Sedimentary facies and evolution in the Qiantang River incised valley, eastern China

During the deposition of the floodplain-estuary facies, the conditions of sea level rise, tidal regime, sediment supply and accommodation space were suitable for the development of a tidal ridge system; the sand lenses associated with this facies may represent a tidal ridge system in the incised valley. At the later stage when the estuarine sand bars were formed, the sedimentary conditions were no longer favourable, resulting in absence of sand ridge deposits. Biogenic gas is stored in the floodplain-estuary sand lenses of the incised valleys. The Changjiang River provides the major sediment supply for the QR estuary sand bar, and the QR carried sediments constitute only a small portion of the deposits.