The timing of India–Asia collisionremains controversial but is importantto understanding the nature of strainaccommodation in Cenozoic Asia.The sediment record on each collidingmargin provides some of the bestconstraints on when initial contactoccurred. In a recent study Upadhyayet al. (2004) suggested that palyno-morphs eroded from sediments on theIndian passive margin were reworkedinto turbidites on the Asian activemargin well before the final collision.In this model palynomorphs weretransported across the Tethys andincorporated into a trench–subduc-tion complex on the Asian margin.However, geochemical, structural andsedimentary evidence indicates thatthe Asian margin was tectonicallyerosive prior to collision and that theforearc sedimentary rocks in questionaccumulated not in the trench, but asa volcanic debris apron on a subsidingforearc. The palynomorphs werelikely eroded from Asian sedimentaryrocks, similar to those now exposed inthe northern Karakoram.Geological settingThe Indus Suture Zone in Ladakh,India, preserves a well-exposed seriesof sedimentary rocks that were depos-ited before India–Asia collision withinthe forearc basins of two arc com-plexes, the oceanic Dras-Kohistan Arcand its successor the continental Tran-shimalayan Arc (Fig. 1; Reuber,1989). In a recent contribution toTerra Nova Upadhyay et al. (2004)presented palynological data from theNindam Formation of western Lada-kh and proposed that these demon-strated not only a Palaeocenedepositional age, but also that mater-ial eroded from the passive margin ofIndia was crossing the Tethys andbeing incorporated into a trench sub-duction complex prior to the collisionof India and Asia around 50–55 Ma.While the palynological data presen-ted is useful in providing additionalage control to the generally poorlydated sedimentary rocks of the IndusSuture Upadhyay et al.s preferredmodel, with its significant implicationsfor the dating of India–Asia collisionis not consistent with other constraintson the tectonic setting.The tectonic significance of theproposed model lies in the concept ofsedimentary material being carriedfrom India, and subsequently beingincorporated into a subduction accre-tionary complex on the Asian margin.If true this would mean that theappearance of sedimentary materialof Indian provenance on the Asianmargin could significantly pre-datefinal collision. Several factors indicatethat this pre-collisional transfer can-not have occurred and that a morelikely source for the Permian–Meso-zoic reworked palynomorphs are sedi-mentary rocks on the Asian margin,equivalent to those in the northernKarakoram (Pudsey, 1986; Gaetaniet al., 1990; Searle, 1991). Several linesof evidence show that the Asian fore-arc basin fill comes from Asia. Pal-aeocurrent indicators in the forearcNindam and the Jurutze Formationsshow flow from north to south, incon-sistent with derivation of materialfrom India (Clift et al., 2000, 2002a).Even if small amounts of reworkedmaterial were able to cross the Tethysand reach the trench associated withthe Transhimalayan Arc these materi-als would have been subducted andnot preserved. There is no evidence fora significant preserved accretionarycomplex associated with either theDras–Kohistan Arc or the Transhi-malayan Arc, or given what we knowof the geodynamics, would we expectthere to be. Although Robertson(2000) described a series of subduc-tion-related, tectonic me´langes in thesuture zone (e.g. Urtzi Me´lange), theirwidth of just a few hundred metresmeans they are not equivalent tocomplexes formed at modern activemargins in a state of net long-termgrowth, but rather could reflect shear-ing in a tectonically erosive setting.The Nindam Formation itself is notan accretionary complex. Robertsonand Degnan (1994) were the first tonote that the Nindam turbidite sand-stones do not show the penetrativedeformation associated with modernand ancient subduction complexes,but were deformed like the syn-colli-sional Indus Group, i.e. because ofHimalayan compression.While the volcanic rocks emplacedon the Asian active margin just priorto India–Asia collision show moreenriched chemistries than the pre-ceding oceanic Dras 1 Volcanic For-mation and its equivalents in Pakistan(Chalt Volcanic Group; Pettersonet al., 1991; Khan et al., 1997), theNd isotope and trace element datafrom the Dras 2 and Kardung Vol-canic Formations indicate very limitedsediment involvement in petrogenesis(