内蒙林西—吉林九台地区晚二叠世生物礁与古地理环境

Some important discovers, Late Permian organic reefs, marine limestone and fossils, and Permo-Triassic angle unconformities, have been firstly made in regions of the Linxi, Inner Mongolia - the Jiutai, Jilin. If they could be studied further, many progresses would be achieved for promoting forward the reef-study in North China, restoring palaeo-geographical conditions, and providing evidences to discuss about closing, folding and raising of the Xingan-Inner Mongolia sea-trough.Study of this project will be carried out based on accuratting fossil zones, measurring isotope-chronic specimens and refining stratigraphic division-correlations. Characteristic studies about reefs and reef-facies strata will be done carefully on build-categories, community ecologies, developments and condition-restrictions. And according to basal characters of reefs and the reef chain, the palaeo- geographical conditions and variations will be restored systematically by analysing sedimentary facies and sea-level elevations of the Upper Permian. Then Perrmo- Triassic angle unconformities will be investigated about occurrences, distributions and fasies of their overlayers and underlayers. Moreover, combining regional investigation and exposing hidden-reef bodies, a relationship will be discussed between space-distributions of the reef-chain and close-raising of the Xingan-Inner Mongolia sea-trough. Besides,the source-reservior-cover of oil-gas will be analysed for reef-facies strata in the Upper Permian. The applicant and his group have been worked on reefs and related researches for a long time, and accumulated with rich materials and experiences. And the study of project has reliable work-bases of the earlier stage and could arrieved at the expect objective.

内蒙林西-吉林九台地区多处发现晚二叠世生物礁、海相灰岩和化石、及晚二叠世\早三叠世角度不整合。申请立项研究,对促进我国北方生物礁研究发展，重新认识研究区晚二叠世古地理环境和演变，及论证兴-蒙海槽闭合隆起均具有重要意义。本项研究强调以严格化石分带、系统同位素测年和精细地层划分对比为基础；突出研究代表性礁体和礁相地层的形态结构、群落生态和建造机制等基本特征；揭露隐伏礁体，确定生物礁链的生长发育和环境制约；利用生物礁的特殊指相优势，结合晚二叠世礁相地层的沉积相分析和海平面升降，恢复研究区古地理环境及演变；深入研究晚二叠世\早三叠世角度不整合，查明上覆/下伏地层的产状、分布和沉积归属，论证生物礁链时空分布与兴-蒙海槽闭合隆起的关系；以及系统研究晚二叠世地层的油气生储盖特性。申请者和项目成员长期从事相关学科研究，具有丰富的工作经验，项目前期工作基础坚实，研究实施能够达到预期目标。

重点研究内蒙林西-吉林九台晚二叠世陆缘生物礁及其造礁环境；并将研究区域和时代扩展至内蒙正镶白旗中二叠世三面井组和达茂旗晚石炭-早二叠世阿木山组，以探讨华北板块北缘晚古生代礁链带延伸和构造古地理特征。. 研究取得多项重要成果和进展：多处首次发现生物礁、菊石、角石和疑源类，精细地层划分对比，再次证实华北板块北缘晚二叠世为通畅的海相环境；识别三种陆缘造礁环境，即陆缘碳酸盐台地、简单火山岛弧体系和复合火山岛弧体系，特别火山岛弧环境大量“火山碎屑障积礁”的发现和研究，突破“生物礁为碳酸盐建造”的传统概念；按形态结构、古地理位置和环境制约，将内蒙南部陆缘生物礁分为层礁、点礁、堤礁、圆丘礁、锥礁、塔礁和柱礁，补充完善前人生物礁划分；深入研究各种陆缘造礁环境，系统划分古地理单元，即近岸-潮坪、泻湖、礁滩障壁、陆棚斜坡、火山岛弧、弧前与弧后盆地、弧前三角洲和外侧岛弧，并研究各单元的生物礁组合特征，建立陆缘生物礁古地理分布模式；选择3个代表地层剖面采集火山岩样品，进行锆石U/Pb同位素测年，获得8组可靠数据。. 最后，综合生物礁、造礁环境、同生沉积构造和测年数据的证据，恢复研究区构造古地理演变，论证兴-蒙海槽在晚二叠世最终闭合隆起。