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61.
The county of Riverside California has a long history of land conservation. In this comparative case study between Western Riverside County and the Coachella Valley area in the county we show how governance institutions that encompass regions that have very different ecologies, are governed by rules and regulations that are undifferentiated relative to those differences. The study argues, however, that what may differ are the workings of the local urban regimes and the metabolic appropriation of ecosystems for economic growth. In this close investigation of the sprawling county of Riverside we find very different approaches to habitat preservation and the enrollment of nature for wealth production by the local urban regimes. 相似文献
62.
Stephanie L. DeSisto Heather E. Jamieson Michael B. Parsons 《Applied Geochemistry》2011,26(12):2004-2018
Hardpans, or cemented layers, form by precipitation and cementation of secondary minerals in mine tailings and may act as both physical and chemical barriers. Precipitation of secondary minerals during weathering of tailings can sequester metal(loid)s, thereby limiting their release to the environment. At Montague Gold Mines in Nova Scotia, tailings are partially cemented by the Fe arsenate mineral scorodite (FeAsO4·2H2O). Previous studies have shown that the formation of scorodite can effectively limit aqueous As concentrations due to its relatively low solubility (<1 mg/L at pH 3–4) and high As content (43–52 wt.% As2O5, this study). Co-existing waters and solids were sampled at Montague Gold Mines to identify present-day field conditions influencing scorodite precipitation and dissolution, and to better understand the mineralogical and chemical relationship between hardpan and tailings. In addition to scorodite, hardpan cements were found to include amorphous Fe arsenate and Fe oxyhydroxide. Nearly all hardpan is associated with historical arsenopyrite-bearing concentrate which provides a source of acidity, As5+ and Fe3+ for secondary mineral precipitation. Pore waters sampled from the hardpan have pH values ranging from 2.43 to 7.06. Waters with the lowest pH values also have the highest As concentrations (up to 35.8 mg/L) and are associated with the most extensive hardpan and greatest amount of weathered sulfide. Samples from areas with discontinuous hardpan and less sulfide have near-neutral pH and lower As concentrations. Detailed petrographic observations indicate that the identity and stability of As-bearing secondary minerals depends on the continued availability of sulfide concentrate. The results of this study are being used to develop remediation strategies for highly weathered, hardpan-bearing tailings that consider the stability of both primary and secondary minerals under various cover scenarios. 相似文献
63.
Sources of elevated salinity in the Mississippi River Alluvial Aquifer, south-central Louisiana, USA
Stephanie E. WelchJeffrey S. Hanor 《Applied Geochemistry》2011,26(8):1446-1451
Salinization is a process impacting groundwater quality and availability across much of southern Louisiana, USA. However, a broad divergence of opinion exists regarding the causes of this elevated salinity: updip-migrating marine waters from the Gulf of Mexico, saline fluids migrating up fault planes, movement of water from salt domes, and/or remnant seawater from the last major marine transgression. The Mississippi River Alluvial Aquifer (MRAA) in south-central Louisiana is recharged by the Mississippi River, and there are discharge zones to the west and east. Recharge waters from the Mississippi River are fresh, but Cl− levels in the western portions of the aquifer are as high as 1000 mg/L. The aquifer is an important source of water for several municipalities and industries, but prior to this study the source(s) of the elevated salinity or whether the salinization can be remediated had not been determined.The low Br/Cl ratios in the groundwaters are consistent with a saline endmember produced by subsurface dissolution of salt domes, not a marine source. The H and O isotopic systematics of the aquifer waters indicate meteoric sources for the H2O, not marine waters or diagenetically-altered deep brines. The westward salinization of aquifer water represents a broad regional process, instead of contamination by point sources. Mapping of spatial variations in salinity has permitted the identification of specific salt domes whose subsurface dissolution is producing waters of elevated salinity in the aquifer. These include the Bayou Choctaw and St. Gabriel domes, and possibly the Bayou Blue dome. Salinization is a natural, on-going process, and the potential for remediation or control is slight, if not non-existent. 相似文献
64.
The relative importance of buffering and brine inputs in controlling the abundance of Na and Ca in sedimentary formation waters 总被引:1,自引:0,他引:1
Stephanie Houston Craig SmalleyAdam Laycock Bruce W.D. Yardley 《Marine and Petroleum Geology》2011,28(6):1242-1251
The concentration of Ca in the formation waters of petroleum reservoirs can play a major role in influencing the outcome of a number of processes that are of great significance to the oil industry. For example, formation water Ca concentration affects the risk of carbonate scale formation during production. In order to better understand the concentrations of Ca in formation waters, we have investigated the chemistries of formation waters from a range of onshore and offshore basins worldwide, using published sources, as well as unpublished data held by BP. Although calcium and sodium are the principal cations in almost all formation waters they vary enormously in their relative proportions. We have identified three distinct trends on a plot of XCa (Ca/(Na + Ca)) against Cl. Most data lie on a high-Ca trend, here termed Trend 1, and show an increase in XCa with salinity. We interpret this as tracking equilibration with Ca and Na-bearing minerals, with the ratio (mol Ca/mol Na2) remaining approximately constant irrespective of salinity for chloride-dominated fluids. At very high salinities, Br-enriched bittern brines that have taken part in dolomitisation lie at the Cl-rich end of this trend. Some brines remain Na-dominated up to very high salinities and define a distinct low-Ca trend, Trend 2. These are associated with dissolution of halite beds and are interpreted to arise when the amount of Na in the pore fluid greatly exceeds the amount of Ca available in minerals. We refer to such brines as mass-limited; the sparsity of Ca in the rock-fluid system constrains XCa to a low value. Remarkably few brines lie between these trends. Finally, dilute formation waters show very large variations in XCa and may have bicarbonate as the dominant anion. They define a distinct low-Cl trend, Trend 3. We conclude that the behaviour of Na and Ca in most formation waters reflects equilibration with minerals, and concentrations of Ca in solution are sensitive to pH and PCO2 as well as to chloride concentration. For some brines however, the amount of salts in solution is sufficient to overwhelm the buffering capacity of the wallrocks. 相似文献
65.
Steven R. Jayne Nelson G. Hogg Stephanie N. Waterman Luc Rainville Kathleen A. Donohue D. Randolph Watts Karen L. Tracey Julie L. McClean Mathew E. Maltrud Bo Qiu Shuiming Chen Peter Hacker 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(12):2088-2099
This paper reports on the strength and structure of the Kuroshio Extension and its recirculation gyres. In the time average, quasi-permanent recirculation gyres are found to the north and south of the Kuroshio Extension jet. The characteristics of these recirculations gyres are determined from the combined observations from the Kuroshio Extension System Study (KESS) field program (June 2004–June 2006) and include current meters, pressure and current recording inverted echo sounders, and subsurface floats. The position and strength of the recirculation gyres simulated by a high-resolution numerical model are found to be consistent with the observations. The circulation pattern that is revealed is of a complex system of multiple recirculation gyres that are embedded in the crests and troughs of the quasi-permanent meanders of the Kuroshio Extension. At the location of the KESS array, the Kuroshio Extension jet and its recirculation gyres transport of about 114 Sv. This represents a 2.7-fold increase in the transport of the current compared to the Kuroshio's transport at Cape Ashizuri before it separates from the coast and flows eastward into the open ocean. This enhancement in the current's transport comes from the development of the flanking recirculation gyres. Estimates from an array of inverted echo sounders and a high-resolution ocean general circulation model are of similar magnitude. 相似文献
66.
Colin C. Turner Philip C. Richards John L. Swallow Stephanie P. Grimshaw 《Marine and Petroleum Geology》1984,1(2):105-117
The Upper Jurassic of the Outer Moray Firth Basin can be divided into two main stratigraphic units — the Piper and Kimmeridge Clay Formations. In each of these formations five major sedimentary facies can be recognized. The Piper Formation, of late Oxfordian to early Kimmeridgian age, comprises very fine to coarse-grained sandstones and minor mudstone of clastic shelf to shoreline origin. Large scale upward-coarsening sequences are well developed in some areas, particularly in the reservoir sands of the Tartan oilfield, and are interpreted as regressive, possibly deltaic deposits. The unconformably overlying Kimmeridge Clay Formation ranges in age from late Oxfordian through Volgian to Ryazanian. The formation is predominantly argillaceous, but also contains locally thick accumulations of sandstone deposited by gravity flow processes. The Claymore Sandstone Member is proposed as a new name for these sandstones in the region of the Claymore oilfield, where they form the major reservoir. Sands of the Piper Formation were derived mainly from the south-west, although some input from the north may also have occurred. Deposition may have extended further eastwards than the present erosional limit of the sands. Thick sand sequences in the Kimmeridge Clay Formation are probably restricted to the margins of the Witch Ground Graben, where contemporaneous faulting occurred. 相似文献
67.
Antonin?T.?LaurentEmail author Bernard?Bingen Stephanie?Duchene Martin?J.?Whitehouse Anne-magali?Seydoux-Guillaume Valerie?Bosse 《Contributions to Mineralogy and Petrology》2018,173(4):29
This contribution evaluates the relation between protracted zircon geochronological signal and protracted crustal melting in the course of polyphase high to ultrahigh temperature (UHT; T?>?900 °C) granulite facies metamorphism. New U–Pb, oxygen isotope, trace element, ion imaging and cathodoluminescence (CL) imaging data in zircon are reported from five samples from Rogaland, South Norway. The data reveal that the spread of apparent age captured by zircon, between 1040 and 930 Ma, results both from open-system growth and closed-system post-crystallization disturbance. Post-crystallization disturbance is evidenced by inverse age zoning induced by solid-state recrystallization of metamict cores that received an alpha dose above 35 × 1017 α g?1. Zircon neocrystallization is documented by CL-dark domains displaying O isotope open-system behaviour. In UHT samples, O isotopic ratios are homogenous (δ18O = 8.91?±?0.08‰), pointing to high-temperature diffusion. Scanning ion imaging of these CL-dark domains did not reveal unsupported radiogenic Pb. The continuous geochronological signal retrieved from the CL-dark zircon in UHT samples is similar to that of monazite for the two recognized metamorphic phases (M1: 1040–990 Ma; M2: 940–930 Ma). A specific zircon-forming event is identified in the orthopyroxene and UHT zone with a probability peak at ca. 975 Ma, lasting until ca. 955 Ma. Coupling U–Pb geochronology and Ti-in-zircon thermometry provides firm evidence of protracted melting lasting up to 110 My (1040–930 Ma) in the UHT zone, 85 My (ca. 1040–955 Ma) in the orthopyroxene zone and some 40 My (ca. 1040–1000 Ma) in the regional basement. These results demonstrate the persistence of melt over long timescales in the crust, punctuated by two UHT incursions. 相似文献
68.
69.
Reconstructing 4000 years of mass movement and tsunami history in a deep peri‐Alpine lake (Lake Geneva,France‐Switzerland)
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Katrina Kremer Michael Hilbe Guy Simpson Laurent Decrouy Walter Wildi Stephanie Girardclos 《Sedimentology》2015,62(5):1305-1327
The study of mass movements in lake sediments provides insights into past natural hazards at historic and prehistoric timescales. Sediments from the deep basin of Lake Geneva reveal a succession of six large‐scale (volumes of 22 × 106 to 250 × 106 m3) mass‐transport deposits, associated with five mass‐movement events within 2600 years (4000 cal bp to 563 ad ). The mass‐transport deposits result from: (i) lateral slope failures (mass‐transport deposit B at 3895 ± 225 cal bp and mass‐transport deposits A and C at 3683 ± 128 cal bp ); and (ii) Rhône delta collapses (mass‐transport deposits D to G dated at 2650 ± 150 cal bp , 2185 ± 85 cal bp , 1920 ± 120 cal bp and 563 ad , respectively). Mass‐transport deposits A and C were most probably triggered by an earthquake, whereas the Rhône delta collapses were likely to be due to sediment overload with a rockfall as the external trigger (mass‐transport deposit G, the Tauredunum event in 563 ad known from historical records), an earthquake (mass‐transport deposit E) or unknown external triggers (mass‐transport deposits D and F). Independent of their origin and trigger mechanisms, numerical simulations show that all of these recorded mass‐transport deposits are large enough to have generated at least metre‐scale tsunamis during mass movement initiation. Since the Tauredunum event in 563 ad , two small‐scale (volumes of 1 to 2 × 106 m3) mass‐transport deposits (H and I) are present in the seismic record, both of which are associated with small lateral slope failures. Mass‐transport deposits H and I might be related to earthquakes in Lausanne/Geneva (possibly) 1322 ad and Aigle 1584 ad , respectively. The sedimentary record of the deep basin of Lake Geneva, in combination with the historical record, show that during the past 3695 years, at least six tsunamis were generated by mass movements, indicating that the tsunami hazard in the Lake Geneva region should not be neglected, although such events are not frequent with a recurrence time of 0·0016 yr?1. 相似文献
70.
Timothy Saey Wouter Gheyle Birger Stichelbaut Jean Bourgeois Stephanie Verplaetse Veerle Van Eetvelde Nicolas Note Marc Van Meirvenne 《Geoarchaeology》2016,31(4):267-281
World War I (WWI) battlefields contain a large diversity of buried features that are situated just below the plough layer. A noninvasive interdisciplinary approach is preferred to characterize the buried heritage embedded within its soil landscape. In this study, the potential of integrating both electrical conductivity and magnetic susceptibility measurements from a multireceiver electromagnetic induction (EMI) instrument at a heavily shelled WWI battlefield was evaluated. Primarily, both measurements allowed the attribution of approximate depth interval to the buried trench remains. These remains proved dominantly present within the 0.4–0.8 m depth interval. Subsequently, both apparent electrical conductivity and magnetic susceptibility measurements were separately integrated to improve the contrast between buried features and their surrounding background. Trenches that were ditches filled with topsoil material could be distinguished from trenches that were continuously or partially filled with metal reinforcements or debris. To conclude, integrating multiple signals from a multireceiver EMI system allowed for a more straightforward discrimination of the buried WWI relicts. 相似文献