Water salinity and productivity recorded by ostracod assemblages and their carbon isotopes since the early Holocene at Lake Qinghai on the northeastern Qinghai-Tibet Plateau, China
Water salinity and productivity recorded by ostracod assemblages and their carbon isotopes since the early Holocene at Lake Qinghai on the northeastern Qinghai-Tibet Plateau, China
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DOI：
10.1016/j.palaeo.2014.04.017
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发表时间：
2014-08
期刊：
影响因子：
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通讯作者：
Xiangzhong Li;Weiguo Liu
中科院分区：
文献类型：
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作者：
Xiangzhong Li;Weiguo Liu
青海湖是中国最大的咸水湖，是一个封闭的盆地型湖泊，盐度为16 g/L，位于亚洲季风控制区和西风急流影响区之间的半干旱敏感地带。在国际大陆钻探计划（ICDP）的支持下，青海湖于2005年使用ICDP GLAD 800钻探系统进行钻探。介形类2种，在1F钻孔的5.15 ~ 3.15 m（12.0-7.4 ka）深度范围内，仅发现了1F钻孔上部5.15 m（12.0-7.4 ka）的Limnocythere inopinata和Eucypris mareotica。mareotica和3.15 - 0 m（7.4ka-今）深度以L.介形虫Eucypris mareotica的存在与水的高盐度（超过30 g/L）有关，介形虫的优势种（Limnocythere inopinata）与青海湖地区的微咸水（3-16 g/L）有关（Li et al.，2010年）。现代介形类壳体中碳同位素的变化与青海湖湖底的水盐度和生产力有关（Li et al.，2012年）。在此基础上，利用1F孔介形虫化石种组合相对丰度的变化和介形虫壳中稳定碳同位素的变化以及其他已发表的数据（例如，介形虫Eucypris mareotica的单独出现及其壳中最高的平均δ 13 C值（-0.2 ‰）表明湖泊盐度和生产力非常高，这与全新世早期的高温和低湖平面（尽管降水急剧增加，但仍强烈蒸发）有关。介形虫的死亡数量。介形类的δ 13 C值最低（-2.0 ‰），表明全新世中期由于湖平面上升和温度下降，湖水盐度和生产力下降。最后，全新世晚期气温升高导致E/I值升高，湖平面下降，但湖水盐度和湖泊生产力逐渐增加。
Lake Qinghai, the largest saline lake in China, is a closed-basin lake with a salinity of 16 g/L and is situated in the sensitive semi-arid zone between the Asian monsoon-controlled area and the westerly jet stream-influenced area. With the support of the International Continental Drilling Program (ICDP), Lake Qinghai was drilled in 2005 using the ICDP GLAD800 drilling system. Two ostracod species, i.e.,Limnocythere inopinataandEucypris mareotica, were found only in the upper 5.15 m of the drilled core 1F, covering 12 ka, where the depths of 5.15 to 3.15 m (12.0–7.4 ka) are dominated byE. mareoticaand the depths of 3.15 to 0 m (7.4 ka–present) are dominated byL. inopinata.The presence of the ostracodEucypris mareoticawas related to the high salinity of the water (exceeding 30 g/L), and the dominant species of ostracod (Limnocythere inopinata) was related to the brackish water (3–16 g/L) in the Lake Qinghai area (Li et al., 2010). The changes in the carbon isotope in the modern ostracod shells were related to the water salinity and productivity on the lake bottom in Lake Qinghai (Li et al., 2012). On this basis, this study evaluated the changes in lake salinity and productivity and their relation to climatic change using changes in the relative abundances of ostracod fossil species assemblages and the stable carbon isotope in ostracod shells from core 1F and other published data (e.g., total organic carbon content, δ13CTOCand ice core δ18O).The single occurrence of ostracodEucypris mareoticaand the highest average δ13C values (− 0.2‰) in their shells indicated that the lake salinity and productivity were very high, a phenomenon that was related to the high temperature and low lake level (caused by intense evaporation even though the precipitation increased sharply) in the early Holocene. The deceased abundance of ostracodE. mareoticaand the lowest average δ13C values (− 2.0‰) in ostracod shells showed that the lake salinity and productivity decreased because of the increased lake level and decreased temperatures in the middle Holocene. Finally, the lake level decreased, but the water salinity and the lake productivity gradually increased because of the high E/I ratio related to the increased temperature in the late Holocene.