Pliocene land snail record from western Chinese Loess Plateau and implications for impacts of the summer insolation gradient between middle and low latitudes on the East Asian summer monsoon
Pliocene land snail record from western Chinese Loess Plateau and implications for impacts of the summer insolation gradient between middle and low latitudes on the East Asian summer monsoon
复制标题
中国西部黄土高原上新世陆螺记录及中低纬度夏季日照梯度对东亚夏季风影响的意义
DOI：
10.1016/j.gloplacha.2010.04.006
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发表时间：
2010-05-01
影响因子：
3.9
通讯作者：
Wu, Naiqin
中科院分区：
文献类型：
--
作者：
Li, Fengjiang;Wu, Naiqin
东亚季风可能早在古近纪/新近纪界线就已存在。然而，它的演化过程仍然不太为人所知，主要是由于缺乏长期的，连续的古环境记录。新近报道的中国西部黄土高原中新世（22- 6.2Ma）和晚中新世-上新世（7.1- 3.5Ma）黄土-古土壤序列为季风系统的演化提供了新的认识。然而，从这些沉积物的生物气候指标和随后的古季风重建的报道是罕见的。在这里，我们提出了一个上新世陆生软体动物记录从西部CLP和讨论可能的影响，隔离梯度对东亚夏季风。我们的研究结果表明，大多数峰值的优势温湿软体动物类群，Metodontia和Punctum，东亚夏季风的代理，大约对应于最大值的平均夏季太阳辐射梯度之间的中，低纬度以及一些最大值的35度N的太阳辐射，这表明夏季风和太阳辐射参数之间可能存在因果关系。两个温暖和潮湿的类群通过黄土-古土壤演替的频谱分析的总和的主要频率匹配的中，低纬度地区之间的平均夏季日照梯度变化在这个地质时期，提供了进一步的证据，这种因果关系。中低纬夏季平均太阳辐射梯度对大气环流（即东亚夏季风）有影响。中、低纬度夏季平均日照梯度的升高将增强东亚夏季风和海洋向内陆地区（包括CLP）的水汽和热量通量，为软体动物区系的扩张创造有利条件。因此，在CLP西部的黄土古土壤沉积的软体动物记录提供了证据，在上新世的东亚季风系统的发展的太阳辐射梯度的影响。(C)2010爱思唯尔有限公司版权所有。
The East Asian monsoon probably existed as early as at the Palaeogene/Neogene boundary. However, its evolutionary process is still less well known owing mainly to the lack of long, continuous palaeoenvironmental records. The recently reported Miocene (22-6.2 Ma) and late Miocene-Pliocene (7.1-3.5 Ma) loess-palaeosol sequences from the western Chinese Loess Plateau (CLP) provide new insights into the evolution of the monsoon system. However, reports on the bioclimatic indicators from these deposits and the subsequent reconstruction of the palaeomonsoon are rare. Here we present a Pliocene terrestrial mollusk record from the western CLP and discuss the possible impact of isolation gradients on the East Asian summer monsoon. Our results show that most peak values of the dominant thermo-humidiphilous mollusk taxa, Metodontia and Punctum, a proxy of the East Asian summer monsoon, approximately correspond to maxima of mean summer insolation gradient between middle and low latitudes as well as some maximum values of the 35 degrees N insolation, suggesting a possible causal link between the summer monsoon and the insolation parameters. The major frequencies from spectrum analysis of the sum of the two warmth- and moisture-loving taxa through the loess-palaeosol succession match those obtained from the mean summer insolation-gradient variations between middle and low latitudes over this geological period, providing further evidence for such a causal relationship. Mean summer insolation gradient between middle and low latitudes could influence atmospheric circulation (in the present condition the East Asian summer monsoon). Any elevated mean summer insolation gradients between middle and low latitudes would have intensified the East Asian summer monsoon and the flux of moisture and heat over the oceans to the interior region including the CLP, creating favorable conditions for the expansion of the mollusk fauna. As such, the mollusk record from the loess palaeosol deposits in the western CLP provides evidence for insolation-gradient impacts on the development of the East Asian monsoon system in the Pliocene. (C) 2010 Elsevier B.V. All rights reserved.