通过分析河西走廊花海古湖泊沉积物中的盐类矿物组成，结合年代序列，重建了花海晚冰期以来湖泊演化过程及其对气候变化的响应。结果表明：晚冰期及新仙女木时期，花海湖泊以芒硝沉积为主，属硫酸盐型湖泊，湖水的盐度较高且周期性波动...通过分析河西走廊花海古湖泊沉积物中的盐类矿物组成，结合年代序列，重建了花海晚冰期以来湖泊演化过程及其对气候变化的响应。结果表明：晚冰期及新仙女木时期，花海湖泊以芒硝沉积为主，属硫酸盐型湖泊，湖水的盐度较高且周期性波动频繁；全新世早期（10.47 cal ka BP以前），湖泊以洪泛堆积和风成沉积为主，揭示了湖泊萎缩、甚至干涸；全新世早期至全新世中期（10.47～8.87 cal ka BP）盐类矿物以碳酸盐沉积为主，为碳酸盐型湖泊，湖水淡化，湖泊水位开始逐渐回升；全新世中期（8.87～5.50 cal ka BP）盐类矿物呈现一定的波动变化，其中，8.8 cal ka BP 时期盐类矿物以硫酸盐沉积为主，湖泊由碳酸盐型转化为硫酸盐型，湖水咸化，盐度升高；随后盐类矿物以碳酸盐沉积为主，湖泊由硫酸盐型转化为碳酸盐型，湖水盐度降低、湖泊扩张；全新世中晚期（5.50 cal ka BP以来）出现沉积间断，表明中晚全新世时期湖泊逐渐萎缩。在全新世期间，花海湖泊千年尺度演化过程揭示了该区域气候干湿状况受亚洲季风和西风共同控制的影响。展开更多
High precision elevation measurements using DGPS were carried out along three representative tran- sects for the "Great Ear" area, a dry salt lake within the Lop Nor basin. Results indicate that the Lop Nor ...High precision elevation measurements using DGPS were carried out along three representative tran- sects for the "Great Ear" area, a dry salt lake within the Lop Nor basin. Results indicate that the Lop Nor basin is only 5.2 m deep and its lowest point occurs at the center of the "Great Ear". In addition, the basin is asymmetric - steeper in the southwest (0.19‰) and gentler in the northeast (0.09‰). Points along the same "Great Ear" ring were found to have an identical elevation value, but different when from different ones (lower towards the center). The spacing of the "Great Ear" rings was found to be closely related with the surface steepness. The closer the "Great Ear" rings are spaced, the steeper the ground surface, and vice versa. These findings support the argument that the "Great Ear" rings are the former shoreline trails left behind by Lop Nor water during the last few episodes of recession towards its total dry up. A comprehensive analysis of the high precision elevation data, historical accounts, aerial and satellite photographs and imagery, and official topographic maps of the study area suggests that the "Great Ear" area in the Lop Nor basin was incorrectly mapped as being covered by a great body of water on the 1963 topographic maps. A re-interpretation of the 1958 aerial photographs and newer remote sensing imagery indicated that the "Great Ear" ring structure was already in place in 1958 and it continued to appear on the subsequent remote sensing data without any major changes. It is estimated that lake water in the "Great Ear" area of the Lop Nor basin disappeared between the late 1930s and early 1940s.展开更多
对位于大兴安岭中北段四方山天池全新世以来湖泊沉积物中正构烷烃的分布特征及其单体碳同位素组成进行了讨论分析.结果表明,正构烷烃碳数分布范围为nC_(17)~nC_(33),绝大多数样品具有单峰型的分布特征,少数样品呈现双峰型分布特征,单峰...对位于大兴安岭中北段四方山天池全新世以来湖泊沉积物中正构烷烃的分布特征及其单体碳同位素组成进行了讨论分析.结果表明,正构烷烃碳数分布范围为nC_(17)~nC_(33),绝大多数样品具有单峰型的分布特征,少数样品呈现双峰型分布特征,单峰型以nC_(27)为主峰,双峰型分布中前峰群以nC_(21)为主峰、后峰群以nC_(27)为主峰;短链正构烷烃(<nC_(21))奇偶优势不明显,中链(n C23~n C25)和长链正构烷烃(>nC_(27))具有明显的奇碳优势;正构烷烃的分布特征揭示四方山天池湖泊沉积物中的有机质来源于陆生植物和水生植物的共同输入,并以陆生植物贡献为主.全新世以来,四方山天池湖泊沉积物中长链正构烷烃单体碳同位素值(δ^(13)C_(27~31))逐渐偏负,与太阳辐射的变化表现出明显的一致性,表明在轨道尺度上该区域的有效湿度的逐渐增加主要受太阳辐射的控制,湖泊水位的变化则既受到西太平洋副热带高压和鄂霍次克海高压相对位置的影响,又受到东南季风和东北季风势力强弱的制约.根据多种气候代用指标的变化,全新世以来四方山天池湖泊环境及其区域气候演化可以划分为5个阶段:(1)11.2-8.0 ka BP:区域有效湿度较低,陆生C_3植物中木本植物比例略有增加,湖泊水位频繁波动,湖泊初级生产力下降,湖泊营养状态发生贫化;(2)8.0-6.4 ka BP:区域有效湿度增加,陆生C_3植物中草本植物比例略有增大,湖泊水面收缩、水位下降,湖泊初级生产力变化不大,湖泊营养状态较为稳定;(3)6.4-3.4 ka BP:区域有效湿度比上一阶段更高,陆生C_3植物中木本植物扩张,草本植物比例相对收缩,湖泊水位上升、水面扩大,湖泊初级生产力增加,湖泊营养状态发生好转;(4)3.4-2.4 ka BP:区域有效降水量继续增加,陆生C_3植物中草本植物比例升高,湖泊水位下降、水面收缩,湖泊初级生产力下降,湖泊营养状态发生贫化;(5)2.4-0.9 k展开更多
文摘通过分析河西走廊花海古湖泊沉积物中的盐类矿物组成，结合年代序列，重建了花海晚冰期以来湖泊演化过程及其对气候变化的响应。结果表明：晚冰期及新仙女木时期，花海湖泊以芒硝沉积为主，属硫酸盐型湖泊，湖水的盐度较高且周期性波动频繁；全新世早期（10.47 cal ka BP以前），湖泊以洪泛堆积和风成沉积为主，揭示了湖泊萎缩、甚至干涸；全新世早期至全新世中期（10.47～8.87 cal ka BP）盐类矿物以碳酸盐沉积为主，为碳酸盐型湖泊，湖水淡化，湖泊水位开始逐渐回升；全新世中期（8.87～5.50 cal ka BP）盐类矿物呈现一定的波动变化，其中，8.8 cal ka BP 时期盐类矿物以硫酸盐沉积为主，湖泊由碳酸盐型转化为硫酸盐型，湖水咸化，盐度升高；随后盐类矿物以碳酸盐沉积为主，湖泊由硫酸盐型转化为碳酸盐型，湖水盐度降低、湖泊扩张；全新世中晚期（5.50 cal ka BP以来）出现沉积间断，表明中晚全新世时期湖泊逐渐萎缩。在全新世期间，花海湖泊千年尺度演化过程揭示了该区域气候干湿状况受亚洲季风和西风共同控制的影响。
基金the National Natural Science Foundation of China (Grant No. 40671080)the Program for Changjiang Scholars and Innovative Research Team in University (Grant No. IRT0412)the Key Subject of Soil Science Program in Xinjiang
文摘High precision elevation measurements using DGPS were carried out along three representative tran- sects for the "Great Ear" area, a dry salt lake within the Lop Nor basin. Results indicate that the Lop Nor basin is only 5.2 m deep and its lowest point occurs at the center of the "Great Ear". In addition, the basin is asymmetric - steeper in the southwest (0.19‰) and gentler in the northeast (0.09‰). Points along the same "Great Ear" ring were found to have an identical elevation value, but different when from different ones (lower towards the center). The spacing of the "Great Ear" rings was found to be closely related with the surface steepness. The closer the "Great Ear" rings are spaced, the steeper the ground surface, and vice versa. These findings support the argument that the "Great Ear" rings are the former shoreline trails left behind by Lop Nor water during the last few episodes of recession towards its total dry up. A comprehensive analysis of the high precision elevation data, historical accounts, aerial and satellite photographs and imagery, and official topographic maps of the study area suggests that the "Great Ear" area in the Lop Nor basin was incorrectly mapped as being covered by a great body of water on the 1963 topographic maps. A re-interpretation of the 1958 aerial photographs and newer remote sensing imagery indicated that the "Great Ear" ring structure was already in place in 1958 and it continued to appear on the subsequent remote sensing data without any major changes. It is estimated that lake water in the "Great Ear" area of the Lop Nor basin disappeared between the late 1930s and early 1940s.
文摘对位于大兴安岭中北段四方山天池全新世以来湖泊沉积物中正构烷烃的分布特征及其单体碳同位素组成进行了讨论分析.结果表明,正构烷烃碳数分布范围为nC_(17)~nC_(33),绝大多数样品具有单峰型的分布特征,少数样品呈现双峰型分布特征,单峰型以nC_(27)为主峰,双峰型分布中前峰群以nC_(21)为主峰、后峰群以nC_(27)为主峰;短链正构烷烃(<nC_(21))奇偶优势不明显,中链(n C23~n C25)和长链正构烷烃(>nC_(27))具有明显的奇碳优势;正构烷烃的分布特征揭示四方山天池湖泊沉积物中的有机质来源于陆生植物和水生植物的共同输入,并以陆生植物贡献为主.全新世以来,四方山天池湖泊沉积物中长链正构烷烃单体碳同位素值(δ^(13)C_(27~31))逐渐偏负,与太阳辐射的变化表现出明显的一致性,表明在轨道尺度上该区域的有效湿度的逐渐增加主要受太阳辐射的控制,湖泊水位的变化则既受到西太平洋副热带高压和鄂霍次克海高压相对位置的影响,又受到东南季风和东北季风势力强弱的制约.根据多种气候代用指标的变化,全新世以来四方山天池湖泊环境及其区域气候演化可以划分为5个阶段:(1)11.2-8.0 ka BP:区域有效湿度较低,陆生C_3植物中木本植物比例略有增加,湖泊水位频繁波动,湖泊初级生产力下降,湖泊营养状态发生贫化;(2)8.0-6.4 ka BP:区域有效湿度增加,陆生C_3植物中草本植物比例略有增大,湖泊水面收缩、水位下降,湖泊初级生产力变化不大,湖泊营养状态较为稳定;(3)6.4-3.4 ka BP:区域有效湿度比上一阶段更高,陆生C_3植物中木本植物扩张,草本植物比例相对收缩,湖泊水位上升、水面扩大,湖泊初级生产力增加,湖泊营养状态发生好转;(4)3.4-2.4 ka BP:区域有效降水量继续增加,陆生C_3植物中草本植物比例升高,湖泊水位下降、水面收缩,湖泊初级生产力下降,湖泊营养状态发生贫化;(5)2.4-0.9 k
