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

doi:10.1007/s11707-009-0002-z

Front Earth Sci Chin

0, Vol.

Issue () : 9-20 https://doi.org/10.1007/s11707-009-0002-z

Research paper

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

Viet Dung BUI^1,2(

), Schimanski ALEX², Stattegger KARL², Van Phach PHUNG¹, The Tiep NGUYEN¹, Tien Hai NGUYEN¹, Trung Thanh NGUYEN¹, Truong Thanh PHI¹

1. Institute for Marine Geology and Geophysics, 18 Hoang Quoc viet, Hanoi, Vietnam; 2. Institutes of Geosciences, Kiel University, D-24118, Kiel, Germany

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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

Corresponding Author(s): BUI Viet Dung,Email:buivietdungspt@yahoo.com

Issue Date: 05 March 2009

Cite this article:

Viet Dung BUI,Schimanski ALEX,Stattegger KARL, et al. Sandwaves on the Southeast Vietnam Shelf recorded by high resolution seismic profiles: formation and mechanism[J]. Front Earth Sci Chin, 0, (): 9-20.

URL:

https://academic.hep.com.cn/fesci/EN/10.1007/s11707-009-0002-z
https://academic.hep.com.cn/fesci/EN/Y0/V/I/9

Fig.1 Regional map of the South East Vietnam Shelf Bathymetry modified after Que et al. (). Seismic profiles (red lines) and grab sediment samples (yellow circles). Black lines indicate seismic profilesβemployed in this paper.

Fig.2 Surface current circulations on the South China Sea in June (left) and December (right) (modified after )

Fig.3 Fields of sandwave distribution (pink cross area). Red arrows indicate sandwave orientations. Grab samples (green circles) contain high content of fine sediment (<0.063 mm) and seismic profiles reveal sandwaves (brown lines). Letters show name of sandwave fields

Tab.1 Significant parameters of sandwave recorded by high resolution seismic

Fig.4 Example of sandwaves in field A (a) and B (b) in the north of the study area revealed by seismic boomer profiles

Fig.5 Example of sandwaves in field C (a) and D (b, c, d) in the north of the study area revealed by seismic boomer profiles

Fig.6 Example of sandwaves in field E (a) and F (b) in the north of the study area revealed by seismic boomer files

Tab.2 Estimated bottom currents for different parts on the SE Vietnam Shelf.

Tab.3 In-situ measurement data (). Locations of stations are showed on Fig. 9.

Fig.7 Statistical analysis of sandwave dimensions on the SE Vietnam Shelf and their comparison to the mean global data of Flemming ()

Fig.8 Scatter plot of sandwave dimensions and water depth (a and b). Correlation between median sediment grain size (black) and sandwave dimensions (red) in the north and central part (c and d)

Fig.9 Bottom currents estimated from sandwave dimensions and in-situ measurements on the South East Vietnam Shelf. The black squares show locations of mooring stations

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