Download off Thailand coast Clay Mineralogical Records in Sediments along

Clay Mineralogical Records in Sediments along the Shelf Break of the Eastern Andaman Sea
Bunsomboonsakul, S.1,2 , Liu, Z.F.1, Sompongchaiyakul, P.2, Snidvongs, A.3 and Krastel, S.4
1State
Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China
2Department of Marine Science, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand
3Southeast Asia START Regional Center, Chulalongkorn University, Bangkok, 10330, Thailand
4Leibniz-Institute of Marine Sciences IFM-GEOMAR, Kiel, Germany
Core sediment details
Introduction;
Method;
The Andaman Sea Basin located between the Irrawaddy delta coast of Myanmar, which extends 1,200 km.
southward to Sumatra and the Malacca Strait, has very complex sea floor morphology (Rodolfo, 1969).
Clay minerals were identified by X-ray diffraction
(XRD) using a PANalytical diffractometer at the State
Key Laboratory of Marine Geology, Tongji University
The sediment distribution in the Andaman Sea is dominated mainly by the oceanic condition that has been
strongly influenced by two prevailing monsoon seasons; the northeast (November-April) and the
southwest (May-October) monsoon (Rao P.S. et al., 2005). Due to monsoon, the arrival of strong summer
winds dramatically drive the westerly current to the prevailing south-easterly current resulting in the
transportation of riverine sediment moving eastward along the inner shelf (Rodolfo, 1969; Ramaswamy et
al., 2004; Rao et al, 2005).
MASS-III-007
Description
The clay mineralogy has been used to differentiate the source of terrigenous sediments
and marine sediment as well as the geological condition such as weathering process. The
clay mineral assemblages in ocean sediment is well significant a proxy to differ source
possibility, propagation of water masses and to investigate ocean system. Moreover, the
fined-grained clay minerals can be convey to determine the distance from the sediment
original source and settle pattern. The distribution in the main group of clay mineral
which are smectite, illite, kaolinite and chlorite can used to illustrated the sedimetological
processes.
Depths
(cm)
5-8 cm. Light brown
sand
8-23 cm. Light brown
sand/silt
23-158 cm.
Dark olive
grey
sand/silt
mostly
foraminifera
Lithology
Smectite
(64-80%)
Illite
(5-11%)
Kaolinite
(9-18%)
Chlorite
(3-10%)
δ18O
(-3 -1）
10
Tectonic (left) and bathymetric (right) map of the Andaman
Sea. Tectonic map is taken from Curray (2005).
The large amount of fluvial
input of Irrawaddy river form
the northern part is transport
mainly eastward along the
coast into the eastern of
Andaman Sea and rest settled
offshore by the continental
shelf and due to the forced and
transported
by
Sumatra
streams from the strait into the
south Andaman Sea.
Dark brown
silt
mostly
foraminifera
18-150 cm. Olive grey
clay/silt
20
30
40
50
Lithology
Smectite
(64-80%)
Illite
(4-13%)
Kaolinite
(10-17%)
Chlorite
(2-11%)
δ18O
(-4 0）
10
20
30
40
50
60
60
70
70
80
80
90
90
100
93-95 cm. coarse layer
by shell
fragments
120
100
110
120
130
The preliminary results reveal that the cores contain high smectite (65-79%) and kaolinite
(9-18%), and low illite and chlorite contents (<10%). Although clay mineral contents of
the two cores shows similar average compositions, the vertical profiles of distribution are
displayed reversely particularly for smectite, kaolinite and illite.
Surface sediment; off Myanmar coast
Chlorite
16%
Smectite
44%
Illite
23%
Chlorite
7%
Kaolinite
17%
Illite 8%
Smectite
Kaolinite
12%
Smectite
72%
MASS-III-07
MASS-III-10
Chlorite
11% Smectite
MASS-III-007
Chlorite
6%
Illite 18%
23%
Kaolinite
12%
Smectite
73%
Conclusion;
The results from core sediments suggest that the sediment transport in
this area was strongly controlled by the current direction. In comparison
of clay mineral compositions of the two cores with the surface sediments,
it is implied that the potential terrigenous sediment input to the Andaman
Sea was likewise from Myanmar than from Thai rivers.
(1) The average clay mineral assemblage of core sedimemt consists of
Smectite (65-79%), Kaolinite (9-18%), and Illite and Chlorite contents
(<10%). The values of illite crystallinity range is 0.10 °–0.25°Δ2θ.
(2) The provenance analysis indicated 3 end-member sources: almost
smectite content of core sediment has possible derived from
Northeastern Andaman Sea likewise the content of Myanmar
sediment more than Thai sediment while kaolinite is sourced from the
Thai coast. The illite and chlorite content is showed in low percentage.
MM- Surface
sediment
Kaolinite
47%
Illite 8%
140
150
The sediment off Myanmar Showed the high content in smectite by
44.3% (average form 40 stations) in the other hand the sediment off
Thailand coast showed the high content in kaolinite by 47.5% (average
form 26 stations).
(Jintasaeranee et al, 2012)
130
140
Furthermore, The surface sediments were collected from off Thailand
coast to represent the middle part source and off Myanmar coast to
represent the northern part source, respectively.
Abstract
Distribution of sediments in the Andaman Sea is strongly influenced
by two prevailing monsoon seasons: northeast (November-April)
and southwest (May-October) monsoons. In this study, clay
mineralogy has been inquired to indicate sediment transportation
and provenance of the Andaman Sea sediments. Two sediment
cores from offshore and surface sediments from two nearshore
locations in the Andaman Sea were studied. The cores of 1.58 m
(MASS-III-07) and 1.50 m (MASS-III-10) long were collected from
along the Andaman Sea shelf break off the west coast of Thailand.
The surface sediments were collected from off Thailand coast to
represent the middle part source and off Myanmar coast to
represent the northern part source, respectively. Semiquantitative
analyses of clay minerals were performed using X-ray diffraction
(XRD) to document clay mineralogical composition and distribution,
and to reconstruct the chronological oceanic processes. The
preliminary results reveal that the cores contain high smectite (6579%) and kaolinite (9-18%), and low illite and chlorite contents
(<10%). In comparison of clay mineral compositions of the two
cores with the surface sediments, it is implied that the potential
terrigenous sediment input to the Andaman Sea was likewise from
Myanmar than from Thai rivers.
Depths
(cm)
6-18 cm.
110
Results;
MASS-III-010
Description
Illite Chemistry
TH- Surface
sediment
0.8
0.6
Surface sediment; off Thailand coast
0.4
MASS-III-010
0.2
Illite + Chlorite
Kaolinite
0.10
0.15
0.20
0.25
Illite Crystallinity (Δ2θ)