Is there any significant brittle faulting on the eastern NPHM margin?

The eastern margin of the NPHM along the Indus section has previously been reported [Verplanck, 1986] as the site of a suite of large brittle faults, the Stak Fault Zone. Our observations along this section of the eastern margin indicate that brittle faults are of minor significance and are sparse in density, compared with the western margin along the Indus, and farther south along the western margin. One steep brittle fault with about 10m of gouge and near dip-slip displacement indicators is seen near the contact, of amphibolites of Ladakh and Indian cover metasediments, but otherwise the eastern margin appears as folded but otherwise unmodified MMT mylonites [Photo 1; Photo 3]. Farther south near the eastern margin, between Rama and Rupal/Churit Valleys, brittle faults with dominant dip-slip displacement indicators occur, but are thought from the modest density, and from the absence of a major fault at the Ladakh-Indian cover contact, to provide a minor contribution to overall NPHM vertical displacement. We conclude, concurring with and expanding observations of Treloar et al, 1991, that the eastern margin of the NPHM is largely an unmodified section through the Main Mantle Thrust, turned up by large-scale folding associated with the rise of the Nanga Parbat antiform.

Return to Abstract/Index