北祁连志留系复理石的再探讨

本文通过对北祁连冰沟和肃南两地下志留统复理石的研究．认为它们都是深海系的浊流沉积，包括了盆地平原、外扇、中扇和内扇等不同环境。其中夹有多层砾岩，但它们不代表海水变浅或滨海环境，而是深海扇中的海底峡谷沉积。最后，本文进而讨论了有关的古地理面貌和古构造格局。

A FUTTHER DISCUSSION ON THE SILURIAN FLYSCH IN THE NORTHERN QILIAN MOUNTIANS, GANSU PROVINCE, CHINA

The silurian flysch in the northern Qilian Mountains used to be considered as the products of the folding and uplifting processes of the Qilian Calidonian geosynclines. In this area, the Lower Silurian is made of thick rhythmic beds of grayishgreen to black sandstone, siltstone and slate, in which a lot of sedimentary structures such as graded bedding, Bouma sequences, ripples, convolute bedding, flaming strutures, loadcasts and scour marks are observed, indicating the characteristics of turbidite sedimentation. The features of the grain size accumulation curve and the C-M diagram of the sandstones and siltstones in the Lower Silurian also show the natures of the transport and sedimentation of turbidie. And many trace fossils found in the sequences, such as Helminthopsis ichno sp.,Megagrapton ichno sp. et al, indicate a deep sea environment. All these show that the Lower Silurian in the northern Qilian area is the sediments of the deep sea fan turbidites. Based on the detialed measurements of the sequences, some subenvironments can be distinguished, including the basin plain, outer fan, mid-fan and inner fan.