柴达木盆地西部地区渐新世下干柴沟组上段盐湖沉积特征

利用大量地质及地球化学资料，开展了柴达木盆地西部地区渐新世下干柴沟组上段盐湖沉积特征研究，重点识别岩石类型，恢复古沉积环境，建立沉积模式，探讨控制因素。研究认为：盐湖环境主要发育两大类、五小类沉积相组合，盐湖边缘沉积相包括滨岸斜坡带相组合、缓坡带相组合、陡坡带相组合，盆内沉积相包括水下隆起带相组合和盐湖深水区相组合；盐湖可划分早、中、晚3个沉积演化阶段，分别对应半咸水湖泊、咸水湖泊和盐湖；形成碳酸盐岩与钙质砂岩、富含石膏的碳酸盐岩与泥岩、厚层石盐与薄层碳酸盐岩等主要岩石组合；盐湖沉积主控因素为气候、古地貌与构造运动。

Salt Lake Depositional Characteristics of Upper Member of Lower Ganchaigou Formation,Western Qaidam Basin

Based on abundant geological and geochemical data, the salt lake sedimentary characteristics of the Lower Ganchaigou Formation of Oligocene were studied to identify the major rock types and discuss the controlling factors of complex lithofacies, so as to restore the paleo-sedimentary environment and establish the sedimentary models. Salt lake can be divided into two types of sedimentary environments including basin margin and intra-basin, and five types of sedimentary facies zones are developed. The beach slope facies zone, steep slope facies zone and gentle slope facies zone are developed in the basin margin sedimentary environment, and the underwater high facies zone and the profound water facies zone are developed in the intra-basin sedimentary environment. There are three evolutionary stages from the bottom to the top of the upper section of the Lower Ganchaigou Formation:semi-salt lake, salt water lake, and salt lake, corresponding to three lithological associations of carbonate rocks and calcareous sandstone, anhydrite-rich carbonate rocks and mudstones, and thick-bedded salts and thin-bedded carbonates. The distribution of sedimentary lithofacies is controlled by the differences of chemical, biological and physical sedimentation, and the main controlling factors of sedimentation are climate, paleo-geomorphology,and tectonic movement.