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Investigation of Marine Sediments with a Subbottom Profilers System in West Coast of Camau, Vietnam

Dung Nguyen Quang, Giang Nguyen Van, Thanh Le Ngoc

Inżynieria Mineralna

2023

no. 2, vol. 1

215--223

The west coast of Camau (Southeast Vietnam) connects two semi-enclosed East Sea and Thailand Bays, allowing water exchange between them. Despite its importance to the oceanographic evolution of the region, it has still been poorly studied. Therefore, Subbottom profilers are used across shallow sea waters with some applications, such as sea-level studies, sedimentation process and geomorphology. In the whole survey area, 6 high-resolution shallow seismic measurements have been performed with a total length of 60.6 km, and all have recorded good reflected signals in the range 20–70 ms. In this section, physical characteristics and nature of petrology in the survey environment are quite uniformly shown. The topography of the seabed in the survey area tends to be gradually shallower from west to east, and is relatively flat. Particularly, on the cross section of the T1 line, it is visible that the first section of the line has a rather steep and deep terrain, which may be the slope of the continental shelf in the survey area. Wedge-shaped, oblique, corrugated and transverse structures all appear on the cross-sections. In the survey area, the shallow geological structure in the Holocene sediments is divided into 4 layers, and the structural boundary between the Holocene and Pleistocene sediments at the depth of 25–35 m is observed. In addition, geological faults are also detected on geological sections from seismic sections. For instance, at the section of T6 line, two faults were detected at the beginning of the line. The displacement amplitude of these faults ranges between 1.5–4 m. This new dataset will contribute to future comprehension of the geologic and oceanographic evolution.

Application of artificial storage, recharge for semi-arid area in BacBinh Vietnam

Giang Nguyen Van

Archives of Mining Sciences

2022

Vol. 67, no. 1

37--53

BacBinh is a sand dune area located in the southern part of central Vietnam. This area is confronted with a lack of water supply. The project aims to investigate the site for artificial recharge (AR) and the management of aquifer recharge (MAR) in the sand dune area. The geological setting of the area is characterised by ryo-dacitic bedrock, which forms steep isolated hills (up to 300 m a.s.l.) overlain by a Pleistocene-Holocene marine sand dunes plateau (up to 200 m a. s. l.). This is represented by prevailing white fine sand (Pleistocene) and prevailing red sand (Holocene), which occurs extensively in the coastal area. The hydrological and geological conditions are investigated by collecting all existing data of aerial and satellite photos, rainfall statistics, morphological/geological/ and hydrogeological maps for acquisition and interpretation. The field geophysical surveys are carried out for the location of groundwater aquifers to site selection, monitoring and operation of groundwater recharge. Hydrochemical and isotopic characterisation of surface water and groundwater in different periods showed that the sand dunes aquifers, with electrical conductivity ranging from 100 to 400 μS/cm, are composed of different water types, characterised by complex mixing processes. The site chosen for the artificial recharge, where 162 days of pumping tests have been carried out, proved that the use of the bank filtration technique has considerably improved the quality of water, which was originally highly contaminated by E-coli bacteria. The well field developed within the present project is now capable of supplying 220 m3/day of good water quality to the HongPhong community, BacBinh district, which were recurrently affected by severe droughts.