大别山北缘合肥盆地中、新生代构造演化

TECTONIC EVOLUTION OF HEFEI BASIN, NORTHERN DABIE MOUNTAIN IN THE MESOZOIC AND THE CENOZOIC

合肥盆地中、新生代经历了多次沉降和隆升变化，侏罗系沉积作用分布于整个盆地，中、晚侏罗世盆地内地层遭受广泛剥蚀。白垩纪沉积物局限于盆地东部，最大剥蚀区在盆地东南部。下第三系沉积集中于断裂带控制的断陷盆地中，剥蚀主要在盆地东部和南部。根据南北向平衡剖面分析，早侏罗世盆地为南北挤压，晚侏罗世盆地拉张松驰形成东西向断层；白垩纪受东西向挤压，早第三纪为南北向拉张。东西向平衡剖面分析表明：在盆地内存在一条规模巨大的南北向巨型隆起，隆起形成于早白垩世早期延续到晚白垩世晚期。盆地经历了早侏罗世前挤压推覆，侏罗白垩纪松驰下陷，白垩纪盆地西部及中部隆升，晚白垩世－早第三纪盆地受南北向拉张作用，形成北断南超的箕状断陷盆地；晚第三纪挤压隆升。

Analysis of sedimentation and erosion of the Hefei basin has demonstrated that the basin experienced multi stage depression and uplifting in the Mesozoic and Cenozoic Era. The Jurassic stratum was distributed in the whole basin, however, the Middle to Late Jurassic stratum experienced extensive erosion. The main erosion area is lacated in the middle and western parts, the trend of erosion contours is of a SN direction. The Cretaceous sedimentation was limited within the eastern part of the basin and the main erosion area is located at the east southern part. The sediments of the Eogene were distributed in the faulted basins controlled by the Dingyuan, Hanbaidu and Tanlu faults. The erosion centers were located in the eastern and southern parts. The erosion centers changed with time, and were controlled by the tectonic framework. According to the SN balance section, the basin compressed in the SN direction at the Early Jurassic, then relaxed and extended to form the EW faults at the Late Jurassic. The basin compressed in the EW direction during the Cretaceous, then extended in the SN directon at the Eogene. The EW balance section suggests that there are a great uplift ridge crossing the Shushan fault and Feizhong faults from Fanghushan in the south to Shoxian in the north.The great uplift formed in the Early Cretaceous, and existed until the Late Cretaceous. The Hefei basin was the backarc foreland basin resulted from Dabie orogen compression. It experienced the compression thrust during the Early Jurassic, and the relaxation during the Jurassic to the Cretaceous. During the Jurassic, there was a wide sedimentation. The sedimentary center migrated from south to north. During the Cretaceous the west and center part of the basin was uplifted, while the east part was a depression area. The sedimentary center was near the Tanlu fault. During the Late Cretaceous to the Neogene, the basin was extended along the SN direction and the faulted basin was formed.