Did higher sea-level result in tropical cyclone overwash of high dunes on the coast of Vietnam in the mid-Holocene? Tentative results from the Cam River mouth, Vietnam.

Authors: Harry Williams*, University of North Texas, Long Van Hoang, Hanoi University of Mining and Geology, Hiep Huu Nguyen, Hanoi University of Mining and Geology, Ha Manh, Hanoi University of Mining and Geology, Patrick Elliott, University of North Texas
Topics: Coastal and Marine, Geomorphology, Hazards, Risks, and Disasters
Keywords: paleotempestology, highstand, beachrock, overwash, washover, Vietnam.
Session Type: Paper
Day: 4/12/2018
Start / End Time: 1:20 PM / 3:00 PM
Room: Napoleon D1, Sheraton 3rd Floor
Presentation File: No File Uploaded

A freshwater coastal wetland near the mouth of the Cam River in northern Vietnam stands about 2 m above mean sea level and is bordered by dunes that reach about 6 m above mean sea level. Although the height of the dune barrier makes tropical cyclone overwash seem unlikely at this site, a core from the wetland contains a 10-cm-thick sand and shell layer tentatively identified as a washover deposit. A clue to the possible origin of this deposit is found on the adjacent beach in the form of a beachrock standing above the modern beach and reaching to about 4 m above mean sea level. A tentative explanation of this beachrock is that it represents a beach that formed during a mid-Holocene sea-level highstand, evidence for which has been reported from Thailand, Malaysia and southern Vietnam. The sand and shell layer is tentatively identified as a mid-Holocene washover deposit. The lack of more recent washover deposits in the core suggests that the fall in sea level after the mid-Holocene has prevented additional tropical cyclone overwash at this site.

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