新疆塔西河地区8Ma以来沉积环境演化及其构造意义  

SEDIMENTARY ENVIRONMENT EVOLUTION SINCE 8MaB.P. IN THE TAXIHE AREA,XINJIANG,NORTHWEST CHINA AND ITS TECTONIC SIGNIFICANCE

作　　者：吕红华[1] 李有利[1] 刘运明[1] 司苏沛[1] 赵洪壮[1] 

机构地区：[1]北京大学城市与环境学院,北京100871

出　　处：《第四纪研究》2008年第2期243-252,共10页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:40571013)资助

摘　　要：天山南北麓巨厚的新生代地层记录着天山构造隆升与沉积环境演化的历史。在对新疆塔西河剖面进行磁性地层研究的基础上，通过沉积学分析，确定自8．1Ma以来塔西河剖面存在4个沉积相组合，对应的沉积环境演化分为4个阶段：1）在8．10～5．75MaB．P．之前为浅湖沉积环境；2）在5．75—4．27MaB．P．为扇三角洲沉积环境；3）在4．27～3．44MaB．P．为滨浅湖沉积环境；4）在3．44MaB．P．之后为冲积扇沉积旋回期。塔西河剖面沉积环境演化、岩相与沉积速率的变化等共同揭示出天山自8．1MaB．P．以来先后经历了构造活动稳定期（〉5．75MaB．P．）、过渡期（5．75～3．44MaB．P．）以及快速强烈间歇性隆升期（〈3．44MaB．P．）等3个构造活动阶段，并且自3．44MaB．P．，构造活动有增强的趋势。When and how the Tianshan Mountains began to uplift has been controversial topics. Some previous studies analyzed the history of tectonic uplift solely based on the increase in accumulation rate based on magnetostratigraphy. Although the increase in accumulation rate could be resulted from tectonic uplift, the effect of climatic change should not be neglected. On the other hand, although the information on sedimentary environment is very useful to analyze the tectonic uplift,it was rarely used for the north piedmont of the Tianshan Mountains. The thick Cenozoic terrestrial sequence, which was deposited in southern and northern foreland basins of the Tianshan Mountains,provides us an opportunity to probe into the process of the sedimentary environment evolution and the history of tectonic uplift, and thus to understand the relationships between mountain building, erosion-deposition, and global or regional climate better. We thus carried out a magnetostratigraphic study with the hope to better understand the uplift history of the Tianshan Mountains and the process of the sedimentary environment in the region. In the north piedmont of the Tianshan Mountains, the Taxihe region is suitable for magnetostratigraphical and sedimentological study, as the north-flowing Taxihe River has cut across the Tugulu Anticline and the excellent outcrop in the valley provides us a unique opportunity to decipher the history of tectonic uplift since the terrigenous deposits. The studied section, about 1200m thick, lies about 28km southeast of Manasi and is located on the northern limb of the Tugulu Anticline. A total of 676 paleomagnetic samples were taken from the Taxihe section. One sample was selected from each sampled horizon. All selected samples （in total 301 ）were subject to stepwise ：hermal demagnetization in 13 - 17 steps in an ASC TD-48 oven with an internal residual field less than 10nT. Remnant magnetization was measured with a 2G cryogenic magnetometer at the Paleomagnetic Laboratory of the institute of Geome

关 键 词：沉积相 沉积环境演化 构造隆升 晚新生代 天山 

分 类 号：P539.3[天文地球—古生物学与地层学] P546[天文地球—地质学]