Contents

Page No.

1.Introduction / 1
2. Geology of Bangladesh / 2
2.1. Physiography of Bangladesh / 2
2.2. Tectonic Set-up of the Country / 3
2.3. Stratigraphy / 4

2.4. Quaternary of the Bengal Basin

/ 6
2.5 Pleistocene Sediments / 6
2.6. Sea Level Changes and Late Pleistocene-Holocene Sedimentation / 7
3. Aquifer Systems in Bangladesh / 10
3.1 Division of the Aquifers / 10
3.2. Conventional Aquifers / 11
3.3. Division of the Aquifers from Geological Point of View / 12
4. Distribution of Arsenic in Groundwater of Bangladesh / 14
4.1 Arsenic distribution and Geology / 14
4.2. Arsenic Concentration in the Sediments / 15
5. Conclusions / 16
6. Recommendations / 16
7. References / 18

List of Figures

Fig. 1. Map of point source arsenic concentrations observed in groundwaters in the national hydrochemical survey
Fig. 2. Documented cases of arsenic problems in groundwater related to natural contamination.
Fig. 3. Contour map of Bangladesh
Fig. 4. Generalized physiographic map of Bangladesh
Fig. 5. Tectonic map of Bangladesh.
Fig. 6. Correlation of stratigraphic sections from the Himalayan foredeep across the Bengal Basin.
Fig. 7. Map showing the Bengal Basin with Tectonic elements.
Fig. 8. Schematic crustal cross section through the line X-X’, Y-Y’ of fig. 7
Fig. 9. Sea level changes during the last interglacial transition
Fig. 10. A sea level curve from Panigati based on the age and altitude of 4 radiocarbon dated samples
Fig. 11. Profiles of Holocene sediments a) Section across Ganges Delta in West Bengal, B) Section across Jamuna flood plain and Ganges delta in Bangladesh.
Fig. 12. Grounwater development zones.
Fig. 13. Hydrological cross section from north-south across Bangladesh
Fig. 14. Revised hydrological model based on isotopic and hydrochemical data
Fig. 15. Schematic diagram of the aquifers on the geological point of view.
Fig. 16. Geological cross section across the coastal area (E-W)
Fig. 17. Possible relationship of fresh and saline groundwater in SW Bangladesh.
Fig. 18. Lithologic column at salbanhat Test Hole, Panchagarh District.
Fig. 19. Map of smoothed groundwater arsenic concentration from national hydrochemical survey.
Fig. 20. Geological map of Bangladesh

List of Tables

Table 1. Generalized stratigraphic sequence of Bangladesh. / 5
Table 2. Comparative divisions of the Late Pleistocene-Holocene sediments in Bangladesh and West Bengal. / 8
Table 3. Results of the analyses of rocks and sediments of Bangladesh for arsenic / 15