渤海湾盆地旅大隆起区多期叠加构造及其对潜山的控制作用

Multistage structural superimposition and its control on buried hills in the Lyuda uplift zone,Bohai Bay Basin

旅大隆起区位于渤海湾盆地渤海海域的西北部,经历了中生代—新生代多幕构造运动的叠加改造,内幕断裂发育类型多样、变形复杂,前人对其古生界和中生界的构造研究仍相对薄弱。基于三维地震数据的详细构造解析揭示,研究区印支期主要表现为自南向北的逆冲推覆,形成了北西—近东西向的宽缓褶皱和逆冲推覆断裂;燕山早期和中期主要表现为挤压背景下的局部伸展和沉积,中-下侏罗统和上侏罗统-下白垩统之间未见明显的角度不整合;燕山晚期主要表现为自南东往北西方向的逆冲推覆;早喜马拉雅期在北西-南东向的伸展作用下形成了多米诺式的伸展-拆离断层和箕状断陷沉积。其中,印支期北西—近东西向的逆冲断层控制了研究区的基底构造格局,后期的燕山运动和早喜马拉雅运动继承或改造了早期的断层系统。晚白垩世是旅大隆起区构造格局转变的关键时期,自之前的北西—近东西向转为北东向。位于构造转变区的秦皇岛30-1构造和旅大25-1构造潜山是印支期近南北向挤压、燕山晚期北西-南东向挤压和早喜马拉雅期北西-南东向伸展叠加改造的结果,而南部的428构造潜山则受控于近东西走向的印支期逆冲及燕山期和早喜马拉雅期伸展断裂体系。

The Lyuda uplift zone,situated in the northwestern Bohai Sea area,Bohai Bay Basin,experienced multiphase tectonic events in superimposition during the Mesozoic-Cenozoic,leading to the formation of various interior faults with intricate deformations.However,the Paleozoic and Mesozoic structures within this zone remain understudied.Based on a detailed structural analysis with 3D seismic data,this study presents the following findings.(1) The Lyuda uplift zone predominantly experienced top-to-north thrusting during the Indosinian,forming NW-to nearly EW-trending open folds and thrust-nappe faults;(2) The uplift zone primarily underwent localized extension and deposition under compression during the Early and Middle Yanshanian,with the absence of significant angular unconformity between the Middle-Lower Jurassic and the Upper Jurassic-Lower Cretaceous strata;(3) The uplift zone principally experienced top-to-northwest thrusting during the Late Yanshanian;(4) The uplift zone witnessed the emergence of domino-style extensional-detached faults and the deposition in half grabens due to NW-SE directed extension during the Early Himalayan.Among these structures,the Indosinian NW-to nearly EW-trending thrust faults shape the basement tectonic framework for the Lyuda uplift zone,while the Late Yanshanian and Early Himalayan movements either inherited or modified the earlier fault system.The Late Cretaceous marked a pivotal transition for the Lyuda uplift zone's tectonic framework from trending NW to nearly EW to NE.The Qinhuangdao 30-1 and Lyuda 25-1structural buried hills,located in the tectonic transition zone,emerged from the superimposition of the Indosinian nearly S-N directed compression,the Late Yanshanian NW-SE directed compression,and the Early Himalayan NW-SE directed extension.In contrast,428 structural buried hill in the south is controlled by the nearly E-W-trending thrust during the Indosinian and the extensional fault system during the Yanshanian and Early Himalayan.