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41.
42.
Rainer Altherr Manfred Schliestedt Martin Okrusch Eberhard Seidel Hans Kreuzer Wilhelm Harre Heinz Lenz Immo Wendt Günther A. Wagner 《Contributions to Mineralogy and Petrology》1979,70(3):245-255
Polymetamorphic rocks of Sifnos (Greece) have been investigated by Rb-Sr, K-Ar, and fission track methods. Critical mineral assemblages from the northern and southernmost parts of Sifnos include jadeite+quartz+3T phengite, and omphacite+garnet +3T phengite, whereas the central part is characterized by the assemblage albite+chlorite+epidote+2M
1 phengite.K-Ar and Rb-Sr dates on phengites (predominantly 3T) of the best preserved high P/itTmetamorphic rocks from northern Sifnos gave concordant ages around 42 m.y., indicating a Late Lutetian age for the high P/T metamorphism. Phengites (2M
1+3T) of less preserved high P/T assemblages yielded K-Ar dates between 48 and 41 m.y. but generally lower Rb-Sr dates. The higher K-Ar dates are interpreted as being elevated by excess argon.K-Ar and Rb-Sr ages on 2M
1 phengites from central Sifnos vary between 24 and 21 m.y. These ages date a second, greenschist-facies metamorphism which overprinted the earlier high-pressure metamorphic rocks. 相似文献
43.
44.
From wind profile and wave measurements performed during the JONSWAP II experiment, relations between the dimensionless profile slope and the significant wave height are derived. It is shown that the wind profile is distorted by the waves especially in the vicinity of the water surface. The wave influence on the profile seems to be restricted to heights below about three wave heights. Above this level, the dimensionless profile slope is an approximately constant value corresponding to a drag coefficient of about 1.15 × 10–3. 相似文献
45.
46.
Hong Kong is a hyper-dense city with 7×106 people living in an area of 1100km2. One way to improve the livability of compacted and congested cities like Hong Kong is through the provision of urban parks,
an aspect that has largely been under-researched. This study focuses on how users perceive and utilize various facilities
in the Kowloon Park. The findings revealed that the Kowloon Park is one of the most preferred parks in Hong Kong for both
local residents and tourists. Users were quite satisfied with the park’s facilities. Notably, the most important component
of an urban park is its greenery. This is followed by water elements, seating places, and facilities for various recreational
activities. The improvements users would like to see in urban parks include good design and management, meeting users’ needs,
overcoming barriers to use, and providing a high quality and varied experience for different groups in the community. The
findings of this study provide a good basis to address park management issues from the users’ perspective. In particular,
parks should provide easy access, encourage optimum usage and enable complimentary improvements to the environment.
Foundation item: Under the auspices of the Germany-Hong Kong Joint Research Scheme (No.GER/99-00/01) and the Faculty Research
Grant of the Hong Kong Baptist University (No.FRG/00-01/I-38)
Biography: WONG Koon-kwai (1950—), male, a native of Guangdong Province, Ph.D., associate professor, specialized in the analysis
of human-environment interaction. E-mail: kenwong@hkbu.edu.hk 相似文献
47.
Yannick Garcin Annett Junginger Daniel Melnick Daniel O. Olago Manfred R. Strecker Martin H. Trauth 《Quaternary Science Reviews》2009,28(9-10):911-925
The Late Pleistocene to Middle Holocene African Humid Period (AHP) was characterized by dramatic hydrologic fluctuations in the tropics. A better knowledge of the timing, spatial extent, and magnitude of these hydrological fluctuations is essential to decipher the climate-forcing mechanisms that controlled them. The Suguta Valley (2°N, northern Kenya Rift) has recorded extreme environmental changes during the AHP. Extensive outcrops of lacustrine sediments, ubiquitous wave-cut notches, shorelines, and broad terrace treads along the valley margins are the vestiges of Lake Suguta, which once filled an 80 km long and 20 km wide volcano–tectonic depression. Lake Suguta was deep between 16.5 and 8.5 cal ka BP. During its maximum highstand, it attained a water depth of ca 300 m, a surface area of ca 2150 km2, and a volume of ca 390 km3. The spatial distribution of lake sediments, the elevation of palaeo-shorelines, and other geomorphic evidences suggest that palaeo-Lake Suguta had an overflow towards the Turkana basin to the north. After 8.5 cal ka BP, Lake Suguta abruptly disappeared. A comparison of the Lake Suguta water-level curve with other reconstructed water levels from the northern part of the East African Rift System shows that local insolation, which is dominated by precessional cycles, may have controlled the timing of lake highstands in this region. Our data show that changes of lake levels close to the Equator seem to be driven by fluctuations of spring insolation, while fluctuations north of the Equator are apparently related to variations in summer insolation. However, since these inferred timings of lake-level changes are mostly based on the radiocarbon dating of carbonate shells, which may have been affected by a local age reservoir, alternative dating methods are needed to support this regional synthesis. Between 12.7 and 11.8 cal ka BP, approximately during the Northern Hemisphere high-latitude Younger Dryas, the water level of Lake Suguta fell by ca 50 m, suggesting that remote influences also affected local hydrology. 相似文献
48.
49.
Dam Quang-Minh Manfred Frechen Tran Nghi Jan Harff 《International Journal of Earth Sciences》2010,99(8):1731-1740
In Vietnam, the coastal sand barriers and dunes located in front of the steep slopes of the high rising Truong Son Mountains
are sensitive to climate and environment change and give evidence for Holocene sea-level rise. The outer barrier sands were
deposited shortly before or contemporaneous with the local sea-level high stand along the Van Phong Bay postdating the last
glacial maximum (LGM). Optically stimulated luminescence (OSL) dating yielded deposition ages ranging from 8.3 ± 0.6 to 6.2 ± 0.3 ka
for the stratigraphically oldest exposed barrier sands. Further periods of sand accumulation took place between 2.7 and 2.5 ka
and between 0.7 and 0.5 ka. The youngest period of sand mobilisation was dated to 0.2 ± 0.01 ka and is most likely related
to reworked sand from mining activities. At the Suoi Tien section in southern central Vietnam, the deposition of the inner
barrier sands very likely correlate with an earlier sea-level high stand prior to the last glaciation. OSL age estimates range
from 276 ± 17 to 139 ± 15 ka. OSL dating significantly improves our knowledge about the sedimentary dynamics along the coast
of Vietnam during the Holocene. 相似文献
50.
Manfred Frechen Dietrich Ellwanger Matthias Hinderer Jörg Lämmermann-Barthel Inge Neeb Astrid Techmer 《International Journal of Earth Sciences》2010,99(8):1955-1974
During the Pleistocene, the Rhine glacier system acted as a major south–north erosion and transport medium from the Swiss
Alps into the Upper Rhine Graben, which has been the main sediment sink forming low angle debris fans. Only some aggradation
resulted in the formation of terraces. Optically stimulated luminescence (OSL) and radiocarbon dating have been applied to
set up a more reliable chronological frame of Late Pleistocene and Holocene fluvial activity in the western Hochrhein Valley
and in the southern part of the Upper Rhine Graben. The stratigraphically oldest deposits exposed, a braided-river facies,
yielded OSL age estimates ranging from 59.6 ± 6.2 to 33.1 ± 3.0 ka. The data set does not enable to distinguish between a
linear age increase triggered by a continuous autocyclical aggradation or two (or more) age clusters, for example around 35 ka
and around 55 ka, triggered by climate change, including stadial and interstadial periods (sensu Dansgaard–Oeschger cycles).
The braided river facies is discontinuously (hiatus) covered by coarse-grained gravel-rich sediments deposited most likely
during a single event or short-time period of major melt water discharge postdating the Last Glacial Maximum. OSL age estimates
of fluvial and aeolian sediments from the above coarse-grained sediment layer are between 16.4 ± 0.8 and 10.6 ± 0.5 ka, and
make a correlation with the Late Glacial period very likely. The youngest fluvial aggradation period correlates to the beginning
of the Little Ice Age, as confirmed by OSL and radiocarbon ages. 相似文献