How are alluvial soils formed ? How is Bangar alluvium different from Khadar?

Alluvial soils are formed by the deposition of materials brought down by the rivers. This process of deposition continues for millions of years leading to accumulation of soil into thick layers.
These have been deposited by three important Himalayan rivers namely the Indus, Ganga and the Brahmaputra.
Differences :
(i) These are the new alluvium deposited recently.
(ii) These are fine and fertile.
(iii) These are found near the river in the flood plains and deltas.
(iv) These are sandy and light in colour.
(i) These are the old alluvium deposited in the recent past.
(ii) These are coarse and less fertile. (presence of ‘Kankar’ nodules)
(iii) These are found away from the river especially along the foothills.
(iv) These are clayey and dark in colour.