囊谦盆地贡觉组含膏盐地层粘土矿物组合特征及气候环境意义

囊谦盆地晚始新世贡觉组厚层红色含膏盐粉砂质泥岩是研究青藏高原始新世古气候演化和含膏盐沉积环境的良好素材。采集囊谦盆地贡觉组约257 m含膏盐地层的碎屑沉积物,研究其粘土矿物成分和组合特征及气候与沉积环境变化。结果显示,粘土矿物主要以伊利石(52.1%)为主,其次为绿泥石(8.1%)和高岭石(3.5%)。根据岩性特征及粘土矿物组合变化,剖面自下而上可划分为3个阶段,分别指示了暖湿—低盐度、冷干—高盐度、较暖湿—低盐度的气候和沉积环境。贡觉组气候与沉积环境受到青藏高原地区干湿交替变化大背景的影响。

Clay Mineral Assemblage Characteristics and Sedimentary Environmental Significance of Gypsum-bearing Strata in Gongjue Formation, Nangqian Basin

The thick red gypsum-bearing silty mudstone of Gongjue Formation in the late Eocene of the Nangqian Basin is a good material for studying the Eocene paleoclimate evolution and gypsum-salt depositional environment in the Qinghai-Tibet Plateau. Clastic sediments of the Gongjue Formation of the Nangqian Basin, about 257 m gypsum-bearing strata, were collected to analyze the components of clay minerals and study the evolution of paleoclimate and sedimentary environment. The results show that illite (52.1%) is the main clay mineral, followed by chlorite (8.1%) and kaolinite (3.5%). According to the lithological characteristics and the variation of clay mineral assemblages, the profile can be divided into three stages from bottom to top, indicating the climate and sedimentary environment of warm-wet-low salinity, cold-dry-high salinity,and warm-wet-low salinity,respectively. The climate and sedimentary environment of Gongjue Formation are influenced by wet and dry changes in the Qinghai-Tibet Plateau.