关键词: 第四纪, 断裂活动性, 安徽, 头坡断裂

Abstract: The Toupo Fault,located in the southern Anhui Province,strikes N60°～70°E in a linear route that is clear on satellite image. It plays an important role in controlling the tectonics,topography and distribution of Mesozoic-Cenozoic basins and strata. Detailed field investigation was carried out along the Toupo Fault about its activity. Profiles as well as a trench excavated reveal that the Quaternary superstratum above the fault has not been offset. The stratum was sampled and dated with TL methods to be the Mid-Pleistocene time,implying that the fault has been no longer active since then. Three stages can be divided since the fault was formed,namely,the first stage (late Yanshan Movement),when the fault movement was of reversal left-lateral strike-slipping and the tracks formed then are still clear today; the second stage (early Himalayan Movement-the late Cretaceous-early Tertiary),when the fault movement turned to be normal faulting and the southern wall became a tensile basin and received clastic sediments; and the third stage (since the late Tertiary),when the tectonic movement was very week. No late Tertiary sediments were formed and the Quaternary sediment is only as thick as tens meters. The topography also suggests an old-age form. Neither vertical nor horizontal displacement was evident along Toupo Fault during this stage,though fault gouge dating suggests the Toupo Fault might have been active during the Middle Pleistocene.

Key words: Quaternary, fault activity, Anhui, the Toupo Fault