Abstract: Anqiu-Juxian Fault(F₅) is the latest active fault in the eastern graben of the middle segment of the Tanlu fault zone. In recent years, the research results of F₅ in Jiangsu Province are abundant, and it is found that Holocene activity is prevalent in different segments, and the movement pattern is dominated by dextral strike-slip and squeezing thrust. The Anhui segment and the Jiangsu segment of the Tan-Lu fault zone are bounded by the Huaihe River. Previous studies have not discussed the extension and activity of F₅ in the south of the Huaihe River in Anhui Province. This paper chooses the Ziyangshan segment of Tanlu fault zone in the south of the Huaihe River as the breakthrough point, which is consistent with the linear image feature of extension of F₅ in Jiangsu Province. Through the remote sensing image interpretation, geological and geomorphological investigation and trench excavation, we initially get the following understanding:(1)The linear structural features of the Ziyang segment are clear, and the fault is developed on the gentle slope of the Mesozoic red sandstone uplift along the Fushan-Ziyangshan, which is the southern extension of the Anqiu-Juxian Fault(F₅); (2)The excavation of the Zhuliu trench reveals that the late Pleistocene clastic layers are interrupted, and the late late Pleistocene to early Holocene black clay layers are filled along the fault to form black fault strips and black soil-filled wedges, indicating that the latest active age of the fault is early Holocene; (3)The excavation of Zhuliu trench reveals that there are at least 3 paleo-earthquake events since the Quaternary, the first paleo-seismic event is dated to the early and middle Quaternary, and the 2nd paleo-seismic event is 20.10~13.46ka BP, the age of the third paleo-seismic event is(10.15±0.05)~(8.16±0.05)ka BP. These results complement our understanding of the late Quaternary activity in the Anhui segment of the Tanlu fault zone, providing basic data for earthquake monitoring and seismic damage prevention in Anhui Province.

Key words: Tanlu fault zone, late Quaternary, Holocene activity, Anhui Province, Ziyangshan

摘要： 安丘-莒县断裂（F₅）为郯庐断裂带中段东地堑内最新活动断裂。近年来，F₅江苏段研究成果丰硕，发现不同地段普遍存在全新世活动性，运动方式以右旋走滑兼挤压逆冲为主。以往研究未讨论过F₅在淮河以南安徽境内的延伸情况以及进一步的活动性问题。文中选取与F₅江苏段线性影像特征延伸一致的淮河南岸郯庐紫阳山段作为突破口，通过遥感影像解译、地质地貌调查和探槽开挖，初步得到以下认识：1）紫阳山段线性构造地貌特征清晰，断层发育于浮山至紫阳山一线的中生代红色砂岩隆起边缘缓坡，为安丘-莒县断裂（F₅）过淮河后的南延部分；2）朱刘探槽开挖揭示，该段错断了晚更新世晚期黏土层，晚更新世晚期-全新世早期黑色黏土层受断层活动影响沿断面灌入、填充，形成黑色断层条带及黑土充填楔，表明断层最新活动时代达全新世早期；3）朱刘探槽开挖揭示，该段第四纪以来存在至少3次古地震事件，第1次古地震事件推测年代为第四纪早、中期，第2次古地震事件年代为20.10~13.46ka BP，第3次古地震事件年代为（10.15±0.05）~（8.16±0.05） ka BP。上述研究成果弥补了对郯庐断裂带安徽段晚第四纪活动性认识的不足，为安徽省的地震监测和震害防御工作提供了基础数据。

关键词: 郯庐断裂带, 晚第四纪, 全新世活动, 安徽, 紫阳山