deep seated gravitational slope deformations related landslides and tectonics abstract deep seated gravitational slope deformations and their relationships with tectonic deformation of rocks is considered to examine the viewpoint of tectonics as a causative factor in slope deformation first a distinction is made between the different types of deep seated gravitational slope deformation then the geomorphological and structural effects of the different macrostructural deformations induced by tectonics on the scale of the whole deforming ridge is briefly discussed finally some case studies that represent either verified or possible cases of gravity deformation in response to tectonic activity are used as illustration

the ms 7 3 1992 suusamyr kyrgyzstan earthquake in the tien shan 2 aftershock focal mechanisms and surface deformation abstract the m s 7 3 suusamyr earthquake of 19 august 1992 was a large thrust type earthquake in the northern tien shan of kyrgyzstan an intracontinental mountain belt in central asia focal mechanisms of both the mainshock and 13 moderate sized aftershocks are consistent with a seismotectonic setting that is dominated by nnw sse horizontal compression which manifests itself in reverse faulting along roughly east west trending steeply dipping fault planes the earthquake produced surface faulting at two widely separated locations along two different fault segments the total length of which was less than 4 km detailed measurements at one of the locations indicate a net slip of at least 4 2 0 4 m a wide variety of secondary surface effects was observed in the macroseismic zone that extended over an area of 2500 km 2 the lack of extensive surface rupture from such a large event can be explained by a combination of 1 redistribution of the net slip at depth among the secondary splays that branches out from the main fault near the surface and 2 variable surface slip over the fault length the active deformation associated with this event documents a structural style that involves steeply dipping reverse faults extending from mid crustal depths to the surface at nearly uniform dip accommodating crustal shortening in the interior of the tien shan

rate of slip from multiple quaternary dating methods and paleoseismic investigations along the talas fergana fault tectonic implications for the tien shan range the 400 km long talas fergana fault is one of a series of major right lateral strike slip faults that cross the tien shan range this fault has been recognized as active in the late holocene and accommodates part of the deformation induced by the ongoing indo asian collision the kinematics and the role of this strike slip fault are poorly understood with no large earthquakes reported in the instrumental or historical catalogs and no well constrained geological slip rate estimates here we used high resolution satellite imagery to present a first detailed analysis of the fault segmentation we identified nine geometric segments based on strike variations for the talas fergana fault along the kyldau segment through morphological analyses of an offset alluvial fan and the application of multiple dating methods be 10 al 26 cl 36 luminescence and radiocarbon we calculated a late quaternary slip rate ranging from 2 2 to 6 3 mm year this rate is higher than the geodetic measurements but the discrepancy can be partly explained if the talas fergana fault accommodates shortening by counterclockwise rotation around a vertical axis paleoearthquakes identified by trenching indicate that at least two primary surface ruptures and possibly a third occurred in the past 3 800 years and that no large earthquake has ruptured the kyldau segment since at least 420 years b p possibly within the last 2 700 years making this fault segment a potential candidate to generate an earthquake with m 7 in the near future

the annual cycle in equatorial convection and sea surface temperature abstract the coupled atmosphere ocean system in the equatorial eastern pacific and atlantic exhibits a distinct annual cycle that is reflected in contrasting conditions at the times of the two equinoxes the contrasts are so strong that they dominate the annual march of zonally averaged outgoing longwave radiation for the equatorial belt the march equinox corresponds to the warm season when the equatorial cold tongues in the eastern pacific and atlantic are absent with the onset of summer monsoon convection over colombia central america and west africa in may june northward surface winds strengthen over the eastern pacific and atlantic the equatorial cold tongues reappear and the marine convection shifts from the equatorial belt to the intertropical convergence zones itczs along 8 n as the northern summer program the itczs remain strong and shift northward to new 10 n while sea surface temperature sst continues to drop over the cold tongues and the southern tropics perhaps in response to the

paleoenvironmental and paleohydrochemical conditions of dolomite formation within a saline wetland in arid northwest australia abstract groundwater dolocrete occurring within the fortescue marsh a large inland wetland in the pilbara region of northwest australia has been investigated to provide paleoenvironmental and paleohydrological records and further the understanding of low temperature dolomite formation in terrestrial settings over the quaternary period two major phases of groundwater dolocrete formation are apparent from the presence of two distinct units of dolocrete based on differences in depth 18o values and mineral composition group 1 g1 occurs at depth 20 65 m b g l below ground level and contains stoichiometric dolomite with 18o values of 4 02 0 71 group 2 g2 is shallower 0 23 m b g l occurring close to the current groundwater level and contains ca rich dolomite secondary calcite with a comparatively lower range of 18o values 7 74 and 6 03 modelled 18o values of paleogroundwater from which older g1 dolomite precipitated indicated highly saline source water which had similar stable oxygen isotope compositions to relatively old brine groundwater within the marsh developed under a different hydroclimatic regime the higher 18o values suggest highly evaporitic conditions occurred at the marsh which may have been a playa lake to saline mud flat environment in contrast g2 dolomite precipitated from comparatively fresher water and modelled 18o values suggested formation from mixing between inflowing fresher groundwater with saline brine groundwater within the marsh the 18o values of the calcite indicates formation from brackish to saline groundwater which suggests this process may be associated with coeval gypsum dissolution in contrast to the modern hydrology of the marsh which is surface water dependent and driven by a flood and drought regime past conditions conducive to dolomite precipitation suggest a groundwater dependent system where shallow groundwaters were influenced by intensive evaporation

why the itcz is mostly north of the equator abstract although the distribution of sunshine is symmetrical about the equator the earth s climate is not climatic asymmetries are prominent in the eastern tropical pacific and atlantic oceans where the regions of maximum sea surface temperature convective cloud cover and rainfall are north of the equator this is the result of two sets of factors interactions between the ocean and atmosphere that are capable of converting symmetry into asymmetry and the geometries of the continents that determine in which longitudes the interactions are effective and in which hemisphere the warmest waters and the intertropical convergence zone are located the ocean atmosphere interactions are most effective where the thermocline is shallow because the winds can readily affect sea surface temperatures in such regions the thermocline happens to shoal in the eastern equatorial pacific and atlantic but not in the eastern indian ocean because easterly trade winds prevail over the tropical atlantic and pacific wher

late quaternary slip rates across the central tien shan kyrgyzstan central asia 1 slip rates across active faults and folds show that late quaternary faulting is distributed across the central tien shan not concentrated at its margins nearly every intermontane basin contains neogene and quaternary syntectonic strata deformed by holocene north south shortening on thrust or reverse faults in a region that spans two thirds of the north south width of the central tien shan slip rates on eight faults in five basins range from 0 1 to 3 mm yr fault slip rates are derived from faulted and folded river terraces and from trenches radiocarbon optically stimulated luminescence and thermoluminescence ages limit ages of terraces and aid in their regional correlation monte carlo simulations that sample from normally distributed and discrete probability distributions for each variable in the slip rate calculations generate most likely slip rate values and 95 confidence limits faults in basins appear to merge at relatively shallow depths with crustal scale ramps that underlie mountain ranges composed of pre cenozoic rocks the sum and overall pattern of late quaternary rates of shortening are similar to current rates of north south shortening measured using global positioning system geodesy this similarity suggests that deformation is concentrated along major fault zones near range basin margins such faults separated by rigid blocks accommodate most of the shortening in the upper crust index terms 8107 tectonophysics continental neotectonics 9320 information related to geographic region asia 8010 structural geology fractures and faults

tectonics and seismicity of the toktogul reservoir region kirgizia ussr the 214 m high toktogul dam will impound a 19 5 km3 reservoir on the naryn river in central kirgizia the reservoir lies along the talas fergana fault a major tectonic feature of central asia the nature of cenozoic movements along the fault is in debate however there is considerable evidence of present day right lateral movement the region is one of moderate to high seismicity a magnitude 7 6 earthquake occurred in 1946 approximately 65 km from the dam near the intersection of the talas fergana fault and chatkal ranges construction of the dam was completed in 1975 and by late 1979 the water level in the reservoir reached three fourths its final planned depth low magnitude induced earthquakes began as the water level first exceeded 100 m in late 1977 a microearthquake survey using portable instruments was carried out in july august 1978 and a seven station telemetered network was installed in october 1978 the largest of the induced earthquakes has been of magnitude 2 5 the activity is in the immediate vicinity of the dam at very shallow depths 2 5 km and is related to water level preliminary analysis of data gathered during 1978 1979 shows a zone of activity extending to 5 km depth supporting geological evidence for an active reverse fault beneath the dam and parallel to the canyon of the naryn river where the reservoir crosses the talas fergana fault 15 km upstream from the dam the water level has not yet reached 100 m and seismicity along the talas fergana has not shown any significant change related to filling of the reservoir

influences of continental monsoons and air sea coupling on the climate of the equatorial pacific abstract an air sea land coupled model of intermediate complexity was used to reveal the important roles of air sea coupling and adjacent continental monsoons i e american monsoons and asian australian monsoons on the annual cycle and mean state of the equatorial pacific excluding the effects of adjacent continental monsoons the simulated mean sst in the western pacific displays a warm bias the sst seasonal cycle exhibits an erroneous dominant annual component in the western pacific and insufficient strength and a 2 month phase delay in the equatorial eastern pacific the air sea coupling alone cannot sustain the full strength of the annual marches of the itcz cold tongue complex this is because the diabatic heating associated with the itcz rainfall generates both a southerly and a westerly component to its equatorward side while the southerly cools the cold tongue establishing a positive feedback to enhance the itcz and the equatorial westerly favors cold tongue warming inducing a negative fe

ocean atmosphere interaction in the making of the walker circulation and equatorial cold tongue abstract the climate over the equatorial pacific displays a pronounced asymmetry in the zonal direction that is characterized by the walker circulation in the atmosphere and the cold tongue in the ocean an intermediate coupled ocean atmosphere model is used to investigate the driving force and the ocean atmosphere interaction mechanism for the generation of the zonal asymmetry in the far eastern pacific the upwelling at the equator is weak because zonal winds are blocked by the andes the off equatorial upwelling induced by southerly cross equatorial winds is thus crucial for cooling the eastern pacific a realistic cold tongue appears in the coupled model only when this southerly wind forcing is included the southerly winds cause the sea surface temperature to fall in the east enhancing the zonal heat contrast and hence intensifying easterly winds across the basin these anomalous easterlies induce more equatorial upwelling and raise the thermocline in the east amplifying the initial cooling by th

long term investigation of a deep seated creeping landslide in crystalline rock part i geological and hydromechanical factors controlling the campo vallemaggia landslide slope movements of the deep seated campo vallemaggia landslide in the southern swiss alps have been reported for over 200 years surface and borehole investigations of the unstable mass reveal an u

interannual variability in a tropical atmosphere ocean model influence of the basic state ocean geometry and nonlinearity abstract the behavior of a tropical coupled atmosphere ocean model is analyzed for a range of different background states and ocean geometries the model is essentially that of cane and zebiak for the tropical pacific except only temporally constant background states are considered here for realistic background states and ocean geometry the model solutions feature oscillations of period of 3 5 yr by comparing the full model solution with a linearized version of the model it is shown that the basic mechanism of the oscillation is contained within linear theory a simple linear analog model is derived that describes the nature of the interannual variability in the coupled tropical atmosphere ocean system the analog model highlights the properties that produce coupled atmosphere ocean instability in the eastern ocean basin and the equatorial wave dynamics in the western ocean basin that are responsible for a delayed negative feedback into this instability growth the growth rate of the local instabil

late palaeozoic to mesozoic kinematic history of the talas ferghana strike slip fault kyrgyz west tianshan as revealed by 40ar 39ar dating of syn kinematic white mica abstract the nw trending talas ferghana fault tff in kyrgyzstan central asia is one of the largest intracontinental strike slip faults in the world it extends over a distance of more than 2000 km from southern tourghai to western tarim and exhibits a maximum dextral offset of 200 km during the late palaeozoic to present the history of the fault provides important insights for the understanding of the evolution of southern central asia but remains poorly constrained due to lack of reliable geochronological data we present new ar ar ages and structural data from the kyrgyz west tianshan that elucidate the kinematic history of the tff in the palaeozoic and mesozoic 40ar 39ar ages on mylonitic white micas document a deformational history consisting of several episodes a late carboniferous age of 312 4 ma point to initiation of top to the south and dextral transpressional deformation during a metamorphic overprint in precambrian and palaeozoic rocks along the northern compartment of the tff the main phase of dextral motion along the entire fault occurred in the permian as suggested by minimum ages of 260 290 ma obtained at two different locations in the nw and central parts of the tff partial isotopic resetting occurred between 240 and 210 ma and younger ages of the ar ar mineral ages and structural data argue for a major phase of dextral shearing affecting the entire region from the west tianshan to mongolia in the late permian and leading to formation of almost equally spaced major nw trending dextral strike slip faults the uniform character of this deformation indicates that the process of amalgamation in this part of the caob ended prior to the late permian and central asia evolved as a single coherent continental block since that time

structural development and stress evolution of an arcuate fold and thrust system southwestern greater caucasus republic of georgia abstract the southern front of the greater caucasus is quite rectilinear in plan view with the exception of part of the rioni basin where marine and continental deposits of cretaceous neogene age were locally folded and uplifted this resulted in the formation of an arcuate fold and thrust system that extends 45 km into the foreland although previous studies suggested that this system has developed only since miocene times our new detailed and systematic field measurements of brittle and ductile structures show a very complex history consisting in four main phases of brittle deformation and folding dated from eocene to quaternary times we collected microtectonic data at 248 faults and calculated the related paleostress tensors the first two phases which we document here predated folding and were characterised by dominant transcurrent faulting and subordinate reverse motions the greatest principal stress 1 was perpendicular and later parallel to the mountain belt afterwards nw se e w and ne sw trending south vergent asymmetrical folds started to form in the western sector of the study area folds are sinuous in plan view whereas to the east they show a left stepping en echelon geometry another two brittle deformation phases took place after the folding due to the activity of a set of right lateral strike slip faults that strike nw se and ne sw respectively as well as by left lateral strike slip faults mostly striking nw se ne sw and nne ssw these two additional phases were produced by a ne sw to n s trending 1 the arcuate belt is marked by along strike variations in the tectonic regime and deformation geometry plus belt parallel stretching based on our field data integrated with published analogue models we suggest a possible explanation for the rioni structure in terms of the oblique asymmetric indentation of an upper crustal blocks moving to the ssw

source to sink dynamics in the kyrgyz tien shan from the jurassic to the paleogene insights from sedimentological and detrital zircon u pb analyses new insights in the mesozoic geodynamic evolution and related basin range interactions in the kyrgyz tien shan were obtained based on new sedimentological and detrital zircon u pb la icp ms results from jurassic to paleogene sedimentary sequences studied sedimentary sections are located in the fergana and yarkand fergana basins to the west of the talas fergana fault tff and in the issyk kul and ming kush kokomeren basins to the east the ages of the phanerozoic zircon grains found in 18 jurassic to paleogene sandstones can be divided into four groups caledonian 470 390 ma hercynian 315 260 ma triassic 250 210 ma and jurassic 190 160 ma ages the differences in sedimentation pattern and zircon u pb results suggest that the tff played an important role in the distribution of the sedimentary deposits in the mesozoic during the early middle jurassic the tff was active and the strongest subsidence occurred in the yarkand fergana basin the provenance of its sediments can be explained both by local sources close to the tff and by more distal sources to the south west probably stretching into the present day pamir during the late jurassic early cretaceous renewed compression led to the inversion of the yarkand fergana basin around the jurassic cretaceous transition large alluvial fans developing in a semi arid to arid climate traceable around the whole tien shan were also deposited in the fergana basin a mafic sill intruded within these alluvial fans provides an emplacement age of 144 8 ma apatite u pb indicating sub volcanic activity during the early cretaceous during the late cretaceous to early paleogene the area to the west of the tff experienced marine incursions related to the proto paratethys sea the dominance of caledonian ages in the upper cretaceous lower paleogene detrital samples indicates a change in provenance whereby the drainage areas became larger towards low relief land area east of the tff

low stable isotope ratios of tropical cyclone rains tropical cyclone rains have distinctly lower stable isotope ratios than rains in other tropical and summer precipitation systems with a mean value slightly above that of water vapor near the sea surface the isotope ratios also decrease radially inward to the eye wall but appear to be anomalously low even near the periphery of the rain shield these findings indicate that tropical cyclones are highly efficient precipitation systems and suggest the use of stable isotope ratios as dynamic tracers of a tropical cyclone s water and energy budgets

landslides triggered by earthquakes and their relations with faults and mountain slope geometry an example from ecuador abstract a large number of landslides occurred during two seismic events respectively 6 9 and 6 1 msw on 5 march 1987 in the ecuadorian andes these landslides have been mapped digitized and coregistered with topography at 1 50 000 scale geometry of coseismic and holocene faulting has been assessed integrating field and geophysical data landslide distribution and holocene tectonic features have been compared with earthquake foci geological deposits slope area inclination and orientation and vegetation cover the macro seismic field deduced by landslide distribution is ellipse shaped with the major axis striking nne and coinciding with the trend of the coseismic and holocene faults landslide distribution also shows a correlation with respect to the dip direction of these faults and the orientation of mountain slopes slopes parallel to the coseismic fault planes sloping towards wnw are almost unaffected by landsliding while this increases on the slopes at high angle to the fault plane and lying along its strike if these results could be confirmed in other areas a method of reconstruction of geometry of seismogenetic faults from topographic effects appears feasible

late cenozoic slip on the talas ferghana fault the tien shan central asia although cenozoic crustal shortening and thickening by thrust faulting have built the present tien shan active right lateral shear on the northwest trending talas ferghana fault appears to be the most rapid localized deformation in the belt ephemeral stream valleys have been offset right laterally tens of metres new and published radiocarbon dates of organic material deposited in depressions blocked by offset ridges place upper bounds on the average holocene slip rate at 18 localities uncertainties allow 14 upper bounds to overlap the range of 8 16 mm yr and 95 confidence limits on such bounds at 11 sites are entirely within this range we infer that the rate of 10 mm yr is not simply an upper bound but applies to the late holocene epoch although the bounds on rates permit more rapid slip in the northwest than the southeast they do not place a useful constraint on variations in slip rate along the fault offsets of paleozoic facies boundaries imply a total right lateral shear of 180 250 km but early cretaceous sedimentary rock appears to have been offset only 60 10 km published paleomagnetic declinations of cretaceous miocene rock demonstrate 20 30 of counterclockwise rotation of the ferghana valley which lies just west of the talas ferghana fault with respect to stable parts of eurasia and 20 11 with respect to the central tien shan east of the fault these declinations are consistent with a maximum northwestward translation of 70 210 km of the ferghana valley at the talas ferghana fault and therefore with a similar maximum horizontal shortening across the chatkal ranges which lie between the ferghana valley and the kazakh platform estimates of crustal thickness beneath the chatkal ranges however permit only 60 100 km of cenozoic shortening if 100 km of slip on the talas ferghana fault accumulated at a constant rate of 10 mm yr it would imply an initiation of slip more recently than ca 10 ma long after india collided with the rest of eurasia

propagation of strike slip faults across holocene volcano sedimentary deposits pasto colombia this study contributes to the understanding of shear failure development on the basis of macroscopic field data collected in latest pleistocene holocene pyroclastic and fluvio lacustrine deposits in the pasto valley sw colombia here there is a pervasive system of microfaults and joints right lateral strike slip microfaults strike n0658 whereas left lateral strike slip microfaults strike n1208 three main joint sets strike n n0658 and n0208 in decreasing order of frequency stress computation gives a horizontal s1 trending wn0608 and a horizontal s3 trending wn1508 consistent with earthquake focal mechanisms and stress inversion of main faults synthetic shears dominate resulting from nucleation of older cracks in the basement cropping out northeast of pasto the ne to ene striking buesaco aranda and pasto faults show evidence of latest pleistocene holocene right lateral strike slip motions the structures in the pasto valley can be interpreted as a mode iii damage zone representing the up dip propagation of the main faults across the young volcano sedimentary deposits q 2005 elsevier ltd all rights reserved

earthquake induced landslides and their effects on alluvial fans abstract earthquakes as small as magnitude 4 0 may dislodge landslides from susceptible slopes and larger earthquakes can generate tens of thousands of landslides throughout areas of hundreds of thousands of square kilometers producing billions of cubic meters of loose surficial sediment these landslides can have significant geomorphic effects that vary depending on the landslide characteristics and materials and on the settings in which the landslides occur a review of data from historical earthquakes indicates that the landslides they generated can be classified into 14 different types these include highly disaggregated and fast moving falls disrupted slides and avalanches more coherent and slower moving slumps block slides and earth slides and lateral spreads and flows that involve partly to completely liquefied material rock falls disrupted rock slides and disrupted slides of earth and debris are the most abundant types of earthquake induced landslides whereas earth flows debris flows and avalanches of rock earth or debris typically transport material the farthest because of their abundance or long distances of transport these landslides generally have the greatest effects on the landscape during and after earthquakes landslide effects on alluvial fans include direct deposition of material on fan surfaces fissuring and displacement of fan materials alterations in drainage basins such as devegetation denudation and changes in channel networks and generation of large amounts of sediment that may be transported to fans by post earthquake water flows or debris flows

gravel deposits on the margins of the qinghai xizang plateau and their environmental significance abstract the thick deposits of quaternary gravels found along the margins of the qinghai xizang tibet plateau have been studied for decades here we concentrate on two sediment series widely developed along the kunlun tian shan and qilian mountains the xiyu formation a molassic series of lower pleistocene age and the middle and upper pleistocene gobi gravels these two series with their contained fossil assemblages throw light on the question of the mean altitudes and uplift rates of the tibetan plateau during the quaternary and on the related problem of the vigour and penetration of advected summer monsoonal moisture into central asia the sedimentary series on the northern piedmonts of the tibetan plateau considered here challege the view that plateau uplift accelerated in the upper pleistocene they indicate that the plateau had reached mean altitudes in the range 4000 5000 m perhaps by the end of the lower pleistocene and certainly by the middle pleistocene this diminished the incursion of southerly monsoonal moisture and so imposed arid and semi arid conditions across much of a vast region north of the plateau which among other effects precluded widespread mountain glaciation in the lower pleistocene and general ice sheet glaciation of the tibetan plateau as a whole

uav based surveying in volcano tectonics an example from the iceland rift abstract in the present work we applied the use of an unmanned aerial vehicle uav a quadcopter and the aerial structure from motion digital photogrammetry image processing technique asfm to study volcano tectonics and tectonic features in an active icelandic rift data have been collected in order to evaluate the holocene deformation in the northern volcanic zone of iceland we mapped 397 structures mainly related to extension fractures and subordinately normal faults in the theistareykir fissure swarm obtaining 1098 and 21 structural data respectively this allowed to reconstruct an overall spreading direction of n108 during holocene times and to calculate a stretch of 1 013 regarding 8 10 ka old lava units deformation in the area is related to both dyke intrusions and extensional tectonics furthermore detailed geological structural field and uav surveys were also performed in two test areas in order to determine data accuracy and the associated reliability of this approach in addition to the above different flight heights were tested suggesting that photo collection with a 12 4 mpx camera at 100 m is efficient to study fracture dilation and kinematics

chemical openness and potential for misinterpretation of the solute environment of coastal sabkhat abstract sabkha deposits in the geologic record are commonly used to interpret the environmental conditions of deposition implicit in this use is the assumption that the solute system is chemically closed that is the authigenic minerals represent the composition of the fluids in their environment of origin thermodynamic and mass balance calculations based on measurements of water and solute flux of contemporary abu dhabi coastal sabkha system however demonstrate that the system is open for sodium and chloride where nearly half of the input is lost but closed for sulfur where nearly 100 is retained sulfur and chloride isotopes were consistent with this observation if these sabkha deposits were preserved in the geologic record they would suggest a solute environment rich in sulfate and poor in chloride yet the reverse is true in most coastal sabkha environments capillary forces bring solutes and water to the surface where the water evaporates and halite carnallite sylvite and other soluble minerals are precipitated retrograde minerals such as anhydrite calcite dolomite and gypsum however precipitate and accumulate in the capillary zone beneath the surface of the coastal sabkha because they possess relatively low solubility and are below the surface these retrograde minerals are protected from dissolution and physical erosion occurring from infrequent but intense rainfall events thus they are more likely to be preserved in the geological record than highly soluble minerals formed on the surface

stable isotope and hydrochemical evolution of groundwater in the semi arid hamersley basin of subtropical northwest australia summary the hamersley basin in the semi arid pilbara region of northwest australia is currently subject to increasing pressure from altered hydrology associated with mining activities as well as water abstraction for regional development sustainable water management across the region must be underpinned by an understanding of the factors that constrain water supply in arid zones we measured the amount and isotopic signature of individual rainfall events over three consecutive years 2009 2011 to determine the likely processes that control surface water pools in streams and groundwater recharge across the hamersley basin we also measured concentrations of ions in particular bromide and chloride to define and quantify sources of major recharge stable isotope composition of precipitation across the basin forms a local meteoric water line lmwl defined by the equation 2h 7 03 0 17 18o 4 78 1 45 thus the slope of the lmwl was similar to the global meteoric water line gmwl however the intercept of the lmwl was significantly different to the gmwl which is attributable to the amount or rainout effect the stable isotope composition of rainfall events was highly variable and dependent on event size however the 2h and 18o values of fresh groundwater from the alluvium and fractured aquifers were similar and characterised by a very narrow range alluvium aquifer 18o 8 02 0 83 2h 55 6 6 0 n 65 fractured aquifer 18o 8 22 0 70 2h 56 9 5 0 n 207 our findings suggest that intense rainfall events of 20 mm with limited evaporation prior to infiltration contribute most to recharge in contrast the 2h and 18o values and chemical composition of the relatively saline groundwater in the terminal fortescue marsh suggest a combination of evaporation and cyclic drying and wetting of the marsh surface prior to recharge saline groundwater samples were more 18o enriched than fresh groundwater 2h and 18o values shifted to the right of the lmwl forming a straight line with a slope of 3 58 0 20 and an intercept of 25 55 0 71 r2 0 95 p

the water balance equations in saline playa lakes comparison between experimental and recent data from quero playa lake central spain abstract the quero playa lake is an ephemeral saline playa lake located in the la mancha region of central spain in this study a daily monitoring of the brine physical properties water activity brine depth and main climatic parameters was simultaneously carried out together with determining the precipitation sequence of minerals field data were compared with the results of simulating the water evaporation in an environmental chamber in this simulation a similar hydrochemical composition for the saline lake was used and the main climatic parameters temperature and humidity were controlled the water balance equation for saline lakes has usually been described using the wood and sanford equation econ geol 85 1990 1226 1235 our experimental results required us to revise the water balance equation for the brine depth variations dh dt that may be expressed as follows d h d t p 1 k a b a l s i s o h d where p mm is the precipitation k is the drainage coefficient of the lake al is the lake surface ab is the drainage basin surface si and so are the contribution of influent and effluent seepage to the depth of brine in the lake the term is the evaporation condensation defined as kpw aw rh where k is the mass transfer coefficient dalton s equation pw is the water pressure in equilibrium with the air aw is the water activity of the brine rh is the relative humidity the other terms h and d correct the brine depth loss or and gain a consequence of hydrated saline mineral precipitation and early diagenetic hydration dehydration reactions as a consequence of the above we suggest that the water balance equation for saline lakes can be an important consideration in the interpretation of their evolution the precipitation of hydrated saline minerals and the early diagenetic dehydration hydration reactions imply changes in the dh dt curves as a result the interpretation of the sequence of primary saline minerals in older evaporitic deposits may be used as a paleoenvironmental marker

stoichiometric saturation tests of nacl1 xbrx and kcl1 xbrx stoichiometric saturation is examined as a possible control on br contents of halite and sylvite during precipitation from binary salt solutions of nacl nabr and kcl kbr respectively experimental data at 25 c assumed to represent stoichiometric saturation were used to predict mole fractions of nabr in halite and kbr in sylvite in thermodynamic equilibrium with fluids as a function of aqueous activity ratios of br cl the predictions are based on the additional assumption that the aqueous activity product of the major salt component in the precipitated salt was independent of the trace br content in the salt lattice the extension of the predictions to diagenetic pressures and temperatures is discussed the predicted equilibrium br content of halite at initial halite saturation of evaporating seawater is in close agreement with that computed from the distribution coefficient of lutz 1975 measured in slowgrowth single crystal experiments fluid recrystallization of halite and sylvite at near surface temperatures is predicted to generally deplete the br contents in the solids bulk br contents in halite in cap rock of gulf coast salt domes generally agree with those predicted by the recrystallization of halite in the presence of evaporative concentrated seawater at a constant solution composition increasing temperature results in increasing the equilibrium br content of halite making less efficient br depletion in halite by recrystallization

geochemical and climate modeling evidence for holocene aridification in hawaii dynamic response to a weakening equatorial cold tongue abstract a 13 5 m sequence of holocene limnic sediments from a sinkhole on oahu hawaii provides a valuable paleoclimatic record for the central subtropical pacific 13 c analysis of plant leaf waxes n alkanes n c 27 n c 29 n c 31 and n c 33 is used to infer vegetative changes average 13 c values of the suite of n alkanes increase from approximately 31 0 5 at 10 ca kyr bp calibrated thousand years before present to about 27 0 5 by 6 ca kyr bp and then remain roughly constant until the polynesian arrival about 1 15 ca kyr bp the increase in 13 c values of n alkanes is interpreted to indicate a shift in the local vegetation from c 3 to c 4 dominated flora based on mass balance calculations the observed increase in the 13 c values translates to at least a doubling of the relative abundance of c 4 plants we argue that the expansion of c 4 plants was a response to decreased overall water availability aridification due to reduced wintertime precipitation model simulations of an orbitally induced increase in insolation along the equator during the holocene provide evidence for a wintertime drying trend in the eastern subtropical north pacific this trend is associated with boreal fall to winter warming of the cold tongue in the eastern equatorial pacific eep these model results provide a conceptual framework to explain a dynamic link between the reconstructed holocene drying trend in hawaii and orbitally forced climate change in the eep that is analogous to the modern el nino southern oscillation teleconnection

seismic moments of major earthquakes and the rate of shortening across the tien shan three twentieth century earthquakes that richter assigned m 8 and two of comparable magnitude in the nineteenth century imply rapid deformation within the tien shan seismic moment tensors of major earthquakes in this century suggest an average shortening rate of 7 2 mm yr 1 across the tien shan in the western part however where three of the five largest earthquakes occurred the calculated rate is consistent with the value of 20 mm yr 1 measured using gps in that area by abdrakhmatov et al as avouac et al suggested the high rate in the western part apparently is a manifestation of counter clockwise rotation of the tarim basin relative to eurasia about an axis near the east end of the tien shan

quaternary deformations along the engadine gruf tectonic system swiss italian alps the engadine line el is a seismically active fault in southeastern switzerland in the field we studied its western segment presently not affected by seismicity but characterised by features suggesting neotectonic motions and the coterminous gruf line uphill and downhill facing scarps offset rivers non equilibrium hydrological conditions and aligned deep seated gravitational slope deformations are dominant in the western sector of the el in the inn valley landform offsets and the most recent fault striations point to oblique left lateral strike slip close to the el at the maloja pass a huge collapse beheaded the inn valley trench excavation with palaeoseismic analysis stratigraphic correlations of quaternary deposits and optically stimulated luminescence dating indicate that the collapse and faulting mostly occurred in the late pleistocene in the bregaglia valley the gruf line stretches along the southwestern extension of the el six deep seated gravitational slope deformations developed along the gruf line and were dated to pre and post last glacial maximum times we suggest that the western sector of the el moved also in a pleistocene time interval during which tectonic forces in the area were probably larger than at present favouring local uplift widespread gravity deformation and retrogressive slope failure at the inn valley head copyright 2007 john wiley sons ltd

morphometry of late pleistocene holocene faulting and volcanotectonic relationship in the southern andes of colombia diffuse seismicity and the active galeras volcano characterize the southern andes of colombia whose inhabitants are prone to a high natural risk we used field geological structural and quantitative morphological data to define the geometry and kinematics of late quaternary faults and the volcanotectonic relationships in this area the main ne sw buesaco fault has a late pleistocene holocene 29 km rupture length offset of dated landforms yields 188 13 m of horizontal right lateral long term cumulative component of slip the vertical component of uplift of the nw block being 67 12 m the long term net slip rate is 1 48 0 12 mm yr the other main structure here named aranda fault also strikes ne sw and is 13 km long offset of landforms yields 160 10 m of horizontal right lateral long term component of slip and 3 9 1 9 m of vertical component of uplift of the nw block the long term net slip rate is 1 19 0 08 mm yr on the galeras edifice e w to nw se faults have normal motions and slip rates from 0 02 to 0 23 mm yr both the galeras and a late pleistocene pyroclastic cone lie along the ideal extension of the buesaco fault magma uprising in the crust can occur along the ne striking fractures when magma pressure mp is greater than the normal to fault component of tectonic 1 magma uprising in the uppermost crust i e in the cone can occur by rock cracking along e w planes with mp 3 up to nw se planes with mp greater than shear stress component of the horizontal greatest principal stress hmax

hydrochemical and stable isotope indicators of pyrite oxidation in carbonate rich environment the hamersley basin western australia abstract sulphur s is a commonly occurring element in most aquifers primarily in oxidised sulphates and reduced sulphides forms sulphides often constitute a risk to groundwater quality due to acid rock drainage especially in catchments that are subject to mining excavations or groundwater injection however in semi arid regions detection of the acid rock drainage risk can be challenging and traditional methods based on observations of increasing so 4 concentrations or so 4 cl ratios in surface and groundwater are not necessarily applicable in addition decreasing ph usually accompanying pyrite oxidation can be masked by the high ph neutralisation capacity of carbonate and silicate minerals analysis of 73 surface and groundwater samples from different water bodies and aquifers located in the hamersley basin western australia found that most of the samples are characterised by neutral ph but there was also a large spatial variability in the dissolved sulphate so 4 concentrations that ranged from 1 mg l to 15 000 mg l not surprisingly groundwater in aquifers that contained pyrite had high sulphate concentrations 1000 mg l this was associated with low 34 s so4 values 1 2 to 4 6 and was consistent with the values obtained from aquifer matrix pyritic rock samples 1 9 to 4 4 it was also found that the so 4 concentrations and acidity levels were not only dependent on 34 s so4 values and existence of pyrite but also on the presence of carbonate minerals in the aquifer matrix the groundwater in aquifers containing both pyrite and carbonate minerals had a neutral ph and was also saturated with respect to gypsum and had high magnesium concentrations of up to 2200 mg l suggesting de dolomitisation as the process buffering the acidity generated by pyrite oxidation based on the findings from this study a classification scheme has been developed for identification of the acid rock drainage contribution to groundwater that encompasses a myriad of geochemical processes that occur in aqueous systems the classification uses five proxies so 4 so 4 cl si of calcite 34 s so4 and 18 o so4 to improve assessment of the oxidation of sulphide potential contribution to overall sulphate ion concentrations regardless of acidity levels of the aqueous system

isotopic and hydrologic responses of small closed lakes to climate variability comparison of measured and modeled lake level and sediment core oxygen isotope records abstract simulations conducted using a coupled lake catchment isotope mass balance model forced with continuous precipitation temperature and relative humidity data successfully reproduce within uncertainty limits long term i e multidecadal trends in reconstructed lake surface elevations and sediment core oxygen isotope 18 o values at castor lake and scanlon lake north central washington error inherent in sediment core dating methods and uncertainty in climate data contribute to differences in model reconstructed and measured short term i e sub decadal sediment i e endogenic and or biogenic carbonate 18 o values suggesting that model isotopic performance over sub decadal time periods cannot be successfully investigated without better constrained climate data and sediment core chronologies model reconstructions of past lake surface elevations are consistent with estimates obtained from aerial photography simulation results suggest that precipitation is the strongest control on lake isotopic and hydrologic dynamics with secondary influence by temperature and relative humidity this model validation exercise demonstrates that lake catchment oxygen isotope mass balance models forced with instrumental climate data can reproduce lake hydrologic and isotopic variability over multidecadal or longer timescales and therefore that such models could potentially be used for quantitative investigations of paleo lake responses to hydroclimatic change

the ms 7 3 1992 suusamyr kyrgyzstan earthquake 1 constraints on fault geometry and source parameters based on aftershocks and body wave modeling we investigated the suusamyr kyrgyzstan earthquake of 19 august 1992 using aftershock data teleseismic body wave modeling and field observations aftershocks were recorded by the iris kyrgyzstan broadband network a temporary six station aftershock network and a regional network operated by the kyrgyz institute of seismology the aftershocks which range in depth from the surface to 18 km defined a 50 10 km long rupture zone that dips 50 13 to the south and strikes roughly east west the base of the eastern end of the aftershock zone shallowed to the east along strike and may represent a lateral ramp the surface ruptures also had an east west strike and dipped south but the total length less than 4 km was much shorter than the aftershock zone a teleseismic body wave inversion using a point source and a directivity correction yields a focal mechanism with a strike of 221 dip of 46 and a slip of 43 we obtained a moment of 4 1 1019 n m with a centroid depth between 5 and 21 km the rupture propagated along an azimuth of 330 60 which matches the relative location of the mainshock with respect to the aftershock zone the results of the aftershock study and teleseismic inversion yield a clear picture of the fault geometry of a large thrust earthquake

a coupled theory of tropical climatology warm pool cold tongue and walker circulation abstract based on results from analytic and general circulation models the authors propose a theory for the coupled warm pool cold tongue and walker circulation system the intensity of the coupled system is determined by the coupling strength the local equilibrium time and latitudinal differential heating most importantly this intensity is strongly regulated in the coupled system with a saturation level that can be reached at a modest coupling strength the saturation west east sea surface temperature difference and the associated walker circulation corresponds to about one quarter of the latitudinal differential equilibrium temperature this regulation is caused primarily by the decoupling of the sst gradient from a strong ocean current the author s estimate suggests that the present pacific is near the saturation state furthermore the much weaker walker circulation system in the atlantic ocean is interpreted as being the result of the influence of the adjacent land which is able to extend

the landslide response of alpine basins to post little ice age glacial thinning and retreat in southwestern british columbia abstract the role of post little ice age lia neoglacial retreat on landslide activity is investigated in 19 alpine basins along the upper lillooet river valley british columbia we examine how neoglacial scouring and glacial recession have modified hillslope form and slope stability and construct a decision making flowchart to identify landslide hazards associated with glacial retreat this work is based on field mapping gis analysis statistical associations between landslides and terrain attributes and a comparison between neoglaciated and non neoglaciated terrain within each basin the bedrock landslide response to glacial retreat varies appreciably according to lithology and the extent of glacial scour below the lia trimline valleys carved in weak quaternary volcanics show significant erosional oversteepening and contain deep seated slope movement features active rock fall rock slides and rock avalanches near glacial trimlines basins in stronger granitic rock rarely show increased bedrock instability resulting from post lia retreat except for shallow seated rock slides along some trimlines and failures on previously unstable slopes in surficial materials landslides associated with post lia retreat originate in till or colluvium as debris slides or debris avalanches and are concentrated along lateral moraines or glacial trimlines significant spatial association was also observed between recent catastrophic failures gravitational slope deformation and slopes that were oversteepened then debuttressed by glacial erosion eight out of nine catastrophic rock slope failures occurred just above glacial trimlines and all occurred in areas with a previous history of deep seated gravitational slope movement implying that this type of deformation is a precursor to catastrophic detachment

ocean atmosphere interaction and the tropical climatology part i the dangers of flux correction abstract this sequence of papers examines the role of dynamical feedbacks between the ocean and the atmosphere in determining features of the tropical climatology a stripped down intermediate coupled ocean atmosphere model is used to provide a prototype problem for the pacific basin here the authors contrast the fully coupled case with the case where flux correction is used to construct the climatology in the fully coupled case the climatology is determined largely by feedback mechanisms within the ocean basin winds driven by gradients of sea surface temperature sst within the basin interact with the ocean circulation to maintain sst gradients for all realistic cases these lead to a unique steady solution for the tropical climatology in the flux corrected case the artificially constructed climatology becomes unstable at sufficiently large coupling leading to multiple steady states as found in a number of coupled models using continuation methods we show that there is a topological change i

the role of soil organic matter in the geochemical cycling of chloride and bromide abstract chloride to bromide ratios were determined for rainfall in western australia and groundwaters and surface waters from a number of catchments in western australia victoria and queensland the ratio in rainfall though showing a large short term scatter on average reflected the ratio in ocean water groundwaters and surface waters often showed characteristic differences in cl br presumably associated with the cycling of bromide through soil organic matter to prove this association it is shown that in the leachate of saturated small columns of soil the cl br ratio is governed by chloride and bromide released from decomposing organic matter on leaching the columns of soil the cl br weight ratio decreased rapidly from a high 300 reflecting rainfall to a low 10 reflecting the ratio of chlorine to bromine bound to soil organic matter

groundwater seepage controls salinity in a hydrologically terminal basin of semi arid northwest australia abstract very small groundwater outflows have the potential to significantly impact the hydrochemistry and salt accumulation processes of notionally terminal basins in arid environments however this limited groundwater outflow can be very difficult to quantify using classical water budget calculations due to large uncertainties in estimates of evaporation and evapotranspiration rates from the surface of dry lake beds in this study we used a dimensionless time evaporation model to estimate the range of groundwater outflow required to maintain salinity levels observed at the fortescue marsh fm one of the largest wetlands of semi arid northwest australia 1100 km2 the groundwater outflow from aquifers underlying the fm to the lower fortescue catchment is constrained by an extremely low hydraulic gradient of 300 g l after 45 ka we calculated that only a very small seepage of 2g l yr 0 03 of the fm water volume is sufficient to maintain current salinity conditions the minimum time required to develop the current hydrochemical groundwater composition under the fm ranges from 60 to 165 ka we conclude that a dimensionless time evaporation model versus inflow over outflow ratio model is likely more suitable than classical water budget calculations for determining outflow from large saline lakes and to estimate groundwater seepage from hydrologically terminal basins

tectonic geomorphology and late quaternary deformation on the ragged mountain fault yakutat microplate south coastal alaska abstract the 33 km long ragged mountain fault rmf forms the northwestern corner of the yakutat terrane which is colliding with the north american plate in south coastal alaska at 5 5 cm yr the fault zone contains three types of scarps in a zone up to 175 m wide 1 antislope scarps on the lower range front 2 a sinuous thrust scarp at the toe of the range front and 3 a swarm of flexural slip scarps on the footwall trenches across the first two scarp types reveal evidence for two holocene surface ruptures plus several late pleistocene ruptures in the antislope scarp trench ruptures occurred at 0 5 3 9 ka slightly younger than 8 3 ka and at 18 1 21 8 ka recurrence intervals 4 4 8 kyr and 9 8 13 3 kyr displacements per event ranged from 15 to 40 cm in the thrust trench ruptures are dated at 2 8 5 9 ka 5 9 17 2 ka and 17 2 44 9 ka mean recurrence intervals 7 2 kyr and 19 5 kyr displacements per event ranged from 26 to 77 cm we interpret the thrust fault as the primary seismogenic structure and its largest trench displacement 77 cm equates to the average displacement expected for a 33 km long reverse rupture the flexural slip scarp in contrast was rapidly formed ca 4 ka but its sag pond sediments have continued to slowly fold up to present the southern third of the fault is dominated by large gravitational failures of the range front as large as 2 5 km wide 0 6 0 7 km long and 200 250 m thick which head in a linear 40 m deep range crest trough filled with lakes a classic expression of deep seated gravitational slope deformation

slip partitioning in the northeast pamir tian shan convergence zone abstract based on a detailed analysis of satellite imagery combined with field geologic and geomorphic observations we have mapped late cenozoic folds and faults in the northeastern pamir tian shan convergence zone it is a unique example to understand intracontinental ongoing mountain building within india eurasia collision system in the front of northeastern pamir our investigations reveal that the nw wnw trending folds display a right stepping en echelon pattern and nw wnw striking faults are mainly characterized by south dipping thrusts with an extensive dextral strike slip component drainage systems across the active faults show a systematic right lateral offset in contrast structural style of the ene trending fold and thrust belts are predominated by south north directed shortening southwest of the tian shan our results also infer that oblique thrusting accommodates as long term dextral slip rate of ca 4 0 mm yr during the late cenozoic time north of the pamir topographic front tectono stratigraphic evidence suggests that the tectonic deformation was initiated at ca 3 5 ma in the study area we suggest that intracontinental mountain building in the pamir tian shan convergence zone should be attributed to the crustal shortening caused by folding and thrusting as well as block rotation related to strike slip faulting within the india eurasia collision system

on the role of sea surface temperature gradients in forcing low level winds and convergence in the tropics abstract we examine the importance of pressure gradients due to surface temperature gradients to low level p 700 mb flow and convergence in the tropics over time scales 1 month the latter plays a crucial role in determining the distribution of cumulonimbus convection and rainfall our approach is to consider a simple one layer model of the trade cumulus boundary layer wherein surface temperature gradients are mixed vertically consistent with ecmwf analyzed data the top of the layer is taken at 700 mb the influence from higher levels is intentionally suppressed by setting horizontal pressure gradients and frictional stresses to zero at the top of the layer horizontal convergence within the layer is taken up by cumulonimbus mass flux however the development of the cumulonimbus mass flux is associated with a short relaxation time o hr roughly the development time for such convection during this short time horizontal convergence acts to redistribute mass so as to reduce horizontal pressur

active tectonics of central western caucasus georgia abstract this work contributes to a better knowledge of potentially seismogenic faults of the georgia greater and lesser caucasus by evaluating the distribution of earthquake foci active tectonic stress field kinematics and geometry of main fault planes we consider all the information coming from field structural geology geomorphology seismological data from historical and instrumental catalogues seismic reflection sections as well as new focal mechanism solutions these data enable recognizing some active ene wsw reverse faults in the core of the greater caucasus that are parallel to the mountain range at the southernmost front of the greater caucasus a series of main thrusts dipping towards nne are active with up to hundreds km long segments along this thrust zone a potentially locked segment is present about 90 km long the studied section of the lesser caucasus has active structures along the northern front given by south dipping thrusts as well as in the central core where strike slip and oblique faults coexist the transcaucasian depression between the two mountain ranges shows an ongoing inversion tectonics of the central part of the rioni basin where active n to ne dipping reverse faults are present accompanied by clear evidence of uplift of a wide area the data are coherent with a n s to nne ssw contraction of the central western greater caucasus and lesser caucasus although in general the seismicity decreases westward in terms of number of earthquakes and magnitude seismological and geological structural data in the rioni basin indicate here a quaternary propagation of deformation towards the west

late quaternary kinematics of the pallatanga strike slip fault central ecuador from topographic measurements of displaced morphological features the northeast trending pallatanga right lateral strike slip fault runs across the western cordillera connecting n50 e n70 e trending normal faults in the gulf of guayaquil with n s reverse faults in the interandean depression over most of its length the fault trace has been partly obscured by erosional processes and can be inferred in the topography only at the large scale only the northern fault segment which follows the upper rio pangor valley at elevations above 3600 m is prominent in the morphology valleys and ridges cut and offset by the fault provide an outstanding record of right lateral cumulative fault displacement the fault geometry and kinematics of this particular fault segment can be determined from detailed topographic levellings the fault strikes n30 e and dips 75 to the nw depending on their size and nature transverse morphological features such as tributaries of the rio pangor and intervening ridges reveal right lateral offsets which cluster around 27 11m 41 5 4 m 590 65 m and 960 70 m the slip vector deduced from the short term offsets shows a slight reverse component with a pitch of about 11 5 sw the 41 5 4 m displacements are assumed to be coeval with the last glacial termination yielding a mean holocene slip rate of 2 9 4 6 mm yr 1 assuming a uniform slip rate on the fault in the long term the 27 m offset appears to correlate with an identified middle holocene morphoclimatic event and the long term offsets of 590 m and 960 m coincide with the glacial terminations at the beginning of the last two interglacial periods

late oligocene early miocene initiation of shortening in the southwestern chinese tian shan implications for neogene shortening rate variations abstract the cenozoic tian shan is one of the preeminent examples of an intracontinental orogen however there remains a significant controversy over when deformation related to the india asia collision commenced and therefore how shortening within the mountains has been partitioned over time one approach has been to look at the modern shortening rate as measured by geodetic studies combined with estimates of the total shortening across the range and extrapolate backwards this approach suggests that the onset of range construction was ca 10 ma k y abdrakhmatov s a aldazhanov b h hager m w hamburger t a herring k b kalabaev k b kalabayev v i makarov p molnar s v panasyuk m t prilepin r e reilinger i s sadybakasov b j souter y a trapeznikov v y tsurkov a v zubovich relatively recent construction of the tien shan inferred from gps measurements of present day crustal deformation rates nature 384 6608 1996 450 453 an alternate method is to determine the age of the onset of exhumation using thermochronology we present 19 new apatite fission track aft results from the southwestern chinese portion of the belt this region represents the first area exhumed during the late tertiary along a transect at ca 76 e exhumation commenced at the oligocene miocene boundary 24 ma along the maidan and muziduke thrusts which bound the southern side of the kokshaal range subsequently deformation propagated ca 20 km south to the kashi basin bounding thrust kbt which was exhumed by no earlier than 18 9 3 3 ma three detrital aft samples from plio pleistocene strata deposited ca 20 km farther south contain fission track grain age peaks that young monotonically upwards from 20 9 7 0 5 3 ma to 15 9 5 4 4 0 ma with a fairly constant lag time of 16 to 18 ma these ages combined with structural data suggest that both the hanging wall and the footwall of the kbt experienced a renewed episode of exhumation during the latest cenozoic the discrepancy between the late oligocene miocene initiation of significant exhumation shown herein and the 10 ma initiation estimate from geodesy suggests that the tian shan has undergone a complex late cenozoic shortening history assuming that the present shortening rate could account for the total amount of cenozoic shortening in 10 ma and realizing that shortening initiated at least 15 myr earlier we conclude that the shortening rate must have varied over time possibly in pulsed southward migrating events and that the present rate may not reflect the average rate since initiation of range uplift

hydrogeochemical and isotopic constraints on the origins of dryland salinity murray basin victoria australia abstract combined hydrogeological and hydrogeochemical data allow flow systems and the origins of solutes in the honeysuckle creek area of the southeastern murray basin which is an area affected by dryland salinity to be constrained recharge occurs both on the uplands that are composed of fractured violet town volcanic rocks and the riverine plain that comprises sediments of the shepparton and coonambidgal formations groundwater from the violet town volcanics has low salinity 20 mmol l groundwater has intermediate cl br ratios 600 1000 which indicate that the high salinities do not simply result from halite dissolution rather mixing of groundwater homogenises cl br ratios and evaporation as a consequence of a shallow water table is the dominant process that increases salinity oxygen and h isotopes also indicate that mixing and evaporation have occurred these results indicate that land use over the whole region not just the uplands needs to be considered in any salinity management plans additionally future development of salinity is controlled by depth to the water table on the plains and the efficiency of recharge rather than by salt stores halite or brines in the unsaturated zone

long term investigation of a deep seated creeping landslide in crystalline rock part ii mitigation measures and numerical modelling of deep drainage at campo vallemaggia for more than 200 years the villages of campo vallemaggia and cimalmotto have been slowly moving on top of a deep seated landslide in the southern swiss alps numerous mitigation measures have bee

large ancient earthquakes in the western issyk kul basin kyrgyzstan northern tien shan abstract new paleoseismological and archaeoseismological data from the western issyk kul basin of kyrgyzstan northern tien shan provide new insights on active fault in the actively deforming basement involved thrust system of central asia newly discovered fault scarps follow south and north dipping thrust faults which delineate the kyrgyz and kungey ranges bordering the issyk kul basin motion on these faults generated earthquakes with magnitudes 6 2 7 6 and msk 64 shaking intensities viii xi deformation observed in the zone of the toguz bulak fault results from two holocene earthquakes and another event that occurred about 8000 yr bp two more events at 13 000 and 3000 yr bp deformed the northeastern periphery of the kyzyl ompul uplift archaeoseismological research in the northern sary bulun settlement in the western periphery of the boz barmak uplift revealed traces of another earthquake of msk 64 shaking intensity i viii dating back to the 12th century the obtained data correlates well with results of previous paleoseismological and archeoseismological studies they show that in the northern tien shan there were clusters of strong earthquakes with ages of 14 13 8 4 3 ka ago and in the 11 12th centuries ad divided by periods of 4 5 ka we infer that coseismic slip on these faults may have formed a tectonic dam at the edge of the basin through growth of the boz barmak uplift and this dam ultimately deflected the chu river into its modern channel which bypasses the lake lacustrine sediments in the northeastern periclinal segment of the boz barmak uplift bear signatures of soft sediment deformation structures seismites corresponding to seven m 5 5 5 i vi vii earthquakes timed at about 20 000 yr bp

a modeling study of the effect of the andes on the summertime circulation of tropical south america abstract a simple linear two level model of the atmosphere is developed which has a reasonable representation of the external and tropically important baroclinic modes by blocking the lower layer of the model with a meridional wall the interaction between diabatic forcing centered in the amazon basin and the andes is studied this forcing can be considered a source of rossby waves that scatter from the above partial barrier the scattering process is examined analytically by making the long wave approximation with the conclusion that transmission of external rossby waves reflection of baroclinic kelvin waves and the creation of topographic jets are likely to be important numerical solutions without the long wave approximation are then considered and the effects of the above scattering process are examined the upper level circulation is shown to be qualitatively similar to that obtained without a barrier the low level circulation west of the barrier is weak in the winds and consists of a positive g

present day kinematics of asia derived from geologic fault rates active fault geometry available quaternary rates on major faults and the far field plate motion are used to determine crustal kinematics in the collision zone between india and asia using a finite element formalism to construct a spherical shell model of the asian continent with embedded faults we seek a velocity solution approaching the motion of rigid blocks by minimizing the elastic strain energy in the fault bounded blocks by doing so we test the assumption that long term deformation within continents is mostly localized into major faults in the solution fault motion accounts for more than 80 of the deformation allowing us to describe our velocity model in terms of quasi rigid block rotations on the sphere south china is rotating clockwise about a pole located southwest of borneo implying an e ese velocity vector of 11 mm yr for a point at shanghai in agreement with the velocity vector determined by very long baseline interferometry heki et al 1995 the eastward movement of south china is accommodated by oblique extension along the red river fault at a rate of 10 5 mm yr in the south and by the combination of left lateral strike slip motion on the qinling dabie shan fault and the counterclockwise rotation of the ordos and adjacent blocks in the north the tarim rotates clockwise with respect to dzungaria about a pole located at 44 n 92 e consistent with increasing crustal shortening toward the west throughout the tien shan assuming incompressibility a crustal volume budget over a domain encompassing the tertiary mountain ranges in asia shows that over the last 10 000 years 73 4 of the north south shortening between india and asia has been absorbed by thickening of the lithosphere and 27 has been accommodated by lateral extrusion of continental blocks the present day predominance of thickening in asia results from the relatively slow eastward motion of south china controlled by strike slip faulting in the qinling shan and oblique extension in northeastern china

source parameters of moderate sized earthquakes in the tien shan central asia from regional moment tensor inversion we estimate faulting geometry depth and seismic moment of 32 moderate sized earthquakes in the tien shan by matching observed and synthetic seismograms recorded at regional distances the moment tensor compression axes are oriented in the direction 170 350 consistent with the orientation of india eurasia convergence this compression is manifested in reverse faulting on roughly east west trending fault planes faults within the mountain system have moderate to steep dips but range bounding faults appear to dip more gently earthquake source depths are in the range 5 25 km consistent with those determined from local earthquake studies the distribution and mechanism of earthquakes in the tien shan suggests that a significant proportion of the active deformation in the tien shan is absorbed by shortening across intramontane basins the absence of strike slip earthquake mechanisms associated with the talas ferghana fault suggests that the fault is presently locked with deformation accommodated on neighboring compressional structures

gps velocity field for the tien shan and surrounding regions 1 measurements at 400 campaign style gps points and another 14 continuously recording stations in central asia define variations in their velocities both along and across the kyrgyz and neighboring parts of tien shan they show that at the longitude of kyrgyzstan the tarim basin converges with eurasia at 20 2 mm yr nearly two thirds of the total convergence rate between india and eurasia at this longitude this high rate suggests that the tien shan has grown into a major mountain range only late in the evolution of the india eurasia collision most of the convergence between tarim and eurasia within the upper crust of the tien shan presumably occurs by slip on faults on the edges of and within the belt but 1 3 mm yr of convergence is absorbed farther north at the dzungarian alatau and at a lower rate with the kazakh platform to the west the tarim basin is thrust beneath the tien shan at 4 7 mm yr with respect to eurasia the ferghana valley rotates counterclockwise at 0 7 myr 1 about an axis at the southwest end of the valley thus gps data place a bound of 4 mm yr on the rate of crustal shortening across the chatkal and neighboring ranges on the northwest margin of the ferghana valley and they limit the present day slip rate on the right lateral talas ferghana fault to less than 2 mm yr gps measurements corroborate geologic evidence indicating that the northern margin of the pamir overthrusts the alay valley and require a rate of at least 10 and possibly 15 mm yr

vertically propagating annual and interannual variability in an ogcm simulation of the tropical pacific ocean in 1985 94 abstract the annual and interannual variability in the subthermocline equatorial pacific is studied in a simulation of the tropical pacific for the 1985 94 decade using a primitive equation high resolution model the study focuses on temperature variability and vertical energy fluxes similar to the observations made by w s kessler and j p mccreary the annual harmonic of vertical isotherm displacements presents phase lines sloping downward from east to west with off equatorial maxima estimates of zonal and vertical phase speeds the location of the maxima of isotherm displacements and an analysis of ernergy fluxes suggest the presence of l 1 rossby waves the simulated field is somewhat more trapped toward the equator than the observations a linear simulation is carried out for the vertical standing modes with characteristics derived from the ogcm simulation in the linear simulation high order meridional mode rossby waves are more prominent than in the ogcm simulation however the l 1 ros

ground water control of evaporite deposition topographically closed basins may be hydrologically open as a result of seepage losses to underlying or surrounding ground water systems in such cases these losses can have a substantial control over the suite and the thicknesses of evaporite minerals formed in the basin the ratio of ground water outflow to inflow flux ratio in hydrologically open basins is as important in determining the mineralogy and thicknesses of evaporite deposits as the solute composition of the inflow water attainment of steady state flux ratios permits large thicknesses of two or three minerals to form rather than thin veneers of many minerals the presence or absence of glauberite mirabilite halite bloedite polyhalite and hexahydrite caused by subtle changes in the ground water seepage is illustrated using an example from the southern high plains of texas and new mexico however the model is general and is applicable with any solute composition including that of seawater and the use of surface rather than ground water an analytical lumped parameter solute mass balance model is developed to define the concept of a ground water flux ratio as it applies to topographically closed basins in which evaporation exceeds precipitation diffusion advection and density driven flow are proposed as mechanisms by which solutes can escape to the ground water from these closed basins the geochemical reaction computer program phrqpitz is used to document the effects of various flux ratios on the mineralogy and thickness of deposits solute analyses used in conjunction with the model can be used to screen prospective basins as well as to provide insights for exploratory drilling program

magnetostratigraphy of the yaha section tarim basin china 11 ma acceleration in erosion and uplift of the tian shan mountains we report a magnetostratigraphic and rock magnetic study of the yaha section located on the southern flank of the central tian shan mountains asia our results show a two fold increase in sedimentation rate as well as marked changes in rock magnetic characteristics ca 11 ma after 11 ma sedimentation rate remained remarkably constant until at least 5 2 ma these findings are consistent with sedimentary records from other sections surrounding the tian shan we conclude that uplift and erosion of the tian shan accelerated ca 11 ma long after the onset of the collision between india and asia and that the range rapidly evolved toward a steady state geometry via a balance between tectonic and erosion processes

past changes to isotopic and solute balances in a continental playa clues from stable isotopes of lacustrine carbonates in many salt lakes around the world the relative abundance of preserved authigenic minerals is different from that predicted from solute mass balance calculations conventional mass balance models assume that chloride behaves conservatively over long periods of time and fail to take into account the role of diffusion deflation and fractional crystallisation dissolution of salts an alternative approach is to use oxygen isotopes as these reflect directly water molecule rather than solute concentrations and have the added advantage of providing a palaeohydrological record in lacustrine carbonates we present a steady state stable isotope model in conjunction with stable isotopic measurements of sub surface brines regional groundwaters and carbonate deposits from the lake malata lake greenly playa complex in south australia to estimate the apparent leakage and palaeoleakage from these superficially closed playa lakes the steady state model calculations using the present and compositions of the lake brines and inflowing groundwater suggest that the apparent present day leakage for the complex is 75 to 90 of inflow 35 times that calculated from cl and br under such conditions only low magnesian calcite precipitates and the lake water experiences reduced effects of evaporation gas and vapour exchange and consequently reduced isotopic and chemical enrichment further our model shows that calcite becomes increasingly mg rich until leakage is reduced to 55 to 70 of inflow a condition favourable for dolomitisation and of the lacustrine carbonates show excursions on the order of 5 over the length of a 2 3 m core indicating that the lake complex has varied from being throughflow dominated presence of low mg calcite relatively depleted in and to evaporation dominated high mg calcite dolomite relatively enriched in and throughout late quaternary our estimates of leakage fractions are consistent with the observed mineralogical suite but there remains a discrepancy between apparent closure indicated by the presence of the highly saline brine reservoir 1 leakage and high rates of throughflow inferred from stable isotope data we propose that the brine was formed by winter time re solution of a seasonal halite crust which forms during summer dominated evaporative discharge recirculation of the secondary brine and mixing with regional groundwater may decouple the solute cycle from the water cycle in many playa lakes the end result is a partially mixed brine characterised by nearly conserved solutes but with isotopic signatures indicative of brine rainfall groundwater interactions

tectonic and gravity induced deformation along the active talas fergana fault tien shan kyrgyzstan abstract this paper shows by field palaeoseismological data the holocene activity of the central segment of the intracontinental talas fergana fault tff and the relevance of possible future seismic shaking on slope stability around a large water reservoir the fault striking nw se is marked by a continuous series of scarps deflected streams and water divides and prehistoric earthquakes that offset substrate and holocene deposits fault movements are characterised by right lateral strike slip kinematics with a subordinate component of uplift of the ne block structural geological and geomorphological field data indicate that shallow and deep landslides are aligned along the tff and some of them are active where the tff runs close to the reservoir the fault trace is obscured by a series of landslides affecting rock and soil materials and ranging in size from small slope instabilities to deep seated gravity induced slope deformations dgsds the largest of these which does not show clear evidence of present day activity involves a volume of about 1 km3 and is associated with smaller but active landslides in its lower part with volumes in the order of 2 5 104 m3 to 1 106 m3 based on the spatial and temporal relations between landslides and faults we argue that at least some of these slope failures may have a coseismic character stability analyses by means of limit equilibrium methods lems and stress strain analysis by finite difference numerical modelling fdm were carried out to evaluate different hazard scenarios linked to these slope instabilities the results indicate concern for the different threats posed ranging from the possible disruption of the m 41 highway the main transportation route in central asia to the possible collapse of huge rock masses into the reservoir possibly generating a tsunami

numerical investigation of coupled density driven flow and hydrogeochemical processes below playas numerical modeling approaches with varying complexity were explored to investigate coupled groundwater flow and geochemical processes in saline basins long term model simulations of a playa system gain insights into the complex feedback mechanisms between density driven flow and the spatio temporal patterns of precipitating evaporites and evolving brines using a reactive multicomponent transport model approach the simulations reproduced for the first time in a numerical study the evaporite precipitation sequences frequently observed in saline basins bull s eyes playa specific flow evapo concentration and chemical divides were found to be the primary controls for the location of evaporites formed and the resulting brine chemistry comparative simulations with the computationally far less demanding surrogate single species transport models showed that these were still able to replicate the major flow patterns obtained by the more complex reactive transport simulations however the simulated degree of salinization was clearly lower than in reactive multicomponent transport simulations for example in the late stages of the simulations when the brine becomes halite saturated the non reactive simulation overestimated the solute mass by almost 20 the simulations highlight the importance of the consideration of reactive transport processes for understanding and quantifying geochemical patterns concentrations of individual dissolved solutes and evaporite evolution this article is protected by copyright all rights reserved

late quaternary kinematics slip rate and segmentation of a major cordillera parallel transcurrent fault the cayambe afiladores sibundoy system nw south america abstract we describe the recent activity of the cayambe afiladores sibundoy fault casf and recognise it as one of the major potential active structures of northwestern south america based on field observations stereoscopic aerial photos of offset late pleistocene holocene deposits and landforms and crustal seismic activity the casf runs for at least 270 km along the sub andean zone of northern ecuador and southern colombia we measured systematic latest pleistocene holocene right lateral strike slip motion and right lateral reverse motion consistent with earthquake focal mechanism solutions and estimated a 7 7 0 4 to 11 9 0 7 mm yr slip rate magnitudes of the earthquakes that could be generated by possible fault segment reactivation range up to m 7 0 0 1 the casf should be considered as a major source of possible future large magnitude earthquakes presenting a seismic hazard for the densely populated regions to the west the casf is part of the tectonic boundary of the north andean block escaping nne wards with respect to the stable south american plate

hydrogeologic processes in saline systems playas sabkhas and saline lakes abstract pans playas sabkhas salinas saline lakes and salt flats are hydrologically similar varying only in their boundary conditions thus in evaluating geochemical processes in these systems a generic water and solute mass balance approach can be utilized a conceptual model of a coastal sabkha near the arabian gulf is used as an example to illustrate the various water and solute fluxes analysis of this model suggests that upward flux of ground water from underlying formations could be a major source of solutes in the sabkha but contribute only a small volume of the water local rainfall is the main source of water in the modeled sabkha system with a surprisingly large recharge to rainfall ratio of more than 50 the contribution of seawater to the solute budget depends on the ratio of the width of the supratidal zone to the total width and is generally confined to a narrow zone near the shoreline of a typical coastal sabkha because of a short residence time of water steady state flow is expected within a short time 50 000 years the solute composition of the brine in a closed saline system depends largely on the original composition of the input water the high total ion content in the brine limits the efficiency of water rock interaction and absorption because most natural systems are hydrologically open the chemistry of the brines and the associated evaporite deposits may be significantly different than that predicted for hydrologically closed systems seasonal changes in temperature of the unsaturated zone cause precipitation of minerals in saline systems undergoing evaporation thus during the hot dry season months minerals exhibit retrograde solubility so that gypsum anhydrite and calcite precipitate evaporation near the surface is also a major process that causes mineral precipitation in the upper portion of the unsaturated zone e g halite and carnallite provided that the relative humidity of the atmosphere is less than the activity of water the slope of the fresh brine water interface in saline lake systems is shallower than in fresh seawater interface because of the greater density difference between the fresh brine water bodies the interface between sabkha brines and seawater slopes seaward unlike normal marine fresh water systems that slope landward moreover the brine seawater interface does not achieve steady state because it is pushed toward the sea by the sabkha s brine

magnetochronology of the upper cenozoic strata in the southwestern chinese tian shan rates of pleistocene folding and thrusting abstract the southwestern chinese tian shan of central asia is an actively deforming part of the indian asian collision system paleomagnetic investigations of two plio pleistocene terrestrial successions provide the first detailed magnetostratigraphy for the upper cenozoic strata in this region paleomagnetic samples were collected from 358 sites within the atushi formation and xiyu formation across the atushi talanghe anticline near atushi thermal demagnetization behavior reversal and fold tests of paleomagnetic stability indicate that the characteristic remanence directions were acquired before tilting and folding of the strata a composite magnetostratigraphic section for this sequence correlates with the mammoth subchron to the jaramillo subchron between 3 3 and 1 07 myr of the geomagnetic polarity timescale of cande and kent j geophys res 100 1995 6093 6095 the mean declination 349 3 in the boguzihe section indicates a counterclockwise vertical axis rotation 11 2 during the past 1 4 myr the conglomeratic xiyu formation is time transgressive along its progradational contact with the underlying atushi formation across a map distance of 6 km the basal contact ranges from less than 1 0 myr in the ganhangou section to 1 9 myr in the boguzihe section to the southwest and to 2 8 myr on the northwest limb of the anticline northeastward lateral propagation and growth of the atushi talanghe anticline initiated at 1 4 myr in the boguzihe and 1 2 myr in the ganhangou the cross section in the boguzihe provides a conservative maximum estimate of shortening rate of 3 3 4 4 mm yr and uplift rate of 3 mm yr this rate represents about half of the geodetically determined shortening rate between the northern tarim basin and the kyrgyz tian shan wang et al acta seismol sin 22 2000 263 270 reiger et al earth planet sci lett 191 2001 157 165 during fold growth over the past 1 4 myr the crest of the atushi talanghe anticline eroded at an average rate of 2 6 2 7 mm yr

on the genesis of the equatorial annual cycle abstract a linear theory is proposed that can explain both the period and the westward propagation of the equatorial annual cycles in the sst and zonal wind a coupled model linearized about a mean state of the air sea system is used this model allows the surface winds to directly change the sst through surface evaporation and vertical mixing in contrast to the formulation of the conventional air sea coupling models that emphasize the effects of winds on ocean dynamics it is demonstrated that the characteristics of the equatorial seasonal cycle including its period phase and amplitude are determined to a large extent by the mean state of the air sea coupling system the meridional wind which is specified here is the most important forcing for the annual cycle in sst suggesting that the equatorial annual cycle is the response to an annual solar forcing in the off equatorial regions

effects of topography on surface fault geometry and kinematics examples from the alps italy and tien shan kazakstan abstract the kinematics and extent of surface faulting are usually determined using observations on morphostructures such as escarpments and measurements of the net displacement of geologic deposits and topographic features such as gullies and ridges the present paper shows that these measurements can be misleading in rugged terrains if one does not take into account the effect of topography to illustrate this effect field data on surface deformations collected along holocene faults of the italian alps and kazakstan tien shan are compared with fault plane geometry and local topography the reverse foscagno fault italy which is also linked to deep seated gravitational slope deformation splays upward at a 50 m high ridge inducing scarps with apparent normal offset the transpressional sate fault tien shan changes its dip near the surface where it intersects ridges at least 50 60 m high here fault inclination changes up to 60 80 with a complete inversion of fault dip a normal fault appearing at the surface the transpressional beskaragai fault tien shan manifests an opposite sense of slip at a 80 m high ridge a detailed measurement of surface displacement along these holocene structures shows that the offset apparently increases at ridges and tends to zero at inter ridge depressions these data are here explained with a new model which considers the greater mobility of the rock mass of the ridge which has unbuttressed sides this produces upward or horizontal downhill expulsion of part of the ridge in a direction perpendicular to the fault strike if faulting has vertical motions while the expulsion direction is parallel to the fault strike when strike slip motions occur this expulsion can be accompanied by tilting which produces oversteepening of the downhill slope and landsliding

ocean atmosphere interaction and the tropical climatology part ii why the pacific cold tongue is in the east abstract the influence of coupled process on the climatology of the tropical pacific is studied in a model for the interaction of equatorial sst the associated component of the walker circulation and upper ocean dynamics in this part the authors show how different physical mechanisms affect the spatial pattern of the pacific warm pool and cold tongue in this coupled climatology when model parameters give a suitable balance between effects of upwelling and thermocline depth on sea surface temperature and for suitable atmospheric parameters a good prototype for the observed cold tongue configuration is produced this is largely determined by coupled ocean atmosphere processes within the basin presence of an easterly wind s component produced by factors external to the pacific basin can be important in setting up a cooling tendency but this is magnified and modified by a chain of nonlinear feedbacks between trade winds and ocean dynamics affecting the sst gradient within the basin these feedbacks d

geochemical and hydrological processes controlling groundwater salinity of a large inland wetland of northwest australia abstract understanding mechanisms of hydrochemical evolution of groundwater under saline and brine wetlands in arid and semiarid regions is necessary to assess how groundwater extraction or injection in large scale basins may affect the natural interface between saline fresh aquifers in those systems we investigated the evolution of groundwater of the fortescue marsh a large inland wetland of northwest australia that is mainly supplied by floodwater from the upper fortescue river catchment the marsh is located in the pilbara region one of the world s major iron ore provinces where mining activities often occur below water tables here we quantified the stable isotope and chemical composition of groundwater surface water and rainfall in and around the marsh to better understand how saline marshes and playa lakes function geochemically hydrologically and ecologically the deep groundwater 50 m depth of the fortescue marsh is highly saline 100 g l 1 whilst shallow groundwater 0 20 m depth and surface water are mainly fresh or brackish currently the marsh is mainly recharged by occasional floodwater consequently salt in the marsh is concentrated by evaporation of rainfall we expected that the hydrochemical composition of surface and groundwater would therefore reflect the chemical composition of rainwater we analysed 206 water samples for stable isotope composition 2 h 18 o and water chemistry including ph dissolved oxygen electrical conductivity ec and total dissolved solids tds as well as na ca mg k si fe hco 3 so 4 cl sr and br we then developed geochemical models and a salt inventory to estimate the geological time of salt accumulation and to decouple geochemical characteristics of salt from modern groundwater we found that groundwater associated with the marsh can be divided into two distinct groups that are characterised by their stable isotope compositions i fresh and brackish groundwater tds 1 18 o 8 0 0 9 and ii saline and brine groundwater tds 10 g l 1 18 o varies from 2 5 to 7 2 fresh groundwater was evaporated by

atmospheric bromine flux from the coastal abu dhabi sabkhat a ground water mass balance investigation 1 a solute mass balance study of ground water of the 3000 km2 coastal sabkhat salt flats of the emirate of abu dhabi united arab emirates documents an annual bromide loss of approximately 255 metric tons 0 0032 gmoles or 85 kg km2 this value is an order of magnitude greater than previously published direct measurements from the atmosphere over an evaporative environment of a salar in bolivia laboratory evidence consistent with published reports suggests that this loss is by vapor transport to the atmosphere if this bromine flux to the atmosphere is representative of the total earth area of active salt flats then it is a significant and generally under recognized input to the global atmospheric bromide flux