山东临朐红丝石层中的古地震事件记录

红丝石是产于山东临朐中奥陶统下部的一类具红色丝线状弯曲纹层的用于加工工艺品(砚台、笔筒等)的微晶碳酸盐岩。产有红丝石的这部分地层,厚约60m,被称为“红丝石层”。根据野外观测、室内鉴定及地震地质对比,从临朐红丝石层中识别出了具卷曲变形(包括塑性和半塑性变形)、环形纹层变形、微断裂(包括阶梯状和共轭微断裂)、震裂隙和震碎角砾等地震成因岩石构造的震积岩层。这些震积岩是中奥陶世古地震事件的记录,红丝石仅是古地震作用形成的一种常见的震积岩,由于在中奥陶世郯庐带内也有震积岩生成,因此认为这些地震记录是古郯庐带在中奥陶世强烈活动的证据。

Records of paleoseismic events in the red-silk stone bed in Linqu, Shandong

Red-silk stone is a kind of microcrystalline carbonate rocks with red silk thread-like curled laminations used for carving stone handicrafts (ink slabs, brush pots etc.), which occurs in the lower part of the Middle Ordovician in Linqu, Shandong. The portion of strata containing red-silk stone, about 60 m thick, is named "red silk stone bed". Based on field observation, lab examination correlation of seismic structures, seismite layers with seismogenetic structures such as curl deformation (including plastic and semi-plastic deformations), circular laminations, microfractures (including ladder and conjugated ones), vibration fissures and shattered breccia are recognized in the red-silk stone bed. These seismites are records of Middle Ordovician paleseismic events. Red-silk stone is only one of common seismites formed by paleoseismism. As seismites also formed in the Middle Ordovician Tanlu zone, it is considered that these seismic records are evidence of the intense tectonic activity of the Paleo-Tanlu fault at that time.