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Geophysical survey on the tectonic and sediment distribution of Qinghai lake basin

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Science china Earth Sciences 2006年第8期49卷 851-861页

作者： AN Zhisheng1, wang Ping2, SHEN Ji3, zhang Yixiang2, zhang Peizhen4. wang {4.3, LI Xiaoqiang1, SUN Qianli1, SONG Yougui1, AI Li1, zhang Yechun2, JIANG Shaoren2, LIU Xingqi3 & wang Yong31. {4. of Earth environment, Chinese Academy of Sciences (CAS), Xi’an 710075, china 2. South china Sea {4. of Oceanology, CAS, Guangzhou 510301, china 3. nanjing institute of geography and limnology, CAS,{14., china 4. {4. of Geology, china Earthquake Administration, Beijing 100029, china institute of Earth environment Chinese Academy of Sciences (CAS) Xi’an China South china Sea institute of Oceanology CAS Guangzhou China nanjing institute of geography and limnology CAS Nanjing China institute of Geology China Earthquake Administration Beijing China

The intensive geophysical survey of Qinghai lake reveals the buried depth of lake sediments and their distribution features. The result indicates that there are three important inter- phases of Qinghai lake sediments: T1 is the rife interphase of the lake, above which sediments are spread all over the lake basin with roughly the same thickness; T5 is the interphase from which the neotectonic sedimentary cycle begins, and its above sedimentary environment is relatively stable; Tg is the base of the lake basin. Five west-northwest (WNW) fault belts defined the tectonic structure of Qinghai lake basin: the central hunch around Haixin Shan with two subbasins both in its north and south. The thickness of the lake sediments varies at different places, the thickest sediments are found within the two subbasins. According to the depth that the Sparker System can reach, sediment in the northern subbasin is deeper than 560 m, while sediment in the southern subbasin is deeper than 700 m. The correlation between the seismic sequence stratigraph and the lithology of onshore core shows that Qinghai lake sediments consist of muddy silt, clay silt, silty clay, gravel silty clay, etc.

关键词： sediment, geophysical survey, Qinghai lake.

Quantitative reconstruction of the paleosalinity at Qinghai lake in the past 900 years

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Chinese Science Bulletin 2004年第7期49卷 730-734页

作者： zhang Enlou1,2,SHEN Ji1,wang sumin1,YIN Yu1,ZHU Yuxin1 & XIA Weilan1 1.Key Laboratory of lake {4. and environment,{4. institute of geography and limnology,Chinese Academy of Sciences,Nan-jing 210008,china 2.Graduate School of Chinese Academy of Sciences,Beijing 100039,china Correspondence should be addressed to zhang Enlou(e-mail:elzhang@ ***) Key Laboratory of lake sediment and environment Nanjing Institute of Geography and Limnology Chinese Academy of Sciences Nanjing 210008 China Graduate School of Chinese Academy of Sciences Beijing 100039 China

Based on the function relationship between the shell length of Limnocythere inopinata and the salinity of its living water in Tibetan Plateau lakes, the paleosalinty of Qinghai lake in the past 900 years was reconstructed through the measurement of the adult body length of Limno-cythere inopinata. Meanwhile, the paleosalinity sequence of Qinghai lake during the same period was rebuilt by the Sr/Ca ratio of the shell of Eucypris inflata combined with the Sr/Ca ratio of living ostracod valves from the species of ge-nus Eucypris inflata and the host water. The paleosalinity results obtained by two different methods were compared and assessed in this paper. To check the result, it was also contrasted with other historical climatic sequences of this area including tree ring and ice core. It was shown that the paleosalinity sequence rebuilt by adult ostracod body length had high reliability, and the paleosalinity reconstruction method by trace elements of ostracod shells was not suitable for Qinghai lake. From the reconstructed paleosalinty se-quence of Qinghai lake, it can be found that low salinity during 1160—1290 AD showed the humid climate condition on the Mediaeval Warm Period in this area, while the high salinity during 14.0—154. AD, 1610—1670 AD and 1770—1850 AD which was corresponding to the three cold pulses of the Little Ice Age with a dry climate condition. And the high salinity in the latest several decades was consistent with re-cent warm and dry trends of the climate in this area. The good consistency of the reconstructed palaeosalinity sequence and the precipitation sequence in this area rebuilt by tree ring proves the reconstruction of past lake salinity is reliable.

关键词：青海湖数量重建成体特异湖浪介古盐度树轮海底沉积物介形亚纲动物

A subfossil chironomid-total phosphorus inference model for lakes in the middle and lower reaches of the Yangtze River

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Chinese Science Bulletin 2006年第17期51卷 2125-2132页

作者： zhang Enlou Alan Bedford Richard Jones SHEN Ji wang sumin TANG Hongqu nanjing institute of geography & limnology Chinese Academy of Sciences Nanjing 210008 China Natural Geographical and Applied Sciences Edge Hill College Ormskirk L394QP England Department of geography University of Exeter Exeter EX4 4RJEngland School of Biology Nankai University Tianjin 300017 China

The results of an investigation into the relationship between surface sediment subfossil chi- ronomid distribution and water quality are presented. Data from 30 lakes in the middle and lower reaches of the Yangtze River indicate that the nutrient gradi- ent was the major factor affecting the distribution of chironomids across these sites. Canonical corre- spondence analysis (CCA) revealed that of 12 sum- mer water environmental variables, total Phosphorus was most important, accounting for 20.1% of the variance in the chironomid data. This was significant enough to allow the development of quantitative in- ference models. A TP inference model was devel- oped using weighted averaging (WA), partial least squares (PLS) and weighted averaging partial least squares (WA-PLS). An optimal two-component WA-PLS model provided a high jack-knifed coeffi- cient of prediction for conductivity r 2jack = 0.76, with a low root mean squared error of prediction (RMSEPjack = 0.13). Using this model it is possible to produce long-term quantitative records of past water quality for lacustrine sites across the middle and lower reaches of the Yangtze River, which has important implications for future lake management and eco- logical restoration.

关键词：湖泊亚化石摇蚊推理模型长江中下游地区