渤海西部中新生代多旋回构造演化与潜山形成

    MESO-CENOZOIC MULTICYCLIC TECTONIC EVOLUTION AND ITS BEARING ON THE FORMATION OF BURIED HILL SYSTEMS IN THE WESTERN BOHAI SEA

    • 摘要: 渤海西部中新生代演化具有频繁的构造体制转换和鲜明的旋回性,从而决定了潜山地质结构和内幕构造的多样性和复杂性。在地震资料精细解释基础上,运用构造解析的方法,以构造变形、构造期次划分和古应力场分析为主线,重建研究区中新生代多旋回构造演化序列。另一方面,从潜山内幕残留地层和断裂特征入手,解剖潜山的地质结构,识别和划分了研究区潜山构造样式和成因类型。研究表明,渤海西部中新生代存在印支、早燕山、中燕山、晚燕山、早喜山、晚喜山6个构造旋回,相应地潜山的形成经历了前印支期潜山物质基础发育、印支—早燕山旋回挤压逆冲与潜山雏形、中燕山—早喜山旋回伸展裂陷与潜山初始格局、晚喜山旋回断-拗沉降与潜山定型定位四大演化阶段。各个旋回构造变形的时空差异以及叠加组合方式的不同导致研究区潜山构造特征呈现明显的分带性,自西向东可划分为西侧内幕残留逆冲型、中部反转块断翘倾型和东部复杂走滑断块型潜山带。

       

      Abstract: The Meso-Cenozoic tectonic evolution of the western Bohai Sea is characterized by frequent change in tectonic regimes and distinct cyclicity, which caused the formation of diversified and complex buried hills. On the basis of fine interpretation of seismic data, this paper is devoted to the reconstruction of the multicyclic tectonic evolutionary history of the study area during the period of Meso-Cenozoic using the method of structural analysis. Structural deformation, tectonic stages and definition of paleostress field are also studied in details. Starting from remained strata and fracture systems in buried hills, the geological structure of the buried hills is carefully dissected, and the structural style as well as genetic types of the buried hills identified and divided. It is found that there are six tectonic cycles in the region during Mesozoic and Cenozoic, i.e. Indosinian, early Yanshanian, Middle Yanshanian, Late Yanshanian, Early Himalayan and Late Himalayan epochs. Accordingly, the buried hills have experiencecl four stages of evolution, which includes the formation of material basis in the pre-Indosinian epoch, the formation of embryonic form of buried hills by thrusting and napping in the Early Yanshanian epoch, inceptive tectonic framework by tensional rifting in the Middle Yanshanian to Early Himalayan epoch, and the accelerated faulting and subsiding in the Late Himalayan epoch. The structural characteristics of buried hills in the study area are obviously zonal due to the space-time differentiation of tectonic deformation and stacking patterns in each cycle. From west to east, the buried hills can be divided into three types, i.e. inner residual thrust type, reversal block-fault tilting type and complex strike slip fault-block type.

       

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