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91.
Dolomite in caves: Recent dolomite formation in oxic, non-sulfate environments. Castañar Cave, Spain
Dolomite is a common mineral in the rock record but rare in recent superficial environments. Where it does occur, it is related to anoxic, sulfate-rich environments and microbial activity. The occurrence of some dolomite deposits in caves, however, indicates that dolomite formation is also possible in oxic, non-sulfate settings. Dolomite is forming at 17 °C and in oxic-vadose conditions on the host rocks and aragonite speleothems of the Castañar Cave, Cáceres, Spain. It appears as spheroids and dumbbells 50–300 μm in diameter that internally consist of micron-sized rhombic to rounded crystals. Initially this dolomite is Ca-rich, non-stoichiometric and poorly ordered. Mg-rich solutions allow the precipitation of metastable Mg-rich carbonates, such as huntite. This soon transforms into this Ca-rich dolomite, which later “ages” to form a more stoichiometric dolomite. These dolomites show similarities to those grown under anoxic, sulfate-rich conditions and their presence in caves provides a different setting that may contribute to the understanding of the “dolomite problem”, including their initial formation and later recrystallization processes. 相似文献
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The investigation of a limestone cave on the Ryonggok-ri of Sangwon County, North Hwanghae Province, DPRK, has yielded many faunal remains including Late Pleistocene deer, brown bears and horses. Uranium series dating of fossil teeth yielded dates of ~72ka at the base of Layer 2 – the bone-bearing unit – and ~44ka at the top. The rich and diverse mammal remains of Ryonggok Cave No. 1 are indicative of warm and humid temperate conditions during the Late Pleistocene, and reflect the presence of both dense forests and open grassland. In addition, pollen and spores from the site include two families and 24 genera of trees, six families and a genus of grasses and herbs, and two families and six genera of ferns, corroborating the environments inferred from the faunal remains. 相似文献
96.
Thomas Boyle 《The Australian geographer》2012,43(4):393-410
As the social, ecological and economic benefits of green buildings become more established, firms, especially professional service firms, are responding by adopting sustainable office space (SOS). Accelerating this uptake demands a nuanced appreciation of firms’ understandings of and motivations for adopting SOS. Through a qualitative study of professional service firms in Sydney, this paper brings together a decentred understanding of the contemporary firm drawn from the ‘new economic geographies’ approach and theories of corporate social responsibility to trace and interpret the diverse and overlapping motivations shaping the uptake of SOS amongst these firms. The firm is shown to be a site of plurality and agency, governed by multiple logics. Whilst motivations informed by economic logic remain persuasive and pervasive, the adoption of SOS is simultaneously informed by a wider palette of logics, including environmental and social logics. The paper argues that a decentred conceptualisation of the firm brings the multiplicity of firms’ orientations towards SOS into view and, in so doing, has the potential to inform a politics of intervention for steering firms towards more socially and environmentally sustainable behaviours. 相似文献
97.
《Experimental Astronomy》2009,23(1):277-302
The Molecular Hydrogen Explorer, H2EX, was proposed in response to the ESA 2015 - 2025 Cosmic Vision Call as a medium class space mission with NASA and CSA participations.
The mission, conceived to understand the formation of galaxies, stars and planets from molecular hydrogen, is designed to
observe the first rotational lines of the H2 molecule (28.2, 17.0, 12.3 and 9.7 μm) over a wide field, and at high spectral resolution. H2EX can provide an inventory of warm (≥ 100 K) molecular gas in a broad variety of objects, including nearby young star clusters,
galactic molecular clouds, active galactic nuclei, local and distant galaxies. The rich array of molecular, atomic and ionic
lines, as well as solid state features available in the 8 to 29 μm spectral range brings additional science dimensions to
H2EX. We present the optical and mechanical design of the H2EX payload based on an innovative Imaging Fourier Transform Spectrometer fed by a 1.2 m telescope. The 20’×20’ field of view
is imaged on two 1024×1024 Si:As detectors. The maximum resolution of 0.032 cm − 1 (full width at half maximum) means a velocity resolution of 10 km s − 1 for the 0 – 0 S(3) line at 9.7 μm. This instrument offers the large field of view necessary to survey extended emission in
the Galaxy and local Universe galaxies as well as to perform unbiased extragalactic and circumstellar disks surveys. The high
spectral resolution makes H2EX uniquely suited to study the dynamics of H2 in all these environments. The mission plan is made of seven wide-field spectro-imaging legacy programs, from the cosmic
web to galactic young star clusters, within a nominal two years mission. The payload has been designed to re-use the Planck platform and passive cooling design.
相似文献
J. P. Maillard (Corresponding author)Email: |
98.
Shi-Yang Jiang Fu-Yuan Zhao National Astronomical Observatory Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2007,7(2):325-328
We presume the re-brightening of SN 1006 in AD 1016 as recorded in the ancient Chinese literature to be true and the re-brightening was caused by the encounter either of photons or the shock wave from the SN outburst with the circumstellar thin envelope mate- rials. Based on these considerations, and combining the observational results on the optical proper motion of the N-W limb and the radio observations of the other parts of the supernova remnant G327.6 14.5, we re-determine the distance to SN 1006. For the photon-encounter model, the average radius of the envelope material would be 10ly; and for the shock wave- encounter model, the radius would be about 1 ly. We then set up four equations to solve for the distance of the SN, the initial shock speed, the expansion index for two different parts of the supernova remnant, and the real original radius of the thin envelope nebula. It is indicated that only the case of photon-encounter will lead to a reasonable result. We derived a distance of 5074ly (1.56kpc), an original shock expansion velocity of 0.071c, an expansion index of 0.72 for the N-W limb of the SNR, and 0.76 for the other parts . We deem that the SNR evolution is still in the stage of reverse shock. 相似文献
99.
G. N. Huppert 《Environmental Geology》1995,26(2):121-123
This study reviews significant state and federal laws that can be used to protect karst, caves, and associated unique minerals and biota. The first state cave protection act was passed in Colorado in 1883; unfortunately it was repealed in 1971. From that modest beginning there are now a total of 22 states, Puerto Rico, and the Cherokee Nation that have specific cave protection acts. Most of these have been legislated during the last 20 years. There are a number of laws on the federal level that can be used for cave protection. The most important of these is the Federal Cave Resources Protection Act of 1988, which mandates cave conservation for many federal land management agencies. The Endangered Species Act of 1973 and the Federal Archaeological Resources Protection Act of 1976 can also be of significant use in the conservation of caves on federal land. The effects of these acts are variable. One factor is how important agency officials and law enforcement officers regard caves. It has not been unusual that little was done in the way of protection or prosecution even when the perpetrators have been apprehended. This attitude is changing rapidly primarily because those involved in enforcing the laws have been educated to the uniqueness and values of caves and their contents. 相似文献
100.
Influences of agricultural practices on water quality of Tumbling Creek cave stream in Taney County,Missouri 总被引:1,自引:0,他引:1
Influences of agricultural practices on water quality of the Tumbling Creek cave stream are of particular interest because of the karst nature of the area and the recent implementation of a Better Management Practice (BMP). Water quality parameters, measured bi-weekly during one year, consisted of pH, turbidity, water temperature, specific conductivity, total dissolved solids, alkalinity, and chloride. Heavy metals, nutrient and bacteria levels were also monitored during the study. Effects of land use were most obvious in turbidity, nitrate, chloride, and bacteria levels. Sites within the recharge area that pose a major threat to its water quality were identified. Results provide a baseline for these water quality parameters and their seasonal variability that can be used in future studies to address the effects of water quality and stream sediment contamination on the caves ecosystem and to determine the effectiveness of the BMP implemented in this karst area. 相似文献