Abstract

• The study area is situated in Mawlamyine and Mudon Townships, Mon State. It is mainly composed of Early Carboniferous to Early Permian clastic sedimentary rocks comprising shales, mudstones, pebbly mudstones, sandstones, gritty sandstones, conglomerate and pebbly greywacke. Nine lithofacies of Taungnyo Formation are recognized; (1) dark grey color thick-bedded mudstone facies, (2) dark color pebbly sandstone facies, (3) dark color pebbly mudstone facies, (4) conglomeratic gritty sandstone facies,(5) gritty sandstone facies ,(6) medium to thick-bedded sandstone facies, (7) thin to medium-bedded sandstone facies, (8) thin-bedded sandstone with shale interbeddedfacies and (9) sandstone and mudstone interbeddeddfacies. It is divided into three lithofacies associations; (1) pebbly greywacke-pebbly mudstone-shale association which represents upper and lower fan sequence ,(2) conglomerate-gritty sandstone-sandstone-shale association represented upper fan and mid fan sequence and (3) sandstone-shale association representing mid fan channel and basin plain of lower fan sequence. By studying the rocks of Taungnyo Formation it is characterized by high velocity turbidity current, low density turbidity current, fine-grained sandstone with low velocity and coarse-grained sandstone with high velocity turbidity current of submarine fan environment. Taungnyo Formation was formed as a submarine fan and taken place in the deep sea. This is forming as a sand-rich and mixed sand-mud turbidite system. Growth and deposition of a turbidite system are intimately tied to a cycle of eustatic or relative sea-level change. During a maximum regression, the shore line moved basinward and the fluvial system placed on the exposed shelf area and most of the sediments were deposited in continental slope area. This regression is also coincided with the global sea level drop.