合肥盆地侏罗-白垩纪沉积层序及其对周缘隆起的差异响应

Hefei Basin is a typical area for the research on significant tectonic events on the southeastern margin of North China block in the Mesozoic, thanks to its special tectonic location and relatively complete Jurassic-Cretaceous sedimentary deposit. However, there are still some awareness differences and doubtful points of response to periphery tectonic belt of sedimentary evolution, owing to fewer outcrops on surface, uneven distribution and low-level sedimentary records. Therefore, we decide to survey and develop the sedimentary information potential of deep exploration data and samples on the basis of existing achievements, aiming at dubious viewpoints and weakness. Aided with geological survey, we aim to acquire data of substance composition, sedimentary characteristics, palynological assemblage, seismic reflection property, sounding curve reconstruction and isotope of related strata through techniques of paleontology, isotope thermochronology, destination process of geophysical exploration data and petrology. Research emphasis will be laid on geological period of doubtful strata, sedimentary response of overlay area, and origin tracing in Huoqiu region. We also intend to comprehensively analyze the Jurassic-Cretaceous System sedimentary evolution, probe into its discrepancy response to periphery uplift, pay special attention to space-time transformation in orogenic belt of Zhangbaling and Dabie Mountain, and provide references for research on the Mesozoic Tanlu fault activity, Dabie orogenic belt evolution and oil gas survey.

合肥盆地侏罗-白垩系沉积较齐全，而且与重大构造事件活动区紧密相邻，被认为是研究中生代华北陆块东南缘构造活动及其沉积响应的有利地区；但受地面露头较少、深部沉积记录揭示程度低等制约，其沉积演化及其对周缘构造带隆升的响应研究还存在一些认识差异和疑点问题。为此，我们拟在已有成果基础上，针对以往研究存在的疑点问题和薄弱环节，重新审视和开发已有深部探测数据和样品包含的沉积信息，辅以地面地质调查，借助于古生物学、同位素热年代学、物探数据目标处理和岩石学等技术方法，获取相关地层的物质成分、沉积特征、孢粉组合、反射地震属性、电测曲线重构和同位素测年等材料，着重开展疑点地层地质时代、覆盖区沉积响应及霍邱地区物源示踪等研究，综合分析侏罗-白垩系沉积演化过程，探索其对周缘隆起的差异响应，特别关注张八岭和大别造山带制约沉积演化的时空变换，为中生代郯庐断裂活动、大别造山带演化和油气勘查等研究提供参考。

按照资助计划书，通过主要岩石地层单位梳理、地层格架建立、关键性疑点地层厘定、沉积特征等研究，结合前人相关成果，主要分析了合肥盆地侏罗-白垩系地层层序和沉积演化过程，探索其对周缘隆起（断裂）的差异响应，主要认识：（1）根据钻井、地震和地面地质等资料，依据地震层序与区域构造事件的对应关系，结合古生物学、岩石学和同位素测年等证据，尝试性提出了层序格架新认识：周公山组和圆筒山组岩石学、地球物理学和古生物学等特征相似，二者合并、称为圆筒山组，原先的周公山组和圆筒山组分别视为该组地层的上部和下部，时代为中侏罗统。朱巷组为上侏罗统。响导铺组为下白垩统。与以往研究相比，本文强调了层序界面关系和区域构造事件在地层划分与对比中的重要性，力求达到古生物遗迹、岩性、层序、同位素测年和区域构造背景的统一。（2）依据地震反射特征和露头、钻井等资料，结合郯庐断裂走滑断裂和伸展断裂体系、大别山北缘断裂早中生代逆冲推覆和晚中生代伸展体系分析，探索了沉积演化：早、中侏罗世表现为前陆盆地特征，大别山隆起是主要物源,下侏罗统沉积范围比较小，中侏罗统广布全盆地，为盆地发展的鼎盛期。晚侏罗世,表现为挠曲盆地特征，大别山及张八岭隆起均提供物源。早白垩世，响导铺组主要分布在大桥凹陷，受郯庐断裂伸展活动影响明显，张八岭隆起是主要物源。晚白垩世，合肥盆地解体，张桥组沿断裂下降盘呈东西向分布。合肥盆地西缘和北缘隆起在侏罗-白垩纪时物源特征不明显。此外，本次研究还在安参1井基底地层发现了保存良好的孢粉化石647粒，共计23属51种及部分未定种，经过与华北其他地区孢粉组合特征对比分析，明确了安参1井前侏罗纪基底为石炭—二叠系。