浙江永康盆地朝川组震积岩发育特征及其地质意义

Development characteristics and geological significance of the seismites of Chaochuan Formation in Yongkang Basin,Zhejiang Province

浙东永康盆地北东段朝川组中上部发现多期地震活动的记录,赋存于湖相灰黑色泥灰岩、钙质泥岩与紫红色粉砂质泥岩和粉砂岩互层地层中。识别出的地震活动标志为多种原地成因的震积岩,主要包括层内微断层、震裂角砾岩、液化砂岩脉、碟状构造、液化角砾和液化卷曲变形。通过对震积岩及震积序列特征分析,结合浙东地区构造背景,认为朝川组中上部地震事件与早白垩世晚期盆地控盆断裂的活动有关,是区域构造-沉积由稳定补偿沉积阶段转为抬升剥蚀阶段的启动标志,并具良好等时性意义,是陆相盆地沉积地层划分对比的重要标志。

Some seismic records were found in marlstone interbeds,including grey and black lake facies marlstone,calcilutite,silt mudstone and siltstone in Chaochuan Formation at the northeastern part of Yongkang Basin.The seismites of varied autochthony are the seismic motion signs in the study area. Typical structures of the seismites included micro-fault,seismic fissure bed,liquefied breccia,liquefied vein,dish structures and liquefied convolute. Through the analysis of seismite and its sequence,and combined with the tectonic background of East Zhejiang,the authors supposed that the earthquake events in the middle and upper Chaochuan Formation could be related with the basin-controlling fault activity during the late period of Early Cretaceous. These represent the regional structural-sedimentary transformation from stable compensation deposition period to uplift-erosion period,and are of isochronous and important significance for the stratigraphic division of terrestrial facies basin.