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Coral mortality may result in macroalgal proliferation or a phase shift into an alga-dominated state. Subtidal, high-latitude western Indian Ocean coral communities at Sodwana Bay on the KwaZulu-Natal coast, South Africa, have experienced some mortality because of warm-water anomalies, storms and other causes, but the response of the macroalgae is unknown. We investigated the abundance and diversity of benthic algae on different hard natural substrata (dead digitate, brain and plate corals and beach rock) on Two-Mile Reef, Sodwana Bay. We also compared algal communities colonising ceramic, marble and pretreated ceramic tiles placed on the reef for six months. We identified 95 algae (14 Chlorophyta, 11 Phaeophyceae, 69 Rhodophyta and one cyanobacterium). Assemblages on natural and artificial substrata were dominated by the brown alga Lobophora variegata (Lamouroux) Womersley ex Oliveira and non-geniculate corallines (Rhodophyta, Corallinaceae). Cluster and ordination analyses revealed that the algae showed no affinity for particular substrata, whether natural or artificial. Algal cover was occasionally higher on rougher tiles and crustose corallines were significantly more abundant on marble than ceramic tiles. Two-Mile Reef had 23.1% dead and 48.4% live scleractinian coral cover, where dead corals were colonised indiscriminately by many small algal species, but there was no evidence of algal proliferation. The results provide a baseline for monitoring this high-latitude reef system. 相似文献
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Mineralized veins at Major's Creek consist of preponderant quartz and carbonate gangue with gold, Au-Ag tellurides and base metal sulphides within silicified and sericitized dykes or granodiorite of the Braidwood Granite. Fluid inclusion studies indicate deposition throughout the range 350–80°C by low salinity fluids. Significant Au-Ag telluride mineralization took place at a temperature of about 155°C. Mineral deposition was due to the separation of a liquid CO2 phase from an originally CO2-rich aqueous fluid. Observed argillic alteration is a consequence of acid leaching above the boiling zone. Mineralization is epithermal in character and probably formed during the existence of a hydrothermal convective system. A relationship with similar epithermal gold deposits in the adjacent Eden-Yalwal Rift zone is inferred. 相似文献
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Elaine M. Sadler Russell D. Cannon Tom Mauch Paul J. Hancock David A. Wake Nic Ross Scott M. Croom Michael J. Drinkwater Alastair C. Edge Daniel Eisenstein rew M. Hopkins Helen M. Johnston Robert Nichol Kevin A. Pimbblet Roberto De Propris Isaac G. Roseboom Donald P. Schneider Tom Shanks 《Monthly notices of the Royal Astronomical Society》2007,381(1):211-227
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Russell Cannon Michael Drinkwater Alastair Edge Daniel Eisenstein Robert Nichol Phillip Outram Kevin Pimbblet Roberto De Propris Isaac Roseboom David Wake Paul Allen Joss Bland-Hawthorn Terry Bridges Daniel Carson Kuenley Chiu Matthew Colless Warrick Couch Scott Croom Simon Driver Stephen Fine Paul Hewett Jon Loveday Nicholas Ross Elaine M. Sadler Tom Shanks Robert Sharp J. Allyn Smith Chris Stoughton Peter Weilbacher Robert J. Brunner Avery Meiksin Donald P. Schneider 《Monthly notices of the Royal Astronomical Society》2006,372(1):425-442
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R. A. Glen B. J. Drummond B. R. Goleby D. Palmer K. D. Wake‐Dyster 《Australian Journal of Earth Sciences》2013,60(4):341-352
The Cobar Basin in central western New South Wales is a mineral‐rich Early Devonian basin typical of those that characterize the Siluro‐Devonian history of the Lachlan Orogen of southeastern Australia. One hundred and seventy kilometres of seismic profiling in three lines across the basin have shown it to be asymmetrical in shape with an east‐dipping western margin that is steeper than the moderately west‐dipping eastern margin. Maximum basin thickness is around 6 km, but there are significant thickness changes, especially from south to north, which reflect the effect of synsedimentary faulting. Seismic profiling suggests that the basin deformed by thin‐skinned tectonics; postulated strike‐slip effects were not visible on the sections. The seismic profiling has, for the first time, imaged the western synrift basin margin which is generally not exposed. Strain variations during deformation along this edge were taken up by the formation of a major jog ('dog‐leg') which has propagated into the basin as a tear fault. Intrabasinal tears, as well as thrusts, which link into one or more detachments, provide potential pathways for mineralizing fluids during basin inversion. 相似文献
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Quantifying groundwater–surface water interactions in a proglacial valley,Cordillera Blanca,Peru 
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下载免费PDF全文 Lauren D. Somers Ryan P. Gordon Jeffrey M. McKenzie Laura K. Lautz Oliver Wigmore AnneMarie Glose Robin Glas Caroline Aubry‐Wake Bryan Mark Michel Baraer Thomas Condom 《水文研究》2016,30(17):2915-2929
A myriad of downstream communities and industries rely on streams fed by both groundwater discharge and glacier meltwater draining the Cordillera Blanca, Northern Peruvian Andes, which contains the highest density of glaciers in the tropics. During the dry season, approximately half the discharge in the region's proglacial streams comes from groundwater. However, because of the remote and difficult access to the region, there are few field methods that are effective at the reach scale to identify the spatial distribution of groundwater discharge. An energy balance model, Rhodamine WT dye tracing, and high‐definition kite‐borne imagery were used to determine gross and net groundwater inputs to a 4‐km reach of the Quilcay River in Huascaran National Park, Peru. The HFLUX computer programme ( http://hydrology.syr.edu/hflux.html ) was used to simulate the Quilcay River's energy balance using stream temperature observations, meteorological measurements, and kite‐borne areal photography. Inference from the model indicates 29% of stream discharge at the reach outlet was contributed by groundwater discharge over the study section. Rhodamine WT dye tracing results, coupled with the energy balance, show that approximately 49% of stream water is exchanged (no net gain) with the subsurface as gross gains and losses. The results suggest that gross gains from groundwater are largest in a moraine subreach but because of large gross losses, net gains are larger in the meadow subreaches. These insights into pathways of groundwater–surface water interaction can be applied to improve hydrological modelling in proglacial catchments throughout South America. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Adrian Collister Ofer Lahav Chris Blake Russell Cannon Scott Croom Michael Drinkwater Alastair Edge Daniel Eisenstein Jon Loveday Robert Nichol Kevin Pimbblet Roberto De Propris Isaac Roseboom Nic Ross Donald P. Schneider Tom Shanks David Wake 《Monthly notices of the Royal Astronomical Society》2007,375(1):68-76
We describe the construction of MegaZ-LRG, a photometric redshift catalogue of over one million luminous red galaxies (LRGs) in the redshift range 0.4 < z < 0.7 with limiting magnitude i < 20 . The catalogue is selected from the imaging data of the Sloan Digital Sky Survey (SDSS) Data Release 4. The 2dF-SDSS LRG and Quasar (2SLAQ) spectroscopic redshift catalogue of 13 000 intermediate-redshift LRGs provides a photometric redshift training set, allowing use of ann z, a neural network-based photometric-redshift estimator. The rms photometric redshift accuracy obtained for an evaluation set selected from the 2SLAQ sample is σ z = 0.049 averaged over all galaxies, and σ z = 0.040 for a brighter subsample ( i < 19.0) . The catalogue is expected to contain ∼5 per cent stellar contamination. The ann z code is used to compute a refined star/galaxy probability based on a range of photometric parameters; this allows the contamination fraction to be reduced to 2 per cent with negligible loss of genuine galaxies. The MegaZ-LRG catalogue is publicly available on the World Wide Web from http://www.2slaq.info . 相似文献