terrigenous sediment supply in the scotia sea southern ocean response to late quaternary ice dynamics in patagonia and on the antarctic peninsula geochemical and mineralogical compositions of modern and late quaternary marine sediments from the scotia sea trace sources and transport paths of terrigenous sediment we discuss downcore variations of compositional data of two sediment cores from the northern and southern scotia sea that correlate with fluctuations in magnetic susceptibility sediments were derived from very different sources at both localities as revealed by contrasting clay mineral assemblages however a common feature is the input of more basic and undifferentiated crustal material with the potential of high magnetic susceptibility during glacial periods indicated by variable quartz feldspar ratios and major trace and rare earth elements terrigenous sediments mainly originate from nearby terrestrial sources or are introduced through interbasinal sediment transfer from adjacent seas the observed temporal compositional variations have to be attributed to changes in the relative detrital contributions from the diverse source areas ice mass extensions in southern patagonia on the antarctic peninsula and adjacent islands likely control the supply of glaciogenic detritus to the open ocean during times of glacial expansion diluting the sediment input of interbasinal origin current transport is mainly responsible for sediment dispersal to the pelagic scotia sea and may amplify the glaciological source signals during glacial climate periods because of a stronger wind forcing of the antarctic circumpolar current

crustal structure and earthquake focal depths beneath northeastern india and southern tibet summary we use broad band teleseismic data recorded at eight sites along a north south profile from karimganj 24 84 n 92 34 e south of the eastern shillong plateau to bomdilla 27 27 n 92 41 e in the eastern lesser himalaya to determine the seismic characteristics of the crust in northeastern india we also analyse data from the chinese digital seismic network station at lhasa and indepthii stations located on the southern tibetan plateau north of our profile to extend the seismic images of the crust further northwards although the northeastern indian stations and the tibetan stations do not lie along a linear profile across the himalaya the wellrecognized uniformity of the himalaya along strike make this comparison of the two profiles meaningful receiver functions calculated from these data show that the crust is thinnest 35 38 km beneath the shillong plateau receiver functions at cherrapunji on the southern edge of the shillong plateau have a strong azimuthal dependence those from northern backazimuth events show that the moho beneath the southernmost shillong plateau is at a depth of 38 km while receiver functions from southern backazimuth events indicate that the moho beneath the northernmost bengal basin is at a depth of 44 km receiver functions from sites on the brahmaputra valley demonstrate that the moho is deeper by 5 7 km than below the shillong plateau a result which agrees with the hypothesis that the shillong plateau is supported by shearing stress on two steep faults that cut through the crust further north of the eastern himalayan foredeep the moho dips gently northwards reaching a depth of 48 km beneath bomdilla in the lesser himalaya and 88 km below lhasa in tibet using the crustal velocity models obtained from receiver function inversions we redetermined focal depths of wellrecorded earthquakes across this part of the indo tibetan collision zone and find all of these to occur within the crust hence we find no evidence for bimodal depth distribution of earthquakes beneath this region of northeastern india

last deglacial sea surface temperature evolution in the southeast pacific compared to climate changes on the south american continent abstract applying the alkenone method we estimated sea surface temperatures ssts for the past 33 kyr in two marine sediment cores recovered from the continental slope off mid latitude chile the sst record shows an increase of 6 7 c from the last ice age lia to the holocene climatic optimum while the temperature contrast between lia and modern temperatures is only about 3 4 c the timing and magnitude of the last deglacial warming in the ocean correspond to those observed in south american continental records according to our sst record the existence of a younger dryas equivalent cooling in the southeast pacific is much more uncertain than for the continental climate changes a warming step of about 2 5 c observed between 8 and 7 5 cal kyr bp may have been linked to the early to mid holocene climatic transition 8 2 7 8 cal kyr bp also described from equatorial africa and antarctica in principal variations in the latitudinal position of the southern pacific westerlies are considered to be responsible for sst changes in the peru chile current off mid latitude chile

analysis of asymmetric multipathing with a generalization of the double beam method abstract an array method integrating source and receiver array beamforming is presented the method is a generalization of previous work kruger et al 1993 to independent variation of slowness and azimuth in both the source and the receiver array compared to the analysis capabilities of a single array the resolution is enhanced and asymmetric scattering configurations and multipathing can be studied the generalized double beam method dbm is applied to a data set consisting of nuclear explosions detonated in eastern kazakhstan and recorded at the yellowknife array in northern canada the multipathing found for pcp and pdp is interpreted in terms of lateral inhomogeneity in the lowermost mantle below severnaya zemlya indications for rayleigh to p wave scattering observed for the shagan river and degelen subsites of the former main test site of the ussr in eastern kazakhstan can be related to the structure in the vicinity of the two subsites

double beam analysis of anomalies in the core mantle boundary region seismic p waves from nuclear explosions at the kazakhstan test site in eastern kazakhstan kts observed at the yellowknife array yka canada are used to analyze the structure at the base of the mantle under severnaya zemlya arctic sea 18 events at the degelen subsite and 9 events at the shagan river subsite of kts are studied the simple waveforms and well controlled source parameters of nuclear explosions allow the use of the events as source arrays in addition to the usual receiver array configuration a new method double beamforming integrating both concepts is presented this method increases the resolution considerably for the degelen yka path one anomalous arrival 1 9 s before pcp slowness between p and pcp slowness is observed smaller anomalous arrivals are found 6 5 s degelen yka and 8 1 s before pcp shagan river yka these anomalous phases cannot be explained with standard earth models they are produced by reflections from an inhomogeneity in the lowermost mantle at 82 3n 107 5e under the area north of severnaya zemlya the strong variations between the wavefields for the two source receiver combinations indicate a heterogeneous structure in the lower mantle the anomaly found here is located close to an anomaly in the lowermost mantle beneath the nansen basin

the reconstruction and climatic implication of an independent palaeo ice cap within the andean rain shadow east of the former patagonian ice sheet santa cruz province argentina abstract this paper describes the reconstruction of the previously undocumented meseta cuadrada palaeo ice cap on south west meseta del lago buenos aires santa cruz province patagonia based on theoretical surface profiles the reconstruction of the meseta cuadrada palaeo ice cap indicates an ice mass covering at least 78 km2 with a total ice volume around 9 2 km3 the inferred equilibrium line altitude ela of the palaeo ice cap 2031 m asl represents a drop of 286 m compared to the ela of the current meseta cuadrada glacier 2317 m asl we explain this small change in ela with reference to the flat hypsometry of the palaeo ice cap and an enhanced aridity to the west of the patagonian andes caused by the existence of the last glacial maximum lgm patagonian ice sheet calculated annual accumulation values of ca 402 to 957 mm a at the ela of the meseta cuadrada palaeo ice cap derived by a degree day model ddm during the last local glacial maximum extent are low compared with estimations of the current accumulation at the ela of the remaining glacierized area of around 3789 mm a this strongly supports the existence of increased aridity and seasonality east of the patagonian andes during the last glacial maximum provided both maximum extents were synchronous

recent glaciation at high elevations on arsia mons mars implications for the formation and evolution of large tropical mountain glaciers 1 the 166 000 km2 fan shaped deposit at arsia mons contains three characteristic facies ridged knobby and smooth which are interpreted as the depositional remains of a cold based glacier that was present on the west northwestern flanks in the late amazonian period of mars history here we consider several high elevation graben on the western flank of arsia mons that are interpreted as the source regions for late stage cold based glaciers that overflowed graben walls advanced tens to hundreds of kilometers downslope experienced subsequent retreat and left distinctive depositional features similar to those associated with cold based glaciers in the dry valleys of antarctica these new observations provide additional support for a cold based glacial interpretation of the tharsis montes fan shaped deposits morphological evidence suggests that the largest of these graben was the primary source region for the most proximal smooth facies lobes at arsia mons and map plane ice sheet reconstructions are consistent with these observations this relationship has significant implications for the relative ages of the individual facies within the fan shaped deposit including the possibility that the smooth facies represents several distinct phases of glaciation the high relief and large elevation differences between the upslope and downslope walls of these graben appear to be critical factors for ice accumulation and the generation collection of rockfall within glacial accumulation zones we suggest that rockfall was the dominant process responsible for debris cover formation on the glaciers sourced within these graben and consider the implications for the entire arsia fan shaped deposit new crater count data suggest that the fill material in the large arsia graben formed within the past 100 myr model age of 65 ma taken together these new observations provide additional evidence for several periods of late amazonian climate change on mars within the past few 100 myr resulting in episodes of tropical mountain glaciation finally mola topography reveals that several lobate features interpreted as remnant debris covered ice from the most recent phase of glaciation are presently hundreds of meters thick suggesting the possibility of long term near surface water ice survival in the equatorial regions of mars

microstructural investigation of different nanopore types in marine continental transitional shales examples from the longtan formation in southern sichuan basin south china abstract variations in pore types the complexity of pore structures and strong heterogeneity complicate the thorough characterization of pore networks in marine continental shales in this study a novel 2d image processing method was proposed expounded and verified to clarify the geometrical morphologies formation mechanisms the size distributions proportions and the fractal characteristics of different types of pores in marine continental shales six types of pores inter particle intra particle organic matter om inter crystalline dissolved pores and micro fractures were classified and morphologically characterized the different types of shale pores had distinct relatively restricted morphologies formation mechanisms and size ranges nano and micron sized pores were controlled by om pores and micro fractures with the size ranging of 6 80 nm and 200 350 nm and 6 10 m respectively furthermore the fractal dimension characteristics were investigated on the basis of the 2d binary images and the results were verified by the fractal findings obtained from the n2 adsorption data these fracture dimension results demonstrated that the longtan shale pore structures had strong complexity and heterogeneity which was strongly and positively controlled by micro fractures inter crystalline and om pores in addition the total organic carbon content strongly and positively influences the development and anisotropy of the nanoscopic pores which were dominated by om pores while the clay minerals content has a minor effect on the total pore development and heterogeneity of shales but a significant effect on the dissolved pore development of shales whereas brittle minerals inhibit total pore development and heterogeneity of shales but contribute greatly to the development of the inter crystalline pores

the influence of tectonically derived relief and climate on the extent of the last glaciation east of the patagonian ice fields argentina chile abstract two large ice fields between 46 30 and 51 30 s cover the patagonian andes the north and south patagonian ice fields are separated by the transandine depth line at 47 45 to 48 15 s canal and rio baker run through this depression the two ice fields are generally considered relics of a continuous ice cap which covered the entire patagonian andes from 39 to 52 s and extended far into the eastern foreland of the andes this assumption is not correct for the 200 km long section of the andes between lago pueyrredon lago cochrane in chile 47 15 s and lago san martin lago o higgins in chile 48 45 s the lack of a continuous ice cap extending far into the east is caused by the transandine depth line playing a crucial role in the fluvial erosion and the glacial scouring of this tectonic zone this depression formed a river system e g rio baker rio bravo and rio mayer that drains towards the west reconstruction of the maximum glacial advance of the last ice age shows that the eastern outlet glaciers of the two ice fields between lago san martin and lago pueyrredon did not drain towards the east but rather followed the general gradient of the transandine depth line in this area the eastern flank of the andes between monte san lorenzo 3770 m and sa de sangra 2155 m supported valley glaciers which were independent of the expanding ice fields only a few valley glaciers advanced towards the patagonian meseta the terminal moraines of these glaciers were erroneously interpreted as the eastern edge of a continuous ice cap north of 47 30 s the outlet glaciers of the npi advanced 200 km during the lgm and the late glacial advances nearly reached to 71 w in contrast south of 49 s glacier expansion was comparatively less the lgm is situated only 85 115 km east of the present margins of the large outlet glaciers o higgins viedma and upsala and no late glacial advance reached 72 w these considerable differences of glacier expansion were influenced by the northward migration of the westerly precipitation belt during glacial cycles there is tentative evidence that the glaciers advanced three times in the period from 14 000 to 9 500 14c years bp

regional seismic event location with a sparse network application to eastern kazakhstan ussr three component data from a sparse three station seismic network in eastern kazakhstan surrounding the soviet nuclear test site have been analyzed to determine location estimates for regional events recorded by two or three stations included among these events are the september 1987 chemical explosions whose locations are known locations are calculated using arrival times of p and s phases and arrival azimuths from first p location uncertainties are estimated using a combination of a priori and a posteriori data uncertainties a layered p wave velocity model adapted from soviet deep seismic sounding surveys is employed for calculating travel times and two s models are tried location results for the chemical explosions are excellent even if only two stations are used absolute location errors are less than 10 km and estimated 90 confidence uncertainties are only a few kilometers the data are also adequate to determine correctly their depth i e focus at the surface the other regional events include numerous suspected mine blasts and two earthquakes from the tien shan the calculated locations of the latter events agree well with a teleseismic location for one of them falling within a belt of regular seismic activity nearly all of the presumed blasts can be associated with mapped mines and we have been able to identify the source areas for two sets of blasts in high resolution satellite images before and after photographs allow us to identify specific active mines our location estimates agree quite well with the observed active mines

geomorphic records along the general carrera chile buenos aires argentina glacial lake 46 48 s climate inferences and glacial rebound for the past 7 9 ka a reply we present geomorphic stratigraphic and chronological data acquired along the general carrera buenos aires gcba glacial lake located along a major morphological incision across the andes complementing relevant available data relative chronology of morpho climatic records together with 18 10be cosmic ray exposure cre ages allow constraining the timing of the patagonian ice sheet fluctuations since the lgm it improves the knowledge of the patagonia climate evolution in the 46 48 s area and allows documenting the uplift rates glacial rebound for the past 7 9 ka the first major ice lobe retreat occurred after 17 3 0 6 ka and has likely continued during the acr from 12 9 to 14 5 ka between 12 9 ka and 10 9 1 3 ka the general carrera lake evolved as an endorheic basin terraces t4 to t1 top to bottom have recorded abrupt lake regressions likely controlled by rainfall deficit they have accumulated in the time interval 17 3 12 3 ka maximum limits two glacial re advances at 10 9 1 3 and 7 9 1 1 ka marked a major climate change that led the lake to be ice dammed again a major transgression occurred subsequently that have flooded the previously accumulated terraces since then a pervasive regression has steered the gcba lake to the situation at present the highest shoreline of the transgression is used as a passive marker in order to quantify the magnitude and character of the regional deformation at 72 30 w the gcba lake area uplifted glacial rebound at a rate between 15 to 33 5 mm yr 1 during the past 7 9 1 1 ka we infer that the high uplift rate mainly originates from the north patagonian icefield ice loss

modelling the inception of the patagonian icesheet abstract we use a coupled climate icesheet model to simulate the inception and growth of the patagonian icesheet assuming a temperature lowering of 6 c and a uniform pressure gradient driving windfields an icesheet builds up with dimensions and morphology similar to that of the last glacial maximum analysis of the stages of growth reveals the following conclusions different sectors of the 1800 km long icesheet behave differently as a result of latitudinal variations in mass balance the fastest growth occurs in latitudes 45 52 s where the north and south patagonian icefields merge and expand to the coast within 1500 model years the most favourable topography for glacier initiation is the presence of high elevation basins low elevation summits in the mountain chain take a long time to become covered by ice because of the delay in ice spreading along the main mountain axis feedback between the increasing elevation of the icesheet and increasing mass balance on its windward flank enhances the rate of migration of the icesheet towards the precipitation source there is a lee side effect whereby easterly mountains are glaciated early on but are then starved of snow as ice builds up to the windward such locations should hold an empirical record of the early stages of a glacial cycle

an ice cap landsystem for palaeoglaciological reconstructions characterizing the younger dryas in western scotland abstract this paper reviews the contrasting behaviours of ice caps and icefields defines a generic landsystem model that can effectively discriminate between them and applies the model to landform sediment assemblages in an area of western scotland such a model is necessary since many palaeoenvironmental inferences from formerly glaciated terrains are based on the geometry extent and dynamics of reconstructed ice masses the validity of these glacier reconstructions is dependent on the accurate initial interpretation of relict landforms and sediments and their inter relationships a new landsystems model is presented here in which individual geological and geomorphological elements are checked against a set of eight theoretical diagnostic criteria that characterize the style of former glaciation when applied to a 1200 km 2 area of the western scottish highlands the landsystem tool predicts 1 an extensive younger dryas ice cap with a maximum surface elevation of 900 m above sea level implying colder or wetter conditions than previously thought and 2 the survival of an independent mountain icefield in part of the area during deglaciation glaciological theory proxy palaeoenvironmental data and established glacier climate topography relationships support these predictions thereby giving credibility to the landsystem methodology as a generic tool for palaeoglaciological reconstructions

late holocene glacier advances and related climate conditions in the hailuogou catchment gongga shan eastern tibetan plateau we present simulations for the late holocene glacier advances in the hailuogou catchment gongga shan in attempts to test the glacier sensitivity to climate changes and constrain the climate conditions that support these glacier advances we use a coupled mass balance and ice flow model parameterized using empirical glaciological and climatological data to simulate the glacier extents by fitting modeled glaciers to corresponding glacial landforms the glacier sensitivity test showed that in the hailuogou catchment glacier area expands increasingly quickly until 4 c cooling beyond which decreased expansion occurs up to at least 5 c cooling but the modeled glacier volume increases steadily up to 5 c with an approximate linear rate being 1 1 109 m3 0 5 c the temperatures were estimated to be 1 9 3 1 c 1 5 2 6 c and 1 0 2 2 c cooler than present for the respective guanjingtai hailuogou and little ice age lia maximum glacial stages considering a realistic precipitation field being 80 120 of

the last glacial maximum and deglaciation in southern south america abstract this paper models the extent of the patagonian icesheet during the last glacial maximum lgm and its subsequent deglaciation it constrains a new coupled icesheet climate numerical model with empirical evidence and simulates the icesheet at the lgm and at stages of deglaciation under lgm conditions an icesheet with a modelled volume slightly in excess of 500 000 km3 builds up along the andes there is a marked contrast between the maritime and continental flanks of the modelled icesheet with positive mass balance exceeding 2 m in the west and declining tenfold to the east modelled ice velocities commonly reach 400 m yr 1 in the western fjords the model is most sensitive to variations in temperature and good agreement between modelled ice extent and empirical evidence was achieved by applying a temperature decrease of 6 c relative to present day temperatures with constant wind fields over the model domain assuming a stepped start to deglaciation modelled ice volumes declined sharply contributing 1 2 m to global sea level 80 of it within 2000 years the empirical record suggests that such a stepped warming occurred around 17 500 17 150 cal yr ago

40ar 39ar and k ar chronology of pleistocene glaciations in patagonia during the pleistocene east of lago buenos aires argentina at 46 5 s at least 19 terminal moraines were deposited as piedmont glaciers from the patagonian ice cap advanced onto the semi arid high plains adjacent to the southern andes exceptional preservation of these deposits offers a rare opportunity to document ice cap fluctuations during the last 1 2 m y 4 0 ar 3 9 ar incremental heating and unspiked k ar experiments on four basaltic lava flows interbedded with the moraines provide a chronologic framework for the entire glacial sequence the 4 0 ar 3 9 ar isochron ages of three lavas that overlie till 90 km east of the cordillera at lago buenos aires and another 120 km from the andes along rio gallegos at 51 8 s that underlies till strongly suggest that the ice cap reached its greatest eastward extent ca 1100 ka at least six moraines were deposited within the 256 k y period bracketed by basaltic eruptions at 1016 10 ka and 760 14 ka similarly six younger more proximal moraines were deposited during an 651 k y period bracketed by an underlying 760 14 ka basalt and the 109 3 ka cerro volcan basalt flow that buried all six moraines coupled with in situ cosmogenic surface exposure ages of moraine boulders the 109 ka age of cerro volcan implies that moraines deposited during the penultimate local glaciation correspond to marine oxygen isotope stage 6 further westward toward lago buenos aires six additional moraines younger than the cerro volcan basalt flow occur surface exposure dating of boulders on these moraines combined with the 1 4 c age of overlying varved lacustrine sediment indicates deposition during the last glacial maximum lgm 23 16 ka although antarctic dust records signal an important patagonian glaciation at 60 40 ka moraines corresponding to marine oxygen isotope stage 4 are not preserved at lago buenos aires apparently these were overrun and obliterated by the younger ice advance at 23 ka notwithstanding the overall pattern of glaciation in patagonia is one of diminishing eastward extent of ice during successive glacial advances over the past 1 m y we hypothesize that tectonically driven uplift of the patagonian andes which began in the pliocene yet continued into the quaternary in part due to subduction of the chile rise spreading center during the past 2 m y maximized the ice accumulation area and ice extent by 1 1 ma subsequent deep glacial erosion has reduced the accumulation area resulting in less extensive glaciers over time

an advance of soler glacier north patagonian icefield at c ad 1222 1342 soler glacier is a temperate outlet glacier on the eastern side of the north patagonian icee eld in chile the glacier is currently receding from its little ice age maximum position attained sometime between ad 1600 and 1900 across the snout and foree eld of the glacier is an arcuate belt of well sorted granule gravel and coarse sand containing tree remains these sediments are interpreted as reworked glaciolacustrine material elevated to the glacier surface by thrusting and folding radiocarbon dating of samples of tree remains in these reworked glaciolacustrine sediments demonstrates that the glacier overrode this lake bed sometime between ad 904 and ad 1334 in situ tree remains plastered onto a large boulder in front of the glacier constrain this advance to the period between ad 1222 and ad 1342 this advance precedes by several hundred years the maximum little ice age extent of other north patagonian icee eld outlet glaciers suggesting either an early age for the onset of little ice age conditions or a previously unrecognized period of glacier advance prior to the advance at c ad 1222 to ad 1342 soler glacier was more recessed than at present cone rming the dynamic response of patagonian glaciers to holocene climatic e uctuations

crustal structure in eastern kazakh u s s r from teleseismic receiver functions broadband receiver functions determined from teleseismic p waveforms recorded at two seismic stations in eastern kazakh u s s r are inverted for the vertical velocity structure beneath the stations the detailed broadband receiver functions are obtained by stacking source equalized radial components of teleseismic p waveforms a time domain inversion of the radial receiver function is used to determine the structure assuming a crustal model parameterized by flat lying homogeneous layers the general features of the inversion results are a complex shallow crust velocities less than 6 km s in the upper crust a high velocity 6 9 7 5 km s lower crust and a moho that varies between 47 and 57 km depth these results compare favorably with a composite velocity model from deep seismic sounding data but show lower velocities in the upper crust and higher velocities in the lower crust the results indicate that the crust in this region is relatively uniform however the nature and depth of the moho changes significantly across the region the receiver function inversion structure for the kazakh sites is similar to a published receiver function structure for a site on the canadian shield

last glacial maximum climate in new zealand inferred from a modelled southern alps icefield abstract we present a simulation of the new zealand southern alps icefield at the last glacial maximum lgm c 30 000 20 000 calendar years ago ka in an attempt to constrain the climate of that period we use a 500 m resolution ice sheet model parameterised using empirical glaciological climatological and geological data specific to the model domain to simulate the entire southern alps icefield we find that an lgm cooling of at least 6 6 5 c is necessary to bring about valley glaciers that extend beyond the mountains however climate topography thresholds related to the elevation and hypsometry of individual catchments control the gradient of the rate of glacier expansion in the domain and in order to remain within geologically reconstructed lgm limits we find that the lgm cooling was most likely associated with a precipitation regime up to 25 drier than today wetter than present scenarios give rise to equilibrium line depressions and ice extents that are incompatible with empirical evidence these results perhaps indicate that either the westerly air masses affecting new zealand during the lgm were drier than today or that they were weaker or zonally displaced with respect to present

mapping moho depth variations in central italy from psmoho p delay times evidence of an e w transition in the adriatic moho at 42 n latitude 1 along the italian peninsula adjoin two crustal domains peri tyrrhenian and adriatic whose boundary is not univocal in central italy in this area we attempt to map the extent of the moho in the two terrains from variations of the travel time difference between the direct p wave and the p to s wave converted at the crust mantle boundary called psmoho we use teleseismic receiver functions computed at 38 broad band stations in this and previous studies and assigned each of the recording sites to the adriatic or peri tyrrhenian terrains based on station location geologic and geophysical data and interpretation and consistency of delays with the regional moho trend the results of the present study show that the psmoho arrival time varies from 2 3 to 4 1 s in the peri tyrrhenian domain and from 3 7 to 5 5 s in the adriatic domain as expected the lowest time difference is observed along the tyrrhenian coastline and the largest values are observed in the axial zone of the apennine chain a key new result of this study is a sharp e w boundary in the adriatic domain that separates a deeper moho north of about 42 n latitude from a shallower moho to the south this feature is constrained for a length of about 40 km by the observations available in this study the e w boundary requires a revision of prior mapping of the moho in central italy and supports previous hypotheses of lithosphere segmentation

efficient calculation of differential seismograms for lithospheric receiver functions summary a new technique for computing differential seismograms for crustal and upper mantle response to a teleseismic wave receiver functions is developed using the matrix formalism of kennett the work was motivated by the difficulty of modelling teleseismic sv waves and has also proven useful for modelling teleseismic p waves this efficient method for calculating differential seismograms is based on three separate methods for computing synthetic seismograms two of the synthetic seismogram methods save intermediate results then the remaining synthetic seismogram algorithm uses the stored results in an efficient calculation of a new synthetic seismogram for a perturbed velocity model these developments have led to a faster for a 30 layer model a 90 per cent reduction in computation time and more accurate linearized inversion scheme for the determination of velocity models using teleseismic waves

the receiver structure beneath mina nevada abstract receiver functions obtained from broadband teleseismic p waveforms recorded at seismic station mnv near mina nevada are inverted for the vertical shear wave velocity structure southeast of the station the time domain inversion procedure for vertically heterogeneous and laterally homogeneous one dimensional models includes smoothness constraints to minimize model roughness and a pseudo monte carlo approach to investigate the nonuniqueness of the solution models we also report on the potential effects of scattering on a receiver function inversion for a one dimensional velocity structure mnv receiver functions sample the walker belt crust and upper mantle beneath the soda spring valley and pilot mountains to the east and the garfield hills and excelsior mountains to the west of the station the preferred southeast solution models show a smooth positive gradient in the mid and lower crust with the top of the crust mantle boundary at 34 to 36 km depth reaching an upper mantle p velocity of 7 8 to 7 9 km sec 1 between 38 and 40 km these results suggest that the crust beneath mnv may be representative of a transition zone between typical basin and range province crust to the east and a thicker sierran block to the west of the station

anatomy of regional phases and source characterization of the soviet joint verification experiment underground nuclear explosion broadband data from the nrdc deployment of stations in kazakhstan at karkaralinsk kkl and bayanual bay are subjected to detailed waveform modeling to understand the nature of regional wave propagation and to determine the nature of the explosion time function and sources of low and high frequency tectonic release minor modification of a crustal model inferred from dss studies in the region is very effective in explaining the arrival times amplitudes and waveshapes of the pn and pmp arrivals at both stations the sh wave data are remarkable however for showing a large high frequency arrival after the expected and observed arrival of sms from the explosion source these secondary s arrivals imply a secondary source 1 to a few kilometers to the south of the shot point shear waves from this source dominate the seismic data at high frequency but are minor at low frequency where shear waves and surface waves from the inferred relaxation of the explosion cavity dominate the wave field the secondary s wave source is inferred to represent explosion driven faulting with no net moment significant overshoot in the rdp is required to match the p wave data it is found that von seggern blandford and haskell source functions are incapable of producing the observed overshoot however the mueller murphy source model is very effective in matching the clear overshoot effects seen in the p waves spall effects are also considered but appear to be minor and serve to require even more overshoot in the rdp the excitation and dispersion of rayleigh waves in the period band of 1 to 10 sec is seen to be a sensitive but nonunique function of both vs and vp in the upper crustal layer high poisson ratios in this layer are needed to explain the rayleigh waveform

pleistocene glacitectonic landforms and sediments around central magellan strait southernmost chile evidence for fast outlet glaciers with cold based margins abstract proglacial and subglacial glacitectonic sediments and landforms around the margins of the strait of magellan southernmost chile record the advance and retreat of outlet glaciers of the patagonian ice cap during the last glacial cycle the spatial arrangement of glacitectonic landforms in the area is inferred to have resulted from the advance of ice lobes with cold based margins and wet based interiors as the ice advanced subglacial basins were excavated beneath the glacier margins and the eroded material was pushed up into thrust moraines probably because frozen bed conditions formed a thermal dam against the free drainage of subglacial meltwater these ice marginal glacitectonic landforms were then overridden and streamlined into drumlins and flutes as thicker wet based ice passed over the area evidence for permafrost near sea level in patagonia during the last glaciation suggests that mean annual temperatures were several degrees lower than indicated by recent modelling studies the results indicate that future modelling experiments should incorporate more realistic basal boundary conditions particularly the presence of a weak deforming layer at the glacier bed to improve climatic reconstructions of southern south america

hypocenter constraint with regional seismic data a theoretical analysis for the natural resources defense council network in kazakhstan ussr source depth and epicenter determination remains a simple but key method for discrimination between earthquakes and nuclear explosions at near regional distances a variety of secondary body wave arrivals can be observed that may be useful for constraining source depth and epicenter in this paper we study the source location problem using regional arrival time and arrival azimuth data from a sparse seismic network a theoretical analysis of the source location inverse problem provides estimates of the stability and uncertainty of the solution for a particular suite of data as a function of epicenter and depth as well as evaluating the importance of each datum to the solution an empirical analysis with actual data complements the theoretical analysis our approach is applied to the three station natural resources defense council soviet academy of sciences network in kazakhstan the theoretical analysis indicates that reasonable constraint on depth and epicenter is possible whenever three distinct phases p pn pg pzp and pmp or equivalent s phases are observed at two or three stations our theoretical analysis for two station locations shows that the epicenter constraints are extremely poor for sources along the line passing through the two observing stations the use of arrival azimuth in two station locations results in improvement in epicenter constraint for events occurring in the vicinity of the line connecting the two stations but there is no significant improvement elsewhere an empirical analysis of data from two of the september 1987 chemical explosions and data from an explosion in an active mining area supports the theoretical analysis showing that two station locations both epicenter and depth are quite reliable furthermore the theoretical analysis also indicates that even with data from a single observing station satisfactory results are obtained if three or more phases plus arrival azimuth are available

glacial sediment landform associations and paleoclimate during the last glaciation strait of magellan chile abstract glacial sediments and landforms preserved beside the strait of magellan record repeated advances of an outlet of the patagonian icefield during and following the last glacial maximum lgm 25 000 14 000 14c yr b p ice marginal landform assemblages consist of thrust moraine complexes kame and kettle topography and lateral meltwater channels very similar to those found at the margins of modern subpolar glaciers taken together with other forms of paleoenvironmental evidence the landform assemblages show that during the lgm and late glacial time permafrost occurred near sea level in southernmost south america this finding implies that mean annual temperatures were 7 8 c lower than at present somewhat lower than those reconstructed by current glacier climatic models comparison with precipitation temperature relationships for modern glaciers suggests in addition that precipitation levels were lower than today reduced glacial age precipitation may have resulted from a precipitation shadow induced by the patagonian icefield an equatorward migration of the average position of westerly cyclonic storm tracks in the southern midlatitudes or both these factors

seismic velocity structure and event relocation in kazakhstan from secondary p phases abstract three component seismic data from a set of presumed explosions recorded by stations at bayanaul and karkaralinsk in kazakhstan were analyzed in order to model the crustal structure of the region and to examine the use of the arrival times of secondary p phases primarily pmp in regional event location polarization analysis aided in the identification of the secondary phases low pass filtered data 4 hz corner from the first 5 to 10 sec of 13 presumed explosions were modeled with the reflectivity method the two chemical explosions in 1987 provided a check on accuracy as their locations and origin times are accurately known a good fit to the arrival times and amplitudes in the first 5 sec of the p wave pn pg and pmp was obtained in the epicentral distance range of 100 to 300 km beyond 300 km the simple layered model was not adequate to model the pmp arrival the crustal p wave velocity model we derived has an upper crustal velocity increasing fairly rapidly from 4 5 km sec near the surface to 6 5 km sec at 15 km depth then increasing more slowly to 7 05 km sec at 50 km depth the observed difference in the arrival times of the phases pg pmp and pn in the range between 100 and 250 km distance required a relatively sharp transition at the crust mantle boundary the model is generally similar to previous estimates of p velocity structure in the region though with a gentler gradient in the upper crust and a steeper gradient in the lower crust we used the derived crustal model and the primary and secondary p wave arrival times to relocate events in the kazakhstan region inclusion of the phase pmp substantially decreases the focal depth uncertainty for many of the events all but one of the events analyzed are concluded to be surface explosions the identity of the remaining event is uncertain

precise relative location of 25 ton chemical explosions at balapan using ims stations wetest how well low magnitude m blg 1 8 to 2 6 25 ton chemical explosions at balapan kazakhstan can be located using ims stations and standard earth models relying on precisely determined relative arrival times of nearly similar regional and teleseismic waveforms three 1997 balapan explosions were recorded by a number of currently reporting and surrogate ims stations three regional stations and two teleseismic arrays yielded consistent waveforms appropriate for relative picking master event locations based on the ak135 model and ground truth information from the first shallowest and best recorded explosion fell under 1 km from known locations for depths constrained to that of the master event the resulting 90 confidence ellipses covered 12 13 km2and contained the true locations however results for depth constrained to true depth were slightly less satisfactory from predictions based on ground truth we found a pgcoda phase at makanchi kazakhstan to be misidentified and poorly modeled after accounting for this 90 ellipses shrank to 2 3 km2and true depth mislocation vectors became more consistent with confidence ellipse orientations these results suggest that a high level of precision could be provided by a tripartite array of calibration shots in cases where models are poorly known we hope that the successful relocation of these small balapan shots will support the role of calibration explosions in verification monitoring and special event studies including on site inspection

fast flowing outlet glaciers of the last glacial maximum patagonian icefield abstract glacial geomorphology around the northern patagonian icefield indicates that a number of fast flowing outlet glaciers the continuation of ice streams further upglacier drained the icefield during the last glacial maximum these topographically controlled fast flowing glaciers may have dictated the overall pattern of last glacial maximum ice discharge lowered the ice surface profile and forced the ice divide westward the influence of the fast flowing outlet glaciers on icefield behavior also helps to explain why the configuration of the patagonian icefield at the last glacial maximum is not accurately represented in existing numerical ice sheet models fast flowing outlet glaciers would have strongly influenced ice discharge patterns and therefore partially decoupled the icefield from climatically induced changes in thickness and extent

detection of seismic bedrock using radial receiver function the receiver function rf method has been widely applied to estimate velocity structures of earth s crust and mantle using teleseismic data in this study we perform a rf iterative deconvolution method to detect the depth variations of seismic bedrock in the taipei basin and chiayi area we use strong motion data recorded by five and seven stations in the taipei basin and chiayi area respectively the ps p times appear at about 0 235 0 93 s for the taipei basin and 1 015 1 685 s for the chiayi area the time differences imply gradually increases of the bedrock depth from southeast to northwest in the taipei basin and from east to west in the chiayi area our results show that the method can efficiently detect depth variations of seismic bedrock which are consistent with those from other geophysical observations as well

seismic evidence for an ancient rift beneath the cumberland plateau tennessee a detailed analysis of broadband teleseismic p waveforms broadband receiver functions developed from teleseismic p waveforms recorded on the midperiod passband of regional seismic test network station rscp are inverted for vertical velocity structure beneath the cumberland plateau tennessee the detailed broadband receiver functions are obtained by stacking source equalizd horizontal components of teleseismic p waveforms the resulting receiver functions are most sensitive to the shear velocity structure near the station a time domain inversion routine utilizes the radial receiver function to determine this structure assuming a crustal model parameterized by many thin flat lying homogeneous layers lateral changes in structure are identified by examining azimuthal variations in the vertical structure the results reveal significant rapid lateral changes in the midcrustal structure beneath the station that are interpreted in relation to the origin of the east continent gravity high located northeast of rscp the results from events arriving from the northeast show a high velocity midcrustal layer not present in results from the southeast azimuth this velocity structure can be shown to support the idea that this feature is part of a keweenawan rift system another interesting feature of the derived velocity models is the indication that the crust mantle boundary beneath the cumberland plateau is a thick probably laminated transition zonemore between the depths of 40 and 55 km a result consistent with interpretations of early refraction work in the area less

a review of topographic controls on moraine distribution ice marginal moraines are often used to reconstruct the dimensions of former ice masses which are then used as proxies for palaeoclimate this approach relies on the assumption that the distribution of moraines in the modern landscape is an accurate reflection of former ice margin positions during climatically controlled periods of ice margin stability however the validity of this assumption is open to question as a number of additional nonclimatic factors are known to influence moraine distribution this review considers the role played by topography in this process with specific focus on moraine formation preservation and ease of identification topoclimatic controls are not considered published literature indicates that the importance of topography in regulating moraine distribution varies spatially temporally and as a function of the ice mass type responsible for moraine deposition in particular in the case of ice sheets and ice caps 1000 km2 one potentially important topographic control on where in a landscape moraines are deposited is erosional feedback whereby subglacial erosion causes ice masses to become less extensive over successive glacial cycles for the marine terminating outlets of such ice masses fjord geometry also exerts a strong control on where moraines are deposited promoting their deposition in proximity to valley narrowings bends bifurcations where basins are shallow and or in the vicinity of topographic bumps moraines formed at the margins of ice sheets and ice caps are likely to be large and readily identifiable in the modern landscape in the case of icefields and valley glaciers 10 1000 km2 erosional feedback may well play some role in regulating where moraines are deposited but other factors including variations in accumulation area topography and the propensity for moraines to form at topographic pinning points are also likely to be important this is particularly relevant where land terminating glaciers extend into piedmont zones unconfined plains adjacent to mountain ranges where large and readily identifiable moraines can be deposited in the case of cirque glaciers 10 km2 erosional feedback is less important but factors such as topographic controls on the accumulation of redistributed snow and ice and the availability of surface debris regulate glacier dimensions and thereby determine where moraines are deposited in such cases moraines are likely to be small and particularly susceptible to post depositional modification sometimes making them difficult to identify in the modern landscape based on this review we suggest that despite often being difficult to identify quantify and mitigate topographic controls on moraine distribution should be explicitly considered when reconstructing the dimensions of palaeoglaciers and that moraines should be judiciously chosen before being used as indirect proxies for palaeoclimate i e palaeoclimatic inferences should only be drawn from moraines when topographic controls on moraine distribution are considered insignificant

glacial inception and quaternary mountain glaciations in fennoscandia abstract the aim of this review is twofold first the role of the fennoscandian mountains as a nucleation center for glacial inception is investigated the second objective is to review glacial erosion by mountain glaciers throughout the quaternary all available field data and several modelling experiments show that the fennoscandian mountains seeded the last glaciation since the mountains seem to be of key importance for ice sheet inception it is reasonable to assume a similar inception pattern throughout most of the major pleistocene glaciations this pattern also implies prolonged periods of glacial ice in the fennoscandian mountains during late cenozoic time mountain based glaciers thus have had a long time to act on their substratum resulting in a profound geomorphological impact

comparison of crustal velocity profiles determined by seismic refraction and teleseismic methods recently two diverse seismic techniques were applied independently to the study of the crustal structure of the cumberland plateau eastern tennessee one involved a reinterpretation of a refraction experiment performed in 1965 by the u s geological survey consisting of two 400 km long reversed refraction lines the other entailed the inversion of broadband teleseismic p waveforms recorded at a single three component broadband station rscp located at the intersection of the two refraction profiles a comparison of the two sets of velocity profiles revealed many similarities and some significant differences both sets of velocity models consist of three major crustal layers 1 an upper crust vp 6 1 6 4 km s down to about 17 km 2 a mid crust vp 6 7 6 9 km s between 17 and 40 km depth 3 a lower crust vp 7 2 7 4 km s from 40 to 51 km depth the refraction models have linear transition zones up to 11 km thick at the base of each layer whereas the teleseismic models have more irregular transition zones at the base of the mid and lower crust the differences in the results of these studies are attributed to the differing frequency bandwidths of the data sets the predominant sensitivity of the teleseismic data to shear velocities compared to compressional velocities for the refraction data and the different analysis procedures involved in each method nevertheless the similarities indicate that the teleseismic waveform method with broadband data is capable of retreiving comparable crustal information as the cumberland plateau refraction survey in addition it provides the kind of complementary information required to constrain the composition of the continental lower crust and uppermost mantle

glaciation of scotland during the younger dryas stadial a review considerable research effort in recent years has refined our knowledge of the landforms and sedimentary sequences generated by glaciers of the last cold episode in scotland the younger dryas and the chronology of their formation these recent advances have benefited from new technologies such as high resolution digital terrain models numerical ice sheet simulations and cosmic ray surface exposure dating this review presents a summary of recent younger dryas research in scotland particularly focusing on studies from the last two decades the findings of these investigations are compared with those of earlier workers and critically are appraised in terms of their relevance to five key aspects of younger dryas glaciation growth of the ice cap its geometry dynamics mode of decay and likely stadial climate minor differences aside the consensus view appears to favour a relatively thick but areally restricted central ice cap surrounded by satellite ice fields at its centre the ice cap was probably thickest during the first 500 years of the stadial after which it most likely thinned as the climate became increasingly arid outlet glaciers were dynamic only in marginal areas where they produced abundant moraine sequences during deglaciation but throughout much of the stadial central areas of the ice cap effected only minimal landscape modification deglaciation took place by active retreat under a rapidly warming climate overall the stadial was dominated by much colder and drier conditions than present and probably experi enced greater intra annual temperature ranges copyright 2009 john wiley sons ltd