Palaeoenvironmental Deductions of Microfossil Flora and Fauna of the Shiala and Yong formations, Tethyan Garhwal Himalaya

The present study is an interdisciplinary approach to put forward a precise picture of Ordovician-Silurian acritarcha and other associated microfossil distribution in the Lower Palaeozoic Tethyan sequence of the Garhwal Himalaya, lndia For the purpose, sedimentological data, macrofauna and microflora from the Shiala and Yong Formations have been considered to constrain the environmental distribution of the microfossils It has been found that chitinozo and melanosclerites as well as acritarcha of Garhwal Tethys Himalaya have a wide range of adaptation The acritarcha bloomed during cool marine condition whereas chitinozoa and melanosclerites preferred mainly In warm-water condition of blooming The Shlala Formation was deposited under cool-water conditions In a shallow pulsating basin with a rapid variations In the depositonal environment and frequent sea-level changes This formation has been affected by the fluvial influx intermittently and possibly there was a sea-level drawdown at Ordovician-Silurian boundary An attempt has been made to correlate this phenomenon with a possible Late Ordovician glacioeustatic event and it is found that the Hirnantian glaciation was probably not situated in the Himalayan region The Yong Formation was deposited mainly in a shallow subtidal setting in a tranquil and low energy ancient warm-water mass.