北祁连西段志留系层序地层学特征

The Sequence Stratigraphical Characters of the Silurian System in the West of the Northern Qilanshan

甘肃省北祁连西段志留纪地层为一套形成于残留盆地的碎屑岩堆积,其岩石地层包括肮脏沟组,泉脑沟山组,旱峡组,分别相当于年代地层单位的下志留统、中志留统和上志留统。通过对其沉积环境、层序地层学特征及其变化研究认为该区地层包括低水位体系域(水位扇、低水位进积楔)、海侵体系域和高水位体系域沉积,其沉积环境由深海扇(近源浊积盆地、远源浊积盆地)渐变为陆棚直至潮坪,为一个完整的海浸海退旋回,基本上是一套完整的Ⅰ型层序。

The Silurian System in the west of the northern Qilianshan, GanSu province, is detrial rock that formed in a residual basin. The sequence stratigraphical characters and evolution of the Silurian System show the process well when the residual basin formed, developed and died out. The Silurian System is composed of Angzanggou, Quannaogoushan and Hanxia Formation. Angzanggou Forma- tion corresponds with the lower Silurian System of chronostratigraphic unit, Quannaogoushan Formation corresponds with the middle Silurian System, and Hanxia Formation corresponds with the upper Silurian System. Based on the study of the sedimentary environment, stratigraphic texture, sequence stratigraphic characters and their changes, it is suggested that the Silurian System include the lowstand system tract （LST）, transgression system tract （TST）, and highstand system tract （HST）. The sedimentary environment is from deep - sea fan （proximal pluvial basin and distal pluvial basin） changed slowly into the continental shelf and to tidal flat, which composes a whole circle of marine invasion to marine regression. So, it＇s likely a set of type 1 sequence basically.