- journal_title：Geology
- Contributor：Andrew J. Meigs ; Douglas W. Burbank ; Richard A. Beck
- Publisher：Geological Society of America
- Date：1995-
- Format：text/html
- Language：en
- Identifier：10.1130/0091-7613(1995)023<0423:MLMMFO>2.3.CO;2
- journal_abbrev：Geology
- issn：0091-7613
- volume：23
- issue：5
- firstpage：423
Three independent data sets from northwestern India and Pakistan suggest initial displacement along >1000 km of the Main Boundary thrust prior to 10 Ma, at least 5 m.y. earlier than previously reported. Regionally extensive changes in the depositional characteristics and rates of the foreland-basin fill between 11 and 9.5 Ma are interpreted to reflect new hinterland loading due to the formation of the Main Boundary thrust. Sediment-accumulation rates, sandstone-siltstone ratios, and thickness and amalgamation of individual sandstone bodies all substantially increase after 11 Ma in well-dated stratigraphic sections from Pakistan to Nepal across the Indo-Gangetic foreland basin. In the Himachal Pradesh reentrant of northwestern India, a newly discovered 8.7 Ma conglomerate derived from the hanging wall of the Main Boundary thrust indicates that source-area uplift and denudation must have occurred prior to 9 Ma and probably prior to 10 Ma, assuming a gravel progradation rate of 3 cm/yr. Three apatite fission-track ages from structures at the leading edge of the Main Boundary thrust in the Kohat region of northwest Pakistan indicate that rapid cooling below ∼105° C between 8 and 10 Ma followed bedrock uplift and erosion that began ∼1–2 m.y. earlier. These data indicate that the Main Boundary thrust in the western Himalaya formed synchronously along strike in the middle-late Miocene, has a displacement rate of ∼10 mm/yr, and has a displacement history that is coeval with late displacement on the Main Central thrust.