Contribution to the Foraminiferal Biostratigraphy and Paleoecology of the Pyawbwe Formation, Sakangyi – Thayet Area, Myanmar

Litho- and foraminiferal biostratigraphic studies were carried out on the Lower Miocene siliciclastic Pyawbwe Formation exposed at Sakangyi area, Myanmar. The investigated planktonic and benthonic foraminiferal species showed great similarities and close affinities to those of the Mediterranean Region. The studied planktonic foraminifera were grouped into three globally foraminiferal biozones compared with standard biozones N4, N5, N6 and N7. The benthonic foraminifera revealed two locally biozones arranged from base to top as follows; 1- Ammonia beccarii and 2- Bolivina vaceki Zones. Three abundant foraminiferal assemblages are defined, characterised and documenting three environmental factors, energy levels, oxygen levels and water productivity. Near the base and top of the section both foraminiferal taxa abundance and diversity are very extremely low, corresponding to the increased sand content indicating high energy levels and turbidity. The Pyawbwe Formation may be deposited under shallow marine. The middle part of the section was deposited in relatively deeper marine conditions (> 30 m. to 150 m. depth) and regressed in upper most parts to lagoon depth less than 30 m.