M.R.W. JOHNSON; Volume balance of erosional loss and sediment deposition related to Himalayan uplifts. Journal of the Geological Society ; 151 (2): 217–220. doi: https://doi.org/10.1144/gsjgs.151.2.0217
The volume of sediment in the foreland basins, deltas and fans which are a consequence of the collision of India and Asia appears to require the removal of a vertical section c.35km high if the sediments were entirely derived from the Himalaya. It is argued that this is implausible and that it is likely that the Himalayan hinterland (e.g. Karakoram and Tibet) was an important source of sediment prior to c. 20 Ma when significant Himalayan uplift commenced.