【摘要】 天山北麓河流阶地序列及其年代一直是悬而未决的问题。根据详细的野外工作,确定天山北麓发育7级河流阶地,其中T7、T6、T5及T2等主要阶地为河流切割先期冲积扇而形成,与4级阶地对应的4期冲积扇分别为F1、F2、F3与F4。由于天山北麓构造隆升向盆地方向迁移,冲积扇呈串珠状发育,背斜带间发育的冲积扇平面形态则由于南北背斜的限制而变得不规则。基于黄土—古土壤序列对比分析、ESR与OSL测年以及前人研究成果,确定天山北麓河流下切形成T7、T6、T5及T2等阶地的时间分别为约0.54MaBP、0.3￣0.2MaBP、28￣8kaBP和全新世早期。阶地年代表明,天山北麓3级主要阶地T7、T6、T5及对应冲积扇发育与天山更新世3个冰期间冰期旋回基本对应。更多还原

【Abstract】 The northern piedmont of the Tianshan Mountains, which is characterized by three parallel ridges of anticlines, known as Fold-and-Thrust zones I-III from the mountains towards the foreland basin, and north-flowing rivers, is a typical region containing many scientific problems attracting a lot of geologists and geographers. Under the special geological setting, the terraces developing along these rivers contain a lot of information on climatic changes and tectonic movement. However, previous studies on fluvial terraces in the northern piedmont of the Tianshan Mountains are still divergent. This work tries to solve the problem and well understand the sequences and ages of fluvial terraces along the northern piedmont of the Tianshan Mountains. The seven fluvial terraces named as T1 to T7 developed along major river channels in the northern piedmont of the Tianshan Mountains, and some main and consecutive terraces correspond to some fans. The fans corresponding to T7, T6, T5 and T2 are respectively named as F1, F2, F3 and F4. Because the center of the upheaval migrated from south to north in the process, some fans developed one by one. But the limit of the anticlines leads to the anomalistic shape of some fans between two anticlines. According to the ESR age, OSL age, and loess-paleosol series, the highest terrace (T7), corresponding to the oldest alluvial fan (F1) which is covered by thick loess and strongly dissected, is dated as 0.54 Ma BP. The higher terrace (T6) corresponds to F2, and the surface of T6 and F2 is also covered by thick loess and dissected by gullies, some of which were abandoned. The age of T6 is estimated as 0.3-0.2 Ma on the basis of the ESR age and loess-paleosol series.更多还原