石门杨家坪下寒武统杷榔组三段内波和内潮汐沉积研究

Study on internal-wave and internal-tide deposits of the third member of the Lower Cambrian Balang Formation at Yangjiaping, Shimen

湖南石门杨家坪下寒武统杷榔组第三段主要为一套深灰色、灰绿色页状至薄层含粉砂水云母泥(页)岩与泥质粉砂岩夹透镜状、条带状粉砂岩,其沉积环境为斜坡环境。中上部透镜状、条带状粉砂岩中交错层理极为发育,纹层倾向既有沿斜坡向上和向下双向倾斜的,也有沿斜坡向下或沿斜坡向上单向倾斜的,它们不应是等深流沉积或浊流沉积,而应为内波、内潮汐产生的沿斜坡上下交替流动所形成的。笔者对寒武系内波、内潮汐沉积做了首次研究。

The third member of the lower Cambrian Balang Formation at Yangjiaping, Shimen, Hunan Province consists mainly of dark-gray, gray-green laminated to thinly bedded silt-bearing hydromica mudstones and muddy siltstones intercalated with lenticular and striped siltstones, whose sedimentary environment was a slope environment. Cross laminations are well developed in lenticular and striped siltstones of the middle and upper Parts of the third member, whose laminae are inclined not only bi-directionally up- and down the slope, but also uni-directionally which correspond to up-or down-slope directions. The characteristics indicated that lenticular and striped siltstones should not be contourites or turbidites, but should be formed by alternating up- and down-slope currents produced by internal waves and internal tides. This is the first example of internal-wave and internal-tide deposits found in the Cambrian.