Holocene Delta Evolution and Depositional Models of the Mekong River Delta, Southern Vietnam
Thi Kim Oanh Ta, Van Lap Nguyen, Masaaki Tateishi, Iwao Kobayashi, Yoshiki Saito, 2005. "Holocene Delta Evolution and Depositional Models of the Mekong River Delta, Southern Vietnam", River Deltas–Concepts, Models, and Examples, Liviu Giosan, Janok P. Bhattacharya
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The Mekong River Delta in southern Vietnam is a typical mixed tide- and wave-dominated delta with a wide delta plain formed during the last 6 to 8 ky. The late Pleistocene-Holocene sequence in this region since the last sea-level lowstand is composed of an incised- valley fill, comprising late Pleistocene to early Holocene fluvial to estuarine sediments, and Holocene deltaic sediments. The deltaic sediments are composed of early Holocene aggradational sediments and progradational sediments of middle to late Holocene age.
The progradational delta has evolved from a tide-dominated delta to the present mixed wave- and tide-dominated delta during the last 3 ky and shows a sudden regime shift of coastal environment. The tide-dominated delta was characterized by a well-developed mangrove forest on the subaerial delta plain, cross-shore sediment dispersal, and tide-influenced sedimentary facies. The tide- and wave-dominated delta exhibits a beach-ridge system in the subaerial delta plain, longshore sediment dispersal, and a steep delta-front topography, in which the sediments of the proximal river-mouth area are coarse-grained and those more distal are fine-grained.
As river-mouth coastal systems evolve from estuaries to deltas in response to sea-level changes, the formation of a tide-dominated delta marks the initiation of the highstand systems tract.
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Deltas are amongst the most environmentally and economically important coastal sedimentary environments. Studies of deltas lag behind research in both fluvial and deep-water depositional systems, as well as more geomorphologically oriented land studies. This knowledge lag reflects both a reorientation of the petroleum industry in the last two decades toward deep-water systems, as well as the difficulty of working across the shoreline with the traditional tools used for oceanographic or land-based work. However, deltaic studies are experiencing a renewed focus, because of their global importance in environmental and other societal concerns. This volume stems from a special session: Deltas: Old and New, held at the Annual Geological Society of America conference in October 2002, that was convened to highlight these new directions in deltaic research.