宁夏中奥陶统香山群徐家圈组内波、内潮汐沉积类型

Sedimentary Types of Internal-wave and Internal-tide Deposits of Middle Ordovician,Xujiajuan Formation,Xiangshan Group, Ningxia Autonomous Region,China

内波、内潮汐沉积是深水沉积研究中一个非常年轻的研究领域,自发现到现在仅仅20年时间,对其沉积类型的研究目前尚未涉及。以宁夏香山群徐家圈组中的内波、内潮汐沉积为对象,详细描述了深水环境中形成的双向交错层理、单向交错层理、复合流层理及具有波状纹层、束状纹层和交错纹层透镜体的交错层理,并探讨了其成因机制,识别出了短周期内波沉积。在此基础之上,结合已有的内波、内潮汐沉积鉴别标志,从沉积构造的角度对内波、内潮汐沉积类型进行了探讨。将内波、内潮汐沉积分为短周期内波沉积、内潮汐沉积和叠加内波沉积。鉴于内潮汐形成机制的独特性和海洋物理学中内波的研究现状,三者仍统称为内波、内潮汐沉积。

The study of internal-wave and internal-tide deposits is a very young research field with twenty years of history in the deep-water deposition,and there is no study on its sedimentary types.Here,we forcus on the internal-wave and internal-tide deposits developed in Xujiajuan Formation,Xiangshan Group,Ningxia Autonomous Region and describe related sedimentary structures in detail.We interpret combined-flow-ripple lamination and the cross beddings with undulatory laminations,offshooting laminations and cross-laminated lenses as combined-flow and oscillatory flow generated by short-period internal waves respectively.According to these new interpretations and the interpretations of deep-water bidirectional cross-beddings and unidirectional cross-beddings in literatures,we attribute internal-wave and internal-tide deposits to short-period internal-wave deposits,internal-tide deposits and interaction internal-wave deposits.Here,we use internal-wave and internal-tide deposits instead of internal-wave deposits because of the special origin and research status of internal tides.