西秦岭造山带泥盆纪沉积地质学和动力沉积学:西秦岭北带泥盆纪前陆盆地的沉积特征及盆地格局

秦岭造山带是横亘于华北、扬子两板块之间的巨型造山带,在中国古大陆地壳形成演化中占有十分重要的地位。作为连接造山带加里东一海西、印支阶段重要一环的泥盆系对恢复造山带沉积和构造演化意义重大。本文仅从西秦岭北带泥盆系地层和沉积学入手,探讨该区早海西期的盆地格局和构造特征。西秦岭北带泥盆系包括舒家坝群和大草滩群(包括红相和绿相两种类型),前者以临滨-陆棚-半深海背景沉积和风暴流、重力流事件沉积为特色;后者以辫状河和网状河(红相)和湖泊-水下冲积扇和深湖重力流(绿相)沉积为特征。沉积特征和充填序列都反映其形成于压性的前陆盆地背景下。该前陆盆地是由于北秦岭造山带的向南仰冲,在中秦岭微板块北缘形成的。

SEDIMENTARY GEOLOGY AND DYNAMIC SEDIMEN-TOLOGY OF THE DEVONIAN STRATA IN THE WEST QINLING OROGENIC BELT SEDIMENTARY CHARACTERISTICS AND FRAMEWORK OF THE DEVONIAN FORELAND BASIN IN THE NORTHERN BELT OF THE WEST QINLING OROGENIC BELT

The Qlnling orogenic belt lying between the North China Plate and Yangtze Plateplays an important part- in explaining the fo,rmation and evolution of palaeo continents inChina. As all important link between the Caledonian and Hercynian tectonic stages,the Devonian strata in the belt has all along been considered as the key bed to decipher the sedimentary and tectonic evolution in the study area. The present paper focuses on the earlyHercynian basin framework and tectonic features hased on stratigraphy and sedimentologyof the Devonian strata in the northern belt of the West Qinling orogenic belt. The Devonian strata in this region consist of the Shujiaba and Dacaotan Groups (including two types:red factes and green factes). The former is characterized by the nearshore shelf-bathyalbackground deposits, storm deposits and gravity flow deposit-s, while the latter by thebraided and anastomosed deposits (red factes)and lake-subaquenotls alluvial fan,deep-lakegravity flow deposits (green factes ). These depositional characteristics and infilling sequences indicate the existance of the foreland,which was formed oil the northern margin ofthe central Qinling microplate due to the southward obduction of the northern Qinling orogenie belt during early Hercynian stage.