NEW DATA ON
BASALTS IN THE BOTTOM
OF THE SOUTH CENTRAL VIỆT NAM CONTINENTAL SHELF
TAKEN BY CRUISES VG-05
1NGUYỄN TIẾN HẢI, 2K.
STATTEGGER
1Institute of Marine
Geology and Geophysics (IMGG), Việt
2Institute of Geosciences
of
Abstract: Within the framework of a Scientific Research
Joint Project between Institute of Marine Geology and Geophysics (IMGG, Việt
Nam) and Institute of Geosciences of Kiel University (CAU, Germany), an
expedition has been carried out by VG-05 cruises during the year 2004 in the
East Việt Nam Sea. The interpretation of new data taken by this cruise along
high resolution shallow seismic profiles has defined some volcanos/diapirs
(basalts, mouths) in the bottom of the South Central Việt
- A volcano on profile 10050403 (about 108o.7891
E and 10o.5960 N, having diameter of about 800 and 2.400 m) in the
bottom of the Vũng Tàu - Bình Thuận continental shelf (in the northeast
vicinity of Hòn Tro volcano island).
- A volcano on profile 09050403 (about 108o.8699
E and 10o.2528 N, having diameter of about 700 m) in the bottom of
the Vũng Tàu - Bình Thuận continental shelf.
- A volcano on profile 14050407-14050420
(diameter of about 150 m, 400 m and 10 km) in the bottom of the Vũng Tàu - Bình
Thuận continental shelf.
- A volcano on profile 15050401-15050411
(diameter of about 5 km) in the bottom of the Vũng Tàu - Bình Thuận continental
shelf.
- A volcano on profile 28050415 (about 109o.3566
E and 12o.3568 N, having diameter of about 320 m) in the bottom of
the of Nha Trang continental shelf.
I. INTRODUCTION
The continental shelf off the southeast
Vietnamese coast has extension of varied dimensions: in the vicinity of the
The results of this study aim to provide with
the principal knowledge on the geologic history and evolution of the
SE-Vietnamese coastal zone over the last 10,000 years. In addition, these
results should support planning strategies for integrated coastal zone
management with respect to sustainable development. Reference should be given
to competing interests between potential users of the coastal zone, e.g.
tourism, fisheries, exploitation of mineral resources.
The studied region is located at the borders
of the Sundaland continental plate and is assumed to be tectonically stable
during the Quaternary (Tjia & Liew, 1996). An important dislocation, termed
as the 110º-fault runs parallel to the Vietnamese coast reaching the study area
in the east. Two fault zones in the region of Nha Trang trending SW-NE join the
110º-fault (Fontaine & Workman, 1997). They were formed by the SE movement
of the
The coastal zone in SE Việt Nam shows a
variety of morpho-structural types and landforms which are genetically related
to different types of coastline comprising sea terraces, sandy coasts, salt
water swamps, erosional and denudation-accumulation coastal plains, basaltic
plateaux, inselbergs. The volcanic activities in
the region began and developed along regional rifts in the activated period of
late Cenozoic magma in the
Widespread volcanic activities of basaltic
and basanitic type persisted during Tertiary and Quaternary times. The last
large eruption was noted in 1923 on the continental shelf in the area of
II. MATERIAL AND METHODS
The project “Holocene coastal evolution,
sea-level fluctuations, terrigenous sedimentation and sediment dynamics on the
continental shelf between the Mekong Delta and Nha Trang, SE Việt
The sea floor of the Việt Nam continental
shelf was surveyed using the shipboard parasound system to characterize
sea-floor morphology and geometry of subsurface seismic reflectors, as well as
to ensure coring at suitable locations. Using the parametric effect, the system
emits two different frequencies of 18 kHz and 20.5-23.5 kHz, generating a
working frequency of 2.5-5.5 kHz. These results in narrow beam characteristics
return a well resolved signal of the sea-floor and subsurface reflectors with a
penetration of up to 150 m, depending on bottom characteristics. Correlation of
sedimentary strata with similar physical characteristics is thus simplified and
the lateral extent of sediment bodies is traceable. In combination with ground
truthing by sedimentological and geochemical investigations, the abundance and
distribution of sedimentary beds on the continental shelf can be estimated.
The data interpretation from high resolution shallow seismic profiles
was taken in cruises VG-05 within the framework of the Project in 2004 [2].
III. RESULTS
On the basis of the data interpretation from high resolution shallow
seismic profiles, some volcanos/diapirs (basalts, mouths) have been found in
the bottom of the South Central Việt
In the bottom of the Vũng Tàu - Bình Thuận continental shelf:
- Seismic line 3: Volcano on
profile 10050403 (about 108o.7891 E and 10o.5960 N),
having size of about 800 and 2.400 m (in NE vicinity of Hòn Tro volcano island,
Fig. 1).
- Seismic line 1: Volcano on
profile 09050403 (about 108o.8699 E and 10o.2528 N)
having size of about 700 m (Fig. 2).
- Seismic line 6+7a: Volcano on
profile 14050407-14050420 (Fig. 2) having size of about 150 m, 400 m and 10,000
m.
- Seismic line 7b: Volcano on profile
15050401-15050411 (Fig. 2) having size of about 50,000 m).
Figure 1. Seismic
line 1, volcano on profile 09050403 in the bottom
of the Vũng Tàu - Bình Thuận continental shelf.
Figure 2. a) Seismic line 3, volcano on profile
10050403;
b) Seismic line 6+7a, volcano on profile 14050407-14050420;
c) Seismic line 7b, volcano on profile 15050401-15050411
in the bottom of the Vũng
Tàu - Bình Thuận continental shelf.
Fig.3. Seismic line 14, volcano on profile 28050415 in the bottom
of the Nha Trang continental shelf.
In
the bottom of the Nha Trang continental shelf:
- Seismic line 14: Volcano on profile 28050415 (about 109o.3566
E and 12o.3568 N) with the size of about 320 m (Fig. 3).
IV. DISCUSSION
Presented
characteristics of the volcanoes show that the volcanic activities in the
studied region began and developed along regional rifts in the activated period
of late Cenozoic magma in the East Sea [3] and maybe the determine ages into
four volcanic period: Late Miocene, Pliocene, Middle Pleistocene and actual, in
themselves - into two groups: hawaian and tholeiitic [1] .
REFERENCES
1. Đỗ Minh Tiệp, 1996. Time and space differentiation
of Cenozoic submarine basalts on the bottom of the
2. Nguyễn Tiến Hải et al, 2006. Holocene coastal evolution, sea-level fluctuations, terrigenous
sedimentation and sediment dynamics on the continental shelf between the Mekong
Delta and Nha Trang, SE Việt Nam. Coop. Proj. between
IMGG (Việt Nam) and CAU (Germany) in 2003-2005.
3. Nguyễn Xuân Hãn et al, 1996. Features of late Cenozoic
volcanic activities in the East Sea of Việt Nam. Contr. of Marine geol. and
geoph., II : 88-95. Sci. & Techn. Publ. House, Hà Nội.
4. Schimanski A., K. Stattegger, 2004. Deglacial and Holocene
evolution of the Vietnamese continental shelf: Stratigraphy, sediments and
sea-level change. Marine Geology, pp. 1-24.
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Conf. on Deltas (Mekong Venue): Geol. Modelling and Manag., HồChíMinh City.