magnitude of late quaternary left lateral displacements along the north edge of tibet images taken by the earth observation satellite spot of the quaternary morphology at 18 sites on the 2000 kilometer long altyn tagh fault at the north edge of tibet demonstrate that it is outstandingly active long term left lateral strike slip offsets of stream channels alluvial terrace edges and glacial moraines along the fault cluster between 100 and 400 meters the high elevation of the sites mostly above 4000 meters in the periglacial zone suggests that most offsets resulted from slip on the fault since the beginning of the holocene these data imply that slip rates are 2 to 3 centimeters per year along much of the fault length and support the hypothesis that the continuing penetration of india into asia forces tibet rapidly toward the east

position of the lhasa block south tibet during the late cretaceous the latitude of the lhasa block xizang south tibet during the late cretaceous early tertiary is of prime importance for understanding the collision of india and eurasia and the mechanism of the formation of the qinghai xizang plateau during the first field expedition of the french chinese collaboration several geological formations have been sampled in southern tibet between lhasa 29 40 n 91 09 e and dingri 28 35 n 86 38 e we present here the first results obtained for middle cretaceous to palaeocene red beds from the lhasa block north of the yarlung zang bo suture zone recognized as the main suture between the indian and the eurasian plates they indicate a palaeolatitude of the lhasa block of 20 n during the late cretaceous while india was situated 30 s

the indus tsangpo suture zone in ladakh northwest himalaya further palaeomagnetic data and implications abstract a total of 81 samples 244 specimens from upper cretaceous indus molasse and middle to upper cretaceous dras flyschoids of the indus tsangpo suture zone in ladakh northwest himalaya has been studied by thermal demagnetization methods both formations showed a characteristic magnetization component indicative for equatorial to low northern palaeolatitudes of acquisition similar palaeolatitudes have been obtained before from secondary magnetization components of early tertiary age in the ladakh intrusives and in the tibetan sedimentary series of central nepal the present characteristic components are interpreted likewise as secondary magnetizations which stabilized between 50 and 60 m y ago during greater india s collision with asia s southern margin the dras flyschoids show another magnetic component which in case of primary origin indicates acquisition at a low southern palaeolatitude if correct this interpretation supports recent suggestions for late cretaceous obduction of an island arc on greater india s northern margin

rotational overthrusting of the northwestern himalaya further palaeomagnetic evidence from the riasi thrust sheet jammu foothills india abstract thermal demagnetization results 316 samples are presented for the tertiary succession of the riasi thrust sheet jammu foothills northwestern himalaya primary and secondary magnetization directions of murree group red beds miocene to upper eocene sampled northeast of jammu indicate for this part of the riasi thrust sheet a clockwise rotation over about 45 with respect to the indian shield since late eocene early miocene time this accords with clockwise rotations of similar magnitude observed in the panjal nappe and the krol belt and is interpreted as representative for the northwestern himalaya results from the western part of the kalakot inlier sampled northwest of jammu i e basal murree claystone middle eocene and carbonate from the subathu group lower middle to lower eocene indicate an aberrant 20 25 counterclockwise rotation which is of local importance only available observations on rotation of himalayan thrust sheets with respect to the indian shield indicate that the himalayan arc has formed through oroclinal bending this supports powell and conaghan s and veevers et al s model of greater india with large scale intracontinental underthrusting along the main central thrust beneath the tibetan plateau minimal magnitudes of underthrusting of 550 km in the krol belt and 650 km in the thakkhola region are concluded palaeolatitude observations herein and in 1 agree with absolute positioning of the indian plate based on india africa relative movement data fixed to a hotspot frame in the atlantic ocean and with palaeolatitude observations from dsdp cores on the indian plate collision related secondary magnetic components observed both to the north and to the south of the indus tsangpo suture zone show palaeolatitudes between the equator and 7 n comparison of both datasets indicates that initial contact between greater india and south central asia had been established in the hindu kush karakorum region by about 60 ma ago whereas eastwards progressive suturing had advanced to the lhasa block segment of the indus tsangpo suture zone before 50 ma ago

india eurasia collision chronology has implications for crustal shortening and driving mechanism of plates the motion of the indian plate is determined in an absolute frame of reference and compared with the position of the southern margin of eurasia deduced from palaeomagnetic data in tibet the 2 600 900 km of continental crust shortening observed is shown to have occurred in three different episodes subduction of continental crust intracontinental thrusting and internal deformation and lateral extrusion the detailed chronology of the collision and plate reorganizations in the indian and pacific oceans supports the hypothesis that slab pull is a dominant driving mechanism of plate tectonics

tectonic environment and geodynamic significance of the neo cimmerian donqiao ophiolite bangong nujiang suture zone tibet the bangong nujiang suture zone is underlain by a discontinuous and roughly ew ophiolite belt around donqiao gyanco ophiolitic and metasedimentary palaeozoic series form nappes thrusted over jurassic flysch series all these series have undergone a late symmetrical folding accompanied by generally northward reverse faulting although strongly dismembered a complete ophiolitic sequence comprising harzburgites with large podiform type chromite deposits wehrlites cumulate gabbros sheeted dolerite dykes foliated garnet bearing amphibolites and pillow lavas has been found

shallow gas accumulations in the german north sea abstract shallow gas here defined as free gas that is trapped in unconsolidated deltaic and shallow marine siliciclastic sediments of plio pleistocene age is found within the topmost 1000 m of sediment in the southern north sea shallow amplitude anomalies in seismic reflection data are likely due to the presence of gas the most prominent and easy to recognize indicators are high amplitude anomalies or bright spots that are widespread within the southern north sea gas from shallow reservoirs is currently produced offshore the netherlands in this study we determine whether there are analogous shallow gas accumulations within the german north sea therefore we screened 2d and 3d multichannel seismic data for shallow amplitude anomalies several clusters of bright spots are identified above salt domes that closely resemble the economic deposits known in the dutch sector in both size and their characteristic multilayered shape three of these potential gas accumulations occurring in combination with additional hydrocarbon indicators such as seismic attenuation and velocity push downs are investigated in detail and compared to shallow gas fields from offshore the netherlands amplitude anomalies indicate gas seepage on the seafloor that may contribute to the atmospheric methane budget and may have an impact on offshore infrastructure

rock magnetic properties and structural development in the core of the hazara kashmir syntaxis ne pakistan paleomagnetic and structural analyses have been conducted on three well exposed sections through a 6 8 km thick pile of molassic red beds murree formation in the lowermost tectonic unit of the hazara kashmir syntaxis micropaleontological age determinations of the lowermost murree sediments indicate late paleocene deposition 55 m y from south to north the sections are situated in the jhelum neelum both in azad kashmir and kaghan northeastern pakistan valleys thermal demagnetization experiments suggest that haematite with high unblocking temperatures carries stable characteristic remanence directions the relationship between finite strain and magnetic fabric was established by mapping deformed reduction spot strain markers and by measuring the anisotropy of magnetic susceptibility ams for the jhelum valley the weakly tectonized murree beds are characterized by flattened ams ellipsoids resulting from diagenetic compaction inclination values suggest that the murree foreland basin started to develop at about 8 n during the early suturing of india and the development of island arcs to the north india has moved northward by at least 2600 km since collision with eurasia in the paleocene declination values suggest 45 of clockwise rotation of the block supporting the murree formation relative to the indian craton for the neelum and kaghan valleys quantitative strain mapping shows a progressive increase of deformation northward nrm directions rotate passively toward the cleavage plane which parallels the foliation of the ams ellipsoids nrm directions and ams ellipsoids are deformed because of superposition of tectonic strain on a primary compactional strain the ams pattern is interpreted in light of this superposition and a regional deformation path from south to north is suggested a tectonic rotation model is proposed which is consistent with the transport directions around the hazara kashmir syntaxis and the rotation of thrust sheets indicated by the nrm data this model relates the convergent transport directions with the mean indentation direction of india into asia

a palaeomagnetic reconnaissance of kashmir northwestern himalaya india abstract thermal demagnetization studies of 800 palaeozoic and lower mesozoic samples mainly carbonates from 14 localities in kashmir showed four magnetic components a a recent field component of normal polarity and large intensity b a middle to late tertiary secondary component of large intensity and of reversed and normal polarity which indicates clockwise rotation of central and eastern kashmir over approximately 45 with respect to peninsular indo pakistan c primary magnetic components of triassic late permian early carboniferous siluro ordovician and middle to early ordovician age the triassic and late permian components show a 20 30 cumulative counterclockwise offset with respect to the indo pakistan apparent polar wander path apwp this indicates a post middle to late triassic counterclockwise rotational movement of kashmir over 65 75 with respect to peninsular indo pakistan d a component of low inclination and predominantly east west declination which is observed only in rocks of pre panjal traps age a secondary origin associated with extrusion of the panjal traps flows is surmised but could not be established beyond doubt alternatively this component may be related to the regional foliation the triassic and late permian primary component directions are predominantly of normal polarity this suggests a pre punjabian late permian upper age limit for the permo carboniferous kiaman reversed polarity interval which is earlier than the early to late tatarian limit observed in the u s s r

cretaceous paleomagnetic results from western tibet and tectonic implications we present paleomagnetic results obtained from samples collected in the summer of 1989 along a 1000 km traverse between yecheng xinjiang and shiquanhe tibet in the western qinghai xizang plateau along 80 e longitude during this field trip 480 paleomagnetic cores in jurassic to tertiary limestones and sandstones were drilled at 49 sites 400 were measured isothermal remanent magnetization analysis indicates the existence of high coercivity minerals and thermal rather than alternating field demagnetization was found to be more efficient in isolating paleomagnetic directions the characteristic magnetization has rather low unblocking temperatures 250 560 c in most limestone samples and higher unblocking temperatures 400 c 680 c in the sandstone samples about half of the measured samples show the present geomagnetic field or aberrant directions the remainder display stable multicomponent magnetizations the stable characteristic magnetizations indicate 1 a probable jurassic remagnetization 2 a cretaceous 120 80 ma magnetization which passes a fold test yielding a mean pole at 66 2 n 245 0 e a95 5 1 n 14 sites and 3 a large scatter of tertiary directions which may be due to tectonic problems and or remagnetization in the sampling zone the cretaceous paleodirections from aksaichin and longmuco 11 sites on the qiangtang north tibet block are very similar to those from shiquanhe three sites on the lhasa south tibet block separated by 300 km this suggests that the north and south tibet blocks formed a single unit at least as early as the cretaceous comparing our results with previous paleomagnetic work on the tibetan plateau it is found that the paleolatitude of 10 6 5 1 obtained from this study for a reference at domar 33 75 n 80 4 e is close to that 9 6 2 8 obtained by achache et al 1984 and lin and watts 1988 from the takena formation 110 100 ma in the lhasa region 30 n 91 e in addition it appears that the southern margin of the tibetan blocks i e eurasia occupied an e w trending position at about 7 6 n latitude paleodeclination differences between the western and eastern tibetan blocks suggest internal deformations of the plateau at different scales from 1 to 1000 km according to differences in paleomagnetic declinations the arcuate shape of the blocks would have been partly acquired after the collision

palaeomagnetic estimates of crustal shortening in the himalayan thrusts and zangbo suture this article reports new palaeomagnetic results from precisely dated late palaeocene limestones from the former northern margin of the indian subcontinent now in tibet between the major himalayan thrusts and the india tibet suture zone convergence in the suture and intracontinental thrusting can be estimated separately and are respectively found to be of the order of 550 km 650 km and 400 km 400 km comparison with kinematic models derived from magnetic anomalies constrains the age of the collision at about 50 myr

the himalayan arc large scale continental subduction oroclinal bending and back arc spreading abstract palaeomagnetic results from the himalayan arc and southern tibet compared with simulated apparent polar wander paths for the indian plate show a consistent pattern of rotations of the himalayan arc relative to the indian shield varying gradually from 45 clockwise in the northwestern himalaya to slightly counterclockwise in the lhasa region this pattern is consistent with continental underthrusting of greater india beneath the tibetan plateau since the early miocene over at least 650 km at the longitude of western nepal and oroclinal bending since the latest miocene available palaeomagnetic observations support the steady state model for the formation of the himalayan arc with refinements as follows 1 collision between greater india s northern boundary and southern asia occurred at equatorial latitudes with progressive suturing from palaeocene in the northwestern himalaya until early eocene in the eastern himalaya 2 continuing convergence and indentation of greater india into southern asia over about 2000 km up to the early miocene resulted in southeastward extrusion of indochina and 3 neogene counterclockwise rotational underthrusting of greater india along the main central thrust with pliocene quaternary oroclinal bending of the himalayan arc

a review of indian phanerozoic palaeomagnetism implications for the india asia collision abstract an overview is presented of the indian apparent polar wander path apwp for the phanerozoic and in particular for post late palaeozoic times this apwp is compiled on basis of data available at october 1981 from peninsular and extrapeninsular indo pakistan and from dsdp cores from the indian plate one of the more important and newly recognized features of this apwp is a large scale triassic jurassic loop this loop indicates a changeover from a late palaeozoic early mesozoic northwards and counter clockwise rotational movement with greater india reaching moderately low southern latitudes into a southwards and clockwise rotational movement during the early to middle jurassic recognizable likewise in apwp s from other gondwana continents this loop reflects the opening of the neotethys studies of extrapeninsular regions up to and north of the indus tsangpo suture zone have shown wide spread presence of magnetic overprints which delineate two regionally confined age groups younger overprints 20 40 m y predominate in the more external thrust zones older overprints 50 60 m y in contrast are found in the more internal zones both north and south of the indus tsangpo suture zone the latter are interpreted to reflect a late phase of relaxation in the early tertiary collision of greater india with south central asia or off shore island arcs which occurred at equatorial to low northern palaeolatitudes 0 10 n subsequent northwards movement over 2500 3000 km or more and impingement of greater india into southern asia resulted into large scale underthrusting of greater india along the main central thrust beneath southern tibet and to clockwise rotation of thrust units in the western himalaya a discrepancy between indian palaeomagnetic data and results available todate from southern tibet is discussed

paleogeographic and tectonic evolution of southern tibet since middle cretaceous time new paleomagnetic data and synthesis during the second french chinese paleomagnetic campaign in tibet in the summer of 1981 we sampled the middle cretaceous red beds of the takena formation and the cenozoic volcanics of the lingzizong formation a detailed analysis of about 400 specimens of red beds reveals a stable component of normal magnetization n in the north of the lhasa block north of the nyainqentanglha range and two stable components in the south lt ht where the red beds are more strongly folded and are unconformably overlain by the lingzizong volcanics all three components are carried by hematite blocking temperatures range from 400 to 600 c for lt and up to the neel temperature of hematite for both n and ht lt is shown to postdate part of the folding of the takena whereas n and ht both indicate a positive fold test at the 99 probability level in addition a small less than 10 of the natural remanent magnetization antiparallel component is superimposed in most samples and may be consistent with a model of long term acquisition of a chemical remanent magnetization for the red beds analysis of the volcanics reveals a single stable component with mixed polarities carried either by hematite or magnetite the paleomagnetic directions indicate that 1 the lhasa block stood at 12 5 3 n by upper cretaceous and at 13 5 6 5 n in the paleocene eocene thus confirming the limited displacement of the margin of eurasia between albian aptian deposition of the red beds and eocene onset of the india asia collision these values imply crustal shortening by as much as 1900 850 km north of the block since the upper cretaceous and by 1400 1200 km south of the block since the onset of the collision 2 southern tibet formed a single tectonic unit by middle cretaceous time and 3 differential rotations are observed within the block and are related to the collision these rotations are discussed in the frame of a recent propagating extrusion tectonics model this study confirms the close paleogeographic relationship between indochina khorat plateau and southern tibet prior to the india asia collision

paleomagnetism in the tajikistan continental shortening of european margin in the pamirs during indian eurasian collision abstract a stable and well defined magnetization withd 350 i 55 5 and 95 4 carried by hematite is isolated in the red beds of the tajik basin the fold test is positive 99 probability and this magnetization predates the late eocene early oligocene folding phase in the tajik basin the coordinates of the vgp are 82 n 323 e dp 4 dm 6 with a paleolatitude of dushanbe 38 38n 68 51e of35 6 5 a high blocking temperature component with weak intensity and reverse polarity has been demonstrated in the site of ragoon but it has not been isolated this component predates the long cretaceous normal period and is compatible with the older stratigraphic age attributed to the formation valanginian these arguments indicate that this component is likely of primary origin the other component of higher intensity and clearly isolated in all the sites is a pre folding remagnetization the process of remagnetization is attributed to the tectonic events such as fluids migration and slight heating during a few million years which took place just before the first late eocene early oligocene phase of folding an anticlockwise rotation of 26 encountered by the region of dushanbe is in good agreement with the indentation model of collision leading to anticlockwise rotation west of the indian wedge and clockwise rotation to the east a comparison of the paleolatitude of dushanbe computed from the direction of magnetization and the paleolatitude expected from the apparent polar wander path for eurasia gives an estimate of the post collision continental shortening north of the tajik basin this shortening did not exceed a few hundred kilometers and was probably between 100 and 300 km an estimate of the roles of the different classical mechanisms of crustal shortening is discussed and a paleogeographic reconstruction giving the location of the southern margin of eurasia at 45 ma is proposed the paleolatitude deduced from the prefolding remagnetization of the red beds of the tajik basin is then compared with the results obtained by soviet workers in tertiary sediments of the same area revealing strong contradictions in interpretation this contradiction emphasizes the problem of the rigidity of european plate

revised and synthetic apparent polar wander paths of the african eurasian north american and indian plates and true polar wander since 200 ma we have reviewed paleomagnetic data available for the eurasian african north american and indian plates over the last 200 ma selection criteria are those generally accepted with an emphasis on evidence for lack of remagnetization accurate dating and proper structural analysis this results in 23 35 51 and 2 poles for eurasia africa north america and india respectively we believe that this limited set of higher quality data is more likely to reveal key features of apparent polar wander apw paths than averaging of larger data sets involving less stringent selection criteria we propose and describe revised apw paths but more importantly we next use relative motion models to transfer all data in a common reference frame we find good agreement between transferred data when they are averaged separately for each plate in independent 20 ma windows this is a check on consistency of paleomagnetic data kinematic models and of the geocentric dipole hypothesis transferred data from all plates are averaged in 20 ma windows to generate synthetic apw paths for all plates studied these synthetic paths are in agreement with the original revised apw paths that use only data from a single plate moreover both geographic and time resolution are improved spatial confidence intervals are of the order of 5 the synthetic paths display interesting features such as a previously ill recognized apw loop for eurasia paleomagnetic and hotspot apw are next compared and a determination of true polar wander tpw is derived we find significant tpw amounting to over 20 in the last 200 ma tpw appears to be episodic with a standstill between 180 and 110 ma there is general agreement with a previous study of livermore et al 1984 the tpw standstill appears to correlate with a time of decreasing reversal frequency ending with the cretaceous long normal superchron other periods of fast tpw would seem to correspond to increasing reversal frequency however it is suggested that the major tpw hairpin at 50 ma might correspond to the collision of india with eurasia tentative correlations with core or mantle indicators can be understood as a result of couplings between the core mantle and lithosphere we believe primarily related to episodic evolution of the d layer

the tibetan side of the india eurasia collision results are reported from the 1980 joint french chinese field expedition in tibet the area covered was from the high himalaya in the south to the region of nagqu 250 km north of yangbajain ophiolites in the zangbo valley represent remnants of the crust of an ocean basin which lay adjacent to the gangdise granodiorite belt in the late mesozoic the ophiolites were thrust to the south onto the cretaceous melange and triassic flysch but the age of this event is unclear in the tertiary sediments of the indian margin and the xigaze basin were folded with steeply dipping cleavage which indicates some north south shortening of the crust however the tertiary volcanic sequence on the lhasa block and further north shows comparatively little folding and thrusting in the quaternary deformation of tibet was characterized by east west extension

variability in north atlantic heat content and heat transport in a coupled ocean atmosphere gcm a coupled ocean atmosphere general circulation model has been used to study the variations of north atlantic upper ocean heat content ohc sea surface temperature sst and ocean heat transport oht and the relationships between these three quantities we find that ohc anomalies and salinity anomalies propagate anti cyclonically around the north atlantic subtropical gyre they propagate eastward in midlatitudes and westward in low latitudes both the advection of mean temperature by anomalous currents and the advection of temperature anomalies by mean currents are responsible for these zonal propagations in addition to zonal propagations upper ocean temperature anomalies propagate southward in the eastern north atlantic where subduction plays a dominant role variability in the northward oht in the atlantic is primarily governed by variability in the ocean circulation rather than variability in temperatures fluctuations in oht are the major cause of anomalies in ohc and sst in the gulf stream extension region this is true both for interannual variability and for decadal variability on interannual time scales however surface fluxes also make a significant contribution analysis of the relationships of oht with ohc and sst suggests that a knowledge of oht fluctuations could be used to predict variations in ohc and therefore sea surface temperatures several years in advance

late cenozoic right lateral strike slip faulting in southern tibet field observations collected during the sino french himalaya tibet cooperation project 1980 1982 show that right lateral faulting between southern and northern tibet roughly along the chord joining the eastern and western syntaxes of the himalayan arc is a major component of the active tectonics north of the himalayas just north of the well developed rifts of southern tibet we studied three right lateral 100 200 km long strike slip faults forming an en echelon array along that chord evidence for earthquake surface breaks was found on each of these faults for the m 8 beng co or damxung strike slip earthquake of november 18 1951 rupture parameters could be constrained to be 8 2 m and l 90 km offset glacial and postglacial morphological markers 105 years and 104 years b p imply displacement rates of the order of 1 2 cm yr on the three faults the en echelon fault zone appears to extend westward 2000 km across the plateau to the karakorum fault and is thus referred to as the karakorum jiali fault zone kjfz fast rates of slip on it and on faults along the northern rim of tibet appear to contrast with the slower rates of deformations in the interior of the plateau our estimates of slip rates on the strike slip and normal faults of southeastern tibet suggest that eastward extrusion of north tibet between the right lateral kjfz and the left lateral altyn tagh and kun lun faults absorbs at least 30 of the present convergence between india and asia we propose an instantaneous velocity model of the active tectonics of asia compatible with such faulting rates and geometries evidence for tertiary right lateral strike slip movements in southern tibet and around the eastern syntaxis of the himalayas is also found in the structural record offsets of various large scale geological features imply that these movements have been large

paleomagnetism of cretaceous rocks from eastern qiangtang terrane of tibet thermal demagnetization has successfully isolated high unblocking temperature characteristic directions from paleomagnetic samples of lower and middle cretaceous redbed formations from eastern qiangtang terrane tibet the tilt corrected mean direction for the lower cretaceous is d i 57 7 50 2 with 95 10 9 and n 12 sites and that for the middle cretaceous is d i 39 7 51 6 with 95 8 5 and n 11 sites both formations pass the fold test and the latter possesses two polarities the magnetization predates the eocene and was probably acquired during cretaceous time comparison of the mean directions with expected directions from the stable interior of eurasia indicates significant clockwise rotation but little paleolatitudinal change for the sampling area deformation and rotation of these rocks are presumably related to the collision of india with asia and its subsequent northward indentation into asia existing paleomagnetic data from tibet and its environs seems to be compatible with a crustal shortening thickening model dewey et al 1988 in that the continental crust directly north of the indian indenter was substantially shortened north south whereas in the vicinity of the western and eastern syntaxes latitudinal displacement was minimal but tectonic rotation was very important more data are needed to further differentiate between this model and the lateral eastward crustal extrusion model molnar and tapponier 1975

paleogeographic maps of the continents bordering the indian ocean since the early jurassic paleomagnetic data from the african plate from the early jurassic onward are critically re evaluated and updated resulting in a set of 30 paleopoles from which an apparent polar wander path is derived using 20 ma intervals this path is then used in conjunction with kinematic models of the indian and atlantic oceans to place other continents bordering the indian ocean eurasia india islands and plateaus madagascar seychelles mascarene and blocks involved in the collision of india with eurasia south tibet indochina in an absolute paleogeographic frame fixed with respect to africa paleogeographic maps are presented for the early jurassic pre breakup the jurassic cretaceous boundary anomaly ml5 the early cretaceous m2 the late cretaceous a 34 the cretaceous tertiary boundary a 29 the early eocene a 24 the middle eocene a 21 and the oligocene miocene boundary a 6 observed and predicted paleomagnetic directions for landmasses other than africa i e for western europe china korea india and australia which are not used in deriving the maps are found to be in very satisfactory agreement the quality of reconstructions as measured by rms discrepancies between observed and predicted paleolatitudes is of the order of 5 the main features of the paleogeographic maps are discussed with the aim of relating oceanic and on land geodynamic events the constraints provided by tibetan data on the india asia collision and the 20 ma reorganization of geology and plate boundaries in a band extending from the south china sea through tibet to the red sea system are discussed in more detail we emphasize the episodic nature of the breakup of gondwanaland and formation of the indian ocean and subsequent interaction with eurasia in which six major discrete events are identified separated by 30 ma phases of rather uniform plate motion

right lateral shear and rotation as the explanation for strike slip faulting in eastern tibet the convergence of two continents can be accommodated by crustal thickening and by lateral transport of crust out of the path of the converging continents1 3 the principal features suggesting that lateral transport is important are major strike slip faults striking roughly orthogonally to the orientation of convergence between the continents displacement on such faults is imagined to allow lateral transport of material with respect to the converging continents possibly accounting for a large fraction of the convergence between the two continents the most spectacular example of such strike slip faulting is in the eastern part of the tibetan plateau where three major left lateral faults with slip rates of 10 mm yr 1 and several smaller roughly parallel faults dominate the regional strain field2 3 cobbold and davy4 suggested that these faults may be rotating in a clockwise fashion here we put bounds on that rate of rotation and conclude that the image of lateral transport on such faults2 known also as continental escape extrusion or expulsion is an illusion and that instead the left lateral slip on east striking planes in eastern tibet is a manifestation of north striking right lateral simple shear if this conclusion is correct the east striking left lateral faults and the crustal blocks between them are rotating clockwise at 1 2 myr 1 the east west dimension of eastern tibet is shortening at 10 20 mm yr 1 and little material is moving eastward out of india s path into eurasia by left lateral simple shear