Land-Sea Sedimentary Facies Transition at the Mouth of a Small Mountain River on the West Coast of Taiwan Since 50,000 yr BP
Abstract:
These transitions indicate that the paleo-river mouth began to develop a transgressive-estuarine system at 10,000 yr BP, when the paleo-river mouth was inundated by the rising sea. The sediments that were come from Zhuoshui River accumulated slower than the sea-level rise. This resulted in gradually deeper environment. The evidence of maximum flooding surface (MFS) suggests transgression progressed until 5700 yr BP. Combined with findings from previous studies the position of MFS display a shallowing trend from the south to north. This implies that the deposition rate in the north was higher than that in the south. Therefore it is reasonable to assume that the paleo-river mouth was located north to the present position. After the sea level became stable, because of large terrestrial sediments discharge the paleo-river mouth was soon switched from a transgressive system to an aggradational delta system.
The Zhuoshui River delta, unlike many well-known river delta systems, is limited by the depth of the Taiwan Strait. Shallow water depth and energetic hydrodynamics result in the non-deposition of muddy sediments near the river mouth. This caused the absence of thick muddy prodelta deposits in the upper part of the JRD cores. This caused the absence of thick muddy prodelta deposits in the upper part of the JRD cores. Moreover, the offshore morphology influenced the tidal current that become parallel to the shoreline in a short distance from the shore. The currents enabled the delta to develop a parallel coast tidal ridge at the delta front. This creates a unique depositional model for the Zhuoshui River delta.