用Fischer图解研究山西临汾中奥陶世马家沟组旋回层序

山西临汾奥陶纪马家沟组顶底与上覆和下伏地层呈平行不整合，是一套沉积于广阔陆表海浅水台地上的碳酸盐、蒸发岩潮坪层序。泥晶石灰岩、白云岩、蒸发岩等岩石类型和沉积构造如鸟眼、干裂、石膏、石盐假晶、叠层石等反映出来的旋回性清晰明显。在野外共划分出了８４个旋回层，用Ｆｉｓｃｈｅｒ图解对马家沟组的旋回层序进行了分析，共划分出３个三级旋回，１２个四级旋回。８４个旋回层可能是因地球偏心率变化而引起的米兰柯维奇旋回

The Application of Fischer Plots to the Analysis of Cycles in Middle Ordovician Majiagou Formation in Linfen,Shanxi Province

The Middle Ordovician Majiagou Formation is in unconformable contact with both t he underlying and the overlying strata. It is a carbonate_evaporated tidal sequ ence deposited on a large shallow water carbonate platform. Cycles formed by suc h rocks as limestone, dolomite, gypsum or such sedimentary structures as birdey e structure, cracks, pseudocrystals of gypsum and halite are obvious. 84 cycles were recognized in the field and Fischer plots were used to analyse the cyclic s equence. 3 third_order and 12 fourth_order sea level curves were differentiate d. The 84 cycles are considered to be of a kind of Milankovitch rhythms formed by the eccentric variation of the earth. The Fischer plots are proved to be an effective tool for analysing the cycles formed in tidal environment.