Quaternary Science Reviews 21 (2002) 1807–1819
Holocene delta evolution and sediment discharge of the Mekong
River, southern Vietnam
Thi Kim Oanh Taa,*, Van Lap Nguyena, Masaaki Tateishib, Iwao Kobayashib,
Susumu Tanabeb, Yoshiki Saitoc
a
Sub-Institute of Geography, Vietnam National Center for Natural Science and Technology, 1 Mac Dinh Chi Street, 1 Dist.,
Ho Chi Minh City, Viet Nam
b
Department of Geology, Faculty of Science, Niigata University, Niigata 905-2181, Japan
c
MRE, Geological Survey of Japan, AIST, Central 7, Higashi 1-1-1, Tsukuba, Ibaraki 305-8567, Japan
Received 18 August 2001; accepted 14 January 2002
Abstract
Evolutionary changes, delta progradation, and sediment discharge of the Mekong River Delta, southern Vietnam, during the late
Holocene are presented based on detailed analyses of samples from six boreholes on the lower delta plain. Sedimentological and
chronostratigraphic analyses indicate clearly that the last 3 kyr were characterized by delta progradation under increasing wave
influence, southeastward sediment dispersal, decreasing progradation rates, beach-ridge formation, and steepening of the face of the
delta front.
Estimated sediment discharge of the Mekong River for the last 3 kyr, based on sediment-volume analysis, was 144736
million t yr1 on average, or almost the same as the present level. The constant rate of delta front migration and stable sediment
discharge during the last 3 kyr indicate that a dramatic increase in sediment discharge owing to human activities, as has been
suggested for the Yellow River watershed, did not occur. Although Southeast Asian rivers have been considered candidates for such
dramatic increases in discharge during the last 2 kyr, the Mekong River example, although it is a typical, large river of this region,
does not support this hypothesis. Therefore, estimates of the millennial-scale global pristine sediment flux to the oceans must be
revised. r 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction
The Mekong River, one of the largest rivers in
Southeast Asia, flows southward from the Tibetan
Plateau to the South China Sea through the Indochina
Peninsula and forms a delta at its mouth. This wide
delta plain is one of the largest deltas in the world
(Coleman and Roberts, 1989). For the last 6 ka, the
delta has prograded more than 200 km around the
Cambodian border to the present coastline in southern
Vietnam. At present, the Mekong River delta is
classified as a wave-influenced tide-dominated delta
according to the diagram of Galloway (1975).
Stable to slightly falling sea levels for the last 6 kyr, in
combination with high sediment discharge from large
*Corresponding author. Tel.: +84-8-822-0829; fax. +84-8-8224895.
E-mail addresses: [email protected] (T.K.O. Ta),
[email protected] (Y. Saito).
rivers originating in and flowing through high mountains and a monsoonal climate, have resulted in the
formation of immense deltas in Asia (Saito, 2001), such
as those of the Changjiang (Yangtze River), the
Ayeyarwady (Irrawaddy), the Song Hong (Red River),
the Chaophraya River, and the Huanghe (Yellow River)
(Nguyen et al., 2000; Woodroffe, 2000; Saito et al.,
2000a ,b, 2001; Hori et al., 2001), the Ganges–Brahmaputra (Goodbred and Kuehl, 2000). Asian rivers
contribute about 30–40% of the world’s delivery of
sediment from rivers (Milliman and Syvitski, 1992).
Present sediment discharge from rivers to the oceans
of the world is estimated to be 20 109 t annually
(Milliman and Syvitski, 1992). However, the naturalstate sediment discharge is thought to have been about
one-third this level (Milliman and Syvitski, 1992;
GESAMP, 1993; Hu et al., 1998). The increase that
has occurred during the last 2000 years is considered to
result from human activities, especially cultivation and
deforestation in Asia. One of the best examples of
0277-3791/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved.
PII: S 0 2 7 7 - 3 7 9 1 ( 0 2 ) 0 0 0 0 7 - 0
1808
T.K.O. Ta et al. / Quaternary Science Reviews 21 (2002) 1807–1819
human impact on a river is the Huanghe. The naturalstate sediment discharge of the Huanghe before 2 ka is
estimated to have been one-third to one-tenth the
present level (Milliman et al., 1987; Ren and Zhu,
1994; Saito et al., 2001). The present large discharge is
thought to be the result of both human cultivation of the
Loess Plateau (Milliman et al., 1987; Ren and Zhu,
1994; Saito et al., 2001) and a change in the depocenter
of the riverine sediments from the fluvial plain to the
coast (Ren and Zhu, 1994; Saito et al., 2001). The
Changjiang has shown a similar increase in sediment
discharge during the last 2 ka as a result of a depocenter
change from the middle reaches of the river to the lower
reaches and deltaic region (Hori et al., 2001, 2002).
However, the increase in sediment discharge of these
two rivers alone cannot explain the large increase in
total global sediment discharge suggested by Milliman
and Syvitski (1992). One of the key areas to look for an
explanation of this increase is Southeast Asia, and the
Mekong River is a typical example of a large river of
that region.
We describe the late Holocene evolution of the
Mekong Delta and estimate millennial-scale sediment
discharge on the basis of volume analysis of the late
Holocene deltaic strata. The paleo-offshore break from
subtidal flat to delta front was reconstructed on the basis
of detailed sediment facies analyses and 39 accelerator
mass spectrometry (AMS) 14C dates from six cores
taken in the outer part of the Mekong River Delta. The
offshore break is the coarsest sediment facies in a deltaic
succession (Hori et al., 2002; Ta et al., 2002) and is easily
identified in cores. Six cores with lengths of 20–70 m
each, were taken in 1997–1999. These cores have been
partly described by Ta et al. (2001, 2002) and Tanabe
et al. (2001). In this paper, we outline the sediment
facies, including previously unreported core descriptions
and radiocarbon ages, and discuss late Holocene
paleogeography and sediment discharge.
2. General setting
2.1. Physiography and geology
The Mekong Delta, one of the largest deltas in
Southeast Asia, is located at the mouth of the Mekong
River. The river has its headwaters in the Tibetan
mountains, and it flows down the Indochina Peninsula
through several countriesFChina, Laos, Myanmar,
Thailand, and CambodiaFbefore emptying into the
South China Sea in southern Vietnam (Fig. 1). The river
is 4620 (4350–4880) km long (Hori, 1996; National
Astronomical Observatory, 1999), and it drains an area
of 790–810 103 km2 (Milliman and Syvitski, 1992;
Hori, 1996; National Astronomical Observatory,
1999). Its water discharge is 470 km3 yr1, and its
sediment discharge is 160 million t yr1 (Milliman and
Ren, 1995), or tenth and ninth largest in the world,
respectively.
The Mekong Delta is defined as the roughly
triangular area between Phnom Penh, Cambodia, the
Saigon River mouth near Ho Chi Minh City, and Ca
Mau Cape on the south of Camau Peninsula (Gagliano
and McIntire, 1968) (Fig. 1). The area of the delta is
between 62,520 and 93,781 km2 (Orton and Reading,
1993; Nguyen et al. 2000). The delta is bounded on the
northeast by Pleistocene-age uplands, swamps, and the
Saigon River system (Fig. 1).
The modern Mekong Delta system has two major
distributary channels known as the Bassac and Mekong
rivers (Fig. 1). The Mekong River in turn subdivides
into three major distributary channels. The positions of
these distributary channels are estimated to have been
relatively stable over the last 2–3 ka from the distribution of the beach ridges, which indicate interdistributary
plains.
The detailed topography of the subaerial delta plain
suggests that it is composed of two parts: an upper
(inner) delta plain dominated by fluvial processes, and a
lower (outer) delta plain characterized by a welldeveloped beach-ridge system and mainly influenced
by marine processes (Gagliano and McIntire, 1968;
Nguyen et al., 2000). The rows of beach ridges on the
lower delta plain trend northeast to southwest and are
3–10 m high; they are separated by inter-ridge swamps.
The beach ridges often have a diverging, bifurcating
pattern formed by southwestward spit progradation
(Nguyen et al., 2000). The modern, active subaerial delta
environment is composed mainly of mangroves, beach
ridges (including the foreshore), and tidal flats.
The huge delta plain stretching from Cambodia to the
Vietnamese coast was formed during a short period of
only 6–7 ka, mostly after the mid-Holocene sea-level
highstand, which was recorded at 2.5 or 4.5 m above the
present sea level at about 5–7 ka (Nguyen et al., 2000).
The shoreline at that time (at nearly the maximum
extent of transgression) was located in Cambodia. Since
then, the delta has prograded more than 200 km
southeastward (Nguyen et al., 2000).
Delta progradation over the last 6–7 ka was not
constant. The topography and sediment facies show that
the upper delta plain formed in a tide-influenced
environment before 3 ka, and the lower delta plain
formed in a more wave-influenced environment during
the last 3 ka (Tanabe et al., 2001; Ta et al., 2002).
2.2. Coastal hydrodynamics and morphology
The coastal environment of the Mekong River Delta
is classified as a mixed-energy (tide-dominated) environment, according to Hayes (1979) and Davis and Hayes
(1984). The mean tidal range is 2.570.1 m (Gagliano
T.K.O. Ta et al. / Quaternary Science Reviews 21 (2002) 1807–1819
1809
Fig. 1. Locations of the six cores and map of the Mekong River Delta. Simplified after Nguyen et al. (2000). Open circles: borehole sites. Bathymetric map is based on Topographic Map of Seabed,
1:1,000,000 (1983).
T.K.O. Ta et al. / Quaternary Science Reviews 21 (2002) 1807–1819
1810
and McIntire, 1968; Coleman, 1981; Wolanski et al.
1996; Nguyen et al. 2000), and the maximum tidal range
is 3.2–3.8 m (Wolanski et al. 1996; Nguyen et al. 2000).
The mean wave height is 0.9 m (T. D. Thanh, personal
communication). Southwestward coastal and longshore
currents generated by winter monsoons are dominant
(Gagliano and McIntire, 1968), and are mainly responsible for the formation of the beach ridge and spit
system.
The subaqueous topography of the Mekong River
Delta is composed of two parts: subtidal flats and
the delta front. The subtidal flats extend to a depth
of 6 m and are 5–20 km wide (Figs. 1 and 4). Based on
the bathymetry, the delta front gradient off the Bassac
River is 0.3–0.4%, which is the steepest among the
present delta front areas. Also steep is the southwestward front off Ca Mau Cape, where the gradient
is 0.6–0.7%. This steep face is estimated to be the
slip face of the southwestward prograding spit that
formed Ca Mau Cape. At present, sediment transport
is dominantly southwestward by monsoonal longshore
currents. Gagliano and McIntire (1968) also showed
bedforms on the subtidal flat. The toe of the delta
front is clear from the bathymetry. The offshore
topography indicates a series of depressions normal
to the shore; these have a thin Holocene cover and are
estimated to have formed during the sea-level lowstand.
Most river-derived sediments are trapped within the
deltaic system, including around Ca Mau Cape.
undertaken on plant fragments and molluscan shells
by AMS at the Center for Chronological Research,
Nagoya University, Japan and at Beta Analytic, Inc.
Calendar ages were calculated by using the INCAL98
calibration curve (Stuiver et al., 1998). Results of the
analyses of the BT1, BT2, and BT3 cores are reported by
Ta et al. (2001, 2002), and the VL1 and TV1 cores are
discussed by Tanabe et al. (2001). We outline their
results and compile previously unreported core data
(Table 2).
4. Depositional facies and stratigraphic correlations
The Late Pleistocene–Holocene stratigraphy of the
Mekong River Delta was studied mainly on the basis of
samples from the six cores. The stratigraphic sections
are shown in Fig. 2. Late Pleistocene–Holocene strata
are grouped into (1) Late Pleistocene undifferentiated
sediments, (2) transgressive incised-valley fill sediments,
and (3) Holocene delta sediments.
4.1. Late Pleistocene undifferentiated sediments
The Late Pleistocene sediments were recovered at
about 13 to 35 m below present sea level in the lowest
parts of the BT1, BT3, VL1, TC1, and TV1 sites and
consist of stiff, slightly oxidized, yellowish gray silty
sand and fine–medium sand bearing scattered quartz
pebbles. Lenticular bedding and parallel lamination are
common. These sediments were dated to 43,420+980
(BETA-132936) and >50,400 (BETA-142430) conventional 14C BP at the TC1 and TV1 sites, respectively.
They were unconformably overlain by Holocene marine
sediments.
3. Materials and methods
Six continuous cores 25 km apart on average and
totaling 250 m in length were drilled in the lower
plain of the Mekong River Delta during 1997–1999
(Fig. 1; Table 1; BT1, BT2, BT3, VL1, TC1, TV1).
The cores were split, described, and photographed.
Radiographs of slab samples were taken throughout
all split cores. Sand and mud (silt and clay)
contents were measured every 20 cm throughout the
core using 5 cm thick sand and 2 cm thick silt and clay
samples. Fossils and microfossils such as diatoms,
foraminifers, and mollusca species were identified. Forty
samples were collected for 14C dating; analyses were
4.2. Transgressive incised-valley fill sediments
The most recently deposited transgressive succession
has been investigated in more detail at the BT2 site (Ta
et al., 2001). Only this core penetrated the incised valley
formed during the Last Glacial. The other sites are
thought to be in interfluvial zones. After the Last
Glacial Maximum (LGM), the sea level rose rapidly,
and accommodation space was probably created pre-
Table 1
List of core locations taken from the Mekong River Delta
Cores
Latitude
Longitude
Altitude (m)
Drilling depth (m)
Drilling period
BT1
BT2
BT3
VL1
TV1
TC1
101170 0100
101080 1800
101010 0500
101010 4600
91510 0400
91410 0400
1061210 3400
1061280 0700
1061370 4400
1051580 4200
1061110 3700
1061260 4800
+3
+2
+2
+2
+0.8
+2
40
71
29
42
27
36
Dec.
Dec.
Dec.
Dec.
Dec.
Dec.
1997
1997
1997
1998
1998
1999
T.K.O. Ta et al. / Quaternary Science Reviews 21 (2002) 1807–1819
1811
Table 2
List of 14C ages from the cores taken from the Mekong River Delta
Cores Altitude (m) Materials
BT2
BT3
VL1
TV1
TC1
10.2
15.4
32.54
35.1
35.15
52.38
60.87
2.94
4.97
6.52
7.52
10.09
10.46
18.0
19.45
0.45
7.94
9.96
13.8
18.61
33.66
1.82
3.76
5.72
7.85
9.58
11.64
15.76
20.63
24.99
3.21
3.6
6.6
7.63
10.2
14.34
16.56
18.52
18.84
Shell
Plant material
Shell
Shell
Shell
Shell
Plant material
Shell
Shell
Shell
Shell
Shell
Wood
Shell
Shell
Plant material
Plant material
Plant material
Plant material
Plant material
Shell
Shell
Shell
Shell
Shell
Shell
Shell
Shell
Shell
Shell
Plant material
Shell
Shell
Shell
Shell
Shell
Shell
Shell
Shell
d13C
Conventional Calibrated age (cal BP)
(per million) 14C age (BP)
Intercept
1.4
27.4
0.44
0.46
1.8
2.8
26.6
4.14
1.75
1.32
2.34
1.81
28.1
0.27
0.97
29.1
29.4
32.6
27.6
28.3
0.3
0.8
1.4
0.6
0.3
0.3
0.6
0.3
0.8
0.8
27.4
4.2
1.1
0.9
1.4
0.1
1.8
0.8
0.8
3660780
4590790
5210790
5320780
4970740
7590760
113407115
1300790
1730760
2130770
1990780
1620790
3120760
4170790
4030770
3210750
3390740
3340740
3480750
4210730
5700740
1190740
1190740
1470740
1870740
2000740
2230740
2350740
2930740
434207980
4510750
3120760
3620760
3980750
4250750
4590750
4520770
4840750
>50400
Sample code Reference
no.
Range
3562
3660–3459
NUTA-6529 Ta et al. (2001)
5309
5451–5055
NUTA-6551 Ta et al. (2001)
5578
5646–5474
NUTA-6530 Ta et al. (2001)
5658
5747–5590
NUTA-6540 Ta et al. (2001)
5300
5321–5278
Beta-149701 Ta et al. (2001)
8021
8110–7962
Beta-149702 Ta et al. (2001)
13314/13258/13194
13,456–13,152 NUTA-6552 Ta et al. (2001)
868
928–735
NUTA-6543 Ta et al. (2002)
1278
1319–1237
NUTA-6534 Ta et al. (2002)
1706
1806–1616
NUTA-6545 Ta et al. (2002)
1535
1629–1459
NUTA-6542 Ta et al. (2002)
1177
1266–1067
NUTA-6536 Ta et al. (2002)
3356
3385–3267
NUTA-6546 Ta et al. (2002)
4237
4383–4105
NUTA-6537 Ta et al. (2002)
4059
4141–3950
NUTA-6539 Ta et al. (2002)
3442/3425/3407
3470–3377
Beta-132922 Tanabe et al. (2001)
3636
3688–3574
Beta-132923 Tanabe et al. (2001)
3626/3622/3571
3634–3477
Beta-132924 Tanabe et al. (2001)
3808/3794/3720
3830–3644
Beta-132925 Tanabe et al. (2001)
4826
4831–4658
Beta-132926 Tanabe et al. (2001)
6111
6168–6038
Beta-132927 Tanabe et al. (2001)
721
760–678
Beta-132928 Tanabe et al. (2001)
721
760–678
Beta-132929 Tanabe et al. (2001)
1001
1054–958
Beta-132930 Tanabe et al. (2001)
1403
1465–1354
Beta-132931 Tanabe et al. (2001)
1545
1601–1514
Beta-132932 Tanabe et al. (2001)
1826
1873–1793
Beta-132933 Tanabe et al. (2001)
1962
2002–1915
Beta-132934 Tanabe et al. (2001)
2719
2740–2699
Beta-132935 Tanabe et al. (2001)
F
F
Beta-132936 Tanabe et al. (2001)
5280/5163/5135/5105/5072 5301–5046
Beta-142422 This study
2876
2957–2810
Beta-142423 This study
3505
3586–3442
Beta-142424 This study
3969
4061–3895
Beta-142425 This study
4368
4411–4281
Beta-142426 This study
4814
4838–4787
Beta-142427 This study
4774/4743/4736
4815–4606
Beta-142428 This study
5131
5252–5034
Beta-142429 This study
F
F
Beta-142430 This study
NUTA-: 14C dating in Nagoya University.
Beta-: 14C dating in Beta Analytic Inc.
ferentially in incised valleys, which were effectively filled.
The sedimentary succession of the incised-valley is
composed of estuarine channel/tidal river sandy silt,
muddy tidal flat/salt marsh, estuarine marine sand,
transitional sandy silt, and finally open bay mud facies
in ascending order.
The estuarine channel/tidal river sandy silt facies
consists of slightly oxidized gray silty sand and fine–
medium sand bearing scattered quartz pebbles in the
lower part. Lenticular bedding and parallel lamination
are common. There is an intermixture of marine
plankton, marine–brackish-water, and freshwater diatom species, indicating the influence of tidal currents
and/or wave activity. Foraminifer species are few,
indicating a brackish water habitat.
The muddy tidal flat/salt marsh facies is characterized
by interbedded, stiff, brownish gray silty clay. Faint
lamination is found in the lower part and discontinuous
parallel lamination in the upper part. Plant fragments
and calcareous concretions are common. The presence
of several diatom and foraminifer species indicates a
marine–brackish-water habitat. The sediments were
dated to 13,258 cal BP (NUTA-6552).
The estuarine marine sand and sandy silt facies is
composed of 18.5 m of sand and sandy silt. The lower
part of this facies consists of intercalated yellowish gray
coarse sand, silty sand, quartz pebbles, lenticular bedding, cross-lamination (current ripples), and small-scale
cross-bedding, and dates to 8021 cal BP (BETA-149702).
The middle part displays a fining-upward succession
1812
T.K.O. Ta et al. / Quaternary Science Reviews 21 (2002) 1807–1819
Fig. 2. Cross-sections XY and AB and inferred depositional facies with time lines. Section XY is modified after Ta et al. (2002).
T.K.O. Ta et al. / Quaternary Science Reviews 21 (2002) 1807–1819
consisting of brownish gray sandy silt with parallel
lamination and wavy bedding. The upper part is a
coarsening-upward succession consisting of intercalated
dark gray sandy silt and fine sand with parallel
lamination, cross-lamination, wavy bedding, and
small-scale cross-bedding. There is an intermixture of
marine, brackish-water, and freshwater diatom species.
Abundant small-sized foraminifers indicate a coastal
shallow-water environment with varying salinity. The
sedimentary environments are interpreted to have
changed from tidal channels in the lower part to
subtidal to intertidal flats (central basin) in the middle
part, and then to an estuarine-mouth sand body (flood
tidal delta) in a drowned valley as sea level rose during
the last transgression (Dalrymple et al., 1992).
The transitional sandy silt facies consists of intercalated dark gray silt and sandy silt with wavy bedding
and parallel lamination. Shell fragments and bioturbation are common. Marine plankton diatom species
significantly increase. Foraminifers are similar to those
found in the underlying estuarine sediments, but
plankton species become common and indicate a
shallow marine habitat. This facies is interpreted as
the transition from the underlying estuary environment
to the open bay environment of the overlying facies. The
sediments were dated to 5300 cal BP (BETA-149701)
and 5658 cal BP (NUTA-6540).
The open bay mud facies, 10–13 m thick at the BT2 and
VL1 sites, mainly consists of homogeneous greenish gray
mud at the BT2 site and discontinuous-parallel to parallel
laminated mud at the VL1 site. This facies shows a finingupward succession, and the mud content is more than
90%, the highest of all the facies. Shell fragments and
incipient nodules are scattered throughout the facies. The
proportion of marine plankton diatom species increases
upward, and reaches more than 65–70%; the high
abundance of Coscinodiscus radiatus, C. nodulifer, Thalassiosira excentrica, and Thalassionema nitzschioides
indicates an open bay or outer bay environment (Nguyen
and Kobayashi, 1996, 1997; Nguyen et al., 1998, 1999; Ta
and Nguyen, 2000; Ta et al., 2001). The number of
foraminifer species characteristic of an open marine
environment increases upward markedly. Marine and
shallow marine molluscs are also found. The sediments
were dated to 5578 cal BP (NUTA-6530).
4.3. Holocene deltaic sediments
Holocene deltaic sediments consist of prodelta mud
facies, delta front sandy silt facies, sub- to intertidal flat
sandy silt facies and subaerial delta plain facies in
ascending order.
4.3.1. Prodelta mud facies
This facies shows a coarsening-upward succession and
consists of dark gray silt to very fine sand. It is found at
1813
all sites and is 4–7 m thick, except at the VL1 site, where
it is 12.5 m thick. At the BT3 and TV1 sites, the grain is
coarser than at the other sites. Interbedded greenish
gray silt (25–30 mm thick) and silty clay (2–3 mm thick)
layers are found in the lower part of this facies, and
discontinuous and parallel lamination containing very
fine sand layers in the upper part. Shell fragments and
calcareous concretions are common. Marine plankton
diatom species are abundant, and brackish-water species
increase measurably. The marine species Coscinodiscus
radiatus and C. nodulifer and the brackish-water
species Cyclotella caspia and C. styrolum are common.
This indicates a shallow marine habitat frequently
supplemented by fresh- and brackish-water sources.
Moreover, the high abundance of marine plankton
species such as Coscinodiscus radiatus, C. nodulifer,
and Thalassiosira excentrica at the TV1 site indicates
that the site was more strongly influenced by marine
processes than the other sites. Foraminifer species
are similar to those in the underlying open bay mud
facies, but the numbers of each species decrease
markedly. The shallow marine mollusca Natica sp.,
Cryptopecten sp., and Olivellai sp. are also found. This
facies is interpreted as prodelta sediments (Coleman and
Wright, 1975; Coleman, 1981) and was dated to
4826 cal BP (BETA-132926) and 3794 cal BP (BETA132925) (VL1 site); 4743 cal BP (BETA-142428) and
4814 cal BP (BETA-142427) (TC1 site), 1962 cal BP
(BETA-132934) (TV1 site); and 4059 cal BP (NUTA6539) (BT3 site).
4.3.2. Delta front sandy silt facies
This facies, a 6–9 m-thick coarsening-upward succession, consists of intercalated greenish gray sandy silt and
fine sand. Cross-lamination, lenticular bedding, and
wavy bedding are common at the BT2, BT3, and TV1
sites, while discontinuous parallel lamination, parallel
lamination, and current ripples are common at the other
sites. Small shell fragments and mica flakes are scattered
throughout the facies. Marine plankton diatom species
are still abundant and brackish-water species are
common, but freshwater species increase obviously.
Coscinodiscus radiatus, C. nodulifer, Cyclotella styrolum,
and Aulacoseira granulata are common. In particular,
Cyclotella caspia and C. styrolum are abundant in the
lowest part of this facies. Shallow-marine foraminifer
species such as Ammonia spp., Bolivina spp., Asterorotalia sp., and Gallitella vivans are common. Brizalina
spp., Bulimina sp., Hopkinsina pacifica, and Pararotalia
spp., Pseudogyroidina spp., and Quinqueloculina spp.
occur with low frequency. The presence of Ammonia
tepida and Triloculina sp. may reflect the increasing
influence of freshwater. This is consistent with the
increase in freshwater diatoms, which is influenced by
fluvial discharge. Shallow marine mollusca such as
Conus sp. and Mitrella sp. are found. The facies suggests
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T.K.O. Ta et al. / Quaternary Science Reviews 21 (2002) 1807–1819
delta front sediments (Coleman and Wright, 1975) and
was dated to 5309 cal BP (NUTA-6551) and 3562 cal BP
(NUTA-6529).
4.3.3. Sub- to intertidal flat sandy silt facies
This facies, 6–8 m thick, consists of laminated dark
gray sandy silt and fine sand. It is characterized by wave
ripples, lenticular bedding, parallel lamination, and
discontinuous lamination. Shell fragments and mica
flakes are common. Marine plankton diatom species are
obviously less abundant in comparison with the underlying delta front deposits, but brackish-water diatom
species are very abundant. Coscinodiscus radiatus, C.
nodulifer, Cyclotella caspia, and C. styrolum, indicating a
marine–brackish-water habitat, are common. Shallowmarine foraminifer species decrease upward (Ta et al.,
2001). Ammonia sp. is common; Asterorotalia spp.,
Bolivina spp., Gallitella vivans, Brizalina spp., Bulimina
sp., and Hopkinsina pacifica occur with low frequency.
This sedimentary facies differs somewhat between the
two sites BT1 and VL1 and the other four sites, BT2,
BT3, TC1, and TV1, with respect to grain size and
sedimentary structures. The grain size of the sediments
of BT2, BT3, TC1, and TV1 is coarser than that of the
BT1 and VL1 sediments. The sediments at the BT1 and
VL1 sites display a fining-upward succession with
parallel lamination and lenticular bedding, and
an overlying subaerial delta plain facies. The sediments
at the BT2, BT3, TC1 and TV1 sites also show a finingupward succession; however, they display a wide
variation in sedimentary structures, including
wavy bedding, flaser bedding, and cross-lamination,
in addition to parallel lamination and lenticular
bedding, and they are covered by coarse sediments of
the subaerial delta plain facies. These features of
this facies are tide-influenced, and it is interpreted
as a subtidal to intertidal flat facies (Reineck and
Singh, 1980; Li et al., 2000b; Hori et al., 2001, 2002).
However, the facies at the BT2, BT3, TC1, and TV1
sites were influenced not only by tides but also in part by
waves.
4.3.4. Subaerial delta plain facies (marsh and beach
ridge)
This facies is 4–5 m thick and has two parts. The
sediments of BT1 and VL1 consist of dark silt and sandy
silt with rich organic matter, rootlets, and mica flakes.
They are characterized by discontinuous parallel lamination and lenticular bedding. Brackish- and freshwater
diatom species such as Cyclotella caspia, C. styrolum,
Synedra spp., and Stephanodiscus astrea obviously
increase, while marine plankton species decrease. Foraminifers are not found in these sediments. The
sediments at the BT2, BT3, TC1, and TV1 sites consist
of well-sorted fine yellowish brown and gray sand, with
some rootlets and scattered shell fragments at the BT3
site. Fresh/brackish-water diatom species are common.
This facies probably represents an intertidal to supratidal flat/salt marshy deposit at the BT1 and VL1 sites.
The sediment facies at the BT2, BT3, TC1, and TV1
sites is interpreted as sand dune/foreshore sand forming
beach ridges.
5. Discussion
5.1. Sea-level changes and the incised valley
Two cross-sections perpendicular to the present
coastline in Ben Tre and Tra Vinh provinces in the
northeastern part of the Mekong River Delta are
illustrated in Fig. 2. Because the maximum transgression
occurred here at 6–7 ka, most of the incised-valley fill
found at the BT2 site was deposited during the last
transgression. Although the location of the paleoMekong River during the LGM has yet to be mapped,
the BT2 core must penetrate the valley, and the paleoriver would have flowed eastward. The incised valley
was filled by estuarine sediments during the rise of sea
level after the LGM. When the sea first inundated the
BT2 site, an estuarine channel/tidal river sandy silt
facies was formed. As sea level rose, the river mouth
shifted gradually landward, and the marine influence
was enhanced. When sea level was probably around
60 m, the tidal flat sediments dated to 13,258 cal BP
were deposited. An 18.5-m-thick estuarine marine sandy
facies characterized by tidal lamination and abundant
small-sized foraminifers (Wang and Murray, 1983) was
then deposited under conditions of a rising base level (Li
et al., 2000a). All of the other sites are located on
interfluves, for example, terrace-like uplands. An erosional surface with lateritization presents at different
elevations ranging from 10 to 35 m and is regarded
as both a sequence boundary and a transgressive
ravinement surface.
There is not yet any Late Quaternary sea-level curve
for the study area. Estimation of the LGM sea level is
about 120 m in Southeast Asia at around 18,000–
20,000 14C yr BP (**Woodroffe, 1993; Hanebuth et al.
2000). Most of the Sunda Shelf area was subaerially
exposed and formed shelf-wide regressive incisions.
Since the last Glacial episode, sea level has risen rapidly
and reached to 60 m at about 13,258 cal BP at the
Mekong River Delta as indicated by this study. The sealevel curve for the last 15 ka of the Mekong River Delta
could be illustrated in Fig. 3 (Hanebuth et al., 2000;
Nguyen et al., 2000).
5.2. Delta progradation
Away from the incised valley, a progradational deltaic
succession with a thickness of about 25 m (10–35 m) has
T.K.O. Ta et al. / Quaternary Science Reviews 21 (2002) 1807–1819
1815
Fig. 3. Age–depth (accumulation) curves at the core sites from the Mekong River Delta. Compiled with data from Ta et al. (2001) and Tanabe et al.
(2001). Wide curves using light tones with core names indicate accumulation curves on the right part. Open and closed marks indicate radiocarbon
ages from shell and plant fragment materials, respectively. Two thinner curves at the middle part showing sea-level curves: (A) sea-level curve for the
last 15 kyr of the Mekong River Delta; (B) sea-level curve for the last 20 kyr of the Sunda Shelf by Hanebuth et al. (2000) enlarged from the inserted
figure.
developed over the last 6 kyr, especially during the last
3–4 kyr, in this study area. During the sea-level highstand and subsequent periods of slightly falling sea level,
the subaerial and subaqueous delta morphology changed rapidly in response to the large sediment load from
the river. A coarsening-upward succession of prodelta,
delta front, and subaqueous delta plain facies suggests
that the delta sediments formed after the occurrence of
the maximum flooding surface in all cores. There are
some differences in sediment facies and succession
between the inland delta plain and the beach-ridge delta
plain (Fig. 2). Ta et al. (2002) suggested that there are
two types of deltaic succession in the Mekong River
Delta. In the inland delta plain, a coarsening-upward
delta front facies overlain by a fining-upward sub- to
intertidal facies suggests a typical tide-dominated delta
succession (Hori et al., 2001, 2002) or a fining-upward
tidal flat succession (Reineck and Singh, 1980). However, in the outer delta plain with its beach-ridge system,
the upper part consists of a coarsening-upward succession, including in its uppermost part foreshore/dune
sediments. This indicates a wave- and tide-dominated
delta succession. This facies succession change coincides
with the surficial morphology of the present delta plain.
Several beach-ridge systems were formed at higher
elevation seaward.
Related to the above changes, progradation rates of
the deltaic system also changed. The rate decreased from
17–18 m yr1 in the inner delta to 8–15 m yr1 in the
outer delta along the Ben Tre transect (XY section in
Fig. 2; Ta et al., 2002). In particular, progradation rates
differed at different water depths. Estimated progradation rates are 8.5 m yr1 at 20 m altitude between BT3
and the present subaqueous topography, 10.5 and
10.1 m yr1 at 15 m altitude between sites BT2 and
BT3 and between the BT3 site and the present
topography, respectively, and 12.4 and 14.4 m yr1 at
10 m altitude between sites BT2 and BT3 and between
the BT3 site and the present topography, respectively
(Fig 2; Ta et al., 2002). These data indicate that the
progradation rate was high in the shallower part of the
delta, resulting in the change to a steeper delta front
topography with delta progradation during the last
5 kyr. This topographic change can be linked to the
changes in sediment facies and progradation rate, and to
increased wave influence.
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T.K.O. Ta et al. / Quaternary Science Reviews 21 (2002) 1807–1819
Similar phenomena are recognized along the Tra Vinh
transect (AB section in Fig. 2). According to new data of
this study, progradation rates are estimated to be 12.1–
14.4 m yr1 at 15 m altitude, 11.7–15.6 m yr1 at 10 m
altitude, and 13.9–25.2 m yr1 at 5 m altitude between
TC1 and the present subaqueous topography. Delta
progradation rates decreased rapidly after 3 ka from 30–
40 to 10–20 m yr1 with the development of a beachridge system (Tanabe et al., 2001).
This decrease may be related to the increase in wave
influence resulting in sediment dispersal southwestward
(Tanabe et al., 2001; Ta et al., 2002). Most waves are
related to the monsoon climate and approach the
Mekong River Delta region from the northeast. The
headland east of Ho Chi Minh City sheltered the river
mouth from these waves before 3 ka. However, as the
delta prograded seaward and projected past the headland during the last 3 kyr, the environment became more
wave influenced, and the sediment facies and topography began to resemble those of the present delta.
5.3. Sediment accumulation curves (Fig. 3)
Accumulation curves at the core sites show the
relationship between the accumulation rate and the
sediment facies. The accumulation rate at the core sites
has changed together with the changes in sediment facies
and sea level (Fig. 3). The paleo-Mekong River incised
valley was rapidly buried at the BT2 site during the
transgression because of the high sediment discharge
from the river and the confined depositional area. The
accumulation rate of the estuarine sediments was
7.3 mm yr1 from around 8 to 5.6 ka, and from about
5.6 to 5.3 ka, bay and prodelta sediments accumulated at
the extremely high rate of 32.0–63.7 mm yr1. After
5.3 ka, the accumulation rates decreased markedly at the
BT2 and BT3 sites; approximate rates were 4.5 mm yr1
in the prodelta, 2.9–3.6 mm yr1 in the delta front, and
4.2 mm yr1 in the subaqueous delta plain. At the VL1
site, accumulation rates were high at 11.7–13.4 mm yr1
in the embayment and lower prodelta from 6 to 4.8 ka,
7.0 mm yr1 in the upper prodelta, and 38.6 mm yr1 in
the delta front from 3.8 to 3.6 ka. Between 5 and 4.8 ka,
prodelta sediments at the TC1 site accumulated at a rate
comparable to that of the prodelta sediments at the VL1
site. After 4.8 ka, most accumulation rates of the
prodelta, delta front, and subaqueous sediments at the
TC1 and TV1 sites decreased considerably in comparison to those of the corresponding sediments at the VL1
site. Approximate rates were 7.7–13.1 mm yr1 in the
prodelta, 7.9–14.1 mm yr1 in the delta front, and 4.7–
7.1 mm yr1 in the subaqueous delta plain at the TC1
and TV1 sites.
Accumulation curves from age–depth plots at each
borehole site are shown in Fig. 3. The high accumulation rates (steep gradients) at both the VL1 and BT2
sites from 5 to 6 ka indicate that the incised valley and
shelf depression of the paleo-Mekong River were rapidly
buried during the transgression and sea-level highstand
because of the high sediment discharge and confined
depositional area.
5.4. Millennial-scale sediment discharge
The offshore break between the subaqueous delta
plain and the delta front coincides with the coarsest
sediment facies between the subaqueous delta plain
facies and the delta front facies to subaqueous delta
plain facies; we can use this fact to estimate the paleooffshore break locations from the cross-sections in
Fig. 2. Therefore, the points at which the time lines
cross this facies boundary are the locations of the paleooffshore breaks. The estimated locations for the last
4 kyr is shown in Fig. 4 including the heavy-dashed lines
of the paleo-offshore break at 4, 3, 2 and 1 ka. The
offshore break line has migrated seaward at an almost
constant rate of about 20 km kyr1 at the central part of
the delta particularly during the last 3 kyr. The present
convex-up delta front topography formed during this
period. Because the distance between the shoreline and
the offshore break is about 20 km, the paleo-shoreline at
3 ka is estimated to have been 20 km landward from the
offshore break line at 3 ka. This position is almost the
same as the landward limit of the beach-ridge field, so
the present wave- and tide-dominated delta was initiated
at that time. This conclusion is concordant with the
sediment facies analyses.
The volume of sediment deposited over the last 3 kyr
can be roughly estimated using the present topography
and bathymetry, the paleo-offshore break line at 3 ka,
and sediment thickness. The paleo-offshore break in the
southern part of the delta is estimated as the lightdashed line shown in Fig. 4. The thickness of the deltaic
sediments is 25 m on average in the study area (Fig. 2)
and is estimated to be 15–20 m in the southern part of
the delta. The calculated sediment volume deposited
during the last 3 kyr is 360790 109 m3 (2075 m in
thickness, 18 103 km2 in area), which is equivalent to
144736 million t yr1 using a bulk density of
1.270.1 g cm–3. Although this is about 10% lower than
the present sediment discharge of the Mekong River
(160 million t yr1), it is within error ranges, so it could
be similar to the present sediment discharge. The
sediment discharge of the Mekong River has not
changed greatly during the last 3 kyr, because there is
no large change in the migration of the offshore break.
More detailed analyses using borehole data from the
southern part of the delta will give a more precise value
for the paleo-sediment discharge of the Mekong River.
This result is different from that found for other
Asian rivers, such as the Changjiang (Yangtze River)
and the Huanghe (Yellow River). Both the latter rivers
T.K.O. Ta et al. / Quaternary Science Reviews 21 (2002) 1807–1819
1817
Fig. 4. Paleo-offshore break of the delta front for the last 3 kyr. The topographic map of the Mekong River Delta and the bathymetric map are based
on Nguyen et al. (2000) and the Topographic Map of Seabed, 1:1,000,000 (1983) respectively. The light-dashed line connecting with the heavy-dashed
3-ka contour of the paleo-offshore break was used for the calculations of the sediment volume of the deltaic sediments for the last 3 kyr.
have been strongly influenced by human activity on a
millennial time-scale (Saito et al., 2001). The global
pristine sediment discharge without the influence of
human activities is estimated to have been one-third of
the present level on a millennial time-scale, and the
increase has been attributed mostly to Asian rivers
(Milliman and Syvitski, 1992). However, the Mekong
River, a large, typical Southeast Asian river, does not
show such a large change in sediment discharge.
Therefore, the total global pristine sediment discharge
from the land to the oceans should be re-estimated.
6. Conclusion
Detailed analyses of samples from six boreholes taken
from the lower delta plain of the Mekong River Delta
show the sedimentation during the postglacial transgres-
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T.K.O. Ta et al. / Quaternary Science Reviews 21 (2002) 1807–1819
sion and the late Holocene evolution of the Mekong
River Delta. The incised valley that formed during
LGM was located around the BT2 site in Ben Tre
Province. The valley was mostly filled during the rise of
sea level after the LGM. The interfluvial zones are about
–20 m in altitude and are covered unconformably by
Holocene deltaic sediments.
The deltaic sediments and detailed chronostratigraphic analyses clearly show the delta progradation
for the last 4 kyr in terms of the sediment facies, wave
influence, progradation rate, and subaerial and subaqueous topography. As the delta has evolved, the delta
environment has become more wave-influenced with the
development of a beach-ridge field, longshore sediment
dispersal, and a steep face of the delta front.
Estimated sediment discharge of the Mekong River
based on sediment volume analysis over the last 3 kyr is
144736 million t yr1 on average, which is only about
10% lower than at present. The constant delta front
migration over the last 3 kyr and the estimated past
sediment discharge indicate that a dramatic increase in
sediment discharge due to human activity, such as
occurred in the Changjiang and the Huanghe, did not
occur in the Mekong River on a millennial time-scale.
Although Southeast Asian rivers have been considered
candidates for dramatic changes through human activity
over the last 2 kyr, the Mekong River example does not
support this hypothesis. Therefore, millennial time-scale
estimates of the global pristine sediment discharge from
the land to the oceans will need to be revised.
Acknowledgements
We express our gratitude to Prof. T. Nakamura,
Center for Chronological Research, Nagoya University,
for helping with the analyses of 14C ages. Critical
reviews by Drs. K. Stattegger, Univ. of Kiel and C.
Murray-Wallace, Univ. of Wollongong improved the
manuscript considerably. We would thank these reviewers and Prof. J. Rose, Univ. of London for kind
suggestions and comments on our manuscript. This
work was part of a collaborative project between the
Sub-Institute of Geography, Vietnam National Center
for Natural Science and Technology, and the Department of Geology, Niigata University, Japan, and the
Geological Survey of Japan, AIST. This research was
funded mainly by the Global Environment Research
Fund of the Ministry of the Environment, Japan. This
paper is a contribution to IGCP Project 437, ‘‘Coastal
Environmental Change During Sea-Level Highstands’’.
References
Coleman, J.M., 1981. Delta: Processes of Deposition and Models for
Exploration. Burgess Publishing Co., Minneapolis, 124pp.
Coleman, J.M., Roberts, H.H., 1989. Deltaic coastal wetlands.
Geologie en Mijnbouw 68, 1–24.
Coleman, J.M., Wright, L.D., 1975. Modern river delta: variability of
processes and sand bodies. In: Broussard, M.L. (Ed.), Deltas:
Models for Exploration. Houston Geological Society, Houston,
TX, pp. 99–149.
Dalrymple, R.W., Zaitlin, B.A., Boyd, R.A., 1992. A conceptual
model of estuarine sedimentation. Journal of Sedimentary Petrology 62, 1130–1146.
Davis, R.A., Hayes, M.O., 1984. What is a wave-dominated coast?
Marine Geology 60, 313–329.
Gagliano, S.M., McIntire, W.G., 1968. Reports on the Mekong River
Delta: Coastal Studies Inst., Louisiana State University Technical
Report No. 57, 144pp.
Galloway, W.E., 1975. Process framework for describing the
morphologic and stratigraphic evolution of deltaic depositional
systems. In: Broussard, M.L. (Ed.), Deltas: Models for
Exploration. Houston Geological Society, Houston, TX,
pp. 87–98.
GESAMP, 1993. Anthropogenic influences on sediment discharge to
the coastal zone and environmental consequences. GESAMP
Reports and Studies No. 52, UNESCO-IOC, 67pp.
Goodbred Jr., S.L., Kuehl, S.A., 2000. The significance of large
sediment supply, active tectonism, and eustasy on margin sequence
development: Late Quaternary stratigraphy and evolution of
the Ganges–Brahmaputra delta. Sedimentary Geology 133,
227–248.
Hanebuth, T., Stattegger, K., Grootes, P.M., 2000. Rapid flooding of
the Sunda Shelf: a late- Glacial sea-level record. Science 288,
1033–1035.
Hayes, M.O., 1979. Barrier island morphology as a function of
tidal and wave regime. In: Leatherman, S.P. (Ed.), Barrier
IslandsFfrom the Gulf of St. Lawrence to the Gulf of Mexico.
Academic Press, New York, pp. 1–27.
Hori, H., 1996. The Mekong: Development and its Environmental
Effects. Kokon-Shoin Publishing Company, Tokyo, 476pp. (in
Japanese).
Hori, K., Saito, Y., Zhao, Q., Cheng, C., Wang, P., Sato, Y., Li, C.,
2001. Sedimentary facies and Holocene progradation rates ofthe
Changjiang (Yangtze) delta, China. Geomorphology 41, 23–248.
Hori, K., Saito, Y., Zhao, H., Wang, P., 2002. Architecture and
evolution of the tide-dominated Changjiang (Yangtze) River Delta,
China. Sedimentary Geology 146, 249–264.
Hu, D., Saito, Y., Kempe, S., 1998. Sediment and nutrient transport to
the coastal zone. In: Galloway, J.N., Melillo, J.M. (Eds.), Asian
Change in the Context of Global Climate Change. Cambridge
University Press, Cambridge, pp. 245–270.
Li, C., Chen, Q., Zhang, J., Yang, S., Fan, D., 2000a. Stratigraphy and
paleoenvironmental changes in the Yangtze Delta during the Late
Quaternary. Journal of Asian Earth Science 18, 453–469.
Li, C., Wang, P., Fan, D., Dang, B., Li, T., 2000b. Open-coast
intertidal deposits and the preservation potential of individual
laminae: a case study from east-central China. Sedimentology 47,
1039–1051.
Milliman, J.D., Ren, M.-E, 1995. River flux to the sea: impact of
human intervention on river systems and adjacent coastal areas. In:
Eisma, D. (Ed.), Climate Change: Impact on Coastal Habitation. :
Lewis Publications, Boca Raton, FL, pp. 57–83.
Milliman, J.D., Syvitski, J.P.M., 1992. Geomorphic/tectonic control of
sediment discharge to the oceans: the importance of small
mountain rivers. Journal of Geology 100, 525–544.
Milliman, J.D., Qin, Y.S., Ren, M.-E., Saito, Y., 1987. Man’s influence
on the erosion and transport of sediment by Asian rivers:
the Yellow River (Huanghe) example. Journal of Geology 95,
751–762.
National Astronomical Observatory, 1999, Chronological Scientific
Tables (Rika-nenpyo): Maruzen, Tokyo, 1058pp. (in Japanese).
T.K.O. Ta et al. / Quaternary Science Reviews 21 (2002) 1807–1819
Nguyen, V.L., Kobayashi, I., 1996. Holocene diatom flora and
sedimentary environment of the Echigo Plain, central Honshu,
JapanFPart 1: the analysis of Fukushima-gata well core. Scientific
Report of Niigata University 11, 13–33.
Nguyen, V.L., Kobayashi, I., 1997. Diatom flora and paleoenvironment of Late Pleistocene and Holocene deposits of Lake Kamo,
Sado Island, Central Japan. Scientific Report of Niigata University
12, 51–83.
Nguyen, V.L., Tateishi, M., Kobayashi, I., 1998. Reconstruction of
sedimentary environments for Late Pleistocene to Holocene coastal
deposits of Lake Kamo, Sado Island, Central Japan. The
Quaternary Research (Daiyonki-Kenkyu) 37, 77–94.
Nguyen, V.L., Kamoi, Y., Kobayashi, I., 1999. Late Pleistocene and
Holocene diatom flora of the Echigo Plain and Lake Kamo, central
Japan. In: Proceeding of the 14th International Diatom Symposium. Koeltz Science Books, pp. 551–563.
Nguyen, V.L., Ta, T.K.O., Tateishi, M., 2000. Late Holocene
depositional environments and coastal evolution of the Mekong
River Delta, Southern Vietnam. Journal of Asian Earth Science 18,
427–439.
Orton, G.J., Reading, H.G., 1993. Variability of deltaic process in
terms of sediment supply, with particular emphasis on grain size.
Sedimentology 40, 475–512.
Reineck, M.E., Singh, J.B., 1980. Depositional Sedimentary Environments. Springer, Berlin, 551pp.
Ren, M.-E, Zhu, X., 1994. Anthropogenic influences on changes in the
sediment load of the Yellow River, China, during the Holocene.
The Holocene 4, 314–320.
Saito, Y., 2001. Deltas in Southeast and East Asia: their evolution and
current problems. In: Mimura, N., Yokoki, H. (Eds.), Global
Change and Asia Pacific Coast. Proceedings of APN/SURVAS/
LOICZ Joint Conference on Coastal Impacts of Climate Change
and Adaptation in the Asia–Pacific Region, APN, pp. 185–191.
Saito, Y., Wei, H., Zhou, Y., Nishimura, A., Sato, Y., Yokota, S.,
2000a. Delta progradation and chenier formation in the Huanghe
(Yellow River) Delta, China. Journal of Asian Earth Sciences 18,
489–497.
Saito, Y., Sato, Y., Suzuki, Y., Sinsakul, S., 2000b. Late Holocene
Chao Phraya delta progradation in the Central Plain of Thailand.
Proceedings of Comprehensive Assessments on Impacts of Sealevel Rise. Dept. of Mineral Resources, Bangkok, Thailand, pp.
62–65.
1819
Saito, Y., Yang, Z.S., Hori, K., 2001. The Huanghe (Yellow River)
and Changjiang (Yangtze River) deltas: a review on their
characteristics, evolution and sediment discharge during the
Holocene. Geomorphology 41, 219–231.
Stuiver, M., Reimer, P.J., Bard, E., Beck, J.W., Burr, G.S., Hughen,
K.A., Kromer, B., McCormac, G., van der Plicht, J., Spurk, M.,
1998. INCAL98 radiocarbon age calibration, 24,000–0 cal BP.
Radiocarbon 40, 1041–1083.
Ta, T.K.O., Nguyen, V.L., 2000. DiatomFindicator of sedimentary
environments and sea-level changes in late Pleistocene–Holocene.
Journal of Science of the Earth 22, 226–233 (in Vietnamese with
English abstract).
Ta, T.K.O., Nguyen, V.L., Tateishi, M., Iwao, K., Saito, Y., 2001.
Sedimentary facies, diatom and foraminifer assemblages in a late
Pleistocene–Holocene incised-valley sequence from the Mekong
River Delta, Bentre Province, Southern Vietnam: the BT2 core.
Journal of Asian Earth Science 20, 83–94.
Ta, T.K.O., Nguyen, V.L., Tateishi, M., Iwao, K., Saito, Y., 2002.
Sediment facies and late Holocene progradation of the Mekong
River Delta in Bentre Province, southern Vietnam: an example
of a tide- and wave-dominated delta. Sedimentary Geology,
in press.
Tanabe, S., Ta, T.K.O., Nguyen, V.L., Tateishi, M., Kobayashi, I,
Saito, Y., 2001. Delta evolution model inferred from the Mekong
Delta, Southern Vietnam. In: Posamentier, H.W., Sidi, F.H.,
Darman, H., Nummedal, D., Imbert, P. (Eds.), Tropical Deltas of
Southeast AsiaFSedimentology, Stratigraphy, and Petroleum
Geology. SEPM Special Publication, in press.
Wang, P.X., Murray, J.W., 1983. The use of foraminifers as indicates
of tidal effects in estuarine deposits. Marine Geology 51,
239–250.
Wolanski, E., Nguyen, N.H., Le, T.D., Nguyen, H.N., Ngoc, T., 1996.
Fine-sediment dynamics in the Mekong River Estuary, Vietnam.
Estuarine, Coastal and Shelf Sciences 43, 565–582.
Woodroffe, C.D., 1993. Late Quaternary evolution of coastal and lowland riverine plains of Southeast Asia and northern Australia: an
overview. Sedimentary Geology 83, 163–175.
Woodroffe, C.D., 2000. Deltaic and estuarine environments and their
Late Quaternary dynamics on the Sunda and Sahul shelves.
Journal of Asian Earth Sciences 18, 393–413.