川东北飞仙关组鲕粒特征与水动力相关性研究

早三叠世鲕粒在全球范围内广泛发育，且出现巨鲕。川东北飞仙关组台缘鲕粒滩非均质性强，鲕粒类型复杂。选择川东北龙潭村、莱溪及鱼洞子剖面进行野外实测、镜下鉴定及粒度分析，对鲕粒类型及粒度参数演化与水动力相关性进行研究。研究发现川东北飞仙关组发育7种原生沉积鲕粒，9种后生改造成因鲕粒，其中后生改造成因的破碎鲕可进一步细分。除偏度外，平均粒径、标准偏差、峰度等粒度参数及粒度资料图解曲线形态具有很强的相关性，与鲕粒类型结合判断龙潭村鲕粒滩由活动边缘带转变为稳定鲕粒砂坪沉积，水动力逐渐减小；莱溪呈活动边缘带—稳定鲕粒砂坪—活动边缘带沉积旋回，水动力先减小再增大；鱼洞子向上水动力逐渐减小。但含巨鲕的层位与整体的鲕粒类型及粒度变化趋势相关性较差，这可能是由于巨鲕异常大的粒径形成主要受微生物作用和海水碳酸盐岩饱和度的快速增大复合影响，而非水动力快速变化。因此，在利用粒度参数判断具有巨鲕发育的沉积环境水动力条件时，不能简单地凭借粒度便做出结论，需对鲕粒粒度参数进行相关性分析，去除相关性较差的样品数据。

Correlation Between Ooid Characteristics and Hydrodynamic Forces in the Feixianguan Formation,Northeastern Sichuan

Ooids developed all over the world in the Lower Triassic， and giant ooids appeared. The ooid shoal at the margin of the Feixianguan Formation platform in northeastern Sichuan comprises strongly heterogeneous and complex ooid types. The relationship between ooid type， grain size parameter evolution and hydrodynamic forces were studied for deposits in the Longtancun， Laixi and Yudongzi regions using field measurement， microscopic identification and grain-size analysis. Seven primary divisions and nine subdivisions of ooids were found， and fractured ooids may be classed separately. In addition to skewness， other parameters （e.g.， average particle size， standard deviation， kurtosis and graphic curve shape of particle size data） are strongly correlated. The classifications suggest that the ooid shoal at Longtan village indicates a change from an active marginal zone to a stable ooid sand flat as hydrodynamic conditions gradually decreased. At Laixi， a deposition cycle of active marginal zone-stable ooid sand flat to active marginal zone is evident， with decreasing and then increasing hydrodynamic force. The hydrodynamic force decreases with upward at Yudongzi. However， there is poor correlation between the horizon containing giant and the overall trend of changes in ooid grain type and size， possibly because the abnormally large particle size in the giant ooids is affected by a combination of microbial action and the rapid increase of seawater carbonate saturation rather than rapid change in hydrodynamic force. Therefore， when judging the hydrodynamic conditions of sedimentary environments containing giant ooids using grain-size parameters， it is not possible to draw a conclusion from grain size alone， but it is necessary to analyze the correlations between ooid grain-size parameters.