Palaeoceanological significance of Holocene ostracean banks in Tianjin area

On the basis of the study of ostracean banks in Tianjin area,the present study recognized that the ostracean banks at Ninghe County in Tianjin area are well developed along the west coast of the Bohai Sea; they consist of thanato-coenose and taphocoenose from Crassistrea gigars and C.revularis.From the ¹⁴C datings it can be known that the banks had formed from early Middle-Holocene and continued up to over 2 ka BP (¹⁴C age).The top has different reliefs.Although there is an effect of spatial shift of estuary position,the top is only distributed in the range of -0.50~-2.50 m(Huanghai elevation minus National elevation system).The banks cannot explain the sea-level fluctuation.As the string ostracean banks are distributed near E-W direction,it suggests that the direction of tidal currents was then similar to that of the present day.