GEOLOGICAL STRUCTURE OF BIHAR B A II , PAPER 3, UNIT - 5 BY DR BHAWANA NIGAM, DEPT OF GEOGRAPHY, A N COLLEGE, PATLIPUTRA UNIVERSITY, PATNA. INTRODUCTION GEOLOGICAL TIME SCALE THE FORMATION OF BIHAR • The structure of Bihar is different from its neighbouring states and the formation took place at different times. • It is closely related with the upheaval of Himalayan Mountains. • It consist of vast alluvial plain, • small hilly region in the north west portion known as Someshwar hills and • the southern most portion is made of Kaimur range, in the district of Gaya, Nawada, Munger, and Banka closely associated with Chotanagpur region. GEOLOGICAL DIVISION OF BIHAR • Based on above discussion the state can be broadly divided into • 1) SOMESHWAER HILLY REGION • 2) VAST ALLUVIAL PLAIN • 3) SOUTHERN MOST HILLY REGION. SOMESHWAR HILLY REGION • Located in NW part of the state and it consist of hills and dun range. • It is part of Indo-Gangetic plain. • Geologist believes that it has origin from the Geosyncline of Himalayas. Later it was subsided due to overload of sediments deposited by river. • During the second upliftment of Himalayan mountains it was developed as hilly area. • This is the border area ; where peninsular India joined with northern Asia, therefore consist of depressions and ridges. • This area has undergone massive down wrapping and leads to crustal instability in NW part of Bihar. ALLUVIAL PLAIN AREA OF BIHAR. • It consist of North Bihar and South Bihar Plain. This plain area has similar geological formation like those of Indo-Gangetic plain. • North Bihar Plain has alluvial deposition by perineal rivers coming from the Himalayas and has unique Geological Formation. • The plain has distinctive sediments characterised by kankar, nodules, calcareous beds, in the areas of E & W Champaran, Sitamarhi and Sheohar Districts; it also include clay and mud in Ganga and Gandak district. • South Bihar Plain has deposition from the rivers coming from Chotanagpur plain and Madhya Pradesh. The plain has Khadar deposition having older alluvium which consist of clay and sand. • The SE portion of Bihar has silica deposition from Chotanagpur region.. SOTHERN HILLY REGION • The southern part of Bihar are geological formation of Complex nature having bare rocks of early geological period. • This region include Kaimur hilly region, the hills of Gaya, Navada , Nalanda, Kiul, Munger, and Banka etc. • The rock consist of sandstone, quartzite, limestone, dolomite, and shales. • The hilly terrain of Gaya, Nalanda, Nawada, etc. are the outliers of Chotanagpur plateau. REFERENCE • Sinha V.P et.all – Bihar land, people and economy. • National digital library • Google scholar. • Thanks..