stream driven high density gravelly traction carpets possible deposits in the trabeg conglomerate formation sw ireland and some theoretical considerations of their origin within high density flood flows a prominent mechanism of gravel transport and deposition is by stream driven high density traction carpet with a rheology similar to grain flow these gravel carpets are envisaged to form the basal portion of a bipartite high density flood flow decoupled from an overlying sand and silt laden turbulent flow several examples already documented in the literature are reviewed and an additional case from the lower old red sandstone of southwest ireland is presented two mechanisms of traction carpet initiation are discussed by rapid entrainment of gravel into suspension on rising stage followed by settling into the gravel traction carpet at peak and falling stage and by overconcentration of a normal low density bedload gravel entrainment suspension and traction carpet development are significantly easier if the flood water already carries a high concentration of sand and silt in suspension theoretical consideration further shows that gravelly traction carpets can be maintained in channels of relatively low gradient by the shear stress exerted by the high density sand bearing turbulent flood flow above this tangential shear stress is converted to dispersive pressure which aids buoyancy and quasi static grain to grain contacts in the support of the clasts within the gravel carpet the carpet is thought to have a quasi plastic rheology but behave much like a viscous fluid at high shear rates stream driven gravelly traction carpets are expected to produce sheet like units of clast to matrix supported conglomerate characterized by a parallel or an a p a i clast fabric these units may be ungraded normally or inversely graded depending on the rate of shear the viscosity of the flow and the celerity of deposition

climate changes reconstructed from a glacial lake in high central asia over the past two millennia abstract climatic changes in arid central asia aca over the past two millennia have been widely concerned however less attention has been paid to those in the high central asia hca where the asian water tower nurtures the numerous oases by glacier and or snow melt here we present a new reconstruction of the temperature and precipitation change over the past two millennia based on grain size of a well dated glacial lake sediment core in the central of southern tianshan mountains the results show that the glacial lake catchment has experienced cold wet climate conditions during the dark age cold period 300 600 ad dacp and the little ice age 1300 1870 ad lia whereas warm dry conditions during the medieval warm period 700 1270 ad mwp integration of our results with those of previously published lake sediment records stalagmite 18o records ice core net accumulation rates tree ring based temperature reconstructions and mountain glacier activities suggest that there has a broadly similar hydroclimatic pattern over the hca areas on centennial time scale during the past two millennia comparison between hydroclimatic pattern of the hca and that of the aca areas suggests a prevailing warm dry and cold wet hydroclimatic pattern over the whole westerlies dominated central asia areas during the past two millennia we argue that the position and intensity of the westerlies which are closely related to the phase of the north atlantic oscillation nao and the strength of the siberian high pressure sh could have jointly modulated the late holocene central asia hydroclimatic changes

holocene optimum events inferred from subglacial sediments at tschierva glacier eastern swiss alps abstract this study investigates the subglacial sedimentary archive at tschierva glacier eastern swiss alps subfossil wood remains found at the retreating glacier tongue indicate that their emergence results from recent transport from an upvalley basin a confluence basin like structure was found to exist by georadar measurements underneath the present glacier in combination with high resolution age determinations based on dendrochronology and radiocarbon dating it is implied that a retreated tschierva glacier allowed vegetation growth and sediment accumulation in that basin three periods of glacier recession were detected which occurred around 9200 cal yr bp from 7450 to 6650 cal yr bp and from 6200 to 5650 cal yr bp these periods are called holocene optimum events hoe accordingly an equilibrium line rise 220 m compared to the reference period from 1960 to 1985 was inferred from digital elevation models of former glacier extents since glacier mass balance depends on summer june july august temperature and precipitation an equilibrium line altitude ela rise of 220 m implies a summer temperature increase of about 1 8 c assuming unchanged precipitation during the dated hoe alternative calculations point to probable temperature increase in a broad interval between 1 0 c taking into account a precipitation change of 250 mm a to 2 5 c with 250 mm a precipitation change supporting earlier paleotemperature estimates it is proposed that higher mean summer insolation caused a stronger seasonality during the mid holocene as compared to late holocene conditions

application of rate and state friction formalism and flash melting to thin permanent slip zones of major faults strain within certain major exhumed fault zones concentrated within a 1 mm wide permanent slip zone a surrounding 10 mm thick fault core is strongly damaged concentration of seismic strain rate within a very thin zone is expected both for rate and state friction and weakening of the slip zone by flash melting at real contacts in both cases the material at the rupture tip begins with a strength that is far above that for steady state sliding the permanent slip zone is slightly weaker than its surroundings and begins to slip with a strain rate faster than the surrounding core damage from strain thus weakens the sliding zone more than the fault core further concentrating strain rate toward a minimum thickness that depends on the finite size of grains flash heating involves a weakening velocity that is the product of a material property the weakening strain rate and the slip zone thickness there is a minimum strength associated with a sliding velocity 15 m s 1 where stresses at the crack tip just exceed the elastic limit higher sliding velocities imply large inelastic strains near the rupture tip that would add to macroscopic friction lower sliding velocities imply higher coefficients of friction as flash weakening is velocity weakening the width of the psz should organize to a finite value so its weakening velocity is that needed to give the sliding velocity for minimum strength

glacier fluctuations equilibrium line altitudes and palaeoclimate in lyngen northern norway during the lateglacial and holocene based on lacustrine and morpho stratigraphical evidence from lyngen in troms northern norway 13 marginal moraines have been mapped in front of lenangsbreene in strupskardet moraines m1 m13 are inferred to represent glacier halts or advance readvance taking place during the lateglacial and holocene the presence of collapse depressions suggests that some of them were ice cored m1 m3 a chronological framework taking into account a combination of former shorelines and related glacier meltwater channels lichenometry and ams radiocarbon dated lacustrine sediments spanning the last 20 000 cal yr bp has been established the distal glacier fed lake aspvatnet was isolated from the sea c 10 300 cal yr bp and the lacustrine sediments have been investigated by use of loss on ignition loi magnetic susceptibility water content wet and dry bulk density dbd and the magnetic parameters anhysteretic remanent magnetization arm and saturation remanent magnetization sirm there is in general good agr

the effects of lithology and base level on topography in the northern alpine foreland abstract the evolution of topography is driven by climate and tectonics and strongly influenced by substrate properties and different base levels the contributions of these factors may vary in space and time and are thus difficult to disentangle our study area the hausruck kobernauserwald range has a rather uniform climatic and tectonic history but is drained by rivers with different base levels and consists of contrasting sedimentary rocks mainly due to different sedimentation environments this makes them an ideal location to study the effects of lithology and base level on topography to decipher the roles of these influences we used a high resolution digital elevation model and performed a series of morphometric analyses longitudinal river profiles indicate that all channels in the study area independent from base level bed rock and overall morphological expression are well graded hypsometry shows no evidence for base level effects on the present topography while variations in the hypsometric curves coincide with lithological differences this is also reflected in contrasts of mean elevation and slope distributions lithology dependent variations in channel concavity and catchment wide hypsometric integrals show that lithology controls both channel incision and hillslope processes in the study area our results further indicate that variations in channel and catchment metrics are not linked to the prevalence of different rock types alone but to different successions of lithological units along the channels and within the catchments variations in channel slope and geomorphological mapping suggest that lithology dependent landsliding is the dominant process causing the observed large scale landscape diversity in the hausruck kobernauserwald range

multicentury glacier fluctuations in the swiss alps during the holocene subfossil remains of wood and peat from six swiss glaciers found in proglacial fluvial sediments indicate that glaciers were smaller than the 1985 reference level and climatic conditions allowed vegetation growth in now glaciated basins an extended data set of swiss glacier recessions consisting of 143 radiocarbon dates is presented to improve the chronology of glacier fluctuations a comparison with other archives and dated glacier advances suggests 12 major recession periods occurring at 9850 9600 93008650 85508050 77007550 74506550 61505950 57005500 52004400 43003400 28002700 21501850 14001200 cal yr bp it is proposed that major glacier fluctuations occurred on a multicentennial scale with a changing pattern during the course of the holocene after the younger dryas glaciers receded to a smaller extent and prolonged recessions occurred repeatedly culminating around 7 cal kyr bp after a transition around 6 cal kyr bp weak fluctuations around the present level dominated after 3 6 cal kyr bp less frequent recessions interrupted the trend to advanced glaciers peaking with the prominent little ice age this trend is in line with a continuous decrease of summer insolation during the holocene

application of inventory data for estimating characteristics of and regional climate change effects on mountain glaciers a pilot study with the european alps a parameterization scheme using simple algorithms for unmeasured glaciers is being applied to glacier inventory data to estimate the basic glaciological characteristics of the inventoried ice bodies and simulate potential climate change effects on mountain glaciers for past and potential climate scenarios glacier changes for assumed mass balance changes are calculated as step functions between steady state conditions for time intervals that approximately correspond to the characteristic dynamic response time a few decades of the glaciers in order to test the procedure a pilot study was carried out in the european alps where detailed glacier inventories had been compiled around the mid 1970s total glacier volume in the alps is estimated at about 130 km3 for the mid 1970s strongly negative mass balances are likely to have caused a loss of about 10 20 of this total volume during the decade 1980 90 backward calculation of glacier length changes using a mean annual mass balance of 0 25m w e a 1 since the end of the little ice age around 1850 ad gives considerable scatter but satisfactory overall results as compared with long term observations the total loss of alpine surface ice mass since 1850 can be estimated at about half the original value an acceleration of this development with annual mass losses of around 1 m a 1 or more as anticipated from ipcc scenario a for the coming century could eliminate major parts of the presently existing alpine ice volume within decades

numerical modelling of historical front variations and dynamic response of sofiyskiy glacier altai mountains russia the recent fluctuation of the central asian climate and its effect on the region s glaciers is poorly known largely because of a lack of knowledge of the dynamic behaviour of so called summer accumulation type glaciers in this study a one dimen sional numericalglaciermodelisusedtosimulatethedynamicresponseof sofiyskiyglacier altai mountains russia to climate forcing a successful simulation of the observed histor ical front variations was accomplished by dynamic calibration this resulted in a recon struction of the recent mass balance history of the glacier showing a distinct decline in surface massbalance in the second half of the19th century a slightly higher massbalance at the beginning of the 20th century followed by a steady decline towards present condi tions the future response of sofiyskiy glacier was projected for six 21st century climate scenarios undera no change scenario the glacier will retreat 42kmby 2100 if airtem perature gradually risesby 45 c during this century the glacier will vanish around 2100 basic response characteristics of sofiyskiy glacier were determined these indicate rather low mass balance sensitivity to temperature change but a strong front reaction due to geo metric conditions

holocene glacier variation chronology of the smorstabbtindan massif jotunheimen southern norway and the recognition of century to millennial scale european neoglacial events new stratigraphic evidence for the holocene history of three glaciers in central jotunheimen southern norway is presented and the implications for century to millennial scale glacier and climatic variability are considered minerogenic layers in seven stream bank mires flooded episodically by glaciofluvial meltwater are dated by 79 new radiocarbon age estimates a revised chronology for glacier variations in smorstabbtindan suggests a three phase holocene 1 an early holocene deglaciation phase 11500 9500 cal bp characterized by readvances of ice sheet remnants 2 a mid holocene phase with relatively small or absent glaciers 9500 5000 cal bp and 3 a late holocene phase of enlarged and fluctuating glaciers the last 5000 years seven millennial scale neoglacial events smorstabbtindan i vii during which glaciers were larger than at present for most of the time are dated to 10 400 9600 erdalen event 8400 7650 finse event 4800 3900 3200 2550 2350 1700 1400 750 and 500 0 cal

the δ18o record along the greenland ice core project deep ice core and the problem of possible eemian climatic instability over 70 000 samples from the 3029 m long greenland ice core project grip ice core drilled on the top of the greenland ice sheet summit have been analyzed for 8o a highly detailed and continuous 8o profile has thus been obtained and is discussed in terms of past temperatures in greenland we also discuss a three core stacked annual 8o profile for the past 917 years the short term 50 years variability of the annual 8o signal is found to be 1 in the holocene and estimates for the coldest parts of the last glacial are 3 or higher these data also provide insights into possible disturbances of the stratigraphic layering in the core which seems to be sound down to the onset of the eemian spectral analysis of highly detailed sequences of the profile helps determine the smoothing of the 8o signal which for the holocene ice is found to be considerably stronger than expected we suggest this is due to a process involving diffusion of water molecules along crystal boundaries in the recrystallizing ice matrix deconvolution techniques were employed for restoring with great confidence the highly attenuated annual 8o signal in the holocene we confirm earlier findings of dramatic temperature changes in greenland during the last glacial cycle abrupt and strong climatic shifts are also found within the eem sangamon interglaciation which is normally recorded as a period of warm and stable climate in lower latitudes the stratigraphic continuity of the eemian layers is consequently discussed in section 3 of this paper in terms of all pertinent data which we are not able to reconcile

latest pleistocene and holocene glacier fluctuations in western canada we summarize evidence of the latest pleistocene and holocene glacier fluctuations in the canadian cordillera our review focuses primarily on studies completed after 1988 when the first comprehensive review of such evidence was published the cordilleran ice sheet reached its maximum extent about 16 ka and then rapidly decayed some lobes of the ice sheet valley glaciers and cirque glaciers advanced one or more times between 15 and 11 ka by 11 ka or soon thereafter glacier cover in the cordillera was no more extensive than at the end of the 20th century glaciers were least extensive between 11 and 7 ka a general expansion of glaciers began as early as 8 4 ka when glaciers overrode forests in the southern coast mountains it culminated with the climactic advances of the little ice age holocene glacier expansion was not continuous but rather was punctuated by advances and retreats on a variety of timescales radiocarbon ages of wood collected from glacier forefields reveal six major periods of glacier advance 8 59 8 18 7 36 6 45 4 40 3 97 3 54 2 77 1 71 1 30 ka and the past millennium tree ring and lichenometric dating shows that glaciers began their little ice age advances as early as the 11th century and reached their maximum holocene positions during the early 18th or mid 19th century our data confirm a previously suggested pattern of episodic but successively greater holocene glacier expansion from the early holocene to the climactic advances of the little ice age presumably driven by decreasing summer insolation throughout the holocene proxy climate records indicate that glaciers advanced during the little ice age in response to cold conditions that coincided with times of sunspot minima priority research required to further advance our understanding of late pleistocene and holocene glaciation in western canada includes constraining the age of late pleistocene moraines in northern british columbia and yukon territory expanding the use of cosmogenic surface exposure dating techniques using multi proxy paleoclimate approaches and directing more of the research effort to the northern canadian cordillera

late holocene glacier variations in the frontal and inner ranges of the tian shan central asia evidence for the timing and extent of late holocene glacial advances in the tian shan mountains central asia is based on lichenometric and radiocarbon dating of end moraines three phases of glacial advance occurred at 1700 2100 and 1100 1300 lichenometric l years ago and then during the little ice age 150 700 l years ago differences in the pattern of glacier variations between the northwestern frontal and inner areas of the tian shan are reflected in the equilibrium line altitude ela depression of 23 glaciers studied at nine selected sites the peripheral glaciers appear to have been significantly more extensive during late holocene advances than the glaciers of the inner areas this difference seems to be explained by regional differences in humidification in the northwestern periphery of the tian shan the cold periods of the late holocene were more humid than the warm period of the mid holocene whereas in the inner areas the pattern of climate changes was the opposite a warm and hu

the glacially overdeepened trough of the salzach valley austria bedrock geometry and sedimentary fill of a major alpine subglacial basin abstract overdeepened valleys are unambiguous features of glacially sculpted landscapes they result from erosion at the bed of the glacier and their size and shape is determined by ice dynamics and the characteristics of the underlying bedrock major overdeepened valleys representing vertical bedrock erosion of several hundreds of meters are characteristic features of many trunk valleys in the formerly glaciated parts of the alpine mountain belt the thick sedimentary fill usually hinders attempts to unravel bedrock geometry formation history and fill characteristics based on reflection seismic data and core logs from multiple deep drillings we construct a detailed bedrock model of the lower salzach valley trough one of the largest overdeepened valleys in the european alps the analysed overdeepened structure characterized by a strongly undulating topography two reaches of enhanced erosion can be identified and are suggested to be related to variations in bedrock erodibility and a triple glacier confluence the sedimentary fill shows clear characteristics of rapid infilling and subaqueous fan delta deposits indicate a strong influence of tributary streams associated surface lowering of the valley floor had a major impact on tributary stream incision but also on the available ice accumulation area at subsequent glaciations the extent to which fills of earlier glaciations have been preserved from erosion during the last glacial maximum remains ambiguous and demands further exploration to our knowledge the presented bedrock model is one of the best defined of any major overdeepened trunk valley

climatically driven late pleistocene holocene hydrological system transformation and landscape evolution in the eastern periphery of chuya basin se altai russia abstract this paper presents the results of geological geomorphological geochronological investigations and the analysis of the biological composition of deposits within the high mountainous boguty river basin the main stages of landscape evolution during the last 14 ka have been investigated through 32 radiocarbon dates the area is located in the most arid southeastern part of russian altai and constitutes the eastern periphery of the chuya intermountain depression and the western side of the chikhachev range postglacial landscape development of the upper reaches of the chuya river began from the degradation of its vast glaciation by 14 ka cal bp the glaciers had either completely melted or retreated above 2500 m above sea level as a result numerous lakes occupied open places and five types of these basins can be seen in the modern topography they are large moraine dammed lakes connected with the boguty river while some basins have been dammed by uplifted tectonic blocks and numerous lakes are of thermokarst origin or are small cirque lakes and temporal lakes fed by seasonal meltwater from meteoric ground water and permafrost degradation large moraine dammed lakes within the boguty basin were developed before the holocene the water filling these basins was controlled by the height of moraine dams and by the depth of the boguty river incision the moraine dammed low boguty lake formed earlier than 10 ka cal bp its partial draining and transformation of littoral zone into peat bog took place about 8 2 7 6 ka cal bp as a result of the analysis of biological composition four stages of water level fluctuations in the lacustrine boggy system were recognized the specific geomorphic and sedimentary features in the middle part of the boguty basin determined the recurrence of debris flow events at about 8 7 2 9 1 0 65 and 0 3 ka cal bp but the last event occurred in june 2017 the occurrence of fossil forest soils dating to about 11 8 5 ka cal bp and of charcoals larix sibirica ledeb of about 8 5 7 8 ka cal bp indicate a prolonged period of developing forest vegetation in the boguty basin which is currently treeless in general the data suggest that in se altai the climate in the first half of the holocene was warmer and more humid in comparison with the modern one the second half of the holocene has been characterized by colder climate conditions accompanied by aridity intensification which became especially pronounced during the last 2 1 5 ka

the onset of neoglaciation 6000 years ago in western mongolia revealed by an ice core from the tsambagarav mountain range glacier highstands since the last glacial maximum are well documented for many regions but little is known about glacier fluctuations and lowstands during the holocene this is because the traces of minimum extents are difficult to identify and at many places are still ice covered limiting the access to sample material here we report a new approach to assess minimal glacier extent using a 72 m long surface to bedrock ice core drilled on khukh nuru uul a glacier in the tsambagarav mountain range of the mongolian altai 4130 m asl 48 39 338 n 90 50 826 e the small ice cap has low ice temperatures and flat bedrock topography at the drill site this indicates minimal lateral glacier flow and thereby preserved climate signals the upper two thirds of the ice core contain 200 years of climate information with annual resolution whereas the lower third is subject to strong thinning of the annual layers with a basal ice age of approximately 6000 years before present bp we interpret the basal ice age as indicative of ice free conditions in the tsambagarav mountain range at 4100 m asl prior to 6000 years bp this age marks the onset of the neoglaciation and the end of the holocene climate optimum the ice free conditions allow for adjusting the equilibrium line altitude ela and derive the glacier extent in the mongolian altai during the holocene climate optimum based on the ela shift we conclude that most of the glaciers are not remnants of the last glacial maximum but were formed during the second part of the holocene the ice core derived accumulation reconstruction suggests important changes in the precipitation pattern over the last 6000 years during formation of the glacier more humid conditions than presently prevailed followed by a long dry period from 5000 years bp until 250 years ago present conditions are more humid than during the past millennia this is consistent with precipitation evolution derived from lake sediment studies in the altai

formation and preservation of open framework gravel strata in unidirectional flows open framework gravel ofg in river deposits is important because of its exceptionally high permeability resulting from the lack of sediment in the pore spaces between the gravel grains fluvial ofg occurs as planar strata and cross strata of varying scale and is interbedded with sand and sandy gravel the origin of ofg has been related to 1 proportion of sand available relative to gravel 2 separation of sand from gravel during a specific flow stage and sediment transport rate either high falling or low 3 separation of sand from gravel in bedforms superimposed on the backs of larger bedforms 4 flow separation in the lee of dunes or unit bars laboratory flume experiments were undertaken to test and develop these theories for the origin of ofg bed sediment size distribution sandy gravel with a mean diameter of 1 5 mm was kept constant but flow depth flow velocity and aggradation rate were varied bedforms produced under these flow conditions were bedload sheets dunes and unit bars the fundamental cause of ofg is the sorting of sand from gravel associated with flow separation at the crest of bedforms and further segregation of grain sizes during avalanching on the steep lee side sand in transport near the bed is deposited in the trough of the bedform whereas bed load gravel avalanches down the leeside and overruns the sand in the trough the effectiveness of this sorting mechanism increases as the height of the bedform increases infiltration of sand into the gravel framework is of minor importance in these experiments and occurs mainly in bedform troughs the geometry and proportion of ofg in fluvial deposits are influenced by variation in height of bedforms as they migrate superposition of small bedforms on the backs of larger bedforms aggradation rate and changes in sediment supply if the height of a bedform increases as it migrates downstream so does the amount of ofg changes in the character of ofg on the lee side of unit bars depend on grain size sorting in the superimposed bedforms dunes and bedload sheets thick deposits of cross stratified ofg require high bedforms dunes unit bars and large amounts of aggradation these conditions might be expected to occur during high falling stages in the deeper parts of river channels adjacent to compound bar tails and downstream of confluence scours increase in the amount of sand supplied relative to gravel reduces the development of ofg such increases in sand supply may be related to falling flow stage and or upstream erosion of sandy deposits

strong seismic shaking of randomly prestressed brittle rocks rock damage and nonlinear attenuation strong seismic waves produce frequent episodes of transient oscillating dynamic stress in the shallow subsurface within seismically active areas dynamic stress drives slip on a network of preexisting small fracture planes and leaves residual stresses once shaking ceases the residual stresses act as prestresses during the next strong earthquake local failure occurs on fractures at low dynamic stresses where the prestresses are favorably aligned while most of the bulk rock remains intact hence nonlinear attenuation of strong seismic waves commences at dynamic stresses well below those for pervasive coulomb failure consideration of the fractal distribution of prestresses indicates that nonlinear attenuation increases rapidly with dynamic stress vertically propagating shear waves provide simple scaling relationships for quick application 1 nonlinear attenuation is concentrated near the quarter wavelength depth 2 the coulomb stress ratio dynamic lithostatic stress above the quarter wavelength depth scales with the sustained dynamic acceleration in g s rate and state friction thus provides estimates of the maximum sustained acceleration from coulomb stress ratio at failure 1 for regolith that has repeatedly failed 1 5 for shallow intact sandstone and 2 for shallow intact granite a potentially observable effect occurs with shallow brittle regolith on hillslopes where gravity causes net downslope creep during strong shaking analogous crack network behavior with prestress occurs in the damage zone surrounding the rupture zone of major faults pulverized rock forms at shallow depths when rock is repeatedly deformed in strong shaking to just beyond the elastic limit but strain does not localize into a crack network

glacier fluctuations during the past 2000 years abstract a global compilation of glacier advances and retreats for the past two millennia grouped by 17 regions excluding antarctica highlights the nature of glacier fluctuations during the late holocene the dataset includes 275 time series of glacier fluctuations based on historical tree ring lake sediment radiocarbon and terrestrial cosmogenic nuclide data the most detailed and reliable series for individual glaciers and regional compilations are compared with summer temperature and when available winter precipitation reconstructions the most important parameters for glacier mass balance in many cases major glacier advances correlate with multi decadal periods of decreased summer temperature in a few cases such as in arctic alaska and western canada some glacier advances occurred during relatively warm wet times the timing and scale of glacier fluctuations over the past two millennia varies greatly from region to region however the number of glacier advances shows a clear pattern for the high mid and low latitudes and hence points to common forcing factors acting at the global scale globally during the first millennium ce glaciers were smaller than between the advances in 13th to early 20th centuries ce the precise extent of glacier retreat in the first millennium is not well defined however the most conservative estimates indicate that during the 1st and 2nd centuries in some regions glaciers were smaller than at the end of 20th early 21st centuries other periods of glacier retreat are identified regionally during the 5th and 8th centuries in the european alps in the 3rd 6th and 9th centuries in norway during the 10th 13th centuries in southern alaska and in the 18th century in spitsbergen however no single period of common global glacier retreat of centennial duration except for the past century has yet been identified in contrast the view that the little ice age was a period of global glacier expansion beginning in the 13th century or earlier and reaching a maximum in 17th 19th centuries is supported by our data the pattern of glacier variations in the past two millennia corresponds with cooling in reconstructed temperature records at the continental and hemispheric scales the number of glacier advances also broadly matches periods showing high volcanic activity and low solar irradiance over the past two millennia although the resolution of most glacier chronologies is not enough for robust statistical correlations glacier retreat in the past 100 150 years corresponds to the anthropogenic global temperature increase many questions concerning the relative strength of forcing factors that drove glacier variations in the past 2 ka still remain

chronology of the last glacial maximum in the salzach palaeoglacier area eastern alps a chronostratigraphy based on luminescence data was established at a key loess profile duttendorf in the northern alpine foreland of austria the data help to constrain the timing and duration of the last glacial maximum lgm in the area of one of the largest east alpine piedmont glaciers the salzach palaeoglacier climate deterioration and maximum advance of this glacier were coeval with the beginning of the main loess accumulation phase in the glacier forefield at 29 30 ka a late lgm outwash gravel layer deposited on top of the loess profile marks the end of the lgm glacier activity at 20 ka the geomorphological setting around the loess profile provides evidence of a major glacier oscillation during the course of the lgm a phenomenon qualitatively known from other alpine palaeoglaciers but never interpreted in terms of palaeoclimate a lgm glacier oscillation similar to that of the salzach palaeoglacier was reported recently from the south alpine tagliamento palaeoglacier suggesting a common forcing the onset of loess deposition at duttendorf and the tentatively contemporal advance of the salzach palaeoglacier reflect as do other data the drastic cooling in europe as a result of heinrich event 3 the first glacier maximum is not well constrained in the study area but a correlation with the better dated tagliamento amphitheatre suggests a possible response to heinrich 2 the second re advance occurred synchronously within dating uncertainties in both palaeoglaciers forefields at 21 ka but the forcing mechanism remains unknown copyright 2011 john wiley sons ltd

identification of erosional mechanisms during past glaciations based on a bedrock surface model of the central european alps the bedrock topography beneath the quaternary cover provides an important archive for the identification of erosional processes during past glaciations here we combined stratigraphic investigations of more than 40 000 boreholes with published data to generate a bedrock topography model for the entire plateau north of the swiss alps including the valleys within the mountain belt we compared the bedrock map with data about the pattern of the erosional resistance of alpine rocks to identify the controls of the lithologic architecture on the location of overdeepenings we additionally used the bedrock topography map as a basis to calculate the erosional potential of the alpine glaciers which was related to the thickness of the lgm ice we used these calculations to interpret how glaciers with support by subglacial meltwater under pressure might have shaped the bedrock topography of the alps we found that the erosional resistance of the bedrock lithology mainly explains where overdeepenings in the alpine valleys and the plateau occur in particular in the alpine valleys the locations of overdeepenings largely overlap with areas where the underlying bedrock has a low erosional resistance or where it was shattered by faults we also found that the assignment of two end member scenarios of erosion related to glacial abrasion plucking in the alpine valleys and dissection by subglacial meltwater in the plateau may be adequate to explain the pattern of overdeepenings in the alpine realm this most likely points to the topographic controls on glacial scouring in the alps the flow of lgm and previous glaciers were constrained by valley flanks while ice flow was mostly divergent on the plateau where valley borders are absent we suggest that these differences in landscape conditioning might have contributed to the contrasts in the formation of overdeepenings in the alpine valleys and the plateau

vanishing iron smelting furnaces of the south eastern altai russia evidences for highly developed metallurgical production of ancient nomads abstracts results of multidisciplinary investigations of ferrous metallurgy archaeological sites within four locations in the south eastern altai russia are presented radiocarbon dating applying both conventional and ams techniques evidences for constructing and operating of iron smelting furnaces during the turk period the second half of the 5th 11th centuries ad trees larix sibirica more than 100 years old were utilized for charcoal production generally larches growth in 2nd 10th centuries ad were used in metallurgical process in the kuektanar 1 kuektanar 2 and turgun 1 sites belonging to the chuya kurai metallurgical zone the time of the last iron production for the bloomery iron smelting furnace in the kuektanar 1 site was reliably established falling between ad 655 and 765 mineral composition of slag from the kuektanar 1 site indicates that two types of the ore quartz hematite and siderite could be utilized for iron production the high ca k and al content in some slag droplets evidence for possible presence of calcite in the initial ore or flux additives a small amount of fluxes could come from the clay lining of the bloomery hearth generally high concentration of furnaces near the kuektanar mouth and in the turgun valley was determined by wide spreading of forest vegetation in an area and close location of ore occurrences intensive timber consumption by nomadic societies together with the progressive aridity intensification led to total deforestation of the eastern part of the chuya depression

the genesis of the northern kettle moraine wisconsin interpreting past glacial dynamics from the glacial record requires that the depositional environments of glacial sediments and landforms be understood in the case of interlobate deposits models that incorporate various components of pro supra and subglacial deposition have been developed and tested in the northern kettle moraine nkm wisconsin a large interlobate deposit that formed between the green bay and lake michigan lobes of the laurentide ice sheet during the last deglaciation in this paper we interpret a new genesis for the nkm using sediment analysis and distribution along with landform distribution in sheboygan county the nkm consists of two steep sided high relief hummocky ridges separated by a low elevation and low relief central axis gravel in the bounding hummocky ridges is well sorted and well rounded some bedding is collapsed large isolated moulin kames are restricted to the axis area and composed of relatively poorly sorted more angular gravel and diamicton the distribution of these different sediments and landforms are explained by the accumulation of supraglacial debris that insulated the ice below the axis of the nkm while the melting of cleaner ice on either side formed channels on the ice surface as deglaciation proceeded a substantial thickness of well rounded stream deposited sand and gravel accumulated on ice in the bounding channels eventual collapse of this sediment formed the two hummocky ridges poorly sorted debris along the axis fell and slid into moulins and larger collapse areas in the ice thus differential debris insulation and ice ablation controlled the mainly supraglacial deposition of this part of the nkm

transition between stable sliding and stick slip due to variation in slip rate under variable normal stress condition this paper discusses a new mechanism that may control the transition between stable sliding and cyclic stick slip under variable normal stress condition with a rate and state dependent friction law that embodies the effect of normal stress a single degree of freedom spring slider system inclined to the driving direction has a velocity dependent critical stiffness which separates stable sliding and cyclic stick slip with steady state log linear rate dependent friction the critical stiffness decreases with increasing velocity accordingly higher velocity stabilizes a system for a predetermined stiffness lower than the critical value and may change the motion from cyclic stick slip to stable sliding and vice versa our numerical simulations in full dynamic motion confirmed such transition and agreed well with the analytical calculation such transitions can also be found in experimental works

a continuous stable isotope record from the penultimate glacial maximum to the last interglacial 159 121 ka from tana che urla cave apuan alps central italy abstract relatively few radiometrically dated records are available for the central mediterranean spanning the marine oxygen isotope stage 6 5 mis 6 5 transition and the first part of the last interglacial two flowstone cores from tana che urla cave tcu central italy constrained by 19 u th ages preserve an interval of continuous speleothem deposition between ca 159 and 121 ka a multiproxy record 18 o 13 c growth rate and petrographic changes obtained from this flowstone preserves significant regional scale hydrological changes through the glacial interglacial transition and multi centennial variability interpreted as alternations between wetter and drier periods within both glacial and interglacial stages the glacial stage shows a wetter period between ca 154 and 152 ka while the early to middle last interglacial period shows several drying events at ca 129 126 and 122 ka which can be placed in the wider context of climatic instability emerging from north atlantic marine and nw european terrestrial records the tcu record also provides important insights into the evolution of local environmental conditions i e soil development in response to regional and global scale climate events

evolution of an overdeepened trough in the northern alpine foreland at niederweningen switzerland quaternary deposits in the overdeepened wehntal switzerland were investigated using both seismicprofiling and the analysis of 93 6 m long drill core using sedimentology geochemistry palynology

heterogeneity patterns of quaternary glaciofluvial gravel bodies sw germany application to hydrogeology abstract the architecture of sedimentary bodies determines the heterogeneity of many aquifers thus for environmental risk assessment and quantification of clean up efficiencies determination of the spatial distribution of hydraulic properties is required in this study outcrop analogues of glaciofluvial gravel bed deposits are used for a process based analysis of sedimentary heterogeneities which in turn are transformed into hydraulic parameters three scales of heterogeneities are distinguished a the lithofacies scale is formed by unique transport and depositional processes that form the fundamental building blocks hydrofacies types b the depositional element scale shows distinct geometrical characteristics internal structure and bounding surfaces and determines the local distribution of lithofacies and hence the correlation structure of permeabilities c the architectural scale of gravel bodies is formed by the stacking of depositional elements which is controlled by the dynamics of aggrading paleofluvial systems comparison of numerous gravel pits in sw germany revealed three major architectural patterns of glaciofluvial gravel bodies that can be distinguished statistically by the preservation of depositional elements as well as the frequency of lithofacies types the facies analysis results in three conceptual facies models of proglacial river systems which are regionally classified as main intermediate and minor discharge types based on calculated and laboratory measured hydraulic properties of the various lithofacies types detailed outcrop wall maps were digitized into polygons of defined hydrofacies types by using the gis system arc info the two dimensional fields of hydraulic properties were then transferred into a numerical model of groundwater flow modeling results clearly illustrate that the three heterogeneity patterns of gravel bodies also have distinguishable hydraulic response characteristics

a quantitative three dimensional depositional model of gravelly braided rivers a quantitative three dimensional depositional model of gravelly braided rivers has been developed based largely on the deposits of the sagavanirktok river in northern alaska these deposits were described using cores wireline logs trenches and ground penetrating radar profiles the origin of the deposits was inferred from observations of 1 channel and bar formation and migration and channel filling interpreted from aerial photographs 2 water flow during floods and 3 the topography and texture of the river bed at low flow stage this depositional model quantitatively represents the geometry of the different scales of strataset the spatial relationships among them and their sediment texture distribution porosity and permeability in the model are related to sediment texture the geometry of a particular type and scale of strataset is related to the geometry and migration of the bedform type e g ripples dunes bedload sheets bars associated with deposition of the strataset in particular the length to thickness ratio of stratasets is similar to the wavelength to height ratio of associated bedforms furthermore the wavelength and height of bedforms such as dunes and bars are related to channel depth and width therefore the thickness of a particular scale of strataset i e medium scale cross sets and large scale sets of inclined strata will vary with river dimensions these relationships between the dimensions of stratasets bedforms and channels mean that this depositional model can be applied to other gravelly fluvial deposits the depositional model can be used to interpret the origin of ancient gravelly fluvial deposits and to aid in the characterization of gravelly fluvial aquifers and hydrocarbon reservoirs

from morphostratigraphy to geochronology on the dating of ice marginal positions abstract this study focuses on the glacial landscape of northern germany as a part of the southwestern sector of the scandinavian ice sheet sis as it has a research history reaching back about 130 years since the glacial theory replaced the drift theory in the late 19th century it has experienced a number of key changes including the introduction of the concept of polyglaciation or the differentiation of ice advances within one glaciation which is closely linked to the morphostratigraphical definition of ice marginal positions with the development of numerical dating methods the rather static morphostratigraphically based chronologies which are deeply rooted in research history have been confronted with a growing number of geochronometrical data obtained from glacigenic deposits in order to date ice marginal positions the two most commonly used dating methods for that purpose are optically stimulated luminescence osl and surface exposure dating of erratic boulders this study highlights the dependency of the significance of results from different dating methods on the sampling position within the geomorphological framework results from osl and surface exposure dating for the same ice marginal position in theory cannot be the same as the methods date different processes in the development of the glacial landscape osl dating of fluvioglacial sandur sediments dating the process of active sedimentation at the ice front and surface exposure dating of boulders on end moraines dating the process of stabilisation of end moraines after the retreat of the ice front often qualify as the most useful combination of techniques in order to define a time interval for the formation of the landforms at a specific ice marginal position methodological drawbacks which might occur unfortunately tend to widen the process induced offset between osl and surface exposure ages incomplete bleaching of fluvioglacial sediments might cause an offset towards a maximum osl age for an ice marginal position whereas delayed stabilisation or post exposure relocation of boulders might cause a shift towards a minimum age of key importance are the influence of periglacial processes and the effects of melting of buried ice on landform stabilisation which remain to be quantified a possible solution to this problem combining osl and surface exposure dating is suggested in this study nevertheless the possibility exists to date different geomorphological processes by applying different dating methods to glacigenic deposits this allows for a differentiated reflection of morphostratigraphically based chronologies against the background of the modern concept of dynamic ice sheets in contrast to the traditional morphostratigraphical definition of ice marginal positions a time based definition is proposed because it offers the possibility of a more detailed reconstruction of ice sheet dynamics at a certain point in time

post late glacial calcareous tufas from the kurai fault zone southeastern gorny altai russia abstract calcareous tufa deposits have been discovered in the chibitka river valley near lake cheybek kohl at the junction of the kurai and teletsk kurai large active faults in the southeastern gorny altai russia at an altitude of 1800 2000 m fossil tufa is composed of calcite and cements holocene grey colluvium and glacial till deposited by the late glacial chibitka glacier current tufa precipitation has been observed from a low flow spring with cold 10 c hco 3 so 4 ca mg water 6 86 the stable isotope composition of spring water is 5 8 vpdb 13 c of dissolved inorganic carbon and 14 5 vsmow 18 o modern tufa consists of thin laminated mg calcite and sr aragonite crusts with abundant algae and biofilms on their surfaces both modern and fossil tufas are depleted in ree a total of 0 40 16 4 ppm and 0 40 3 80 ppm respectively and share similar paas normalised ree y spectra with hree enrichment and slight progressive lree depletion the modern tufas show positive 13 c values of 0 1 to 0 9 vpdb while the fossil ones have an isotopically lighter composition of 13 c 4 1 to 1 9 vpdb the 18 o range is very narrow 13 0 to 13 8 vpdb both stable isotope and trace element signatures including ree patterns of the tufas indicate precipitation from cold groundwaters subjected to prolonged interaction with a carbonate aquifer the baratal group of limestone and dolostone in a cold continental climate similar to the present conditions tufa deposition in the lake cheybek kohl area began with the onset of post late glacial global warming and permafrost degradation unlike the fossil tufa formation current precipitation of freshwater carbonates has been microbially mediated the discovered tufa deposits provide new palaeoclimatic and active tectonic proxies in the southeastern gorny altai

palaeoecology of quaternary periglacial environments during ois 2 in the forefields of the salzach glacier upper austria palaeopedological sedimentological and palaeoecological investigations were carried out on the pleniglacial loess deposits of duttendorf austria in the area of the pleistocene salzach glacier detailed insights into the past climate topography and vegetation especially during the oxygen isotopic stage 2 ois 2 were obtained according to the results it seems that alluvial processes played a more important role for the genesis of the loess deposits during the late glacial maximum lgm than previously assumed the pollen record plant macro remains and malaco fauna yield the occurrence of hygrophilous taxa as well as of water plants by consequence the sediment can be regarded as alluvial loess furthermore the results show that the landscape corresponded not only to a cold and dry loess steppe environment but was also partly influenced by humid conditions and that probably even small water bodies may have existed

chronology of the last glacial cycle in the european alps chronological data for glacier advances in the european alps between the last interglacial eemian and the holocene are summarised 115 to 11 ka during this time glaciers were most extensive extending tens of kilometres out onto the forelands between 30 and 18 ka that is synchronous with the global ice volume maximum of marine isotope stage mis 2 evidence for ice expanding to just past the mountain front for an earlier major glacier advance comes from swiss sites where advances have been luminescence dated to mis 5d 100 ka and mis 4 70 ka up to now no such evidence has been found in the eastern alps by 18 ka more than 80 of the late wurmian ice volume had gone subsequently glaciers readvanced reaching into the upper reaches of the main valleys during the lateglacial gschnitz stadial which likely occurred around 17 ka with final moraine stabilisation no later than 15 4 ka the link of the egesen stadial with the younger dryas climate deterioration is supported by exposure ages from four sites as well as minimum limiting radiocarbon dates from bogs within former glacier tongue areas key questions on the spatial and temporal variability of ice extents throughout the last glacial cycle have yet to be answered copyright 2008 john wiley sons ltd

structures and textures in triassic braided stream conglomerates bunter pebble beds in the sherwood sandstone group north staffordshire england in the northern parts of the needwood and stafford eccleshall basins england the pebble beds of the sherwood sandstone group contain thick successions of texturally mature fluvial pebble cobble conglomerates which are organized into either horizontal or cross stratified sets the horizontally lying sets generally coarser grained and more poorly sorted than the cross bedded sets are usually disorganized and either matrix or clast supported although thin lenses of well sorted occasionally openwork units interpreted as falling stage phenomena are often present the cross stratified conglomerates have foresets exhibiting remarkable textural organization with a coarse bimodal sometimes matrix supported part grading upwards or being abruptly overlain by a finer well sorted occasionally openwork part and finally capped by sandstone these rhythmic textural changes are attributed partly to an avalanche process at high stage and partly to falling stage conditions the most common types of vertical association are thick successions of horizontally bedded conglomerates up to 20 m and sequences of an upwards coarsening nature 2 12 m in which cross stratified sets are overlain by flat lying sets the environment of deposition of the gravels is interpreted as one in which water depths at high stage were greater than depths in most modern braided stream plains proglacial or alluvial fan but shallower than depths associated with the pleistocene catastrophic floods from which texturally mature giant gravel bars have been recorded recent braided streams with relatively confined channels and considerable bar channel relief are better analogues in particular medial or mid channel bars with a two tier structure subaqueous and partly emergent portions may explain the upward coarsening sequences in which horizontally lying conglomerates overlie cross stratified conglomerates the thicker sequences of horizontally stratified conglomerates represent proximal longitudinal bar deposits sheets of pebbly sandstone and argillaceous sandstone lying between the conglomerates and commonly occurring towards the top of the succession largely represent deposition from sandwaves and dunes finer interbedded argillaceous sandstones siltstones and mudstones are interpreted as overbank and waning flood deposits basin forming tectonism of increasing intensity probably caused the initial coarsening upwards of the lower part of the succession whilst more stable tectonic conditions and decreasing relief on the margins of the basins and in the areas of provenance in the midlands and the hercynides account for the upwards fining of the upper part of the succession

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

lithofacies variations within sandur deposits the role of runoff regime flow dynamics and sediment supply characteristics abstract the icelandic sandur plains have for long acted as classic sites for models of braided river behaviour and of associated lithofacies assemblages however many of the icelandic sandurs are subject to repeated catastrophic flood events or jokulhlaups which are likely to have played a significant role in sandur construction established lithofacies models based on the icelandic sandurs have failed to take account of the varying runoff regimes which characterise the different sandur environments in addition sediment inputs to sandur channel systems are highly variable fluctuating in response both to varying runoff patterns and to advance and retreat of the source glacier that affect sediment availability within the proglacial zone this paper describes the main lithofacies types and vertical profiles that characterize the sandurs of south iceland and demonstrates that they can largely be attributed to extreme runoff events with few deposits typical of braided river facies occurring within the sedimentary record a preliminary qualitative model is developed that allows interpretation and prediction of vertical lithofacies profiles derived from glacial outwash in terms of i the drainage mechanism which in turn controls the dominant runoff population ii sediment availability and iii the spatial variability in flow dynamics

mid to late holocene climate change an overview the last 6000 years are of particular interest to the understanding of the earth system because the boundary conditions of the climate system did not change dramatically in comparison to larger glacial interglacial changes and because abundant detailed regional palaeoclimatic proxy records cover this period we use selected proxy based reconstructions of different climate variables together with state of the art time series of natural forcings orbital variations solar activity variations large tropical volcanic eruptions land cover and greenhouse gases underpinned by results from general circulation models gcms and earth system models of intermediate complexity emics to establish a comprehensive explanatory framework for climate changes from the mid holocene mh to pre industrial time the redistribution of solar energy due to orbital forcing on a millennial timescale was the cause of a progressive southward shift of the northern hemisphere nh summer position of the intertropical convergence zone itcz this was accompanied by a pronounced weakening of the monsoon systems in africa and asia and increasing dryness and desertification on both continents the associated summertime cooling of the nh combined with changing temperature gradients in the world oceans likely led to an increasing amplitude of the el nin o southern oscillation enso and possibly increasingly negative north atlantic oscillation nao indices up to the beginning of the last millennium on decadal to multi century timescales a worldwide coincidence between solar irradiance minima tropical volcanic eruptions and decadal to multi century scale cooling events was not found however reconstructions show that widespread decadal to multi century scale cooling events accompanied by advances of mountain glaciers occurred in the nh e g in scandinavia and the european alps this occurred namely during the little ice age lia between ad w1350 and 1850 when the lower summer insolation in the nh due to orbital forcing coincided with solar activity minima and several strong tropical volcanic eruptions the role of orbital forcing in the nh cooling the southward itcz shift and the desertifi cation of the sahara are supported by numerous model simulations other simulations have suggested that the fingerprint of solar activity variations should be strongest in the tropics but there is also evidence that changes in the ocean heat transport took place during the lia at high northern latitudes with possible additional implications for climates of the southern hemisphere sh

seismically damaged regolith as self organized fragile geological feature 1 the s wave velocity in the shallow subsurface within seismically active regions self organizes so that typical strong dynamic shear stresses marginally exceed the coulomb elastic limit the dynamic velocity from major strike slip faults yields simple dimensional relations the near field velocity pulse is essentially a love wave the dynamic shear strain is the ratio of the measured particle velocity over the deep s wave velocity the shallow dynamic shear stress is this quantity times the local shear modulus the dynamic shear traction on fault parallel vertical planes is finite at the free surface coulomb failure occurs on favorably oriented fractures and internally in intact rock i obtain the equilibrium shear modulus by starting a sequence of earthquakes with intact stiff rock extending all the way to the surface the imposed dynamic shear strain in stiff rock causes coulomb failure at shallow depths and leaves cracks in it wake cracked rock is more compliant than the original intact rock cracked rock is also weaker in friction but shear modulus changes have a larger effect each subsequent event causes additional shallow cracking until the rock becomes compliant enough that it just reaches coulomb failure over a shallow depth range of tens to hundreds of meters further events maintain the material at the shear modulus as a function where it just fails the formalism provided in the paper yields reasonable representation of the s wave velocity in exhumed sediments near cajon pass and the san fernando valley of california a general conclusion is that shallow rocks in seismically active areas just become nonlinear during typical shaking this process causes transient changes in s wave velocity but not strong nonlinear attenuation of seismic waves wave amplitudes significantly larger than typical ones would strongly attenuate and strongly damage the rock

application of rate and state friction laws to creep compaction of unconsolidated sand under hydrostatic loading conditions 1 rate and state variable friction laws describe the time dependent fault normal compaction that occurs during holds in slide hold slide friction tests on unconsolidated materials this time dependent deformation is qualitatively similar to that observed during volumetric creep strain tests on unconsolidated sands and shales under hydrostatic loading conditions to test whether rate and state friction laws can be used to model volumetric creep processes in unconsolidated sands the rate and state formulation is expanded to include deformation under hydrostatic stress boundary conditions results show that the hydrostatic stress form of the rate and state friction law successfully describes the creep strain of unconsolidated sand more importantly values obtained for rate and state friction parameters by fitting these data are in the same range as those obtained from more traditional tests by fitting the fault normal compaction of simulated gouge during a hold in a laboratory friction experiment

palaeoclimate glacier and treeline reconstruction based on geomorphic evidences in the mongun taiga massif south eastern russian altai during the late pleistocene and holocene abstract little is known about the extent of glaciers and dynamics of the landscape in south eastern russian altai the effects of climate induced fluctuations of the glaciers and the upper treeline of the mongun taiga mountain massif were therefore reconstructed on the basis of in situ multiannual observations geomorphic mapping radiocarbon and surface exposure dating relative dating such as schmidt hammer and weathering rind techniques and palaeoclimate modelling during the maximal advance of the glaciers their area was 26 times larger than now and the equilibrium line of altitude ela was about 800 m lower assuming that the maximum glacier extent took place during mis 4 then the average summer temperatures were 2 7 c cooler than today and the amount of precipitation 2 1 times higher buried wood trunks by a glacier gave ages between 60 and 28 cal ka bp and were found 600 700 m higher than the present upper treeline this evidences a distinctly elevated treeline during mis 3a and c with a correction for tectonics we reconstructed the summer warming to have been between 2 1 and 3 0 c during mis 3c the glaciated area was reduced to less than 0 5 km2 with an increase of the ela of 310 470 m higher than today due to higher precipitation the glaciated area during mis 3a was close to the current ela exposure dating 10be would indicate that the maximum glacier extension was 24 ka bp but the results are questionable from a geomorphic point of view the maximum extent can more likely be ascribed to the mis4 stage we estimate a cooling of summer temperature of 3 8 to 4 2 c and a decrease in precipitation of 37 46 compared to the present day situation samples of wood having an age of 10 6 6 2 cal ka bp were found about 350 m higher than the present treeline it seems that the summer temperature was 2 0 2 5 c higher and annual precipitation was double that of the present day for that period the reconstructed glaciation area was 1 km2 less than today three neoglacial glacier advances were detected the glaciers covered about double the area during the little ice age lia summer cooling was 1 3 c with 70 of the present day precipitation the reconstructed amplitude of climatic changes and the shift of the altitudinal zones show that the landscape has reacted sensitively to environmental changes and that dramatic changes may occur in the near future

ductile creep compaction and rate and state dependent friction within major fault zones the shear traction on major strike slip faults during earthquakes is much lower than that expected on a frictionally sliding surface in equilibrium with hydrostatic pressure the low shear traction is explained if the fluid pressure at the time of the earthquake is much greater than hydrostatic pressure ductile creep within mostly sealed fault zones compacts the matrix and thus increases fluid pressure between earthquakes frictional dilatancy during earthquakes decreases fluid pressure below hydrostatic and over the earthquake cycle the fault zone is in long term equilibrium with the country rock this ductile mechanism is formally unified with rate and state theory for time dependent friction when the difference between a critical porosity where the rock loses all strength and the actual porosity of cracks is used as a state variable this choice is justified by percolation theory of mostly broken lattices time dependent behavior associated with changes in normal traction in the laboratory is explained by the formalism instability earthquakes sometimes occurs in the numerical experiments however fairly small amounts of frictional dilatancy during initial frictional creep decrease fluid pressure and preclude unstable sliding two coupled mechanisms for producing dilatancy on faults once an instability is well underway are evident 1 expansion of pore fluids associated with frictional heating increases fluid pressure offsetting the effects of increased pore volume during earthquakes there is some tendency for pore volume increase to balance fluid expansion so that fluid pressure stays relatively constant 2 production of isolated voids that do not immediately decrease fluid pressure throughout the fault zone during earthquakes can occur to the extent that the fault zone is not significantly strengthened although the extent of both processes is constrained by energy considerations the variation of fluid pressure during earthquakes is not yet well enough understood to predict stress drop from observable material properties

late pleistocene climate change and landscape dynamics in the eastern alps the inner alpine unterangerberg record austria drill cores from the inner alpine valley terrace of unterangerberg located in the eastern alps of austria offer first insights into a pleistocene sedimentary record that was not accessible so far the succession comprises diamict gravel sand lignite and thick fine grained sediments additionally cataclastic deposits originating from two paleo landslide events are present multi proxy analyses including sedimentological and palynological investigations as well as radiocarbon and luminescence data record the onset of the last glacial period wurmian at unterangerberg at 120 110 ka this first time period correlated to the mis 5d was characterised by strong fluvial aggradation under cold climatic conditions with only sparse vegetation cover furthermore two large and quasi synchronous landslide events occurred during this time interval no record of the first early wurmian interstadial mis 5c is preserved during the second early wurmian interstadial mis 5a the local vegetation was characterised by a boreal forest dominated by picea with few thermophilous elements the subsequent collapse of the vegetation is recorded by sediments dated to 70 60 ka i e mis 4 with very low pollen concentrations and the potential presence of permafrost climatic conditions improved again between 55 and 45 ka mis 3 and cold adapted trees re appeared during interstadials forming an open forest vegetation mis 3 stadials were shorter and less severe than the mis 4 at unterangerberg and vegetation during these cold phases was mainly composed of shrubs herbs and grasses similar to what is known from today s alpine timberline the unterangerberg record ended at 45 ka and or was truncated by ice during the last glacial maximum

the role of pingos in the development of the dzhangyskol lake pingo complex central altai mountains southern siberia abstract dzhangyskol is a small lake of glacial origin in the central part of the altai mountains in southern siberia pollen stratigraphies and chronologies of two cores record the vegetational development of the area from the late glacial treeless landscape to the forest and steppe of today the modern lake is a remnant of a much larger ice dammed lake which was reduced in size and then temporarily drained after diversion of the inflowing mountain meltwater stream which had low 18o values the dry lake floor allowed development of permafrost and small pingos frozen mounds of lake sediments with the onset of greater climatic humidity in the mid holocene the input of local water with higher 18o caused a rise in lake level drowning the earlier pingos growth of a broad fen on the margin of the lake led to formation of a modern pingo complex

luminescence dating of the rissian type section in southern germany as a base for correlation abstract the exact timing of the rissian has been under discussion since being established by penck and bruckner 1909 at the beginning of the 20th century difficulties in correlating and especially dating the sediments associated with the rissian have led to different nomenclatures in the different regions of the northern alpine foreland naf various dating approaches have led so far to often unsatisfying results in this study we successfully dated the high terrace gravels of the rissian type section using single grain feldspar luminescence we were able to evade the problems of incomplete bleaching in fluvioglacial sediments using the post infrared irsl protocol at 225 c we were able to show that the feldspar in the research area only shows low rates of anomalous fading we were able to show that these low fading rates have an influence on the age determination this is remarkable because many of the signals were close to saturation the conclusive age range of 149 15 179 17 ka corresponds to marine isotope stage 6 defining an age for the rissian is a first step to consolidate the heterogeneous nomenclature and to reconstruct the chronology of past major alpine glaciations

holocene glacier fluctuations a global overview of glacier advances and retreats grouped by regions and by millennia for the holocene is compiled from previous studies the reconstructions of glacier fluctuations are based on 1 mapping and dating moraines defined by 14 c tcn osl lichenometry and tree rings discontinuous records time series and 2 sediments from proglacial lakes and speleothems continuous records time series using 189 continuous and discontinuous time series the long term trends and centennial fluctuations of glaciers were compared to trends in the recession of northern and mountain tree lines and with orbital solar and volcanic studies to examine the likely forcing factors that drove the changes recorded a general trend of increasing glacier size from the earlyemid holocene to the late holocene in the extra tropical areas of the northern hemisphere nh is related to overall summer temperature forced by orbitally controlled insolation the glaciers in new zealand and in the tropical andes also appear to follow the orbital trend i e they were decreasing from the early holocene to the present in contrast glacier fluctuations in some monsoonal areas of asia and southern south america generally did not follow the orbital trends but fluctuated at a higher frequency possibly triggered by distinct teleconnections patterns during the neoglacial advances clustered at 4 4e4 2 ka 3 8e3 4 ka 3 3e2 8 ka 2 6 ka 2 3e2 1 ka 1 5e1 4 ka 1 2e1 0 ka 0 7e0 5 ka corresponding to general cooling periods in the north atlantic some of these episodes coincide with multidecadal periods of low solar activity but it is unclear what mechanism might link small changes in irradiance to widespread glacier fluctuations explosive volcanism may have played a role in some periods of glacier advances such as around 1 7e1 6 ka coinciding with the taupo volcanic eruption at 232 5 ce but the record of explosive volcanism is poorly known through the holocene the compilation of ages suggests that there is no single mechanism driving glacier fluctuations on a global scale multidecadal variations of solar and volcanic activity supported by positive feedbacks in the climate system may have played a critical role in holocene glaciation but further research on such linkages is needed the rate and the global character of glacier retreat in the 20th through early 21st centuries appears unusual in the context of holocene glaciation though the retreating glaciers in most parts of the northern hemisphere are still larger today than they were in the early and or mid holocene the current retreat

quaternary glacial chronology of the kanas river valley altai mountains china the kanas river originates on the southern slope of youyi peak the largest center of modern glaciation in the altai mountains in central asia glaciers advanced and retreated repeatedly during quaternary glacialeinterglacial cycles in the kanas river valley and four moraine complexes and associated glaciofluvial deposits are preserved in the valley optically stimulated luminescence osl dating has been used to determine ages of glaciofluvial deposits sand lenses sandwiched between tills in moraines using a single aliquot regenerative dose sar protocol based on dating results from this and previous studies including 14 c electron spin resonance esr and osl dates and geomorphic relationships the innermost moraine complex was concluded to deposit during the little ice age lia the second akekule moraine complex was deposited during the neoglacial the third kanas moraine complex was deposited during the last glacial cycle marine oxygen isotope stage mis 2e4 and the outermost set of moraines is mis 6 in ages penultimate glaciation the kanas moraine complex could be divided into three subsets iii1 iii2 and iii3 with inferred ages of mis 2 mid mis 3 and mis 4 respectively which is consistent with moraine records from other areas in central asia and climate reconstructions from the guliya ice core the glaciers in the kanas valley at their maximum extents during the lia neoglacial last glaciation and penultimate glaciation were 13 8 km 32 km w100 km and w120 km long respectively

environmental change during the holocene in western china on a millennial timescale recent data on the evolution of the inland lakes loess palaeosol sequences and glacier variations in western china are briefly reviewed the lake history shows three distinct stages in the holocene i e low water levels before 7500 bp a stage of expansion during the climatic optimum between 7500 and 3500 bp and contraction after 3500 bp three stages wooded grassland mixed woodland wooded grassland becoming steppe also appear indicated by the holocene loess palaeosol sequence in the lanzhou region the optimal period for soil development being between 7500 and 3500 bp there were seven periods of glacier advance the continental glaciers advanced at about 8300 5700 4000 and 400 bp in northwestern china and the maritime glaciers advanced at about 3000 2000 1000 and 200 bp it is suggested that the climatic changes show two periodicities during the holocene namely at intervals of about 2500 and 1000 years

luminescence dating of glaciofluvial deposits linked to the penultimate glaciation in the eastern alps during the penultimate glaciation vast areas of the alps were glaciated with piedmont glaciers protruding into the foreland in the easternmost part of the northward draining valleys of the alps the glaciers did not reach the foreland but formed valley glaciers confined by the mountainous terrain this also applies to the ybbs valley where samples for luminescence dating out of glaciofluvial gravel accumulations were taken at three locations along the present day river course in a highly dynamic depositional environment such as a glacier fed river system incomplete resetting of the luminescence signal is possible in particular when transport distances are short in such cases quartz usually is the preferred mineral over feldspar especially if dose rates are low and may theoretically allow obtaining quartz ages beyond 150 ka because previous research has shown and as corroborated within this study quartz from the research area exhibits analytical problems in the high age range therefore luminescence properties of coarse grain 100 200 m quartz and in addition k rich feldspar were investigated with the aim to reconstruct the chronology of the glacial processes within the ybbs catchment area issues of incomplete bleaching were pirir225 encountered and addressed by comparing quartz osl fading corrected k feldspar ir50 and pirir225 to identify reliable ages depositional ages based on quartz osl and feldspar pirir225 signals revealed deposition of ice marginal kame terraces and glaciofluvial foreland terraces during late to middle mis 6 in combination with results from previous studies we could reconstruct the valley evolution during the riss glaciation newly gained luminescence ages of the deglaciation in the easternmost alps coincide with osl dated deglaciation events in the western alps indicating that climatic change along the north side of the alps happened simultaneously

glacial history of the kuznetsky alatay mountains field investigations showed that the leeward slopes across the kuznetsky alatay mountains also the windward slopes in the tigertysh ridge are intensively eroded by glaciers and represent the classical type of alpine type landscape accumulative glacial landforms are developed in all types of glacial valleys study of five valleys the karatas the lower and the upper tayzhasu perekhodnya the right source of the small kazyr rivers showed that four stadial moraine complexes can be identified these moraines are very different by their morphology they indicate the change of glaciation from large ancient valley glaciers to modern small cirque and slope glaciers in this article the first data are assessed about evolution of glaciers and climate in the kuznetsky alatay mountains from the last glacial maximum of late pleistocene between 26 500 and 19 000 20 000 years bp to nowadays on the basis of studies of glacial landforms sedimentology and biostratigraphy in the glacier inventory complied in 1970s early 1980s 91 glaciers were recorded in the kuznetsky alatay however some were erroneously identified as glaciers the review of the current changes of modern glaciation of the kuznetsky alatay is made on the basis of repeated photographs and direct field measurements of 30 glaciers 18 out of the 30 studied glaciers melted away completely their area decreased from 1 4 to 0 5 0 3 km2 not all glaciers strongly degraded large cirque glaciers have not changed significantly over the past 110 years the area of perennial snowfields in the kuznetsky alatay mountains had reduced by 90 over the century the timberline has risen by about 50 m and is currently located at 1220 1200 m a s l

sudden and gradual compaction of shallow brittle porous rocks 1 porous brittle rocks fail in shear and compaction rate and state friction describes such failure on a planar surface while end cap failure describes the failure of a continuum both formalisms include coulomb failure in shear at low normal tractions rate and state friction includes slow compaction of gouge by normal traction when shearing is not occurring rate and state friction also represents slow compaction of porous sandstone end cap failure includes both grain crushing and shear micromechanically all these mechanisms involve exponential creep at stresses of a few gigapascals rate and state friction is modeled by tabular real contacts where shear and extrusion occur the observed compaction rate depends on the normal traction to a modest power of 27 for gouge and 10 for sandstone end cap failure involves grain cracking in the neighborhood of the grain grain contact its rate should depend on the normal traction raised to a power of 100 this strong rate dependence is not measurable in practice as a failure cascade commences once some grains crack materials with pointy contacts including unwelded tuff and regolith in the uppermost tens of meters that has repeatedly been damaged by strong seismic waves compact in this manner at dynamic stresses modestly above their ambient lithostatic stress this failure produces significant nonlinear attenuation of compressional p waves with sustained dynamic accelerations that are a modest fraction of the ambient acceleration of gravity

microscopic elasticity and rate and state friction evolution laws 1 rate and state friction formalism represents the dependence of macroscopic shear traction m on sliding velocity v and the history of the sliding surface in macroscopic terms m pn 0 a ln v vref b ln norm where pn is normal traction 0 is the coefficient of friction a b 0 01 are small dimensionless parameters vref is a reference velocity is the state variable that depends on history and norm represents the effect of changes in normal traction this representation does not consider microscopic elasticity and is inadequate over very small times the apparent value of a just after a small decrease in shear traction is a factor of a few larger than its traditional value of 0 01 changes of microscopic elastic strain energy may cause this effect microscopic elasticity affects friction after changes in normal traction shear traction does not change instantly after a sudden change in normal traction because time is required for real contact area to change a hybrid of the aging law where increases linearly with time during holds and the slip law behavior where the state variable does not change in the limit of zero sliding velocity is necessary slip law behavior dominates near steady state and also applies to sudden initial sliding where the state variable and porosity are far from steady state porosity increases from its initial value toward the steady state value over slip scaling with the critical displacementdc the ratio of dilatant to shear strain in low porosity material is a modest fraction of 1 and related to the construct of dilatancy angle in engineering

lithofacies types and vertical profile models an alternative approach to the description and environmental interpretation of glacial diamict and diamictite sequences abstract increased knowledge of modern glacial depositional environments has resulted in rapidly evolving classifications of glacial tills these are based to a large degree on theoretical considerations of likely depositional processes the classifications are sophisticated and more advanced than the establishment of simple field criteria whereby individual till facies can be identified in quaternary and pre quaternary successions this situation is compounded in many quaternary terrains by the continued description of tills in terms of laboratory derived analytical data only reflecting a traditional interest in stratigraphic correlation rather than reconstruction of depositional environment detailed sedimentological logging of lithofacies is rarely undertaken there is thus considerable confusion as to what is being described or sampled when analytical data are presented for many pleistocene tills the same remarks apply to pre pleistocene tillites a lithofacies code is presented here for the rapid description and visual appraisal of field sequences or drill cores containing unconsolidated diamicts or lithified diamictites the term till is not used as it has a strict genetic definition referring to direct aggregation and deposition by glacier ice use of a four part code in conjunction with codes already published for fluvial sediments allows fundamental field properties to be depicted independent of genetic terminology and provides a firm basis for subsequent environmental interpretation and analytical work the value of this approach is illustrated by comparing a representative suite of vertical profiles of diamict assemblages deposited by modern grounded glaciers with a classic late pleistocene glacigenic sequence at scarborough bluffs ontario

late holocene variation of the raigorodskogo glacier and climate change in the pamir alai central asia during the late holocene the raigorodskogo glacier in the pamir alai central asia expanded before 3215 after 1545 and at 310 cal years bp as dated by the 14c calibrated ages of wood samples from moraine deposits and terrace exposures the glacier expansions which were accompanied by increased melt water run off over the terrace surface were confined to the proglacial area the terrace deposits with intercalated buried soil layers provide evidence of two obvious warm periods when the glacier abruptly retreated during the late holocene shortly before 1545 cal years bp and again sometime before ca 500 cal years bp fallen juniperus turkestanica broken by moraine deposits suggests that the largest glacial expansion during the little ice age occurred 310 cal years bp the glacier expansion in the little ice age was on roughly the same scale as that which occurred in the cold period after 1545 cal years bp observational records of the glacier terminus and moraine positions indicate that recent glacier advances occurred in the years 1908 1911 sometime in 1911 1934 and in 1960 1977 these advances were small while the glacier recessions were larger in the 1900s with large recessions also sometime in 1911 1934 and in 1977 1998 the glacier recession rate of 27 m year in 1911 1934 was faster than the rates of 13 m year in 1977 1990 and 21 m year in 1990 1998 however the glacier recession rate has been accelerating recently particularly after 1990 this recession reflects recent climate warming in inland asia

high resolution mapping of glacial landforms in the north alpine foreland austria abstract in this study results from traditional field mapping were merged with precise elevation information from airborne lidar light detection and ranging surveys morphological and sedimentological data provide new results from the austrian eastern part of the salzach piedmont glacier during times of and shortly after the last glacial maximum lgm the variations in meltwater discharge had a major impact on the development of glacial landforms in areas with high meltwater supply erosional or debris reworking processes play a major role represented by drainage channels drumlins and kettled low relief hummocky moraine with low slope angles low discharge areas are associated with distinct depositional forms such as high relief end moraines up to 30 m and hummocky moraine averaging 20 m with high slope angles isolated conical kames may reach heights up to 45 m fluvial activity is supposed to rise towards the end of the glacial cycle causing high melting rates and comprehensive debris reworking the formation of terminal lakes and associated widespread inorganic lake clays are the last deposits within the study area before the salzach glacier completely receded to its main valley the survey of glacial landforms through the combination of field mapping and high resolution dem derived from airborne lidar missions gives precise information on transport and deposition during the last glacial cycle of the eastern salzach glacier piedmont lobe

nonlinear attenuation and rock damage during strong seismic ground motions strong seismic waves cause nonlinear behavior in the shallow subsurface in fractured rocks seismologists use low amplitude signals from small repeating earthquakes to measure s wave velocity decrease after strong motion the 2004 parkfield california earthquake provides examples of such velocity changes in fractured sandstone with an s wave velocity of 300 m s 1 this nonlinear behavior occurred around the wave number depth of the incident waves 30 m for the 10 s 1 dominant angular frequency on a velocity seismogram the low amplitude s wave velocity gradually recovered with the logarithm of time the attenuation of strong waves in general depends nonlinearly on their amplitude high dynamic stress triggered small very shallow earthquakes at sites including parkfield the theoretical frictional behavior of a fractured medium with heterogeneous prestress relates these phenomena failure occurs in the highly prestressed domains causing small earthquakes and opening mode cracks the energy to dilate the cracks dissipates a significant fraction of the incoming seismic energy the local high porosity domains close with the logarithm of time as expected from the aging law of rate and state friction increasing the s wave velocity the domain model indicates that nonlinear effects increase gradually over a range of dynamic coulomb stresses as observed and as included in the widely used masing rules the linker and dieterich 1992 relationship provides the maximum sustainable dynamic coefficient of friction needed to utilize the masing rules this parameter is the coefficient of friction at a laboratory normal traction plus a constant 0 15 times the logarithm of the ratio of field normal traction to the laboratory normal traction it is helpful to relate s wave velocity to starting frictional strength as coefficient of friction near the quarter wavelength depth determines nonlinear behavior then the dynamic coefficient of friction and equivalently the maximum sustainable acceleration at the dominant frequency depend weakly on s wave velocity for example the coefficient of friction at an angular frequency of 10 s 1 is less than 1 5 for rocks ranging from parkfield sandstone to intact granite

the little ice age in the canadian rockies abstract this paper reviews the evidence and history of glacier fluctuations during the little ice age lia in the canadian rockies episodes of synchronous glacier advance occurred in the 12th 13th early 18th and throughout the 19th centuries regional ice cover was probably greatest in the mid 19th century although in places the early 18th century advance was more extensive glaciers have lost over 25 of their area in the 20th century selective preservation of the glacier record furnishes an incomplete chronology of events through the 14th 17th centuries in contrast varve sequences provide continuous annually resolved records of sediments for at least the last millennium in some highly glacierized catchments such records have been used to infer glacier fluctuations evaluation of recent proxy climate reconstructions derived from tree rings provides independent evidence of climate fluctuations over the last millennium most regional glacier advances follow periods of reduced summer temperatures reconstructed from tree rings particularly ca 1190 1250 1280 1340 1690s and the 1800s reconstructed periods of higher precipitation at banff alberta since 1500 are 1515 1550 1585 1610 1660 1680 and the 1880s glacier advances in the early 1700s the late 1800s and in places the 1950 1970s reflect both increased precipitation and reduced summer temperatures negative glacier mass balances from 1976 to 1995 were caused by decreased winter balances the glacier fluctuation record does not contain a simple climate signal it is a complex response to several interacting factors that operate at different timescales evaluation of climate proxies over the last millennium indicates continuous variability at several superimposed timescales dominated by decade century patterns only the 19th century shows a long interval of sustained cold summers this suggests that simplistic concepts of climate over this period should be abandoned and replaced with more realistic records based on continuous proxy data series the use of the term lia should be restricted to describing a period of extended glacier cover rather than being used to define a period with specific climate conditions

the pleistocene end moraine fans controls on their sedimentation and location abstract this paper presents a model of end moraine sedimentation based on data from pleistocene ice sheet margins according to this model end moraines quite often constitute alluvial fans or coalesced fans formed at the ice margin by redeposition of supraglacial material three types of end moraine fan have been recognized those composed mainly of mass flow deposits type a equivalent to dry alluvial fan in nonglacial settings those containing both mass flow and waterlain sediments type b and those that contain mainly sorted waterlain material type c equivalent to wet alluvial fan in nonglacial settings for each type of fan several sedimentary subenvironments differentiated by distance from the ice front are identified the diagnostic processes on the end moraine fans are cohesive and cohesionless debris flows or grain flows types a and b or hyperconcentrated flows and sheetflows types b and c the type b fan seems to represent the most typical sequence in the end moraine zones but the type c fan is also quite common at the pleistocene ice sheet margins our studies also suggest that the terminal supraglacial drainage controls the type of end moraine fan sedimentary subenvironment moraine types a b c whereas subglacial hydrology and ice stream regime which determine the mobility of the ice front and larger scale conditions of sediment supply to the ice margin control the location and size of the end moraine fan

the last and penultimate glaciation in the north alpine foreland new stratigraphical and chronological data from the salzach glacier abstract the northern alpine foreland was repeatedly covered by massive piedmont glaciers during quaternary glacial maxima the salzach palaeoglacier lobe austria germany was the easternmost of a series of pleistocene piedmont glaciers entering the foreland through major alpine valleys it covered an area of more than 1000 km2 during at least four glacial maxima here we aim to bring more light into its history by analyzing multiple drill log data two major outcrops topographic data and absolute chronologies of sediments stratigraphic and lithofacies investigations are focused on proximal i e near the lobe axis and distal i e near terminal moraine deposits of the salzach glacier lobe the glacial carving into the miocene bedrock occurred during early glacial maxima and was rather uniform across the lobe with larger values only in the proximal parts of the glacier more than 100 m of accumulated sediments during later glacial maxima indicate a change in ice sheet dynamics and a characteristic sequence development which varies from proximal to distal lobe positions new luminescence ages suggest a depositional focus at the penultimate glacial period while the impact of the lgm was rather minor sediments of gravelly braided rivers dominate the proximal parts of the former lobe where meltwater discharge was generally high while sheetflood deposits dominate the distal near terminal lobe positions

rate and state dependent friction of intact rock and gouge the shear traction during frictional sliding depends on the instantaneous sliding strain rate e and on a state variable which represents the previous history of the sample a formulation of rate and state friction covers the continuum between gouge and intact rock as well as the behavior at high and low normal tractions a traditional formula for the instantaneous coefficient of friction is retained 0 a in e e 0 b in 0 where 0 is the steady state coefficient of friction at the reference strain rate e 0 and a and b are small constants the normalizing 0 for isothermal conditions is p n p 0 n where ap is the effective normal traction p 0 is a reference normal traction and n is an exponent the coefficient of friction of intact rock is approximately close bn in p p close where the coefficient of friction is close at the normal traction p close where essentially all the pore space is closed during steady state sliding the formulation provides an acceptable fit to the observed coefficient of friction of westerly granite at normal tractions up to 1500 mpa including steady sliding and intact rock failure

a rheologic model for wet crust applied to strike slip faults the strength and stability of crustal faults are not adequately addressed by the widely used two mechanism rheologic models of the crust based on byerlee s law and power law creep the models neglect the fluid assisted mechanisms of deformation that are important to strength of the crust and do not describe the variation in rate dependence of friction that governs the stability of fault slip several distinct mechanisms of frictional slip are defined on the basis of variations in frictional behavior and microfabric of simulated fault gouge in laboratory experiments state variable constitutive relations are used in a multiple mechanism formulation to describe the rate and temperature dependence of three friction mechanisms in wet quartz gouge at elevated temperatures this multimechanism description of friction is substituted for byerlee s law in the two mechanism models to generate a multimechanism rheologic model for the crust the multimechanism model is used to predict the rate and temperature dependence of crustal strength and the slip rate and depth temperature conditions over which each mechanism dominates application of the model to strike slip faults in the crust illustrates that the thickness of the actively shearing zone within faults is a critical parameter governing fault strength and stability the model predicts that frictional strength at midcrustal depths is significantly reduced relative to byerlee s law only for thick fault zones the reduction in strength is due to the operation of a strain rate sensitive friction mechanism involving combined cataclasis and solution transfer the rheologic model predicts that only very thin faults display the rate dependent characteristics necessary for initiation of seismic slip to any significant depth in the crust

real contacts and evolution laws for rate and state friction the well known formalism of rate and state dependent friction represents the transition between static and dynamic friction the instantaneous coefficient of friction is proportional to the logarithm of the sliding velocity v and the logarithm of a state variable whose inverse is a measure of the current amount of damage within a shearing gouge layer or on a sliding surface evolution equations that represent the change of the state variable with time include damage from sliding and healing the dieterich 1979 evolution law contains separate terms for the two effects the ruina 1983 law groups the two effects into one term proportional to v ln v in addition the state variable depends exponentially on porosity as exp f c where is the porosity at reference conditions and c is a dimensionless constant i obtain these relationships as well as relationships between friction law parameters and physical parameters by representing asperity contacts as rectangular deformable regions between two rigid sheets the creep rate within an asperity depends exponentially on the second invariant of the deviatoric stress in terms of asperity scale quantities the invariant includes normal traction and shear traction the derivations assume that contact stresses scale with macroscopic stresses this yields simple expressions analogous to those in rate and state friction the ruina 1983 evolution law in general and the decrease in compaction rate during a hold in a slider experiment in particular arise because a sudden decrease in sliding velocity implies that the shear traction and hence the invariant decrease the porosity state relationship arises when real stresses at contacts or the inverse real contact area depend linearly on the separation of the sheets and by analogy the porosity conversely the ruina 1983 evolution law is inapplicable when asperity scale stresses within a deforming material do not scale with macroscopic stresses

review of holocene glacial chronologies based on radiocarbon dating in tibet and its surrounding mountains a compilation of 53 14c ages on moraines constrains the holocene glacial history of tibet and the surrounding mountains several holocene glacial stages are identified the little ice age had three substages at 1 0 0 13 cal ka bp however the glacial advances may have occurred 200 600 a earlier in southern and eastern bordering mountains than in the northern bordering mountains the earlier glacial advance might have been driven by humid conditions in bordering areas of tibet most glacial advances in the neoglaciation occurred at 3 5 1 4 cal ka bp they can be identified in almost every mountain range an early holocene glacial advance occurred 9 4 8 8 cal ka bp in both central tibet and bordering mountains the timings of holocene glacial advances are synchronous with the cooling periods in the 18o record from ice cores and with the results of optically stimulated luminescence dating and cosmogenic exposure dating in tibet copyright 2008 john wiley sons ltd

jokulhlaup deposits in proglacial areas abstract this paper discusses the main causes and characteristics of jokulhlaup glacier burst floods and explores the extent to which they generate depositional landform and sediment assemblages that are distinct from those of normal braided river outwash type i outwash two main jokulhlaup outwash environments are identified type ii outwash produced by sudden drainage of ice dammed lakes and type iii associated with drainage during subglacial geothermal activity and distinguished by deposits resulting from high sediment concentrations and hyperconcentrated flows in fluid flows especially ones yielding type ii outwash the most common deposits are large scale expansion bars and locally eddy and pendant bars and mega ripples or dunes both forms normally composed of large scale gravel cobble cross bedding often capped by an imbricated boulder lag a type b2 lithofacies sequence the armour is absent only where runoff decreased too rapidly to allow surface winnowing other jokulhlaup facies include extensive boulder beds type c inverse normally graded cobble beds type ds ice proximal debris flow deposits and deformed bedding containing diamicton clasts types g and h and slack water sediments type a type iii outwash is dominated by massive homogeneous flood surge granules underlain by pre surge gravels and capped by post surge fluid bedforms reflecting deposition during both the rising and falling limbs of the flood hydrograph type e4 the paper demonstrates that jokulhlaups do generate distinctive assemblages of depositional landforms and sediments and concludes with a model of the dominant lithofacies sequences and associated landforms in proglacial environments subject to jokulhlaup drainage

depositional model in subglacial cavities killiney bay ireland interactions between sedimentation deformation and glacial dynamics subglacial meltwater drainage and sedimentary processes play a major role in ice sheet dynamic but there is a lack of study of subglacial environment because modern ice sheet beds remain inaccessible previous authors already intended to provide diagnostic criterion and recent investigations suggest that fluid pressure variations are a key factor in subglacial environment this paper investigated the late devensian sedimentary record in order to describe subglacial sedimentological facies associations and deformation features related to fluid overpressures we used an integrated approach based on stratigraphy sedimentology and deformations styles to demonstrate a subglacial depositional model the studied interval is composed of stratified gravel and sand interbedded with diamicton and boulder pavement deposited in depressions formed by irregularity of the upper surface of diamicton deformation structures include convolutes dykes and normal micro faulting dykes show different dip directions from vertical oblique to subhorizontal from which both directions of shortening and extension can be determined vertical dykes are formed under pure shear strain related to ice weight only oblique dykes imply both ice bed coupling and simple shear strain between ice and substrate induced by flowing ice related to progressively increasing meltwater drainage intensity horizontal dykes are formed when minimum strain is vertical and therefore the overpressure exceeds the weight of overburden they are associated with high meltwater drainage intensity and ice bed uncoupling and refer to hydrofracturing overall depositional and deformation sequence also illustrates the increasing intensity of meltwater drainage in small cavity as high energy channelised deposits and in large cavities where subaqueous fan are deposited under hydraulic jump conditions moreover large cavities represent lee side cavities formed by fast flowing ice over an obstacle hydrofracturing is likely to occur when a dense fluid potentially associated with catastrophic drainage of an upstream cavity enters the low pressure confined environment of a downstream cavity and is injected under pressure in the soft substrate the studied glacial sequence represents a regional pattern probably related to an allocyclic control on sedimentation linked to long term glacial dynamics rather than local depositional conditions based on these results we provided a synthetic model linking depositional and deformation processes during ice sheet growth and decay but also valid at different timescales from annual to seasonal scale

some remarks about a new last glacial record from the western salzach foreland glacier basin southern germany the amount of glacial advances into the alpine foreland during the pleistocene is still a matter of discussion the big four glaciations of the classical approach were originally derived from outwash sequences from glacial basins only very few long records and studies are known in the context of a geological mapping programme of the bavarian environment agency a research drilling through the salzach foreland glacier area was undertaken continuous coring reached the base of the glacial basin sequence 117 m below surface geological and geophysical logging pollen sampling and dating attempts of core material were conducted while age constraints for the lower part of the sequence are still uncertain the upper part can be ascribed to the last glacial cycle the interpretation of diamictons from the early part of the last glacial cycle is discussed a validation compared to other stratigraphic observations and interpretations from northern alpine quaternary records is presented

sea level during the penultimate interglacial period based on a submerged stalagmite from argentarola cave italy accurate constraints are presented for the absolute age duration and sea level for the highstand corresponding to marine isotope stage mis 7 1 our work is based on a stalagmite collected in a currently submerged cave from italy argentarola cave flooding of this coastal cave is clearly marked within the stalagmite by a thick marine overgrowth of serpulid worms precise uranium thorium u th ages measured by thermal ionization mass spectrometry suggest that the stalagmite growth varied in phase with climate during mis 7 2 and mis 6 the penultimate glacial period in addition the period of marine transgression is bracketed between 202 and 190 kyr bp defining a mis 7 1 duration of 11 2 kyr comparison with previous studies provides a new constraint on the sea level during mis 7 1 that has approximately remained between 318 and 39 m relative to present sea level the timing of the mis 7 1 highstand is in full agreement with the specmap chronology which contrasts with the growing body of evidence showing a significant phase difference for mis 5 5 a tempting conclusion is that second order sea level highstands such as mis 7 1 may be purely driven by astronomical changes in contrast with major terminations such as termination ii atmospheric co2 levels may partly explain this contrast since the two sea level transitions mis 7 2 7 1 and mis 6 5 5 are characterized by very different co2 rises 20 vs 100 ppm fl 2002 elsevier science b v all rights reserved

physical basis of evolution laws for rate and state friction the well known formalism of rate and state dependent friction represents the transition between starting friction and sliding friction it expresses the instantaneous coefficient of friction in macroscopic quantities as 0 a ln v v0 b ln norm where 0 is the first order coefficient of friction a and b are small 0 01 dimensionless constants v is sliding velocity v0 is a reference sliding velocity and the inverse of the state variable 1 represents damage the normalizing state variable norm p p0 b represents the effect of the normal traction p on stress concentrations where p0 is a constant with dimensions of pressure and b is another dimensionless constant evolution equations represent the combined effect of damage from sliding and healing on the state variable the ruina 1983 evolution equation implies that the state variable does not change no healing during holds when sliding is stopped it arises from exponential creep within gouge when the concentrated stress at asperities scales with the macroscopic quantities the parameter b a being positive is a necessary condition for a spring slider system becoming unstable microscopically this parameter represents the tendency of asperities accommodating shear creep to persist longer than asperities of compaction creep at high sliding velocities in the dieterich 1979 evolution law healing occurs when the sample is at rest it is a special case where creep that produces shear and creep that produces compaction occur at different microscopic locations at a subgrain scale it also applies qualitatively for compaction at a shear traction well below that needed for frictional sliding chemically it may apply when shear sliding occurs within weak microscopic regions of hydrated silica while compaction creep occurs within comparatively anhydrous grains

fluctuation of glaciers in the southeast russian altai and northwest mongolia mountains since the little ice age maximum the present state and dynamics since the maximum of the lia of the glaciers of southeast russian and north mongolian altai have been studied data were obtained from 15 areas of glaciation the research is based on multiyear in situ observations and analysis of aerial photos of mid 1960s and high resolution space imagery 553 modern glaciers with total area 313 4 km2 have been mapped and put down into catalogues including glaciated areas and glaciers that have not been studied before glacial complexes with united accumulation zone and flat summit glaciers in the center and valley glaciers on the sides are typical for the area of research the firn line level rises from 3200 3300 m in the west to 3600 3700 m in the east this tendency reflects the reduction of nourishment of the glaciers in this direction due to decrease of precipitation the largest valley glaciers exist on the northeastern leeward slopes as a result of two to threefold concentration of snow the last glacial advance in the maximum of lia according to dendrological data finished in the first half of the 19th century from the maximum of the lia the glaciation of the region lost about 51 ela average uplift was 89 m on the background of general trend of glacial retreat there were several periods of stabilization of glacial fronts the most distinct in mid 1960s in the last 50 years there were two warm and dry intervals 1972 1981 and 1992 2008 and three cool and moist intervals prior to 1972 during 1982 1994 and subsequent to 2009 it caused fluctuations of firn line altitude with about 300 m range and abrupt changes of glacial area maximal changes were observed between 1995 and 2008 when areas of the glaciers decreased with average rate 1 2 year determination of retreat of glacial snouts after the lia by geomorphic features is described by vi phase scheme

hummocky moraine sedimentary record of stagnant laurentide ice sheet lobes resting on soft beds abstract over large areas of the western interior plains of north america hummocky moraine hm formed at the margins of laurentide ice sheet lis lobes that flowed upslope against topographic highs current depositional models argue that hm was deposited supraglacially from stagnant debris rich ice disintegration moraine across southern alberta canada map and outcrop data show that hm is composed of fine grained till as much as 25 m thick containing rafts of soft glaciotectonized bedrock and sediment chaotic non oriented hm commonly passes downslope into weakly oriented hummocks washboard moraine that are transitional to drumlins in topographic lows the same subsurface stratigraphy and till facies is present throughout these landforms and others such as doughnut like rim ridges flat topped moraine plateaux and linear disintegration ridges are identified as belonging to subglacially deposited soft bed terrain this terrain is the record of ice lobes moving over deformation till derived from weakly lithified bentonite rich shale drumlins record continued active ice flow in topographic lows during deglaciation whereas hm was produced below the outer stagnant margins of ice lobes by gravitational loading pressing of remnant dead ice blocks into wet plastic till intervening zones of washboard moraine mark the former boundary of active and stagnant ice and show hybrid drumlins whose streamlined form has been altered by subglacial pressing humdrums below dead ice the presence of hummocky moraine over a very large area of interior north america provides additional support for glaciological models of a soft bedded laurentide ice sheet

holocene glacier fluctuations and climate changes in the southeastern part of the russian altai south siberia based on a radiocarbon chronology abstract this study investigates glacier dynamic and climatic variations in the southeastern part of the russian altai se altai during the last 7000 years recent glacier retreats and ice melting in moraines has led to exhumation of organic material allowing the possibility of radiocarbon dating we report here 57 new radiocarbon dates from wood remains buried by moraines and from proglacial forefields from peat layers and lacustrine sediments that cover moraines from dead trees at the upper tree limit and from rock glaciers on trough slopes from six glacial valleys in the north chuya range se altai such a numerous dataset for the vast but unified in neotectonic and climatic conditions area is presented for the first time the history of research in the altai together with 62 previously published radiocarbon ages mainly of fossil soils and peat layers in the foot of the ranges in se altai they form the basis for understanding the relative magnitudes and timing of the most important glacial and climatic events of se altai new data refute the traditional concept of the russian altai holocene glaciations as a consecutive retreat of the late wurm glaciers and argue their complete degradation at the head of trough valleys at least 7000 cal years bp moraine complexes of three holocene glacial stages are morphologically expressed in trough valleys of the north chuya range they correlate with three identified periods of glacial advances from 4900 to 4200 cal years bp akkem stage from 2300 to 1700 cal years bp historical stage and in the 13th 19th centuries little ice age lia or aktru stage the coincident extremes of lowering temperature and increasing precipitation during the akkem stage led to abrupt glacier advances and forming of the most remote moraine complexes downstream in the valleys following glacier advances had distinctly smaller magnitudes in addition to the radiocarbon data the time limits of the historical stage were defined more precisely using dendrochronological and archaeological data from scythian burials of pazyryk culture in se altai repeated forest regrowth in the presently glaciatiated area indicates significant retreat or even complete glacier degradation during interstage warming the decreases of glacier length in the following stages argues for intensification of aridity in the se altai during the second half of the holocene the thermal minimum in the middle of 19th century the greatest in the last millennium did not positively influence the mass balance of glaciers which also supports this conclusion

latest pleistocene and holocene glacier variations in the european alps in the alps climatic conditions reflected in glacier and rock glacier activity in the earliest holocene show a strong affinity to conditions in the latest pleistocene younger dryas glacier advances in the alps related to younger dryas cooling led to the deposition of egesen stadial moraines egesen stadial moraines can be divided into three or in some cases even more phases sub stadials moraines of the earliest and most extended advance the egesen maximum stabilized at 12 2 1 0 ka based on 10be exposure dating at the schonferwall tyrol austria and the julier pass outer moraine switzerland final stabilization of moraines at the end of the egesen stadial was at 11 3 0 9 ka as shown by 10be data from four sites across the alps from west to east the sites are piano del praiet northwestern italy grosser aletschgletscher central switzerland julier pass inner moraine eastern switzerland and val viola northeastern italy there is excellent agreement of the 10be ages from the four sites in the earliest holocene glaciers in the northernmost mountain ranges advanced at around 10 8 1 1 ka as shown by 10be data from the kartell site northern tyrol austria in more sheltered drier regions rock glacier activity dominated as shown for example at julier pass and larstig valley tyrol austria new 10be dates presented here for two rock glaciers in larstig valley indicate final stabilization no later than 10 5 0 8 ka based on this data we conclude the earliest holocene between 11 6 and about 10 5 ka was still strongly affected by the cold climatic conditions of the younger dryas and the preboreal oscillation with the intervening warming phase having had the effect of rapid downwasting of egesen glaciers at or slightly before 10 5 ka rapid shrinkage of glaciers to a size smaller than their late 20th century size reflects markedly warmer and possibly also drier climate between about 10 5 ka and 3 3 ka conditions in the alps were not conducive to significant glacier expansion except possibly during rare brief intervals past tree line data from kaunertal tyrol austria in concert with radiocarbon and dendrochronologically dated wood fragments found recently in the glacier forefields in both the swiss and austrian alps points to long periods during the holocene when glaciers were smaller than they were during the late 20th century equilibrium line altitudes ela were about 200 m higher than they are today and about 300 m higher in comparison to little ice age lia elas the larstig rock glacier site we dated with 10be is the type area for a postulated mid holocene cold period called the larstig oscillation presumed age about 7 0 ka our data point to final stabilization of those rock glaciers in the earliest holocene and not in the middle holocene the combined data indicate there was no time window in the middle holocene long enough for rock glaciers of the size and at the elevation of the larstig site to have formed during the short infrequent cold oscillations between 10 5 and 3 3 ka small glaciers less than several km2 may have advanced to close to their lia dimensions overall the cold periods were just too short for large glaciers to advance after 3 3 ka climate conditions became generally colder and warm periods were brief and less frequent large glaciers for example grosser aletschgletscher advanced markedly at 3 0 2 6 ka around 600 ad and during the lia glaciers in the alps attained their lia maximum extents in the 14th 17th and 19th centuries with most reaching their greatest lia extent in the final 1850 1860 ad advance

pollen based reconstructions of vegetation and climate changes during the late holocene in the southern altai mountains we here preset a result of high resolution pollen data of a lacustrine peat sediment core from yushenkule yskl peat southern altai mountains northwestern china we aim to reconstruct the palaeo

terrestrial ice streams a view from the lobe abstract the glacial landforms of minnesota are interpreted as the products of the lobate extensions of ice streams that issued from various ice sheds within the laurentide ice sheet low relief till plains trough shaped lowlands boulder pavements and streamlined forms make up the subglacial landsystem in minnesota that is interpreted as having been formed by streaming ice extremely uniform tills are created subglacially in a way that remains somewhat mysterious at the ice margins thrust moraines and hummocky stagnation topography are more common than single crested simple moraines if the ice lobes had repeated advances subglacial drainage features are obscure up ice but are present down ice in the form of tunnel valleys eskers spooner hills and associated ice marginal fans ice streaming may occur when basal shear stress is lowered as a result of high subglacial water pressure subglacial conditions that allow the retention of water will allow an ice lobe to extend far beyond the ice sheet as long as the ice shed also supports the advance by supplying adequate ice even with adequate ice flux however the advance of an ice lobe may be terminated at least temporarily if the subglacial water is drained through tunnel valleys or perhaps a permeable substrate thrust moraines and ice stagnation topography will result from sudden drainage although climate change is ultimately responsible for the accumulation of ice in the laurentide ice sheet the asynchronous advances and retreats of the ice lobes in the mid continent are strongly overprinted by the internal dynamics of individual ice streams as well as the interaction of ice sheds which obscure the climate signal

quaternary glaciation of muztag ata and kongur shan evidence for glacier response to rapid climate changes throughout the late glacial and holocene in westernmost tibet the glacial geology of two massifs muztag ata and kongur shan in western tibet was examined to help define the timing and style of glaciation in the semiarid regions of western tibet remote sensing geomorphic mapping and 10be terrestrial cosmogenic nuclide tcn surface exposure dating of boulders on the moraines and sediment in depth profiles show that glaciers advanced at least 12 times during at least the last two glacial cycles over this time the style of glaciation changed progressively from one that produced ice caps to one that produced less extensive and more deeply entrenched valley glaciers the timing of the two earliest glaciations is poorly defined but they likely occurred prior to the penultimate glacial cycle the karasu glacial stage and the early part of the last glacial cycle or during the penultimate glacial cycle the subaxh glacial stage in contrast the timing of later glacial advances the olimde glacial stage is relatively well defined showing quasiperiodical oscillations on millennial time scales 17 1 0 3 ka 13 7 0 5 ka 11 2 0 1 ka 10 2 0 3 ka 8 4 0 4 ka 6 7 0 2 ka 4 2 0 3 ka 3 3 0 6 ka 1 4 0 1 ka and a few hundred years before the present these data suggest that since the global last glacial maximum lgm the glaciers in western tibet likely responded to northern hemisphere climate oscillations rapid climate changes with minor influences from the south asian monsoon this study provides the first well defined glacial geologic evidence to suggest that glaciers in western tibet respond to rapid climate changes on millennial time scales throughout the late glacial and holocene

what does control earthquake ruptures and dynamic faulting a review of different competing mechanisms the fault weakening occurring during an earthquake and the temporal evolution of the traction on a seismogenic fault depend on several physical mechanisms potentially concurrent and interacting recent laboratory experiments and geological field observations of natural faults revealed the presence and sometime the coexistence of thermally activated processes such as thermal pressurization of pore fluids melting of gouge and rocks material property changes thermally induced chemical environment evolution elasto dynamic lubrication porosity and permeability evolution gouge fragmentation and wear etc in this paper by reviewing in a unifying sketch all possible chemico physical mechanisms that can affect the traction evolution we suggest how they can be incorporated in a realistic fault governing equation we will also show that simplified theoretical models that idealistically neglect these phenomena appear to be inadequate to describe as realistically as possible the details of breakdown process i e the stress release and the consequent high frequency seismic wave radiation quantitative estimates show that in most cases the incorporation of such nonlinear phenomena has significant often dramatic effects on the fault weakening and on the dynamic rupture propagation the range of variability of the value of some parameters the uncertainties in the relative weight of the various competing mechanisms and the difference in their characteristic length and time scales sometime indicate that the formulation of a realistic governing law still requires joint efforts from theoretical models laboratory experiments and field observations

a constitutive law for rate of earthquake production and its application to earthquake clustering seismicity is modeled as a sequence of earthquake nucleation events in which the distribution of initial conditions over the population of nucleation sources and stress ing history control the timing of earthquakes the model is implemented using solutions for nucleation of unstable fault slip on faults with experimentally derived rate and state dependent fault properties this yields a general state variable constitutive formulation for rate of earthquake production resulting from an applied stressing history to illustrate and test the model some characteristics of seismicity following a stress step have been explored it is proposed that various features of earthquake clustering arise from sensi tivity of nucleation times to the stress changes induced by prior earthquakes the model gives the characteristic omori aftershock decay law and interprets aftershock parameters in terms of stress change and stressing rate earthquake data appear to support a model prediction that aftershock duration defined as the time for rates to return to the back ground seismicity rate is proportional to mainshock recurrence time observed spatial and temporal clustering of earthquake pairs arises as a consequence of the spatial depen dence of stress changes of the first event of the pair and stress sensitive time dependent nucleation applications of the constitutive formulation are not restricted to the simple stress step models investigated here it may be applied to stressing histories of arbitrary complexity the apparent success at modeling clustering phenomena suggests the possibil ity of using the formulation to estimate short to intermediate term earthquake probabil ities following occurrence of other earthquakes and for inversion of temporal variations of earthquake rates for changes in driving stress

vegetation history of the penultimate glacial period marine isotope stage 6 at ioannina north west greece the vegetational history of the penultimate glacial period marine isotope stage mis 6 c 185 135 ka has remained relatively unexplored here we present a new record from the ioannina basin north west greece which constitutes the highest resolution terrestrial pollen record for this interval produced to date it shows that the vegetation history of mis 6 in this region can be divided into two parts an early period 185 155 ka with pronounced oscillations in tree population extent and a later period 155 135 ka with much smaller tree populations and subdued oscillations this pattern is analogous to the mis 3 mis 2 division during the last glacial in the same sequence although the early part of mis 6 had larger pinus populations and fewer temperate trees relative to the equivalent interval in mis 3 this implies cooler and wetter conditions which is somewhat counterintuitive given the high summer insolation during mis 6e but is in line with other palaeoclimatic evidence from the mediterranean comparison with north atlantic records suggests that despite the absence of pronounced iceberg discharges during mis 6 north atlantic millennial scale variability had a significant downstream impact on tree populations in north west greece copyright c 2011 john wiley sons ltd

glacier dynamics palaeohydrological changes and seismicity in southeastern altai russia and their influence on human occupation during the last 3000 years abstract the 3 ka chronology of climatically driven glacier fluctuations and upper tree limit variations dates of strong prehistoric earthquakes and fluvial system transformation are established for the se altai mountains of south siberia on the basis of radiocarbon and dendrochronological dating this time period of prosperity of the altai nomadic cultures is characterized by more arid and cold climate in comparison with the first half of the holocene during the last 3 ka glacier advances occurred at 2300 1700 cal bp historical stage and 13th 19th centuries aktru stage lia the recurrence interval of strong prehistoric earthquakes is estimated as 400 years the final draining of the holocene lake in the chuya intermountain depression took place about 1500 cal bp all these natural events together with political and social factors controlled the nomadic population their habitat and the patterns of evolution and migration of nomadic cultures within the se altai aridity intensification and cooling enhanced by anthropogenic impact brought deforestation of the eastern part of the chuya depression