柴达木盆地北缘石灰沟地区下奥陶统沉积特征

Sedimentary Characteristics of the Lower Ordovician in the North Margin of Qaidam Basin

柴达木盆地北缘石灰沟地区下奥陶统石灰沟组主要为一套深灰色至灰黑色页岩夹砾屑灰岩、砂屑灰岩、砂岩及粉砂岩 ,多泉山组主要为浅灰至深灰色薄层泥晶灰岩 ,顶部有砾屑灰岩。研究表明 ,其中的暗色页岩主要为斜坡至盆地的深水细粒沉积 ,砾屑灰岩具有碎屑流沉积的特征 ,属碎屑流沉积 ,而砂屑灰岩、砂岩及粉砂岩具有典型的浊流沉积特征 ,应为浊流沉积 ;研究区早奥陶世沉积环境主要为广海陆棚、斜坡至盆地边缘 。

The Lower Ordovician Shihuigou Formation in the north margin of Qaidam Basin consists mainly of dark-gray to black shales with minor intercalated beds of calcirudite, calcarenite, sandstone and siltstone, and the Duoquanshan Formation consists mainly of grayish to dark-gray thin calcilutite with calcirudite on the top. The study shows that dark shales are deep-water fine-grained deposits from slope to margin of slope, calcirudites are debris flow deposits, and calcarnites, sandstones and siltstones are typical turbidity current deposits. The sedimentary environments of Lower Ordovician in the study area may be deep-water shelf, slope to margin of basin where water is gradually deepened.