莱阳凹陷莱阳群层序特征及其对走滑活动的响应

Sequence character of Laiyang group and strike-slip tectonics in Laiyan depression

本文基于前人研究成果,利用莱阳凹陷较完整的地质露头、地震和钻井岩心等资料,在莱阳凹陷莱阳群共识别出2个区域性不整合界面SB1、SB3,1个局部不整合面SB2,将莱阳群作为一个二级构造层序,以其内部的次一级局部不整合面SB2为界,分为SQ1(瓦屋夼组)、SQ2(止凤庄组—曲格庄组)两个三级层序。根据SQ2内部层序结构及其沉积特征,将其划分为低水位体系域、水进体系域和高水位体系域,反映了由走滑强烈拉张经走滑拉张相对平静向走滑挤压转化的构造演化过程,主要表现为冲积扇和冲积扇—冲积平原—河流相沿桃村—东陡山断裂向北东方向不断迁移,并导致莱阳凹陷东北部的抬升和剥蚀。

Based on previous studies,integral outcrops,seismic data,and core data,we identify two regional unconformities(SB1,SB3) and one local unconformity(SB2) in the Laiyang group of Laiyang depression.Considering the Laiyang group as one second-order tectonic sequence,we divide the Laiyang group into two third-order sequences,SQ1(Wawukuang formation) and SQ2(Zhifengzhuang formation-Qugezhuang formation) separated by SB2 local boundary.According to its internal sequence architectures and depositional characteristics,SQ2 is divided into lowstand system-tract,transgressive system-tract,and highstand system-tract.This represents the tectonic evolution process from intensive strike-slip extension through relative quiet strike-slip extension to strike-slip compression.It presents that alluvial fan facies-alluvial plain facies-fluvial facies gradually migrated towards the NE direction along the Taocun-Dongdoushan fault,and it caused the northeastern depression uplifting and to be eroded.