Abstract

• The next occurrence of the Middle Devonian Unit which is the equivalent unit of the Pwepon Limestone in Pyinoolwin Township, recognized in the Maymyo Formation, Hsipaw area, northern Shan State. It exposed as an isolated outcrops of only one soil-covered hill which is now seeing as road-cut section near Kontha village. Primary petrographic study indicate that the limestone varies essentially medium- to coarse, locally argillaceous, calcilutite with abundant biogenic debris in the middle part and an intraclastic biogenic calcilutite with fine- to medium-grained in the lower and upper parts. Microstylolites with iron stained argillaceous concentrations and brecciation are developed in places. The fossiliferous unit is laterally passed into dolomite or dolomitic limestone which is regarded as the sandwiched unit of the MaymyoFormation. Initial fossil studies have led to the recognition of rugose, tabulate and brachiopods faunal assemblages. These are solitary rugose corals of Temnophyllum, Grypophyllum, Macgeea, Cyathophyllum, Acanthophyllum, Dohmophyllum and abundant colonial rugose corals of Argutastrea; tabulate corals of Alveolites, Coenites, Favosites and brachiopods of Spinatrypa, Atrypa, Desquamatia, Strophomena, Reticulariopsis, Athyris and Xystrostrophia. This coral assemblage is quite similar to Pwepon Limestone but this unit is more argillaceous, fossiliferous, more abundant brachiopods and corals attain larger size. This unit is not previously described in Hsipaw area.