塔里木地区寒武纪中期古地理与沉积环境

Paleogeography and sedimentary environments of Middle Cambrian periodin Tarim area

寒武纪中期(相当于第三世的第五期、鼓山期和古丈早期)是塔里木地区重要的盐岩、膏盐岩盖层沉积期。对该阶段塔里木地区古地理与沉积环境的研究将有助于其油气赋存条件及分布规律的认识。本文在前人研究的基础上,野外调查和收集分析了13个露头区、17口钻井的地质剖面资料,并参考部分地震勘探成果,重塑了塔里木地区寒武纪中期古地理轮廓,绘制了古构造-沉积环境图。研究表明:(1)寒武纪中期的古地理格局基本承袭了寒武纪早期的特征,但南天山洋盆、北昆仑洋盆和库鲁克塔格—满加尔拗拉槽半深海-深海盆地范围明显扩大,而塔里木陆表海(浅海)盆地范围有所缩小;(2)寒武纪中期,塔里木地区气候干燥炎热,形成了面积达23×104 km2的蒸发台地,沉积数百米厚膏盐岩地层为油气的储存提供了优质封盖条件。

The Middle Cambrian（corresponding to Stage 5,Drumian,Early Guzhanqian of Series 3） is an important sedimentary period of gypsum-halite rocks in Tarim area.Researches on paleogeography and sedimentary environments of Tarim area will help recognize the reservoir and distribution regularity.Based on previous studies,the authors investigated and analyzed 13 outcrops and 17 borehole sections,and consulted some seismic sections.By means of an analysis of stratigraphic and petrologic characteristics,the paleogeographic framework was rebuilt and a tectonic-sedimentary environment map of Tarim area was compiled.Some conclusions have been reached：（1）The paleogeographic pattern in Middle Cambrian period inherited the characteristics of Early Cambrian,but the South Tianshan Ocean,North Kunlun Ocean and Kuluketage-Manjiaer bathyal-deep sea basin were enlarged,and the areas of Tarim epeiric sea basin was reduced in Middle Cambrian.（2）Because the climate of Tarim area was xerothermic in that period,the evaporative platform of 23×104 km2 was formed.Gypsum-halite rocks hundreds of meters in thickness were deposited in an evaporative environment,which provided high quality caprocks.