unprecedented evidence for deep convection hydrating the tropical stratosphere 1 we report on in situ and remote sensing measurements of ice particles in the tropical stratosphere found during the geophysica campaigns troccinox and scout o3 we show that the deep convective systems penetrated the stratosphere and deposited ice particles at altitudes reaching 420 k potential temperature these convective events had a hydrating effect on the lower tropical stratosphere due to evaporation of the ice particles in contrast there were no signs of convectively induced dehydration in the stratosphere

liquefaction evidence for strong earthquakes of holocene and latest pleistocene ages in the states of indiana and illinois usa abstract sand and gravel filled clastic dikes of seismic liquefaction origin occur throughout much of southern indiana and illinois nearly all of these dikes originated from prehistoric earthquakes centered in the study area in this area at least seven and probably eight strong prehistoric earthquakes have been documented as occurring during the holocene and at least one during the latest pleistocene the recognition of different earthquakes has been based mainly on timing of liquefaction in combination with the regional pattern of liquefaction effects but some have been recognized only by geotechnical testing at sites of liquefaction most paleo earthquakes presently recognized lie in indiana but equally as many may have occurred in illinois studies in illinois have not yet narrowly bracketed the age of clastic dikes at many sites which sometimes causes uncertainty in defining the causative earthquake but even in illinois the largest paleo earthquakes probably have been identified prehistoric magnitudes were probably as high as about moment magnitude m 7 5 this greatly exceeds the largest historic earthquake of m 5 5 centered in indiana or illinois the strongest paleo earthquakes struck in the vicinity of the concentration of strongest historic seismicity elsewhere paleo earthquakes on the order of m 6 7 have occurred even where there has been little or no historic seismicity both geologic and geotechnical methods of analysis have been essential for verification of seismic origin for the dikes and for back calculating prehistoric magnitudes methods developed largely as part of this study should be of great value in unraveling the paleoseismic record elsewhere

modification and preservation of environmental signals in speleothems speleothems are primarily studied in order to generate archives of climatic change and results have led to significant advances in identifying and dating major shifts in the climate system however the climatological meaning of many speleothem records cannot be interpreted unequivocally this is particularly so for more subtle shifts and shorter time periods but the use of multiple proxies and improving understanding of formation mechanisms offers a clear way forward

an integrated model of extrusive sand injectites in cohesionless sediments clastic injection and surface expression of subsurface sediment remobilization is a phenomenon which is becoming increasingly recognized however understanding of the physical mechanisms that control these features remains limited dominated by inference from outcrop and seismic studies here this limitation is addressed through a set of experiments focused on the development and evolution of fluidization features in non cohesive bedded sequences fluidization and the onset of piping are shown to occur progressively through a sequence of discrete phases with initial void formation development of infiltration horizons rupture and finally pipe formation critically the style of piping the stability of piping and the temporal evolution of venting are shown to exhibit considerable variability in particular pipes may either be stable or very mobile migrating laterally over large distances these produce deposits that are typically interpreted in outcrop as being the product of en masse liquefaction rather than localized dynamic fluidization these differing elements are synthesized to produce a model of sand extrudites in addition the implications of this model are explored

quantification of holocene asian monsoon rainfall from spatially separated cave records abstract a reconstruction of holocene rainfall is presented for southwest china an area prone to drought and flooding due to variability in the east asian monsoon the reconstruction is derived by comparing a new high resolution stalagmite 18 o record with an existing record from the same moisture transport pathway the new record is from heshang cave 30 27 n 110 25 e 294 m and shows no sign of kinetic or evaporative effects so can be reliably interpreted as a record of local rainfall composition and temperature heshang lies 600 km downwind from dongge cave which has a published high resolution 18 o record wang y j cheng h edwards r l he y q kong x g an z s wu j y kelly m j dykoski c a li x d 2005 the holocene asian monsoon links to solar changes and north atlantic climate science 308 854 857 by differencing co eval 18 o values for the two caves secondary controls on 18 o e g moisture source moisture transport non local rainfall temperature are circumvented and the resulting 18 o signal is controlled directly by the amount of rain falling between the two sites this is confirmed by comparison with rainfall data from the instrumental record which also allows a calibration of the 18 o proxy the calibrated 18 o record provides a quantitative history of rainfall in southwest china which demonstrates that rainfall was 8 higher than today during the holocene climatic optimum 6 ka but only 3 higher during the early holocene significant multi centennial variability also occurred with notable dry periods at 8 2 ka 4 8 4 1 ka 3 7 3 1 ka 1 4 1 0 ka and during the little ice age this holocene rainfall record provides a good target with which to test climate models the approach used here of combining stalagmite records from more than one location will also allow quantification of rainfall patterns for past times in other regions

experimental studies of the fluidization of layered sediments and the formation of fluid escape structures experiments demonstrate that fluid escape structures can be produced as a result of unstable fluidization behaviour where a lower base layer of granular material is inhibited from fluidizing by the presence of an overlying non fluidizing top layer before the base layer can fluidize the weight of the overlying material must be balanced and this is accomplished by base layer material pressing against the bottom surface of the confining top layer forming a static layer this static layer allows the top layer to lift away from the base layer which is then free to fluidize a water filled crack forms below the static layer and as this grows instability causes the static layer and top layer to bend and conical voids to form below the antiformal sections rupture occurs at the apex of the water void allowing the underlying water and fluidizing material to burst out through the top layer the fluidized base layer material then flows through the rupture until all of this material except that in the static layer is deposited above the previously overlying layer and a stable fluidization system results the top layer material is bent upwards around the rupture and the resulting pillar type escape structure is preserved if flow then ceases the vigour of the burst out is greatest when the base layer material has a grain size 15 of the top layer material if the base layer grain size is less than 8 of the top layer then base layer material will pass through the top layer pore spaces without forming an escape structure if cohesive material is present escape structures form when a layer of fine grained cohesive material overlies a layer of cohesionless material at low flow rates small pipes with scattered angular bends pierce the top layer and base layer material passes through them the base layer material is ejected on to the top layer and builds up around the mouth of each pipe to form constructional structures sand volcanoes this is in contrast to the cohesionless experiments where the weight of material being deposited on the top layer caused an ejecta filled depression to form around the rupture if flow then ceases both the pipes and the sand volcanoes are preserved at high flow rates where the base layer fluidizes the top cohesive layer becomes fragmented small fragments circulate within the fluidizing base layer and are preserved as floating clasts large fragments sink to the bottom of the fluidizing base layer erosion of the bottom surface of these larger fragments causes this surface to become convex downward the experimentally derived structures are similar to pillar type structures observed in the field and the processes described can be used to investigate the development of these structures fluidization experiments also demonstrate the genesis of dish structures and the cohesive behaviour can be applied to the deformation of these structures after initial formation

a three thousand year record of north atlantic climate annual band counting on three radiometrically dated stalagmites from nw scotland provides a record of growth rate variations for the last 3000 years over the period of instrumental meteorological records we have a good historical calibration with local climate mean annual temperature mean annual precipitation regional climate north atlantic oscillation and sea surface temperature sst strongest at 65 70 n 15 20 w although the correlation with the latter breaks down prior to the instrumental record this suggests that the climatic factors that force nw scottish climate and therefore our stalagmite growth varied through time and include winter nao strength the strength of the thermohaline circulation and possibly solar output spectral analysis was performed on the stalagmite growth rate time series a spectral frequency of 50 70 years is predominant in two stalagmites that were deposited from 1000 to 3000 bp a slightly longer frequency of 72 94 years is dominant from 1000 bp to present these are the same as that observed in ocean gcm output for the north atlantic region ssts our stalagmites provide high resolution precisely dated evidence of a similar periodicity predominating over the last 3000 years in a climate proxy record known to be sensitive to changes in forcing functions relevant to the north atlantic sector

transfer of climatic variables by dripwater a case study from kateřinska cave moravian karst hydrological hydrochemical properties of drip points in kate inska cave moravian karst were studied with focus on their relation to climatic variables especially rainfall and temperature the discharges of two drips marked as meteorologically sensitive drips showed statistically significant positive correlations with rainfalls with respective lags of 5 and 2 days in addition the discharges showed statistically significant positive correlations with specific electrical conductivity ph and supersaturation with respect to calcite other drips in the same cave marked as meteorologically insensitive drips did not show these correlations because the climatic conditions are identical the drip types must differ in their reaction flow paths this indicates that the paths may control some proxies possibly preserved in speleothems which should be taken into consideration for paleoenvironmental reconstructions in case of the speleothems formed by the meteorologically sensitive drips we believe that it would be possible to distinguish the intra annual climatic events via individual laminas and their composition

a coupled fluid fracture approach to propagation of clastic dikes during earthquakes abstract the propagation of clastic dikes was studied in ami az plain where hundreds of clastic dikes cross cut the soft rock of the late pleistocene lacustrine lisan formation within the seismically active dead sea basin two analytic models were established to estimate the dike propagation velocities the dike emplacement duration and the driving pressures that were associated with dike propagation either under laminar or turbulent flow conditions these models depend on the host rock and fluid properties dike width and length based on these properties and field limitations the results indicate that the dikes were propagated under turbulent flow conditions and propagation velocities of 4 65 m s the emplacement duration of the clastic dikes is between 0 8 and 2 s which is similar to the order of the acoustic wave duration that passes through the soft rock during an earthquake event this implies that the propagation of dikes could form during the passing acoustic waves and may thus be considered as an earthquake induced impact structures the calculated driving pressures that were generated during the earthquake events near the surface are 1 2 mpa one order of magnitude larger than the pressure due to the overburden on the source layer

the geometry and emplacement of conical sandstone intrusions conical sandstone intrusions with a geometry comparable with that of many igneous sills have been identified using 3d seismic data from large areas of the north sea and faeroe shetland basins these intrusions are of reservoir scale ranging from 100 to 2000 m or so in diameter 50 300 m in height and 1 80 m in thickness aperture they are concentrated in specific stratigraphic intervals in the cenozoic fills of both basins two geometrical end members are recognised and defined here apical cones and flat based bowls the former consist of inward dipping conical inclined sheets meeting at a prominent apex and the latter of similarly dipping discordant margins climbing from the edges of a concordant sheet both end members are associated with domal folds that are interpreted as resulting from the hydraulic elevation of the overburden during intrusion and which are analogous to similar structures associated with bowl shaped igneous sills measurements of aperture versus distance exhibit systematic relationships with the structural relief of these folds offering a potentially predictive method for estimation of sandstone intrusion aperture and reservoir volume prior to drilling a growth model for these end member geometries is presented drawing on existing theory for igneous sill emplacement aperture versus distance plots x are used to illustrate two contrasting models for aperture inflation during propagation but these require much further data before any specific growth model can be adopted

cyclic rapid warming on centennial scale revealed by a 2650 year stalagmite record of warm season temperature 1 a 2650 year bc665 ad1985 warm season mjja may june july august temperature reconstruction is derived from a correlation between thickness variations in annual layers of a stalagmite from shihua cave beijing china and instrumental meteorological records observations of soil co2 and drip water suggest that the temperature signal is amplified by the soil organism co2 system and recorded by the annual layer series our reconstruction reveals that centennial scale rapid warming occurred repeatedly following multicentenial cooling trends during the last millennia these results correlate with different records from the northern hemisphere indicating that the periodic alternation between cool and warm periods on a sub millennial scale had a sub hemispherical influence

an annually laminated stalagmite record of the changes in thailand monsoon rainfall over the past 387 years and its relationship to iod and enso abstract northern thailand is the most flood prone region in thailand during the indian ocean dipole iod and el nino southern oscillation enso events an annual growth rate profile covering the period from 1622 to 2008 ad was derived from the laminated stalagmite nj 0901 from this area by comparing stalagmite nj 0901 to a contemporaneous stalagmite from the same cave and correlating the growth rate of nj 0901 with meteorological data from the most recent 100 years the stalagmite record proved to be a paleoclimate proxy of thailand monsoon tm rainfall this is the first annually laminated speleothem record that has been traced back four centuries this record provided a long term perspective and a valuable insight into tm rainfall and allowed us to investigate variations in the monsoon activity that was associated with iod and enso our results indicate that both iod and enso are significant climate modes that impact tm rainfall but the effect of the interaction iod and enso on tm rainfall remains unclear

estimates of sea surface temperature in the coral sea at the last glacial maximum the climap 1981 reconstruction of the coral sea found relatively little cooling 2 c in the low latitudes 10 s but a warming off australia at about 25 s the small low latitude changes are of interest because terrestrial pollen and snowline data from the new guinea highlands imply that surface temperatures may have been 6 to 9 c colder at the last glacial maximum lgm the purpose of this paper is to evaluate these conclusions on the basis of additional core sites new oxygen isotope stratigraphy and new sea surface temperature sst estimates using the modern analog technique mat in the northern coral sea planktonic foraminifer assemblages consist of tropical subtropical species that show little change over the past 20 kyr quantitative estimates of sst using the modern analog technique mat confirm the climap 1981 conclusion that little or no temperature change occurred in this tropical region at the lgm thus reinforcing the conflict with terrestrial evidence in the southern region 25 s two cores indicate that foraminifer faunas became more subtropical at the lgm the mat estimates for the lgm are 3 to 4 c colder than modern producing a steeper thermal gradient in the southern coral sea these data remove the warm sst anomaly along the eastern coast of australia and indicate that during the lgm cool high latitude waters were displaced northward along the coast of australia into the southern coral sea

lake kumphawapi revisited the complex climatic and environmental record of a tropical wetland in ne thailand kumphawapi which is thailand s largest natural freshwater lake contains a 10 000 year long climatic and environmental archive new data sets stratigraphy chronology hydrogen isotopes plant macrofossil and charcoal records for two sedimentary sequences are here combined with earlier multi proxy studies to provide a comprehensive reconstruction of past climatic and environmental changes for northeast thailand gradually higher moisture availability due to a strengthening of the summer monsoon led to the formation of a large shallow lake in the kumphawapi basin between 10 700 and c 7000 cal bp the marked increase in moisture availability and lower evaporation between c 7000 and 6400 cal bp favoured the growth and expansion of vegetation in and around the shallow lake the increase in biomass led to gradual overgrowing and infilling to an apparent lake level lowering and to the development of a wetland multiple hiatuses are apparent in all investigated sequences between c 6500 and 1400 cal b

the influence of microbial mats on the formation of sand volcanoes and mounds in the red sea coastal plain south jeddah saudi arabia abstract extensive areas covered by microbial mats have been found in the upper intertidal flats and supratidal pools in the red sea coastal plain of south jeddah saudi arabia numerous microbially controlled sediment surface morphologies are evident such as flat cohesive mats that commonly pass into mats with wrinkles reticulates and tufts together with erosion pockets and mat chips these microbial mats form cohesive surface layers that lead to biostabilization of the sediment surface fluidization of the underlying sediments is due to tidal influences and pressurized gas escape from decay and photosynthesis of microbial mats and causes deformation and rupture of the cohesive surface mat layer via vertical and sub vertical pipes extrusion of fluidized sediments and water through these pipes leads to redeposition of sediment grains above the surface mat layer to form sand volcanoes and mounds most of the sand volcanoes present in the intertidal flats and supratidal pools show a symmetrical morphology whereas in tidal channels asymmetrical forms are more common extrusion of underlying sediments through several adjacent vents leads to coalescence of sand volcanoes to form sand mounds in this study sand volcanoes are also compared with other cone like features from the red sea such as gas domes and crab mounds this comparison should help in differentiating similar cone like features associated with microbial mats in the rock record

on steady homogeneous sand water flows in a vertical conduit in this paper an idealized model of the steady state phase of the flow in a vertical conduit leading to a sand volcano eruption is developed from first principles the model assumes that a sand water mixture flows upwards driven by an overpressure at the base of a vertical cylindrical conduit or a two dimensional fracture and opposed by gravity viscous resistance and turbulent drag the conditions for flow are analysed in detail and the mechanisms controlling the eruption rates are studied quantitatively the flow predictions are in accordance with our observations of analogous vigorous sand eruptions at deepwater oil fields for sufficiently high flow velocities u 10ut and small sand fractions s 0 2 the flow may be well mixed and homogeneous if these conditions are not met the flow may either become two phase or does not develop combining geological considerations with the steady homogeneous model it is possible to predict the behaviour of the vigorous quasi steady stage of a sand volcano eruption it is shown that based on the average density of the overlying sediments there are a range of overpressures for which sand volcanoes may develop

a dry episode during the younger dryas and centennial scale weak monsoon events during the early holocene a high resolution stalagmite record from southeast of the loess plateau china 1 a high resolution stalagmite oxygen isotope record from dongshiya cave located southeast of the chinese loess plateau reveals detailed climatic oscillations between 12 7 and 9 0 ka bp on centennial and decadal timescales with a temporal resolution of 1 to 20 years the early younger dryas is characterized by a gradual increase in 18o values which is followed by a depositional hiatus for the remainder of the younger dryas between 12 1 and 11 5 ka bp implying a weak east asian monsoon or a dry climate during the younger dryas eight weak monsoon events between 11 5 and 9 0 ka bp punctuate the early holocene east asian monsoon and are likely tied to cold events in greenland including the pre boreal oscillation and the 9 2 ky event the spectral analysis of the dongshiya 18o time series yields peaks at frequencies that have been linked to solar frequencies indicating that solar changes may be at least partially responsible for changes in the intensity of the east asian monsoon during the early holocene

regional sand injectite architecture as a record of pore pressure evolution and sand redistribution in the shallow crust insights from the panoche giant injection complex california abstract observations on outcrop of a regionally developed sand injectite are used to infer and estimate the pore pressure conditions in the shallow crust that caused the fluidization and injection of tens of cubic kilometres of sand the estimated pore fluid pressures at the base of the injection complex at 1500 m burial depth below a regionally developed shale dominated seal are from 22 26 to 25 08 mpa which respectively correspond to 0 81 and 0 95 lithostatic pressure a theoretical basis for prediction of sand injection is defined and applied to the prediction of pore pressure at the time of sand injection the depth at which seal failure occurred and the density and granular content of the fluidized flow lateral variations in the style and abundance of sandstone intrusions are described and these all fit into a remarkably uniform tripartite division of parent units an intrusive complex and an extrusive complex a sill zone intrusions are dominated by sills occurs in a restricted stratigraphic interval 200 270 m thick location of the base of the sill zone is directly related to the thickness of the overburden and an isobaric surface at the time of sand injection the lithostatic equilibrium surface is defined at the base of the sill zone when the sills formed an extended period of supra lithostatic pressure occurred within the sill zone

world s largest extrusive body of sand using three dimensional seismic and well data from the northern north sea we describe a large 10 km 3 body of sand and interpret it as extrusive to our knowledge this is the world9s largest such sandbody it would bury manhattan new york 60 km 2 under 160 m of sand or the whole of london uk 1579 km 2 under 6 m of sand this sand vented to the seafloor when it was more than 500 m deep during the pleistocene glacial period the sandbody 1 covers an area of more than 260 km 2 2 is up to 125 m thick 3 fills low areas around mounds which formed when underlying sand injectites lifted the overburden 4 wedges out away from a central thick zone 5 is locally absent along irregular ditches 20 km long and up to 50 m deep which overlie feeders on the flanks of the mounds and 6 consists of fine grained to medium grained sub rounded to rounded grains we compare the distribution of the sand with the results of scaled physical experiments in our interpretation high fluid pressure fractured the regional hordaland group seal in the study area so that fluidized sand moved rapidly to the seafloor through fissures on the flanks of underlying mounds mixed with seawater and formed lateral gravity currents these transported the sand as much as 8 km away from the blow out fissures and formed extruded sand sheets large extrusive sands represent a new type of economically interesting reservoir

influence of the state of the indian ocean dipole on the following year s el nino el nino southern oscillation enso consists of irregular episodes of warm el nino and cold la nina conditions in the tropical pacific ocean 1 with significant global socio economic and environmental impacts 1 nevertheless forecasting enso at lead times longer than a few months remains a challenge 2 3 like the pacific ocean the indian ocean also shows interannual climate fluctuations which are known as the indian ocean dipole 4 5 positive phases of the indian ocean dipole tend to co occur with el nino and negative phases with la nina 6 9 here we show using a simple forecast model that in addition to this link a negative phase of the indian ocean dipole anomaly is an efficient predictor of el nino 14 months before its peak and similarly a positive phase in the indian ocean dipole often precedes la nina observations and model analyses suggest that the indian ocean dipole modulates the strength of the walker circulation in autumn the quick demise of the indian ocean dipole anomaly in november december then induces a sudden collapse of anomalous zonal winds over the pacific ocean which leads to the development of el nino la nina our study suggests that improvements in the observing system in the indian ocean region and better simulations of its interannual climate variability will benefit enso forecasts

cave air and hydrological controls on prior calcite precipitation and stalagmite growth rates implications for palaeoclimate reconstructions using speleothems abstract hourly resolved cave air p co 2 and cave drip water hydrochemical data illustrate that calcite deposition on stalagmites can be modulated by prior calcite precipitation pcp on extremely short timescales a very clear second order covariation between cave air p co 2 and drip water ca 2 concentrations during the winter months demonstrates the effects of degassing induced pcp on drip water chemistry estimating the strength of the cave air p co 2 control on pcp is possible because the pcp signal is so clear at our drip site a one ppm shift in ca 2 concentrations requires a p co 2 shift of between 333 and 667 ppm this value will undoubtedly vary from site to site depending on drip water flow rate residence time drip water cave air p co 2 differential and availability of low p co 2 void spaces in the vadose zone above the cave high resolution cave environmental measurements were used to model calcite deposition on one stalagmite in crag cave sw ireland and modelled growth over the study period 222 m over 171 days is extremely similar to the amount of actual calcite growth 240 m over the same time interval strongly suggesting that equations used to estimate stalagmite growth rates are valid although cave air p co 2 appears to control drip water hydrochemistry in the winter drip water dilution caused by rain events may have played a larger role during the summer as evidenced by a series of sudden drops in ca 2 concentrations dilution followed by much more gradual increases in drip water ca 2 concentrations slow addition of diffuse water this research demonstrates that pcp on stalactites cave ceilings and void spaces within the karst above the cave partially controls drip water chemistry and that thorough characterisation of this process at individual caves is necessary to most accurately interpret climate records from those sites

mechanisms and controls on the formation of sand intrusions sandstone intrusions are found in all sedimentary environments but have been reported most commonly from deep water settings they also appear to be more frequently developed in tectonically active settings where applied tectonic stresses facilitate development of high fluid pressures within the sediments a variety of mechanisms have been cited as triggers for clastic intrusions these include seismicity induced liquefaction application of tectonic stresses excess pore fluid pressures generated by deposition related processes and the influx of an overpressured fluid from deeper within the basin into a shallow sand body the formation of sandstone dykes and sills is investigated here by considering them as natural hydraulic fractures when the seal on an unconsolidated overpressured sand body fails the resulting steep hydraulic gradient may cause the sand to fluidize the fluidized slurry can then inject along pre existing or new fractures to form clastic intrusions the scale and the geometry of an intrusive complex is governed by the stress state depth and pre existing joints or faults within the sedimentary succession as well as the nature of the host sediments for the simplest tectonic setting where the maximum stress in a basin is vertical gravitational loading small irregular intrusions commonly result in the formation of sills at shallow depths within a few metres of the surface whereas at greater depth dykes and sills forming clastic intrusion networks are more typical a simple relationship is derived to calculate the maximum burial depth at which a dyke sill complex forms as a function of the source bed to sill height the bulk density of the surrounding sediments and the ratio of the vertical to horizontal effective stresses k 0 when applied to three examples of large scale dyke sill complexes developed within paleocene and eocene deep water reservoir sand bodies of the north sea maximum burial depths in a range of 375 to c 500 m 450 700 m and 550 850 m are estimated for intrusion of each of the three complexes

very high frequency and seasonal cave atmosphere pco2 variability implications for stalagmite growth and oxygen isotope based paleoclimate records abstract cave air p co 2 at two irish sites varied dramatically on daily to seasonal timescales potentially affecting the timing of calcite deposition and consequently climate proxy records derived from stalagmites collected at the same sites temperature dependent biochemical processes in the soil control co 2 production resulting in high summer p co 2 values and low winter values at both sites large large amplitude high frequency variations superimposed on this seasonal cycle reflect cave air circulation here we model stalagmite growth rates which are controlled partly by co 2 degassing rates from drip water by considering both the seasonal and high frequency cave air p co 2 variations modeled hourly growth rates for stalagmite cc bil from crag cave in sw ireland reach maxima in late december 0 063 m h 1 and minima in late june early july 0 033 m h 1 for well mixed diffuse flow cave drips such as those that feed cc bil high summer cave air p co 2 depresses summer calcite deposition while low winter p co 2 promotes degassing and enhances deposition rates in stalagmites fed by well mixed drips lacking seasonal variations in 18 o integrated annual stalagmite calcite 18 o is unaffected however seasonality in cave air p co 2 may influence non conservative geochemical climate proxies e g 13 c sr ca stalagmites fed by seasonal drips whose hydrochemical properties vary in response to seasonality may have higher growth rates in summer because soil air p co 2 may increase relative to cave air p co 2 due to higher soil temperatures this in turn may bias stalagmite calcite 18 o records towards isotopically heavier summer drip water 18 o values resulting in elevated calcite 18 o values compared to the equilibrium values predicted by calcite water isotope fractionation equations interpretations of stalagmite based paleoclimate proxies should therefore consider the consequences of cave air p co 2 variability and the resulting intra annual variability in calcite deposition rates

seasonal trace element and stable isotope variations in a chinese speleothem the potential for high resolution paleomonsoon reconstruction abstract we report the presence of clear annual cycles in trace element mg ca sr ca ba ca and u ca and stable isotope 18o and 13c composition in an annually banded stalagmite from heshang cave hubei province china 30 44 n 110 42 e through a combination of micromilling and in situ analysis la mc icpms we measured geochemical variations across 16 annual growth bands to assess their potential as seasonal resolution paleomonsoon proxies to facilitate comparison with modern climatic and environmental data we created composite annual cycles for each proxy by stacking 6 well defined years speleothem 18o variations 10 8 to 8 5 are controlled by seasonal variations in temperature and drip water 18o which lead to maximum values during may around the time of summer monsoon onset this provides a chronological marker which can be used to constrain the timing of the other geochemical cycles the composite cycles reveal a strong positive correlation between mg ca sr ca ba ca and 13c values in the micromilled section r2 0 65 0 98 with minimum values occurring around may maximum u ca values occur at the same time we present simple models which show that these correlations as well as the observed ranges of mg ca 14 1 to 22 4 mmol mol sr ca 0 2 to 0 4 mmol mol and 13c 12 5 to 10 7 may be fully explained by progressive co2 degassing and calcite precipitation from an initially saturated solution using realistic initial conditions for heshang cave t 18 c mg casolution 0 84 mol mol sr casolution 0 69 mmol mol 13ctdic 16 75 we find that the observed relationships can be produced by using dmg 0 016 and dsr 0 30 within the range of expected values the model suggests that the fraction of ca removed from the solution ranges from 0 to 30 to produce the observed seasonal cycles this variation may be due to two related processes which occur during drier periods 1 increased prior precipitation of calcite in the epikarst or on the cave ceiling and or 2 a greater degree of co2 degassing and calcite precipitation on stalagmite surfaces when drip rates are lower both mechanisms would have the effect of enriching speleothem mg ca sr ca ba ca and 13c values during drier periods past variations in heshang carbonate chemistry may therefore be useful as seasonal resolution proxies for past rainfall

a synthesis of abrupt changes in the asian summer monsoon since the last deglaciation we have compiled 36 previously published palaeoclimate records to determine the timing and spatial pattern of century scale abrupt changes in asian monsoon precipitation since the last deglaciation we identify abrupt events from 1 the interpretations of the authors of these records and 2 the more objective moving t test calculation our results indicate that abrupt climatic changes occurred at 11 5 cal ka 4 5 5 0 cal ka and ad 1300 at the start of the holocene 11 5 cal ka asian monsoon precipitation increased dramatically this climatic change is synchronous with an abrupt warming in the north atlantic during the middle holocene there was a time of preferred and widespread weakening in monsoon strength 4 5 5 0 cal ka this result contradicts previous notions of either a gradual trend towards drier conditions or a series of abrupt events that occurred in an unorganized fashion across space and time the middle holocene abrupt event could have been synchronous with an abrupt cooling event in the north atlantic as well as a warming and intensie cation of internannual variability in the tropical pacie c in contrast to previous periods precipitation changes at ad 1300 have a heterogeneous spatial pattern we e nd no conclusive evidence for a change in the asian monsoon at 8 2 cal ka as suggested by several previous studies more high resolution data may be needed to observe this short lived event overall our results attest to the potential for rapid and major shifts in asian monsoon precipitation that may be triggered by variations in other components of the climatic system

clastic dike swarms and the structural evolution of the foreland fold and thrust belt of the southern andes clastic dike swarms are intruded into a cenozoic foreland fold and thrust belt in southern chile the dike material consists of sandstone and conglomerate with clasts as much as 25 cm in diameter brecciated wall rocks are also found in the clastic matrix the dikes often exceed 50 cm in width and hundred of metres in length in outcrop and are oriented overwhelmingly transverse to fold axes and parallel to cross joints the dike swarms are concentrated near the toe of major thrusts where they are found injected into the hanging wall a regional axial planar spaced cleavage is developed in the clastic dikes and sills clearly postdating injection of clastic material dike injection postdates at least the initiation of extension fractures the cross joint set within the swarms the dike intrusions represent as much as 20 extension parallel to fold axes in addition to several percent extension represented regionally by the cross joints the structural features of the dike swarms and their geometric relationship to other structures suggest rapid single phase injection the arrival of the front edge of a thrust on an already highly overpressured sedimentary sequence would cause an instantaneous increase in the overburden pressure and therefore could result in injection of a dense slurry of wet coarse sediments along preexisting planes of weakness field relationships of mesoscopic structures suggest the following evolution cross joint development incipient cleavage development initiation of thrusting and buckling clastic dike injection regional spaced cleavage development and associated late stage tightening of folds

geometry and tectonic significance of albian sedimentary dykes in the sisteron area se france abstract sedimentary dykes in the sisteron area have penetrated pre existing fracture sets in late aptian and early albian strata dynamic characteristics of such fractures are revealed by the bifurcation and the branching of dykes three dimensional statistical analysis of the initial orientation of two vertical conjugate sets of dykes indicates their mechanics of formation as well as the principal compressional stress direction during the development of the sill dyke regime in the sisteron area another set of sandstone dykes present in the area suggests syn sedimentary and extensional faulting tectonic activity before the area became involved in compressional tectonics several significant dyke forms clearly show the sense of shear along fractures filled with sand and enable the stress pattern during dyke formation in the area to be recognized

state of the antarctic and southern ocean climate system this paper reviews developments in our understanding of the state of the antarctic and southern ocean climate and its relation to the global climate system over the last few millennia climate over this and earlier periods has not been stable as evidenced by the occurrence of abrupt changes in atmospheric circulation and temperature recorded in antarctic ice core proxies for past climate two of the most prominent abrupt climate change events are characterized by intensification of the circumpolar westerlies also known as the southern annular mode between 6000 and 5000 years ago and since 1200 1000 years ago following the last of these is a period of major trans antarctic reorganization of atmospheric circulation and temperature between ad1700 and 1850 the two earlier antarctic abrupt climate change events appear linked to but predate by several centuries even more abrupt climate change in the north atlantic and the end of the more recent event is coincident with reorganization of atmospheric circulation in the north pacific improved understanding of such events and of the associations between abrupt climate change events recorded in both hemispheres is critical to predicting the impact and timing of future abrupt climate change events potentially forced by anthropogenic changes in greenhouse gases and aerosols special attention is given to the climate of the past 200 years which was recorded by a network of recently available shallow firn cores and to that of the past 50 years which was monitored by the continuous instrumental record significant regional climate changes have taken place in the antarctic during the past 50 years atmospheric temperatures have increased markedly over the antarctic peninsula linked to nearby ocean warming and intensification of the circumpolar westerlies glaciers are retreating on the peninsula in patagonia on the sub antarctic islands and in west antarctica adjacent to the peninsula the penetration of marine air masses has become more pronounced over parts of west antarctica above the surface the antarctic troposphere has warmed during winter while the stratosphere has cooled year round the upper kilometer of the circumpolar southern ocean has warmed antarctic bottom water across a wide sector off east antarctica has freshened and the densest bottom water in the weddell sea has warmed in contrast to these regional climate changes over most of antarctica near surface temperature and snowfall have not increased significantly during at least the past 50 years and proxy data suggest that the atmospheric circulation over the interior has remained in a similar state for at least the past 200 years furthermore the total sea ice cover around antarctica has exhibited no significant overall change since reliable satellite monitoring began in the late 1970s despite large but compensating regional changes the inhomogeneity of antarctic climate in space and time implies that recent antarctic climate changes are due on the one hand to a combination of strong multi decadal variability and anthropogenic effects and as demonstrated by the paleoclimate record on the other hand to multi decadal to millennial scale and longer natural variability forced through changes in orbital insolation greenhouse gases solar variability ice dynamics and aerosols model projections suggest that over the 21st century the antarctic interior will warm by 3 4 1oc and sea ice extent will decrease by 30 ice sheet models are not yet adequate enough to answer pressing questions about the effect of projected warming on mass balance and sea level considering the potentially major impacts of a warming climate on antarctica vigorous efforts are needed to better understand all aspects of the highly coupled antarctic climate system as well as its influence on the earth s climate and oceans

quantitative interpretation of fossil pollen spectra dissimilarity coefficients and the method of modern analogs abstract dissimilarity coefficients measure the difference between multivariate samples and provide a quantitative aid to the identification of modern analogs for fossil pollen samples how eight coefficients responded to differences among modern pollen samples from eastern north america was tested these coefficients represent three different classes 1 unweighted coefficients that are most strongly influenced by large valued pollen types 2 equal weight coefficients that weight all pollen types equally but can be too sensitive to variations among rare types and 3 signal0to noise coefficients that are intermediate in their weighting of pollen types the studies with modern pollen allowed definition of critical values for each coefficient which when not exceeded indicate that two pollen samples originate from the same vegetation region dissimilarity coefficients were used to compare modern and fossil pollen samples and modern samples so similar to fossil samples were found that most of three late quaternary pollen diagrams could be reconstructed by substituting modern samples for fossil samples when the coefficients indicated that the fossil spectra had no modern analogs then the reconstructed diagrams did not match all aspects of the originals no modern analogs existed for samples from before 9300 yr b p at kirchner marsh minnesota and from before 11 000 yr b p at wintergreen lake michigan but modern analogs existed for almost all holocene samples from these two sites and brandreth bog new york

non linearities in drip water hydrology an example from stump cross caverns yorkshire drip rate data have been collected at 15 min intervals at six locations in stump cross caverns n england since 1998 the different drip sites cover a wide range of drip rates from 2 drips s to 2 drips h and in general the variability of drip rate increases with mean drip rate in our continuous data sampling we observe rapid discharge increases which appear to be synchronous between drips sites and which can be explained by flow switching of the water overlying the cave during times of high infiltration rate such as intense rain storms or rapid snowmelt a test for non linearity white test in the drip series provides very strong evidence that many of the drip sequences are non linear we conclude that at our drip sites there is a non linear input weather and non linearities within the karst system leading to non linear dripping which is independent of drip rate our results have implications for stalagmite palaeoclimatology where such widespread non linearities have not been taken account of

velocities and driving pressures of clay rich sediments injected into clastic dykes during earthquakes summary we studied the velocities and driving pressures associated with clastic dyke formation in the ami az plain where hundreds of clastic dykes cross cut the soft rock of the late pleistocene lacustrine lisan formation within the seismically active dead sea basin flow of clastic material into fractures and opening of the fractures are two mechanisms that occur during earthquake induced clastic dyke emplacement two analytic models were established based on field observations and experimental viscosity tests to estimate the velocities and driving pressures that were associated with dyke emplacement a a channel flow for upward injection of a clay water mixture and b a profile of fracture dilation based on the elastic theory analysis the two models predict that pressures between 1 and 10 mpa are generated in the source layer and dykes in the last stage of the injection process in addition the channel flow model predicts that the injection velocity reaches metres to tens of metres per second and the emplacement time of the clastic dykes is on a scale of seconds it is suggested that the high pressure values represent the static stress drop during earthquake events or represent dynamic stresses resulting from the seismic waves which passed through the soft lacustrine rocks in both cases the predicted high pressure values indicate that the clastic dyke was emplaced in close proximity of an active segment of the dead sea fault during the late pleistocene holocene

terrestrial conditions at the last glacial maximum and climap sea surface temperature estimates are they consistent climap 1981 seasonal reconstruction of the earth s surface at the last glacial maximum geological society of america map and chart series mc 36 boundary conditions were used as inputs to the giss general circulation model and the last glacial maximum lgm climate was simulated for six model years the simulation was compared with snow line depression and pollen inferred temperature data at low latitudes specifically for hawaii colombia east africa and new guinea the model does not produced as much cooling at low latitudes as is implied by the terrestrial evidence an alternative experiment in which the climap sea surface temperatures were uniformly lowered by 2 c produces a better fit to the land data although in hawaii model temperatures are still too warm the relatively warm climap tropical sea surface temperatures also provide for only a slight decrease in the hydrologic cycle in the model in contrast to both evidence of lgm tropical aridity and the results of the experiment with colder ocean temperatures with the climap sea surface temperatures the lgm global annual mean surface air temperature is 3 6 c colder than at present if the ocean temperatures were allowed to cool in conformity with the model s radiation balance the lgm simulation would be 5 6 c colder than today and in better agreement with the tropical land evidence

applications of stalagmite laminae to paleoclimate reconstructions comparison with dendrochronology climatology abstract laminated stalagmites observed in either ultra violet or visible light or recognized via trace elements are now widely recognized as a common deposition form annually laminated stalagmites should be expected in caves which have an overlying climate that has a strong seasonality similar climate zones to where trees grow with distinct annual rings continuous laminated stalagmite chronologies up to several thousand years should be expected where some mixing of stored water occurs such stalagmites can be used to reconstruct climate particularly through variations in lamina width such climate records would be relatively damped by mixing of event water with stored groundwater constraining the amount of high frequency climate signals contained in the stalagmite but relatively long continuous lamina sequences permit the preservation of low frequency centennial scale climate signals this contrasts with numerous tree ring climate records which are frequently limited in preserving multi centennial trends due to the necessary removal of age related noise from relatively short tree segments laminated stalagmites and tree rings should therefore to some degree provide complementary climate information appropriate methods for compiling stalagmite layer chronologies and climatologies are presented

a new phenomenon in ancient liquefaction the draw in process its final stage abstract the authors propose a draw in phenomenon which occurs at the final stage of liquefaction three case studies of ancient liquefaction accompanied with draw in phenomena are examined from the karasu river district gunmna prefecture and the sanbusho and motoyashiki archeological sites niigata prefecture central japan the intrusion spout phenomenon is the primary or the main process of liquefaction caused by the increase in pressure of the liquefied layer during the earthquake the draw in phenomenon is the secondary or final process of liquefaction which occurs just after the earthquake the draw in structure is important to recognize in the field because only the final form of ancient liquefaction is preserved during the draw in stage the ancient surface soils are mixed and drawn in therefore the draw in structure is useful in order to estimate the age of ancient liquefaction events

use of liquefaction induced features for paleoseismic analysis an overview of how seismic liquefaction features can be distinguished from other features and how their regional distribution and properties of source sediment can be used to infer the location and strength of holocene paleo earthquakes abstract liquefaction features can be used in many field settings to estimate the recurrence interval and magnitude of strong earthquakes through much of the holocene these features include dikes craters vented sand sills and laterally spreading landslides the relatively high seismic shaking level required for their formation makes them particularly valuable as records of strong paleo earthquakes this state of the art summary for using liquefaction induced features for paleoseismic interpretation and analysis takes into account both geological and geotechnical engineering perspectives the driving mechanism for formation of the features is primarily the increased pore water pressure associated with liquefaction of sand rich sediment the role of this mechanism is often supplemented greatly by the direct action of seismic shaking at the ground surface which strains and breaks the clay rich cap that lies immediately above the sediment that liquefied discussed in the text are the processes involved in formation of the features as well as their morphology and characteristics in field settings whether liquefaction occurs is controlled mainly by sediment grain size sediment packing depth to the water table and strength and duration of seismic shaking formation of recognizable features in the field generally requires a low permeability cap above the sediment that liquefied field manifestations are controlled largely by the severity of liquefaction and the thickness and properties of the low permeability cap criteria are presented for determining whether observed sediment deformation in the field originated by seismically induced liquefaction these criteria have been developed mainly by observing historic effects of liquefaction in varied field settings the most important criterion is that a seismic liquefaction origin requires widespread regional development of features around a core area where the effects are most severe in addition the features must have a morphology that is consistent with a very sudden application of a large hydraulic force this article discusses case studies in widely separated and different geological settings coastal south carolina the new madrid seismic zone the wabash valley seismic zone and coastal washington state these studies encompass most of the range of settings and the types of liquefaction induced features likely to be encountered anywhere the case studies describe the observed features and the logic for assigning a seismic liquefaction origin to them also discussed are some types of sediment deformations that can be misinterpreted as having a seismic origin two independent methods for estimating prehistoric magnitude are discussed briefly one method is based on determination of the maximum distance from the epicenter over which liquefaction induced effects have formed the other method is based on use of geotechnical engineering techniques at sites of marginal liquefaction in order to bracket the peak accelerations as a function of epicentral distance these accelerations can then be compared with predictions from seismological models

on the weakening relationship between the indian monsoon and enso analysis of the 140 year historical record suggests that the inverse relationship between the el nino southern oscillation enso and the indian summer monsoon weak monsoon arising from warm enso event has broken down in recent decades two possible reasons emerge from the analyses a southeastward shift in the walker circulation anomalies associated with enso events may lead to a reduced subsidence over the indian region thus favoring normal monsoon conditions additionally increased surface temperatures over eurasia in winter and spring which are a part of the midlatitude continental warming trend may favor the enhanced land ocean thermal gradient conducive to a strong monsoon these observations raise the possibility that the eurasian warming in recent decades helps to sustain the monsoon rainfall at a normal level despite strong enso events