Middle Miocene denudation of the Higher Himalayan Crystallines revealed by chemical composition of detrital garnets from the Siwalik foreland basin sediments, western and central Nepal

•Provenance study reveals that the Higher Himalayan Crystallines (HHC) supplied detritus to the Lower Siwalik sub-group.•Detrital staurolite and Mg-rich garnets appeared in the Lower Siwalik sub-group at 13–10 Ma in western and central Nepal.•Regional-scale denudation of the HHC rocks accompanied by an out-of-sequence thrust activity occurred at 13–10 Ma.•Denudation and exposure of the HHC rock progressed from the west toward east in the Central Himalaya.