Sandwaves on the Southeast Vietnam Shelf recorded by high resolution seismic profiles: formation and mechanism

Abstract

The application of high resolution seismic data using boomer sound source has revealed a wide distribution of large-scale bedforms (sandwaves) on the Southeast Vietnam continental shelf. Bedforms that are a few meters high in wave height and hundreds of meters long in wavelength are primarily developed in the inner shelf (20-40 m) and considered to be formed under the present-day marine hydrodynamic conditions. Those bedforms developed in the deeper water (120 m) of the northernmost part of the continent can be interpreted as the relict morphological features formed during the latest sea-level lowstand of the late Pleistocene period. Two sediment transport paths have been identified on the basis of the bedform’s leeward orientation: northeast-southwest (along-shore) and north-south (cross-shore). A quantitative bottom current map is constructed from sandwave dimensions, surface sediments and measurement data. The strongest current velocities that gradually decrease toward the southwest are indicated by large sandwaves in the north (field B). Water depth, surficial sediment composition and bottom current are three factors that control the development of bedforms.

Keywords

bedforms / sandwaves / bottom currents / Southeast Vietnam Shelf

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Acknowledgements

This work was completed as the final part of a Master’s study in University of Kiel, Germany of Dung BV, funded by the Vietnamese Ministry of Education and Training and German Academic Exchange Service (Deutsche Akademische Austauschdienst—DAAD). The authors wish to thank Professor Zhongyuan Chen and Dr .Zhanghua Wang for invaluable critical comments on the earlier versions of the manuscript.

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