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

formation and stability of transverse and longitudinal sand dunes the shape of dunes depends on the history of wind regimes and sand availability in deserts exposed to winds from two different directions but with comparable magnitude dunes are found to be linear ridges which are either perpendicular or parallel to the mean wind direction depending on the angle between the two wind directions these dunes respectively observed for small and large angles between winds are called transverse and longitudinal dunes in both cases their large width hundreds of meters and evolution time scale years strongly limit the investigation of their dynamics and thus our understanding of such structures here we show that under water similar structures can be obtained but at much smaller space and time scales performing controlled experiments together with numerical simulations we highlight the physical mechanisms at play in the formation and long term evolution of these structures we show in particular that while longitudinal dunes are stable and extend in time transverse dunes are unstable they evolve into wavy ridges and eventually break into barchans if the sand supply is too low this fundamental difference is understood through the study of single sand piles and bars exposed to two winds in the case of a large angle between winds a sand pile grows a finger pointing in the average wind direction and transforms into a longitudinal dune such an elongation does not occur for a small angle where a sand pile evolves into a barchan these results explain the morphological differences between straight and long longitudinal dunes and sinuous transverse dunes while giving keys to infer the wind history or pattern state of development from the observation of dune shapes in the field

glaciations of the west coast range tasmania geomorphic stratigraphic palynologic and 14c evidence indicates that the west coast range tasmania was glaciated at least three times during the late cenozoic the last or margaret glaciation commenced after 30 000 yr b p culminated about 19 000 yr b p and ended by 10 000 yr b p during this period a small ice cap ca 250 m thick and cirque and valley glaciers covered 108 km2 the glacial deposits show little chemical weathering or erosional dissection the snow line ranged from 690 to 1000 m with an average of 830 m for the ice cap mean temperature was 6 5 c below the present temperature during the preceding henty glaciation a 300 to 400 m thick ice cap and outlet glaciers exceeded 1000 km2 the glacial deposits are beyond 14c assay they are more weathered chemically and more dissected than margaret age deposits and the degree suggests a pre last interglaciation age 130 000 yr b p the snow line of the ice cap lay at 740 m and annual temperature was reduced by 7 c ice of the earliest linda glaciation slightly exceeded that of the henty glaciation but had a similar distribution the glacial deposits are intensely weathered have reversed magnetization and overlie a paleosol containing pollen of tertiary type an early pleistocene or tertiary age is indicated

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

late pleistocene landscape response to climate change eolian and alluvial fan deposition cape liptrap southeastern australia abstract sea cliffs along the western coast of cape liptrap at arch rock provide nearly continuous exposure of calcareous eolianites dated at 68 112 ka five optically stimulated luminescence osl ages calcareous eolian deposition began immediately after the last interglacial marine highstand oxygen isotope stage ois 5e and continued during sea level fall until the beginning of ois 4 west southwesterly winds transported calcareous sand across 12 km of exposed continental shelf by the beginning of ois 4 a brief period of cold arid windy continental climate with ephemeral but intense surface runoff immediately preceded the last glacial maximum lgm this resulted in fluvial reworking of the calcarenites into an alluvial fan dated at 23 25 ka four osl ages the fan overlies peat dated at 25 279 yr cal bp and is capped by a paleosol dated at 6010 yr cal bp concurrent eolian reworking by northwesterly winds of siliceous sediments on marine terraces along the eastern and central portion of cape liptrap formed siliceous longitudinal dunes with ages ranging from 19 to 24 ka five osl ages the phase of maximum landscape instability at cape liptrap coincides with solar insolation and air temperature minima and preceded the lgm by several thousand years

cryoturbation versus tectonic deformation along the southern edge of the tunka basin baikal rift system siberia new insights from an integrated morphotectonic and stratigraphic study the tunka basin is a broad emerging basin situated between the baikal lake to the east and the the hovsgol lake to the west the basin is bounded to the north and to the south by the tunka and the khamar daban mountain ranges respectively the tunka normal fault located at the southern foothills of the tunka mountain range is the main structure that controlled the development of the tunka basin during the neogene paleoearthquake surface ruptures attest of its present activity and show that its western and eastern terminations are undergoing a tectonic inversion characterized by left lateral reverse deformations the southern edge of the tunka basin is classically interpreted as being tectonically controlled in this paper we present the results of a geomorphological and stratigraphic analysis within its southwestern and southeastern parts suggesting that there is no active fault affecting the foothills of the khamar daban mountain range the different features observed in the quaternary deposits are interpreted to be the result of periglacial processes induced by alternating episodes of permafrost aggradation and degradation during the holocene our study concludes that the khamar daban range and the tunka basin are uplifting together and that the tunka and mondy faults are the two main triggers of regional earthquakes

active tectonics of an apparently aseismic region distributed active strike slip faulting in the hangay mountains of central mongolia summary we identify and describe a series of east west left lateral strike slip faults named the songinomargats the hag nuur the uliastay and the south hangay fault systems in the hangay mountains of central mongolia an area that has little in the way of recorded seismicity and which is often considered as a rigid block within the india eurasia collision zone the strikeslip faults of central mongolia constitute a previously unrecognized hazard in this part of mongolia each of the strike slip faults show indications of late quaternary activity in the form of aligned sequences of sag ponds and pressure ridges developed in alluvial deposits total bed rock displacements of 3 km are measured on both the songino margats and south hangay fault systems bed rock displacements of 11 km are observed across the hag nuur fault cumulative offset across the uliastay fault systems are unknown but are unlikely to be large we have no quantitative constraint on the age of faulting in the hangay the 20 km of cumulative slip on the hangay faults might at least in part be inherited from earlier tectonic movements our observations show that despite the almost complete absence of instrumentally recorded seismicity in the hangay this part of mongolia is cut through by numerous distributed strike slip faults that accommodate regional left lateral shear between siberia and china central mongolia is thus an important component of the india eurasia collision that would be overlooked in models of the active tectonics based on the distribution of seismicity we suggest that active faults such as those identified in the hangay of mongolia might exist in other apparently aseismic regions within continental collision zones

the anatomy of last glacial maximum climate variations in south westland new zealand derived from pollen records abstract we present pollen records from three sites in south westland new zealand that document past vegetation and inferred climate change between approximately 30 000 and 15 000 cal yr bp detailed radiocarbon dating of the enclosing sediments at one of those sites galway tarn provides a more robust chronology for the structure and timing of climate induced vegetation change than has previously been possible in this region the kawakawa oruanui tephra a key isochronous marker affords a precise stratigraphic link across all three pollen records while other tie points are provided by key pollen stratigraphic changes which appear to be synchronous across all three sites collectively the records show three episodes in which grassland interpreted as indicating mostly cold subalpine to alpine conditions was prevalent in lowland south westland separated by phases dominated by subalpine shrubs and montane lowland trees indicating milder interstadial conditions dating expressed as a bayesian estimated single best age followed in parentheses by younger older bounds of the 95 confidence modelled age range indicates that a cold stadial episode whose onset was marked by replacement of woodland by grassland occurred between 28 730 29 390 28 500 and 25 470 26 090 25 270 cal yr bp years before ad 1950 prior to the deposition of the kawakawa oruanui tephra milder interstadial conditions prevailed between 25 470 26 090 25 270 and 24 400 24 840 24 120 cal yr bp and between 22 630 22 930 22 340 and 21 980 22 210 21 580 cal yr bp separated by a return to cold stadial conditions between 24 400 and 22 630 cal yr bp a final episode of grass dominated vegetation indicating cold stadial conditions occurred from 21 980 22 210 21 580 to 18 490 18 670 17 950 cal yr bp the decline in grass pollen indicating progressive climate amelioration was well advanced by 17 370 17 730 17 110 cal yr bp indicating that the onset of the termination in south westland occurred sometime between ca 18 490 and ca 17 370 cal yr bp a similar general pattern of stadials and interstadials is seen to varying degrees of resolution but generally with lesser chronological control in many other paleoclimate proxy records from the new zealand region this highly resolved chronology of vegetation changes from southwestern new zealand contributes to the examination of past climate variations in the southwest pacific region the stadial and interstadial episodes defined by south westland pollen records represent notable climate variability during the latter part of the last glaciation similar climatic patterns recorded farther afield for example from antarctica and the southern ocean imply that climate variations during the latter part of the last glaciation and the transition to the holocene interglacial were inter regionally extensive in the southern hemisphere and thus important to understand in detail and to place into a global context

factors determining desert dune type while most observers recognize four elemental types of desert dunes longitudinal transverse barchan and star1 3 there is little agreement about which factors determine these types the angular relationships between the resultant of sand shifting winds and both the crest and principal slipfaces of the elemental types have been discussed qualitatively for many decades these relationships have been quantified but the wide range of dune types that combine the elemental forms and the juxtaposition of different dune types show that wind regime is not the only determinant for example sand availability has been considered important we have now quantified the importance of both wind regime and sand availability as determinants of dune type we show here that the four elemental types occur in areas uniquely defined by both the equivalent sand thickness of sediments held in the dunes and a measure of directional variability of sand moving winds wind strength does not appear to be important vegetation has an ambiguous role and the particle size of dune sediments is unimportant

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

luminescence studies of dunes from north eastern tasmania abstract northern tasmania has a geographically extensive cover of quaternary aeolian features and although the morphology and stratigraphy of many of these have been studied it is difficult to assign a reliable chronology because of the lack of material suitable for radiocarbon dating the dunes are primarily composed of quartz and hence are ideally suited for the application of luminescence dating in this paper a variety of luminescence techniques are applied to samples from the area analysis of the multiple aliquot osl measurements showed that a higher precision could be obtained using the signal from the initial 6 mj cm 2 of the optical stimulation rather than the total light sum the initial near exponential decay of the osl signal is highly reproducible from one sub sample to another but the later part of the osl decay curve which is dominated by retrapping effects is highly variable the multiple aliquot osl results are consistent with single aliquot additive dose results the luminescence ages show that the ainslie linear dunes were initially deposited by 44 ka were mobile again at 30 ka and have been subject to reworking within the last 100 200 years it appears that the quaternary history of aeolian activity in this area has been more complex than was previously thought

contributions of water supply from the weathered bedrock zone to forest soil quality one measure of forest soil quality is the ability of the soil to support tree growth in mediterranean type ecosystems such as most of california s forests there is virtually no rainfall during the summer growing season so trees must rely on water stored within the substrate water is the primary limitation to productivity in these forests many forest soils in california are relatively thin but are underlain by thick zones of weathered bedrock weathered granitic bedrock the most prevalent lithology has available water capacities 0 12 cm water cm rock that approach those of soils 0 2 cm water cm soil and because the weathered rock zone is usually so much thicker several meters than the soil 1 m it almost always constitutes the larger storage reservoir for plant available water the weathered bedrock retains the original rock fabric and is friable and easily excavated but the primary minerals are not thoroughly altered to clay minerals so it is not considered saprolite roots of ponderosa pine pinus ponderosa seedlings penetrate through the soil and encounter weathered bedrock within the first 2 years on many sites thus the influence of the weathered bedrock zone on plant growth begins early root access to the weathered bedrock is restricted to fractures which are often spaced about 50 cm apart water is extracted from the intervening rock matrix through unsaturated flow toward the root mat in the fractures and by mycorrhizal fungal hyphae that penetrate the rock matrix at one site in the sierra nevada 30 year old jeffrey pine p jeffreyi depleted the soil held water by mid june and relied on water stored in the weathered bedrock until the rainy season began in october in this case the weathered bedrock supplied at least 70 of the water used by the trees during the growing season in the same area we found that thin soils are not a detriment to pine productivity when they are underlain by a thick zone of weathered bedrock in mediterranean type ecosystems the weathered bedrock zone is an essential component of the plant water supply system and is thus an important contributor to forest soil quality

teleseismic traveltimes topography and the lithospheric structure across central mongolia 1 teleseismic travel times recorded along a 1000 km long n s transect across central mongolia are used together with topography and gravity data to constrain the deep lithospheric structure of this region time residuals appear positively correlated with the topography suggesting that p wave velocity changes correspond to density variations which in turn cause an isostatic uplift of the topography using a simple local isostasy model and a monte carlo inversion for the crust and asthenosphere velocities and density velocity conversion factors we determine best fitting moho and lithosphere asthenosphere boundary lab geometries which satisfyingly reproduce the observed topography and gravity data the model is validated using previously published 1d s wave velocity models obtained from receiver function analyses our results indicate that most of the long wavelength topography is supported by the asthenosphere buoyancy the hangai dome in the southern half of the transect appears mainly supported by a rather shallow 60 70 km asthenospheric uplift whereas the siberian platform at the extreme north of the profile is underlain by a very thick 200 km lithosphere misfits to the observed bouguer gravity anomaly occur near major faults probably because of lithospheric flexure

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

seismicity of the baikal rift system from regional network observations abstract in the paper we report the state of the art of seismicity study in the baikal rift system and the general results obtained at present the regional earthquake catalog for fifty years of the permanent instrumental observations consists of over 185 000 events the spatial distribution of the epicenters which either gather along well delineated belts or in discrete swarms is considered in detail for different areas of the rift system at the same time the hypocenters are poorly constrained making it difficult to identify the fault geometry clustered events like aftershock sequences or earthquake swarms are typical patterns in the region moreover aftershocks of m 4 7 earthquakes make up a quarter of the whole catalog the maximum magnitude of earthquakes recorded instrumentally is mlh7 6 for a strike slip event in the ne part of the baikal rift system and mlh6 8 for a normal fault earthquake in the central part of the rift system lake baikal basin predominant movement type is normal faulting on ne striking faults with a left lateral strike slip component on w e planes in conclusion some shortcomings of the seismic network and data processing are pointed out

late pleistocene to holocene slip rates for the gurvan bulag thrust fault gobi altay mongolia estimated with 10be dates 1 we surveyed morphotectonic markers along the central part of the gurvan bulag thrust a fault that ruptured with the bogd fault during the gobi altay earthquake 1957 m 8 3 to document climatic and tectonic processes along the fault for the late pleistoceneholocene period the markers were dated using 10 be produced in situ two major periods of alluviation ended at 131 20 and 16 4 8 ka these appear to be contemporaneous with global climatic changes at the terminations of marine isotope stages mis 6 and 2 the vertical slip rates determined from offset measurements and surfaces ages are 0 14 0 03 mm yr over the late pleistocene holocene and between 0 44 0 11 and 1 05 0 25 mm yr since the end of the late pleistocene the higher of these slip rates for the last 16 kyr is consistent with paleoseismic investigations along the fault prentice et al 2002 and suggests that at the end of late pleistocene the fault evolved from quiescence to having recurrence intervals of 4 0 1 2 kyr for surface ruptures with 4 m vertical offset similar to that of 1957 the inferred recurrence interval is comparable to that of the bogd fault 3 7 1 3 kyr suggesting that the two faults may have ruptured together also earlier during the last 16 kyr index terms 7221 seismology paleoseismology 1208 geodesy and gravity crustal movements intraplate 8110 1824 hydrology geomorphology 1625 7230 seismology seismicity and seismotectonics 8107 tectonophysics continental neotectonics keywords late pleistocene holocene thrust fault slip rate 10be dating mongolia

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

paleostress reconstructions and geodynamics of the baikal region central asia part 2 cenozoic rifting abstract investigations on the kinematics of rift opening and the associated stress field present a renewed interest since it has recently been shown that the control of the origin and evolution of sedimentary basins depends to a large extent on the interplay between lithospheric strength and applied stresses it appears that changes of stress field with time are an important factor that either controls or results from the rifting process the object of this paper is to study the changes of fault kinematics and paleostress field with time in the baikal rift system during the cenozoic reduced paleostress tensors were determined by inversion from fault slip data measured in the central part of the rift and its southwestern termination between 1991 and 1995 results show that the stress field varies as well in time as in space two major paleostress stages are determined corresponding broadly to the classical stages of rift evolution late oligocene early pliocene and late pliocene quaternary the first paleostress stage is related to the rift initiation and the second to the major stage of rift development similarities between the recent paleostress field and the present day stress field inverted from focal mechanisms indicate that the second paleostress stage is still active therefore we propose to use proto rift for the late oligocene early pliocene stage and active rift for the late pliocene quaternary stage of rift development during the proto rift stage the stress field was characterized by a compressional to strike slip regime a progressive change from transpression to transtension is suspected for the central part of the rift baikal and barguzin basins during this period in the western termination of the rift sayan massif tunka depression a strongly compressional stress field with oblique thrusting kinematics is well constrained in the late miocene early pliocene interval the active rift stage was initiated by a marked change in fault kinematics and stress regime in the late pliocene in the central part of the rift the stress regime changed into pure extension while in the southwestern extremity it changed into pure strike slip fault kinematics suggests that rifting was initiated by an extrusion mechanism due to the interaction of far field compressional stress on a mechanically heterogeneous crust with the southwards pointing wedge of the siberian craton acting as a passive indentor the cenozoic time space evolution of the stress field is believed to reflect the increasing influence of locally generated buoyancy extensional stresses associated with density anomalies of the lithosphere on intraplate stresses generated by the india eurasia convergence and the west pacific subduction

terrestrial dunes man and the late quaternary environment in southern tasmania abstract three source bordering sand sheets that occur adjacent to the derwent estuary and were occupied by aboriginal groups have been examined two lunette sites in the tasmanian midlands one occupied by aboriginals the other not have also been examined geomorphologic stratigraphic pedologic and archaeologic evidence is used to decipher the broad sequence of late quaternary environmental changes and the effects of occupation a broadly parallel sequence of changes is suggested by the two areas the data suggest that relatively cold dry climatic conditions prevailed during the late last glacial stage 25 000 10 000 b p and that more humid conditions preceded and succeeded this period the aeolian landforms and events compare with similar forms and events recorded from se mainland australia

late quaternary erosion events in lowland and mid altitude tasmania in relation to climate change and first human arrival abstract the establishment of a chronology of landscape forming events in lowland and mid altitude tasmania essential for assessing the relative importance of climatic and human influences on erosion and for assessing present erosion risk has been limited by the small number of ages obtained and limitations of dating methods in this paper we critically assess previous tasmanian studies list published radiocarbon ages considered to be dependable present new radiocarbon and thermoluminescence tl ages for 25 sites around tasmania and consider the evidence for the hypotheses that erosion processes at low and mid altitudes have been 1 purely climatically controlled and 2 influenced both by climatic and anthropogenic increased fire frequency effects a total of 94 dependable finite ages calibrated for radiocarbon and as measured for tl and optically stimulated luminescence osl determinations are listed for deposits comprising dunes colluvium alluvium and loess like aeolian deposits two fall in the 100 ka period 15 fall in the period 65 35 ka and 77 fall in the period 35 0 3 ka there was a sustained increase in erosion recorded in the period 35 15 ka as reflected by a greater number of dated aeolian deposits during this period we considered three possible biases that may have affected the age distribution obtained the limitations of radiocarbon dating sampling bias and preservation bias sampling bias may have favoured more recent dune strata but radiocarbon dating and preservation biases are unlikely to have significantly distorted the age distribution obtained long but intermittent aeolian deposition is recorded at two sites southwood b c 59 28 ka and dunlin dune c 29 14 ka but there is no evidence of regional loess deposits such as found in new zealand the timing of increased erosion in tasmania between 35 and 30 ka approximately coincides with the intermittent ten fold increase of dust accumulation between 33 and 30 ka in the antarctic dome c ice core the absence of widespread erosion before 35 ka the abrupt increase of erosion around this time the frequent association of erosion products with charcoal the arrival of people in tasmania at c 40 cal ka and the known use of fires by aborigines to maintain areas of non climax vegetation suggest that ecosystem disturbance by anthropogenic fires in a drier climate than that presently prevailing may have contributed to erosion in lowland and mid altitude tasmania after 35 ka thus the tasmanian erosion record provides circumstantial support for the proposition that human dispersal in southeast australia was accompanied by significant ecological change

stress field associated with the rupture of the 1992 landers california earthquake and its implications concerning the fault strength at the onset of the earthquake we investigate the space and time history of the shear stress produced on the fault during the 1992 landers earthquake the stress is directly calculated from the tomographic image of slip on the fault derived from near source strong motion data the results obtained shed some light on why the earthquake rupture cascaded along a series of previously distinct fault segments to produce the largest earthquake in california in over 40 years rupture on the 30 km long northernmost segment of the fault was triggered by a large dynamic increase of the stress field of the order of 20 to 30 mpa produced by the rupturing of the adjacent fault segments such a large increase was necessary to overcome the static friction on this strand of the fault unfavorably oriented in today s tectonic stress field this misorientation eventually led to the arrest of rupture the same mechanism explains why rupture broke only a small portion of the johnson valley fault on which the earthquake originally started before jumping to an adjacent fault more favorably oriented we conclude from these results that the dynamic stress field could not sustain and drive the rupture along the strongly misoriented nw se strands of the preexisting fault system instead the dynamic stress field produced new fractures favorably oriented in a n s direction and connecting parts of the old fault system

recharge mode and mineralization of groundwater in a semi arid region sidi bouzid plain central tunisia groundwater is the most important source of water supply in sidi bouzid plain located in central tunisia proper understanding of the geochemical evolution of groundwater is important for sustainable development of water resources in this region a hydrogeochemical survey was conducted on the mio plio quaternary aquifer system using stable isotopes radiocarbon tritium and major elements in order to evaluate the groundwater chemistry patterns and the main mineralization processes occurring in this system the chemical data indicate that dissolution of evaporate minerals and evaporation are the main processes controlling groundwater mineralization the isotopic data show that groundwater in the study area is a mixture of recent shallow waters located upstream and along wadi al fakka bed and paleowaters located towards plain limits and discharge areas low 3h and 14c contents are observed in major part of the plain indicating that recharge of the aquifer occurs mainly through direct infiltration at wadi al fakka while there is no evidence of significant recharge in major part of the plain and mountains piedmonts

late cenozoic transpression in southwestern mongolia and the gobi altai tien shan connection the gobi altai region of southwestern mongolia is a natural laboratory for studying processes of active transpressional intracontinental mountain building at different stages of development the region is structurally dominated by several major e w left lateral strike slip fault systems the north gobi altai fault system is a seismically active right stepping left lateral strike slip fault system that can be traced along the surface for over 350 km the eastern two thirds of the fault system ruptured during a major earthquake m 8 3 in 1957 whereas degraded fault scarps cutting alluvial deposits along the western third of the system indicate that this segment did not rupture during the 1957 event but has been active during the quaternary the highest mountains in the gobi altai are restraining bend uplifts along the length of the fault system detailed transects across two of the restraining bends indicate that they have asymmetric flower structure cross sectional geometries with thrust faults rooting into oblique slip and strike slip master faults continued ne directed convergence across the fault system coupled with left lateral strike slip displacements will lead to growth and coalescence of the restraining bends into a continuous sublinear range possibly obscuring the original strike slip fault system this may be a common mountain building process the largely unknown gobi tien shan fault system is a major left lateral strike slip fault system 1200 km long that links the southern ranges of the gobi altai with the barkol tagh and bogda shan of the easternmost tien shan in china active scarps cutting alluvial deposits are visible on satellite imagery along much of its central section indicating quaternary activity the total displacement is unknown but small parallel splays have apparent offsets of 20 km suggesting that the main fault zone has experienced significantly more displacement field investigations conducted at two locations in southwestern mongolia indicate that late cenozoic transpressional uplift is still active along the fault system the spatial relationship between topography and active faults in the barkol tagh and bogda shan strongly suggests that these ranges are large coalescing restraining bends that have accommodated the fault s left lateral motion by thrusting oblique slip displacement and uplift thus from a mongolian perspective the easternmost tien shan formed where it is because it lies at the western termination zone of the gobi tien shan fault system the gobi tien shan fault system is one of the longest fault systems in central asia and together with the north gobi altai and other smaller subparallel fault systems is accommodating the eastward translation of south mongolia relative to the hangay dome and siberia these displacements are interpreted to be due to eastward viscous flow of uppermost mantle material in the topographically low e w trending corridor between the northern edge of the tibetan plateau and the hangay dome presumably in response to the indo eurasian collision 2500 km to the south

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

the record of continental dust from australia in tasman sea sediments abstract the flux of aeolian dust from australia to sediments of the tasman sea has increased during glacial stages of the last four glacial cycles low fluxes of dust from australia before 350 ka were followed by an increase in stage 10 and high fluxes in peak glacial periods thereafter the initiation of higher dust fluxes in stage 10 is consisten with previous estimates of the age of onset of aridity in the source area dust flux to the tasman sea is thought to record the intensity of deflation from the source area in interior southeastern australia which was marked by arid conditions and possibly greater windiness during the last glacial a transect of five cores from the central tasman sea revealed consistently low dust fluxes north of 33 s increasing southward to approximately 40 s glacial to interglacial movement of the northern boundary of the dust plume governed by the position of the subtropical ridge was less than 6 latitude probably closer to 3 350 km the position of the dust plume determined in this study and its response to climate change are significantly different from a previous reconstruction based on the measurement of quartz content of the non biogenic sediment fraction

earthquake depth distributions in central asia and their relations with lithosphere thickness shortening and extension this paper examines the relationship between seismogenic thickness lithosphere structure and rheology in central and northeastern asia we accurately determine earthquake depth distributions which reveal important rheological variations in the lower crust these variations exert a fundamental control on the active tectonics and the morphological evolution of the continents we consider 323 earthquakes across the tibetan plateau the tien shan and their forelands as well as the baikal rift ne siberia and the laptev sea and present the source parameters of 94 of these here for the first time these parameters have been determined through body wave inversion the identification of depth phases or the modelling of regional waveforms lower crustal earthquakes are found to be restricted to the forelands in areas undergoing shortening and to locations where rifting coincides with abrupt changes in lithosphere thickness such as the ne baikal rift and w laptev sea the lower crust in these areas is seismogenic at temperatures that may be as high as 600 c suggesting that it is anhydrous and is likely to have great long term strength lower crustal earthquakes are therefore a useful proxy indicating strong lithosphere in places that are too small in areal extent for this to be confirmed independently by estimating effective elastic thickness from gravity topography relations the variation in crustal rheology indicated by the distribution of lower crustal earthquakes has many implications ranging from the support of mountain belts and the formation of steep mountain fronts to the localization and orientation of rifting in combination these processes can also be responsible for the separation of the front of the thin skinned mountain belts from their hinterlands when continents separate

pliocene to quaternary deformation in south east sayan siberia initiation of the tertiary compressive phase in the southern termination of the baikal rift system the south east sayan area wof the lake baikal is subjected to a very complex tectonic setting where the extensional stress field of the baikal rift system meets the compressional stress field generated by the india asia collision further south using satellite images aerial photographs srtm dem field mapping of geomorphological structures and published neotectonics and geological data we show that most of the relief in the se sayan initiated during late pliocene pleistocene through compressive reactivation of inherited structures by late quaternary clockwise rotation of the compressive field generated strike slip faulting and local secondary extension still within a general compressional stress field we demonstrate that the formation of the small scale extensional basins within the east sayan range is not linked to general the extension in the baikal rift system nor to a possible asthenospheric plume acting at the base of the crust but rather to the rotation of small rigid tectonic blocks driven by the compression

late quaternary aeolianites palaeosols and depositional environments on the nepean peninsula victoria australia abstract the nepean peninsula is a bay mouth bar near melbourne it is comprised of late quaternary aeolianites palaeosols and calcretes tl dates show that most of the sands from which the aeolianites developed as mobile sand dunes were deposited during times of low sea level towards 47 and 23 ka bp and others during times of relatively high sea level towards 118 ka bp aeolian dust mantles were laid down during brief intervals when aeolianite formation had ceased incipient soil formation and minor organic staining of the upper 0 3 0 5 m of the dust mantles points to a lull in dune formation and the temporary development of a widespread plant cover the dust mantles have tl ages of 118 57 54 51 and 47 ka bp indicating that apart from the 118 ka mantle most of the deposition was when sea level was low and the regional climate was drier windier colder and under a more continental climatic regime during times of glacially lower sea level the coastal climate in this region was not invariably cold dry and windy but was punctuated by brief intervals of milder moister and less windy conditions during which dunes and dust mantles became vegetated and soils began to form rapid climatic fluctuations were coeval with aeolianite deposition during times of very low sea level

morphotectonic and paleoseismological studies of late holocene deformation along the primorsky fault baikal rift abstract the baikal rift is the largest cenozoic continental rift in asia and has developed at the boundary between the siberian craton and a collage of microplates composing the amurian lithospheric plate gps data show that the amurian plate moves southeastward at a rate of 3 4 mm yr with respect to stable eurasia but the slip rates along the main faults that control the opening of basins within the baikal rift system are still poorly quantified the recent graben system of the olkhon region of the central baikal rift is a key example for studying of synrift faulting we discovered a previously unknown paleoseismic structure in the course of our morphometric study of the primorsky fault scarp one of the youngest grabens within the baikal rift detailed topographic mapping of the deformation area and trenching across the fault scarp revealed two paleoseismic events responsible for scarp formation dating of organic remnants found in the trench walls allowed us to estimate a late holocene age for the paleoearthquakes and bracket the vertical slip rates along the primorsky fault to between 0 5 0 1 mm yr min and 0 9 0 2 mm yr max over the last 2 5 kyr the geomorphological and paleoseismological data in combination with the analysis of recent seismicity and horizontal geodetic rates suggest that the primorsky fault has accumulated elastic stress with the potential for a m 6 6 earthquake large earthquakes of this magnitude have occurred at least twice on the investigated fault segment during the last 1 4 kyr

post glacial sea level changes around the australian margin a review abstract it has been known since rhodes fairbridge s first attempt to establish a global pattern of holocene sea level change by combining evidence from western australia and from sites in the northern hemisphere that the details of sea level history since the last glacial maximum vary considerably across the globe the australian region is relatively stable tectonically and is situated in the far field of former ice sheets it therefore preserves important records of post glacial sea levels that are less complicated by neotectonics or glacio isostatic adjustments accordingly the relative sea level record of this region is dominantly one of glacio eustatic ice equivalent sea level changes the broader australasian region has provided critical information on the nature of post glacial sea level including the termination of the last glacial maximum when sea level was approximately 125 m lower than present around 21 000 19 000 years bp and insights into meltwater pulse 1a between 14 600 and 14 300 cal yr bp although most parts of the australian continent reveals a high degree of tectonic stability research conducted since the 1970s has shown that the timing and elevation of a holocene highstand varies systematically around its margin this is attributed primarily to variations in the timing of the response of the ocean basins and shallow continental shelves to the increased ocean volumes following ice melt including a process known as ocean siphoning i e glacio hydro isostatic adjustment processes several seminal studies in the early 1980s produced important data sets from the australasian region that have provided a solid foundation for more recent palaeo sea level research this review revisits these key studies emphasising their continuing influence on quaternary research and incorporates relatively recent investigations to interpret the nature of post glacial sea level change around australia these include a synthesis of research from the northern territory queensland new south wales south australia and western australia a focus of these more recent studies has been the re examination of 1 the accuracy and reliability of different proxy sea level indicators 2 the rate and nature of post glacial sea level rise 3 the evidence for timing elevation and duration of mid holocene highstands and 4 the notion of mid to late holocene sea level oscillations and their basis based on this synthesis of previous research it is clear that estimates of past sea surface elevation are a function of eustatic factors as well as morphodynamics of individual sites the wide variety of proxy sea level indicators used their wide geographical range and their indicative meaning some progress has been made in understanding the variability of the accuracy of proxy indicators in relation to their contemporary sea level the inter comparison of the variety of dating techniques used and the nuances of calibration of radiocarbon ages to sidereal years these issues need to be thoroughly understood before proxy sea level indicators can be incorporated into credible reconstructions of relative sea level change at individual locations many of the issues which challenged sea level researchers in the latter part of the twentieth century remain contentious today divergent opinions remain about 1 exactly when sea level attained present levels following the most recent post glacial marine transgression pmt 2 the elevation that sea level reached during the holocene sea level highstand 3 whether sea level fell smoothly from a metre or more above its present level following the pmt 4 whether sea level remained at these highstand levels for a considerable period before falling to its present position or 5 whether it underwent a series of moderate oscillations during the holocene highstand

basin evolution in a folding lithosphere altai sayan and tien shan belts in central asia abstract central asia is a classical example for continental lithospheric folding in particular the altay sayan belt in south siberia and the kyrgyz tien shan display a special mode of lithospheric deformation involving decoupled lithospheric mantle folding and upper crustal folding and faulting both areas have a heterogenous crust with a long history of accretion collision subsequently reactivated as a far field effect of the indian eurasian collision thanks to the youthfulness of the tectonic deformation in this region peak deformation in late pliocene early pleistocene the surface expression of lithospheric deformation is well documented by the surface topography and superficial tectonic structures a review of the paleostress data and tectono stratigraphic evolution of the kurai chuya basin in siberian altai zaisan basin in kazakh south altai and issyk kul basin in kyrgyz tien shan suggests that they were initiated in an extensional context and inverted by a combination of fault controlled deformation and flexural folding in these basins fault controlled deformation alone appears largely insufficient to explain their architecture lithospheric buckling inducing surface tilting uplift and subsidence also played an important role they form typical basins in a folding lithosphere flb their characteristic basin fill and symmetry inner structure folding wavelength and amplitude thermal regime time frame are examined in relation to basement structure stress field strain rate timing of deformation and compared to existing modelling results

the eco geomorphological roles of rocky deep crevices for water supply on arid zone mountain slopes case study mehriz yazd iran rocky slope landscapes are widely distributed on arid land mountains where there are many restoration and forestation project sites this study has surveyed the role of deep crevices and stone layers for supplying water to establish trees and shrubs on arid lands rocky slopes the research was concentrated on the layers of limestone granite and andesite in central iran thirty transects each 25 m long were randomly laid out throughout the studied lithologic units correlation of vegetation cover percentage and abundance of trees were studied along with crack dimensions including width depth and length categorized into three classes large medium and low sizes along those transects the amount of ec ph organic materials caso4 caco3 soil texture n p k and soil moisture content in the cracks were also measured the results showed significant differences p 0 05 among crack properties vegetation cover and life forms in the study units also the vegetation cover and life forms have positive significant relationships with increase of crevice width as well as length and depth of each lithologic unit the findings demonstrated that the inherent potential of limestone rocky slopes with deep layers is higher than other rocky units for restoration and afforestation in this arid region

late quaternary extraglacial cold climate deposits in low and mid altitude tasmania and their climatic implications abstract many tasmanian deposits previously described as periglacial have been described in more detail re interpreted and dated we suggest that periglacial has little meaning when applied locally and the term relict cold climate deposits is more appropriate in this paper we examine the origin and age of relict cold climate slope deposits fan alluvium and aeolian sediments in tasmania and infer the conditions under which they accumulated fan alluvium dating from the penultimate glacial ois 6 and capped by a prominent palaeosol deduced to date to the last interglacial ois 5e is present at woodstock south of hobart many fan deposits formed before 40 ka or in a period c 30 23 ka only a few deposits date to the last glacial maximum in tasmania which is defined as spanning the period 23 5 17 5 ka slope deposits indicate widespread instability down to present day sea level throughout the last glacial probably as a result of freeze thaw in a sparsely vegetated landscape layered fine gravel and coarse sand colluvial deposits resembling grezes litees produced both by dry deposition and by the action of water are locally common where jointed siltstone bedrock outcrops these deposits occur from altitudes of 500 m to near sea level and also in caves and must have formed under sparse vegetation cover probably by freeze thaw in extremely dry conditions they have been radiocarbon dated from 35 to 17 5 cal ka relict dunes and sandsheets are widespread at the margin of the bassian plain that once provided a land bridge between tasmania and the mainland they are also found in western tasmania and in areas of inland southern tasmania that now support wet eucalypt forest and rainforest and receive mean annual rainfall 1500 mm in the south they have been dated 87 5 19 ka and attest to a long period of semi arid climate in an area extending well to the west and south of the present semiarid zone we deduce that during most of the last glacial anticyclones dominated tasmania s climate and rain bearing depressions generally passed south of the land mass however in the east prominent palaeosols in aeolian deposits dated between 26 4 ka and 16 ka at different locations and palaeosols with morphology indicating formation under humid conditions indicate periods of wetter climate in eastern tasmania during or close to the lgm deduced to be the result of easterlies associated with near coastal depressions in the western tasman sea such easterlies may also be responsible for short last glacial wet periods noted at mainland coastal sites a plot of ages of all dated deposits reveals an increase of erosion and deposition between 35 and 20 ka and greater prevalence of aeolian deposits in the 35 15 ka period than earlier in the last glacial there are two possible explanations for this pattern 1 that aeolian activity increased as the result of climatic effects e g increased windiness or 2 that shrubland biomass increased after the megafauna were hunted to extinction following human arrival c 40 ka causing increased fire frequency and in the cold dry climate of the late last glacial such fires caused increased erosion and increased aeolian accumulation

the effect of weathering on pore geometry and compressive strength of selected rock types from turkey weathering processes cause important changes in rock porosity besides porosity distribution of pore sizes is significant for the identification of changes due to rock weathering and its effects on fabric the formation of secondary porosity in different types of rock taken from different parts of turkey was examined and the results are presented in this paper the aim of this study was to observe changes in porosity due to weathering effective porosity mercury intrusion porosimetry and optical and scanning electron microscopy were used to evaluate the changes in pore geometry of the rocks additionally the dry density water absorption and uniaxial compressive strength of the rocks at different weathering stages were determined analysis of experimental data showed that microstructure of the rocks in relation to weathering is the main feature which controls their physical and mechanical properties the study revealed that fabric characteristics particularly the pore and fracture geometry are very important characteristics for assessment of the behaviour of weathered rock

aeolian and fluvial evidence of changing climate and wind patterns during the past 100 ka in the western simpson desert australia abstract sediments near finke in central australia provide evidence of late quaternary evolution and the interaction of aeolian and fluvial systems in response to changing climate in the western simpson desert thermoluminescence tl dating is used to develop a chronology of aeolian and alluvial activity and to identify differences in sand provenance quaternary alluviation in the finke valley at this location occurred at or prior to c 90 ka and with no surviving evidence of subsequent activity until the holocene in contrast to rivers in the eastern part of the lake eyre basin substantial alluviation took place here in the early to mid holocene probably due to reactivation of the northern monsoon and its partial penetration into central australia the regional dunefield near finke consists of linear dunes largely reworked and aligned during the last glacial 30 12 ka as part of the great anticlockwise whorl of dunes in central australia the oldest dated source bordering dunes from the finke river are bright red in colour were deposited at c 100 ka and are now buried beneath paler source bordering dunes the latter consist of two exposed units a lower one of unknown orientation that dates at 17 9 ka and an upper unit aligned to the northwest and parallel to the prevailing winds that dates at 5 0 ka the tl signature and sediment texture of the oldest source bordering dunes show them to have probably been derived from weathered alluvial red beds of similar or greater age nearby and to have contributed abundant sand to the regional dunefield immediately north of the river in contrast sand from the younger paler source bordering dunes appears to be from a different source and to have only recently extended into the regional field the finke region would seem to be in a pivotal position for the study of palaeowind patterns that have created and modified australia s whorl of continental dunes the 30 18 ka regional linear dunes near finke are oriented almost due north their cross sectional asymmetry steeper eastern slopes suggests a response to southwesterly or westerly sand transporting winds between 18 and 10 ka these winds appear to have shifted to their present southeast orientation during the past 5 ka from dune ages alignments and asymmetry it is proposed here that there was a northward shift in the wind pattern at finke by about 100 150 km 1 1 5 of latitude during the last glacial but that through this period the regional dune pattern has remained remarkably stable

a reappraisal of the 1950 mw 6 9 mondy earthquake siberia and its relationship to the strain pattern at the south western end of the baikal rift zone the precise nature of the transition between the present day compressional tectonics in central mongolia and extensional deformation in the central baikal rift has still to be determined for that purpose we have built a comprehensive earthquake focal mechanism data base for the mongolia southern siberia area from which we map the variations of the stress field we focus our detailed investigations on the largest seismic event in the transition zone the 1950 mw 6 9 mondy earthquake for which several discordant focal mechanisms have been proposed using a new approach in source inversion we resolve the focal mechanism left lateral strike slip type on a steep south dipping fault and depth 14 3 km of the mondy earthquake with a satisfactory accuracy this seismological information combined with the geological observations allows us to decipher the connections between the 1950 mainshock the local stress tensor and the active faults which strongly suggest a partitioning of the deformation between two faults namely the mondy and ikhe ukghun faults

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

soil development on dolerite and its implications for landscape history in southeastern tasmania abstract soil genesis has been examined using field description particle size distributions chemical properties mineralogy and elemental distributions of five soil profiles developed on dolerite on mt nelson and tolmans hill near hobart in tasmania the soils form a sequence ranging from a black vertosol p8 to four texture contrast soils namely a eutrophic brown chromosol p5 two mottled subnatric grey sodosols mn8 and p4 and a mottled mesonatric grey sodosol p7 the soil stratigraphic and pedological relationships of these soils have been investigated to help understand their distribution and improve understanding of soil formation history the knowledge of the soil stratigraphy and weathering features aided in the determination of the broader landscape history the field observations show the local dolerite has been subjected to both deep weathering and severe erosional periods pockets of deeply weathered dolerite occur adjacent to thin a c soils or hard outcropping rock deeper colluvial soil materials occur on lower slopes the presence of protruding dolerite columns now buried by transported clayey slope wash materials indicates partial landscape stripping followed by reburial the presence of buried stone lines separating the upper profile from the clayey subsoils supports the idea of a second major erosional depositional cycle a pronounced variation between the a and b horizons particle size distribution mineralogy and elemental distribution supports the conclusion that the modern soils are composed of several sedimentary layers which cap a variable thickness of in situ weathered dolerite termed mealy material above fresh dolerite bedrock jointing veins and rock fabric extend upward from the bedrock into the mealy material but are truncated abruptly at the contact with the clayey subsoil soil forming processes have operated to modify soil colours and mottling soil structure and cation chemistry these findings have important implications for landscape history slope processes and the improved understanding of the distribution of dolerite derived soils in tasmania

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

how do longitudinal dunes respond to climate forcing insights from 25 years of luminescence dating of the australian desert dunefields abstract this paper presents a meta analysis of 689 luminescence age estimates of australian desert sand dunes this analysis had two aims to examine the hypothesis that quaternary climate changes have forced dune accumulation and to understand longitudinal dune behaviour from the age architecture of sand dunes for which stratigraphic information is often absent or poorly known a novel approach to the analysis of probability density curves of dune age frequency shows that in the mallee dunefield of southeastern australia only the period leading up to and including the last glacial maximum lgm 18 34 ka experienced marked dune growth which cannot be explained by random stochastic activity during the lgm most but not all mallee longitudinal dunes were accumulating more rapidly than before and after in the strzelecki dunefield source bordering sbd longitudinal dune tl n 61 and osl n 40 ages are more frequent at the pleistocene holocene transition but nearby non sbd longitudinal dunes n 21 ages were only active above background levels during the lgm however the strzelecki dune age data set suffers from being drawn from a small number of individual dunes 10 sbd dated using tl 12 sbd dated by osl 7 non sbd dated by osl with a marked bias away from surficial young and basal old depths even during the lgm many dunes do not record active growth and the dunefield was most likely a mosaic of stable dune surfaces and bare mobile patches supported by the scant pollen data from the arid zone hyper aridity has not been experienced in these dunefields these vegetated dunes exhibit conservative behaviour with limited response to the range of climate forcing experienced in the late pleistocene a more complete understanding of dunefield response to quaternary climates would require an intensive and structured dating program to overcome the noise from stochastic processes leading to small scale activity in these dunes and the simultaneous removal of parts of the sedimentary record

reappraisal of the 1887 ligurian earthquake western mediterranean from macroseismicity active tectonics and tsunami modelling summary early in the morning of 1887 february 23 a damaging earthquake hit the towns along the italian and french riviera the earthquake was followed by a tsunami with a maximum run up of 2 m near imperia italy at least 600 people died mainly due to collapsing buildings this ligurian earthquake occurred at the junction between the southern french italian alps and the ligurian basin for such a historical event the epicentre and the equivalent magnitude are difficult to characterize with any degree of precision and the tectonic fault responsible for the earthquake is still under debate today the recent malisar marine geophysical survey allowed the identification of a large system of active faults we propose that the rupture of some of the segments belonging to this 80 km long northern ligurian faults system connected to a shallow dipping major thrust plane at depth was the source of the 1887 ligurian earthquake we investigated the macroseismic data from the sisfrance 08 and dbmi 04 historical databases using several models of intensity attenuation with distance and focal depth the modelling results are consistent with the off shore location with an epicentre around 43 70 43 78 n and 7 81 8 07 e and with a magnitude mw in the range of 6 3 7 5 numerous earthquake source scenarios have been tested on the tide gauge record at genoa harbour as a result we present seven characteristic source earthquake scenarios for a shallow strong earthquake occurring below the northern ligurian margin the modelled tide gauge records were analysed with the help of basic statistical tools and a simple harmonic analysis to extract the wave spectrum characteristics this analysis indicates that scenarios of a magnitude mw of 6 8 6 9 along a reverse n55 e striking fault are the best candidates to explain the known characteristics of the tsunami that followed the best fitting scenarios comprise a 70 dipping southward fault plane with mw 6 8 and a 16 dipping northward fault plane with mw 6 9 both with reverse kinematics taking into account the geometry of the active faults the location of the macroseismic epicentre and the morphotectonic evolution of the continental slope we propose that the 1887 ligurian earthquake corresponded to the reverse faulting of a n55 e striking fault plane dipping to the north with a coseismic slip of 1 5 m

catastrophic events in the quaternary outflow history of lake baikal abstract lake baikal is earth s deepest lake and an iconic site of scientific study this vast basin holds sedimentary archives of environmental change dating back to the miocene and its array of palaeoshorelines and surrounding relief record the past 1 3 ma of lake levels and outflows here we present an extensive review of previous work alongside a new set of observations concerning the quaternary development of lake baikal with special focus on lake level fluctuations and the formation and evolution of the lake s three known outlets the sequence of shoreline terraces indicates that lake levels were both higher and lower in the past lake baikal stood 200 m higher during the last interglacial i e marine isotope stage mis 5e and dropped to 40 m below present day during the last glacial maximum mis 2 the relative lake level variations reflect climate factors and gradual or sudden coseismic tectonic impacts on the elevation of the lake s outlet thresholds three successive outlets are known i the palaeo goloustnaya manzurka associated with the manzurka alluvium ii the palaeo irkut and iii the currently active angara river outlet we propose that the manzurka alluvium is the product of catastrophic events in lake baikal the sudden possibly coseismic collapse of the 15 3 km goloustnaya fault block into lake baikal triggered a mega tsunami that thrust overwash deposits across neighbouring drainage divides above lake baikal and the valleys of the goloustnaya manzurka river system the age of the manzurka alluvium remains poorly constrained but the mega tsunami is potentially traceable to an unconformity in drill core sediments at 0 8 1 0 ma although older late pliocene and younger 125 ka ages have also been proposed the irkut outlet existed between mis 6 and mis 5 when lake level was 200 m higher than present 640 650 masl and a large bay extended into the tunka rift at baikal s south west tip lake baikal retreated from the tunka rift when lake level fell by up to 100 m in early mis 5e we propose that the lake level fall is connected to a partial collapse of primorsky ridge at listvenichny bay which caused baikal to overspill into the angara river thereby forming a new outlet the release of a 4000 km3 megaflood down the angara river valley caused large scale modification and reworking of valley fills mis 5e at the end of mis 2 further collapse of primorsky ridge lowered the outlet threshold an additional 50 60 m and prompted a second megaflood down the angara river valley which left a widespread unconformity where horizontal bedded sands dated at 11 8 13 4 ka overlie cryoturbated deposits of the earlier megaflood the central role of catastrophic processes at lake baikal suggests that rather than being rare events coseismic landsliding and mega tsunami may be more frequent than hitherto recognised

hydrogeochemical investigation in an arid region of iran tabas central iran groundwater is the most important source of water supply in iran and understanding the geochemical evolution of groundwater is important for sustainable development of the water resources in tabas area a total of 29 samples of groundwater in tabas area have been analyzed for ions and major elements groundwater of the study area is characterized by the dominance of na cl water type groundwater was generally acidic to high alkaline with ph ranging from 5 42 to 10 75 the tds as a function of mineralization characteristics of the groundwater ranged from 479 to 10 957 mg l with a mean value of 2 759 mg l the ca2 mg2 so42 and hco3 were mainly derived from the dissolution of calcite dolomite and gypsum the cu pb and zn ions are not mobile in recent ph eh but these conditions controlled dissolved se v and mo in groundwater the as is released in groundwater as a result of the weathering of sulfide minerals like arsenopyrite

uplift age and rates of the gurvan bogd system gobi altay by apatite fission track analysis abstract the dating of the uplift onset of the mongolian mountain ranges the northernmost relief associated with the india eurasia convergence is a fundamental issue to better understand the mechanisms of propagation of the cenozoic transpressive deformation in central asia using apatite fission tracks we determined the timing and strain rates of the tectonics affecting the gurvan bogd system in the gobi altay since the middle mesozoic to the late cenozoic the region was firstly affected by a lower middle jurassic tectonic phase characterized by a vertical crustal movement larger than 2 km then followed a protracted period without major crustal vertical movements until the last uplift phase the peneplanation of the jurassic relief produced an erosional surface that has undergone negligible denudation or sedimentation for more than 100 ma this same surface corresponds to the present summit plateaux of the massifs standing about 2000 m above the surrounding region which corresponds to the vertical movement produced by the ongoing uplift modelling of fission track data from the massifs of ih bogd and baga bogd shows that this uplift phase probably started at 5 3 ma the gobi altay mountain range appears therefore as one of the youngest mountain ranges in central asia which is consistent with the idea of a northward propagation of the transpressional deformation from the himalayan front to the siberian craton the cenozoic uplift rate of the massifs is estimated to be between 0 25 and 1 mm yr which is slightly higher than the upper pleistocene vertical slip rates of the bordering faults this suggests that thrust faults observed within the massifs would increase the uplift rate inside the massifs compared to the uplift rate determined at their boundaries

man and megafauna in tasmania closing the gap abstract recent discussion on the late pleistocene extinction of the australian megafauna has revolved around interpretation of several key fossil sites in tasmania it has been suggested that humans did not arrive in tasmania until after the megafauna became extinct or did not hunt now extinct megafauna and therefore that humans cannot be implicated in the extinctions radiocarbon results from these sites indicate that the youngest extinct megafauna are close to charcoal ages from the oldest archaeological deposits although difficulties have arisen in establishing chronologies because most relevant sites have ages near the limit for radiocarbon analysis we report a series of new radiocarbon ages 13 c 15 n and c n ratios on collagen and dentine fractions from skeletal remains in the mount cripps karst area and the mowbray swamp both in northwestern tasmania and discuss the reliability of ages from these and other sites we also report the discovery of an articulated simosthenurus occidentalis skeleton at mt cripps that represents only the second directly dated extinct megafaunal taxon with a reliable age our results suggest that c n ratios measured on collagen or dentine are not an infallible guide to radiocarbon age reliability we confirm previous reports of a temporal overlap between the megafaunal and archaeological records in tasmania but the presence of archaeological evidence and megafauna with the same age at the same site has not yet been demonstrated at least two megafaunal taxa the now extinct protemnodon anak and a giant pleistocene form of the extant macropus giganteus were still present in tasmania after 43 ka when human crossing of the bassian landbridge from mainland australia first became sustainable

mass balance simulation and principal components analysis applied to groundwater resources essaouira basin morocco the water resources of the essaouira coastal basin west of marrakesh are characteristic of a semi arid climate and are severely impacted by the climate in terms of quantity and quality considering the importance of the essaouira aquifer in the groundwater supply of a vast region nearly 1 200 km2 a research study was conducted in order to better understand groundwater evolution in this aquifer system it is a coastal aquifer located on the atlantic coastline southern morocco and salinization problems have been reported covering the palaeozoic bedrock the sedimentary series range from the triassic to the quaternary besides the possibility of seawater intrusion problems the geological structures delineate a syncline bordered by the tidzi diapir of triassic age outcropping to the east and south this is a recharge area for the aquifer whereas the main groundwater flow direction is from se to nw towards the atlantic ocean in spite of the occurrence of calcareous and dolomitic levels all waters in the essaouira basin are of the na cl type based on a range of experimental methodologies combined with pca and geochemical modelling it was possible to identify the mineralization processes occurring in the groundwater system and the importance of the water rock interaction in the water chemistry scenarios were tested using a simple mass balance model through the phreeqc programme the reaction path was assumed to be such that waters observed at shallow depths evolved to more mineralized waters an important contribution of water rock interaction in groundwater mineralization was found corroborating the influence of preferential recharge from the tidzi diapir in the water s signature anthropogenic contamination was also identified and could lead to serious problems with groundwater degradation in the near future in a country with scarce water resources

are post seismic effects of the m 8 4 bolnay earthquake 1905 july 23 still influencing gps velocities in the mongolia baikal area summary gps measurement campaigns in the mongolia baikal area show that 1 the baikal rift zone is currently opening at 4 5 mm yr 1 in a nw se direction and 2 the western part of the amurian north china block is moving eastward relative to eurasia at 5 7 mm yr 1 these results are consistent with recent geodetic studies in asia and indicate that crustal motions in mongolia and north china derived from geodetic measurements are significantly faster than those proposed by most deformation models of asia using a numerical model we test whether post seismic deformation caused by viscoelastic relaxation in the lower crust following the tsetserleg bolnay earthquake sequence mw 7 9 and 8 4 1905 july can explain this discrepancy we find that surface velocities at the gps sites presented here for the 1997 2000 time period can reach 4 mm yr 1 depending on the earthquake source parameters and the rheology used in the models using a model based on our best current knowledge of lithospheric structure and rheology in the mongolia baikal area we find that the contribution of post seismic effects to the gps velocities presented here is less than 2 mm yr 1 for the mongolian sites and less than 1 mm yr 1 for the baikal sites we therefore conclude that the post seismic effects of the mw 8 4 1905 bolnay earthquake cannot explain why the gps derived crustal motions in mongolia and the baikal rift zone are significantly larger than those proposed by deformation models of asia this discrepancy must therefore be sought in processes not accounted for in most of these deformation models such as the farfield contribution of the pacific subduction zones and or the effect of gravitational forces on intracontinental deformation

groundwater flow and radioactivity in namaqualand south africa the namaqualand area is located in the northern cape province of south africa which is characterised by arid climate where groundwater is the only source of water supply for local communities extensive groundwater sampling was carried out in the area and the physico chemical parameters inorganic constituents stable isotopes and trace metals were measured the hydrochemistry of the area indicates dissimilar groundwater composition due to complex geochemical processes where groundwater flow takes place from catchment f30a to the catchment d82b and the chemistry is controlled primarily by redox reaction dissolution and mixing processes the br cl ratio revealed that the salinity in the area is derived from seawater mixing halite dissolution and atmospheric deposition sea aerosol spray under excessive evaporative condition due to climatic aridity groundwater salinity shows increasing trend isotope results show the presence of shallow weathered zone and deep fracture controlled circulating groundwater in the crystalline basement aquifer of the area in comparison to the south african water quality standard the results obtained for gross alpha activity which could be derived from uranium isotopes show that 41 of the reported data in the area fall above the drinking water limit

faulting within the eastern baikal rift as characterized by earthquake studies earthquake relocations focal mechanism determinations waveform modeling and stress analyses using focal mechanism information are used to examine the faulting processes within the western baikal rift 95 to 108 5 results of the study show that high angle dip 70 faulting is most likely to occur in the more youthful parts of the rift and is most likely to be associated with m 4 5 events like the eastern rift nearly all earthquakes occurred on faults dipping 30 suggesting that in no part of the rift is significant deformation occurring on low angle structures focal mechanism information does not indicate there is a sharp boundary to the western rift as observed in the eastern rift less normal faulting rakes 60 to 120 occurs in the western rift than the eastern rift waveform modeling of the two largest earthquakes 1950 mondy and 1959 srednebaikal in the western rift gives focal depths of 10 to 15 km the 1959 event appears to have occurred along the eastern boundary fault on lake baikal just to the north of proval bay a feature created a m 7 1 earthquake in 1862 the 1950 event may have occurred along the southern boundary fault of the tunka depression stress orientation information indicates a near horizontal nw se to wnw ese striking 3 in the eastern part of the western rift

historical earthquakes studies in eastern siberia state of the art and plans for future abstract many problems in investigating historical seismicity of east siberia remain unsolved a list of these problems may refer particularly to the quality and reliability of data sources completeness of parametric earthquake catalogues and precision and transparency of estimates for the main parameters of historical earthquakes the main purpose of this paper is to highlight the current status of the studies of historical seismicity in eastern siberia as well as analysis of existing macroseismic and parametric earthquake catalogues we also made an attempt to identify the main shortcomings of existing catalogues and to clarify the reasons for their appearance in the light of the history of seismic observations in eastern siberia contentious issues in the catalogues of earthquakes are considered by the example of three strong historical earthquakes important for assessing seismic hazard in the region in particular it was found that due to technical error the parameters of large m 7 7 earthquakes of 1742 were transferred from the regional catalogue to the worldwide database with incorrect epicenter coordinates the way some stereotypes concerning active tectonics influences on the localization of the epicenter is shown by the example of a strong 6 4 earthquake of 1814 effect of insufficient use of the primary data source on completeness of earthquake catalogues is illustrated by the example of a strong m 7 0 event of 1859 analysis of the state of the art of historical earthquakes studies in eastern siberia allows us to propose the following activities in the near future 1 database compilation including initial descriptions of macroseismic effects with reference to their place and time of occurrence 2 parameterization of the maximum possible magnitude unlimited number of historical earthquakes on the basis of all the data available 3 compilation of an improved version of the parametric historical earthquake catalogue for east siberia with detailed consideration of each event and distinct logic schemes for data interpretation thus we can make the conclusion regarding the necessity of a large scale revision in historical earthquakes catalogues for the area of study

palaeomagnetism of east siberian traps and kimberlites two new poles and palaeogeographic reconstructions at about 360 and 250 ma summary we studied basalt sills and dykes and kimberlite pipes from the eastern part of the siberian platform these are spread out over a few hundred kilometres and are divided into two age groups late permian early triassic mir aikhal and olenyek regions and late devonian early carboniferous viluy and markha basins aikhal region the palaeomagnetic poles determined for each sill or dyke are statistically different from each other but averaging all corresponding directions from these sills and dykes with those from kimberlites of different generations yields results with acceptable statistics this is probably due to the averaging out of secular variation and or changes in magnetic polarity the resulting palaeomagnetic poles allow one to reconstruct the palaeopositions of siberia during the two large flood basalt events at about 360 and 250 ma a significant rotation of the siberian platform during the devonian and carboniferous is suggested the new data are in general agreement with some earlier palaeomagnetic poles for the late permian early triassic traps of the tungusska basin and significantly reduce uncertainties for previous late devonian early carboniferous siberian poles which were very scattered together with geological and absolute age data the palaeomagnetic data support the hypothesis that kimberlite magmatism and trap intrusions were both rapid and relatively close in time the 360 ma event is emerging as a magmatic event with considerable extent over the russian and siberian platforms related to incipient continental break up and triple junction formation possibly at or near the time of the frasnian famennian mass extinction

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

recurrent holocene movement on the susitna glacier thrust fault the structure that initiated the mw 7 9 denali fault earthquake central alaska abstract we conducted a trench investigation and analyzed pre and postearthquake topography to determine the timing and size of prehistoric surface ruptures on the susitna glacier fault sgf the thrust fault that initiated the 2002 m w 7 9 denali fault earthquake sequence in central alaska in two of our three hand excavated trenches we found clear evidence for a single pre 2002 earthquake penultimate earthquake pe and determined an age of 2210 420 cal b p 2 for this event we used structure from motion software to create a pre 2002 earthquake digital surface model dsm from 1 62 800 scale aerial photography taken in 1980 and compared this dsm with postearthquake 5 m pixel interferometric synthetic aperature radar topography taken in 2010 topographic profiles measured from the pre earthquake dsm show features that we interpret as fault and fold scarps these landforms were about the same size as those formed in 2002 so we infer that the pe was similar in size to the initial m w 7 2 subevent of the 2002 sequence a recurrence interval of 2270 yrs and dip slip of 4 8 m yield a single interval slip rate of 1 8 mm yr the lack of evidence for pre pe deformation indicates probable episodic clustering behavior on the sgf that may be related to strain migration among other similarly oriented thrust faults that together accommodate shortening south of the denali fault we suspect that slip partitioned thrust triggered earthquakes may be a common occurrence on the denali fault system but documenting the frequency of such events will be very difficult given the lack of long term paleoseismic records the number of potential thrust earthquake sources and the pervasive glacial erosion in the region electronic supplement oxcal code and figures of topographic profiles across fault scarps reactivated during the 2002 denali fault earthquake oxcal models of published age constraints on tephra exposed at the wetfan trench site and map showing locations and data used to measure near surface dips of susanna glacier fault in the vicinity of the wetfan trench site

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