中文摘要：

黄土-古土壤序列、红粘土等风尘堆积由于其本身蕴含着丰富的气候信息而成为研究新生代古气候（东亚季风）演化的理想载体。已有的研究表明大面积连续分布的风尘堆积主要出露在黄土高原及邻区。新近，在青藏高原北缘阿尔金山地区发现了一套厚约88.4m的新近纪红粘土堆积（彩虹沟组），红粘土本身沉积特征及其与黄土高原典型风成沉积物的诸多相似性表明其为风成产物。生物化石约束下的磁性地层学表明该风尘堆积形成于13.0~2.6Ma。根据沉积物的载磁矿物、磁化率系统差异可将该序列分为上下两段：下段（13.0~11.5Ma）载磁矿物以磁铁矿为主，磁化率值总体较高（平均值为15×10-8m3/kg）且变化频繁，指示了总体湿润但干湿交替明显的古气候；上段（10.3~2.6Ma）稳定的磁化率低值（平均值为9.5×10-8m3/kg，主要载磁矿物为赤铁矿）为干旱少雨背景下的产物。11.5~10.3Ma（过渡段）的磁化率降低及载磁矿物的转变为区域干旱化增强的反映。该次干旱化事件是在全球变冷与副特提斯洋退出的总体背景下，高原北部逐渐向北扩展引起的。

英文摘要：

Aeolian deposits, such as loess/paleosol and red clay, have been widely used for the reconstruction of paleoclimate（such as the evolution of East Asian Monsoon）.Previous studies have more focused on the aeolian deposit on Chinese Loess Plateau（CLP）, the largest and most extensive area of such deposits in China.Here, we describe and interpret an 88.4-m-thick Neogene aeolian sequence in the lower part of Caihonggou Formation containing 40 visually-defined, brownish-red clay and gray caliche nodule layers in the eastern Xorhol Basin, northeast of the Tibetan Plateau.The study section is located in the north Xorkol Basin of Ruoqiang Town, Ruoqiang County, Xinjiang, with starting coordinates and elevation of 38°57＇09＂N, 91°30＇41＂E and 3652m a.s.l., as well as the ending ones of 38°55＇30.65＂N, 91°30＇57.21＂E and 3635m a.s.l.Both sedimentary features and similarities to the typical aeolian deposit on the CLP point to its eaolian origin.Typical samples from different parts of the sequence have been used for rock magnetism analysis and distinguished characters have been explored along the sequence.Based on the constraints of contact relation and mammalian fossils （Stephanocemas？ sp.）, magnetostratigraphic results show that the sequence spans from chron C5An.4r to chron C2r, indicating that the sequence was deposited between ca.13.0Ma and 2.6Ma.The sequence can be divided into two parts with different climate conditions according to magnetic susceptibility and carriers of magnetic remanence：the lower part（13.0~11.5Ma）indicates a more changeable climate with higher magnetic susceptibility values（average 15×10-8m3/kg） dominated by magnetite; the upper part（10.3~2.6Ma） reflects a drier climate with lower, stable magnetic susceptibility values （average 9.5×10-8 m3/kg） mainly arising from hematite.Transition stage（11.5~10.3Ma）in the middle is characterized for sharp decrease of magnetic susceptibility.Our results indicate that an episode of intensified aridity in the Asia