Tectonics of the Himalaya and southern Tibet from two perspectives

The Himalaya and Tibet provide an unparalleled opportunity to examine the c omplex ways in which continents respond to collisional orogenesis, This pap er is an attempt to synthesize the known geology of this orogenic system, w ith special attention paid to the tectonic evolution of the Himalaya and so uthernmost Tibet since India-Eurasia collision at ca, 50 Ma. Two alternativ e perspectives are developed, The first is largely historical. It includes brief (and necessarily subjective) reviews of the tectonic stratigraphy, th e structural geology, and metamorphic geology of the Himalaya. The second f ocuses on the processes that dictate the behavior of the orogenic system to day. It is argued that these processes have not changed substantially over the Miocene-Holocene interval. which suggests that the orogen has achieved a quasi-steady state. This condition implies a rough balance between plate- tectonic processes that lead to the accumulation of energy in the orogen an d many other processes (e.g., erosion of the Himalayan front and the latera l flow of the middle and low er crust of Tibet) that lead to the dissipatio n of energy, The tectonics of the Himalaya and Tibet are thus intimately re lated; the Himalaya might have evolved very differently had the Tibetan Pla teau never have formed.