Constraints on brittle field exhumation of the Everest-Makalu section of the Greater Himalayan Sequence: Implications for models of crustal flow

摘要: [1] New apatite and zircon fission track (FT) data from the summit slopes of Everest along Barun, Arun, Dudh Kosi, Kangshung valleys that drain Makalu massifs cover a vertical sample transect almost 8000 m Eastern Nepal Greater Himalayan Sequence (GHS). Apatite FT ages range 0.9 ± 0.3 Ma to 3.1 ± 0.3 Ma in GHS with increasing systematically elevation. Series Ordovician limestones are much older, up 30.5 ± 5.1 Ma. Zircon 3.8 ± 0.4 Ma 16.3 ± 0.8 Ma. The brittle exhumation rates calculated these show was exhumed, since ∼9 Ma, at an average rate 1.0 ± 0.2 mm/a. Pliocene higher 1.7 ± 0.3 mm/a. These values not significantly different estimate ductile 1.8 mm/a recorded by metamorphic minerals undergoing decompression between 18.7 15.6 Ma but well below (up 10 mm/a) used thermomechanical models for channel flow GHS. If representative will therefore require further ‘tuning’. Higher have also been observed other parts Himalaya points regional cause, likely increased erosion due onset late Pliocene–Pleistocene glaciation high Himalaya.