东天山地区冰川地貌演化及冰期研究

Developing an accurate and reliable chronological framework for glacial events and glacial landform evolution has traditionally been one of the most challenging problems in research in to Quaternary glaciations in China and internationally. New dating techniques, including CRN, OSL and ESR have been developed and refined over the past two decades and are now being used to provide reliable quantitative constraints on the ages of glacial sediments and landforms. Research on Quaternary glaciations has thus entered a new stage in which the emphasis is on accurate dating, with quantitative techniques augmenting conventional mapping and relative age dating. The Bogeda Peak area and the Tuomuerti Peak area are the largest centers of modern glaciation in the eastern Tianshan range in China. During Quaternary glacial-interglacial cycles these two areas were extensively and repeatedly glaciated. Spectacular landscapes, including erosional, depositional and glaciofluvial landforms from multiple glaciations are well preserved in valleys and on piedmonts. In this project we will use CRN, OSL and ESR dating techniques to determine the chronological record of glaciation preserved in these key areas. In particular we will test the hypothesis that there was a large glacial advance during middle marine oxygen isotope stage (mid-MIS) 3 that was similar in extent to the advance during the global Last Glacial Maximum (LGMG). We will also date Holocene glacier fluctuations and will use ArcGIS software and computer modeling to analyze glacial landform evolution in these two areas. Building on the achievements of traditional mapping, the addition of accurate dating will fill an important gap in research in to glacial landform evolution and Quaternary glaciations in the eastern Tianshan range, and will also provide new data for Chinese Quaternary glacial research. In addition, this study will provide results that will have important implications for palaeoclimatic modelling and palaeoenvironmental reconstructions in the Tianshan range, and that will advance understanding of tectonic uplift of the Tianshan ranges during the Quaternary.

精确年代学框架的建立是冰川地貌演化与冰期研究的难点，也是现阶段中国第四纪冰川研究的工作重点。CRN、OSL、ESR等可对冰川地形进行直接定年的测年技术的发展与应用，使第四纪冰川研究进入了以技术定年为主要特征的新阶段。博格达峰与托木尔提峰地区是东天山两大现代冰川作用中心。在第四纪冰期与间冰期旋回中，这些冰川均发生了规模较大的进退，在山谷与山麓带形成了形态清晰的冰川地形。我们将运用CRN、OSL、ESR等测年技术对这些地形进行综合定年，确定古冰川发育的时序、规模与性质；检测MIS3中期冰进事件的有无；提取全新世以来的冰川变化信息。应用计算机技术与ArcGIS空间分析软件对冰川地貌演化进行探讨。本研究可填补技术定年阶段东天山第四纪冰川研究的空白，为我国第四纪冰川研究增添新的内容。同时，本研究还可为天山的古气候模拟与古环境重建提供可靠的古冰川变化信息，为天山第四纪期间的构造抬升等研究提供理论支持。

本研究集中在东天山，包括两个最大的现代冰川作用中心——博格达峰与托木尔提峰。基于野外考察与遥感影像判读，获得博格达峰地区与托木尔提峰南坡的庙尔沟分别保存有5套与6套形态较为清晰的冰川地形。野外考察期间，课题组还采集了可用于CRN、OSL、ESR等测年技术进行直接定年的年代学样品。基于博格达峰地区的OSL与ESR测年结果，我们获得博格达峰地区保存有全新世期间的小冰期、新冰期、以及可对应于海洋同位素阶段（MIS）2的末次冰期晚阶段、可对应于MIS4的末次冰期早阶段以及可对应于MIS6的倒数第二次冰期的冰川演化序列。研究结果表明，晚第四纪期间，博格达峰地区的冰川演化有逐渐变小的趋势。其变化规律与同受西风环流控制的中亚其他地区的冰川演化较一致。. 在最东端的托木尔提峰南坡的庙尔沟流域，基于地貌地层学原理，我们发现保存在山谷中的5套冰碛可与博格达峰地区的5套冰碛呈一一对应关系。第6套为残存在分水岭或河间地上的残存冰碛地形。采集的CRN年代学样品已经完成了测年靶样的制备，预计近期可获得最终的年代测定结果。此外，我们对接近庙尔沟沟口，早期考察有争议的八大石进行了考察与成因研究，根据其岩性、岩块长轴与山体坡向的关系判定它们为山体巨大岩块滚落的结果，而非早期有些学者认为的冰川成因。. 本研究丰富了东天山地区第四纪冰川的研究内容。同时，本研究还可为天山的古气候模拟与古环境重建提供可靠的古冰川变化信息，为天山第四纪期间的构造抬升等研究提供理论支持。