Abstract

• A new occurrence of the Middle Devonian Unit equivalent to the Padaukpin Limestone in Wetwin-Padaukpin area is recognized for the first time in the lower part of the Maymyo Formation, Lashio area, northern Shan State. It exposed as isolated outcrops only at two localities in Lashio area. The unit mainly composed of from base to top; (1) medium- bedded, grey to dark grey calcitic limestone intercalated with thin-bedded, black shale with abundant recrystallized gastropods (Quarry near the Hseing Hkai car-road, N 22˚ 53 36 and E 97˚40 51); (2) medium-bedded, ligh grey to buff, argillceous limestone with buff to black shale and siltstone containing abundant crinoid stems, cystoid plates and brachiopods and (3) medium-bedded, light grey to grey, calcitic limestone and buff coloured argillaceous limestone interbedded with buff to black shale and siltstone comprising abundant tabulate and rugose corals (along the car-road from Lashio to Muse at mile post 5-6 furlong, N 22˚ 54 02 and E 97˚4208). This unit is also the sandwiched unit in the Maymyo Formation and laterally passed into the dolomite or dolomitic limestone. The age of the unit exposed at the Lashio area is defined by the strong faunal evidences such as gastropods: Muchisonia sp., oonema sp. and Euromphalus sp. and important tabulate and rugose coral species: Favositesgoldfusi, Alveolites sp., Coenites sp., Aulocystics sp., Stringophyllum sp., rypophyllum sp., Temnophyllum sp., Acanthophyllum sp., Peripaedium sp., Cyathophyllumsp. and abundant Calceolasandalina. Calceolasandalina which are known as a typical Middle Devonian (Eifelian) species in Myanmar, Europe, USSR, Asia and Australia. It is a more complete succession of the faunal assemblage with Middle Devonian age and slightly different in lithology and faunal content with the type section of the Padaukpin Limestone.