Neogene Sedimentary Fringe, West of Indo-Burma Ranges, in Western Myanmar: Some Evidences for Late Cenozoic Synorogenic Sedimentation in Himalayan-Bengal System

Khin, Kyi¹; Sakai, Takashi²
¹Oil and Gas Division, Jurong Consultants Pte Ltd, Singapore, Singapore.
²Earth and Planetary Sciences, Kyushu University, 6-10-1, Hakozaki, Higashi-kuFukuoka, Japan.

The Arakan Basin is one of the representative clastic basins formed in the frontal part of the Himalayan orogenic belt since Late Cenozoic. Defining one of the four major sedimentary basins of Myanmar, it is geomorphologically and tectonically differentiated from the others. The study area along the westernmost edge of Myanmar is separated from the Arakan Yoma (Indo-Burma Ranges) by a narrow coastal strip and is bordered by the Bay of Bengal to the west.

Based on planktonic foraminifera zonation, regional stratigraphic correlation and geological age of the siliciclastic sequences were established. Deep marine slope and shelf environments during early Miocene to middle Miocene (about 21.5 to 11 Ma) southward prograded shelf-delta environment during late Miocene to Pliocene time were determined.

The early Miocene underthrusting along the Himalaya front is well documented by the forced-regressive sedimentation patterns in the slope and shelf systems, sediments of which derived from the paleo-Ganges-Bramaputra river systems in the Bengal-Arakan Basins. Sequential evolution of the Miocene successions manifests that forced regressive wedged systems tracts, 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 the sea level by the uplifting in the hinterlands during the early Miocene to early middle Miocene time.

The formation of a shelf-delta system marks a dramatic shift in the evolution of the southward prograding delta system following a eustatic sea-level low. In the foreland areas, erosional off-loading with foreland uplifting caused wide active fluvial system and formed transverse rivers distally in the late middle Miocene to late Miocene.

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012