Atmosphere-ocean interaction and teleconnection in the Northern Pacific during the cold season     

Jiang Quanrong  J. M. Wallace 《海洋学报(英文版)》1992,11(4):537-546

On the basis of the idea in our work (Jiang and Wallace, 1991) , the horizontal structure of SST pattern, the atmospheric response to SST change and the atmospheric forcing of the ocean in the Northern Pacific during the cold season are discussed. The results show that PNA pattern is the most prominent normal mode in the atmosphere-ocean interaction in the Northern Pacific during the cold season.  相似文献   

A fine balance: Accommodation dominated control of contemporaneous cool-carbonate shelf-edge clinoforms and tropical reef-margin trajectories,North Carnarvon Basin,Northwestern Australia     

Ingrid Anell  Malcolm W. Wallace 《Sedimentology》2020,67(1):96-117

The concurrent development of a cool-carbonate Miocene clinoform system and the tropical reef which developed on its shelf in the North Carnarvon Basin is studied. The study, based on seismic interpretation and geometrical analysis, seeks to investigate how the architecture of the clinoforms develops in relation to the advance of the reef-margin, providing a proxy for discussing contemporaneous shoreline versus shelf-edge development. The progradation of the reef and shelf-edge often display a closely mirrored development, although the reef twice advances an order of two to three times the concurrent advance of the shelf-edge. The forced regression of the second advance, as compared to the normal regression during the first, is observed in proportionally higher input of sediment towards advance of the shelf-edge and toe, along with a gentler slope. The inability of the shelf-edge to keep pace with the reef-margin (and by proxy the shoreline) during lower accommodation/sedimentation is a result of the increased volume of sediment required to match reef-margin advance beyond the shelf-edge. Increased accommodation/sedimentation ratios promote higher trajectories where the volumes on shelf and slope are more balanced and the development more closely matched. The observed matched development of reef and shelf-edge during both limited and increased slope sedimentation, suggest that accommodation is the dominant control on the location and trajectory of both ‘shoreline’ and shelf-edge, and that excess sediment is deposited along the slope.  相似文献   

The thermal history of the intergalactic medium     

Joop Schaye  †  Tom Theuns  Michael Rauch  George Efstathiou  Wallace L.W. Sargent 《Monthly notices of the Royal Astronomical Society》2000,318(3):817-826

At redshifts z ≳2, most of the baryons reside in the smooth intergalactic medium which is responsible for the low column density Ly α forest. This photoheated gas follows a tight temperature–density relation which introduces a cut-off in the distribution of widths of the Ly α absorption lines ( b -parameters) as a function of column density. We have measured this cut-off in a sample of nine high-resolution, high signal-to-noise ratio quasar spectra and determined the thermal evolution of the intergalactic medium in the redshift range 2.0–4.5. At a redshift z ∼3, the temperature at the mean density shows a peak and the gas becomes nearly isothermal. We interpret this as evidence for the reionization of He  ii .  相似文献   

The volcanic environment for 40,000 years of human occupation on the Willaumez Isthmus,West New Britain,Papua New Guinea     

V.E. Neall  R.C. Wallace  R. Torrence 《Journal of Volcanology and Geothermal Research》2008

The stratigraphic sequence of 22 tephra beds and their associated paleosols at two sites selected from our studies in West New Britain, Papua New Guinea provide the essential environmental background for understanding human responses to c. 40 ka years of volcanic activity. Lithology, grain size, and mineralogy of the tephras, interpreted for the first time, elucidate the varying volcanic provenance, especially of the Pleistocene beds, and the environmental conditions which former inhabitants experienced.  相似文献   

Calculation of the composition of fractionated solid as deduced from chemical profiles in tholeiitic lava     

Wallace H. MacLean 《Contributions to Mineralogy and Petrology》2000,139(1):85-100

The composition of solid precipitated from cooling magma is calculated from chemical differentiation profiles and an incompatible element monitor of fractionation. In a period of cooling, magma evolves to a derivative liquid and a solid; liquid compositions are obtained from the chemical profiles, and the fractionation interval via the incompatible element and the Rayleigh distillation equation. The composition of the solid, the only unknown, can be calculated for both equilibrium and continuous fractionation models. A sequence of low-K tholeiitic laves (basalt to rhyolite) from an Archean greenstone belt in northwestern Quebec are used to describe the procedure. Chemical trends in the lava exhibit strong iron enrichment followed by depletion and evolution to rhyolite. Trends in the calculated solid are amplified relative to lava, and bulk distribution coefficients, normative minerals, mg-number, and other parameters also show significant divergence. Oxidation state and amount of “trapped liquid” have important effects on solid composition. Solids have notably more basic chemical compositions than coexisting liquids, and this produces a “lag” in differentiation indices between the two. The high values of bulk distribution coefficients calculated for Fe, Ti and P (D ∼ 3 to 4+) in late stages of fractionation make it possible to produce the extremely Fe–Ti–P-rich solid fractions in layered igneous complexes from quartz-normative liquids. Received: 28 June 1999 / Accepted: 13 December 1999  相似文献   

Hydraulic Characterization and Design of a Full-Scale Biocurtain   总被引：4，自引：0，他引：4  

David W. Hyndman  M.J. Dybas    L. Forney  R. Heine    T. Mayottee    M.S. Phanikumar  G. Tatara  J. Tiedje  T. Voice  R. Wallace  D. Wiggert  X. Zhao  C.S. Criddle 《Ground water》2000,38(3):462-474

  相似文献   

Pre-Cenozoic geology of the Latrobe Valley Area—onshore Gippsland Basin,S.E. Australia     

G. R. Holdgate  M. W. Wallace  S. Forbes 《Australian Journal of Earth Sciences》2013,60(6):695-716

In 2010–2011, a well on the uplifted northern edge of the Latrobe Valley (Yallourn North-1A) cored a 550 m section of mostly arenaceous sediments from the Lower Cretaceous Tyers River Subgroup. A follow-up core-hole (Yallourn Power-1) aimed at extending the Tyers River Subgroup section some 5 km south into the Latrobe Valley instead encountered Paleozoic basement rocks immediately below Cenozoic coal measures. From a re-examination of earlier coal and groundwater bore results, and new interpretations from gravity, seismic and magneto-telluric (MT) surveys, there is a significant area of Paleozoic basement rock that may underlie the whole northern Latrobe Valley area. The uplifted Yallourn North Lower Cretaceous sediments are a separate basin entity herein named the Monash trough. It appears they are separate from the main Lower Cretaceous Strzelecki Group Basin sediments on the southern side of the Latrobe Valley. Attributes of the Monash trough may underlie the main Strzelecki Basin, but this remains to be substantiated by further drilling. The intervening subcrop of Paleozoic basement rocks is herein named the Glengarry basement block. It shows characteristic gravity, MT and seismic features covering some 200 km² of the northern Latrobe Valley area. The boundary between the Glengarry basement block and Strzelecki Basin approximates to the Princes Highway. It is uncertain whether structural separation of the Monash trough from the main Strzelecki Basin always existed, or whether uplift and stripping of Cretaceous rocks over the Glengarry basement block occurred in post-Cretaceous but pre-Cenozoic times. Comparative rank and maturity indices indicate a greater depth of burial of the Glengarry basement block than what exists today, whereas less stripping and loss of section have occurred to the Monash trough. Cretaceous sediments of the Tyers River Subgroup (Rintouls Creek Formation, Tyers Conglomerate) in the Monash trough are dominated by mudstones, siltstones with lesser quartzose sandstones, conglomerates and thin coals. The sediments are over 300 m thick and are conformably overlain by 100 m of volcaniclastic sediments typical of the main Strzelecki Group, in turn overlain by nearly 100 m of Cenozoic coal measures. New detailed spore–pollen dating of Yallourn North-1A cores indicates that all Cretaceous sediments in the Monash trough are Barremian in age. This revises the traditional Neocomian age assigned to the formation. High total organic carbon levels in the 100 m-thick mudstones of the Locmany Member in the Rintouls Creek Formation constitute a mature petroleum source rock worthy of future hydrocarbon exploration.  相似文献   

Modelling hydrological connectivity of tropical floodplain wetlands via a combined natural and artificial stream network          下载免费PDF全文

Fazlul Karim  Anne Kinsey‐Henderson  Jim Wallace  Paul Godfrey  Angela H. Arthington  Richard G. Pearson 《水文研究》2014,28(23):5696-5710

The ecological condition and biodiversity values of floodplain wetlands are highly dependent on the hydrological connectivity of wetlands to adjacent rivers. This paper describes a method for quantifying connectivity between floodplain wetlands and the main rivers in a wet tropical catchment of northern Australia. We used a one‐dimensional hydrodynamic model to simulate time‐varying water depths across the stream network (i.e. rivers, streams and man‐made drains). The timing and duration of connectivity of seven wetlands (four natural and three artificial) with the two main rivers in the catchment were then calculated for different hydrological conditions. Location and areal extent of the wetlands and the stream network were identified using high‐resolution laser altimetry, and these data formed key inputs to the hydrodynamic model. The model was calibrated using measured water depths and discharges across the floodplain. An algorithm was developed to identify contiguous water bodies at daily time steps, and this gave the temporal history of connection and disconnection between wetlands and the rivers. Simulation results show that connectivity of individual wetlands to both rivers varies from 26 to 365 days during an average hydrological condition. Location, especially proximity to a main river, and wetland type (natural stream or artificial drain) were identified as key factors influencing these levels of connectivity. Some natural wetlands maintain connection with the river for most or all of the year, whereas the connectivity of some artificial wetlands varies from 26 to 36 days according to their patterns of network connection to adjacent rivers – a result that has important implications for the accessibility of these types of wetland to aquatic biota. Using readily available river gauge data, we also show how connectivity modelling can be used to identify periods when connectivity has fallen below critical thresholds for fish movement. These connectivity patterns within the floodplain network are central to the setting of river flows that will meet environmental requirements for biota that use floodplain wetlands during their life history. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

The filtering capacity of a tropical riverine wetland: I. Water balance     

David McJannet  Jim Wallace  Rex Keen  Aaron Hawdon  Joseph Kemei 《水文研究》2012,26(1):40-52

Wetlands in the coastal catchments adjacent to the Great Barrier Reef lagoon play an important role in local hydrological processes and provide important ecological habitats for terrestrial and aquatic species. Although many wetlands have been removed or degraded by agricultural expansion, there is now great interest in their protection and restoration as important aquatic ecosystems and potential filters of pollutant runoff. However, the filtering capacity of tropical wetlands is largely unknown, so the current study was established to quantify the water, sediment and nutrient balance of a natural riverine wetland in tropical north Queensland. Surface and groundwater fluxes of water, sediment and nutrients into and out of the wetland were monitored for a 3‐year period. This paper focuses on the water balance of this natural wetland and a companion paper presents its sediment and nutrient balance and estimates of water quality filtering. Wetland inflows and outflows were dominated by surface flows which varied by 3–4 orders of magnitude through the course of the year, with 90% of the annual flow occurring during the period January to March. Although groundwater inputs to the wetland were only 5% of the annual water balance, they are very important to sustaining the wetland during the dry season, when they can be the largest input of water (up to 90%). Water retention times in this type of wetland are very short, particularly when most of the flow and any associated materials are passing through it (i.e. 1–2 h), so there is little time to filter most of the annual flux of water through this wetland. Longer retention times occur at the end of the dry season (up to 8·5 days); but this is when the lowest fluxes of water pass through the wetland. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Thioarsenides: a case for long-range Lewis acid–base-directed van der Waals interactions     

G. V. Gibbs  A. F. Wallace  R. T. Downs  N. L. Ross  D. F. Cox  K. M. Rosso 《Physics and Chemistry of Minerals》2011,38(4):267-291

Electron density distributions, bond paths, Laplacian and local-energy density properties have been calculated for a number of As₄S _n (n = 3, 4 and 5) thioarsenide molecular crystals. On the basis of the distributions, the intramolecular As–S and As–As interactions classify as shared bonded interactions, and the intermolecular As–S, As–As and S–S interactions classify as closed-shell van der Waals (vdW) bonded interactions. The bulk of the intermolecular As–S bond paths link regions of locally concentrated electron density (Lewis-base regions) with aligned regions of locally depleted electron density (Lewis-acid regions) on adjacent molecules. The paths are comparable with intermolecular paths reported for several other molecular crystals that link aligned Lewis base and acid regions in a key–lock fashion, interactions that classified as long-range Lewis acid–base-directed vdW interactions. As the bulk of the intermolecular As–S bond paths (~70%) link Lewis acid–base regions on adjacent molecules, it appears that molecules adopt an arrangement that maximizes the number of As–S Lewis acid–base intermolecular bonded interactions. The maximization of the number of Lewis acid–base interactions appears to be connected with the close-packed array adopted by molecules: distorted cubic close-packed arrays are adopted for alacránite, pararealgar, uzonite, realgar and β-AsS and the distorted hexagonal close-packed arrays adopted by α- and β-dimorphite. A growth mechanism is proposed for thioarsenide molecular crystals from aqueous species that maximizes the number of long-range Lewis acid–base vdW As–S bonded interactions with the resulting directed bond paths structuralizing the molecules as a molecular crystal.  相似文献