准噶尔盆地石南地区侏罗系-白垩系间风化壳的发现及其地层学意义

本文综合利用测井、录井、钻井等多种井资料，对准噶尔盆地腹部石南地区引起争议的“杂色泥岩”的古生物群化石组合特征，粘土矿物特征，岩性、电性特征等进行了研究。通过孢粉组合的时代对比和粘土矿物分析，证明了“杂色泥岩”是一个区域风化壳，确定了白垩系与侏罗系的界线以及“杂色泥岩”的原始沉积时代，并且通过岩性、电性特征对该风化壳的结构进行了研究。研究表明：该风化壳平面上具有分带结构，垂向上具有分段结构，各段的测井响应特征明显；“杂色泥岩”的原始沉积属于侏罗系西山窑组，石南地区普遍缺失头屯河组；“杂色泥岩”上覆的白垩系清水河组为超覆，下伏的侏罗系西山窑组被削截。据此，对该地区白垩系与侏罗系（K／J）、侏罗系头屯河组与西山窑组（J2t／J2z）地层界线进行了重新划分，建立了新的分层方案。

Discovery of a Weathering Crust between Jurassic and Cretaceous and Its Stratigraphic Significance in the Shinan Area of the Junggar Basin

This paper uses various data such as well logs and drilling records to study the characteristics of palaeo-biota fossil combination and clay minerals from the variegated mudstone in the Shinan area of the Junggar basin, and analyses their lithologic and electric properties. Based on age contrast of spores and pollens and analysis of clay minerals, it was proved that the variegated mudstone is a regional weathering crust. The study ascertained the boundary of the Cretaceous and the Jurassic and the initial sedimentary age of the variegated mudstone: The results show that the weathering crust exhibits planar zonation and vertical stepwise structure. Every unit has clear diagnostic log response. The variegated mudstone belongs to the Jurassic Xishanyao Formation and the Toutunhe Formation is generally absent in the Shinan area. The Cretaceous Qingshuihe Formation overlaps the variegated mudstone, while the Jurassic Xishanyao Formation is truncated by the variegated mudstone. The authors hereby made new boundaries between the Cretaceous and Jurassic, the Jurassic Toutunhe and Xishanyao Formations, and proposed a new division scheme.