the closing of tethys and the tectonics of the himalaya recent geological and geophysical data from southern tibet allow refinement of models for the closing of southern neo tethys and formation of the himalaya shelf sediments of the indian passive continental margin which pass northward into deep sea tethyan sediments of the indus tsangpo suture zone were deposited in the late cretaceous an andean type margin with a 2 500 km long trans himalayan kohistan ladakh gangdese granitoid batholith formed parallel to the southern margin of the lhasa block together with extensive andesites rhyolites and ignimbrites lingzizong formation the southern part of the lhasa block was uplifted deformed and eroded between the cenomanian and the eocene in the western himalaya the kohistan island arc became accreted to the northern plate at this time the northern part of the lhasa block was affected by jurassic metamorphism and plutonism associated with the mid jurassic closure of the bangong nujiang suture zone to the north the timing of collision between the two continental plates ca 50 40 ma marking the closing of tethys is shown by 1 the change from marine flysch like to continental molasse like sedimentation in the indus tsangpo suture zone 2 the end of gangdese i type granitoid injection 3 eocene s type anatectic granites and migmatites in the lhasa block and 4 the start of compressional tectonics in the tibetan tethys and indus tsangpo suture zone south facing folds south directed thrusts after the eocene closure of tethys deformation spread southward across the tibetan tethys zone to the high himalaya deep crustal thrusting barrovian metamorphism migmatization and generation of oligocene miocene leucogranites were accompanied by south verging recumbent nappes inverting metamorphic isograds and by south directed intracontinental shear zones associated with the main central thrust continued convergence in the late tertiary resulted in large scale north directed backthrusting along the indus tsangpo suture zone more than 500 km shortening is recorded in the foreland thrust zones of the indian plate south of the suture and 150 km shortening is recorded across the indian shelf zanskar range and the indus suture in ladakh there was also large scale shortening of the karakoram and tibetan microplates north of the suture as much as 1 000 km shortening occurred in tibet the more recent deformation however involved the spreading of this thickened crust and the lateral motion of the tibetan block along major approximately east west trending strike slip fault zones

mesozoic neo tethyan pre orogenic deep marine sediments along the indus yarlung suture himalaya shelf forereef and basin margin slope olistoliths exotic blocks of limestone of permian jurassic age are tectonically juxtaposed within the triassic to eocene age pre orogenic deep abyssal plain turbidites of the lamayuru the pre collision tectonic setting and depositional environment of the limestone olistoliths can be reconstructed from within the neighbouring zanskar range the disorganized ophiolitic melange zone an association of different tectonic rock slivers of jurassic eocene age is tectonically underlain by the overthrusted lamayuru formation and tectonically overlain by the nindam formation tectonic slivers of late jurassic early cretaceous age red radiolarian cherts represent a characteristic lithotectonic unit of the ophiolitic melange zone those occurring near the contact zone with the lamayuru formation were deposited within the neo tethyan deep ocean floor of the indian passive margin below the carbonate compensation depth these tectonic slivers accumulated along the northern margin of the indus yarlung suture zone of the ladakh indian himalaya during subduction accretion associated with the initial convergence of the indian plate beneath the eurasian plate

earthquake induced soft sediment deformation in the lower shyok river valley northern ladakh india abstract soft sediment deformation structures occur in the 150 m thick pliocene quaternary fluvio lacustrine sediments exposed around the khalsar and tirit areas in the lower shyok river valley northern ladakh and eastern karakoram india these structures vary in morphology and pattern and occur at different stratigraphic horizons they satisfy the criteria for attributing them to seismic events and it is proposed that these structures were formed as a result of earthquake induced liquefaction the deformation structures are thus interpreted to represent pre historic seismic events which occurred up to 5 ma ago and were associated with tectonic activity along the karakoram fault

sedimentology petrography and tectonic significance of the shelf flysch and molasse clastic deposits across the indus suture zone ladakh nw india abstract in the ladakh area of india a passive triassic to lower cretaceous continental margin is indicated by indian shield derived clastics on the shelf and atlantic type turbidites off the continental margin mid cretaceous initiation of ocean closing is reflected in pacific type flysch and associated island are volcanics which were initially emplaced over the northern indian continental margin in late cretaceous times resulting in the formation of a fore deep in which flysch and minor continental molasse accumulated briefly during the late cretaceous these transient uplifts were however rapidly destroyed for by the latest cretaceous to latest palaeocene uniform carbonate sediments were being laid down over the area with the early eocene the development of a second fore deep this time filled with very thick flysch and molasse sediment indicates a major uplift of the northern indian margin which we attribute to the development of an andean type magmatic arc on the northern edge of the indian plate uplift and molasse sedimentation in this fore deep continued through the oligocene and miocene when the collision of india and asia caused extensive deformation of all the sequences and the shift of molasse sedimentation southwards to the himalaya foothills and indo gangetic plain

the xigaze forearc basin evolution and facies architecture cretaceous tibet abstract the mid cretaceous to eocene flysch deposits of the xigaze forearc basin in southern tibet were investigated in a 120 km segment along the indus yarlung suture zone the basin evolved south of the magmatic arc gangdise belt of the lhasa block on top of trapped oceanic or transitional crust remnants of shelf carbonates are preserved along the northern edge of the basin the mapped segment was shortened by about 65 metamorphism reached low grade conditions along the northern margin of the basin the flysch sequence reaches a thickness of at least 5 km and consists to a large degree of volcaniclastic andesitic to dacitic material shed from the magmatic arc gangdise belt particularly in the western part of the study area plutonic and sedimentary rocks from deep erosion levels and or more distal sources contributed to the basin fill rivers from the lhasa block acted as point sources and fed five major deep sea channel systems turbidity currents in the channels were directed towards the growing accretionary wedge of the subduction zone thus indicating that the basin was continuously filled up to outer ridge level and gradually shallowing the forearc flysch is subdivided into at least three megasequences which begin with wide up to several km incised 10 to 50 m coarse grained channel fills and their associated fan deposits the upper parts of the megasequences contain hemipelagic dark shales and marls deposited above the calcite compensation depth lateral channel migration channel lobe switching but also volcanic pulses generated a predominantly fining upward high frequency cyclicity after continental collision the marine sedimentation in the forearc basin was replaced by fluvial deposits of the eocene oligocene qiuwu formation which is time equivalent to the kailas and indus molasses farther west and rich in coarse gravel derived from the gangdise belt both forearc flysch and qiuwu formation were deformed simultaneously during the miocene we assume that the molasse type qiuwu formation represents the final continental facies of the forearc basin filling

sedimentology and tectonic implications of the lamayuru complex deep water facies of the indian passive margin indus suture zone ladakh himalaya

zircon u pb and hf isotopic constraints on the onset time of india asia collision the time of initial collision between india and asia has been extremely controversial despite the fact that it is vital to constraining the orogenesis and subsequent evolution of the himalayas and tibetan plateau here we report u pb and hf isotope analysis of detrital zircons from two principal foreland basins that is the sangdanlin and gyangze basins respectively in the western and central parts of southern tibet our data suggest that asian derived clastic sediments started contributing to sedimentation on the indian continental margin earlier than generally thought at 60 ma in both basins near the yarlung zangbo suture zone in southern tibet no evidence for the existence of an intra oceanic arc within the neotethys is observed we conclude that 60 ma can be used to constrain the onset time of the india asia collision at least in central tibet after this initial collision closure of the neotethys propagated both westward and eastward with the final closure occurring at 50 and 45 ma in northwestern and eastern himalayas respectively our conclusion differs significantly from the previous view that the india asia collision may have started in northwestern himalaya and propagated eastward with diachronous suturing

pyroclastic activity at home plate in gusev crater mars home plate is a layered plateau in gusev crater on mars it is composed of clastic rocks of moderately altered alkali basalt composition enriched in some highly volatile elements a coarse grained lower unit lies under a finer grained upper unit textural observations indicate that the lower strata were emplaced in an explosive event and geochemical considerations favor an explosive volcanic origin over an impact origin the lower unit likely represents accumulation of pyroclastic materials whereas the upper unit may represent eolian reworking of the same pyroclastic materials

mesozoic deep water slope rise sedimentation and volcanism along the north indian passive margin evidence from the karamba complex indus suture zone western ladakh himalaya abstract mesozoic deep water sedimentary and basic volcanogenic rocks defined as the karamba complex are exposed within the indus suture zone of western ladakh n india the karamba complex originated as part of the north indian passive margin in its entirety and does not include exotic melange or accreted oceanic units as recently suggested the complex preserves younger more distal equivalents relative to more proximal deep water slope lamayuru complex and shelf zanskar successions of the north indian passive margin the karamba complex is mainly inverted youngs to the nnw and includes many outcrop scale folds that face nnw the complex was initially emplaced onto the zanskar shelf as three main thrust slices probably in the latest cretaceous and later inverted faulted and sheared during mid late tertiary nw backthrusting that accompanied uplift of the high himalaya sedimentation in the karamba complex began in the mid late triassic with mainly siliciclastic turbidites derived from the indian basement together with redeposited limestones and minor basic volcanics mixed radiolarian sediments siliciclastic turbidites and redeposited shelf derived calciturbidites accumulated in early mid jurassic accompanied by eruption of alkaline volcanic rocks mainly in the mid jurassic the probable cause of the jurassic volcanism was a pulse of crustal extension along the continent ocean transition zone triggered by late stage rifting of india from gondwana as a precursor to its northward drift quartzose sandstone turbidites accumulated on the upper slope in the early cretaceous whereas sedimentation on the lower slope rise was pelagic marked by depositional hiatuses and sediment redeposition during the late cretaceous a switch to mainly calcareous pelagic deposition took place interspersed with radiolarian accumulation on the lower slope rise initial thrust emplacement onto the zanskar shelf in the latest cretaceous is suggested by the absence of post upper cretaceous sediments within the karamba complex

shyok suture zone n pakistan late mesozoic tertiary evolution of a critical suture separating the oceanic ladakh arc from the asian continental margin abstract the shyok suture zone northern suture of north pakistan is an important cretaceous tertiary suture separating the asian continent karakoram from the cretaceous kohistan ladakh oceanic arc to the south in previously published interpretations the shyok suture zone marks either the site of subduction of a wide tethyan ocean or represents an early cretaceous intra continental marginal basin along the southern margin of asia to shed light on alternative hypotheses a sedimentological structural and igneous geochemical study was made of a well exposed traverse in north pakistan in the skardu area baltistan to the south of the shyok suture zone in this area is the ladakh arc and its late cretaceous mainly volcanogenic sedimentary cover burje la formation the shyok suture zone extends northwards ca 30 km to the late tertiary main karakoram thrust that transported asian mainly high grade metamorphic rocks southwards over the suture zone the shyok suture zone is dominated by four contrasting units separated by thrusts as follows 1 the lowermost askore amphibolite is mainly amphibolite facies meta basites and turbiditic meta sediments interpreted as early marginal basin rift products or trapped tethyan oceanic crust metamorphosed during later arc rifting 2 the overlying pakora formation is a very thick ca 7 km in outcrop succession of greenschist facies volcaniclastic sandstones redeposited limestones and subordinate basaltic andesitic extrusives and flow breccias of at least partly early cretaceous age the pakora formation lacks terrigenous continental detritus and is interpreted as a proximal base of slope apron related to rifting of the oceanic ladakh arc 3 the tectonic melange reconnaissance further east north of the shyok river indicates the presence of redeposited volcaniclastic sediments and thick acid tuffs derived from nearby volcanic centres presumed to lie within the ladakh arc in addition comparison with lower cretaceous clastic sediments maium unit within the northern suture zone west of the nanga parbat syntaxis hunza river reveals notable differences including the presence of terrigenous quartz rich conglomerates serpentinite debris flow deposits and a contrasting structural history the shyok suture zone in the skardu area is interpreted to preserve the remnants of a rifted oceanic back arc basin and components of the asian continental margin in the west hunza river a mixed volcanogenic and terrigenous succession maium unit is interpreted to record syn deformational infilling of a remnant back arc basin foreland basin prior to suturing of the kohistan arc with asia 75 90 ma

palynological evidence for the palaeocene evolution of the forearc basin indus suture zone ladakh india the discovery of permian mesozoic and palaeocene palynomorphs from the nindam forearc basin exposed along the indus suture zone in ladakh is reported the palynomorphs are from volcanogenic sandstones and are poorly preserved distorted and show the effects of abrasion striation marks the frequent occurrence of proxapertites indicates the assemblage is at least palaeocene in age the palaeocene palynomorphs and sediments were transported to the nindam trough from nearby elevated landward regions islands these palaeocene provenance areas were characterized by an estuarine nearshore tropical warm humid environment and were situated at equatorial palaeolatitudes however the occurrence of permian and mesozoic palynomorphs in the assemblage indicates that the late palaeozoic and mesozoic tethyan sedimentary rocks exposed along the northern margin of the indian plate were redeposited into the tectonically active cretaceous palaeocene trench subduction complex that existed between the indian and the asian plates until the collision took place at 50 60 ma

the dras arc complex lithofacies and reconstruction of a late cretaceous oceanic volcanic arc in the indus suture zone ladakh himalaya abstract the purpose of this paper is to give an integrated description and interpretation of mainly volcaniclastic sediments related to excellently exposed oceanic volcanic arc successions in the ladakh himalayas the mainly late cretaceous aptian paleocene dras arc complex in the indus suture zone n india is reconstructed as an oceanic arc passing southwards into a proximal to distal forearc apron the arc complex comprises three structural units from west to east these are the suru unit the naktul unit and the nindam formation the suru unit and the naktul unit are unconformably underlain by dissected late jurassic oceanic crust and mantle the suru unit preserves the interior of the arc and is divided into dras 1 and dras 2 sub units the dras 1 sub unit of mid late cretaceous age was intruded by arc plutonics deformed then unconformably overlain by the poorly dated dras 2 sub unit lower tertiary the dras 1 sub unit comprises arc extrusives volcaniclastic and tuffaceous sedimentary rocks and mainly redeposited shallow water limestones the dras 2 sub unit is dominated by coarse volcaniclastics and lava flows passing up into rhythmically layered acidic extrusives with interbedded turbiditic siltstones and siliceous pelagic limestones further east the naktul unit is mainly clastic with large volumes of massive volcaniclastic talus thick bedded debris flows volcaniclastic turbidites and reworked shallow water carbonates pillowed extrusives and ribbon radiolarites are present mainly low in the succession in some areas while pelagic carbonates are abundant near the top the naktul unit is interpreted as a proximal forearc apron the nindam formation in the east is dominated by deep water volcaniclastic turbidites tuffaceous sediments and pelagic carbonates with subordinate debris flows and is interpreted as a distal deep water forearc succession cyclical alternations of mainly volcaniclastics and pelagic carbonates in the nindam formation are thought to reflect relative sea level changes of tectono magmatic and or global eustatic origin the oceanic dras arc complex formed within neotethys in the mid late cretaceous above an assumed northward dipping subduction zone around 79 ma campanian the oceanic arc underwent collisional deformation possibly related to accretion to the trans himalaya ladakh block and or the southern margin of eurasia to form an andean type active continental margin the suru unit in the west dras 1 sub unit was deformed then overlain by the mainly acidic dras 2 sub unit however there is no direct evidence that the nindam formation in the east was deformed until the early eocene when final collision of india and eurasia took place with southward thrusting of the dras arc complex this was followed by partial erosion during deposition of the indus molasse and then back thrusting and folding related to uplift of the high himalayas in the later tertiary

stratigraphic evidence for an early collision between northwest india and asia the collision of india with asia1 had a profound influence on late cretaceous and cenozoic oceanography2 climate3 fauna extinctions4 and the motion of at least some of the earth s litho spheric plates5 as the collision ended a period of rapid indo asian convergence6 a precise knowledge of its timing when the crust of the neo tethys ocean was completely subducted7 at some point along the plate boundary is important for understanding its wider consequences but current estimates of the collision age range from 65 to 38 myr before present6 8 11 here we report the results of extensive biostratigraphic analyses from waziristan and kurram in northwest pakistan which show that accretionary prism and trench strata were first thrust onto the northwest indian passive margin after 66 myr but before 55 5 myr after this time volcanic arc fragments the accretionary prism trench material and imbricates of the north indian slope were raised to shallow water depths and overlapped by upper palaeocene shallow water carbonates and shales12 14 indicative of post collision thrusting in this region finally both the suture and the indian craton were overlapped by continuous unconformable upper lower eocene shallow marine strata demonstrating that suturing was complete by 49 myr

reply to comments on palynological evidence for the palaeocene evolution of the forearc basin indus suture zone ladakh india by peter clift

sedimentary and geochemical evolution of the dras forearc basin indus suture ladakh himalaya india the nindam formation of the indus suture zone represents the forearc basin to the dras kohistan volcanic arc which was generated in an intraoceanic setting during mid cretaceous time and accreted to the margin of eurasia during late cretaceous time the nindam formation comprises volcaniclastic sediment and pelagic carbonate deposited in cyclic influxes of high density sheet like turbidites with locally well defined channel morphologies debris flow deposits as much as 5 m thick that rework older material are volumetrically 5 of the sequence a fine grained basal section is succeeded by several hundred meters of cyclic sandy turbidites and finally a more shaley top this large scale variation may be linked to tectonic controls on arc activity while individual sandy packages 50 100 m thick are inferred to have a glacioeustatic origin sedimentation mirrors similar patterns observed in the modern mariana and tonga forearcs the lack of major unconformities and large scale reworking suggests that the volcaniclastic sedimentary rocks should form a relatively complete record of geochemical change in the arc source the sediment trace and rare earth element ree signature is similar to that of the dras and chalt volcanic rocks erupted at the volcanic front during the intraoceanic phase of activity and is distinct from the kardung volcanic group erupted during the continental arc phase following collision with the eurasian margin nd isotopes also support an intraoceanic origin the sedimentary rocks show either no or slight light ree enrichment similar to modern sediments from the mariana arc as well as the volcanic and intrusive core of the dras kohistan arc the overall chemistry of the dras kohistan arc is thus more depleted in light ree than continental crust our data do not support models that propose continental crust being formed along intraoceanic active margins

zircon u pb geochronology and hf isotopic constraints on petrogenesis of the gangdese batholith southern tibet abstract during the mesozoic cenozoic northward neotethyan subduction and subsequent india asia collision gave rise to the extensive transhimalayan magmatism that stretches from burma and western yunnan through southern tibet to the ladakh and kohistan complexes to understand the age distribution and petrogenesis of the gangdese batholith the largest intrusive exposure along the transhimalayan magmatic belt fifty granitic samples were selected for in situ zircon u pb and hf isotopic analyses the u pb data suggest four discrete stages of magmatic activity i e 205 152 109 80 65 41 and 33 13 ma respectively with the 65 41 ma stage being the most prominent the hf isotopic data indicate that the gangdese batholith is overwhelmed by positive e hf t values which are comparable to those of the kohistan ladakh batholiths in the west but differ markedly from those of the chayu burma batholiths in the east most of the gangdese granites show similar and young hf model ages 1000 300 ma indicating their derivation from juvenile crust however those formed in the 65 41 ma stage exhibit more heterogeneous hf isotopic ratios with negative e hf t values being observed in some granites younger than 50 ma suggesting the involvement of old indian continental crust in their petrogenesis this age may thus mark the onset of the india asia collision the newly established zircon u pb age and hf isotope database of the gangdese batholith can be used as a powerful tracer or fingerprint when studying the source to sink relation of the sediments eroded from the southern tibetan plateau

formation of melanges in the indus suture zone ladakh himalaya by successive subduction related collisional and post collisional processes during late mesozoic late tertiary time

mapping near inertial variability in the se bay of biscay from hf radar data and two offshore moored buoys 1 hf radar surface current data together with data from two operational offshore oceanographic buoys located over the slope are used to map the variability associated with the near inertial waves during a target year 2009 in the se bay of biscay the results obtained show the complex 4d distribution of inertial oscillations in this area we find a very pronounced horizontal structure across the area with ranges of a factor 5 in near inertial kinetic energy this pattern presents also strong seasonal variability with a peak in ke closer to the shelf break in summer whereas winter maximum is weaker and located further to the north east the mooring data indicate more trapping near the surface in summer these patterns are discussed in relation to the known seasonal differences in atmospheric buoyancy forcing and the characteristics of the sub inertial surface velocity field

age of initiation of collision between india and asia a review of stratigraphic data abstract the collision of india with asia is perhaps the most profound tectonic event to have occurred in past 100 ma it is responsible for the uplift of the himalayas and tibetan plateau and has been argued to have been responsible for geological geochemical and climatological consequences of global extent yet the age of initiation of this collision remains poorly constrained the literature is replete with estimates that range from the late cretaceous 65 ma to latest eocene

mineral chemistry and k ar ages of plutons across the karakoram fault in the shyok nubra confluence of northern ladakh himalaya india abstract petrographic analyses of plutons across the karakoram fault in the shyok nubra confluence of northern ladakh area revealed that the rocks consist of diorite granodiorite granite and leucogranite pyroxene and biotite chemistries by epma indicate that most of the diorite granodiorite and granite are calc alkaline and formed in an arc related tectonic setting these calc alkaline plutons yield k ar biotite ages from 49 3 1 1 to 51 2 1 1 for ladakh batholith in khardung la and from 60 8 1 3 to 65 8 1 4 ma for granites and diorites in hundar area the k ar ages of the hundar igneous complex are within the age range of 46 70 ma of the ladakh batholith near leh town and the neighbor sites indicating the hundar igneous complex as a part of the ladakh arc their ages are also coincident with the khardung volcanics 67 4 and 60 5 ma the calc alkaline granites from panamik of karakoram block yield k ar biotite ages of 95 7 2 1 and 96 7 2 1 ma suggesting that the granites are member of the plutons 90 120 ma occurring in northern pakistan tangtse in ladakh and western tibet that emplaced during subduction of the neo tethyan oceanic plate under the karakoram block the leucogranite and granodiorite in the panamik region yield k ar biotite and muscovite ages ranging from 9 18 0 21 to 9 45 0 21 ma the leucogranites are the s type related to post collision tectonic setting and are considered to have emplaced in relating to activation of the karakoram fault