大兴安岭四方山天池全新世以来沉积物正构烷烃分布、单体碳同位素特征及古环境意义

发布时间：2018-04-08 23:20

本文选题：大兴安岭　切入点：四方山天池　出处：《湖泊科学》2017年02期

【摘要】：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 ka BP:区域有效湿度较高,陆生C_3植物中木本植物逐渐增加,湖泊水位上升、水面扩张,湖泊初级生产力增加,湖泊营养状态有所好转.四方山天池湖泊沉积物所记录的全新世以来区域气候环境演化历史,既与中国东北地区其他高分辨率气候记录有较好的一致性,也存在着差异性,表现出独有的区域气候特征.
[Abstract]:The distribution characteristics of n-alkanes and the composition of individual carbon isotopes in lake sediments since Holocene in Sifangshan Tianchi, central and northern part of Daxing'anling Mountains, were discussed and analyzed.The results show that the distribution range of n-alkane carbon number is n _ C _ (17) / n _ C _ (+) ~ (33). Most of the samples have a single-peak distribution, a few samples have a bimodal distribution, a few samples are characterized by a two-peak distribution, and a few samples are characterized by a two-peak distribution, and a few samples are characterized by a single-peak distribution, and a few samples are characterized by a single-peak distribution.The distribution of n-alkanes reveals that the organic matter in the sediments of Tianchi Lake in Sifangshan Mountain is derived from the common input of terrestrial plants and aquatic plants, and the contribution of terrestrial plants is the main contribution.Since the Holocene, the carbon isotopic values of long-chain n-alkanes in the sediments of Tianchi Lake, Sifangshan, have been gradually negative (未 ~ (13) C ~ (-1) C ~ (27) ~ (31)), which are consistent with the variation of solar radiation.The results show that the gradual increase of effective humidity in the region is mainly controlled by solar radiation, and the variation of lake water level is affected by the relative position of the western Pacific subtropical high and the Okhotsk high.Also subject to the southeast monsoon and the northeast monsoon power constraints.The primary productivity of the lake changed little, and the nutrient status of the lake was relatively stable. The effective humidity of the lake was higher than that of the previous stage. The woody plants in the terrestrial C3 plants expanded, the proportion of herbaceous plants contracted relatively, the lake water level rose and the water surface expanded.The primary productivity of the lake increased, the nutrient status of the lake improved, the effective precipitation of the region continued to increase, the proportion of herbaceous plants increased, the water level of the lake decreased, the water surface contracted, and the primary productivity of the lake decreased, and the proportion of herbaceous plants in the terrestrial C _ (3) plants increased.The nutrient status of the lake is depleted 52.4-0.9 ka BP: the regional effective humidity is higher, the woody plants in the terrestrial C3 plants increase gradually, the lake water level rises, the water surface expands, the primary productivity of the lake increases, and the nutrition status of the lake is improved.The evolution history of regional climate and environment recorded in Tianchi Lake sediments of Sifangshan Mountain since Holocene is not only consistent with other high-resolution climate records in Northeast China, but also different, showing unique regional climate characteristics.
【作者单位】：中国科学院地质与地球物理研究所新生代地质与环境重点实验室;
【基金】：国家自然科学基金项目(41272392,41572353,41320104006)资助
【分类号】：P597;P532

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