1. 1Kyi KHIN, 2Takashi SAKAI
1C.M.C di Ravenna, Singapore
2KyushuUniversity, Japan
Marina Bay Sand Expo and Convention Center
18th September 2012
2. Situated in the Western most part of Myanmar
E: Indo-Burma Ranges, W: Bay of Bengal, N: Chittagong Hills, S: Ramree and Cheduba
offshore Islands
3. NNW-SSE trending 3 long islands
Area: (EW20× NS35 km)
Longitude: 92˚45ʹ to 93˚15ʹE; Latitude: 19˚30ʹto
20˚10ʹN.
Indo-Burman Ranges -elevated Oligocene.
Western Arakan and the Central basins in the
East of the Indo-Burman Ranges-formed on
their flanks.
The basement of the Indian Plate below the
Indo-Burman Ranges is moving toward the
North with respect to the rest of Asia.
Miocene-Pliocene fold belt of western Indo-
Burman Ranges-formed since late Miocene.
5. Bay of Bengal
Andaman Sea
W E
S
N
Tectonically, a juncture of the collision zone
between the Indian and Asian continents to
the North and the subduction zone between
the Indian Plate and Burma Plate to the
East.
The collisional history of the eastern
Himalayas is recorded in sediments
deposited in subsiding foreland basins to
the south including the Bengal basin of
Bangladesh and Bengal Fan.
Bengal-Arakan Basin is a large basin
occupied dominantly by the Paleo-Ganges-
Brahmaputra delta since earliest Miocene.
Exploration for Oil and Gas has been
continuing in the Bengal-Arakan Basin since
few decades.
EHL: Eastern High Land, CLL: Central Low
Land, WR: Western Ranges
WR
CLL
EHL
6. Uddin & Lundberg (2004)
E: The Indo-Burman belt has been accreted onto the Indian Craton margin after the
collision.
Folding within the Indo-Burman Ranges occurred throughout the late Cenozoic
indicates east-west crustal shortening.
This region in the Miocene was near the zone of plate convergence between India and
Burma, with Bengal basin strata overlying the subducting oceanic crust of Indian
plate.
7. Uddin & Lundberg (2004)
N: North-trending folds that are uplifted in the Chittagong-Tripura Folds Belt plunge
northward into the Sylhet Trough.
S: NNW-SSE trending Arakan Coastal Ranges, which occupies western part of the
Indo-Burman Ranges.
Far N: Main Boundary thrust fault, initiated in late Miocene or Pliocene time forms
the northern margin of the Himalayan foredeep, a narrow in this eastern Himalayas. It is
separated from the Bengal basin by Shillong Plateau.
9. Purpose
To provide important information to link the syntectonic sedimentation in the
proximal foreland basins and deep marine sedimentations in distal parts with
episodicity of uplifting and resulted erosional fluxes derived from the India-Asia
collision
Method
-Geological Mapping : Outcrop Mapping with 23- Measured Sections
-Facies Analysis and Sequence Stratigaphy
-Foraminifera Interpretation
-Petrography: Microscopic Thin section Analysis, 60-Point counting Model Analysis
and Provenance Study (38 - Laung Fm, 11 -Yezaw Fm, and 11-Mayu Fm)
-Geochemical Analysis on Mudstone and Siltstone: XRF (major and trace elements
geochemistry of 133 samples were analyzed (80 Siltstone, 53 Mudstone)
10. NNW-SSE trending tight
anticlines and broad synclines
composed with Lower to Upper
Miocene Sequences.
The map pattern in this region
has been compressed by strong
East–West shortening during
the Late Neogene.
13. C
B
C
Slump Folds in FA-3: thin Mudstone
with thick deformed Sandstone blocks
C
FA-3
FA-1
14. E B
D
Convolute laminations in Thin
Sandstone and Shale interbeds of FA-2
Fossiliferous Sandstone bed of FA-3
Gutter-cast (Sandstone) in thin bedded shale FA-4
Dish structures and
convolute
laminations
16. CB
Sharp-based Sandstone with disc structures Debris flow deposits contain rounded
pebbles and disrupted beds (FA-4)
Channelized Sandstone bodies of the FA-4 in Lowermost part of the Laung Fm. (ML1).
Vertical beds with thinning upward succession .
These sediments are interpreted as a low-sinuosity channel facies of the slope and deep
shelf-gully sandstones in the slope environment.
The sharp, scoured surface marking the lower boundary of each graded beds, is indicative
for a marked change the flow energy condition between the systems, in which the
underlying sediment surface was scoured before deposition.
18. C C
C C
Amalgamated Sandstone (FA-4)
Sand dykes in Homogenized Mudstone (FA-3) Climbing ripples in thick bedded sandstone
Hummocky and swaley cross stratifications
in thick bedded sandstone
Climbing ripples in medium bedded
sandstone
19. Dislocated sandstone gutter-cast (gs) overlying
the deformed mudstone (dm)
Basal contact features of the amalgamated
sandstone (FA-4). Irregularly stepped basal contact
immediately underlying chaotic mud (FA-3). Middle
Laung Fm. (ML2)
20. FA-2
FA-3
Downlap contact (arrowed) of FA-2
overlying the chaotic mudstone (FA-3). ML3
Channelized lenticular sandstone (CS) in
FA-2. ML2
Convolute laminations (lower) to Climbing
rippled laminations in sharp-base sandstone
(FA-4). MM2. Upper Mid. Miocene
Shale with thinly laminated sandstone, FA-1.
MM1. Lower Mid. Miocene.
27. Detailed sedimentary structures of heterolithic Facies of FA-5
(Lower to Middle part of Mayu Fm.)
Lenticular laminations Wavy laminations
Climbing ripple laminations Bi-directional cross laminations
33. Thickening toward the south and
toward the east suggests deltaic
deposition prograding southward
and eastward. This further suggests
deeper marine sedimentation
beyond the deltaic deposits to the
43. This is opposite to the pattern normally
seen in foreland basins, due to the
continent–ocean boundary, presumably
exacerbated by sedimentary loading and
basinward downfaulting during Early
Miocene to early Middle Miocene.
Ch: Chittagaung Hills, Sch: Schuppen Belt, Ng: Naga
Hills, As: Assam Basin, Ak: Arakan Basin
Sediments-Acumulation Curves of Assam-
Arakan-Bengal Basins
44. 1. Laung and Yezaw Formations were deposited in the deep marine Slope and
Shelf environments between Early Miocene to Middle Miocene (about 21.5 Ma-11
Ma).
2. Mayu Formation was deposited in the southward prograded shelf-delta
environment during Late Miocene to Pliocene.
3. Forced Regressive Wedged Systems Tracts (FRWST) which evolved slope by-
passing, slumping and following deep-marine channel infilling began to accumulate
the increased sediment load due to the rapid fall of base level presumably
exacerbated by sedimentary loading and basinward downfaulting during Early
Miocene to early Middle Miocene time.
4. Laung Formation and the lower Yezaw Formation demonstrate an overall up-
section enrichment in feldspar, medium- to high-grade metamorphic lithic
fragments whereas the conspicuous change in lithic type, such as chert and meta-
sedimentary lithic fragments which increase more in the upper Yezaw Formation
suggest low input from orogenic belts and high reworking from the older
sedimentary deposits from Indo-Burman ranges.
5. K-feldspar grains increase abruptly in the lower part of Mayu Formation
suggesting that High Himalaya granitic rocks became widely exposed at 11 Ma.
Concluding Remarks
45. 7. Sandstones of the late Middle Miocene are rich in sub angular mono-crystalline
quartz grains, chert and argillite with little amount of feldspar and metamorphic
lithic fragments relative suggesting likely low supply from the Himalayan terrain and
associated with the widespread marine transgression.
8. Sandstones of the Late Miocene-Pliocene (Mayu Formation) and sandstones
contain abundant argillitic and low- to medium-grade metamorphic lithic
fragments and feldspar grains suggesting continued orogenic unroofing. These
younger sandstones are predominant in potassium feldspar relative to the
plagioclase-rich Early to Middle Miocene sandstones, suggesting a granitic source
which is probably from the lesser Himalayas and the High Himalayan Crystalline
terrain.
9. Episodes based on the geochemical and provenance data proxy for the unroofing of
Himalayas are related to the interactions between the timing of Himalayas thrusting,
tectonic denudation and palaeoweathering, migration of foreland fluvial
system and the rate of base-level changes in the Arakan Miocene Basin, Myanmar.
10. These new information based on sequence stratigraphy and provenance data
indicate that sedimentary lithofacies in the fill of this asymmetric basin were controlled
mainly by subsidence due to deltaic progradation over the continent/ocean
boundary, overprinted by tectonic loading and oblique convergence along its eastern
boundary.