3. Recession of the Sea

In the opinion of Blandford, during the Eocene Period, Peninsular India was joined together with Africa. During that period, there was one sea extending from Assam Valley to the Irrawaddy river (Myanmar) in the east and another from Iran and Baluchistan to Ladakh (Indus Valley) in the west. During the last part of the Eocene Period, arms of the Western Sea extended up to Punjab. Due to the rise of the Himalayas during the Miocene Period, these seas started receding by gradual deposits of sediments from the Himalayan rivers. After a prolonged period of sedimentation and subsidence, these gulfs (Gulf of Sind in the west and the Eastern Gulf up to the Shillong Plateau) were filled up, resulting in the formation of the Northern Plains of India.

The evidences cited in favour of the recession of the sea include: (i) the occurrence of limestone rocks in Kumaun-Garhwal region of Uttarakhand, (ii) the presence of saline water lakes in Rajasthan, (iii) the joining of the islands of the Gulf of Kachchh with the mainland, (iv) the seaw ard extension of the Sundarban Delta, (v) the emergence of new islands near Bangladesh coast, and (vi) the presence of marine fossils in the sediments of the Northern Plains of India. The theory, however, fails to give convincing arguments so far as the region of the central portion of the plain is concerned.