present day stress field changes along the baikal rift and tectonic implications intraplate extension in a frame of a global compressional stress field seems linked to local lithospheric perturbations lithospheric thinning or thickening able to modify the resulting state of stress zoback 1992 the baikal rift zone brz siberia is located north of the india asia collision zone and exhibits no direct communication with any oceanic domain it can thus be fully considered as an area of continental extension dominated by the global compressional intraplate stress field resulting from plate driving forces in order to address the problem of its dynamics and kinematics and their links with the india asia collision a comprehensive stress tensor analysis is presented based on 319 focal mechanisms of earthquakes located along the whole baikal rift the stress field is varying at different scales of observation when looking at central asia several thousands kilometers the maximum horizontal stress shmax directions remain rather constant with a fan shape geometry when the tectonic regime goes from compressional himalayas to extensional baikal when observing the baikal rift about 1000 km long clear variations of the stress regime are observed from an extensional regime in the central part of the rift to wrench ones in its northern and southern ends finally at the scale of 100 km systematic shmax reorientations occur close to major rift faults we thus infer that the interaction between collisional processes and inherited structures may have a strong influence on rift dynamics we then use computed stress tensors to predict slip vectors on major rift faults deformation patterns show two distinct parts of the rift the south baikal rift sbr is characterized by a constant trending around n100 e slip vector meanwhile the north baikal rift nbr exhibits a complex block rotation behavior involving at least three crustal blocks we propose to interpret these surficial structures and motions as the result of an interaction between the regional compression coming from the india asia collision and the geometry of the hardly deformable siberian platform this particular setting can explain most of the surficial deformation patterns which suggest a large scale cracking of the lithosphere in the baikal region other possible sources of stress could also be considered like deep mantellic upwelling or trench suction linked to the pacific subduction

geometry and kinematics of recent deformation in the mondy tunka area south westernmost baikal rift zone mongolia siberia we used satellite imagery and field data to investigate the south westernmost baikal rift zone we focus our study in the mondy and ikhe ukhgun valleys site of an mw 6 9 seismic event in 1950 surface deformations are observed along the e w trending mondy strike slip fault and along the ikhe ukhgun thrust the mondy fault system is 80 km long and is composed of four segments 10 15 km long these segments are characterized by subvertical planes with left lateral movements the ikhe ukhgun thrust is 20 km long dips 40 to the south and shows reverse movement with a left lateral component these observations are consistent with the present day regional nne ssw compression and with the focal mechanism of the 1950 mondy earthquake that was recently re evaluated these features like those observed in the tunka basin demonstrate a recent change of regional strain regime from transtension to transpression that we place before the late pleistocene

upper mantle seismic reflections beneath the east pacific rise multichannel seismic reflection profiles from the east pacific rise show distinctive patterns of reflecting events immediately below the reflection moho in the axial region these events begin at the reflection moho horizon between 2 and 12 km from the ridge axis they dip inward in two way traveltime by 0 2 to 0 4 s over horizontal distances of 1 to 3 km depth conversion indicates that their dip is between 30 and 45 the events terminate or fade away down dip and are not observed beneath the ridge crest itself they are observed individually or in pairs about the ridge axis and have only been identified in the axial region we believe that these are the first well documented examples of upper mantle events in marine seismic observations from an active spreading environment they provide much needed observational data on the structure of the uppermost mantle beneath the mid ocean ridge we favor the hypothesis that the sub moho events are directly related to the accumulation of melt in the upper mantle if this interpretation is correct the distribution of events implies that melt arriving at the base of the crust is not always centered with respect to the ridge axis or any imaged crustal features

morphotectonics of the tunka rift and its bordering mountains in the baikal rift system russia abstract the tunka section of the baikal rift system presents a uniform alternation of the following neostructural forms tilted horsts and asymmetrical block uplifts on the northern flank the central system of the rift valleys and the arched uplift of the southern flank this is a standard set of morphostructural elements for the baikal rift system the main morphological feature of the tunka rift is the strong inclination of its floor ranging from 900 m to 200 km in general elevation above lake baikal such traits of recent geodynamics as volcanism thermal activity and seismicity are also different from other parts of the rift zone all of these features of the tunka rift are related to the deep structure of the rift zone the peculiarities of the neotectonic structure of the tunka rift which are clearly expressed morphologically as is typical of the baikal rift system as well as its unique features are in accordance with deep geodynamic processes of the region on the other hand the development of the rift basin structures of the southwestern area near baikal is complicated by inversion deformations local uplifts followed by deformations of the basin sedimentary cover and inverted morphostructures expressed in relief are fixed against the background of the general subsidence of blocks of the pre cenozoic basement grabens the tunka rift has repeatedly experienced inversion deformations throughout its history the last wave of such deformations involved the southwestern region near baikal in the second half of the late pleistocene during the quaternary the positive component prevailed in the whole range of vertical movements of the inter rift and interbasin blocks since the late neogene these structures have experienced a slow but steady uplift accompanied by their extension at the expense of the bordering basins the remote influence of the india asia collision on the formation of the southwestern section of the baikal rift system is very significant and well pronounced in the development of the morphostructural elements of the tunka rift and its bordering mountains

characterizing the present day activity of the tunka and sayan faults within their relay zone western baikal rift system russia the sayan and tunka faults are located at the boundary between the northernmost mountain belt of central asia the sayan baikal ranges and the siberian platform these prominent crustal structures were involved in the opening of the southern baikal rift system since the beginning of the cenozoic and define large scale sharp morphotectonic features despite low instrumental seismic activity late pleistocene holocene morphotectonic features along the two faults indicate that the faults are active and have the capacity to produce strong earthquakes a careful mapping of the most recent trace of activity within the southeastern parts of the two faults where they merge within a relay zone demonstrates that they correspond now to left lateral reverse faults suggesting a recent inversion of their vertical component we also show that the two faults are now structurally connected via a young surface rupture and that no obvious post last glacial maximum ruptures are observed along the central part of the sayan fault beyond its junction zone with the tunka fault this suggests that the left lateral strike slip deformation is transferred from the eastern sayan fault to the tunka fault a detailed morphotectonic study along the southeastern sayan fault allows estimating a left lateral slip rate between 1 3 min and 3 9 mm year max finally a critical review of russian paleoseismic data combined with our paleoseismological investigations allows us to propose that the mean recurrence time along the two faults is on the order of 4 kyr and that they may have either ruptured together or during seismic clusters

arshan palaeoseismic feature of the tunka fault baikal rift zone russia the traditional concept of the rift development of flank depressions in the baikal rift zone is now doubted in view of some indicators for compression deformations identified by the seismogeological and geodetic methods besides the paleoseismological investigations revealed seismogenic strike slips and reverse faults in the tunka fault zone that is a major structure controlling element of the tunka rift depression however a detailed study of the upslope facing scarp in the arshan paleoseismogenic structure zone has shown that its formation might be due to rift mechanism of basin formation age estimation has been made for the previously unknown pre historic earthquake whose epicentral area coincides with the western flank of the arshan paleoseismogenic structure judging from previously determined ages of paleoearthquakes the mean recurrence period for faulting events on the central tunka fault is 2780 3440 years

finite element modelling of crustal deformation in the baikal rift zone new insights into the active passive rifting debate abstract the origin of the forces responsible for crustal extension in the baikal rift zone siberia is the object of a debate between passive rifting models where crustal extension is primarily caused by horizontal forces related to the kinematics of asia india eurasia collision and active rifting models where crustal extension is primarily caused by a diapiric mantle upwelling in this work we used a two dimensional visco elastic finite element model in order to determine whether horizontal forces alone can account for the present day deformation in the baikal rift zone we tested a number of kinematic boundary conditions and compared predictions of various models against the observed stress and strain field deduced from seismotectonic data earthquake focal mechanisms and microtectonic analyses by adjusting the kinematic boundary conditions and using a three plate model with a differential displacement between the mongolian and amurian plates we found a best fit model that correctly accounts for the observed strain and stress field over the entire baikal rift zone the fact that our model does not take into account vertical forces but still explains most of the observed deformation suggests that the present day opening of the baikal rift is essentially controlled by horizontal forces related to the regional kinematics these forces could have their origin in the india eurasia collision zone further south this result does not imply that the asthenosphere played no role in the rifting process in particular before the fast rifting stage of the baikal rift evolution 3 4 ma but might suggest a recent plio quaternary triggering effect of the india asia collision on the deformation in the baikal rift

surface faulting accompanying the borah peak earthquake and segmentation of the lost river fault central idaho on the morning of 28 october 1983 the ms 7 3 borah peak earthquake struck central idaho and formed a y shaped zone of surface faults that is divided into a southern a western and a northern section the total length of the surface faults is 36 4 3 1 km and the maximum net throw is 2 5 to 2 7 m the near surface net slip direction determined from the rakes of striations in colluvium averaged 0 17 m of sinistral slip for 1 00 m of dip slip the 20 8 km long southern section is the main zone of surface faulting and coincides with the thousand springs segment of the lost river fault it has the largest amount of net throw most complex rupture patterns and best evidence of sinistral slip the surface faults include zones of ground breakage as much as 140 m wide en echelon scarps with synthetic and antithetic displacements and individual scarps that are nearly 5 m high the 14 2 km long western section diverges away from the lost river fault near the northern end of the southern section the net throw on this section is generally less than 0 5 m but locally is as much as 1 6 m the new ruptures are poorly developed across the crest and north flank of the willow creek hills they are mostly downhill facing arcuate scars perhaps incipient landslides that may overlie a deeper zone of tectonic movement the northern section at least 7 9 km long is on the warm spring segment of the lost river fault and has a maximum net throw of about 1 m the pattern of surface faulting on this section is simple compared to the other sections a 4 7 km long gap in 1983 surface faults separates the northern and southern sections but contains an older scarp of late pleistocene age geologic seismologic and geodetic data from the earthquake suggest that barriers confined the primary coseismic rupture to the thousand springs segment of the fault the rupture propagated unilaterally to the northwest from a hypocenter near the southeastern end of the segment the southeastern boundary of the segment is marked by an abrupt bend in the range front a 4 km long gap in late quaternary scarps and transverse faults of eocene age that intersect the lost river fault the northwestern boundary of the thousand springs segment is at the junction of the willow creek hills and the lost river fault here the southern and western sections of surface faults diverge and there is a gap in the 1983 scarps during the first few weeks after the main shock the large magnitude and large stress drop aftershocks clustered near this barrier later aftershocks were mainly northwest of the barrier on the warm spring and challis segments and showed that strain adjustments eventually affected the entire northern part of the lost river fault fault scarp morphology and the bedrock geology suggest that the boundary between the thousand springs and warm spring segments has probably ruptured less frequently and had less net slip during much of the late cenozoic than the interior of the adjacent segments the 1983 faulting shows that although segment boundaries can stop or deflect primary ruptures secondary surface faulting can occur on adjacent segments of the main fault a late pleistocene scarp in the 1983 gap suggests that infrequent earthquakes perhaps larger than the 1983 event might break through a segment boundary and thus release strain on two adjacent segments

timing of holocene paleo earthquakes along the langshan piedmont fault in the western hetao graben north china implications for seismic risk abstract geological evidence and precise age constraints for faulting events during the holocene are vital for assessing the seismic potential of active faults especially in regions lacking instrumental and historical records of earthquakes for this study we constrained the timing and recurrence intervals of holocene paleo earthquakes along the 160 km long ne sw trending langshan piedmont fault lpf which forms the nw boundary of the hetao graben north china the results of outcrop observations and radiocarbon dating reveal that 1 at least four surface rupturing earthquakes occurred during the past 9810 yr with an average recurrence interval of 2450 yr 2 the most recent earthquake mre probably took place within the past 1880 yr 3 rupturing of the entire lpf could produce an earthquake of mw 7 8 posing a significant seismic risk in the region of the western hetao graben we suggest that more detailed paleoseismological studies on the active lpf are needed in order to have a better understanding of its seismogenic behavior

interaction between normal fault slip and erosion on relief evolution insights from experimental modelling the growth of relief in active tectonic areas is mainly controlled by the interactions between tectonics and surface processes erosion and sedimentation the study of long lived morphologic markers formed by these interactions can help in quantifying the competing effects of tectonics erosion and sedimentation in regions experiencing active extension river long profiles and faceted spurs triangular facets can help in understanding the development of mountainous topography along normal fault scarps in this study we developed analogue experiments that simulate the morphologic evolution of a mountain range bounded by a normal fault this paper focuses on the effect of the fault slip rate on the morphologic evolution of the footwall by performing three analogue experiments with different fault slip rates under a constant rainfall rate a morphometric analysis of the modelled catchments allows comparing with a natural case tunka half graben siberia after a certain amount of fault slip the modelled footwall topographies of our models reaches a dynamic equilibrium i e erosion balances tectonic uplift relative to the base level close to the fault whereas the topography farther from the fault is still being dissected due to regressive erosion we show that the rates of vertical erosion in the area where dynamic equilibrium is reached and the rate of regressive erosion are linearly correlated with the fault throw rate facet morphology seems to depend on the fault slip rate except for the fastest experiment where faceted spurs are degraded due to mass wasting a stream power law is computed for the area wherein rivers reach a topographic equilibrium we show that the erosional capacity of the system depends on the fault slip rate finally our results demonstrate the possibility of preserving convex river long profiles on the long term under steady external tectonic uplift and rainfall conditions

dynamics of intracontinental extension in the north baikal rift from two dimensional numerical deformation modeling we model the recent deformation along a lithospheric scale cross section perpendicular to the northern part of the baikal rift zone brz with two dimensional finite element models using realistic lithospheric structure and rheological properties and imposing extension as a far field boundary condition we find a model that matches reasonably well the topography observed deformation pattern gravity anomalies and age of formation of the northern brz our results suggest that 1 extensional strain can occur away from the main rift basin in the sayan baikal range and create depending on the rheological properties of the lithosphere a large off rift basin analogous to the barguzin basin or a series of basins and ranges as observed in the southern part of the sayan baikal range 2 anelasticity plays a major role by participating in the uplift of rift shoulders and hanging wall deformation and allowing the subsidence and tilting of the hanging wall along high angle planar normal faults 3 the lower crust accommodates differential strain between the brittle upper crust and upper mantle by horizontal shear and lateral flow towards the regions of crustal and mantle thinning 4 far field extensional stress and a lithospheric discontinuity inherited from paleozoic tectonic events are sufficient to initiate rifting and basin subsidence and 5 there is no or very little dynamic contribution of a hypothetic asthenospheric plume under the brz at least in the recent phase of its evolution fast rifting stage 3 5 myr

the structure and development of the baikal rift depression abstract the baikal rift depression located in southeastern siberia is one of the best investigated intra continental rift structures in the world in addition to being the site of comprehensive studies by russian geo scientists for decades the baikal depression is now the subject of new international investigations using advanced technical means and technologies the present paper summarizes the principal results concerning the morphostructure of the baikal rift the stratigraphy of the cenozoic deposits and the stages of the baikal depression development based on cross sections which exhibit the impact of both tectonic and climatic processes the development of the baikal depression occurred through two stages i the pre crypto rift stage of the late cretaceous eocene and ii active rifting of the oligocene recent the second stage is divided into several steps and substeps separated by tectonic phases formation of the baikal rift zone appears to be related to the indo eurasian plate collision related to a model of passive rifting the uplifted shoulders of the depression have a complex morphostructure overlain by cenozoic deposits which are thin and restricted in area the near marginal zones of the rift are largely defined by the system of longitudinal blocks of different width surfaces of the blocks are inclined either to the uplifted shoulder of the rift bound by listric faults typical for western edges of the depression or to the axis of the depression cenozoic deposits on the blocks consist of accumulative plains composed primarily of thick lacustrine sequences

soils of an eolian analog of the leasburg surface southern new mexico abstract in a dissected mostly sandy terrain along the rio grande valley border of southern new mexico a reddish brown coarse loamy haplargid in an eolian deposit has a stage ii carbonate horizon that is typical of soils of the leasburg surface 8000 15 000 yr b p the eolian deposit buries sediments and soils of late pleistocene age or older thus it does not fit in the chronological framework of the stepped sequence of geomorphic surfaces along the valley border in which age of the surfaces and their soils increases with increasing elevation of the steps because the eolian deposit occurs in isolated areas where its age relative to the stepped sequence cannot be demonstrated geomorphically soil characteristics are major tools for placing the deposit and its soil in the chronological scheme for the area on the basis of the stage ii carbonate horizon the eolian deposit is considered to be an eolian analog of leasburg alluvium one of the leasburg haplargids in eolian sediments on a ridge crest has a total of 23 kg m2 of pedogenic carbonate downslope in an area that receives runoff from higher areas a fine loamy haplargid in leasburg alluvium has 186 kg m2 of carbonate a nearby coarse loamy haplargid that does not receive runoff has only 46 kg m2 of carbonate thus landscape position and texture have a major influence on the total amount of pedogenic carbonate which can range to more than eightfold in soils of leasburg age

late quaternary geology of the tunka rift basin lake baikal region russia abstract the objective of this research is to obtain a better understanding of the evolution of the tunka rift basin part of the baikal rift zone and how it relates to the overall geologic history of the region particular for the quaternary period the tectonically active baikal rift zone began forming over 50 million years ago and continues today in the tunka basin during the oligocene and middle pliocene relatively weak tectonic disturbances took place and thick accumulations of organic rich sands silts and clays were deposited in lacustrine marshy subtropical environments tectonism increased between the miocene and pliocene and thick units of coarse alluvium and floodplain sediments were deposited during the late pliocene quaternary tectonism formed basins that are now filled with a variety of coarse clastic materials early and middle pleistocene sediments are poorly exposed covered by widespread late pleistocene deposits three late pleistocene sedimentary facies dominate boulder pebble gravels proluvial glacial fluvial and alluvial sediments alluvial sand and loess like sediments with associated slope deposits altered by post depositional wind erosion the relationship between these complexes including radiocarbon and other chronological data and fauna and flora remains indicates that they began forming c 70 000 yr ago paleosols glacial deposits and cryogenic material indicate that at times the climate was cool or cold during the early late pleistocene renewed tectonism took place causing increased deposition of coarse sediments the middle late pleistocene deposits consist mostly of sandy floodplain alluvium by the end of the late pleistocene holocene alluviation was reduced and replaced by a high degree of erosion and aeolian deposition

holocene paleoseismicity of the tunka fault baikal rift russia the tunka fault is a major normal oblique transform fault within the nne trending baikal rift that displays geomorphic evidence of recurrent quaternary movement a flight of six fanhead terraces of the kyngarga river is displaced by several parallel faults and has scarps up to 32 m high at arshan the main fault zone is exposed in an abandoned gravel quarry about 1 km east of the kyngarga river thirteen radiocarbon dates from the quarry a shallow trench in a graben and natural streamcuts constrain the timing of the latest two or three holocene paleoearthquakes the latest earthquake is bracketed by the 1024 1315 calendar years cal year b p age of an unfaulted terrace and by the 1947 2179 cal year b p age of a soil buried by scarp colluvium in the graben trench the penultimate earthquake is also relatively well constrained assuming that the displacement event slightly younger than 7091 7867 cal year b p in the upper quarry exposure is the same as the fissuring event slightly older than 6733 7385 cal year b p in the lower quarry exposure evidence for earlier event s between 9 2 12 7 ka depends on ambiguous stratigraphic evidence in the lower quarry exposure on the basis of only the two well dated earthquakes the recurrence interval at arshan may range from 2 9 to 6 8 ka for earthquake displacements of at least 1 3 m or a slip rate of 0 19 0 44 mm yr intermediate term 100 ka and long term circa 500 ka slip rates computed from terrace age estimates and fault scarp heights are 0 08 0 16 mm yr and 0 07 0 11 mm yr respectively rates that are considerably lower than the late holocene rate and the approximately 0 5 mm yr that might be inferred from the tectonic geomorphology of the tunka range front

morphotectonic evolution of two depressions at the southern border of the baikal rift system abstract detailed study of two dry depressions in the baikal rift system the e w khoito ghol tunka bistraya depression and the sw ne gusinoje ivolga depression aims to provide a better understanding of tectonic control on the intershoulder relief evolution after the rift opened both depressions are grabens and both feature a suite of 10 20 km wide basins alternating with more or less massive highs field and laboratory analysis shows that this pattern is of recent tectonic origin and that local breaking up and subsidence followed the general sinking which originally formed the grabens the subsidence belts seem to have gradually shifted north and northeastwards geomorphological analysis reveals that in both depressions the highs are remnants of a former pediment which was broken up the young basins display numerous relevant hydrographic anomalies of the secondary channels and a general water logging they also suggest that the subsidence belts have gradually shifted north and northeastwards in the gusinoje ivolga depression evidence was found of a plio pleistocene river course parallel to the selenga river which was later dismantled by the breaking up this depression parallel to the baikal rift and belonging to the mesozoic system of grabens in the caledonian fold belt seems to have been included into the general system of rifts during the pliocene tectonic phase as for the main hydrographic axes the selenga river was set on a palaeogene age planation surface before the first tectonic phase and kept its original course the irkut river flowed in the khoito gol tunka bistraya depression after the first tectonic phase and was not affected by the later breaking up in contrast the secondary drainage network is largely discordant despite their different geotectonic contexts the two depressions show a similar development of relief pattern which poses the question of the style of rift dynamics after the main pliocene tectonic phase

fan and playa areas in southern california and adjacent parts of nevada in bolsons in the desert regions of southern california and adjacent parts of nevada the area underlain by alluvial fan gravels and playa sediments is generally 1 2 times the area being eroded to produce those sediments in certain larger basins in the vicinity of death valley however the depositional area is only about half the size of the erosional area this reflects the more active tectonic environment in these bolsons of the areas underlain by recent sediments in these bolsons playas make up 2 6 per cent smaller playas are found in the mojave region and seem to be associated with sedimentary terranes conversely igneous terranes support larger playas larger deviations of playa area from these averages are attributable to incorrect identification of bolson boundaries fine sediment is either able to pass through the bolson to the next down stream or is being collected from areas upstream that were not considered to be part of the system for example the playa in death valley is unusually large this is in part because the death valley playa has been deformed tectonically so parts of it are now eroding and in part because the outlet of lake tecopa was downcut in the geologically recent past so sediment once trapped there now reaches death valley the size of the playa in death valley is still adjusting to these changes

morphotectonic analysis and 10 be dating of the kyngarga river terraces southwestern flank of the baikal rift system south siberia the formation of the baikal rift system basins is controlled by active faults separating each basin from the adjacent horsts the kinematics of these faults is mainly explored through investigation of complex sequences of the fault intersecting river terraces that record both tectonic and climatic events this study focuses on the northern margin of the major tunka basin that develops south west of lake baikal the development of the basin is controlled by the segmented tunka fault we performed a detailed mapping of the kyngarga river terraces the best preserved terraces staircase in baikal rift system at their intersection with the tunka fault in order to decipher the chronology of seismic events and the slip rates along that segment of the fault key terraces were dated using in situ produced cosmogenic 10be we demonstrate that the formation of the terrace staircase occurred entirely during mis1 mis2 the obtained data allowed us to estimate the rate of incision at different stages of the terrace staircase formation and the relationship between the vertical and horizontal slip rates along this sub latitudinal segment of the tunka fault making respectively 0 8 and 1 12 mm yr 1 over the past 12 5 ka analysis of the paleoseismology and paleoclimate data together with terrace dating provided the possibility to estimate the influence of tectonic and climatic factors on the terrace formation our proposed model of the kyngarga river terrace development shows that the incisions into terraces t3 and t6 were induced by the abrupt climatic warming episodes gi 1 and gi 2 respectively whereas terraces t5 t4 and t2 were abandoned due to the vertical tectonic displacement along the tunka fault caused by coseismic ruptures

faults and tectonic stresses of the baikal rift zone abstract the cenozoic baikal rift system consists of a central extensional segment which links a southwestern and a northeastern sinistral shear segment statistical studies on fault length amount and sense of slip depth of crustal penetration and spacing has led to the establishment of empirical relationships which appear to apply also for non extensional regimes results are graphically displayed in figs 4 7 tectonic stress regimes were determined by means of fault and joint analyses and on the basis of seismological data results of both approaches are compatible and explain the evolution of the baikal rift zone in terms of tensional reactivation of pre existing crustal discontinuities

accommodating large scale intracontinental extension and compression in a single stress field a key example from the baikal rift system the baikal rift system in southern siberia is one of the main intracontinental extensional features on earth the rift system represents the northwestern boundary of the amuria plate and in that respect can be considered as an evolving plate boundary the baikal rift system has been widely studied both in terms of geology and geophysics and many models have been proposed for its formation and evolution however the age of the initiation of deformation and the mechanism driving this deformation are still largely debated while major extension has occurred since the late miocene pliocene the onset of extension seems older than the india asia collision implying that several driving mechanisms may have acted together or in relay through time in this work we review the available data and models for deformation in an area encompassing the baikal rift system the sayan ranges to the west and the transbaikal to the east using a synthesis of this data and our own field and mapping observations we show that the baikal rift system along with transpressional deformation in the sayan ranges and transtension in the transbaikal area can be explained through major left lateral strike slip systems the deformation is strongly controlled by inherited crustal and lithospheric structures and is distributed over a wide area within the western amuria plate that consequently cannot be considered as a rigid block such distributed deformation is likely to have a strong effect on the structure of the future continental margin if extension evolves towards the formation of oceanic crust