Late Glacial and Holocene development of Lake Donggi Cona, north-eastern Tibetan Plateau, inferred from sedimentological analysis
Late Glacial and Holocene development of Lake Donggi Cona, north-eastern Tibetan Plateau, inferred from sedimentological analysis
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DOI：
10.1016/j.palaeo.2012.04.013
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发表时间：
2012-06
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影响因子：
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通讯作者：
S. Opitz;B. Wünnemann;Bernhard Aichner;E. Dietze;K. Hartmann;U. Herzschuh;J. Ijmker;F. Lehmkuhl
中科院分区：
文献类型：
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作者：
S. Opitz;B. Wünnemann;Bernhard Aichner;E. Dietze;K. Hartmann;U. Herzschuh;J. Ijmker;F. Lehmkuhl
通过对青藏高原东北部东吉科纳湖沉积物的研究，探讨了19 kyr以来该湖沉积环境与气候和非气候变化的关系。今天的湖泊充满了一个30× 8公里大，95米深的构造盆地，与昆仑断层有关。该研究是在一个通过湖泊流域的沉积物样带上进行的，以获得一个完整的时空环境变化的画面。所回收的沉积物部分为细层状，由钙质泥和不同量的碳酸盐泥晶、有机质、碎屑粉砂和粘土组成。沉积学，地球化学和矿物学数据的基础上，多达五个岩性单位（LU）可以区分，记录不同阶段的湖泊系统的发展。最低的LU与湖相泥以上的基底砂的发病表明，湖泊水位至少比现在的水平低39米，并开始上升后，19 ka，可能在响应区域冰川消退。此时的湖泊环境以碎屑沉积物的流入和硅质碎屑沉积物的沉积为特征。在两个沉积物岩心，向上粒度粗化文件湖平面下降后，13卡尔ka BP，可能与晚冰期新仙女木stadial。从11.5到4.3 cal ka BP，深水取心点沉积物岩心的粒度细化和最近的东岐科纳边缘湾的文学的岩心（水深2 m）湖相沉积的开始记录了早全新世至中全新世期间湖平面上升到至少现代水平。此外，高生物生产力和碳酸盐泥晶的显著降水与夏季季风影响增强相关的温暖潮湿的气候条件是一致的。在4.3cal ka BP的湖泊系统从文石-方解石为主的系统，向一个完全开放的水文湖泊系统的变化。此外，较年轻的富含粘土的沉积物没有层压，也没有任何成岩硫化物，这表明有充分的通风条件，而且普遍没有湖泊分层。湖泊历史上的这一转折点可能意味着对太阳强迫气候冷却的阈值响应，或者对非气候触发的响应，例如侵蚀事件或引发强烈地震的构造脉冲，这很难从我们的数据库中确定。
Sediments of Lake Donggi Cona on the northeastern Tibetan Plateau were studied to infer changes in the lacustrine depositional environment, related to climatic and non-climatic changes during the last 19kyr. The lake today fills a 30×8km big and 95m deep tectonic basin, associated with the Kunlun Fault. The study was conducted on a sediment-core transect through the lake basin, in order to gain a complete picture of spatio-temporal environmental change. The recovered sediments are partly finely laminated and are composed of calcareous muds with variable amounts of carbonate micrite, organic matter, detrital silt and clay. On the basis of sedimentological, geochemical, and mineralogical data up to five lithological units (LU) can be distinguished that document distinct stages in the development of the lake system. The onset of the lowermost LU with lacustrine muds above basal sands indicates that lake level was at least 39m below the present level and started to rise after 19ka, possibly in response to regional deglaciation. At this time, the lacustrine environment was characterized by detrital sediment influx and the deposition of siliciclastic sediment. In two sediment cores, upward grain-size coarsening documents a lake-level fall after 13cal ka BP, possibly associated with the late-glacial Younger Dryas stadial. From 11.5 to 4.3cal ka BP, grain-size fining in sediment cores from the profundal coring sites and the onset of lacustrine deposition at a litoral core site (2m water depth) in a recent marginal bay of Donggi Cona document lake-level rise during the early to mid-Holocene to at least modern level. In addition, high biological productivity and pronounced precipitation of carbonate micrites are consistent with warm and moist climate conditions related to an enhanced influence of summer monsoon. At 4.3cal ka BP the lake system shifted from an aragonite- to a calcite-dominated system, indicating a change towards a fully open hydrological lake system. The younger clay-rich sediments are moreover non-laminated and lack any diagenetic sulphides, pointing to fully ventilated conditions, and the prevailing absence of lake stratification. This turning point in lake history could imply either a threshold response to insolation-forced climate cooling or a response to a non-climatic trigger, such as an erosional event or a tectonic pulse that induced a strong earthquake, which is difficult to decide from our data base.