元古界会理群凤山营组风暴流沉积特征

四川省会理县洪川桥地区,是会理群凤山营组广泛分布地区之一,出露面积达百余平方公里。在洪川桥凤山营组剖面的上部(洪剖119层—108层),发育一套约845m厚的风暴流沉积。现将其特征及形成机制作一初步分析,以供参考。一、岩性特征风暴流沉积物,主要为灰—深灰色粉砂质粉屑灰岩和部分泥质灰岩。有时两者呈薄的互层出现。一般层厚几毫米到几厘米,沿走向在数十厘米或几米内尖灭,形成一个个薄的透镜

The Characteristics of Storm Current Deposits in the Proterozoic Fengshanying Formation,Huili Group,Sichuan

A suite of storm current deposits with a thickness of 845 m is developed in the upper part of the Proterozoic Fengshanying Formation in the Hongchuanqiao area, Huili County, Sichuan Province. These tempestite beds comprise the overlapping lenticular layers composed mainly of grey and dark grey silty calcisiltites, locally of argillaceous limestones. The common sedimentary structures include parallel lamination, wave ripple cross-lamination of hummocky crossstratification, storm wave ripples and convolute structure,etc.. The vertical sequences of the storm current deposits in the Hongchuanqiao section consist generally of the association of parallel beds and hummocky cross beds, occasionally of the association of parallel beds, wave ripples and lag beds. Graded beds and sole erosion structure, however, are rare. It follows that the storm current deposits should be the distal deposits near wave base on clear-water shelf.