Abstract

Assam-Arakan basin represents a classical asymmetrical/ foreland basin flanked by NE- SW trending mobile Naga Schuppen belt on the East and Southeast and Arunachal Himalaya to the North and North- East. The present study purports to establish and understand the Late Eocene to Early Oligocene depositional systems of Barail Main Sand (BMS) in terms of the genetic stratigraphic sequence analysis of the region. Well log sequences and seismic stratigraphic analysis together with the with the biostratigraphic studies has been integrated to define various orders of depositional sequences, which are later mapped to bring out the regional depositional pattern. The study shows that the Barail Main Sand is relatively older in the northwestern part i.e in Disangmukh-Rudrasagar area and becomes progressively younger in the east and southeast i.e. Lakwa, Dimulgaon and Galeki area. Therefore, unlike the lithostratigraphy nomenclature, a prodelta to marine shale unit equivalent of BMS has been separated from the underlying Kopili unit, which helped bringing the depositional model more lucidly. A framework of deltaic progradational units, considered as a late High Stand to Shelf Margin System Tract representing a normal regression deposite, attributed to high sediment influx from West and Northwest were probably the favourable factors during the Late Eocene to Early Oligocene sedimentation in Assam Shelf.