Madhupur Clay highly weathered and deeply oxidized reddish brown deposit exposed in the Madhupur, Barind and Lalmai Hill areas. Madhupur Clay represents several north-south elongated pleistocene terraces, highly dissected during the Late Pleistocene climatic episodes. Madhupur Clay makes beautiful scenery of the lalmai hills, Madhupur and Varendra areas. All the ancient civilisations, flourished at mahasthangarh [Mahasthangad], paharpur and mainamati are located in the Madhupur Clay zones. The Madhupur Clay had played a distinct role in the civil engineering works, art and culture of the ancient Bengal.
These deposits are extensively exposed in Vawal and Madhupur Garhs of Dhaka, Mymensingh and Tangail districts. In the Barind area, these deposits are exposed in the Greater Rajshahi and Bogra districts. In Comilla district, Madhupur Clay capped almost all the hilltops of Lalmai Hills. In Madhupur and Barind areas, these deposits form some north-south elongated landmasses slightly elevated from the adjacent floodplain. These clays are known as the Madhupur Clay Formation. The clay contains halloysite and illite and represents relict palaeosol. Nowadays, in Madhupur and Barind areas, this clay is called Madhupur and Barind formations respectively. Stratigraphically Madhupur Clay has been subdivided into three members: upper one is called Dhaka Clay Member, represented by highly weathered deep clayey materials composed of ferruginous nodules, pipestems and manganese spots. The middle member is called Mirpur Silty-clay Member and the lower one is called the Bhaluka Sand Member, and is represented by yellowish brown highly micaceous sand containing primary sedimentary structures, such as, cross bedding, ripple marks etc. Palaeomagnetical studies showed normal polarity of this formation and has been correlated with the Jaramillo Event of Matuyama Reversed Polarity Epoch. It means that the Clay has the age of about 0.97 to 0.90 million years. The depositional environment of the Madhupur Clay is fluvial. [Md Hussain Monsur]