HR: 10:20h
AN: T52A-01 INVITED     [Abstracts]
TI: Strategies to overcome non-uniqueness of detrital age data from Himalayan sediments.
AU: * Carter, A
EM: a.carter@ucl.ac.uk
AF: Birkbeck College, School of Earth Sciences University and Birkbeck College, Gower Street, London, WC1E 6BT United Kingdom
AU: Foster, G
EM: g.l.foster@bristol.ac.uk
AF: University of Bristol, Department of Earth Sciences, Queens Road, Bristol, BS8 1RJ United Kingdom
AB: Studies directed at using the detrital record to reconstruct growth history of the Himalayas are made difficult by the relatively homogeneous geology along strike. High temperature methods such as zircon U-Pb dating can distinguish between Tethyan, Greater or Lesser Himalayan sources but generally lack more site specific information. Lower temperature dating methods are better suited to detect localised differences in ages caused by active tectonics, high-relief and variable climate but can also suffer from non uniqueness in detrital age. A case in point is the similarity between fission-track (FT) bedrock ages in the Namche Barwa syntaxis and Holocene detrital FT ages obtained from delta sediments at Barasat, near Kolkata. A syntaxial source for the Holocene samples is in keeping with the observation by Eduardo Garzanti that sites of focused erosion, such as Namche Barwa contribute a disproportionate amount of the total sediment flux reaching the Bay of Bengal. However similar bedrock ages also occur within the Ganges drainages. For example: modern river sediment from the Trishuli River record identical FT age modes to those from Namche Barwa. More robust evidence is required to distinguish source areas. We discuss how the combination of several thermochronometers and geochemical signatures (Hf, Sr and Pb) measured on the same grain, may provide the best opportunity to obtain more specific provenance information.
DE: 9320 Asia
DE: 8102 Continental contractional orogenic belts
DE: 4825 Geochemistry
DE: 5475 Tectonics (8149)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting