilities of appreciable and perhaps serious environmental impact due to human activities. These possibilities raise policy questions in which the economic and other costs of regulating human activities must be weighed against the possible consequences of no such regulation. The natural variability of the atmosphere, the physical and other limitations on our global sampling and monitoring abilities, and the difficulties in establishing causal connections leave us in a state of uncertainty as to the reality and magnitude of at least some of these theoretical environmental impacts. Policy-makers must make decisions in the face of these uncertainties.The proper role of scientists as such in narrowing and quantifying the uncertainties is discussed, with particular regard to the evidence that cultural and other biases often affect individual scientists' conclusions. Conscious efforts are needed to minimize bias, quantify uncertainties, and speed up the process of scientific consensus-building. A careful distinction should be drawn between scientifically determined probabilities, and cost-benefit analyses which necessarily involve value judgments.  相似文献