长江下游芜湖地区新构造运动基本特点

芜湖地区以长江为界,西北部为冲积平原,东南部为低山丘陵。在低山丘陵区,冲沟多为宽平的"U"型谷。长江沿岸Ⅰ、Ⅱ级河流阶地以堆积阶地为主,局部见有侵蚀阶地。新生代地层主要发育中、晚更新世及全新世地层。新近纪以来,出现2次明显的沉积间断。第1次发生在上新世和第四纪之间,表现形式为洞穴流水沉积间断,溶洞普遍抬升。第2次发生在中、晚更新世之间,表现形式为构造隆升,持续时间约340ka。新生代以来构造运动以升降差异活动为主,断裂活动和褶皱作用不明显。新构造运动的基本特点是继承性、差异性和间歇性。早期活动以继承性为主,晚期活动差异性表现比较突出;而间歇性运动基本上贯穿整个新构造时期。根据地质地貌、断裂活动和测年数据,该区新构造运动的起始时代在上新世末期至第四纪初期。

Basic Features of Neotectonic Movement along the Lower Course of Yangtze River in Wuhu Region

The Yangtze River forms the boundary of the relief,in Wuhu Region.The alluvial plain is to the northwest of the Yangtze River and the hill country is to the southeast of the river.In the hill country,the valleys and gullies are characterized by broad and flat U-type valleys.The terrace Ⅰand the terrace Ⅱ along the Yangtze River are mainly formed by accumulation terraces and partly by erosional terraces.Cenozoic stratigraphy is mainly consists of middle and late Pleistocene series and Holocene series.Since Neogene,two hiatuses occurred.The first hiatus occurred between Pliocene and Quaternary,characterized by the end of running water sediments in the cave and the uplift of all the caves;the second hiatus occurred between the middle and late Pleistocene,characterized by the tectonic uplift which lasted about 340ka.Since Cenozoic,tectonic movement is characterized by the differential movement,and not by faulting and folding.The main features of the neotectonic movement are inherited,differential and intermittent.The inherited movement was dominant at the early period,The differential movement was quite outstanding at the late period,and the intermittent movement ran through all Cenozoic.According to geology,geomorphology,fault activity and dating data,the starting time of the neotectonic movement should be between the late Pliocene and the early Quaternary in Wuhu Region.