米钵山组复理石中的内潮汐沉积

INTERNAL TIDE AND INTERNAL WAVE DEPOSITES IN FLYSCH OF MIBOSHAN FORMATION

贺兰拗拉谷米钵山组复理石由具有递变层理、双向交错层理、单向交错层理、复杂多向交错层理、飘逸层理和波痕构造的韵律性砂岩、粉砂岩、泥岩薄互层组成。根据双向沉积构造等典型物性特征识别出3种内潮汐沉积微相,即飘逸层理砂泥岩韵律性薄互层微相,单向交错层和交错纹理砂岩粉砂岩微相,双向交错纹理和羽状交错纹理砂岩粉砂岩微相。结果表明:研究区复理石为深水牵引流(内波、内潮汐)、重力流以及原地沉积复合成因;经典的鲍玛序列是有待商榷的;重力流与牵引流存在流态转化。

The Miboshan Formation flysch of Helan aulacogen mainly consists of rhythmically thin layers of gray fined sandstones,silt sands and dark gray mudstones in which the typical graded bedding, elegant beddings,cross bedding,pinnated cross bedding,bimodal cross bedding,rhythmic stratification and ripple mark are well developed. Abundance trace fossils are found in the flysch.Three internal tide depositional microfacies are recognized and studied in the flysch,they are rhythmically thin layers of fine sandstones,mudstones and silt sands microfacies with elegant bedding,unidirectional cross bedding and cross lamimated sandstones,silt sands microfacies,fine sandstones, silt sands microfacies with pinnated cross bedding and bidirectional cross lamimates. Based on the study,the flysch of Helan aulacogen is inferred to be formed by deep water traction current （internal tide）,gravity current and deep water in situ deposits. The classical Bouma sequence is to be brout up and analyzed various ideas,; The transformation between the traction current and and gravity current exists.