8 Ma以来准噶尔盆地西缘白杨河冲-洪积扇ZK1钻孔剖面沉积环境演变

准噶尔盆地西缘白杨河冲洪积扇发育典型，但其环境过程问题亟待解决。在该扇西缘ZK1剖面（137 m深）古地磁定年基础上，提取粒度、磁化率、有机质、碳酸钙、孢粉、砂粒微形态、矿物成分等样品信息，综合分析表明：8 Ma以来研究区环境主要在中纬度内陆干旱荒漠至荒漠草原范围演变，包括2个阶段6个亚阶段：阶段Ⅰ（8.1~5.3 Ma）主要为湖泊期，包括亚阶段1（8.1~7.2 Ma）浅湖、亚阶段2（7.2~6.9 Ma）戈壁和亚阶段3（6.9~5.3 Ma）滨湖；阶段Ⅱ（5.3 Ma至今）为冲洪积扇期，由亚阶段4（5.3~3.6 Ma）扇体开始发育形成的干冷扇缘、亚阶段5（3.6~1.1 Ma）为较干冷环境下的第二次快速成扇期和亚阶段6（1.1 Ma至今）最干冷环境下的第三次极快成扇期组成。该扇主要形成于5.3 Ma以来，主要经历了5.3 Ma、3.6 Ma、1.1 Ma等3次成扇期。其发育阶段和环境演化与晚新生代古地中海Messinian期干化事件、半球乃至全球阶段性降温、青藏高原隆升及其远程效应等关系密切。

Depositional environment evolution of ZK1 drilling section since 8 Ma in the Baiyanghe alluvial fan on the western margin of Junggar Basin,NW China

The alluvial fans and their stratigraphies, widely developed in the inland basin-mountain transition zone of Northwest China, are good records of regional environmental evolution and the major geological and palaeo-environmental events of the Late Cenozoic, such as, the inland aridification of Central Asia, the uplift of the Qinghai-Tibet Plateau and its effects etc. Among the numerous alluvial fans distributed across the foothills of the western margin of the Junggar Basin, the Baiyanghe alluvial fan is typical and relatively large, provides a favorable geomorphological and stratigraphic setting for investigating the environmental evolution and strongtium-rich water and soil of this region. At present, the environmental evolution of the fan demand deeperly studies. Here by field investigation the paper is mainly on the paleomagnetic chronology and palaeo-environmental reconstruction of ZK1 (137 m depth) profile(46°18'59.04″N, 84°43'45.11″E) drilled in the western margin of the Baiyanghe alluvial fan.