Late Cenozoic environmental changes and uplift on the northern side of the central Himalaya: a reappraisal from field data

The extreme view that uplift of the Tibetan Plateau and the adjacent Himalayan Range occurred mainly during the Quaternary cannot be further sustained, as discussed in the light of available field data (palaeobiogeography, sedimentary environments and tectonic evidence). Comparison with other independent sources, such as the loess records of central China and data on the post-orogenic sedimentation and geochronology of the Himalayan and South Asian oceanic fans, shows that the Tibetan Plateau certainly reached an elevation close to its present one before the climatic changes of the Quaternary. As such, this elevated Himalaya-Tibet ensemble was probably one of the major causes of the Late Tertiary general cooling of the northern hemisphere, as suggested by global modelling of climate. Palaeoenvironmental changes observed during the Quaternary were certainly governed by orbital parameters: yet, they were also regionally influenced by both the uplift of the Greater Himalaya with respect to Tibet, and by the disruption of the Northern Himalaya and South Tibet into horsts and grabens. Uncertainty still surrounds the periods during which critical elevations were achieved to induce both the monsoon circulation and E-W extension.