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排序方式: 共有208条查询结果,搜索用时 46 毫秒
91.
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吉兰泰盐湖区域地质特征及其形成演化的遥感解译 总被引:1,自引:0,他引:1
采用吉兰泰盐湖地区TM数据进行标准假彩色图像处理 ,对研究区构造、地貌、水系分布等地质特征进行解译和分析 ,探讨了吉兰泰盐湖的形成演化过程和盐湖形成的水体来源。结果表明 ,研究区贺兰山隆起带、吉兰泰沉降带、巴音乌拉山隆起带所组成的北北东向右行多字型斜列的基本构造格局 ,不仅控制着吉兰泰盐湖古湖盆的演化 ,而且控制着吉兰泰盐湖形成的水体来源 相似文献
93.
During a recent (2006) cruise of RV ‘Dana’ high resolution side-scan sonar and sub-bottom profiling was carried out on selected shelf and slope transects offshore Disko Bugt, central West Greenland. Available commercial seismic data from the margin indicate here irregular seabed morphology with erosional features locally extending down to c. 1100 m water depth. The newly acquired side-scan sonar data reveal the presence of giant iceberg plow marks extending (sub)parallel to the slope between about 800 and 1085 m water depth. The height difference between bottom of the scours and rim crest is up to 40 m. The largest plow marks are about 750 m wide. To date no observed modern icebergs including those from Antarctica have drafts in excess of c. 500 m. Taking into account maximum glacial sea level lowering of c. 120 m, the paleo-iceberg keel depth was at least 950 m. Due to the presence of the relatively shallow (< 700 m) sill of Davis Strait to the south, calving of these paleo-icebergs is thought to have occurred from an ice margin in the Baffin Bay region (Jakobshavn Isbræ paleo-ice stream?). The depth of occurrence (> 1000 m) and dimensions of the plow marks are concluded to be exceptional, and comparable to glacial scouring features reported from the Arctic Ocean. 相似文献
94.
Knut H. Andersen Philippe Jeanjean Dirk Luger Hans Petter Jostad 《Ocean Engineering》2005,32(7):845-863
Three centrifuge model tests were performed in normally consolidated Speswhite Kaolin to study the penetration of suction anchors in soft clay. The suction anchors could be penetrated by means of underpressure to a depth of about 12.4 to a little more than 14.5 times the diameter. When the anchors were penetrated by underpressure, all clay displaced by the skirt moved into the anchor. At a penetration depth of about half the maximum penetration depth, the volume of the soil heave inside the anchor actually increased more than the volume of the displaced clay. When a material coefficient of 1.5 against plug failure was mobilized, more than the clay displaced by the skirts had accumulated inside the anchor. The penetration resistance increased by 42 and 26% during rest periods of 4.5 and 0.8 days prototype time, respectively. Some uncertainty in the shear strength of the clay beds gave some uncertainty with respect to the interpretation, but the observed behaviour generally confirmed the theoretical analyses. 相似文献
95.
古丈县万岩重晶石矿点是开展湖南古丈地区矿产地质调查过程中新发现的矿点。本区重晶石矿属低温热液型矿床,成矿完全受裂隙控制。矿体主要赋存于震旦系上统金家洞组(Z2j)地层中,该地层中部的磷矿和底部的黄铁矿均在野外易于识别,且与重晶石矿体有着较为密切的空间关系,对找矿有着重要的指示作用。万岩重晶石矿点以东地区具一定的找矿前景。 相似文献
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赵家堡子金矿位于猫岭-卧龙泉金矿化集中区,是典型的中低温热液矿床。通过区域变质作用,使岩层中的Au、Ag等成矿元素活化,随着变质热液运移到有利的构造部位初步富集;通过应力作用,使岩石发生塑性变形,形成了北西向的韧性剪切带。同时,使Au、Ag等成矿元素再次活化转移、富集;通过后期构造岩浆的大面积侵入,形成了叠加在韧性剪切带之上的北西向韧-脆性断裂和北东向的脆性断裂,同时宏大的热源使地层中的Au再次活化、迁移、富集,同岩浆所带来的大量成矿物质一起在有利的构造部位富集成矿,是本区金矿的主要成矿阶段。 相似文献
98.
One of the primary threats to ocean ecosystems from plastic pollution is ingestion by marine organisms. Well-documented in seabirds, turtles, and marine mammals, ingestion by fish and sharks has received less attention until recently. We suggest that fishes of a variety of sizes attack drifting plastic with high frequency, as evidenced by the apparent bite marks commonly left behind. We examined 5518 plastic items from random plots on Kamilo Point, Hawai’i Island, and found 15.8% to have obvious signs of attack. Extrapolated to the entire amount of debris removed from the 15 km area, over 1.3 tons of plastic is attacked each year. Items with a bottle shape, or those blue or yellow in color, were attacked with a higher frequency. The triangular edges or punctures left by teeth ranged from 1 to 20 mm in width suggesting a variety of species attack plastic items. More research is needed to document the specific fishes and rates of plastic ingestion. 相似文献
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