渤海海域中新世初期砂砾岩体沉积学、年代学及其对构造变革的响应

During the early Miocene, a set of glutenite is widely distributed on the gentle slope above the bottom boundary of Neogene Guantao Formation (T2) and accompanied by magmatic activity in the offshore Bohai Bay basin, corresponding to the major tectonic evolution event in the Cenozoic China offshore basins. However, the response between the distribution of glutenite and tectonic change event is still not clear. Through the study of the sedimentary characteristics, scale and distribution of this set of glutenite, combined with the denudation thickness of the T2 boundary and age constrains of magmatic activity analysis, the project will dissect the response among the glutamate and the evolution of tectonic plates. Then, the continental coupling response and the sedimentary response will be studied in the interaction between Eurasia and the periphery of the Pacific plate and the Indian plate in the early Miocene. Lastly, the genetic mechanism and model of the gentle slope-type glutenite can be clarified. Based on the sedimentology and chronology of the glutenite, the Cenozoic geodynamic condition and basin formation mechanics of the offshore Bohai Bay Basin can be analyzed with a new perspective, and these results have not only yielded implications for better understanding of the formation and evolution of Cenozoic Bohai Bay Basin, but also provided service for the exploration of the middle and large-scale oil and gas fields with the type of glutenite in the study area.

渤海海域中新世初期T2界面处广泛发育一套盆地缓坡背景砂砾岩体并伴随岩浆活动，且T2界面对应于中国东部近海新生代盆地重大板块构造变革事件，然而这套大面积分布砂砾岩体与构造变革界面的响应关系尚不明确。项目通过该套砂砾岩体的沉积学特征、规模和空间展布分析，结合T2界面处剥蚀程度及伴生岩浆活动时限约束，探讨砂砾岩体对重大构造板块变革的响应，完善中新世初期欧亚大陆与周缘板块作用过程的陆内耦合效应，厘定大面积砂砾岩体分布的成因机制及发育模式。本项目借助渤海海域中新世初期砂砾岩体沉积学与年代学研究，以新的角度解析渤海海域新生代成盆动力学机制，研究成果对揭示海域新生代盆地形成演化有理论意义，同时也可服务于渤海海域新生代含油气盆地寻找中大型砂砾岩油气田的实际勘探需求。

渤海海域中新世初期T2界面处广泛发育一套盆地缓坡背景砂砾岩体并伴随岩浆活动，该套砂砾岩体与界面处重大板块构造变革响应亟待厘清。本项目针对环渤中坳陷区晚渐新世-早中新世砂砾岩及伴生岩浆岩应用沉积学与年代学分析方法，综合解析砂砾岩体岩相、沉积响应、形成年代及成因机制，即1）选取不同源区母岩制约下砂砾岩岩心样品，建立砂砾岩岩相划分标准；2）结合T2界面处沉积古地貌恢复及水体环境分析，厘定渤中坳陷北侧沙垒田凸起周缘稳定辫状河沉积体系及南侧渤东地区河流漫溢-片流沉积模型；3）应用T2界面处12口井位砂砾岩及玄武岩与凝灰岩精细锆石定年分析，联合界面上下热沉降速率偏转，指明界面处构造变革属性，岩浆活动时限约束及同期碎屑锆石限定T2界面形成年代为22.93±2.78Ma，属下中新统阿启坦阶（Aquitanian）；4）比对中新世初期周缘板块构造事件，锆石的Th/Nb-Hf/Th和Th/U-Nb/Hf构造判别，表明渤海海域广泛分布砂砾岩体及伴生岩浆岩与太平洋板块俯冲东撤相关，周缘强烈挤压及盆内快速热沉降限定约束砂砾岩体区域展布。以砂砾岩及伴生岩浆岩为切入点解析渤海海域新生代成盆动力学机制，有助于完善渤海新生代盆地形成演化，且河湖边界及砂砾岩体沉积性质转换界线拾取可服务渤海海域新生代规模性砂砾岩油气田勘探实践。