Indo Brahma theory and shivalik river

1. Initial River Formation: During the Miocene period, approximately 5-24 million years ago, a significant river known as the Shiwalik or Indo-Brahma traversed the entire length of the Himalayas, flowing from Assam to Punjab. This river had a massive longitudinal extent and discharged into the Gulf of Sind near lower Punjab.

2. Sedimentary Evidence: The continuity of the Shiwalik and the presence of lacustrine origin and alluvial deposits, including sands, silt, clay, boulders, and conglomerates, provide geological evidence supporting the existence of this ancient river.

3. Fragmentation into Three Drainage Systems:

- Indus Drainage System: In the western part of the Himalayas, the Indo-Brahma river eventually fragmented, forming the Indus River and its five main tributaries. This fragmentation likely occurred due to geological events such as the Pleistocene upheaval in the western Himalayas.

- Ganga Drainage System: In the central part of the Himalayas, the Indo-Brahma river gave rise to the Ganga River and its Himalayan tributaries. The uplift of the Potwar Plateau, also known as the Delhi Ridge, acted as a watershed dividing the Indus and Ganga drainage systems.

- Brahmaputra Drainage System: In the eastern part of the Himalayas, the stretch of the Indo-Brahma river in Assam transformed into the Brahmaputra River and its Himalayan tributaries. The downthrusting of the Malda gap area between the Rajmahal hills and the Meghalaya plateau during the mid-Pleistocene period diverted the flow of the Ganga and Brahmaputra systems towards the Bay of Bengal.

4. Geological Processes: The Pleistocene upheaval in the western Himalayas, including the uplift of the Potwar Plateau, likely played a significant role in the fragmentation of the Indo-Brahma river. Similarly, the downward movement of the Malda gap area redirected the flow of rivers towards the Bay of Bengal, reshaping the drainage pattern in the eastern part of the Himalayas.

These geological processes, including uplifts, downthrusting, and watershed formations, have contributed to the complex and diverse drainage system of the Himalayas, shaping the landscape and influencing the distribution of rivers and tributaries in the region.

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