Geomorphological Evolution and Mangrove Habitat Dynamics Related to Holocene Sea-Level Changes in the Northern Mekong River Delta and the Dong Nai River Delta, Southern Vietnam pp. 125-141
Authors: Kiyoshi Fujimoto, Masatomo Umitsu, Van Lap Nguyen, Thi Kim Oanh Ta, Kumiko Kawase, Duc Hoan Huynh and Toshio Nakamura
Abstract: This study examines sea-level changes, delta evolution and mangrove habitat dynamics during the mid to late Holocene in the northern Mekong River Delta and the Dong Nai River Delta using new data from 44 boreholes and 29 radiocarbon ages, together with existing data. The sea level was -0.4 ± 0.5 m at ca.7300 cal BP and reached between +1 and +2 m around 6500 cal BP. Sea level at ca. 2000 cal BP was similar to or slightly lower than the present level. Between 7000 and 6000 cal BP, mangrove forests dominated by Rhizophora were distributed approximately 60 to 80 km inland from the present coastline on a delta formed by small rivers flowing from the north. The Rhizophora forests changed into other mangrove forests after 6000 cal BP with sea-level fall and sedimentation. The delta front of the Mekong River reached approximately 140 km inland from the present coastline around 4500 cal BP. Between 4500 and 2500 cal BP, the Mekong River Delta expanded rapidly. After 2100 cal BP, the mangrove forest, which stretched to about 120 km inland from the present coastline, changed to a freshwater environment during a fall in sea level. The Can Gio mangrove forests on the Dong Nai River Delta have formed during the last 2600 years from southwest to northeast with delta evolution and covered their present area by 400 cal BP.
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