西秦岭北带大草滩群的解体及其地质意义——兼论北秦岭加里东运动的性质

The Disintegration of the Dacaotan Group in North of Western Qinling and its Geological Significance

分布于西秦岭北带的上泥盆统大草滩群 (D3dc) ,被众多研究秦岭的地质学家认为是典型的造山后的磨拉石建造 ,并将这套地层作为北秦岭加里东运动最直接、重要的证据之一。我们的工作发现 ,大草滩群是由两套不同时代、不同沉积建造的地层体经逆冲—推覆构造作用形成的地层叠置系统。因此 ,原大草滩群予以解体 ,建议取消。

The Upper Devonian Dacaotan Group in the north of Western Qinling has been regarded to be the typical Late Devonian molass and cited as one of the most important and direct evidences of the Caledonian Orogeny of northern Qinling. Our study proves that the Dacaotan Group is composed of two parts. The upper one (Devonian), which is different from the lower(Dias) in age, texture and lithology, lies on the lower with a thrusting, so that the Dacaotan Group should be disintegrated and its name should be abandoned. This recognition will provide important evidence for the study of the characteristics of Caledonian Orogeny and the evolution of Northern Qinling.