右江盆地海相泥盆系-中三叠统层序界面成因类型与盆地演化

在右江地区海相层序地层学研究的基础上,将层序界面区分为升隆侵蚀层序不整合界面、海侵上超层序不整合界面、暴露层序不整合界面和造山侵蚀层序不整合界面四个成因类型,并且相同成因类型的层序界面,在盆内不同地域的具体表现形式不尽相同,它们与盆地的成生、发展有紧密的联系,这些界面类型依次反映了盆地的新生、演化和盆山转换过程。

Genesis of Sequence Boundary and Basin Evolution in Youjiang Basin during the Devonian to the Middle Triassic

Based on the research of marine facies sequence stratigraphy in Youjiang basin area, 44 sequences can be distinguished uhich can be divided into 6 ultrasequences,and they respond well to the evolution of the Youjiang basin as well as to basin\|mountain transformation during the Devonian to the early Triassic. The surface of sequence boundary is a negative sedimentary record which depends on the physical property of the sediments below and above the boundaries and/or on the different sedimentary structure. Every sequence surface of boundary represents each sedimentation and tectonic movements in the sedimentary basin because the tectonic movement can enhance or weaken the marks for sequence boundaries. According to the sequence stratigraphy and basin evolution in Youjiang basin, 4 genetic sequence boundaries can be reconstructed during the Devonian to the early Triassic, which suggest different basin evolution stage. They are uplift erosional sequence unconformity, transgressive onlap sequence unconformity, the exposed sequence unconformity and the orogenic erosional sequence unconformity. Uplift erosional sequence unconformity is caused by tectonic uplifting or by sea\|level falling. This unconformity represents isochronous surface of boundary which show the new basin genesis or basin\|basin transformation. Transgressive onlap sequence unconformity is a transgressive surface which show synchronism bewteen tectonic subsidence of basin and sea\|level rising. The exposed sequence unconformity take place in the steady tectonism stage. The orogenic erosional unconformity means that the sequence boundaries may be highlighted by tectonism in the course of the transformation of the basin systems into the orogenic processes.