北碚地区下三叠统飞仙关组的双壳类与古水流关系

RELATION BETWEEN BIVALVIA AND PALAEOCURRENT IN FEIXIANGUAN FORMATION OF LOWER TRIASSIC IN BEIBEI,CHONGQING

重庆北碚地区下三叠统飞仙关组泥灰岩中含大量双壳类化石,其排列有一定规律。所研究的样本中,过壳喙的壳体平分线与古水流方向一致,壳喙指示水流方向。随机测量53个壳体,经数理统计,得出古水流方向应为294°,并证明贝壳层的沉积环境为泻湖潮坪上的潮渠。

There are many fossils of Bivalvia in the marl of Feixianguan formation of Lower Triassic in Beibei, Chongqing. The shells' arrangement is regular. In the samples under study, the bisectors of the shells which pass through their beaks are parallel to the palaeocurrent direction, and the beak indicates the current direction. After measuring 53 shells at random, we calculated the palaeocurrent direction, which is 294°, with mathematical statistics method, and proved these shell members' sedimentary environment to be tidal ditch on tidal flat of lagoon.