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陆相泥盆纪地层主要分布于北祁连山地层分区及河西走廊—六盘山地层分区(图1),系指位于石炭系杜内阶之下和下古生界之上的一套以灰绿—紫红色砂砾岩为主的山麓、山前河湖相沉积,前人曾称“老君山砾岩”,或“老君山系”等,按岩性、岩相旋回及古生物可分为中泥盆统老君山群及上泥盆统沙流水群。本文主要据甘肃、宁夏、青海的区域地质调查以及石油地质、煤田地质和王振民、王瑞龄、周良仁、沈光隆等整理的有关资料。老君山群的命名地点在民乐老君山,岩性与肃南石窑沟剖面相似,下部为紫红色砾岩夹砂砾岩、砂岩、火山凝灰岩,上部为褐红、灰绿色红砂岩,厚度大于1000米。在北祁连山分区的靖远县永安堡雪山地区,周文昭等(1964)所测剖面层序为:
The continental Devonian strata are mainly distributed in the North Qilian stratigraphy subdivision and the Hexi Corridor - Liupanshan stratigraphic subdivision (Figure 1). The Devonian stratigraphic subterranean terrain is defined by a set of gray-green- Mudstone-based foothills, piedmont lacustrine facies deposition, formerly known as “Laojunshan conglomerate”, or “Laojunshan”, according to lithology, lithofacies cycle and palaeontology can be divided into mud basin Old Laojunshan Group and Upper Devonian Sand Flow Group. This article is mainly based on the regional geological survey of Gansu, Ningxia and Qinghai, as well as the relevant materials compiled by petroleum geology, coalfield geology and Wang Zhenmin, Wang Ruiling, Zhou Liangren and Shen Guanglong. The Laojunshan group is named after the Minle Laojunshan, with similar lithology and Shiyan Shiyaoou profile. The lower part is composed of purplish red conglomerate, sandstone and volcanic tuff. The upper part is reddish-brown, gray-green red sandstone with a thickness of over 1000 Meter. In the Northern Qilian Mountains Jingyuan County Yong’an Fort snow-capped mountains, Zhou Wenzhao et al (1964) measured profile sequence: