The Western Ranges

The Western Ranges consists of two different geological units, namely a board flysch range, which constitutes the main section, and a narrow, intermittently outcropping zone of metamorphic rocks, ophiolite, Triassic Halobia schist and an Upper Cretaceous sequence at their E margin. Flysch-type sediment characteristics, such as alternating beds of greywackey, sandstone, siltstone, claystone and shale, graded bedding, rhythmic interbedding of sandstone and schists, and sole marks can be observed in this rock sequence. The Naga metamorphic Complex contains meso-metamorphic rocks, i.e dark and sometimes graphitic, biotite-muscovite and biotite-muscovite-sillimantie schist, frequently in association with banded paragneiss, sericitic quartzite and the carbonatic Pansat Series.  

The Western Belt of the Indoburman Ranges consists of deformed Senonian mudstone and pelagic limestones, or Chin Flysch, and overlying Eocene and younger clastics (United Nations, 1978b) and is faulted against the Eastern Belt. The surface trace of the active subduction zone between the Indain Plate Myanmar lies west of the Chin Flysch, which can be projected into the Yarlung suture zone in Tebit. Small of less deformed strata of molasse facies were probably deposited in shallower water above the rising flysch strata probably in Late Eocene or Early Oligocene while their coal non-marine strata were laid down in the adjancet tough above the trench, like Yaw and part of Pondaung Formations. The flysch strata were deformed and weekly metamorphosed in the trench environment be north the frontal edge of overriding continental plate.

Within the Pondaung Formation of Late Eocene age some possible small non-marine subunits are exposed. The overlying uppermost Eocene unit, the Yaw Formations is composed of numerous commercial coal seams indicating the non-marines deposition. Line of the western outcrop, exposed as isolated hills of big mountain masses like Paungmin Taung near Htelin, Pyarnattaung near Gangaw and Geiksgoke taung southeast of Kalemyo or as several small Low Hill, lense and individual beds intercalated with flyschoid mudstone and sandstone of comparable age, along the eastern margin of Myittha and Kabaw valleys of the CMB.

Within the Pondaung formation of Late Eocene age some possible small non-marine subunits are exposed. The overlying upper most Eocene unit, the Yaw Formation is composed of numerous commerciate coal seams indicating the non-marine deposition.

reference: 

Atlas of Mineral Resources of the Escpe Region Volume 12, 1996