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藏南沉错地区近1400年来的介形类与环境变化 总被引:7,自引:0,他引:7
通过分析藏南沉错CC1孔的介形类动物群所提供的古环境信息,探讨近1400年来的湖泊演化。CC1孔介形类共计7属15种。据其属种,数量及生态特征,可划分为7个组合,同时发现1400年来沉错环境变化可分为3个时期:(1)公元6世末-14世纪下半叶沉错主要为较深水湖,其中大约在708-780年和1199-1213年湖泊迅速扩大加深;(2)14世纪下半叶-19世纪末沉错主要为浅水湖,其中大约在1454-1525年,1645-1670年和1803-1891年3个时段湖泊强烈退缩,环境极不稳定,而大约在1731-1803年湖泊发生逆向转化,湖水增多,湖面抬升;(3)19世纪末至今沉错由较深水湖转变为浅水湖,20世纪60年代以前为较深水湖,其中大约在1929-1935年湖泊急剧加深,20世纪70年代以来湖泊退缩,湖水变浅。 相似文献
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Environmental changes reflected by the lake sediments of the South Hongshan Lake, Northwest Tibet 总被引:6,自引:1,他引:6
The 1.07-m long lake core with 1 cm interval cutting, which was obtained by drilling in the South Hongshan Lake of Northwest Tibet, was dated by the 210Pb and 137Cs methods, and a 150-year consecutive lake sedimentary sequence (1840─1997) with 1.4 year resolution was obtained. Some environmental proxies, such as the total organic carbon (TOC), total nitrogen (TN), ratio of TOC to TN (TOC/TN), trace chemistry elements (TCE), CaCO3, grain size, richness of ostracoda etc. showed that they are of well coincidence. These results implied that the environmental background varied from the cold-wet period in the late 19th century, to the warm-wet period from the end of the 19th century to the 1920s and to the warm-dry period since the 1920s. There were sub-variations since the 1920s: the cold-dry/warm-wet fluctuation from 1922 to 1960, the intensively warm-dry period since 1960 with a short cold-wet period in the mid-1970s to the end of the 1980s. The humid period from the mid-1970s to the end of the 1970s and the dry period beginning from the early 1980s were well documented by climatic data of the nearby weather station records while the grain size was well correlated to the annual precipitation. Compared with the records from Guliya ice core in the same area, the TOC proxy in the lake core indicating warm/cold conditions well corresponded to the ( 18O records representing temperature variations in the ice core. However, the proxies with dry/wet significance in the lake core were different from the variations of snow accumulation reflected by the ice core. It can be concluded that the chosen environmental proxies have clear environmental significance and the lake sediments can reflect climatic and environmental changes at high-resolution. 相似文献
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西汉古黄河三角洲初探 总被引:3,自引:1,他引:3
根据历史文献、地貌和第四纪地质调查以及卫星影象图等分析,探讨了西汉时期黄河河口位置、三角洲范围及其沉积特征。指出西汉古黄河三角洲的沉积特征与近代黄河三角洲相似,每年进入主河口的泥沙达2.7×l08t左右。 相似文献
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南极乔治王岛长城湾活有孔虫和死有孔虫的比较分析 总被引:1,自引:0,他引:1
本文对中国首次南极考察队在长城湾采集的海底底质样品作了有孔虫分析,初步查明有孔虫属种,并揭示了长城湾有孔虫组合和分布规律。 相似文献
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天津平原第四纪微体化石群及其古地理意义 总被引:7,自引:1,他引:6
近年来,我国地质、地理和考古工作者对渤海湾沿岸平原第四纪海侵问题进行了大量的研究。李凤林等提出中更新世以来渤海湾北岸至少有4—5次海侵,有3次海侵曾抵达玉田、宝坻等县境。天津自然博物馆等单位提出了7000年前海侵的最大范围。随 相似文献
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根据对AB-67钻孔岩芯中微体动物群的分析,本文讨论了北极阿拉斯加巴罗地区过去450年的气候环境变迁历史。 相似文献
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