甘肃靖远─景泰泥盆系湖相风暴岩及其古地理意义  

TEMPESTITE AND ITS PALAEOGEOGRAPHICAL SIGNIFICANCE OF DEVONIAN IN JINGYUAN AND JINGTAI COUNTIES,GANSU PROVINCE

作　　者：杜远生[1] 周道华[1] 龚淑云[1] 韩欣[1] 

机构地区：[1]中国地质大学,湖北武汉430074

出　　处：《矿物岩石》2001年第3期69-73,共5页Mineralogy and Petrology

基　　金：自然科学基金资助 (项目编号 :49972 0 78)

摘　　要：甘肃靖远景泰一带泥盆系雪山组和沙流水组以河湖相碎屑岩为主 ,内发育典型的风暴沉积构造 (包括渠铸型、槽筑型、丘状交错层理和洼状交错层理、平等层理、块状层理和递变层理等 )。雪山组和沙流水组的风暴沉积主要包括 3种岩相类型 :A底部具渠铸型或槽筑型的块状层理和递变层理砂岩。 B具丘状或洼状交错层理及平行层理的砂岩。C具均质层理的粉砂岩、泥质岩。上述岩相 A,B,C分别代表风暴事件沉积中风暴流行作用 -风暴后的快速悬浮沉积 (事件沉积 ) ,它们组合成典型的风暴沉积序列。甘肃靖远一带晚加里东 -早海西期位于北祁连造山带北缘同造山盆地的构造背景下 ,泥盆纪雪山组 -沙流水组以河湖相沉积为主。泥盆纪湖相风暴岩的发现表明该区处于低纬度 (5°～ 2 0°)的风暴作用带。中、晚泥盆世北祁连造山带构造隆升渐弱 ,海拔不高 ,不足以阻隔风暴作用对山后湖盆的侵扰。因此在近海湖盆中形成风暴岩沉积。该沉积对于认识北祁连 -河西走廊泥盆纪的古地理。Xueshan and Shaliushui Formations in Jingyuan and Jingtai Counties,Gansu Province are mainly composed of clastic rocks with well developed sedimentary structures of storm deposits,characterized by gutter casts,hummocky or sunken cross bedding,parallel bedding.The storm deposits in Xueshan and Shaliushui Formations consist of 3 types of lithofacies:1.sandstone with massive and graded bedding and bottom gutter casts and flute cast,2. sandstone with hummocky or sunken cross bedding and parallel bedding,3.siltstone and mudstone with homogeneous bedding.These lithofacies represent respectivly storm current(1),deposits of storm wave(2),rapid suspended sediment(3) within storm event deposits.These lithofacies constitute typical sedimentary sequence of storm deposits.In the Late Caledonian and Early Hercynian stages,Jingyuan and Jingtai Counties was located in a tectonic background of syn orogenic basin of North Qilian orogenic belt.Xueshan and Shaliushui Formations are mainly composed of fluvial and lacustrine deposits.The discovery of tempestite in Xueshan and Shaliushui Formations of Devonian reflects that this region was located in low latitude(5°~20°) zone where storm deposit developed.In the Middle and Late Devonian the uplifting of North Qilian orogenic belt was weak and the elevation was not high enough to prevent the storm to disturb the lake behind the mountains,as a result,the tempestite formed in the lake basin near marine.Meanwhile the discovery of the storm deposits has important significance in the interpretation of the Devonian palaeogeography,palaeoclimate and palaeotectonics of North Qilian Mountains and Hexi Corridor.

关 键 词：风暴岩 风暴沉积 泥盆纪 甘肃 古地理 古气候 地层层位 

分 类 号：P588.245[天文地球—岩石学] P534.44[天文地球—地质学]