Eocene-Miocene Stratigraphy of Surma Trough: a Sequence Stratigraphic Approach

Haque AKM Eahsanul¹, Islam Aminul², Downey Bill², Alam M. Mustafa³

1Weatherford Products & Equipment Pte. Ltd., Singapore; 2Dept of Petroleum Geoscience, Universiti Brunei Darussalam, Brunei; 3Dept. Of Geology, University of Dhaka, Bangladesh

akmeahsan@yahoo.com; aminul_gm_ru@yahoo.com, billdowney49@yahoo.com; mmalam49@yahoo.com

The Bengal Basin is considered to be the deepest basin of the world; however not much works have been done in the basin as a whole for establishing sequence stratigraphic boundaries. Therefore, the stratigraphic framework of the exposed Eocene to Miocene sediments in the Jaintiapur and surrounding areas, northeastern Sylhet involves surface sedimentological studies along with the sequence stratigraphic modeling of the Sylhet trough. Analyses of the facies and facies-associations have been considered one of the better ways to understand the depositional environment and it has been chosen in the present study for the interpretation based on the available sedimentological data. Hence the research work on the sequence stratigraphy of the exposed Eocene to Miocene sediments of Jaintiapur and surrounding areas of northeastern Sylhet is undertaken in order to understand the sequence stratigraphic framework of the area which may include future sub-surface studies in the basin. The exposed Eocene to Miocene sediments includes the rocks of the Dauki Allogroup, Tamabil Alloformation and the Surma Allogroup. Though the Dauki Allogroup includes the Tura Formation, Sylhet Limestone and Jaflong Shale Formation, sequences of Tura Formation is not exposed in the study area. The Tamabil Allogroup has been considered as the undifferentiated unit. Both the Jaintiapur Alloformation and the Afifanagar Alloformation are well developed in the study area. For the present study, parasequences, system tracts, bounding surfaces and sequences of the exposed Eocene to Miocene sedimentary deposits of the study area have been redefined and are recognized in response to changes in relative sea level, sediment influx and paleo-physiography.

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