When Yangtze plate collided with North China plate in Mid-Late Triassic,large-scale strike-slip motion along Tan-Lu fault took place and this made the area around Yangtze River of Lower Yangtze be under transpression. Therefore, transpressional basin was formed. Huangmaqing Group is the sedimentary record of the basin. Its main features are the following:(1)depocentres in the basin are in enechelon arrangement and thickness difference varies considerably from the centre to the margin which indicates that basement of the basin was intensively flexed and depressed during sedimentary process,(2)sediments are dislocated from their source areas,(3)change of the lithofacies is very sharp and the coarse-elastic lithofacies in the basin margin gradually migrates toward the interior due to gradual constriction of the basin with time,(4)two groups of conjugate shear belts, en-echelon folds and associated thrusts in the basin are the products of transpression. We suggest that the motion of Tan-Lu Fault is dynamics of basin formation.