【作者】 李正芳；

【导师】 陈建强；

【作者基本信息】 中国地质大学（北京） ， 第四纪地质学， 2009， 硕士

【摘要】 本文以沉积学、地层学和沉积古地理学等理论为指导,综合露头、钻测井和地震等数据资料,以地层、沉积和构造等多种学科分析为手段,对中扬子区晚侏罗世和白垩纪进行了沉积古地理研究。在前人和项目组研究成果的基础上,对研究区的地层进行了较系统的清理、划分和对比,进一步将中扬子区划分为宜昌-酉阳、江汉和鄂东3个小区,对其上侏罗统-上白垩统的地层进行对比分析。根据区域大地构造和沉积背景资料,以野外剖面观测为主,结合钻井、测井和地震等资料,将中扬子区上侏罗统和白垩系划分为冲积扇相、辫状河相、曲流河相、湖泊三角洲相和湖泊相5种沉积类型,详细阐述了各类沉积相的特征,并进一步得出上侏罗统主要为曲流河沉积体系,下白垩统主要为冲积扇和辫状河沉积系体系,上白垩统主要为冲积扇-扇三角洲-湖泊沉积体系。在地层和沉积体系分析的基础上,利用层序地层学的原理进一步将中扬子区的上侏罗统和白垩系划分出3个二级层序和13个三级层序,依据层序特征和对比发现,中扬子区在侏罗统处于基准面较高的曲流河沉积体系;下白垩统基准面下降,沉积区整体为冲积扇和辫状河沉积体系;上白垩统基准面快速抬升,沉积区整体处于湖泊-扇三角洲沉积体系,一直持续到古近系渐新统晚期。在前人研究成果的基础上,结合沉积体系、地层和物源的研究,利用点(单个露头或钻测井)—线(廊带对比图)—面(沉积古地理图)的编图方法,以二级构造层序为单位,编制了中扬子区上侏罗统和白垩系沉积古地理图,并与上扬子区古地理特征进行了对比分析。结果表明,晚侏罗世到早白垩世中扬子区受秦岭大别造山带和江南逆冲褶皱带的控制,研究区处于挤压逆冲背景下,复合前陆盆地自晚侏罗世自东向西转移,仅在秭归盆地及其以西地区出露地层;早白垩世到晚白垩世古地理的格局发生了明显的变化,构造背景由挤压逆冲转化为伸展断陷,江汉和沅麻等东部盆地群开始发育,西部沉积已限于四川盆地;晚白垩世晚期伸展断陷达到高峰,东南部北东向分散的小型拉分盆地群继续发展,江汉裂谷盆地开始出现。更多还原

【Abstract】 Based on the theories and methods of sedimentology, stratigraphy and palaeogeography, combining with the data of outcrop observing, logging, drilling and seismic, the sedimentary palaeogeographic of late Jurassic and Cretaceous were studied systematically in the mid-Yangtze area by using stratigraphy ,sedimentary and structure methods.In regard to stratigraphic division and correlation, the researched area was divided into three blocks including Youyang, Jianghan and Edong on the basis of forerunner’s data and our research in this thesis. Finally, the paper make analysis of stratigraphy correlation from the Upper Jurassic to the Upper Cretaceous.By referring to the regional geotectonic setting and sedimentary setting data, based mainly on outcrop sections, combined with drilling, logging and seismic profiles, five sedimentary facies were identified in the mid-Yangtze area, which included alluvial fan, braided river, meandering river, delta and lacustrine facies, and deliberately discussed the characteristics of facies. The conclusions were made that Upper Jurassic was mainly developed meandering river; the Lower Cretaceous was mainly developed alluvial fan and braided river; the Upper Cretaceous was developed alluvial fan-fan delta- lacustrine facies.Based on the stratigraphic and sedimentary system, the paper also determined 3 structural sequence and 13 third sequence by using the Principles of Sequence Stratigraphy. Based the sequence characters and comparison , the paper revealed that Upper Jurassic was in the higher base level of meandering river depositional system; the Lower Cretaceous was in the lower base level of alluvial fan and braided river; the Upper Cretaceous was in the higher base level, which developed fan delta- lacustrine facies until late Oligocene.According to the result of previous studies, combining the investigation of sedimentary system, stratigraphic and Source, the structure-sequence sedimentary palaogeographical map of late Jurassic and Cretaceous of the mid-Yangtze area was compiled by adopting sttuctural sequence system tract as basic mapping unit. The sedimentary palaeogeographic characteristics and evolution of different structural sequence and system tracts was demonstrated in details, and make comparison with the upper Yangtze area. Then it concluded that the depositional setting of the Upper Jurassic in Zigui basin is foreland basin because of impaction of Qinling–Dabieshan orogenic belt and Jiangnan fold-thrust belt; the palaeogeographic patterns for the lower Cretaceous and the upper Cretaceous is significantly different, Tectonic setting was converted from compression into extension, at the same time, the jianghan basin and yuanma basin began to develop. The peak of extension was in the end of upper Cretaceous, scattered groups of small pull-apart basin continue to develop in the Southeastern and the jianghan basin began to appear during the period.更多还原