Presentation on Structural analysis of Slump Folds from Neogene Deep-marine Slope - Shallow Marine Deposits to get some trace of India-Asia subduction and Collision.

1. Revisit to Baronga Islands, Yakhine,
West Myanmar
50km
Baronga Islands
Kyi Khin and Aung Moe, 2015
N

2. A
B
A’
A
Rangin, 2013Bertrand & Rangin, 2003
Structural and Tectonic maps of Myanmar

3. Regional Geological Map of Baronga Islands, Yakhine, Myanmar (Kyi Khin et al., 2014)

4. 1
1
2
2
3
3
4
4
5
5
6
6
Detailed outcrop mapping
Sittwe Pauktaw

5. Middle Baronga
Syncline
10km
N
East Baronga Island
West Baronga Island
Strike-slip Faults at eastern part of Middle Baronga Island
?

6. Middle Baronga
Syncline
20km
10kmBaronga Islands
East Baronga Island
West Baronga Island
Minor Cross-Faults at Middle Baronga and Clastic dyke near Cross-Fault at East Baronga Is.

7. Middle Baronga
Syncline
20km
10kmBaronga Islands
East Baronga Island
West Baronga Island
Syn-sedimentary fold and faulted contact at Sittwe point

8. Middle Baronga
Syncline
20km
10km
Baronga Islands
East Baronga Island
Minor Cross-Faults and slope scars at West Baronga Island
West
Baronga
Island

9. Laychat taung Island
Slump Folds in Laung
Formation
(Lower Miocene)
at Sittwe PointNote: Photo taken towards South

10. DF
DF
Laychat Taung Island (off-Sittwe Point)
DF: Debris Flow
Conglomerates
CS: Channel Sandbody
AS: Alternated Sandstones
(Levee deposits)
Interpretation
Submarine slope
deposits containing
submarine channels
based with debris flows
and, levee deposits
N

11. Slump folds in Middle Baronga Island
Note: Photo taken towards South
Note: Photo taken towards NorthNote: Photo taken towards East
Note: Photo taken towards West

12. Regional Structure Development
Shillong Massif
Figure (A)
Figure (B)
Present Structural development of Surma Basin, Bengladesh with the interpretation of the superposed
regional folding related to Himalayan orogenic movements (A) and its three dimensional model explanation
(B).

13. • Regional scale development of dome and basin pattern in Bangladesh and Yakhine
coastal strip (Myanmar) is shown by Hiller and Elahi (1984), Tappan (1990) and
Gani and Alam (1999). Now a day those of structures can be easily recognised
satellite image by Google Earth.
• In the figure (A) dome and basin pattern of Surma Basin (Bangladesh) (Hiller and
Elahi 1984) is used as a model for interpretation of deformation. By joining the lines
of dome and basin, the traces of the three sets of folds (F1, F2 and F3) can be
recognised. These dome and basin structures are called a superimposed folding
(Ramsay 1967) and interfering folding (Ghosh 1993).
• In the three dimension (Fig. B), the first folds (F1) show homoaxial cylindrical E-W
trend horizontal folds. The first folds become distorted and their limbs refolded
with new axial directions. Antiformal second folds are superposed across a first fold
antiform. There is a mutual culmination in both sets of folds resulting in the
formation of a dome like structure. Similarly crossing synforms produce mutual
depressions in both sets of fold axes and the development of a basin structure. As a
result of this interaction the surfaces are folded into a series of alternating domes
and basins, each basin surrounded by four domes, each dome by four basins.

14. Fig. D.Ridge and Valley development in
Bangal fan area.
Fig. C. Fold and fault development on the
Bangladesh and Yakhine coastal area.
F1 Fold
F2 Fold

15. CHARACTER OF FOLDS
• F1 fold is open and gentle. Therefore it was formed by slowly movement (4cm/year: Rangin
2012, Than Htut et al. 2012) with gently stop of Indian plate. F1 fold axis is trending generally
EW direction, which indicates to the northward movement of Indian plate. F1 folds are nearly
upright, symmetry and no vergency, shows the straight northward movement.
• The character of F1 fold distinctly shows that it was formed in the open area of the Bay of
Bangal unfolded sediments, intensive folding commences towards the N continental slope of
the Bay, which was followed the Indian plate northward movement. It was moved very slow
and regularly. When the movement was suddenly stopped by buttress with Shillong Massif
during the Miocene time Himalayan uplift (Uddin and Lundberg 1998), become folded.
Therefore F1 fold is open and gentle.
• F2 fold is narrow and tight. Therefore it was formed by the force of movement and pressed
by the Indian plate. The axis is trending NS direction, which indicates the eastward
propagation of Himalayan collision against to the buttress of Indo-Burman Ranges. F2 folds
are upright, symmetry and no vergency, shows the straight eastward movement.
• F2 fold shows the superimposed folding upon the F1 fold. It moved also slow and regularly,
but later become faster and butted with Indo-Burman Ranges. Therefore F2 fold is narrow
and tight.
• In the F2 fold, Miocene sediments are folded together with Mio-Pliocene sediment. F2 fold
was formed during the Pliocene-Pleistocene eastward propagation of Himalayan collision.
• F3 fold is distinctly found near the Shillong Massif. Along Dauki fault Shillong Massif was
moved eastward by force of Indian plate movement and dragged the folded Bangel fan area.
• By this movement, Kaladan fault and Chittagong coastal fault could be formed as right-lateral
strike slip movement (Rangin,2012).

16. FOLD GEOMETRY AND STEREOPLOT
Fig. E. Equal-area Stereonet plot of Sittwe and Barong Islands.
Black coloured half-circles= Bedding (S0) 245˚/60˚ F2 folds; Red coloured half-circle=Bedding (S0) 360˚/15˚
or 180˚/15˚ F1 folds.
1. Restoration of Plunge Angle=30˚, 2. Restoration of F2 fold dipping = 60˚ and 3. Construction of F1 fold
limb=15˚

17. Strike-slip motion (Extension)
Oblique Motion (Crustal shortening)
Sketches showing NW-SE trend double plunging Folds which as a model
of the slump structures development in Syn-Sedimenatary deposition of
paleo-submarine slope deposits in Baronga Islands , Yakhine, Myanmar
Paleo-Slope trends from Gutter Casts direction
SW
SSE
Lr. Mio
Mid. Mio
Bangladesh
N

18. Conclusion
• NW-SE Trended Faults developed by of riedel shear
movement and sub-parallel with Kaladan and Chittagaung
Coastal Faults
• Paleo-slope Trend in Lower Miocene show SW and changed
SSE in Middle Miocene
• Slump folds were formed by syn-sedimentary deformation
including gravity sliding at eastern Bengal paleo-slope
• Double plunging folds were developed by NE-SW oblique
subduction of India Plate and later right-lateral strike slip
extension

19. Thank You