甘肃敦煌地区现代泥裂几何学特征及成因机制探讨

Geometric Features and Genetic Mechanism of Modern Mud Cracks in Dunhuang, Gansu

沉积构造是沉积学研究的核心内容之一,而泥裂作为物理成因中的暴露成因构造,一直受到学者的关注。此次研究以甘肃敦煌阿克塞河和党河地区的泥裂为研究对象,根据泥裂多边形平面形态特征和边缘形态特征划分泥裂的类型,表征不同类型泥裂的几何学特征,总结泥裂发育的影响因素,并探讨几种特殊泥裂的成因机制。研究结果表明,甘肃敦煌地区发育矩形泥裂、圆形泥裂、不规则泥裂、复式泥裂以及边缘翘起型泥裂;泥裂的发育受到温度及其变化、泥质沉积物的性质、上下物质的差异、含盐度和后期生物改造的影响;矩形泥裂多发育在倾斜地层之上;边缘翘起型泥裂泥质沉积物一般较薄,沉积物底部为松散的粉砂岩,其形成一般经历初始阶段、破裂阶段、分离阶段和翘起阶段四个过程;复式泥裂反映了古水体、古气候的多期次变化,对古环境恢复具有一定的指导意义。

Sedimentary structure is one of the mainelements of sedimentology. And mud cracks, which belong to the exposure relatedstructures, have been interested by scholars. In this study, mud cracks in Akesai River and Dang River, Dunhuang, Gansu wereclassified according to shape characteristics and edge features of the polygon. Geometric features were characterized and the differenceof forming mechanisms was discussed for different types of mud cracks. The results show that there were rectangular, circular, irregular,duplex and edge-curl mud cracks in Akesai River and Dang River, Dunhuang, Gansu. Temperature, sediments properties, thedifferences between the upper and the lower, the salinity and biological activity influenced the formation of mud cracks. Moreover,rectangular mud cracks tend to develop on the slope formation which was uncomfortable. The argillaceous sediments overlying siltstonewas usually thinner in the typical edge-curl mud cracks. The process of the mud crack development is divided into initial stage,cracking stage, separation stage, and buckling stage. In addition, duplex mud cracks may be used to help understand changes inpalaeocurrent and palaeoclimate.