雪峰古陆边缘上石炭统露头层序地层

雪峰古陆边缘沅陵地区的上石炭统岩性特殊，以灰岩为主平白云质灰岩、砾屑灰岩与砾岩、砂岩相互成层，交替出现，因此，相对海平面升降变化在这种类型沉积中表现明显，利用层序地层的研究。上石炭统为１个三级层序，底部以Ｉ型层序与震旦系留茶坡组硅质岩接触；顶部仍以Ｉ型层序边界与下二叠统黔阳组成邻。包括低水位体系域、海进体系域和高水位体系域；依据准层序的叠是分为两个准层序组，即海进体系域和高水位体系域。

Sequence stratigraphy of the Upper Carboniferous strata along the margins of the Xuefeng ancient land

The Upper Carboniferous strata in the Yuanling region along the margins of the Xuefeng ancient land are characterized by limestones interbedded with dolomitic limestones,calcirudites,conglomerates and sandstones. The remarkable relative sea level changes in these strata are considered to facilitate the sequence stratigraphic approach. The Upper Carboniferous strata as a third order sequence overlie the Sinian Liuchapo Formation and underlie the Lower Permian Qianyang Formation,bounded by the type 1 sequence boundary at the top and the base,respectively. These strata consist of the lowstand systems tract,transgressive systems tract and highstand systems tract, which may be grouped,according to stratal stacking patterns,into two parasequence sets:transgressive systems tract and highstand systems tract.