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YEONG BAE SEONG LEWIS A. OWEN HYOUN SOO LIM HO IL YOON YEADONG KIM YONG IL LEE MARC W. CAFFEE 《Boreas: An International Journal of Quaternary Research》2009,38(2):207-213
Glacial landforms on the Barton and Weaver peninsulas of King George Island in the South Shetland Islands, West Antarctica were mapped and dated using terrestrial cosmogenic 36 Cl methods to provide the first quantitative terrestrial record for late Quaternary deglaciation in the South Shetland Islands. 36 Cl ages on glacially eroded and striated bedrock surfaces range from 15.5±2.5 kyr to 1.0±0.7 kyr. The 36 Cl ages are younger with decreasing altitude, indicating progressive downwasting of the southwestern part of the Collins Ice Cap at a rate of ∼12 mm yr−1 since 15.5±2.5 kyr ago, supporting the previously published marine records for the timing and estimate of the rate of deglaciation in this region. 相似文献
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Maritime/continental microphysical contrasts in stratus 总被引：5，自引：0，他引：5
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Internet GIS上矢量型空间数据传送的最优化策略 总被引：4，自引：0，他引：4
作为在Internet上处理大空量空间地理信息的基于客户端的Internet地理信息系统（client-side Internet GIS)，解决矢量型空间数据传送的低效率性是很重要的，该文为此提出一个新的有效方法，首先，将大型矢量地图根据适当的“分裂度”分割成若干部分，每一部分称作一个“炔”（Tile)，当用户在客户端请求地图的某一区域时，GIS服务器中传递和请求区域相关叠的“块”内的空间数据，并且将该数据存在用户的本地机上，以便使用。为此，该文提出一个“地图块分割”方法，地图块查询处理”算法以及“客户服务器间空间数据的效率化传送”策略，和既存传送方法比较，利用该方法构造的Internet GIS,系统的整体效率得到了提高。 相似文献
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Abstract Ultramafic xenoliths in alkali basalts from Jeju Island, Korea, are mostly spinel lherzolites with subordinate amounts of spinel harzburgites and pyroxenites. The compositions of major oxides and compatible to moderately incompatible elements of the Jeju peridotite xenoliths suggest that they are residues after various extents of melting. The estimated degrees of partial melting from compositionally homogeneous and unfractionated mantle to form the residual xenoliths reach 30%. However, their complex patterns of chondrite-normalized rare earth element, from light rare earth element (LREE)-depleted through spoon-shaped to LREE-enriched, reflect an additional process. Metasomatism by a small amount of melt/fluid enriched in LREE followed the former melt removal, which resulted in the enrichment of the incompatible trace elements. Sr and Nd isotopic ratios of the Jeju xenoliths display a wide scatter from depleted mid-oceanic ridge basalt (MORB)-like to near bulk-earth estimates along the MORB–oceanic island basalt (OIB) mantle array. The varieties in modal proportions of minerals, (La/Yb)N ratio and Sr-Nd isotopes for the xenoliths demonstrate that the lithospheric mantle beneath Jeju Island is heterogeneous. The heterogeneity is a probable result of its long-term growth and enrichment history. 相似文献
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The formation and evolution of glacier moraine-dammed lakes are closely related to past glacier expansion and retreat. Geomorphic markers such as lacustrine terraces and beach ridges observed in these lakes provide important evidence for regional paleoenvironment reconstruction. We document the magnitude of paleo-shoreline fluctuations and timings of highstands of lake water by using cosmogenic ~(10)Be surface exposure dating and optically stimulated luminescence(OSL) dating on samples collected from lacustrine sediment and bedrock strath in Lake Khagiin Khar. The lake was initially impounded by glacier moraine at the Global Last Glacial maximum(gLGM; 21–19 ka), and the lake reached its maximum paleo-shoreline level of 1840 m at sea level(a.s.l.). At that time, the stored lake water amount was up to seven times greater and the surface area was three times larger than the present values. The paleolake experienced higher shoreline levels at 1832, 1822, and 1817 m a.s.l. and reached the present lake level after 0.4 ka. We interpret that decrease in the paleolake level was caused by spillover. The increase in melt water after the gLGM and the Late Glacial exceeded the storage threshold of the lake, and the paleolake water overflowed across the lowest drainage divides. The lake spilled over across the lowest bedrock ridge at 15.9 ± 0.6 ka, and the outlet was incised since that time at a rate of 3.72 ± 0.15 mm/yr. The initial stream of the Khiidiin Pass River was disturbed by LGM moraine damming and was rerouted into the present course running through moraine after the spillover at 15.9 ± 0.6 ka. 相似文献
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