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31.
32.
Seismic evidence of up to 200 m lake‐level change in Southern Patagonia since Marine Isotope Stage 4
ANDREA CATALINA GEBHARDT CHRISTIAN OHLENDORF FRANK NIESSEN MARC DE BATIST FLAVIO S. ANSELMETTI DANIEL ARIZTEGUI PIERRE KLIEM STEFAN WASTEGÅRD BERND ZOLITSCHKA 《Sedimentology》2012,59(3):1087-1100
Maar lake Laguna Potrok Aike is located north of the Strait of Magellan (south‐eastern Patagonia). Seismic reflection profiles revealed a highly dynamic palaeoclimate history. Dunes were identified in the eastern part of the lake at approximately 30 to 80 m below the lake floor, overlying older lacustrine strata, and suggest that the region experienced dry conditions probably combined with strong westerly winds. It is quite likely that this can be linked to a major dust event recorded in the Antarctic ice cores during Marine Isotope Stage 4. The dunes are overlain by a series of palaeo‐shorelines indicating a stepwise water‐level evolution of a new lake established after this dry period, and thus a change towards wetter conditions. After the initial, rapid and stepwise lake‐level rise, the basin became deeper and wider, and sediments deposited on the lake shoulder at approximately 33 m below present‐day lake level point towards a long period of lake‐level highstand between roughly 53·5 ka cal. bp and 30 ka cal. bp with a maximum lake level some 200 m higher than the desiccation horizon. This highstand was then followed by a regressional phase of uncertain age, although it must have happened some time between approximately 30 ka cal. bp and 6750 yrs cal. bp . Dryer conditions during the Mid‐Holocene are evidenced by a dropping lake level, resulting in a basin‐wide erosional unconformity on the lake shoulder. A second stepwise transgression between ca 5·8 to 5·4 ka cal. bp and ca 4·7 to 4 ka cal. bp with palaeo‐shorelines deposited on the lake shoulder unconformity again indicates a change towards wetter conditions. 相似文献
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Calanoid copepods of the genus Boeckella and Parabroteas (P. sarsi) are dominant in zooplankton communities of Patagonian lakes and ponds. This study addresses the occurrence of sexual size dimorphism in calanoid copepods of the genus Boeckella and in the monospecific genus Parabroteas occurring in 12 lakes and ponds of Patagonia (Argentina). The morphometric analysis performed showed that in all the species studied the female is larger than the male, although the difference in size among sexes was found to be variable between species. Interestingly, all species showed significant intraspecific stability in their sexual size dimorphism despite potential differences in their environments regarding predation pressure, environmental stability (permanent or temporary waters) and altitude distribution of populations. Finally, we discuss the potential implications of sexual dimorphism in terms of resource use and vulnerability to predation among other environmental forces which may play a role in promoting larger female to male size. 相似文献
34.
Evolution of steam assisted gravity drainage (SAGD) steam chambers in heavy oil and bitumen reservoirs is tied to uniformity
of steam pressure and quality along the length of the perforated interval of the well and reservoir geology and fluid properties
adjacent to the well. If the reservoir geology has poor permeability at an interval along the wellpair, then steam delivery
to and fluids production from the reservoir is not uniform. If the steam is well distributed throughout the injection well,
then the key factor for a uniform steam chamber along the wellpair is reservoir geology. This is especially important in highly
heterogeneous, variable thickness reservoirs where geology and reservoir oil composition may vary significantly over the length
of a wellpair. Heterogeneity of a growing SAGD steam chamber is related to heterogeneity of the underlying geology. In this
study the oil sands models are geostatistically populated to model spatial heterogeneity of permeability. The temperature
profile (chamber growth), steam chamber height, conductive, convective, and total heat fluxes have been examined in each case.
The results reveal that the length scales of steam chamber growth depend on the permeability heterogeneity. This provides
a means to decide length scales for placement of in-well control devices in steam injectors in SAGD. 相似文献
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36.
Impact of AMD on water quality in critical watershed in the Hudson River drainage basin: Phillips Mine,Hudson Highlands,New York 总被引:1,自引:0,他引:1
Sivajini Gilchrist Alexander Gates Zoltan Szabo Paul J. Lamothe 《Environmental Geology》2009,57(2):397-409
A sulfur and trace element enriched U–Th-laced tailings pile at the abandoned Phillips Mine in Garrison, New York, releases
acid mine drainage (AMD, generally pH < 3, minimum pH 1.78) into the first-order Copper Mine Brook (CMB) that drains into
the Hudson River. The pyrrhotite-rich Phillips Mine is located in the Highlands region, a critical water source for the New
York metro area. A conceptual model for derivation/dissolution, sequestration, transport and dilution of contaminants is proposed.
The acidic water interacts with the tailings, leaching and dissolving the trace metals. AMD evaporation during dry periods
concentrates solid phase trace metals and sulfate, forming melanterite (FeSO4·7H2O) on sulfide-rich tailings surfaces. Wet periods dissolve these concentrates/precipitates, releasing stored acidity and trace
metals into the CMB. Sediments along CMB are enriched in iron hydroxides which act as sinks for metals, indicating progressive
sequestration that correlates with dilution and sharp rise in pH when mine water mixes with tributaries. Seasonal variations
in metal concentrations were partly attributable to dissolution of the efflorescent salts with their sorbed metals and additional
metals from surging acidic seepage induced by precipitation. 相似文献
37.
Paulo Pinheiro da Silva Leonardo Salayandía Aída Gándara Ann Q. Gates 《Earth Science Informatics》2009,2(4):249-269
The realization of an international cyberinfrastructure of shared resources to overcome time and space limitations is challenging
scientists to rethink how to document their processes. Many known scientific process requirements that would normally be considered
impossible to implement a few years ago are close to becoming a reality for scientists, such as large scale integration and
data reuse, data sharing across distinct scientific domains, comprehensive support for explaining process results, and full
search capability for scientific products across domains. This article introduces the CI-Miner approach that can be used to
aggregate knowledge about scientific processes and their products through the use of semantic annotations. The article shows
how this aggregated knowledge is used to benefit scientists during the development of their research activities. The discussion
is grounded on lessons learned through the use of CI-Miner to semantically annotate scientific processes in the areas of geo-sciences,
environmental sciences and solar physics: A use case in the field of geo-science illustrates the CI-Miner approach in action. 相似文献
38.
J. W. C. Gates 《The Photogrammetric Record》1997,15(89):809-811
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