lake highstands in the northern kalahari botswana during mis 3b and lgm a bstract the interpretations of late quaternary climate variation in the kalahari are controversial only few speleothem humidity records do exist and reconstruction of aridity periods using aeolian sediments is challenged by considerable dating uncertainties on the other hand studies on the large structural lake basins of the kalahari have to cope with tectonics and the active catchment being far in the north in a different climate zone thus hydrological signals from such palaeolakes may not or only partly reflect kalahari palaeoclimate the sediments of a regional drainage basin west of the tsodilo hills northern kalahari archive hydrological signals not superimposed by remote river catchment and tectonics a ca 3 m thick sediment profile near the palaeoshore of the former lake exhibits two lake highstands dated to mis 3 b and lgm geomorphological studies fossil aquatic assemblages their comparison to modern analogues and geochemical analyses including sclerochronological stable isotope patterns from gastropod shells suggest relatively deep freshwater to oligohaline open basin lake periods the data indicates that the climate was more humid than today with two intra annual rainfall maxima during the lgm but likely under temperature regimes similar to modern times the lake highstands were probably in phase with an inter hemispheric atlantic climate seesaw which may imply that the main moisture source was rather the southern atlantic than the indian ocean

ground deformation caused by magma ascent in an open conduit this study examines magma ascent processes of three basic types prior to intermittent explosions such as vulcanian or strombolian types specifically their relations to volcano ground deformation such repetitive explosions eject magma from an open conduit at short time intervals consequently magma pressure is expected to decrease at the conduit and or reservoir and thereby deflate the volcano then magma within the conduit rises exerting normal and shear stresses on the conduit wall thereby inflating the volcano diffusive mass transfer of water molecules from the melt to bubbles might occur subject to a sudden depressurization by eruption when magma includes numerous small gas bubbles such gas bubble expansion lifts the magma in the conduit calculations of ground deformation on a semi infinite medium for such rising magma show that vertical and radial displacements and tilt motions recorded in the far fields are proportional to the 1 5 power of time for low viscosity magma gas bubbles might rise in the melt because of buoyancy force the gas bubbles expand rapidly with time because of decreased ambient pressure pushing the magma upward in the conduit consequently the volcano slowly inflates initially then the rate of deformation increases over time eventually engendering a rapid inflation immediately before eruption these temporal changes in ground deformations contrast against cases in which magma does not include gas bubbles in such cases amplitudes of ground deformation increase almost linearly or even decrease with time at far fields these differences which are recognized as basic characteristics of temporal changes of ground deformation enable us to know the driving forces of magma in an open conduit and to evaluate the gas bubble behavior quantitatively in magma before eruption

the 1995 1998 eruption of the soufriere hills volcano montserrat wi eruption of the soufriere hills volcano began on 18 july 1995 after three years of elevated seismic activity four months of increasingly vigorous phreatic activity culminated in mid november 1995 with the initiation of dome growth growth rates increased unevenly through early march 1996 with fluctuations on time scales from hours to months since march 1996 gravitational collapse of the unstable dome flank has affected an ever increasing area with pyroclastic flows surges and ashfalls major collapse of the eastern flank on 17 september 1996 resulted in a sub plinian explosive eruption later that day by february 1997 the dome had outgrown the confines of the crater and begun to spill into the surrounding valleys a large collapse on 25 june 1997 caused pyroclastic flows and surges on the northern flanks and resulted in the only deaths of the eruption in august september and october 1997 vulcanian explosions followed further collapses on the western and northern flanks the largest event of the eruption occurred on 26 december 1997 with failure of the southwestern flank of the volcano producing a debris avalanche and large dome collapse pyroclastic flows dome growth ceased in early march 1998 but residual volcanic activity has continued and consists of ash venting mild explosions and dome collapse pyroclastic flows

attenuation of coda waves in new england abstract seismic wave attenuation was measured in new england from the time domain decay of coda wave amplitudes on narrow bandpass filtered seismograms of local earthquakes the frequency band of interest was 0 75 to 10 hz q c f was found to increase with frequency across this band but there was also a difference between the q c f values for short t t 100 sec lapse times of coda wave propagation for the short lapse time data corresponding to wave paths primarily in the upper crust q c f increases from 400 at 3 hz to 1300 at 10 hz for the large lapse time data corresponding to wave paths in the lower crust and upper mantle q c f was found to vary from 660 at 1 hz to 1500 at 10 hz if we interpret this dataset in terms of a model incorporating both scattering and anelastic attenuation we find that the mean free path of seismic waves over this frequency band is 80 km for short lapse times and 400 km for long lapse times if we assume that scattering is entirely responsible for the observed attenuation we find that the minimum mean free path for short lapse times is about 75 km over all frequencies whereas for long lapse times the minimum mean free path decreases from 400 km at 0 75 hz to 90 km at 10 hz

temporal variations of qc 1 and b values associated to the december 2000 january 2001 volcanic activity at the popocatepetl volcano mexico abstract we correlated temporal variations of coda attenuation q c 1 at 6 hz and b values with the 11 december 2000 23 january 2001 major eruptive activity at the popocatepetl volcano mexico we interpreted a total of 225 volcanic earthquakes with magnitudes between 1 9 and 3 3 located between 2 and 8 km from the summit of the volcano and registered from january 1999 to june 2001 q c 1 was estimated using a single scattering model and values of b were obtained applying the method of maximum likelihood our results indicate that from january 1999 to march 2000 period 1 q c 1 varied within the same range without significant changes then values of q c 1 steadily decreased during april mid december 2000 period 2 from about mid december 2000 onset of the major volcanic activity up to february 2001 period 3 q c 1 sharply increased reaching its peak value from march to june 2001 period 4 q c 1 decreased and increased in response to the post eruptive phase of dome formation and destruction process that took place during periods 2 and 3 average b values behaved opposite to the q c 1 trend within period 2 when q c 1 decreased b slowly increased at the start of period 3 b reached its peak value and returned to low values by the end of this time interval we associate the temporal changes of the two analyzed parameters to variations of pressure and or the variation in the degree of saturation of pore fluids that took place before during and after the major eruption during periods 2 and 3 q c 1 correlated negatively with b with a correlation coefficient of 0 61 and 0 83 respectively the significance of correlation cannot be rejected at the confidence level of 0 975 our observations may have important implications for future prediction studies of large eruptions at the popocatepetl volcano

paleoenvironmental and archaeological investigations at qinghai lake western china geomorphic and chronometric evidence of lake level history abstract qinghai lake located on the northeastern qinghai tibet plateau qing zang gaoyuan is china s largest extant closed basin lake its position relative to major asian climate systems makes it sensitive to global climate change the lake has been the subject of numerous paleoenvironmental investigations including dating of shoreline features around the lake basin here we report new age estimates of shoreline features geomorphic exposures and archaeological sites that contribute to the development of a lake level history for qinghai lake and a landscape model of the qinghai lake basin lake highstands above 3230 m 36 m above the modern lake level appear to date to late mis 5 70 110 ka the lake has had much more modest highstands since then no evidence of mis 3 lake stands higher than modern were found and early holocene highstands are no more than 12 m above modern if the age of highstands greater than 3230 m is confirmed through future work then the qinghai lake basin hydrologic balance prior to 70 ka was dramatically different than after that time including during the holocene a simple hydrologic balance model provides insights into the combination of precipitation evaporation and runoff generation needed to sustain the lake at 3260 m the highest shoreline observed a range of factors may explain the difference primarily the relative strength of the east asian monsoon the basin was apparently subject to extensive alluviation during mis 3 interrupted by widespread erosion and development of cryogenic features before and during the last glacial maximum lgm loess that presently drapes much of the lower basin landscape began to be deposited after the lgm 16 18 ka the landscape model outlined here has implications for archaeological visibility of early human occupation of the qinghai tibet plateau

early to mid holocene lake high stand sediments at lake donggi cona northeastern tibetan plateau china lake high stand sediments are found in three onshore terraces at lake donggi cona northeastern tibetan plateau and reveal characteristics of hydrological changes on lake shorelines triggered by climate change geomorphological processes and neo tectonic movements the terraces consist of fluvial alluvial to littoral lacustrine facies end member modeling of grain size distributions allowed quantification of sediment transport processes and relative lake levels during times of deposition radiocarbon dating revealed higher than modern lake levels during the early and mid holocene lake levels follow the trend of asian monsoon dynamics and are modified by local non climatic drivers site specific impacts explain fluctuations during the initial lake level rise 11 cal ka bp maximum lake extension reached 9 2 cal ka bp at 16 5 m above present lake level a p l l littoral and lacustrine sediment deposition paused during a phase of fluvial activity and post depositional cryoturbations at 8 5 cal ka bp when the lake level fell to 8 m a p l l after a second maximum at 7 5 cal ka bp lake level declined slightly at 6 8 cal ka bp probably due to a non climatic pulse that caused lake opening the level remained high until a transition towards drier conditions 4 7 cal ka bp though discontinuous high stand sediments provide a unique high resolution archive

interpreting stable isotope records from freshwater snail shell carbonate a holocene case study from lake golhisar turkey the oxygen and carbon stable isotope ratios from fossil snail shells within a small intramontane lake in southwest turkey are used to highlight the potential and problems of using freshwater snail carbonate as a palaeoenvironmental proxy two species gyraulus piscinarum and valvata cristata yielded different isotope ratios at the same sampling intervals probably due to differences in water isotope composition between different microhabitats isotope ratios from a number of individual shells from the same sampling intervals representing 7 25 years show large ranges up to 8 for 18o for each species only by analysis of a significant number of species specific shells 5 from each sampling interval can a true understanding of environmental change be obtained averages of the data provide an insight into longer term climatic variation while the ranges provide an estimate of short term decadal environmental variability

ground deformation measurements at the soufriere hills volcano montserrat ii rapid static gps measurements june 1996 june 1997 we describe measurements of ground deformation around the erupting soufriere hills volcano made between june 1996 and june 1997 using rapid static gps the measurements define a lateral displacement field which is approximately radially symmetrical about the growing dome no significant sustained vertical displacements have been identified radial displacements have generally increased steadily during this period of observation the rate of displacement decreases from 43 cm per year at a distance of 0 6 km from the centre of the dome to about 1 cm year at a distance of 3 8 km strains within one km of the dome itself are greater than 10 3 the rate of variation of strain with distance indicates a causative centre of pressure at a depth of not greater than 750 meters below the summit of the dome

regional variation and frequency dependence of qβ in the crust of the united states approximate lg attenuation coefficient values are determined for paths in eastern north america at periods between 2 and 4 sec where no data were previously available these new data together with reported values at a period of 1 sec are consistent with values predicted by a frequency dependentent q of the crust in which q varies as 0 2 the new data are inconsistent with values which would be predicted by models having prominent maxima or minima in q 1 within the period range 1 to 5 sec lg attenuation coefficients were computed for the frequency independent crustal q models of cheng and mitchell 1981 for the basin and range province and colorado plateau of the western united states the predicted values at 1 sec for the colorado plateau and basin and range province are about twice as large and three times as large respectively as those predicted for the eastern united states recently reported values of q for 1 sec lg in those regions are consistent with the attenuation coefficients and q values of lg predicted by the colorado plateau and basin and range province models a model with a small degree of frequency dependence of q would be consistent but is not required by the data

a 13 000 year climate record from western tibet although the tibetan plateau is important in influencing the atmospheric circulation of the northern hemisphere1 3 there are only a few continuous palaeoclimate records available and these are limited to the plateau s northeastern margin4 6 here we present a 13 000 yr record from sumxi co western tibet constructed from both lake core and shoreline studies which shows that conditions in the early middle holocene were warmer and wetter than at present these results confirm model predictions of an intensified monsoon over the region at 9 000 yr bp owing to an orbitally induced increase in summer insolation7 8 we also find evidence for warm humid pulses at 12 500 and 10 000 yr bp in phase with the steps of the last deglaciation and for a return to cold dry conditions at 11 10 000 yr bp none of which can be explained by orbital variations the existence of the cold episode confirms that the cooling associated with the younger dry as event occurred in continental china6 9 and provides further evidence of the global nature of this event10

ground deformation at soufriere hills volcano montserrat during 1998 2000 measured by radar interferometry and gps abstract we examine the motion of the ground surface on the soufriere hills volcano montserrat between 1998 and 2000 using radar interferometry insar to minimise the effects of variable atmospheric water vapour on the insar measurements we use independently derived measurements of the radar path delay from six continuous gps receivers the surfaces providing a measurable interferometric signal are those on pyroclastic flow deposits mainly emplaced in 1997 three types of surface motion can be discriminated firstly the surfaces of thick valley filling deposits subsided at rates of 150 120 mm year in the year after emplacement to 50 30 mm year two years later this must be due to contraction and settling effects during cooling the second type is the near field motion localised within about one kilometre of the dome both subsidence and uplift events are seen and though the former could be due to surface gravitational effects the latter may reflect shallow

diet and environment of a mid pliocene fauna from southwestern himalaya paleo elevation implications a mid pliocene fauna 4 2 3 1 ma was recently uncovered in the zanda zhada basin in the southwestern himalaya at an elevation of about 4200 m above sea level these fossil materials provide a unique window for examining the linkage among tectonic climatic and biotic changes here we report the results from isotopic analyses of this fauna and of modern herbivores and waters as well as paleo temperature estimates from the zanda basin the 13c values of enamel samples from modern wild tibetan asses and domesticated horses cows and goats in the area are 9 4 1 8 which indicate a diet comprising predominantly of c3 plants and are consistent with the current dominance of c3 vegetation in the region the enamel 13c values of the fossil horses rhinos deer and bovids are 9 6 0 8 indicating that these ancient mammals like modern herbivores in the area also fed primarily on c3 vegetation and lived in an environment dominated by c3 plants the lack of significant c4 plants in the basin suggests that the area had reached high elevations 2 5 km by at least the mid pliocene taking into account the changes in the 13c of atmospheric co2 in the past the enamel 13c values suggest that the average modern equivalent 13c value of c3 vegetation in the zanda basin in the mid pliocene was 1 2 lower than that of the c3 biomass in the basin today this would imply a reduction in annual precipitation by about 200 400 mm in the area since then assuming that the modern c3 13c precipitation relationship applied to the past consistent with this inference from the 13c data the enamel 18o data show a significant shift to higher values after the mid pliocene which also suggests a shift in climate to much drier conditions after 4 3 ma paleo temperature estimates derived from a fossil bone based oxygen isotope temperature proxy as well as the carbonate clumped isotope thermometer for the mid pliocene zanda basin are higher than the present day mean annual temperature in the area after accounting for late cenozoic global cooling these paleo temperature estimates suggest that the paleo elevation of the zanda basin in the mid pliocene was similar to or slightly less than 1 km lower than its present day elevation which is consistent with the inference from the 13c data

δ18o in mollusk shells from pliocene lake hadar and modern ethiopian lakes implications for history of the ethiopian monsoon abstract two of the five lacustrine intervals in the largely fluvial hadar formation afar ethiopia occur in the sidi hakoma member deposited 3 4 3 2 ma in a perspective of the 18o of 11 modern ethiopian lakes and their shells the 18o of the hadar fossil shells provide a snapshot of the nature of ancient lake hadar and ethiopia s climate in the pliocene ethiopia s modern lakes both in the rift and on the western plateau are fed by drainage of plateau rain with its well established barely negative 18osmow of 1 3 except for the man made lake koka reservoir all other ethiopian lakes are isotopically quite positive ranging from 5 4 to 16 0 indicating how significant evaporation is in their water budget shells from lakes with extant mollusk populations are mostly in isotopic equilibrium with the 18o and temperature of their lake water the upper transgressive interval in the sidi hakoma member is the largest one in the formation beginning at its base with the gastropod beds beach deposits mollusks from shell beds other than the gastropod beds show more positive and more variable 18o between shells with internal variations within shells as much as 7 at these times the site must have been underlain by a shallow partially isolated embayment of lake hadar which underwent rapid expansions and then contractions by evaporation within the few year lifetimes of the individual mollusks the results from the gastropod beds are of most significance for interpreting the overall paleoclimate at hadar their uniformly negative 18opdb shell values that average 6 7 represent a much less evaporated stage of lake hadar when its 18osmow was 8 lower than the spectrum of modern lakes in ethiopia and indeed even 3 or more lower than average modern plateau rain to explain such negative values we hypothesize that the atlantic derived air mass component to the ethiopian monsoon was persistently strengthened during pliocene summers which intensified the amount and the negative isotopic character of rainfall onto both the afar and the ethiopian plateaus that drained to lake hadar a similar phenomenon characterized the brief periodic pluvial episodes of the quaternary including the latest in the early holocene known as the african humid period in contrast to the hot semi desert steppe conditions of today s western afar the diverse abundant terrestrial fossil fauna at hadar including the early hominid australopithecus afarensis is explained by the wetter and probably cooler summers that persisted throughout the late pliocene

seismicity associated with dome growth and collapse at the soufriere hills volcano montserrat varied seismicity has accompanied growth and collapse of the lava dome of the soufriere hills volcano montserrat earthquakes have been classified as either volcano tectonic long period or hybrid and daily variations in the numbers of events have mapped changes in the style of eruption repetitive hybrid earthquakes were common during the first months of dome growth in july 1996 the style of seismicity changed and regular short lived hybrid earthquake swarms became common this change was probably caused by an increase in the magma flux earthquake swarms have preceded almost all major dome collapses and have accompanied cyclical deformation thought to be due to a build up of pressure in the upper conduit which is later released by magma moving into the dome

holocene environmental changes in bangong co basin western tibet part 4 discussion and conclusions abstract a 12 4 m core taken in lake bangong provides a continuous holocene climatic record we summarize information on changes in stable isotope and radiocarbon balances in the lake hydrobiology and vegetal cover in the catchment deduced from detailed analytical results given in the three preceding papers the bangong record is then compared with the environmental history of the neighbouring lake sumxi also constructed from multidisciplinary analyses the two records show a major environmental change at 10 9 5 ka b p attributed to a rapid strengthening of the summer monsoonal circulation which led to wet warm conditions this event was followed by a long term trend toward aridity which culminated around 4 3 ka b p in western tibet maximum monsoon rainfall seems to have occurred from 9 5 to 8 7 ka b p and from 7 2 to 6 3 ka b p as two wet pulses separated by a reversal event centered on 8 0 7 7 ka b p our results broadly agree with the records from lake seling in central tibet and lake qinghai at the plateau s northeastern margin and with palaeoclimatic studies in western china which document conditions wetter and warmer than those of today during the early middle holocene the environmental fluctuations recorded in western tibet appear in phase with climatic changes recognized in tropical north africa suggesting that the 8 0 7 7 ka b p and the 4 0 3 0 ka b p dry events were caused by abrupt disequilibrium in the climatic system

later pleistocene holocene climate conditions of qinghai xizhang plateau tibet based on carbon and oxygen stable isotopes of zabuye lake sediments abstract we present a time series of carbon and oxygen stable isotope records of the last 30 000 14c years throughout the last glacial postglacial cycle from western qinghai xizhang tibet plateau a 20 m core drilled in the south basin of zabuye salt lake was analyzed for inorganic and organic carbon and total sulfur contents 13c and 18o values of carbonates our results indicate that climatic changes have led to a drastic negative shift of stable isotope ratios at the transition between the last full glacial and the postglacial phase during later pleistocene times 16 2 kyr bp and a rapid positive shift at the transition from pleistocene to holocene 10 6 kyr bp the first shift is marked by the drop of 18ocarb values of about 10 from 2 to 8 and 13ccarb values of about 3 from 5 to 2 the second shift which occurred at the transition from pleistocene to holocene was of similar magnitude but in the opposite direction isotope data combined with total organic and inorganic carbon contents and the lithological composition of the core suggest this lake was an alluvial pre lake environment prior to ca 28 14c kyr bp during ca 28 16 2 14c kyr bp zabuye lake was likely a moderately deep lake with limited outflow the cool and arid glacial climate led the lake level to drop drastically extended residence time overwhelmed the lower temperature and caused a steady increase of 13ccarb and 18ocarb values and total inorganic carbon content in the sediments during ca 16 2 10 6 14c kyr bp this lake probably overflowed and received abundant recharge from melting glaciers when the deglaciation was in its full speed a spike of markedly enhanced 13ccarb and 18ocarb is seen at 11 5 kyr bp probably due to the isotopic effects left behind by the short but severe younger dryas yd event after ca 10 6 14c kyr bp zabuye lake probably closed its surface outflow due to strong desiccation and drastic climate warming the early and middle holocene were characterized by unstable climatic conditions with alternating warmer cooler episodes as indicated by the severe fluctuations of total organic carbon 13c and 18o values a hypersaline salt lake environment was finally formed at zabuye after 5 14c kyr bp when the mirabilite and halite concentrations steadily increased and became the dominant minerals in the sediments severe imbalance of inflow outflow resulted in the drastic increase of total sulfur 13ccarb and 18ocarb values and dominance of halite in the lake since ca 3 8 kyr bp to present

clumped isotope thermometry of modern and fossil snail shells from the himalayan tibetan plateau implications for paleoclimate and paleoelevation reconstructions

ostracods and stable isotopes of a late glacial and holocene lake record from the ne tibetan plateau abstract ostracod assemblage changes and stable isotopes of ostracod shells were used to reconstruct the salinity history of lake donggi cona on the northeastern tibetan plateau in response to the late glacial and holocene climate history brackish and relatively unstable conditions were inferred for the earlier part of the late glacial between 18 9 and 13 4 cal ka bp and for the early to mid holocene 11 9 6 8 cal ka bp a saline lake existed in the intervening period probably representing colder and drier conditions during the greenland stadial 1 younger dryas in north atlantic region freshwater conditions similar to the present stage of lake donggi cona were established for the first time at 6 8 cal ka bp this inference and the implied increase in moisture availability in the latter half of the holocene is in contrast to most climate records from the tibetan plateau which suggest drier and colder conditions however three lake records from the eastern tibetan plateau including our new record show that the holocene insolation driven monsoonal weakening and temperature decrease caused a catchment specific opposite response of the moisture availability in comparison to those at the majority of sites catchments with relatively low precipitation at present experienced apparently a moisture availability increase during the colder second half of the holocene in contrast to the inferred drier conditions at predominantly generally wetter sites the increase in moisture availability at relatively dry sites mainly results from the lowered temperature and evaporation but is probably further controlled by a complex of factors including the amount and timing of precipitation the altitudes of the lake basins and upper reaches and the existence or development of glaciers snow fields and frozen ground in a given catchment our record from lake donggi cona suggests that the recently observed reduction in yellow river discharge in response to present global warming will likely continue or even increase under warmer climatic conditions in the future

permafrost on the tibet plateau china abstract the tibet plateau represents a unique permafrost environment being a result of high elevation caused by land uplift in the order of 3000 m over the last 2 million years under present climatic conditions the lower altitudinal limit of permafrost in the north is at 4200 m a s l which means that if the plateau were 1000 m lower than present there would be hardly any permafrost the permafrost is ice poor because during the quaternary the area was unglaciated and little water was available for the formation of massive ground ice furthermore today s climate is arid and little moisture is available for segregated and pore ice formation as a result mid portion desiccation of the active layer does not occur to the same extent as in high latitudes permafrost temperature on the plateau depends mainly upon altitude and varies irregularly with latitude permafrost is warm and thin compared with high latitude polar permafrost in both north america and russia and thus more sensitive to changes in climate and surface conditions a recent warming trend in ground temperature has been monitored and if maintained permafrost will become relict within the next ca 150 years permafrost features are few due to the arid environment many of the pingos on the plateau are genetically associated with faults and therefore of the open system type faults are the most powerful factor disturbing the thermal regime of the plateau permafrost

lake level reconstruction for 12 8 2 3 ka of the ngangla ring tso closed basin lake system southwest tibetan plateau article i nfo we present a shoreline based millennial scale record of lake level changes spanning 12 8 2 3 ka for a large closed basin lake system on the southwestern tibetan plateau fifty three radiocarbon and eight u th series ages of tufa and beach cement provide age control on paleoshorelines ringing the basin supplemented by nineteen ages from shell and aquatic plant material from natural exposures generally recording lake regressions our results show that paleo ngangla ring tso exceeded modern lake level 4727 m asl continuously between 12 8 and 2 3 ka the lake was at its highstand 135 m 4862 m asl above the modern lake from 10 3 ka to 8 6 ka this is similar to other closed basin lakes in western tibet and coincides with peak northern hemisphere summer insolation and peak indian summer monsoon intensity the lake experienced a series of millennial scale oscillations centered on 11 5 10 8 8 3 5 9 and 3 6 ka consistent with weak monsoon events in proxy records of the indian summer mon soon it is unclear whether these events were forced by north atlantic or indian ocean conditions but based on the abrupt lake level regressions recorded for ngangla ring tso they resulted in significant periodic reductions in rainfall over the western tibetan plateau throughout the holocene

potential of pollen and non pollen palynomorph records from tso moriri trans himalaya nw india for reconstructing holocene limnology and human environmental interactions the high altitude lake tso moriri 32 55 46 n 78 19 24 e 4522 m a s l is situated at the margin of the indian summer monsoon and westerly influences in the trans himalayan region of ladakh human settlements are rare and domestic and wild animals are concentrated in the alpine meadows a set of modern surface samples and fossil pollen from a deep water core was evaluated with focus on indicator types revealing human impact grazing activities and lake system development during the last ca 12 cal ka bp the non pollen palynomorph npp record comprising remains of limnic algae and invertebrates as well as fungal spores and charred plant tissue fragments were examined in order to attest palaeolimnic phases and human impact respectively changes in the early and middle holocene limnic environment are mainly influenced by regional climatic conditions and glacier fed meltwater flow in the catchment area the npp record indicates low lake productivity with high influx of freshwater between ca 11 5 and 4 5 cal ka bp which is in agreement with the regional monsoon dynamics and published climate reconstructions geomorphologic observations suggest that during this period of enhanced precipitation the lake had a regular outflow and contributed large amounts of water to the sutlej river the lower reaches of which were integral part of the indus civilisation area the inferred minimum freshwater input and maximum lake productivity between ca 4 5 1 8 cal ka bp coincides with the reconstruction of greatest aridity and glaciation in the korzong valley resulting in significantly reduced or even ceased outflow we suggest that lowered lake levels and river discharge at a larger regional scale may have caused irrigation problems and harvest losses in the indus valley and lowlands occupied by sedentary agricultural communities this scenario in turn supports the hypothesis that mature harappan urbanism ca 4 5 3 9 cal ka bp emerged in order to facilitate storage protection administration and redistribution of crop yields and secondly the eventual decline of the harappan culture ca 3 5 3 cal ka bp was promoted by prolonged aridity there is no clear evidence for human impact around tso moriri prior to ca 3 7 cal ka bp with a more distinct record since ca 2 7 cal ka bp this suggests that the sedimentary record from tso moriri primarily archives the regional climate history

strong influence of water vapor source dynamics on stable isotopes in precipitation observed in southern meghalaya ne india to calibrate 18o time series from speleothems in the eastern indian summer monsoon ism region of india and to understand the moisture regime over the northern bay of bengal bob we analyze the 18o and d of rainwater collected in 2007 and 2008 near cherrapunji india d values range from 18 5 to 144 4 while 18o varies between 0 8 and 18 8 the local meteoric water line lmwl is found to be indistinguishable from the global meteoric water line gmwl late ism september october rainfall exhibits lowest 18o and d values with little relationship to the local precipitation amount there is a trend to lighter isotope values over the course of the ism but it does not correlate with the patterns of temperature and rainfall amount 18o and d time series have to be interpreted with caution in terms of the amount effect in this subtropical region we find that the temporal trend in 18o reflects increasing transport distance during the ism isotopic changes in the northern bob surface waters during late ism and vapor re equilibration with rain droplets using an isotope box model for surface ocean waters we quantify the potential influence of river runoff on the isotopic composition of the seasonal freshwater plume in the northern bob temporal variations in this source can contribute up to 25 of the observed changes in stable isotopes of precipitation in ne india to delineate other moisture sources we use backward trajectory computations and find a strong correlation between source region and isotopic composition palaeoclimatic stable isotope time series from northeast indian speleothems likely reflect changes in moisture source and transport pathway as well as the isotopic composition of the bob surface water all of which in turn reflect ism strength stalagmite records from the region can therefore be interpreted as integrated measures of the ism strength

q c of three component seismograms of volcanic microearthquakes at campi flegrei volcanic area southern italy digital recordings of three component microearthquake codas from shallow seismic events in the volcanic region of campi flegrei southern italy were used with an automatic technique to calculate the attenuation factorq c codaq in the hypothesis of singles tos backscattering results show the same value ofq for each of the three components this result is interpreted as due to isotropics wave radiation pattern a check of the coda method was performed using a single station method based on simple assumptions on the direct sh wave spectrum single stationq was averaged over the stations and over the earthquakes results show that the two methods lead to comparable results a frequency dependence quite different from that evaluated in active tectonic regions was found for coda attenuation comparable to other volcanic areas throughout the world this is interpreted as due to the presence of magma that affects anelasticity and scattering

oxygen and carbon isotope patterns archived in shells of the aquatic gastropod radix hydrologic and climatic signals across the tibetan plateau in sub monthly resolution abstract the tibetan plateau tp including its surrounding mountain ranges represents the largest store of ice outside the polar regions it hosts numerous lakes as well as the head waters of major asian rivers on which billions of people depend and it is particularly sensitive to climate change the moisture transport to the tp is controlled by the indian and pacific monsoon and the westerlies understanding the evolution of the interaction of these circulation systems requires studies on climate archives in different spatial and temporal contexts the objective of this study is to learn more about the interannual variability of precipitation patterns across the tp and how different hydrologic systems react to different climatic factors aragonite shells of the aquatic gastropod radix which is widely distributed in the region may represent suitable archives for inferring hydrologic and climatic signals in particularly high resolution therefore sclerochronological studies of 18 o and 13 c ratios in radix shells from seven lakes were conducted each representing a different hydrologic and climatic setting on a transect from the pamirs across the tp the shell patterns exhibit an increasing influence of precipitation and a decreasing influence of evaporation on the isotope compositions from west to east 18 o values of shells from lakes on the eastern and central tp donggi cona yamdrok yumco tarab co mirror monsoon signals indicated by more negative values and higher variabilities compared to the more western lakes karakul bangong nyak manasarovar in yadang co located on the central southern tp the monsoon rains did not reach the lake in the sampling year although it is located in a region which is usually affected by monsoon circulation the 18 o values are used to differentiate the annual hydrological cycle into ice cover period melt water period precipitation period and evaporation period 13 c compositions in the shells particularly depend on specific habitats which vary in biological productivity and in carbon sources 18 o and 13 c patterns show a positive covariance in shells originating from large closed basins the results show that radix shells mirror general climatic differences between the seven lake regions these differences reflect both regional and local climate signals in sub seasonal resolution without noticeable dependence on the particular lake system

spatial variations of seismic attenuation in the north west of iranian plateau from analysis of coda waves abstract in this study spatial variation of coda wave attenuation in the north western nw iranian plateau is explored using local earthquakes single backscattering method is used to map the spatial variations of coda q qc using 14 969 earthquakes which are recorded digitally by sixteen permanent stations observed spatial attenuation maps are well correlated with geological setting of study area north west of iranian plateau is dominated with high attenuation which is well correlated with quaternary deposits as well as the sahnad sabalan volcanic zone and tabriz fault these observation is in accordance with numerous 2d velocity tomograms which have shown very low velocity in the nw iran the region characterized by volcanic structures exhibits mainly higher seismic attenuation than the surrounding regions whereas paleo tethys basin in the eastern part of covered area are categorized by smaller attenuation than the other zone our observation shows good correlation with reported lower crustal low velocity region beneath the sahand and sabalan volcanos the sahand and sabalan volcanoes are very large structures and they dominate the pliocene quaternary magmatic landscape of nw iran in addition our observation has clearly shown existence of a probable fault zone trending in ne sw direction between tabriz city and urmia lake which is consistent with the trend of meizoseismal zone of the deh khareqan modern azarshahr earthquake m 6 8 in 1641

cosmogenic 10be inferred lake level changes in sumxi co basin western tibet abstract most tibetan lakes are surrounded by conspicuous regressive shorelines attesting to high water levels in the past concentrations of the in situ produced cosmogenic radionuclide 10 be in bedrock from the three highest terraces surrounding sumxi co situated in western kunlun indicate that the highest lake level appeared before 10 000 11 500 yr and most likely between 11 000 and 12 800 yr younger ages for the two lower terraces imply regression of sumxi co during the early mid holocene the concurrency of the highest lake level with orbitally induced maximum northern hemisphere summer insolation suggests that the increase in water supply to sumxi co was most likely associated with increased recharge from melting glaciers we conclude that the enhanced indian monsoon during the early holocene did not penetrate the tibetan plateau and affect the northwestern part of tibet significantly

ground deformation due to magma ascent with and without degassing 1 i numerically calculate upward migration of vesiculated magma in an elastic volcanic conduit taking into account the bubble growth in melt elastic stress from the surrounding medium and degassing from the magma the results show that when magma containing gas bubbles reaches the ground surface without degassing the ground deformation accelerates just before the eruption in response to volumetric expansion of the magma on the other hand the rate of change in ground deformation is almost constant when the magma degasses as it ascends similar characteristics have been observed in ground deformation recorded before explosive eruptions and lava extrusion at several active volcanoes these consistencies strongly suggest that geodetic measurements which have been mainly used to date to estimate the eruption time and the locations of magmatic intrusions provide a basis for predicting the volcanic explosivity and monitoring bubble growth and degassing processes in the conduit

sub seasonal oxygen and carbon isotope variations in shells of modern radix sp gastropoda from the tibetan plateau potential of a new archive for palaeoclimatic studies carbon and oxygen isotope ratios have been measured for nine aragonite shells of the gastropod genus radix from the lake bangda co 30 29 n 97 04 e 4450 m a s l at the south eastern edge and from two characteristic sites at the lake kyaring co 31 09 n 88 17 e 4650 m a s l on the central tibetan plateau radix shells were sampled for isotope ratio analysis with high spatial resolution along the ontogenetic spiral of growth providing the basis of isotope records with a sub seasonal time resolution 18o values of shells from bangda co are on average 15 0 relative to pdb and the pattern exhibits a clear onset and progression of the summer monsoon precipitation indicated by a strong amount effect this pattern mirrors the precipitation pattern in the respective year and region as expected for a small surface area ca 0 3 km2 and shallow 5 m lake or habitat with short water residence times and little evaporative 18o enrichment of the lake water in contrast 18o values of radix shells from kyaring co habitat a which is connected to the deep several tens of metres and big surface area ca 660 km2 lake average at 13 0 consistent with a higher evaporation rate and longer water residence time the latter is supported by more 18o enriched water in this habitat the 18o values of radix shells from kyaring co habitat b are nearly as low as shells from bangda co due to the similar habitat characteristic but isotopic patterns of these shells exhibit a weaker amount effect in both lake systems 13c values of the shells are coupled with oxygen isotopes because a large amount of isotopically light carbon is washed from mountain slopes into the lake during the rainy season although other processes influence the isotopic patterns e g biological productivity 13c or temperature 18o these influences are minor compared with the monsoon signal or the effect of evaporation in the radix shell records the overall weaker amount effect in radix shells from kyaring co habitat b compared with shells from bangda co are consistent with a current decreasing monsoon influence from the south eastern edge towards the central tibetan plateau thus fossil shells of the gastropod genus radix are a valuable archive for reconstructing climatic and environmental changes on the tibetan plateau and provide information about former habitat sizes and depths

ground deformation studies at soufriere hills volcano montserrat i electronic distance meter studies frequent occupation of a network of instrument and target sites using an electronic distance meter edm over 21 months has led to the recognition of two distinct patterns of ground deformation corrected slant distances to reflector targets involve either continuous shortening or an oscillatory pattern of shortening and recovery these two patterns are considered to reflect the response of the volcanic edifice at near field and far field positions respectively at near field locations non elastic deformation is predominant over elastic deformation and rebound associated with changes in the magma conduit pressure are not detectable at far field locations elastic deformation is dominant allowing recognition of relaxation in the conduit magma pressure recognition of the two patterns assists monitoring of crater stability and may aid long range forecasting of future activity at the volcano

the explosive eruption of soufriere hills volcano montserrat west indies 17 september 1996 on 17 september 1996 the soufriere hills volcano started a 9 hour period of dome collapse involving 11 7 106 m dre of lava after 2 5 hours of quiescence a sustained explosive eruption began estimated eruption parameters are plume height at least 11 3 km and a maximum of 15 km 180 m s for launch velocities of ballistic clasts peak explosion pressure of 27 5 mpa magma water contents of 2 5 5 magma discharge rates from 2300 to 4300 m s ejecta volume of 3 2 0 9 106 m dre ejecta consists of pumice 1160 kg m higher density vesiculated ejecta 1300 to 2000 kg m dense glassy clasts 2600 kg m breccias cut by tuffisite veins and hydrothermally altered lithics the ejecta are interpreted as a conduit assemblage with evacuation of the conduit down to depths of about 3 to 5 km the eruption was triggered by unloading of a gas pressurised conduit due to dome collapse

q determined from local earthquakes in the south carolina coastal plain abstract coda q or qc is determined from the rate of coda decay in the coastal plain near charleston south carolina the mean of qc calculated from individual estmates is near 190 at 1 hz and increases to over 1650 at 10 hz a possible temporal change in qc is identified high values being associated with increased seismic activity during late 1977 temporal changes have been observed elsewhere and laboratory measurements of q under different stress states correlate high q with high stress a spatial variation in qc is identified increasing from west qc at 10 hz equal to 850 to east qc at 10 hz greater than 2100 across the coastal plain the demarcation of high to highest zones of qc is coincident with the western boundary of the innermost isoseismal of the charleston 1886 earthquake it is hypothesized that the 1886 earthquake was mislocated originally because of this spatial variation in energy attenuation that was unrecognized at that time

c and o isotope compositions of modern fresh water mollusc shells and river waters from the himalaya and ganga plain the aim of this paper is to unfold the relationship between the o and c isotope compositions of modern fresh water mollusc shells and water in order to refine the basis of interpretation for paleoenvironnemental reconstruction in the sub himalayan river basins large number of mollusc shells and associated host water from both running water and closed body of water were analysed including intra shell variability in a few cases the o isotopic compositions of river waters in the himalaya and ganga plain have a large range from 18 in the north of the high range up to 8 to 4 in the ganga plain 18o of rivers are also seasonally variable especially in foothills rivers whereas the seasonal contrast is smoothed out for the main himalayan rivers having large catchments o isotopic compositions of bulk shells aragonite vary between 15 and 5 average 18oara values are consistent with precipitation at equilibrium with host waters at a temperature range of 20 25 c suggesting that shell growth may be favoured during non monsoon conditions shells collected along the main himalayan rivers have 18o values uniformly distributed within 11 and 6 reflecting the minimal seasonal contrast shown by these rivers in contrast o isotopic compositions of shells from foothills rivers vary only by 4 this shows that depending on the type of river where the molluscs grow the information in term of 18o amplitude will be different for identical climatic conditions in closed or pond water bodies significant enrichment in 18o due to evaporation is observed the c isotopic compositions of river dissolved inorganic carbon dic decrease downstream from 0 to 10 reflecting input of soil derived alkalinity and plant productivity in the river 13c of shells are systematically lower than compositions calculated for equilibrium with river dic indicating that in addition to dic a significant fraction of carbon is derived from metabolic sources intra shell 13c are stable compared to the seasonal variability of dic suggesting that the pool of organic carbon changes throughout year

high late miocene pliocene elevation of the zhada basin southwestern tibetan plateau from carbonate clumped isotope thermometry the timing and pattern of tibetan pla teau rise provide a critical test of possible mechanisms for the development and sup port of high topography yet views range widely on the history of surface uplift to modern elevations of 4 5 km to address this issue we present clumped isotope ther mometry data from two well studied ba sins in central and southwestern tibet for which previous carbonate 18 o data have been used to reconstruct high paleoeleva tions from late oligocene to pliocene time clumped isotope thermometry uses mea surements of the 13 c 18 o bond ordering in carbonates to constrain the temperature t 47 and 18 o value of the water from which the carbonate grew these data can be used to infer paleoelevation by exploiting the systematic decrease of surface tempera ture and the 18 o based paleoaltimetry and with paleontological and isotopic data indicating the presence of cold adapted mammals living in a cold high ele vation climate we suggest that late neogene elevation loss across the zhada basin catch ment probably related to local expression of east west extension across much of the south ern tibetan plateau at this time

attenuation of short period p waves at mount st helens an increase of seismicity occurred at mount st helens between may and july 1998 with more than 900 events md 2 2 recorded by the pacific north west seismograph network this article describes an attempt to estimate the temporal and spatial variation in seismic attenuation using 200 microearthquakes that occurred before january 1995 april 1998 during and after august december 1998 the period of higher seismicity and recorded on three different one component seismic stations epicentral distances of the studied events ranged between 0 5 and 15 km we performed the analysis distinguishing the deep depth 5 5 km from shallow depth 5 5 km events we used the frequency decay method to estimate the quality factor q and station site correction s for p waves in the frequency bands 2 7 and 18 30 hz the results show that the attenuation varies from site to site systematically and decreases with depth lower qp values are obtained for focal depths less than 5 5 km moreover the spatial variations of qp show minimum values 30 in the crater area that are interpreted as due to a low density mass distribution under the crater we find that qp was 30 higher before the period of high seismicity than after this change may be attributed to an increase of pressure in the magma chamber producing new cracks and or reopening of pre existing cracks which are the most viable mechanisms for increasing attenuation

mid holocene palaeohydrochemistry and palaeohydrology of yamdrok yumtso southern tibetan plateau reconstructed from δ18o and δ13c of fossil shells of the gastropod radix auricularia palaeohydrochemical and palaeohydrological changes of lakes have seldom been reconstructed from the fossil shells of the gasropod radix auricularia which is a new and potentially high resolution

30 years in the life of an active submarine volcano a time lapse bathymetry study of the kick em jenny volcano lesser antilles effective monitoring is an essential part of identifying and mitigating volcanic hazards in the submarine environment this is more difficult than onshore because observations are typically limited to land based seismic networks and infrequent shipboard surveys since the first recorded eruption in 1939 the kick em jenny kej volcano located 8km off northern grenada has been the source of 13 episodes of t phase signals these distinctive seismic signals often coincident with heightened body wave seismicity are interpreted as extrusive eruptions they have occurred with a recurrence interval of around a decade yet direct confirmation of volcanism has been rare by conducting new bathymetric surveys in 2016 and 2017 and reprocessing 4 legacy datasets spanning 30 years we present a clearer picture of the development of kej through time processed grids with a cell size of 5m and vertical precision on the order of 1 4m allow us to correlate t phase episodes with morphological changes at the volcano s edifice in the time period of observation 7 09x106 m3 of material has been added through constructive volcanism yet 5 times this amount has been lost through landslides limited recent magma production suggests that kej may be susceptible to larger eruptions with longer repeat times than have occurred during the study interval behavior more similar to sub aerial volcanism in the arc than previously thought t phase signals at kej have a varied origin and are unlikely to be solely the result of extrusive submarine eruptions our results confirm the value of repeat swath bathymetry surveys in assessing submarine volcanic hazards

isotope paleontology growth and composition of extant calcareous species abstract isotope paleontology uses the isotopic composition of fossil remains of organisms to make inferences about the physical surroundings of growth of the organisms especially temperature and to obtain clues about life history and modes of growth in calcareous fossils oxygen isotopes are mainly used in the former and carbon isotopes in the latter however since physical surroundings and organism response are intimately associated both types of information are contained in each of the isotopic signals to explore the potential of isotope paleontology and to provide a basis for reconstruction a broad range of extant organisms has been studied taking the pioneering work of epstein and associates as a starting point results are summarized for a representative sampling of these studies with emphasis on work at the laboratories of the authors from the mid seventies to the present the organisms considered are nannoplankton benthic algae planktonic and benthic deep sea foraminifera larger foraminifera sponges corals bryozoans polychaetes arthropods bivalves gastropods cephalopods and vertebrates fish otoliths the survey broadly suggests that regarding oxygen isotopes materials tend to be precipitated close to equilibrium with the surrounding seawater as postulated by urey and that for carbon isotopes disequilibrium is the rule life spans growth rates differential seasonal growth and age of reproductive activity can be extracted under favorable circumstances from individual shells and skeletal parts in detail the interpretation of isotope records of individual shells is quite complicated and simple models will fail to give satisfactory results in many or most cases

basin morphology and seismic stratigraphy of lake donggi cona north eastern tibetan plateau china basin morphology and depositional stratigraphy of lake donggi cona on the north eastern tibetan plateau has been studied with echo depth sounding and shallow seismic sub bottom profiling the basin is a pull apart structure situated at the highly active kunlun fault it is characterised by a 92 m deep graben structure in the western part of the lake basin and a shallow eastern lake part the latter filled up with fluvial sediments from a large alluvial plain three prominent morphological levels were identified at 24 m 39 m and 57 m below present lake level they were partly created by basin subsidence while the deposition of prograding delta sediments primarily formed the morphological steps the inherited tectonic structures control on going neotectonic activity which seems to have only minor influence on present basin morphology the basin is filled by sediments of at least 30 m thickness in the depocentre three major depositional units can be distinguished in comparison with lithological changes in a sediment core they give evidence of pronounced lake level fluctuations and dramatic changes in lake volume a numerical age datum of w19 cal ka bp at the base of the sediment core allows a tentative reconstruction of late glacial to holocene lake development a very low base level preceded a time of delta formation during higher lake level i e w26 m lower than present during last glacial maximum creating a lake of only 18 of its present size at the transition to holocene the lake level rose very quickly changing to a deep lake environment thus transgression may have promoted maximum lake stands

attenuation of short period seismic waves at etna as compared to other volcanic areas codaq for etna volcano is frequency dependent and theq frequency pattern and the numerical values ranging from about 100 at 1 hz to about 300 at 18 hz are similar to the values obtained for other volcanoes campi flegrei aeolian islands and hawaii moreover the frequency pattern and the numerical values of coda quality factor for most of the seismically active zones of italy are very different from those of the volcanic zones

quaternary environmental changes in the drylands of china a critical review abstract this paper reviews our current understanding of quaternary climate and landscape changes in the desert areas of northern china a key portion of the middle latitude drylands on earth combining earlier studies with our recent research and experience we offer a comprehensive picture of the state of chinese deserts during the quaternary and in the interest of enhancing future research identify knowledge gaps and areas of uncertainty lacustrine deposits found over an area ranging from china s western taklamakan desert to the eastern hunshandake sandy lands suggest that extensive lakes occurred in china s deserts during the pleistocene analysis of digital elevation models from srtm shuttle radar topography mission data supports this interpretation and shows the significant extent of these former lakes new estimates of mean annual evaporation of ca 1000 mm from lake surfaces and ca 100 mm from land surfaces confirms that local and regional rainfall is critical for maintenance of desert lakes in this temperate zone especially during intervals when the mean annual rainfall is more than 100 mm rapid shifts between sand seas and lakes in geologically and environmentally diverse settings suggest that the drylands of china are very sensitive ephemeral systems and not long lasting as previously thought available chronologies suggest that there were large lakes in the western taklamakan desert and the chadamu basin during mis marine isotope stage 3 at 30 ka probably related to a period of strong influence of northern hemispheric westerly winds channels and elevation models revealed by srtm data and remains of lacustrine sediments also indicate that there was a large lake in the hunshandake sandy lands in the eastern portion of the desert belt during the quaternary there is significant evidence that during the middle holocene strong summer monsoons led to a relatively large increase in moisture availability in the entire desert belt of northern china lacustrine records from the badain jaran desert in western inner mongolia suggest that it was generally dry before 10 cal ka becoming wetter from 10 to 4 cal ka and dry again afterwards study of palaeosols widely occurring in dune stratigraphy in the eastern portion of the desert belt suggests that there was a period of wet and warm climate in this region during the mid holocene optimum at a minimum between 6 ka and 4 ka but possibly lasting longer recent observations dealing with the generation and transport of dust from central asia indicate that the causal relationship between sand seas and loess sequences is not as close as previously assumed these results suggest that there is an urgent need to examine whether the frequency and amplitude of climatic variation in chinese deserts are somehow similar to that having occurred in the sahara desert of north africa deserts in northern china were also important focal regions for neolithic cultures during intervals when environmental conditions supported a denser vegetative cover there is evidence that some areas of woody vegetation to the west of badain jaran desert were deforested by humans by ca 4000 yr b p although it is still debatable whether humans have had a significant impact in other areas at that time opinions on the severity of desertification vary and are sometimes contradictory due to the lack of long term field based investigations

palaeoenvironment and palaeoclimate of the middle miocene lake in the steinheim basin sw germany a reconstruction from c o and sr isotopes of fossil remains a differentiated reconstruction of palaeolimnologic environmental and climatic conditions is presented for the middle miocene long term freshwater lake 14 3 to 13 5 ma of the steinheim basin on the basis of a combined c o and sr isotope study of sympatric skeletal fossils of aquatic and terrestrial organisms from the lake sediments the oxygen isotope composition for lake water of the steinheim basin 18oh2o 2 0 0 4 vsmow n 6 was reconstructed from measurements of 18opo4 of aquatic turtle bones the drinking water calculated from the enamel of large mammals proboscideans rhinocerotids equids cervids suids has 18oh2o values 18oh2o 5 9 1 7 vsmow n 31 typical for middle miocene meteoric water of the area this 18oh2o value corresponds to a mean annual air temperature mat of 18 8 3 8 c calculated using a modern day 18oh2o mat relation hence large mammals did not use the lake water as principal drinking water in contrast small mammals especially the then abundant pika prolagus oeningensis drank from 18o enriched water sources 18oh2o 2 7 2 3 vsmow n 7 such as the lake water differences in sr and o isotopic compositions between large and small mammal teeth indicate different home ranges and drinking behaviour and support migration of some large mammals between the swabian alb plateau and the nearby molasse basin while small mammals ingested their food and water locally changes in the lake level water chemistry and temperature were inferred using isotopic compositions of ostracod and gastropod shells from a composite lake sediment profile calcitic ostracod valves ilyocypris binocularis 18o 1 7 1 2 vpdb 13c 0 5 0 9 vpdb n 68 and aragonitic gastropod shells gyraulus spp 18o 2 0 1 3 vpdb 13c 1 1 1 3 vpdb n 89 have 18o and 13c values similar to or even higher than those of marine carbonates 13c values of the biogenic carbonates parallel lake level fluctuations while 18o values scatter around 2 2 and reflect the short term variability of meteoric water inflow vs longer term evaporation 87sr 86sr ratios of aragonitic gyraulus spp gastropod shells parallel the lake level fluctuations reflecting variable inputs of groundwater and surface waters using a water 18oh2o value of 2 0 vsmow water temperatures calculated from skeletal tissue 18o values of ostracods are 16 7 5 0 c gastropods 20 6 5 6 c otoliths 21 8 1 4 c and fish teeth 17 0 2 7 c the calculated mat 19 c lake water temperatures 17 to 22 c and the 18o enriched water compositions are indicative of warm temperate climatic conditions possibly with a high humidity during this period vegetation in the area surrounding the basin was largely of the c3 type as indicated by carbon isotopic compositions of tooth enamel from large mammals 13c 11 1 1 1 vpdb n 40

potential forcing mechanisms of holocene lake level changes at nam co tibetan plateau inferred from the stable isotopic composition of shells of the gastropod radix the timing of lake level fluctuations on the tibetan plateau and their relationship with climatic changes is still under debate and the main reason for this is the lack of suitable archives for reconstructing the paleohydrology and paleoclimatology of the lakes here we present the results of analyses of the shell geochemistry of radix sp from an exposed terrace of nam co lake on the south central tibetan plateau optically stimulated luminescence osl dating reveals that deep water lacustrine sediments formed between ca 4 4 and 2 2 ka suggesting a high and stable lake level significantly above the present the results of sr ca 13c and 18o analyses of the fossil shells of radix sp indicate that during the mid to late holocene lake level variations in nam co were mainly controlled by variations in the indian summer monsoon a trend of decreasing evaporation also played an important role comparison with other results suggests a consistent pattern of mid to late holocene lake level changes acro

environmental change in the vicinity of the neolithic wetland settlement pestenacker s germany during the last 6600 years abstract pestenacker and the adjacent neolithic wetland sites unfriedshausen and pestenacker nord in southern germany belonged to the altheim culture from around 5750 5350 years cal bp in contrast to contemporaneous pile dwellings the houses of pestenacker were constructed at ground level in a wetland environment only little is known about the environmental and hydrological conditions in the direct vicinity of the settlement and how they changed in time to find detailed answers to these questions stratigraphy sedimentology microfossils geochemistry and stable isotopes of a sediment profile immediately to the west of the settlement were studied an age model comprises five radiocarbon dates and dates the base of the profile to about 6600 years cal bp ostracods and aquatic gastropods were frequent only in the basal part of the profile ostracod taxa typical for open water conditions point to higher humidity especially at 6120 5860 years cal bp and 5750 5370 years cal bp sedimentology and organic carbon isotope data confirm this observation thereafter open water habitats disappeared while increasing numbers of non aquatic gastropods occur and soil formation is indicated by elevated 15 n values we conclude that during the time of settlement an open water body existed near by that disappeared shortly after the settlement was abandoned however the spatial extent of this water body still remains to be clarified

elastic deformation models of krafla volcano iceland for the decade 1975 through 1985 the dynamics of the shallow magma reservoir at krafla volcano in ne iceland have been analyzed with three types of elastic models based on over 70 surveys of tilt and displacement made from 1975 to 1985 a period of continuous volcano tectonic activity modeling results are integrated with geophysical and geological information to estimate the position geometry and volume change of magma reservoir domains subjected to periodic inflation and deflation dominating influences on magma reservoir dynamics are examined in the context of activity in krafla s associated rift system and the deformation of its caldera from 1975 1985 rather than the fluid filled cavity concept of mogi 1958 and most recent workers our models are idealized as strained regions with spherical double spherical or general ellipsoidal symmetry the models are mathematically generalized from that of mogi 1958 and are derived by inversion of displacements model results from different displacement components are remarkably consistent although models based on vertical displacements typically have errors of fit much closer to expected measurement errors than those based on tilt or horizontal displacements about one half of the double sphere and ellipsoid models have significantly better fits than single sphere models double sphere model results are consistent with a 2 to 3 km center to center separation of magma storage zones from at least 2 km to 4 km depth by portions of the fissure system as implied by s wave attenuation patterns for 1976 1977 however all models suggest pressurization zones of more limited extent than possible domains of storage inferred from s wave attenuation ellipsoid models typically implied unrealistically shallow depths of magma storage caldera inflation rates decreased after january 1978 when the caldera periodically reinflated to its level prior to the initial december 1975 deflation event from 1975 1980 the volume and duration of inflation between deflation events was strongly correlated with the volume of the previous deflation after 1980 there was a significant increase in the duration of inflation periods and a decrease in rates of caldera inflation and fissure system widening consistent with these results the magma reservoir is conceptualized as a hot rock mass containing numerous magma chambers and pressure sensitive conduits connecting the chambers and deep magma sources magma is injected into the fissure system at critical pressures determined by the confining stress and rock mass strength the duration and volume of inflation required to reach a critical pressure threshold is largely dependent on the volume of magma released in the previous deflation reduction of the extension rate across the krafla fissure system after 1980 suggests that extensional forces were also reduced a resultant rise of confining pressure on the magma reservoir and a reduced capacity of the fissure system to accommodate dike injection in combination would have increased critical stress levels for reservoir deflation and reduced the pressure gradient driving magma supply from deep sources

abrupt changes in the asian southwest monsoon during the holocene and their links to the north atlantic ocean during the last ice age the indian ocean southwest monsoon exhibited abrupt changes that were closely correlated with millennial scale climate events in the north atlantic region1 2 3 suggesting a mechanistic link in the holocene epoch which had a more stable climate the amplitude of abrupt changes in north atlantic climate was much smaller and it has been unclear whether these changes are related to monsoon variability here we present a continuous record of centennial scale monsoon variability throughout the holocene from rapidly accumulating and minimally bioturbated sediments in the anoxic arabian sea our monsoon proxy record reveals several intervals of weak summer monsoon that coincide with cold periods documented in the north atlantic region4 including the most recent climate changes from the medieval warm period to the little ice age and then to the present we therefore suggest that the link between north atlantic climate and the asian monsoon is a persistent aspect of global climate

chemical and isotopic o h c composition of surface waters in the catchment of lake donggi cona nw china and implications for paleoenvironmental reconstructions abstract the oxygen hydrogen and carbon isotope ratios and major and trace element concentrations of surface waters are reported for the catchment of lake donggi cona qinghai province china the chemistry of the surface waters in the southeastern catchment is reflecting the dissolution of carbonate rocks whereas thermal waters add sodium and chlorine to the waters in the northern catchment the dongqu river draining the southeast catchment contributes 87 to 94 to the water budget of the lake thermal waters and waters from the northern catchment add 6 to 13 the combination of hydrogen and oxygen isotopes provides evidence that only small amounts of recycled lake water contribute to the precipitation in the catchment most of the moisture may be transported by the east asian summer monsoon or an eastern branch of the south asian monsoon into the donggi cona region from oxygen isotope ratios it is calculated that about 45 of the lake water input is evaporated and 55 leaves the lake through a channeled outflow the carbon isotope ratios identifies microbial respiration of organic matter probably in soils and sediments of the catchment as the major source of dissolved inorganic carbon in most surface waters and the lake an isotope effect from biological processes in the lake is minor and can be neglected in order to explain isotope ratios of inorganic carbon in lake water the results imply that oxygen isotope ratios in the lake sediment archives mainly mirror the relation between precipitation and evaporation p e which may be controlled by changes in the global water cycle like monsoon intensity or by tectonically driven local changes affecting the outflow flux a comparison between lake archives based on ostracod shells and the modern system indicates similar 18o values for the lake water since 4 3 ka but different 13cdic values this discrepancy between carbon isotope ratios in ostracod shells and modern lake water samples may be due to thermal waters with high 13cdic emerging near the coring site it is suggested that carbon isotopes of ostracods from a sediment drill core reflect the activity of a local thermal spring at the lake bottom whereas oxygen isotopes provide evidence for an open lake system since about 11 ka and that the climate and environment of the donggi cona region changed very little over the last 4300 years

late quaternary hydrological changes inferred from lake level fluctuations of nam co tibetan plateau china abstract this paper discusses the range of lake level changes using hydro acoustic techniques and sediment core data for lake nam co in central tibet china this second largest tibetan lake is situated at an elevation of 4718 m a s l lake level changes with different high stands documented by beach remnants are widespread on the tibetan plateau and also in lake nam co they indicate significant changes in the hydrological system triggered by the monsoonal circulation using hydro acoustic techniques submerged beach remains at approximately 10 15 m 30 m 45 m 70 m and 95 m below present day lake level were detected indicating a more negative water balance than today the 10 15 m lake level is dated to an age equal to the little ice age all deeper lake levels are assumed to have been formed prior to 10000 cal bp folded older sediments detected in the hydro acoustic profiles indicate a possible larger extent of the glaciers during or prior to the last glacial maximum lgm this is followed by a low stand or even by possible desiccation of the entire lake basin during or after the lgm

from precipitation to runoff stable isotopic fractionation effect of glacier melting on a catchment scale stable isotope variability and fractionation associated with transformation of precipitation accumulation to firn to glacial river water is critical in a variety of climatic hydrological and paleoenvironmental studies this paper documents the modification of stable isotopes in water from precipitation to glacier runoff in an alpine catchment located in the central tibetan plateau isotopic changes are observed by sampling firnpack profiles glacier surface snow ice meltwater on the glacier surface and catchment river water at different times during a melt season results show the isotopic fractionation effects associated with glacier melt processes the slope of the d 18o regression line and the deuterium excess values decreased from the initial precipitation to the melt impacted firnpack slope from 9 3 to 8 5 and average d excess from 13 4 to 7 4 the slope of the d 18o line further decreased to 7 6 for the glacier runoff water the glacier surface snow ice from different locations which produces the main runoff had the same d 18o line slope but lower deuterium excess by 3 9 compared to values observed in the firnpack profile during the melt season the d 18o regression line for the river water exhibited a lower slope compared to the surface snow ice samples although they were closely located on the d 18o plot isotope values for the river and glacier surface meltwater showed little scatter around the d 18o regression line although the samples were from different glaciers and were collected on different days results indicate a high consistency of isotopic fractionation in the d 18o relationships as well as a general consistency and temporal covariation of meltwater isotope values at the catchment scale copyright 2013 john wiley sons ltd

seasonal stable isotope evidence for a strong asian monsoon throughout the past 10 7 m y o of wet season rainfall was signi cantly morenegative 29 5 smow prior to 7 5 ma than after 26 5 smow if this change is attributable to a lessening of the amounteffect in rainfall this agrees with oral and soil geochemical datathat indicate increasing aridity beginning at 7 5 ma keywords tibetan plateau monsoon stable isotopes paleohydrology seasonality introductionthe tibetan plateau is the engine that drives the modern asianmonsoon by generating a high altitude region of low pressure in thesummer as the plateau heats and a region of high pressure in the winteras the plateau cools hastenrath 1991 during the summer warm airrises from the plateau pulling moist air off the ocean across the indiansubcontinent and into the highlands this results in heavy summer rain fall on the subcontinent the opposite occurs in the winter resultingin cold dry air spilling off the plateau and effectively excluding rainfrom the subcontinent thus the presence of a strong wet season dry season alternation implies the presence of a plateau broad and highenough to drive the monsoon the timing of the uplift of the plateau remains a matter of con siderable debate because there are few direct indicators of paleotopog raphy in the geologic record consequently past workers in tibet re lying on indirect indicators of uplift have proposed dates ranging from40 to 3 4 ma on the basis of initiation of potassic volcanism chunget al 1998 turner et al 1993 or extension on the plateau harrisonet al 1995 coleman and hodges 1995 changes in marine sedimen tation rates burbank et al 1993 sediment types rea et al 1998 or biota nigrini and caulet 1992 kroon et al 1991 and changesin stable carbon isotope and palynological patterns on the indian sub continent quade et al 1989 chen 1981 although different areasof the plateau may have risen at different times many workers haveinferred rapid simultaneous uplift of large areas of the plateau at 7 8ma by a process such as lithospheric delamination molnar et al 1993 this inference was based on the following approximately coevalphenomena a major change in plant communities of the indian sub continent quade et al 1989 and shifts in marine upwelling patternsthat are linked to an intense monsoon kroon et al 1991 althoughthere is strong evidence for signi cant climate change at 7 8 ma it isunclear whether this is the onset of the monsoon the oral transitionseems to have been a global rather than local phenomenon cerling etal 1997 and monsoonally driven upwelling may have already beenpresent by 10 12 ma nigrini and caulet 1992 kroon et al 1991 because there is an intimate association between the intense sea sonality of the modern monsoon and a high tibetan plateau and be cause evaporation can be unambiguously recognized in the d

chlorine isotopes of thermal springs in arc volcanoes for tracing shallow magmatic activity the evaluation of the status of shallow magma body i e from the final intrusion stage to quiescence and back to activity one of the key parameters that trigger and sustain volcanic eruptions has been challenging in modern volcanology among volatile tracers chlorine cl uniquely exsolves at shallow depths and is highly hydrophilic consequently cl enrichment in volcanic gases and thermal springs has been proposed as a sign for shallow magmatic activities however such enrichment could also result from numerous other processes e g water evaporation dissolution of old chloride mineral deposits seawater contamination that are unrelated to magmatic activity here based on stable isotope compositions of chloride and dissolved inorganic carbon as well as previous published 3he 4he data obtained in thermal springs from two recently erupted volcanoes la soufriere in guadeloupe and montagne pelee in martinique in the lesser antilles arc we show that the magmatic cl efficiently trapped in thermal springs displays negative 37cl values 0 65 0 65 consistent with a slab derived origin but distinct from the isotope compositions of chloride in surface reservoirs e g seawater local meteoric waters rivers and cold springs displaying common 37cl values of around 0 using this 37cl difference as an index of magmatic cl we further examined thermal spring samples including a 30 year archive from two thermal springs in guadeloupe covering samples from its last eruption in 1976 1977 to 2008 and an island wide sampling event in martinique in 2008 to trace the evolution of magmatic cl in the volcanic hydrothermal systems over time the results show that magmatic cl can be rapidly flushed out of the hydrothermal systems within 30 to 80 years after the eruption much quicker than other volatile tracers such as co2 and noble gases which can exsolve at greater depths and constantly migrate to the surface because arc volcanoes often have well developed hydrothermal systems where magmatic cl is easily transferred to the surface following its exsolution from shallow magma body we suggest that 37cl has great potential to be a unique proxy to monitor the cessation and revival of infrequent arc volcanoes particularly at centennial time scales

the geological evolution of the tibetan plateau the geological evolution of the tibetan plateau is best viewed in a context broader than the india eurasia collision zone after collision about 50 million years ago crust was shortened in western and central tibet while large fragments of lithosphere moved from the collision zone toward areas of trench rollback in the western pacific and indonesia cessation of rapid pacific trench migration 15 to 20 million years ago coincided with a slowing of fragment extrusion beyond the plateau and probably contributed to the onset of rapid surface uplift and crustal thickening in eastern tibet the latter appear to result from rapid eastward flow of the deep crust probably within crustal channels imaged seismically beneath eastern tibet these events mark a transition to the modern structural system that currently accommodates deformation within tibet

holocene variations in the asian monsoon inferred from the geochemistry of lake sediments in central tibet we present a record of monsoon variations for the early and middle holocene that is inferred from the geochemistry of sediment cores from ahung co a lake in central tibet the resolution of this record is better than 50 yr and the age model is derived from radiocarbon ages of terrestrial charcoal which eliminates errors associated with the lake hard water effect we made down core geochemical measurements of carbonate organic carbon c n and 13c of bulk organic matter 13c and 18o of carbonate and dolomite proxy calibration and modern water balance reconstruction show that these are proxies for lake depth and the amount of monsoon precipitation we find that lake level and monsoon precipitation have been decreasing at ahung co since the early holocene 7500 cal yr b p superimposed on this trend are rapid declines in monsoon rainfall at 7000 7500 and 4700 cal yr b p and seven century scale wet dry oscillations the cores do not contain sediment from the last 4000 yr surface sediments from the lake accumulated during the 20th century however from this we argue that lake levels have risen again recently following a late holocene dry period

overview of the eruption of soufriere hills volcano montserrat 18 july 1995 to december 1997 the onset of phreatic volcanic activity at the soufriere hills volcano montserrat on 18 july 1995 followed a three year period of heightened volcano seismic activity beneath the island phreatic explosions gave way to continuous eruption of juvenile andesitic magma in the form of a lava dome on or around 15 november 1995 magma production rate has varied leading to changes in eruptive style an explosive eruption on 17 september 1996 followed a period of enhanced dome growth and large scale gravitational collapses from its eastern flank increasing dome volume led to stressing and overtopping of the confining crater walls to the southwest north and west during early 1997 sustained high magma production rate since june 1997 has led to three periods of major gravitational dome collapses followed by vulcanian explosive eruptions dome growth re started immediately after the cessation of the latest of these explosive phases in october 1997 and continues as of december 1997

oxygen and carbon isotope ratios in gastropod shells as indicators of paleoenvironments in the afar region of ethiopia abstract the oxygen and carbon isotope ratios in the shells of ancient freshwater gastropods coupled with geological geographical and hydrological data from their area and time of origin can yield information concerning general climatic conditions prevailing at the time the gastropod lived in addition sequential oxygen isotope analyses along the growth spiral of the shell provides indications of seasonal variability in the life span of the organisms such data were collected for some freshwater gastropods collected from two lakes and two springs in the afar region of ethiopia spanning late pleistocene to modern age episodes of high rainfall in the ethiopian highlands were clearly evident in the depleted 18o values in some shells whiel arid spells produced enriched levels in others hot springs introduced an added complication to the isotope record this study on a region of particularly complex hydrology and highly variable environmental history indicates the utility of stable isotope analyses as proxies for past climates but also emphasizes the problems involved

stable isotopes in fossil mammals fish and shells from kunlun pass basin tibetan plateau paleo climatic and paleo elevation implications we report the results of a stable isotope study of a late pliocene fauna recently discovered in the kunlun mountain pass area similar to 4700 m above sea level on the northern tibetan plateau the delta c 13 values of enamel samples from modern herbivores from the kunlun pass basin range from 14 8 to 10 6 with a mean of 12 0 0 7 parts per thousand indicating pure c3 diets consistent with the current dominance of c3 vegetation in the area in contrast enamel samples from fossil herbivores yielded delta c 13 values of 5 4 parts per thousand to 10 2 parts per thousand with a mean of 7 9 1 3 parts per thousand significantly higher than those of modern herbivores in the area the higher delta c 13 values indicate that these ancient herbivores unlike their modern counterparts had a variety of diets ranging from pure c3 to mixed c3 c4 vegetation the local ecosystems in the kunlun pass area in the late pliocene likely included grasslands that had small amounts of c4 grasses the delta o 18 values of enamel from large herbivores shifted to higher values after the late pliocene indicating a significant change in the delta o 18 of local meteoric water we estimate that there has been approximately 3 2 parts per thousand increase in annual delta o 18 values of meteoric water since similar to 2 3 ma most likely driven by changes in the regional hydrological cycle possibly as a result of tectonic and climate change the delta o 18 values of fossil fish teeth bones and gastropod shells along with abundance of aquatic plants and other invertebrate fossils clearly indicate that the kunlun pass basin once had plenty of water and was occupied by a freshwater lake in the late pliocene our isotope data from both terrestrial and aquatic fossils suggest that the kunlun pass basin was a hospitable place with a much warmer and wetter climate in the late pliocene very different from today s rock desert and cold steppe environments the mean annual temperature in the late pliocene estimated from the delta o 18 of fossil bone carbonate and paleo water was about 10 8 degrees c much higher than the present day mean annual temperature in the basin if valid the estimated temperature change would imply that the elevation of the basin has increased by similar to 2700 1600 m since similar to 2 3 ma c 2008 elsevier b v all rights reserved

slowing extrusion tectonics lowered estimate of post early miocene slip rate for the altyn tagh fault abstract determination of long term slip rate for the altyn tagh fault is essential for testing whether asian tectonics is dominated by lateral extrusion or distributed crustal shortening previous slip history studies focused on either quaternary slip rate measurements or pre early miocene total offset estimates and do not allow a clear distinction between rates based on the two the magmatic and metamorphic history revealed by shrimp zircon dating of clasts from miocene conglomerate in the xorkol basin north of the altyn tagh fault strikingly matches that of basement in the southern qilian shan and northern qaidam regions south of the fault this match requires that the post early miocene long term slip rate along the altyn tagh fault cannot exceed 10 mm year supporting the hypothesis of distributed crustal thickening for post early miocene times this low long term slip rate and recently documented large pre early miocene cumulative offset across the fault support a two stage evolution wherein asian tectonics was dominated by lateral extrusion before the end of early miocene and since then has been dominated by distributed crustal thickening and rapid plateau uplift

intra seasonal hydrological processes on the western tibetan plateau monsoonal and convective rainfall events at 7 5 ka abstract the tibetan plateau and the himalayas influence monsoonal circulation patterns and represent the water towers of humanity modern coupling of atmospheric circulation and the hydrological cycle over and on the plateau can be observed and delineated and the factors that control lake levels can be identified recent monitoring of lakes has shown that many have grown for decades due to higher meltwater inflow or stronger rainfall from different sources depending on the location the long term dynamics of lakes however can be best described by using high resolution climate archives we focus here on the often controversial discussion of holocene lake development and use the bangong co drainage basin on the western tibetan plateau as a case study we aim to identify the factors that influence lake level such as monsoonal or convective precipitation and meltwater to accomplish this shells of the aquatic gastropod genus radix were collected from an early middle holocene sediment sequence in the nama chu subcatchment of the eastern bangong co and sclerochronlogical isotope patterns for five shells were obtained at a weekly to submonthly resolution our data suggest that at ca 7 5 ka monsoonal rainfall was higher than it is today however summer precipitation was not continuous but occurred as extended moisture pulses this result implies that the northern boundary of the sw asian monsoon was similar to that today we identify convective rainfall events significantly stronger than today and relate these events to higher soil moisture and larger lake surface areas under higher insolation conditions the regional amount of meltwater corresponds with the westerly derived winter snowfall exceptionally heavy 13c values archived in the shells were likely at least partly triggered by biogenic methane production we suggest that our approach is suitable for studying other lake systems on the tibetan plateau from which fossil radix shells can be obtained

magma storage region processes inferred from geochemistry of fe ti oxides in andesitic magma soufriere hills volcano montserrat w i analyses of fe ti oxides help constrain models of magma storage region processes for the soufriere hills volcano montserrat w i and provide clear evidence of the nature of transient heating events in the magma storage region to constrain timescales of magma heating and remobilization the tio2 zoning patterns in a time series of natural titanomagnetites were compared with those produced in controlled phase equilibrium experiments on the andesite most samples of andesite erupted from 1995 to 2002 contain titanomagnetite crystals with uniform core compositions tio278 wt many crystals are characterized by rimward increases in tio2 interpreted to be ti diffusion gradients caused by heating of the andesite by invading basaltic magma some andesites erupted during periods of the highest observed mass eruption rate however contain titanomagnetite with uniformly low tio2 contents from core to rim the observation that no ti diffusion gradients and no elevated core tio2 contents occur in the vast majority of titanomagnetite grains in magma batches that were erupted more than 2 years after the onset of the present eruption strongly suggests first that heating of the batches of andesite occurred just before eruption and second that injection of basaltic magma has continued throughout the eruption heat but little mass may be transferred from the invading basalt to the andesite in the magma storage region by injection of dikes or formation of sills ponding of basaltic magma at the base of a pre existing andesitic magma storage region is the simplest explanation consistent with observations the fe ti oxide data strongly suggest that an internal conduit within the andesitic magma storage region carries magma from the zone of heating to the overlying conduit which carries the magma through the upper arc crust in this model the magma chamber is being emptied from the bottom at the contact between pre existing andesite and newly intruded basalt

sensitivity of climate to late cenozoic uplift in southern asia and the american west numerical experiments experiments with general circulation models with no mountains half mountains and full modern mountains show the sensitivity of atmospheric circulation patterns to progressive amounts of uplift the experiments were motivated by geologic evidence for large kilometer scale uplift in the late cenozoic in southern asia and the american west particularly within the last 10 m y in january the amplitude of the mid latitude upper tropospheric planetary waves increased with uplift and the low level winds were progressively blocked or diverted around the topographic features in july the progressive uplift caused monsoonlike circulations to develop in the vicinity of the colorado and tibetan plateaus atmospheric heating rates midtroposphere vertical motion and upper tropospheric planetary wave amplitudes varied approximately linearly with progressive uplift these results suggest that geologically recent kilometer scale uplift may have had climatic consequences comparable in magnitude and pattern to those of earlier stages of uplift comparison of the simulated climatic effects of uplift with the geologic evidence for late cenozoic climatic change especially for the last 10 m y is given in accompanying papers

a holocene molluscan succession from floodplain sediments of the upper lena river lake baikal region siberia floodplainsediments of the upperlenariver near basovo in south central siberia have yielded the most detailed holocenemolluscansuccession yet reported from the entire eastern palaearctic over 72 500 shells from at least 28 species of terrestrial and 23 species of freshwater mollusc have been recovered an abundance and diversity far higher than previously reported from the region the molluscan assemblages are dominated by land snails especially members of the genus vallonia represented by five species including vallonia tenuilabris and two poorly known species vallonia kamtschatica and vallonia cf chinensis other noteworthy species recovered include gastrocopta theeli carychium pessimum vertigo extima southernmost record vertigo microsphaera and the first asian records of three other taxa vertigo geyeri vertigo genesii and vertigo parcedentata illustrations are provided for the critical species since opinions differ about the status of various taxa and the correct names that should be used the molluscan assemblages show clear successional trends during the early to mid holocene reflecting episodes of dryness wetness on the floodplain drier conditions at ca 6350 14c yr bp coincide with major changes in the archaeological record seen at other sites in the region but it remains unclear whether the two are linked a prominent charcoal rich horizon dated to ca 2800 14c yr bp marks a burning event in the catchment which resulted in a two fold increase in sediment accumulation rate remains of small mammals occurred throughout the sequence including a tooth of microtus cf maximowiczii possibly the first occurrence of ungar vole west of lakebaikal the faunal analyses have been integrated with a detailed pedological study of the sedimentary profile and a chronology was obtained by means of 12 ams radiocarbon dates this study provides the first detailed palaeoecological information relating to holocenemolluscan assemblages from the cis baikalregion and lays the foundation for future work in the eastern palaearctic

a study of source parameters site amplification functions and average effective shear wave quality factor qseff from analysis of accelerograms of the 1999 chamoli earthquake himalaya the accelerograms of the 1999 chamoli earthquake and nine of its aftershocks which occurred in uttaranchal himalaya have been analyzed to investigate their source parameters the site amplification functions and the average effective shear wave quality factor qseff in the region the fault plane solution of the main shock is obtained using the spectral amplitudes of sh waves approximated by transverse components of accelerograms of the high energy packets observed in the accelerograms of the main shock it is found to be comparable with the reported solutions in other studies similarly the other source parameters viz seismic moment 5 03 1 7 1025 dyne cm stress drop 65 bars source duration 5 2 s and moment magnitude 6 4 estimated for the main shock are consistent with the values obtained in other studies the stress drops estimated for the aftershocks vary from 23 bars to 153 bars and the seismic moment from 1 4 1023 dyne cm to 2 9 1023 dyne cm the average estimated values of the effective shear wave quality factor qseff vary from 655 359 in the uttaranchal sector of himalaya and 1475 130 in the delhi region in general the qseff value increases with an increase in the epicentral distance reflecting the penetration of the waves into deeper layers of the crust as the epicentral distance of the observation point increases these values of qseff indicate that in general the curst is at low temperatures that will promote brittle behavior and conditions for episodic failure as compared to creep under the accumulated strains from plate collision at the himalaya plate boundary the site amplification characteristics at sites have been identified from the frequency bands of significant amplification observed in the spectral ratios of the horizontal to the vertical component records the decay of peak ground acceleration pga values with distance has been investigated using the empirical regression curves vis a vis the site amplification factors

hydrological and climatic changes in deserts of china since the late pleistocene article i nfo article history large areas in western china were wetlands or less arid between 40 and 30 ka corresponding to the greatest lake period on the adjacent tibetan plateau during the last glacial maximum some of these western chinese deserts again experienced wetter conditions however at the same time the sandy lands in the eastern chinese desert belt experienced an activation of aeolian dunes while interpretations of the mid holocene environment in the deserts of china are controversial it is quite likely that it was more humid not only in the eastern areas influenced by monsoon climate systems but also in the western deserts where moisture is currently associated with westerlies evaluation of lacustrine records in the lakes recharged by dryland rivers and the complex interactions of these systems as well as other paleoenvironmental proxies such as the artemisia chenopodiaceae ratio should be interpreted with greater caution facing the highlighted uncertainties in our understanding of climate changes in chinese deserts it is hoped that this special issue will improve our knowledge considerably

a scattering model to explain seismic q observations in the lithosphere between 1 and 30 hz observations of lithospheric q for shear waves in the range 1 30 hz reported in the literature are examined using a scattering model consisting of randomly distributed spheres for the single scattering approximation i have assumed 1 q 1 q sub i gv omega where q sub i is the intrinsic q due to anelasticity v is the velocity of shear waves omega is angular frequency and g is the turbidity g is taken as a constant in this paper since g integral n a sigmada where n a da is the number of scattering spheres of radius a unit volume and sigma is the scattering cross section for a sphere this suggests that geometrical scattering dominates this will be true for ka 1 where k is wavenumber based on this criterion and the observation that q is large i e g small at a frequency of 0 05 hz a is of the order of magnitude 1 10 km fits of observations of shear wave q from japan and central asia indicate that q sub i 2000 500 for the lithosphere of both regions g 0 01 km for the japan observations and g 0 005 km sup 1 for central asia

vertical ground deformation on mount etna 1975 1980 we present the results of repeated precise leveling between the years 1975 and 1980 of an 11 km traverse over the summit of mount etna together with data from a network of dry tilt stations measured between 1976 and 1980 both methods demonstrate that little vertical movement occurs except on fresh lava flows which show a consistent pattern of downward movement interpreted as compaction and downhill sliding of lava after it has solidified other small vertical movements of a few centimetres recorded on the leveling traverse appear to be related to activity particularly the eruptions from a new vent area on the southeast side of the summit in 1978 and 1979 models of the recorded movement indicate that a small amount of magma was already stored in a dike below this eruption site as much as two years before it was erupted although the bulk of the magma for these eruptions was not stored in the upper few kilometres of the volcano the latter conclusion is supported by the dry tilt data which are dominated by local movements of 10 to 20 microradians with no consistent pattern of movement over the whole volcano

the elevation history of the tibetan plateau and its implications for the asian monsoon abstract the determination of the evolving palaeoaltitude of the tibetan plateau since the india eurasia collision underpins our understanding of how orography in central asia affects the intensity of the monsoon and hence global climate change palaeoaltitudes however cannot be measured directly and need to be inferred from proxy observations that are usually model dependent differing tectonic models for the behaviour of the lithosphere during continental collision have contrasting implications for the elevation of the plateau however two techniques recently employed for determining palaeo elevation are independent of tectonic models the first involving the variation with altitude of oxygen isotopes in precipitation and the second involving the change of leaf morphology with moist static energy of the atmosphere elevation studies have focused on southern tibet largely due to the relative ease of access to the region there is a remarkable unanimity amongst the diverse techniques applied that the altitude of the southern plateau has not significantly changed since at least the mid miocene ca 15 ma arguing for an onset of the monsoon system during or before the early miocene a range of tectonic studies suggest that the northern and eastern parts of the plateau are younger geomorphological features but there are few quantitative constraints of the timing of elevation from these regions of tibet since both the elevation and the surface area of the plateau impact on atmospheric circulation palaeoaltitude studies need to be extended to chart the increasing areas of elevated land surface through time

normal faulting in central tibet since at least 13 5 myr ago tectonic models for the evolution of the tibetan plateau interpret observed east west thinning of the upper crust to be the result of either increased potential energy of elevated crust1 or geodynamic processes that may be unrelated to plateau formation2 3 4 5 6 a key piece of information needed to evaluate these models is the timing of deformation within the plateau the onset of normal faulting has been estimated to have commenced in southern tibet between about 14 myr ago7 and about 8 myr ago8 and in central tibet about 4 myr ago9 here however we report a minimum age of approximately 13 5 myr for the onset of graben formation in central tibet based on mineralization ages determined with rb sr and 40ar 39ar data that post date a major graben bounding normal fault these data along with evidence for prolonged activity of normal faulting in this and other tibetan grabens support models that relate normal faulting to processes occurring beneath the plateau thinning of the upper crust is most plausibly the result of potential energy increases resulting from spatially and temporally heterogeneous changes in thermal structure and density distribution within the crust and upper mantle beneath tibet this is supported by recent geophysical and geological data10 11 12 13 14 15 16 17 which indicate that spatial heterogeneity exists in both the tibetan crust and lithospheric mantle

growth pattern and oxygen isotopic systematics of modern freshwater mollusks along an elevation transect implications for paleoclimate reconstruction abstract fossil mollusk shells are widely distributed in the geologic records and their oxygen isotopic compositions have been used to reconstruct seasonality local climatic and elevation conditions however interpretation of isotope data from fossil shells to estimate paleoclimate and elevation is often ambiguous this study examines the oxygen isotopic systematics of modern freshwater gastropods bellamya and radix shells along an elevation climate transect in the asian monsoon region of china to improve the accuracy of paleoclimate and paleoelevation reconstruction using stable isotopes in fossil shells the results from sclerochronological analyses of the shells show that the intra shell oxygen isotopic pattern is determined by seasonal variations in lake water temperature and water isotopic composition as well as the life cycle of the organism both bellamya and radix appear to grow throughout the year in lakes where water temperature does not fall below 13 c radix in the high elevation cold habitat although prefers to grow in the warmer months can survive through the freezing temperature the 18o patterns in the shells are similar across the elevation climate transect showing high 18o values in the winter months and low 18o values in the summer months consistent with the expected pattern in asian monsoon region the average growth rates of the shells were highest at the lowest elevation site warm and humid climate but were similar at the mid to high elevation sites for large shells 2 2 cm for bellamya and 1 4 cm for radix average growth temperatures calculated using the aragonite oxygen isotope thermometer closely approximate the annual mean water temperature while their intra shell variability is a good proxy for the amplitude of seasonal variations in monthly air temperature this suggests that large shells of both bellamya and radix are excellent archives of lake environmental conditions and most suitable for paleoenvironmental studies

quaternary geomorphological evolution of the kunlun pass area and uplift of the qinghai xizang tibet plateau abstract there is a set of late cenozoic sediments in the kunlun pass area tibetan plateau china paleomagnetic esr and tl dating suggest that they date from the late pliocene to the early pleistocene analyses of stratigraphy sedimentary characteristic and evolution of the fauna and flora indicate that from the pliocene to the early quaternary about 5 1 1 ma bp there was a relatively warm and humid environment and a paleolake occurred around the kunlun pass the elevation of the kunlun pass area was no more than 1500 m and only one low topographic divide existed between the qaidam basin and the kunlun pass basin the geomorphic pattern in the kunlun pass area was influenced by the kunlun yellow river tectonic movement 1 1 0 6 ma bp the wangkun glaciation 0 7 0 5 ma is the maximum quaternary glaciation in the pass and in other areas of the plateau during the glaciation the area of the glaciers was 3 5 times larger than that of the present glacier in the pass area there was no xidatan valley that time the extreme geomorphic changes in the kunlun pass area reflect an abrupt uplift of the tibet plateau during the early and middle pleistocene this uplift of the plateau has significance on both the plateau itself and the surrounding area

seismic coda q and turbidity coefficient at the phlegraean fields volcanic area preliminary results digital recordings of microearthquake codas from shallow seismic events in the phlegraean fields region south central italy were used to calculate the attenuation factor qc