HR: 10:35h
AN: T52A-02    [Abstracts]
TI: Provenance of early foreland basin sediments, Nepal: constraints to the timing and diachroneity of early Himalayan orogenesis.
AU: * Najman, Y
EM: y.najman@lancs.ac.uk
AF: Dept Environmental Science, Lancaster University, Lancaster, LA1 4YQ United Kingdom
AU: DeCelles, P
EM: decelles@geo.arizona.edu
AF: Dept of Geosciences, University of Arizona, Tucson, AZ 85721 United States
AU: Gehrels, G
EM: gehrels@geo.arizona.edu
AF: Dept of Geosciences, University of Arizona, Tucson, AZ 85721 United States
AU: Carter, A
EM: a.carter@ucl.ac.uk
AF: School of Earth Sciences, University and Birkbeck College, Gower St., London, WC1E 6BT United Kingdom
AU: Martin, A
EM: amartin@geo.arizona.edu
AF: Dept of Geosciences, University of Arizona, Tucson, AZ 85721 United States
AU: Oliver, G
EM: gjho@st-andrews.ac.uk
AF: School of Geography and Geosciences, The University, , St. Andrews, KY16 9AL United Kingdom
AU: Garzanti, E
EM: eduardo.garzanti@unimib.it
AF: Dip di Scienza della Terra, University Milan-Bicocca, Via Mangiagalli 34, Milan, 2013 Italy
AB: In contrast to Eocene Himalayan foreland basin sediments in India and Pakistan, co-eval sediments of the Bhainskati Formation in Nepal contain no petrographic evidence for orogenic input. Such data have been used as evidence to promote models of diachroneity of India-Asia collision. In this paper we provide evidence of orogenic input into the Eocene foreland basin sediments of Nepal, from U-Pb and fission track analyses of detrital zircons. Our data removes the evidence for significant diachroneity of collision as pertains to provenance data in the sediment record in Nepal, and brings the sediment record into better agreement with ages of early thrusting and metamorphism in the orogen. We also use our detrital fission track data to bolster previous age determinations of the overlying Dumri Formation, confirming the basin-wide occurrence of a major unconformity. Comparison of our fission-track dataset with that from the co-eval Dagshai Formation more than 500 kms along strike in India suggests that there is no evidence of significant diachroneity in early stages of exhumation of the orogen.
DE: 8102 Continental contractional orogenic belts
DE: 8105 Continental margins and sedimentary basins
DE: 8110 Continental tectonics--general (0905)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting