Integrated tectonostratigraphic analysis of the Himalaya and implications for its tectonic reconstruction P.M. Myrow a; Ã , N.C. Hughes b , T.S. Paulsen c , I.S. Williams d , S.K. Parcha e , K.R. Thompson a , S.A. Bowring f , S.-C. Peng g , A.D. Ahluwalia h a Department of Geology, Colorado College, Colorado Springs, CO 80903, USA b Department of Earth Sciences, University of California, Riverside, CA 92521, USA c Department of Geology, University of Wisconsin, Oshkosh, WI 54901, USA d Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia e Wadia Institute of Himalayan Geology, Dehra Dun, Uttranchal 248001, India f Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA g Nanjing Institute of Geology and Paleontology, Nanjing 210008, PR China h Department of Geology, Panjab University, Chandigarh 160014, India Received in revised form 23 March 2003; accepted 5 May 2003 Abstract TheisotopegeochronologyofisochronouslydepositedCambrianstratafromdifferenttectonostratigraphiczonesof the Himalaya confirms new stratigraphic, sedimentological, and faunal evidence indicating that the Himalaya was a single continental margin prior to collision of India with Asia. Lesser, Greater, and Tethyan Himalaya represent proximal to distal parts of a passive continental margin that has been subsequently deformed during Cenozoic collision of India with Asia. Detrital zircon and neodymium isotopic data presented herein discount the prevailing myth that the Lesser Himalaya has a unique geochronologic and geochemical signature that is broadly applicable to modeling the uplift history of the Himalaya. The conclusion that all pre-Permian Lesser Himalaya strata lack young detrital zircons that are present in the Greater and Tethyan Himalaya underpins previous arguments that the Main CentralThrustformsafundamentalcrustalboundarythatseparatestheIndiancratonfromanaccretedterranetothe north.ThesuppositionthatHimalayanlithotectoniczonesdifferindetritalzirconagepopulationshasalsobeenused to reconstruct the unroofing history of the Himalaya during foreland basin development in the Cenozoic. Our data conflictwiththeunderlyingassumptionsimplicitinthesestudiesinthatsamplesofsimilardepositionalagefromboth the Lesser and Tethyan Himalaya contain detrital zircons with similar age spectra. Similarities between the Kathmandu Complex and the Tethyan Himalaya support stratigraphic continuity between the former and either age- equivalent Greater Himalayan protolith or the Tethyan. Assuming that the complex rooted along the Main Central Thrust, these strata would simply have escaped intense metamorphism during Cenozoic tectonism. Alternatively, the complexmayrepresentapartoftheTethyanHimalayathatwasemplacedduringanearlystageofmovementalonga south-directed thrust fault located near the present-day structural position of the South Tibetan Fault System. ß 2003 Elsevier Science B.V. All rights reserved. 0012-821X/03/$ ^ see front matter ß 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0012-821X(03)00280-2 * Corresponding author. Tel.: +1-719-389-6790; Fax: +1-719-389-6910. E-mail address: pmyrow@coloradocollege.edu (P.M. Myrow). Earth and Planetary Science Letters 212 (2003) 433^441 R Available online at www.sciencedirect.com www.elsevier.com/locate/epsl