Geology of Bangladesh

The South-Central region of Bangladesh is crisscrossed by numerous rivers and small creeks. These waterbodies carry a significant amount of sediment load to the Bay of Bengal. In fact, it is the most active part of the Bengal Delta, which has been undergoing massive morphological changes since historic times. Because of the morphological changes of the river channel as well as coastal shorelines, people have to shift their living places from these areas frequently. Severe erosion and accretion of the riverbanks and shoreline cause significant damage to people, with croplands bearing the brunt of the damage. Even high tide inundates their land regularly. Hence, it was crucial to study the morphological changes of the riverbanks and shoreline of the south-central region. This report illustrates the amount of erosion and accretion of the rivers as well as the shoreline in the south-central region. It is found that the rivers in this region have gone through more accretion than erosion in the past two decades. However, the Kuakata beach has gone through more erosion than accretion during the timeframe. The report also depicts the observation and description of collected samples from the beach. It provides the description of physiographic conditions, geomorphic features, geological resources and also the reasons behind the structure of the major rock units. We found mostly sedimentary structures, which are formed mostly by the water current and action, such as ripple marks, dunes, burrows, etc. The study of lithology, sedimentary structures, grain size parameters and degree of sorting reveal that the sediments were deposited in fluvial to shallow marine environments.

This report aims at geologically characterizing the area, which was investigated by the students of 3rd year, Department of Geology, University of Dhaka. It deals with the physiography, geomorphology, structure, stratigraphy, petrography and its interpretation, correlation with standard geologic succession, economic geology of Janitiapur-Tamabil, Sylhet, Northeastern Bangladesh, along with the facies analysis and interpretation of paleo-environment of depositional history. The investigated area lies in between 25°05´ N to 25°11´ N and 92° E to 92°11´15´´ E, latitude and longitude respectively. It is a hilly region with irregular topography. Highest elevation of the investigated area is 301 feet above the MSL. The drainage pattern of the area is mainly dendritic. Structurally, the area is an outer reflection of a monocline that trends nearly E-W. The area exposes both fossiliferous and non-fossiliferous thick sequence comprising of a succession of limestone, sandstone, shale, siltstone and claystone. Lithostratigraphically, the sedimentary sequence of the area is divided from bottom to top as Sylhet Limestone Formation, Kopili Shale Formation, Barail Group, Bhuban Formation, Boka Bil Formation, Tipam Sandstone Formation, Girujan clay Formation, Dupi Tila Formation, Dihing Formation and Alluvium. The age range of these formaions is Middle Miocene to Pleistocene. The constituent rocks of the region are of Sedimentary origin. It appears from the rock records that the depositional conditions in the basin varied quite considerably and were at time cyclic in nature. Analysis of different facies associations that observed in different formation and application of different facies model indicates that the Sediments of different formations were deposited in continental, continental fluviatile , deltaic, shoreline, shoreline marine. The petrographic analysis of the collected samples is included in this report which is performed with a view to define and classify sandstones, to reconstruct their provenance tectonic relations, to illustrate the diagenatic changes and to find out stratigraphic implications. The limestone exposed in the investigated area and the gravels carried by the rivers are economically valuable. Moreover, it is to be mentioned that the adjoining areas have high prospect for hydrocarbon exploration.

After the nuclear tests conducted by India and Pakistan in May 1998, experts, particularly the former US president Bill Clinton, described the region as becoming a dangerous region in the world. This description of South Asia is to be viewed in the context of the uneasy relations between India and Pakistan since their independence. The geopolitical disputes among South Asian countries have remained an area of unresolved and dangerous conflict involving external powers, arms proliferation and ethnic and religious hatred that go back to the evolution of India,

Atlas of Urban Geology, FORUM ON URBAN GEOLOGY IN ASIA AND THE PACIFIC, THE GROUND BENEATH OUR FEET: A FACTOR IN URBAN PLANNING, UN ESCAP , 1999

The rapid growth of population, urbanization, communication and infrastructure development in Bangladesh has sharpened the need of understanding the geological processes that some times cause severe natural and man-made disasters. The natural landscape of Bangladesh can distinctly be portrayed as active plains of fluvial, deltaic and coastal environments, having few strips of low hills in the east and northeast. The country is prone to annual flood and other climatic hazards. The general elevation of the deltaic and coastal plain land is only 2 to 4m above mean sea level. There are number of large and small clusters of urban growth throughout the country, among these the capital city of Dhaka, the port cities of Chittagong and Khulna (Mongla Port), Rajshahi, Sylhet, Mymensingh, Bogra and Barisal are important. Most of the urban centers are located on naturally raised land facets. The physical growth of these urban centers is so fast that it has become difficult to maintain a systematic land-use pattern of these clusters. The geological disadvantages or advantages for economic and rational engineering design are overlooked. For this many of the newly grown areas have incurred severe damages due to flood, cyclone and tidal surges, riverbank and coastal erosions, landslides, soil collapse and foundation failures. Due to increased frequency of failures in different projects and structures, the concerned authorities are paying attention to the inherent causes of the failure or taking measures to avoid further disruptions. After the independence of Bangladesh the development activities started so rapidly that a time lag remained between the planners and developers in interchanging the necessary geo-information and data for rational designing or formulation of the projects. In recent years, the city planners and other national organizations like the city improvement authority, the roads and high ways department and the public works department have extended hand for geological information for proper understanding of geological aspects of their projects. Considering these, the Geological Survey of Bangladesh (GSB) has taken up a National Mapping Programme for preparation of geological maps in the scale of 1: 50,000 and engineering geological maps in the scale of 1: 20,000 of different cities and town of the country. So far the GSB has completed about 35% of country's geological mapping and engineering geological mapping of seven cities and towns, among these the urban geological maps of Dhaka and Chittagong cities are most significant achievements. These maps are yet to be published. This paper describes the present status, prospects and types of geological or geo-environment data, maps and other information available to planners and developers. The means for optimum utilization of hard achieved geological and geotechnical data for rational utilization in the urban and infrastructure developments are proposed.

Bangladesh is one of the densely populated country of the world. There are various type of geological hazards in this small landmass which cause serious damage to the lives and property of the country every year. The geological hazards like floods, erosion, landslides, subsidence and earthquake are discussed in this paper. It is necessary to identify the geological aspects in mitigation of these hazards for an effective land use planning and development. The possible relationship between the hazards and geological processes are delineated in this paper.

2018

Rajshahi and Nawabgonj district occupies a portion of Barind Tract. Depositional environment and neo-tectonics of the area analyzed with the help of bore log data. About 80 no of bore logs were collected from BMDA and BWDB. Subsurface geological condition, their architectural elements as well as depositional environment was derived from those lithologs. The study area divided in to four informal units named Unit-A, Unit-B, Unit-C and Unit-D. Unit-D is further subdivided into two subunits as Subunit-1 and Subunit-2. Subunit-1 is being deposited during Recent time and Subunit-2 was deposited during Pleistocene period. Below this Unit-C, Unit-B and Unit-A is found which have been deposited during Mio-Pliocene period. The subsurface litho-succession was prepared from collected lithologs and architectural element analysis helps to understand the vertical and lateral distribution pattern of the sediments. The study area is tectonically still very active and signatures of neo-tectonic acti...

2020

The Bhuban Formation of the Surma Group of rocks is well exposed in the Kaptai to Baraichari road cut section, Sitapahar anticline, Kaptai, Chittagong Hill Tracts, Bangladesh. The main goal of the study is to delineate lithosequences, facies association, depositional model and interpret of different sub environment of the sedimentary deposits of the study area. Litho-stratigraphically the Middle Bhuban Member consists of mainly light gray to black laminated to thinly bedded shale, sandy shale and siltstone and the Upper Bhuban Member of yellowish brown and dark color sandstone, silty shale and black shale. The Lower Bhuban Member is not exposed in the investigated area. Based on texture and sedimentary structures, a total of six lithofacies have been identified such as turbidite sandstone (ST), lenticular laminated sandstone -siltstone-silty shale (Sll), ripple laminated sandstone-siltstone (Sr), wavy laminated sandstone-siltstone-silty shale (Sw), wavy laminated silty shale to shal...

Journal of Nepal Geological Society

The study illustrates the effect of tectonics, climate, and relative sea-level change on the depositional process of the Miocene Bhuban and Boka Bil Formation of Bengal Basin. Outcrop sediments of five transverse sections exposed along the axial zone of Bandarban anticline were studied. Twelve lithofacies such as Gm, Gms, Sm, ST, Sp, Sr, Sl, Sf, Sll, Fw, Fl and Fm have been identified within the successions and grouped into (i) turbidite generated, (ii) outer fan distal lobe basin plain and (iii) tide-influenced facies association. The analyses reveal that the Bhuban Formation was turbidite- generated that deposited below the continental shelf-slope environment. The Lower Bhuban Member consists of gray to brownish-gray calcareous sandstone with shale deposited under the channelized lobe of submarine fan. The Middle Bhuban Member dominated by black shale-siltstone deposited in distal turbidite lobe due to change the flow regime. The Upper Bhuban Member consists of yellow to yellowish...

Journal of Nepal Geological Society, 2015

The Barind Tract is an elevated Pleistocene Terraces (about 11-48 mamsl) in northwestern Bangladesh and is widely accepted Tract to have been evolved from tectonic upliftment and /or exists as an erosional geomorphic feature. Some part of the Barind Tract bears the characteristics of morphological origin but some areas are providing evidences of tectonic upliftment. The present study is an attempt to interpret the morphological characteristics of the rivers in the area and tried to unveiling the processes that are responsible for the evolution of the Tract. River morphology are interpreted from satellite images and field mapping and are used to relate neotectonic activities occurred in the area. The river forms U-shaped valleys in floodplain areas whereas these are V-shaped within the Barind Tract. The rivers and valleys on the Tract are also comparatively more straight, incised and entrenched, and rivers are tightly meandered, more localized, form paired and unpaired terraces, and ...

2020

A rock is a natural substance made up of solid crystals of various minerals that were fused into a solid lump together. The solid mineral material that is part of the earth's surface and other similar planets that is exposed on the surface or underlying the earth. There are three main rock groups: Igneous rocks, Sedimentary rocks, and Metamorphic rocks. Rocks are of great resource value like minerals, some directly, and some as mineral constituents. Nearly all types of building materials used to pave roads, floors, and house walls, or various other structures, including bridges, come from rocks. These rocks are found in countries all over the world. In this research, different rocks that are found in Bangladesh were collected and identified depending on their color, texture and grain size. This paper also deals with the properties and uses of these rocks.