酒西盆地青南凹陷柳沟庄-窟窿山地区下白垩统震积岩的发现及意义

在甘肃省酒西盆地青南凹陷柳沟庄-窟窿山地区下白垩统下沟组及中沟组地层序列中,首次发现发育一套地震事件沉积物,是一套含微裂缝或同生变形构造及振动液化泄水构造等震积特征的泥质白云岩、白云质泥岩及泥质粉砂岩的组合.本区震积作用及震积岩的主要识别标志为振动液化卷曲变形及其伴生构造、重荷模及伴生构造、脆性和塑性两类沉积物相间的滑塌变形作用及滑塌岩、软沉积物的液化作用及泄水构造、层内阶梯状断层及地裂缝.柳沟庄-窟窿山地区下白垩统震积岩的发现,填补了本区震积岩研究的空白,反映了本区在早白垩世存在一个强烈的构造活动时期,可以推测其影响范围可能还会波及青南凹陷的其他地区,也有望在酒西盆地类似环境的其他凹陷发现震积岩,开辟震积岩研究的新领域.区域构造背景的研究同样表明,青南凹陷青西Ⅰ号同生断裂带及509断阶带的强烈构造活动正是本区早白垩世震积作用的直接诱发因素,为本区震积岩的存在提供了科学依据.

The Discovery of Seismite and Its Significance in Lower Cretaceous in Liugouzhuang and Kulongshan Region, Qingnan Sag, Jiuxi Basin

A set of seismo-deposition and seismites are discovered for the first time in the Lower Cretaceous Xiagou Formations and Zhonggou Formations in the Liugouzhuang and Kulongshan region, Qingnan Sag, Jiuxi Basin. They are combined sediments of argillaceous dolomite, dolomite-mudstone and argillaceous siltstone, with seismo-deposition characteristics such as fissure, synsedimentary deformation structure, vibratory-liquefied water-escape structure. In this area, the main recognized marks of seismo-deposition and seismites include vibratory-liquefied curl deformation, load cast and their associated structures, slump deformation between brittle and plastic sediments and slump turbidites, liquefaction of soft sediments and water-escape structure, and step intrabed faults and geofractures. The discovery of seismo-deposition and seismites in the Lower Cretaceous in the Liugouzhuang and Kulongshan region filled up the blank of the seismites study in this area and indicates that intense earthquake activity once occurred during the Lower Cretaceous period, based on which it could be presumed that the earthquake could affect other areas in the Qingnan Sag. In addition, seismite is expected to be discovered in other sags with resemble tectonic settings in the Jiuxi Basin and thus opening a new study field of seismite. The study of regional tectonic settings also shows that the intense tectonic activities of the Qingxi No. 1 and 509 synsedimentary faulted zones are the direct inducing factors of the seismo-deposition in the Lower Cretaceous in this area, which presents a scientific proof for the existence of seismites.