Décollement folds in Redbank area,northern territory     

Emile Rod 《Australian Journal of Earth Sciences》2013,60(1-2):89-95

The structural deformation which produced more than 80 Jura‐type folds each of an axial length exceeding 1 km, in the Redbank Area, N.T., involved only a 360‐to 400‐m thick blanket of sediments. This thin skin of sediments and volcanic rocks, belonging to the Lower Proterozoic Tawallah Group, consists from bottom to top of the Wollogorang Formation, Gold Creek Volcanics, and Pungalina beds. Folding did not involve the underlying Settlement Creek Volcanics or Aquarium Formation. It is postulated that the cause of this detachment and shearing off along the bottom of the thin blanket of sediments is the infiltration of carbonated, K‐rich hydrothermal fluids under high pressure. This occurred during a period of igneous activity related to a postulated deep‐seated alkaline magma thought to be responsible for the many breccia pipes in the area. Thus the folds result from a décollement triggered by high fluid pressure, and from the accompanying gravity gliding and gravitational induced deformation of the thin skin of sediments along a gentle slope.  相似文献   

The spatial and temporal patterns of aggradation in a temperate,upland, gravel‐bed river     

Emma K. Raven  Stuart N. Lane  Rob I. Ferguson  Louise J. Bracken 《地球表面变化过程与地形》2009,34(9):1181-1197

Intensive field monitoring of a reach of upland gravel‐bed river illustrates the temporal and spatial variability of in‐channel sedimentation. Over the six‐year monitoring period, the mean bed level in the channel has risen by 0·17 m with a maximum bed level rise of 0·5 m noted at one location over a five month winter period. These rapid levels of aggradation have a profound impact on the number and duration of overbank flows with flood frequency increasing on average 2·6 times and overbank flow time increasing by 12·8 hours. This work raises the profile of coarse sediment transfer in the design and operation of river management, specifically engineering schemes. It emphasizes the need for the implementation of strategic monitoring programmes before engineering work occurs to identify zones where aggradation is likely to be problematic. Exploration of the sediment supply and transfer system can explain patterns of channel sedimentation. The complex spatial, seasonal and annual variability in sediment supply and transfer raise uncertainties into the system's response to potential changes in climate and land‐use. Thus, there is a demand for schemes that monitor coarse sediment transfer and channel response. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Redistribution of sewage-nitrogen in estuarine food webs following sewage treatment upgrades     

Kylie A. Pitt  Rod M. Connolly 《Marine pollution bulletin》2009,58(4):573-580

Stable nitrogen isotopes were used to assess the effects of wastewater treatment plant (WWTP) upgrades on the utilisation of sewage-N by estuarine biota in Moreton Bay, Australia. We measured δ¹⁵N of filamentous algae, mangrove leaves and shore crabs at the Brisbane and Logan Rivers before and after scheduled WWTP upgrades, and at two reference rivers where WWTPs had been upgraded >4 years previously. The total N discharged into Brisbane River decreased by >80% after the upgrades had occurred, but N loads remained similar at Logan River despite the upgrade. In Brisbane River, δ¹⁵N values of algae and crabs decreased and were comparable to the reference rivers within 1-2 years but no changes occurred at Logan River. The δ¹⁵N of mangrove leaves remained elevated in all rivers, indicating that sewage-N remained a major source to mangroves either from residual WWTP discharges or from N accumulated in the sediments over many years.  相似文献   

Lithium depletion in the brown dwarf binary GJ 569Bab     

M. R. Zapatero Osorio  E. L. Martín  B. F. Lane  Ya. Pavlenko  H. Bouy  I. Baraffe  G. Basri 《Astronomische Nachrichten》2005,326(10):848-851

GJ 569Bab is the first brown dwarf binary for which the mass of each component has been derived by solving the astrometric and spectroscopic orbit of the pair, i.e., independently of any theoretical assumption. This allows us to test the predictions of the various evolutionary models available in the literature. Particularly interesting are the predictions of lithium depletion for the mass (0.08–0.05M_⊙) and likely age (300–800 Myr) of the substellar components. High‐resolution optical spectra of GJ 569B (the pair is not resolved) obtained with HIRES at the Keck telescope show that there has been significant lithium depletion in both components. We will compare these results to state‐of‐the‐art theoretical calculations. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Diamictic sediments within high Arctic lake sediment cores: evidence for lake ice rafting along the lateral glacial margin   总被引：2，自引：0，他引：2  

I. Rod Smith 《Sedimentology》2000,47(6):1157-1179

Sediment cores from six small lake basins in the Canadian high Arctic reveal a gravel‐rich (≤30% by weight) to gravel‐poor (≥2%) diamict facies underlying massive, post‐glacial, clayey silt. Ten other lakes contain a second diamict facies within what are interpreted to be glaciolacustrine sedimentary assemblages. The sedimentology, clast fabrics and fossil remains (diatoms, ostracodes and chironomid head capsules) within both diamict facies suggest that these deposits are not tills. Clast fabrics yielded low S₁ (0·41–0·57) and high S₃ (0·09–0·22) eigenvalues, placing them within the range of ice‐rafted diamictons and glacigenic sediment flows. The high percentage of clast dip angles >45° (15–61%), random clast azimuth and lower diamict contacts conformable to underlying current‐bedded sediment favours an origin as a rain‐out or settling deposit. Samples of the matrix and scrapings of clasts from the diamicts revealed a diatom assemblage dominated by littoral and planktonic forms, such as are found in the littoral regions of the lakes today. This contrasts sharply with the assemblages within the overlying clayey silt, in which benthic forms predominate. Clasts are thus interpreted to have been rafted from the littoral areas of the lake. The process proposed to explain this is rafting by the lake ice cover in a glacial‐marginal environment. Early season meltwater, impounded along the lateral margin of retreating cold‐based glaciers, would buoyantly lift the lake ice cover and any adfrozen lake sediment. Higher lake levels and increased areal extent of seasonal freeze‐on between the lake ice cover and the lake bed would allow the redeposition of littoral sediments to the benthic regions through greater lateral shifting of the ice cover as it broke up. Incision by meltwater streams into the lateral glacial margins would later isolate the lake, allowing seasonal warming of lake water, enough to support the growth and maturation of the ostracode and chironomid species found as fossils within the diamicts.  相似文献   

Macroinvertebrates of a rocky shore in the freshwater tidal Hudson River     

David L. Strayer  Lane C. Smith 《Estuaries and Coasts》2000,23(3):359-366

We studied the macroinvertebrate fauna of a rocky shore in the freshwater tidal Hudson River during 1992–1994, the early years of the zebra mussel (Dreissena polymorpha) invasion. The macroinvertebrate community was numerically dominated by chironomids, nematodes, oligochaetes, gastropods, zebra mussels, and planarian flatworms. The community was a mixture of species typical of stony warm water rivers and lake shores, freshwater generalists, and semiterrestrial species. Overall macroinvertebrate densities were moderate to low (2,800–14,600 m⁻²). Density was a strong function of season and elevation, with consistently low densities in the early spring and in the intertidal zone. This pattern suggests that physical harshness (alternating submergence and desiccation;ice and low temperatures) limits the distribution of invertebrates at this site. Zebra mussels occurred at our study site chiefly below the low tide mark, but only at moderate abundance (usually <1,000 m⁻²). A weak correlation between the densities of zebra mussels and those of other macroinvertebrates nonetheless suggests that the zebra mussel invasion may have affected community structure.  相似文献   

William Gilbert: the first palaeomagnetist     

Prof.  Emeritus Rod Wilson 《Astronomy& Geophysics》2000,41(3):3.16-3.19

William Gilbert first described the Earth as a giant dipole magnet 400 years ago. But, as Rod Wilson recounts, he did far more than this.  相似文献   

Concepts,Conceptualization, and Conceptions in Geography     

Rod Lane  Jennifer Carter  Theresa Bourke 《The Journal of geography》2019,118(1):11-20

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Editor's note     

David Cooper  Rod Hine  Darren Bellerby  Peter Ghiringhelli 《Astrophysics and Space Science》1995,229(1):163-167

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Vernacular heritage and evolving environmental policy in Australia: Lessons from the Murray–Darling Outreach Project     

Ruth Lane  Joanna Wills  Frank Vanclay  Damian Lucas 《Geoforum》2008,39(3):1308-1320

The interface between environmentalism and neoliberalism in industrialised nations is dynamic and evolving with each of these significant socio-political movements exerting influence on the other. In the context of Australian environmental policy, ideas of heritage, sense of place and belonging are increasingly invoked to support the current policy emphasis on the role of regional communities for realising goals for land and water conservation and environmental restoration. To explore the broader meaning and consequences of these developments, we focus on the manner in which ideas of heritage are employed and evoked within the Murray–Darling Outreach Project, a collaboration between the Murray–Darling Basin Commission, a key natural resource management agency, and the National Museum of Australia. The Murray–Darling Outreach Project has the aim of increasing community involvement in local environmental issues by promoting ideas of vernacular heritage.  相似文献