摘要
盐池位于祁连山北麓的河西走廊中段,是研究长时间尺度亚洲夏季风影响区北部边界变化的关键区域。现代气候学证据显示,亚洲夏季风的水汽输送限于祁连山东部地区,但是在全新世长尺度气候变化的背景下,夏季风西北边界是否会南北向移动是一个关键的科学问题。本研究对盐池古湖泊沉积物进行了孢粉浓缩物AMS14C测年,并分析了岩性、粒度、矿物及地球化学等指标。年代结果显示剖面下部湖相沉积层主要形成于晚冰期和早全新世期间,配合指标研究,该时期盐池沉积物体现了湖泊扩张的特征;剖面中部湖相沉积层主要形成于早、中全新世过渡时期,该段年代序列混乱,且普遍偏老,与之对应的指标结果显示湖泊开始退缩。湖泊退缩过程中,湖泊边缘附近水动力作用较强,导致再搬运及再沉积作用明显,从而使得年代结果较老且混乱。中全新世以来盐池古湖泊退缩明显,沉积速率较低,以泥沼相沉积为主。盐池晚冰期以来湖泊演化过程与青藏高原区和典型季风区的古气候记录具有一致性,整体表现为晚冰期及早全新世湖泊扩张,中、晚全新世期间湖泊退缩明显,这种变化模式与西风区湖泊演化存在差异,显示了千年尺度亚洲夏季风对该区域的影响,证明了夏季风北部边界摆动的事实。
Yanchi Lake is located in the northern Qilian Mountains and the central Hexi Corridor, which is a key research area for the long-term northern boundary changes of the Asian summer monsoon. Modem climate research shows that the Asian summer monsoon moisture transport is limited to the eastern part of Qilian Mountains. On the Holocene millennial-scale, whether the northwest boundary of the summer monsoon varies according to climate change is a key scientific issue. Paleoclimatic data, including AMS ~4C dates of pollen concentrates, lithology, grain-size, mineral composition and geochemical proxies were acquired from lake sediments of Yanchi Lake. The chronological results show that the lower part of the lacustrine section is formed mainly in the late glacial and early Holocene period, while the proxies＇ data indicate that the lake expansion is associated with high contents of mineral salts. The middle part of this section is formed during the transition period of the early and middle Holocene. The AMS ~4C ages of pollen concentrates from the middle part of the section are generally older than those from the lower part. Proxy data indicate that the lake began to retreat since the transition period of the early and middle Holocene. When the lake level is relatively low, the location of the lacustrine section is near the lake edge. Reworking effects of lake sediments are strong on the lake edge; therefore, the ages are relatively old. Since the mid-Holocene, Yanchi Lake retreated significantly and the deposition rate dropped obviously. The Yanchi Lake record is consistent with the late glacial lake records on the Qinghai-Tibet Plateau and in the typical monsoon domain, which shows the late glacial and early Holocene lake expansion and the strong Asian summer monsoon. The long-term monsoonal pattern is different from that of the lake evolution in Central Asia on the Holocene millennial-scale. This study suggests that the monsoon has impacts on the northwest margin of the summer monsoon, and also proves the fact that
出处
《地理学报》
EI
CSCD
北大核心
2013年第7期933-944,共12页
Acta Geographica Sinica
基金
国家自然科学基金(41001116)
兰州大学中央高校基本科研业务费专项资金项目(lzujbky-2013-127
lzujbky-2013-129)共同资助~~
关键词
盐池
亚洲夏季风
全新世
晚冰期
湖泊沉积物
季风边缘区
Yanchi Lake
Asian summer monsoon
Holocene
the late glacial
lakesediments
monsoon marginal zones
