The Xujiajuan Formation of the Lower Xiangshan Group in Ningxia, China, is composed of grayish-green to yellowish-green, fine- to medium-grained sandstone, calcareous sandstone, siltstone, and shale. The upper part is thin-bedded limestone. At the top of the second and third members of the formation, a number of beds intercalated between turbidites and deep-water shale show well-developed cross-bedding. These beds are composed mainly of thin- to medium-bedded calcareous siltstone, fine-grained sandstone, fine-grained calcisiltitic limestone, and silty shale. All bedding types reflect traction-current action. The laminae of the bidirectional and unidirectional cross-bedded units tend to dip either opposite to or at a large angle to the regional slope. The units vary in shape and orientation in both upslope and downslope directions. A comprehensive evaluation of the sedimentary structures and inferred paleocurrents suggests that the cross-bedded intervals were not formed by contour currents or turbidity currents, but most probably represent internal-wave and internal-tide deposits.

四川盆地及其周缘地区下二叠统碳酸盐岩中，不同程度地发育着一些细晶至粗晶白云岩和白云质灰岩，前人将其解释为淡水透镜体混合白云石化的产物。根据野外及室内薄片观察，并结合阴极发光、碳氧稳定同位素、地球化学分析、包体均一温度和有序度的综合研究，认为这类白云岩主要是由埋藏白云石化作用形成的。

内波、内潮汐沉积是近10年来发现和研究的一种新的深水牵引流沉积类型。现代海底普遍发育由内波、内潮汐引起的深水牵引流，内波、内潮汐不仅可形成各种小规模、分散的深水牵引流沉积，而且还可建造千米级的大型沉积物波。在古代地层记录中已发现各种厘米级的内波、内潮汐沉积单元，但尚未发现内波成因的大型沉积物波。通过系统的岩心观察和地震剖面分析，在塔中地区中上奥陶统碎屑岩段内发现了由内波和内潮汐作用形成的各种牵引流沉积构造单元。已识别出4种内波、内潮汐沉积微相类型及5种基本垂向沉积层序，同时还在研究区中上奥陶统陆坡相中识别出了内波成因的大型沉积物波。这些内波、内潮汐沉积具有较好的油气潜能，是该区中上奥陶统潜在的油气勘探新领域。

宁夏中奥陶统香山群为一套遭受轻微区域变质的灰绿色中2细粒长石石英砂岩、板岩、砾屑灰岩和硅质岩等，从下到上可分为徐家圈组、狼嘴子组和磨盘井组。系统地论述了香山群发育的各种深水沉积的特征及其沉积序列，认为香山群由深水原地沉积和深水异地沉积组成，其中后者主要包括浊流沉积、碎屑流沉积、内波、内潮汐沉积和深水复合流沉积。垂向组成单元自下而上依次为浊流沉积层（Ⅰ）、牵引流沉积层（Ⅱ）和半深海沉积层（Ⅲ）。这些认识不仅对进一步开展香山群的沉积学研究具有重要的意义，而且也可为该地区早古生代构造环境的研究提供重要的信息，同时也为目前在国际上引起注意的深水重力流的流体特征研究提供新的实例。

The study of internal-wave and internal-tide deposits is a new research field on sedimentology during the last ten years. Deep-water traction currents induced by internal waves and internal tides are developed on the modern sea floor, which can form not only all kinds of small scale and dispersal deep-water traction currents deposits, but also large-scale sediment wave in km-size scale. In this paper, the concepts and features of internal waves and internal tides in oceanography are introduced, and the characteristics, sedimentary sequences, sedimentary microfacies and sedimentation models of internal-wave and internal-tide deposits found and the origin of large scale sediment waves in deep sea bottom are summarized. The relationship between internal-wave and internal-tide deposits and petroleum is discussed, and finally internal-wave and internal-tide deposits are shown to be a new potential field for petroleum exploration.