SEDIMENTARY TEXTURES AND ENVIRONMENTS OF THE HANGZHOU BAY
Liu Cangzi Dong Yongfa (Institute of Estuarine and Coastal Research, East China Normal University, Shanghai,China, 200062)
The Hangzhou Bay is a typical macrotidal estuary. Its modern sedimentation is controlled by funnel-shaped topographic configuration, strong tidal currents and silt suspension from the Changjang River estuary. Changes of sedimentary textures are mainly restricted by intensity of the tidal currents. According to the sedimentary textures of bottom sediments and hydrodynamic conditions, the following sub-environments can be identified in the Hangzhou Bay: east part of the bay bottom, west part of the bay bottom, Andong shoal, nearshore deep channel and tidal sand ridges. This paper expounds sedimentary texture characteristics and formation mechanism of the different sub-environments, probes what causes the tidal sand ridges (typical sand bodies in the macrotidal estuary) to poorly develop in the Hangzhou Bay, and also points out that it is difficult to build up sand ridges without sufficient coarsegrained sediments, although tidal current is strong enough.