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Noor Alam, MD.
- Stratigraphic and Structural Features of the Surma Basin and the Upliftment of the Madhupur Tract of Northeastern Bengal Basin
Authors
1 Bangladesh Petroleum Institute (BPI), Sector # 8, Plot # 5A, Uttara Model Town, Dhaka-1230, BD
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 69, No 6 (2007), Pagination: 1319-1327Abstract
The structural features developed under the influence of regional tectonics that in turn controls the seismo-stratigraphy in the northeastern part of Bangladesh have been illustrated in this paper. Almost all prominent seismo-stratigraphic horizons represented by continuous, high amplitude reflections that extend over a fairly large distance were identified, traced, and mapped. Interpreted sections reveal the structures and arrangement of the Tertiary-Quaternary succession in the Bengal Basin area while the areal extent maps of the youngest eight prominent seismo-stratigraphic horizons revealed a fair picture on the relative distribution of the near-surface stratigraphic horizons developed under the influence of associated tectonics in the northeastern part of Bengal Basin.
Two interpreted composite seismic sections across the Barind Tract and the Madhupur Tract reveal that, they belong to different seismo-stratigraphic horizons where the Barind Tract seems to correlate with the older seismic horizons than the Madhupur Tract. Structurally the exposure of the Madhupur Tract coincides with the crestal part of a low amplitude, broad anticlinal fold with it's NW-SE trending axis stretching along Sariakandi in Bogra District to Bhuapur in Tangail District and further southeast towards Lalmai. A similar pattern is observable on the LANDSAT imagery of Bangladesh. This broad anticlinal feature separates spatial distribution of some of the Pleistocene and younger sedimentary horizons of the Surma Basin from that of the Faridpur Trough as well as south of the Barind Tract.The composite areal extent map mostly comprising seven youngest seismo-stratigraphic horizons of the Quaternary sequence in the Surma Basin is representative of their inter-relationship. The areal extent of these horizons gradually decrease with time and dip towards their common depocenter near Tangua-Raular Bils (Marsh) north of Madhyanagar Thana in Sunamganj District. The Tangua-Raular Bils (Marsh) coincides with the axis of a broad synclinal fold between the Madhupur Tract and the Chhatak anticline where the Pleistocene formation has undergone a continuous subsidence of about 2 km during post-Pleistocene time. These sediments were probably deposited in a fluvio-lacustrine environment. The Quaternary sediments have excellent developments in this area and therefore can be considered as type locality for the Quaternary deposits in the Bengal Delta. On the other hand the Quaternary sediments on the west and southwest of the Madhupur Tract and that south of the Barind Tract were deposited in a rather active deltaic environment and were severely affected by river erosion. These sediments most probably have been brought in by the river Ganges and its tributaries and distributaries and the delta prograded rapidly towards the Bay of Bengal to the south.
