internal characteristics of ice marginal sediments deduced from georadar profiling and sediment properties brogger peninsula svalbard abstract georadar and sedimentological data were acquired in the ny alesund area on brogger peninsula in order to study diamicton in frontal areas of vestre broggerbreen and midre lovenbreen parallel common offset georadar lines were acquired for information on thickness and layering and multioffset measurements served to deduce the subground velocity short permafrost cores

the interrelation of glaciotectonic and glaciodepositional processes within the glacial environment abstract in recent years it has been recognised that ice sediment coupling occurred beneath the quaternary ice sheets that advanced over the soft sediments of lowland areas this paper looks in detail at the effects of this coupling on the sediments which results in glaciotectonic deformation and also discusses the interaction of deformation and deposition within the subglacial environment two types of glaciotectonic deformation are discussed that are produced by the active movement of ice 1 proglacial tectonics at the margin which include compressive fold styles such as listric thrusts and faults and open folding 2 subglacial tectonics formed beneath the glacier which include fold styles resulting from simple shear and represent a soft rock purely dynamic shear zone styles of deformation associated with stagnant ice are also investigated we argue that glaciotectonic deformation is a common phenomenon and an integral part of geological record from continental ice sheets it is suggested that zones of deformation within the sediment are related to similar zones of strain in the ice sheet and complex deformation sequences are produced by the superimposition of these differing styles upon one another as the ice sheet advances and retreats it is also argued that subglacial deposition and deformation are related and that on soft beds underformed till is rare whilst deformed till is very common

abrupt change in mantle fabric across northern apennines detected using seismic anisotropy 1 we estimated sks splitting parameters for 18 earthquakes observed over 2 years on a dense linear seismometer array crossing the apennines orogen northern italy an abrupt within 30 km change in fast polarization occurs near the crest of the apennines southwest of the crest fast polarization parallels the apennines strike wnw ese rotating to ew orientation near the tyrrhenian sea northeast of the crest toward the po plain fast polarization is nne ssw roughly normal to the orogen s strike delay times 0 6 2 9s do not show a remarkable pattern splitting parameters beneath the apennines argue against anisotropy restricted to the crust and suggest that the mantle region deformed by apennines slab rollback is spatially limited we hypothesize that the rollback process has been uneven evolving to a contortion of the northern edge of the apennines slab and perhaps incipient detachment lithospheric anisotropy beneath the po plain may also be significant

sequence stratigraphy in a marine moraine at the head of hardangerfjorden western norway evidence for a high frequency relative sea level cycle abstract the depositional architecture and stratigraphy of the haereid moraine a sedimentary ridge ca 1 5 km long and up to 113 m in height at the head of hardangerfjorden west norway have been reconstructed in a high resolution sequence stratigraphic framework information from ground penetrating radar gpr profiles outcrop sections and borehole data have been used in the analysis the basal forced regressive deposits comprise relicts of a gilbert type delta that commenced its development at the front of a grounded glacier on the seaward distal side of the ridge there is a major channel fill mouth bar complex covering large parts of the delta s former frontal slope and prodelta zone the complex occurs in the seaward lengthening of a fluvially incised channel and is interpreted as a lowstand to early transgressive succession of fluvial and fluvial estuarine facies the channel fill mouth bar complex and the dissected delta top have been planed off through transgressive ravinement and the delta top is overlain by an upvalley thinning sedimentary wedge 3 8 m thick and with a general landward onlapping and propagating internal bedform geometry this wedge is thought to be composed mainly of transgressive marine estuary mouth barrier facies on the landward proximal side of the ridge the transgressive deposits include a retrograding landward dipping foreset interpreted as relicts of a flood tidal delta overlain by possible washover fan deposits these deposits are again conformably overlain by laminated clay interpreted as the remains of a highstand mud drape the depositional sequence delineated in this study up to 20 m thick and comprising deposits of a lowstand wedge a transgressive and a highstand systems tract developed in response to a relative sea level rsl rise of 12 15 m this rsl rise which interrupted the general rsl fall following the deglaciation is correlated with the younger dryas transgression a regionally recorded sea level event the highstand mud drape was deposited as the rising rsl ultimately led to drowning of the moraine the highstand and transgressive deposits are erosively truncated by a thin gravelly lag deposited during final emergence in the early holocene

complex kame belt morphology stratigraphy and architecture the development of glacier karst at the margins of melting ice sheets produces complex glaciofluvial sediment landform assemblages that provide information on ice sheet downwasting processes we present the first combined geomorphological sedimentological and geophysical investigation of the brampton kame belt an important glaciofluvial depositional zone at the centre of the last british irish ice sheet ground penetrating radar gpr data allow the broad scale internal architecture of ridges eskers and flat topped hills ice walled lake plains to be determined at four sites in combination with sediment exposures these provide information on lateral and vertical variations in accretion styles depositional boundaries and grain size changes building on existing work on the subject we propose a refined model for the formation of ice walled lake plains resulting from the evolution and collapse of major drainage axes into lakes as stable glacier karst develops during deglaciation the internal structure of esker ridges demonstrates variations in sedimentation that can be linked to differences in ridge morphologies across the kame belt this includes low energy flow conditions and multiple accretion phases identified within large s n oriented esker ridges and fluctuating water pressures hyperconcentrated flows and significant deformation within a fragmented sw ne oriented esker ridge in combination with updated geomorphological mapping this work allows us to identify two main styles of drainage within the kame belt 1 major drainage axes aligned broadly s n that extend through the entire kame belt and collapsed into a chain of icewalled lakes and 2 a series of smaller fragmented sw ne aligned esker ridges that represent ice marginal drainage as the ice sheet receded south eastwards up the vale of eden our study demonstrates the importance of integrated geomorphological sedimentological and geophysical investigations in order to understand complex and polyphase glaciofluvial sediment landform assemblages

architecture and sedimentation of outwash fans in front of the mýrdalsjokull ice cap iceland in this study we introduce the architecture and style of sedimentation of two outwash fans in front of the myrdalsjokull ice cap central south iceland that broaden different types of ice marginal sedimentation at kotlujokull a southeastern outlet of the ice cap fan formation was monitored from the late 1970s to 2002 thus the style of sedimentation is well understood and the relationship to the depositional architecture easily established in front of slettjokull a northern lobate extension of the ice cap a fan from the 10th century ad is capped by neoglacial till sheets at both sites the fan surfaces were reconstructed in three dimensions ground penetrating radar gpr provided the thickness and internal structure of sediment bodies geological exposures and excavations were used for detailed sedimentological documentation of the outwash deposits in proximal to distal transects the outwash deposits at both kotlujokull and slettjokull are considered to be alluvial fans of the hochsander type i e supraglacially fed as they show all the architectural characteristics of alluvial fans with a semiconical shape a restricted radial length of ca 0 5 1 5 km a plano convex cross profile and a slope gradient ranging between 1 and 5 fan deposits are dominated by planar or low angle cross bedded sand facies interbedded with thin laminae of fine gravel occasionally draped by mud sedimentation occurs during upper flow regime sheetflows associated with antidune migration within an aggrading shallow braided stream network hochsanders are intimately linked to advancing or stationary glaciers with steep ice cored frontal slopes that favor supraglacial over subglacial drainage most important hochsander fans lack any proximal to distal transition in the grain size distribution sediment facies or facies associations because much classification of glacial outwash sediments is based on proximal to distal distinctions it is crucial to consider the depositional model for hochsanders this study also indicates a strong dependence between the altitudes of the buried fan surface and the present day terrain in the forefield of slettjokull illustrating that subsequent to fan formation subglacial landforms merely mask many of the pre existing morphological features less

ground penetrating radar and its use in sedimentology principles problems and progress abstract ground penetrating radar gpr also referred to as ground probing radar surface penetrating radar subsurface radar georadar or impulse radar is a noninvasive geophysical technique that detects electrical discontinuities in the shallow subsurface

shear wave polarization anisotropy and subduction induced flow in the mantle wedge of northeastern japan abstract shear wave polarization anisotropy in the central part of northeastern ne japan was investigated we analyzed s phases of 293 intermediate depth earthquakes recorded at 77 stations and obtained 1286 splitting parameters the obtained results show the systematic variation in splitting parameters across the arc the leading shear wave polarization directions fast direction obtained at stations in the western side of the study area are oriented nearly e w which is sub parallel to the direction of relative plate motion between the pacific plate and the north american okhotsk plate in contrast fast directions obtained at stations in the eastern side of the study area are oriented approximately n s stations in the western side have a larger average delay time compared to those in the eastern side these variations suggest that the nature of anisotropy is quite different between the eastern and the western sides both experimental studies on the deformation of olivine and numerical simulations of plate driven flow predict that the lattice preferred orientation of olivine causes the fast direction sub parallel to the flow direction for the conditions in the mantle wedge of ne japan we thus infer that the lattice preferred orientation of olivine generated by flow induced strain is the most likely candidate for anisotropy that produces splitting with e w fast direction three possible causes of anisotropy in the eastern side are considered deformation of water rich olivine in the mantle wedge trench parallel flow in the mantle wedge due to along strike dip variations in the slab and anisotropy in the crust and the slab we could not however determine which causes are dominant further systematic study is required to reveal the cause of anisotropy in the eastern side

debris transport in a temperate valley glacier haut glacier d arolla valais switzerland hambrey m j goodsell becky glasser n f 2005 debris transport in a temperate valley glacier haut glacier d arolla valais switzerland journal of glaciology 51 172 pp 139 146

gpr in sediments advice on data collection basic processing and interpretation a good practice guide within sedimentological studies ground penetrating radar gpr is being used with increasing frequency because it yields images of the shallow subsurface that cannot be achieved by any other non destructive method the purpose of this paper is to provide an introduction to the collection processing and interpretation of gpr data so that future sedimentary studies can be improved with gpr equipment now being lightweight robust and portable proper data collection and survey design methods need to be followed in order to acquire high resolution subsurface digital data various factors are discussed including reflection profiling velocity soundings test surveys topography logistics data quality and extreme environments basic data processing and visualization are then reviewed followed by a discussion on gpr interpretation strategies including a background to radar stratigraphy for the sedimentary geologist or geomorphologist gpr offers unique data of the shallow subsurface including stratigraphy geometry architecture and structure

morphology and gpr stratigraphy of a frontal part of an end moraine of the laurentide ice sheet paris moraine near guelph on canada abstract during deglaciation the laurentide ice sheet developed lobate ice termini in the great lakes area where the lobes remained quasi stationary for considerable time and sediment was supplied by the glacier end moraines fronted by outwash plains were formed one of the best examples in southern ontario is the paris moraine formed by the lake ontario lobe this study is a detailed examination of the morphology transverse and longitudinal of part of the paris moraine near guelph ontario and an analysis of the stratigraphy as derived from borehole information and ground penetrating radar gpr surveys parts of the northwestern frontal zone of the moraine are characterized by c 30 m high semi isolated hills composed in great part by aprons fans of debris flow and waterlaid sediments to the southeast these hills are backed by moat like depressions similar to those formed by ice push generating hill hole morphology the ice push effect is corroborated by evidence of folding and dislocation in the gpr profiles farther southeastward still the main body of the end moraine is characterized by hummocky topography typical of differential melting of sediment charged stagnant ice

hints on the deformation penetration induced by subductions and collision processes seismic anisotropy beneath the adria region central mediterranean adria is a small region surrounded by three mountain belts the alps the apennines and the dinarides built up by long evolution of subduction and collisional systems we present 253 shear wave splitting measurements obtained by studying more than 100 teleseismic events for 12 stations sks splitting measurements show 3 d complexity and quite strong upper mantle deformation we carefully analyzed results in terms of back azimuthal coverage and interpret measurements as related to adria rotation and to subductions evolution in the northern part of adria the anisotropy pattern follows the arcuate shape of the alps the same pattern parallel to the mountains occurs along the apennines but fast directions show a sudden change in the adria foreland this lateral variation has been analyzed to isolate a distinct adria mantle anisotropic pattern which is identified as ne sw fast direction along the western microplate boundary and as n s fast direction at trieste this pattern might be induced by drag effect of the counterclockwise rotation of adria lithosphere that behaves as an independent microplate as identified by gps data our measurements suggest that the geodynamic process that generated the alps is more efficient deforming a larger volume of mantle than its apennine counterpart moreover the mantle circulation we hypothesize looking at the regional scale patterns of anisotropy requires the existence of an escape route beneath the alps apennines transition through which the mantle flows and feed circulation in the tyrrhenian mantle system as suggested by previous geodynamic models and as seen by some tomographic studies

evolution of subducting mantle lithosphere at a continental plate boundary although it is apparent that at continental convergence mantle lithosphere can be accommodated by a subduction like style of deformation it is not clear how this process evolves and how it is different from classical plate subduction using numerical models of the crust mantle system these issues are considered for the case of a simplified continent continent plate collision the results suggest that subducting mantle lithosphere is prone to detach resulting in a reversal of subduction polarity alternatively it may undergo symmetric plate consumption with steepening and possible roll over polarity reversal the style of post collisional subduction is largely controlled by the strength e g dependent on temperature assumed rheology of the mantle lithosphere

a review of the occurrence form and origin of c bearing species in the khibiny alkaline igneous complex kola peninsula nw russia abstract the khibiny complex hosts a wide variety of carbon bearing species that include both oxidized and reduced varieties oxidised varieties include carbonate minerals especially in the carbonatite complex at the eastern end of the pluton and na carbonate phases reduced varieties include abiogenic hydrocarbon gases particularly methane and ethane dispersed bitumens solid organic substances and graphite the majority of the carbon in the khibiny complex is hosted in either the carbonatite complex or within the so called central arch the central arch is a ring shaped structure which separates khibinites coarse grained eudialite bearing nepheline syenites in the outer part of the complex from lyavochorrites medium grained nepheline syenites and foyaites in the inner part the central arch is petrologically diverse and hosts the major ree enriched apatite nepheline deposits for which the complex is best known it also hosts zones with elevated hydrocarbon dominantly methane gas content and zones of hydrothermally deposited na carbonate mineralisation the hydrocarbon gases are most likely the product of a series of post magmatic abiogenic reactions it is likely that the concentration of apatite nepheline deposits hydrocarbon gases and na carbonate mineralisation is a function of long lived fluid percolation through the central arch fluid migration was facilitated by stress release during cooling and uplift of the khibiny complex as a result carbon with a mantle signature was concentrated into a narrow ring shaped zone

the formation of sawtooth moraine ridges in bodalen western norway abstract the forefield of the bodalsbreen glacier western norway exhibits a prominent set of end moraines the outermost one deposited at the little ice age lia maximum a d 1755 is smooth continuous and arcuate thus reflecting an even ice front in contrast subsequently formed moraines deposited a d 1767 1930 show a striking sawtooth morphology in an attempt to elucidate the formation processes responsible for this complex landform assemblage we have employed several methods of investigation including geomorphological mapping sedimentological studies and ground penetrating radar gpr in general the detailed formation processes of all moraines include bulldozing and thrusting furthermore the sediment composition and structure are similar for all the moraines containing recycled diamicton the remaining major factor influencing the moraine morphology thus seems to be the shape of the glacier front due to the distinctive geometry of the bodalen valley the former glacier underwent strong changes of its transverse stress field in the part where the valley was wider splaying radial crevasses developed further downvalley where the valley again narrowed these crevasses were closed as previous studies have concluded the change in valley morphology to a large extent explains the distinct morphology of the bodalen valley moraines this notion is further corroborated by studying sawtooth or sawtooth like moraines elsewhere where valley geometry also seems to have been a major contributing factor for moraine morphology

trench parallel flow beneath the nazca plate from seismic anisotropy shear wave splitting of s and sks phases reveals the anisotropy and strain field of the mantle beneath the subducting nazca plate cocos plate and the caribbean region these observations can be used to test models of mantle flow two dimensional entrained mantle flow beneath the subducting nazca slab is not consistent with the data rather there is evidence for horizontal trench parallel flow in the mantle beneath the nazca plate along much of the andean subduction zone trench parallel flow is attributale utable to retrograde motion of the slab the decoupling of the slab and underlying mantle and a partial barrier to flow at depth resulting in lateral mantle flow beneath the slab such flow facilitates the transfer of material from the shrinking mantle reservoir beneath the pacific basin to the growing mantle reservoir beneath the atlantic basin trenchparallel flow may explain the eastward motions of the caribbean and scotia sea plates the anomalously shallow bathymetry of the eastern nazca plate the long wavelength geoid high over western south america and it may contribute to the high elevation and intense deformation of the central andes

seismic anisotropy reveals the long route of the slab through the western central mediterranean mantle abstract in the south eastern corner of the tyrrhenian basin in the central mediterranean sea a tight alignment of earthquakes along a well defined benioff zone marks one of the narrowest active trenches worldwide where one of the last fragment of the former tethys ocean is consumed seismic tomography furnishes snapshot images of the present day position of this slab and seismic anisotropy allows to reconstruct the past kinematics of the subduction process using seismic anisotropy fast directions as a proxy for the present and past mantle flow we look backward for the seismic traces of the slab motion through the western central mediterranean mantle from the starting locus of subduction toward its present day position the result of combining independent data sets provides a coherent pattern of anisotropy that illustrates an example of slab rollback from its initiation point to its present day position

lateral moraines of glacier de tsidjiore nouve form development and implications the relationship between supraglacial lateral moraines and lateral dump moraines at arolla switzerland is discussed a detailed study of the lateral moraines of glacier de tsidjiore nouve reveals their complex form as superimposed and nested ridges and the current mode of development possibly related to the passage of a kinematic wave sedimentological analysis indicates that much of the constituent debris is of supraglacial origin it is transported either directly from the base of slopes flanking the pigne d arolla ice fall or via englacial septa comprising marginal sediment incorporated in the accumulation zone a calculation of the volume of debris in the lateral moraines suggests that glacier de tsidjiore nouve has recently been more active in transporting and depositing supraglacial debris than in glacial erosion sensu stricto

mantle flow at a slab edge seismic anisotropy in the kamchatka region the junction of the aleutian island and the kamchatka peninsula defines a sharp turn in the boundary of the pacific and north american plates terminating the subduction zones of the northwest pacific the regional pattern of shear wave birefringence near the junction indicates that trench parallel strain follows the seismogenic benioff zone but rotates to trench normal beyond the slab edge asthenospheric mantle is inferred to flow around and beneath the disrupted slab edge and may influence the shallowing dip of the benioff zone at the aleutian junction

the genesis and significance of hummocky moraine evidence from the isle of skye scotland abstract the range of genetic and climatic interpretations of scottish hummocky moraine is reviewed and new data are presented from the isle of skye western scotland which are used as the basis of a genetic classification hummocky moraine on skye is shown to consist of three principal sediment landform associations 1 recessional moraines 2 chaotic ice stagnation moraines and 3 drumlins and fluted moraines the recessional moraines consist of transverse moraine ridges and chains of mounds and were formed by a combination of glaciotectonics and debris accumulation at active ice margins second chaotic moraines consist of randomly distributed hummocks mounds and rim ridges and record deposition in contact with inactive ice finally drumlins and fluted moraines are longitudinally oriented subglacial bedforms formed by a combination of lodgement and sediment deformation individual occurrences of hummocky moraine may comprise one two or all of these associations the detailed study and differentiation of scottish hummocky moraine provides a valuable source of information on former glacier dynamics and landscape change

the sedimentary signature of ice contact sedimentation and deformation at macro and micro scale a case study from nw scotland abstract studies on the genesis of subaerial debris flows and associated deposits are relatively rare in the literature especially in an ice marginal context of moraine formation the present contribution reports results from both the macro and micro scales of a subaerial depositional setting in order to contribute to closing this gap at the macroscale alternating loose stratified clast and matrix supported diamicts and finely laminated sand units indicate deposition of debris flows and fluvial units in a subaerial ice marginal setting that were stacked up to form a terrestrial ice contact fan macroscale and micromorphological analyses show that this fan displays evidence of a three phased formation a overriding and glaciotectonisation of pre existing sediments followed by retreat and burial of this core by b ice contact fan deposition dominated by water rich fluvial deposition with relatively little debris flow activity and c a switch to a gravitational sedimentation style with dominantly debris flow deposition and fewer and thinner fluvial units thin sections of both the diamict and laminated sand units show evidence of deposition of a mud and fine sand rich slurry being expelled from the tops of advancing mass flows water rich fine grained slurries appear to have been progressively overridden and deformed in response to ductile shear occurring at the base of individual flows liquefaction and remobilisation of sand within laminated deposits occurred during such basal shear events resulting in the injection of liquefied sediments into variably deformed laminated sands and clays deformation is more likely to have taken place through internal movement of the sediment due to changing porewater conditions and loading upon emplacement our approach confirms previous results that highlight the possibilities of increasing the accuracy of sedimentological investigations through combined sedimentological analyses at varying scales

seismic anisotropy beneath the northern apennines italy and its tectonic implications we examined shear wave splitting in sks and s phases from 22 teleseisms at 10 temporary stations on a transect across the northern apenninic arc the array near 43 n spans from corsica island across the tyrrhenian region and the apenninic belt to the adriatic coast we applied particle motion covariance matrix decomposition and cross correlation methods to estimate the polarization direction of the fast split shear wave and the delay time between split phases t most of the analyzed shear waves show clear evidence of splitting the in the adriatic foreland and in the apennines are approximately parallel to the strike of the mountain belt nw se the largest t correspond to the highest elevations suggesting that anisotropy is related to the compressional tectonics which built the apennines and that this tectonic compression involved at least the entire lithosphere in the tyrrhenian area we observe oriented about e w suggesting a reorientation of the mantle fabric due to astenospheric flow responsible for the e w post orogenic extension observed at the surface

evolution of high arctic glacial landforms during deglaciation abstract glacial landsystems in the high arctic have been reported to undergo geomorphological transformation during deglaciation this research evaluates moraine evolution over a decadal timescale at midtre lovenbreen svalbard this work is of interest because glacial landforms developed in svalbard have been used as an analogue for landforms developed during pleistocene mid latitude glaciation ground penetrating radar was used to investigate the subsurface characteristics of moraines to determine surface change a lidar topographic data set obtained 2003 and a uav derived obtained 2014 digital surface model processed using structure from motion sfm are also compared evaluation of these data sets together enables subsurface character and landform response to climatic amelioration to be linked ground penetrating radar evidence shows that the moraine substrate at midtre lovenbreen includes ice rich radar velocities of 0 17 m ns 1 and debris rich radar velocities of 0 1 0 13 m ns 1 zones the ice rich zones are demonstrated to exhibit relatively high rates of surface change mean thresholded rate of 4 39 m over the 11 year observation period however the debris rich zones show a relatively low rate of surface change mean thresholded rate of 0 98 m over the 11 year observation period and the morphology of the debris rich landforms appear stable over the observation period a complex response of proglacial landforms to climatic warming is shown to occur within and between glacier forelands as indicated by spatially variable surface lowering rates landform response is controlled by the ice debris balance of the moraine substrate along with the topographic context such as the influence of meltwater site specific characteristics such as surface debris thickness and glaciofluvial drainage are therefore argued to be a highly important control on surface evolution in ice cored terrain resulting in a diverse response of high arctic glacial landsystems to climatic amelioration these results highlight that care is needed when assessing the long term preservation potential of contemporary landforms at high arctic glaciers a better understanding of ice cored terrain facilitates the development of appropriate age and climatic interpretations that can be obtained from palaeo ice marginal landsystems

crustal structure above a retreating trench receiver function study of the northern apennines orogen abstract teleseismic receiver functions recorded along a densely spaced transect of 20 broad band seismic stations highlight systematic spatial variation of crustal thickness across the northern apennines italy revealing the two sides of an active continental orogenic zone the crustal structure has been investigated using a 1d grid search technique based on the coherent arrivals of forward and reverberated p to s converted phases from the moho at the sw end of the transect the tyrrhenian sea and tuscany are characterized by a shallow moho 20 25 km and a sharp impedance contrast at the opposite edge the definition of the crust mantle boundary is problematic suggesting a gradual and or complicated transition from the crust to the mantle in the adriatic domain however where we can resolve it the crustal thickness is larger 35 km the boundary between these two crustal regimes coincides with the high crest of the apennines shear wave splitting measurements an upper mantle texture indicator in the area reveal a correspondence between crustal thickness and mantle fabric transitions we suggest that these spatially coincident changes in the crustal structure and the upper mantle texture beneath high apennines mark the edge of the eurasian plate in italy

p wave tomography of the mantle under the alpine mediterranean area 1 we study the upper mantle p wave velocity structure below the euro mediterranean area down to 1000 km depth by seismic travel time tomography we invert summary residuals constructed with both regional and teleseismic first arrival data reported by the international seismological centre isc 1964 1995 introducing some alternative strategies in the travel time tomographic approach and a new scheme to correct teleseismic data for global mantle structure our high resolution model pm0 5 is parameterized with three dimensional 3 d linear splines on a grid of nodes with 0 5 spacing in both horizontal directions and 50 km vertical spacing we obtain about 26 root mean square rms reduction of residuals by inversion in addition to roughly 31 reduction after summary rays formation and selection sensitivity analyses are performed through several test inversions to explore the resolution characteristics of the model at different spatial scales the distribution of large scale fast anomalies suggests that two different stages of a convection process presently coexist in very close regions the mantle dynamics of western central europe is dominated by blockage of subducted slabs at the 660 km discontinuity and ponding of seismically fast material in the transition zone contrarily in the eastern mediterranean fast velocity material sinks into the lower mantle suggesting that the flow of the cold downwelling here is not blocked by the 660 km discontinuity on a smaller scale the existence of tears in the subducted slab lithospheric detachment all along both margins of the adriatic plate as proposed by some authors is not supported by our tomographic images

younger dryas glacial landsystems in north west scotland an assessment of modern analogues and palaeoclimatic implications abstract by explicitly linking process to form landsystem models developed in modern environments provide powerful tools for the reconstruction of past environments from the sedimentological and geomorphological record some landform characteristics however may originate by more than one process equifinality so although a particular depositional model may fit the data it is not necessarily the correct one here we critically examine the use of modern analogues to interpret glacial landforms focusing on hummocky moraine a distinctive landform association consisting of numerous sharp crested moraine mounds and ridge fragments which occurs on many valley floors in upland britain detailed studies of examples of younger dryas age in the north west highlands of scotland show that they represent ice contact fans which have been affected to varying degrees by ice push and subglacial deformation and that they formed at active oscillating ice margins the sedimentological data are inconsistent with an origin by englacial thrusting as has been proposed for similar moraines elsewhere in upland britain on the basis of morphological criteria comparison with modern glacial landsystems shows that although aspects of hummocky moraines in the study area have close modern counterparts none provides an exact analogue in all respects this may reflect the distinctive climate of western scotland during the younger dryas estimates of mean july temperatures in the younger dryas in scotland based on chironomid assemblages are c 8 c at sea level when combined with reconstructed equilibrium line altitudes for contemporaneous glaciers these estimates indicate mean annual precipitation totals in the range of 2358 337 mm yr 1 at sea level in nw scotland c 26 higher than present day values the implied heavy snowfall suggests that glaciers in western scotland during the younger dryas were of high activity type unlike modern glaciers in svalbard for example high glacier velocities and high winter precipitation would suppress permafrost development despite low mean annual temperatures the climatic environment also favoured rapid oscillations of glacier margins during both glacier build up and retreat phases climatic factors combined with the availability of large quantities of subglacial debris led to the development of distinctive glacial landsystems which may have no direct modern analogue

the italian cmt dataset from 1977 to the present abstract the ingv harvard european mediterranean regional centroid moment tensor rcmt catalog collects solutions routinely computed since 1997 for earthquakes with moderate magnitude 4 5 m 5 5 in the mediterranean region the database represents an extension to smaller magnitudes of the harvard global cmt catalog based on analysis of seismograms recorded at regional distance and modeling of intermediate period surface waves the catalog includes about 600 events 200 of which in the italian region this study extends the catalog back in time for the italian region as long as made possible by available digital data i e since 1977 with the same analysis and inversion method used for current seismicity as a result we present here 65 new moment tensors for years between 1977 and 1997 these solutions represent 45 of the total number of events analyzed the existing seismograms being often too scarce to allow a stable solution the new dataset includes events in many seismic zones where moderate seismicity had previously been scarcely documented e g the po plain the central to southern apennines and the adriatic sea the complete dataset including previously determined rcmts and cmts represents the seismic deformation in the italian area during the last 25 years

seismic anisotropy beneath the northern apennines italy mantle flow or lithosphere fabric shear wave splitting estimates from recordings of 10 portable seismographic stations during the first year of the retreat seismic deployment in combination with broadband data from the italian national seismic network are associated with seismic anisotropy within the upper mantle beneath the northern apennines anisotropic parameters derived from both shear wave splitting and p travel time residuals vary geographically and depend on event back azimuth reflecting complexity in the underlying mantle strain field variations of the splitting time delays and fast polarization seem to exclude a 2 d sublithosphere corner flow associated with the apennines subduction as the main source of the inferred anisotropy the anisotropic signal may be generated by a frozen in fabric of the adriatic and tyrrhenian lithosphere domains or by flow variations induced by episodic and fragmentary slab rollback

sks splitting in southern italy anisotropy variations in a fragmented subduction zone abstract in this paper we present a collection of good quality shear wave splitting measurements in southern italy in addition to a large amount of previous splitting measurements we present new data from 15 teleseisms recorded from 2003 to 2006 at the 40 stations of the cat scan temporary network these new measurements provide additional constraints on the anisotropic behaviour of the study region and better define the fast directions in the southern part of the apulian platform for our analysis we have selected well recorded sks phases and we have used the method of silver and chan to obtain the splitting parameters the azimuth of the fast polarized shear wave and delay time t shear wave splitting results reveal the presence of a strong seismic anisotropy in the subduction system below the region three different geological and geodynamic regions are characterized by different anisotropic parameters the calabrian arc domain has fast directions oriented nne ssw and the southern apennines domain has fast directions oriented nnw sse this rotation of fast axes following the arcuate shape of the slab is marked by a lack of resolved measurements which occurs at the transition zone between those two domains the third domain is identified in the apulian platform here fast directions are oriented almost n s in the northern part and nne ssw to ene wsw in the southern one the large number of splitting parameters evaluated for events coming from different back azimuth allows us to hypothesize the presence of a depth dependent anisotropic structure which should be more complicated than a simple 2 layer model below the southern apennines and the calabrian arc domains and to constrain at 50 km depth the upper limit of the anisotropic layer at least at the edge of southern apennines and apulian platform we interpret the variability in fast directions as related to the fragmented subduction system in the mantle of this region the trench parallel observed in calabrian arc and in southern apennines has its main source in the asthenospheric flow below the slab likely due to the pressure induced by the retrograde motion of the slab itself the pattern of in the apulian platform does not appear to be the direct result of the rollback motion of the slab whose influence is limited to about 100 km from the slab the anisotropy in the apulian platform may be related to an asthenospheric flow deflected by the complicated structure of the adriatic microplate or may also be explained as frozen in lithospheric anisotropy

glacial geomorphological mapping a review of approaches and frameworks for best practice geomorphological mapping is a well established method for examining earth surface processes and landscape evolution in a range of environmental contexts in glacial research it provides crucial data for a wide range of process oriented studies and palaeoglaciological reconstructions in the latter case providing an essential geomorphological framework for establishing glacial chronologies in recent decades there have been significant developments in remote sensing and geographical information systems gis with a plethora of high quality remotely sensed datasets now often freely available most recently the emergence of unmanned aerial vehicle uav technology has allowed sub decimetre scale aerial images and digital elevation models dems to be obtained traditional field mapping methods still have an important role in glacial geomorphology particularly in cirque glacier valley glacier and icefield ice cap outlet settings field mapping is also used in ice sheet settings but often takes the form of necessarily highly selective ground truthing of remote mapping given the increasing abundance of datasets and methods available for mapping effective approaches are necessary to enable assimilation of data and ensure robustness this paper provides a review and assessment of the various glacial geomorphological methods and datasets currently available with a focus on their applicability in particular glacial settings we distinguish two overarching work streams that recognise the different approaches typically used in mapping landforms produced by ice masses of different sizes i mapping of ice sheet geomorphological imprints using a combined remote sensing approach with some field checking where feasible and ii mapping of alpine and plateau style ice mass cirque glacier valley glacier icefield and ice cap geomorphological imprints using remote sensing and considerable field mapping key challenges to accurate and robust geomorphological mapping are highlighted often necessitating compromises and pragmatic solutions the importance of combining multiple datasets and or mapping approaches is emphasised akin to multi proxy approaches used in many earth science disciplines based on our review we provide idealised frameworks and general recommendations to ensure best practice in future studies and aid in accuracy assessment comparison and integration of geomorphological data these will be of particular value where geomorphological data are incorporated in large compilations and subsequently used for palaeoglaciological reconstructions finally we stress that robust interpretations of glacial landforms and landscapes invariably requires additional chronological and or sedimentological evidence and that such data should ideally be collected as part of a holistic assessment of the overall glacier system

geochronology and geomorphology of the jones point glacial landform in lower hudson valley new york insight into deglaciation processes since the last glacial maximum abstract the glacial deposits at jones point located on the western side of the lower hudson river new york were investigated with geologic geophysical remote sensing and optically stimulated luminescence osl dating methods to build an interpretation of landform origin formation and timing osl dates on eight samples of quartz sand seven single aliquot and one single grain of quartz yield an age range of 14 27 ka for the proglacial and glaciofluvial deposits at jones point optical age results suggest that jones point deposits largely predate the glacial lake albany drainage erosional flood episode in the hudson river valley ca 15 13 ka based on this data we conclude that this major erosional event mostly removed valley fill deposits leaving elevated terraces during deglaciation at the end of the last glacial maximum lgm our analysis supports the earlier 15 ka date for the flood occurrence and suggests that more recent overlying glaciofluvial deposits formed in the lee side of the jones point promontory

on the relation between seismic anisotropy and finite strain because seismic anisotropy in the upper mantle is due primarily to lattice preferred orientation lpo of olivine crystals induced by deformation observations of anisotropy can provide constraints on mantle deformation and flow in this paper we use a previously published theory for deformation induced lpo ribe and yu 1991 to quantify the relation between seismic anisotropy and deformation for two model compositions a pure olivine dunite aggregate and a harzburgite comprising 70 olivine and 30 enstatite analytical and numerical solutions of the governing equations show that the predicted lpo and hence also the seismic anisotropy depends only on the finite strain and not on the deformation path by which that strain is produced the magnitude of the anisotropy depends only on the ratios c1 c2 and c2 c3 where c1 c2 c3 are the lengths of the principle axes of the finite strain ellipsoid and the directions of maximum and minimum compressional wave velocity vp coincide with the axes c1 and c3 respectively we calculate the percent anisotropies for compresional and shear waves propagating along the three principle axes of the finite strain ellipsoid as functions of the axial ratios c1 c2 and c2 c3 for our two model compositions however inferences of the magnitude of finite strain obtained using these results are likely to be minimum estimates because our theory neglects the effects of dynamic recrystallization finally we present as a byproduct of this study a new direct method for calculating the finite strain produced by an arbitiary deformation history

correlation of late quaternary moraines impact of climate variability glacier response and chronological resolution abstract the last decade has seen a global surge in the number and resolution of well dated geomorphological reconstructions of mountain glacier fluctuations and former ice sheet extents this has been facilitated by the widespread deployment of large samples of terrestrial cosmogenic nuclide dating tcnd allowing more sophisticated probability analyses for reducing the statistical uncertainty of moraine ages and testing of correlations at local regional and hemispheric scales geochronological advances in the field laboratory and on model calibration have taken place in parallel with modelling of palaeoclimate based on glacier reconstructions and of glacier sensitivity to temperature and precipitation forcing in spite of these advances basic conceptual issues remain this review questions whether the technical leap forward in dating has encouraged us to over reach our interpretive limits particularly in terms of the concept and practice of correlation we propose that to enable reliable correlation glacier chronologies should first be examined for their climatic integrity spatial coherence and chronological robustness even with excellent dating interpretive complexity remains due to complex climate signals and glacier response characteristics and to erosion censoring of the landform record all are issues which must be addressed to avoid either spurious lumping correlation or splitting differentiation of glacier chronologies and thus misinterpretation of the climatic significance of reconstructed glacier advances we suggest that the reliability of correlation is no better than the weakest link in the chain of reasoning which connects climatic fluctuations with dated landforms and sediments improved dating means that poor chronological resolution is less likely to be the limiting factor for correlation but shifts the focus onto other less quantifiable sources of uncertainty these conceptual statements are exemplified with reference to holocene glacial chronologies of contrasting mid latitude environments in southern norway iceland and new zealand

himalayan glacial sedimentary environments a framework for reconstructing and dating the former extent of glaciers in high mountains abstract reconstructing paleoenvironmental change from glacial geologic evidence in the himalayas has been difficult because of the lack of organic material for radiocarbon dating and the problems of correctly identifying the origin of highly dissected landforms studies of the contemporary glacial depositional environments and ancient landforms and sediments in the hunza valley karakoram mountains the lahul and garhwal himalaya and the khumbu himalaya illustrate the variability in processes landforms and sediment types these studies can be used to interpret ancient landforms and sediments for paleoenvironmental reconstructions and aid in forming strategies for sampling sediments and rocks for the developing techniques of cosmogenic radionuclide crn surface exposure and optically stimulated luminescence osl dating many himalayan glaciers have thick covers of supraglacial debris derived from valley sides and such debris mantled glaciers exhibit important differences from clean glaciers both in terms of debris transport processes and the depositional landforms that they produce analysis of sediment landform associations can be used to reconstruct processes of sediment transport and deposition and the relationship between moraines and other landforms and climatic forcing cycles such analysis is of fundamental importance in guiding sampling and interpretation in crn and osl dating work

moho depth and vp vs ratio in peninsular italy from teleseismic receiver functions 1 we present a new data set of moho depth estimates for peninsular italy obtained from receiver functions analysis and a grid search approach teleseismic records from 174 broadband seismic stations were used to compute the receiver function data set in general our results agree well with previous knowledge adding original information in many regions where previous data were lacking or uncertain we find broad regions with consistent moho depth namely 1 the peri tyrrhenian areas bordering the homonymous sea have a 20 to 25 km deep moho 2 the foreland regions adriatic apulia iblean with 30 35 km deep moho 3 the apennines belt where we find westward deepening of the adriatic moho down to 50 km depth that well delineate the westward adria subduction overlayed by the shallow tyrrhenian moho 4 calabria shows a flat 40 km deep moho suddenly dipping at high angle from the tyrrhenian coast westward defining the ionian subduction and 5 a clear separation between northern and southern apennines is marked by a region of almost flat moho possible evidence of a detached slab in between we also find that in the northern apennines the shallow tyrrhenian moho is continuous for more than 200 km from the sea to under the northern apennines with a generally flat geometry and a few undulations suggesting either the boudinage or episodic pulses of extension of the tyrrhenian crust during its pliocene quaternary stretching the eastward extent of the tyrrhenian moho below the apenninic belt approximately corresponds to the eastward extent of the observed extension in the upper crust as mapped by the normal faulting earthquakes in this portion of the apennines we interpret an intracrustal discontinuity sw dipping below the belt parallel to the adria moho as the top of the lower crust being subducted beneath the apennines the subcrustal earthquakes of this region down to 80 km depth seem to be located within this subducted crustal layer the southern apennines show the same general geometry of subduction as the northern arc although the former have a less defined on land extended region and no earthquakes in the lower crust uppermost mantle in between the central apennines present a different moho geometry no clear doubling of the two plates but rather a constant bilateral deepening possibly associated to a crustal root with no evidence of a subduction setting this reinforces the hypothesis of a detached slab in this area we also present the first large scale mapping of average crustal vp vs ratios for peninsular italy the results although representing averages over the whole crust enhance some interesting features the most evident are belts of high vp vs in the thinned crust of the apennines where extension has long been active in the quaternary probably as an effect of highly fractured rocks with abundant fluid circulation strong correlation exists between areas of high vp vs and quaternary volcanoes suggesting the presence of fluids at depth

genesis stability and preservation potential of large lateral moraines of alpine valley glaciers towards a unifying theory based on findelengletscher switzerland abstract lateral moraines are prominent features of glaciated landscapes in high mountain environments and key landforms in glacier and palaeoclimatic reconstructions yet compared to smaller moraines they have been little studied and several aspects are not well understood we here present detailed sedimentological results from the lateral moraines of findelengletscher in sw switzerland to gain new insights into the formation of these landforms the lateral moraines studied here stand up to 140 m above the valley floor are over 3 km long and strongly asymmetrical in cross profile with distal slopes between 29 and 36 and proximal slopes that are commonly 41 64 but locally reach angles of up to 80 recorded lithofacies comprise loose clast and matrix supported stratified diamicts and intercalated sorted sediments in the distal slopes and near the crestline overconsolidated matrix supported massive and weakly stratified diamicts and streaked out sorted sediment lenses in the core and proximal slopes and partly intercalated dark brown layers overlain by loose and consolidated diamicts exposed in near vertical walls in the proximal flank these are interpreted as supraglacial debris flow units with intercalated fluvial wash horizons glaciotectonised and subglacial traction till with boudinaged and streaked out sediment lenses and palaeosoils overlain by sediment produced by overtopping of the former moraine surface during a subsequent advance of the glacier clast shape analysis and process observations reveal that the dominant mode of transport is subglacial and glaciofluvial and that the main mode of sediment delivery to the moraines is by debris flows after the material has been transferred from the bed via englacial debris bands and meltout at the surface this differs from previous studies that found that a supraglacial source was dominant sedimentary structures clast fabric and process observations during the 1979 1980 readvance of findelengletscher strongly suggest that proximal layers of reworked pre existing sediments and or basal traction zone till have been plastered onto the moraine core in several locations causing a high degree of overconsolidation and strongly clustered fabric eigenvalues s 1 0 94 with clustering parallel to the moraine crestline this suggests that a combination of basal lateral drag and lateral plastering produces the observed proximal stability and ensures a high preservation potential we develop a conceptual model that describes alpine lateral moraines as structurally complex landforms that do not just record a single event as often surmised and we discuss implications for palaeo glacier reconstruction and the application of numerical dating methods

the final phase of dead ice moraine development processes and sediment architecture kotlujokull iceland consecutive phases of de icing of ice cored moraines and the formation of dead ice moraine were monitored over a 4 year period at the terminus of the kotlujokull glacier iceland particularly the transition from partially ice cored moraine with isolated dead ice blocks to the ice free landscape receives attention in this paper in order to link the final melting processes to the architecture of the sedimentary end product in the current humid sub polar climate of south iceland de icing of partially ice cored moraines results chiefly from melting along the bottom surface of ice cores with an annual average rate of 25 cm the final de icing is associated with an interrelated group of re sedimentation processes and surface features series of sinkholes evolve at the toe of dead ice blocks which initiate retrogressive rotational sliding or backslumping of the ice cored slopes and the formation of distinct edges and fractures in the adjacent basins although backslumping is the dominant process in this phase of re sedimentation structures resulting from this process are rarely recognized in the ice free landscape as ice cores gradually diminish the effect of the latest re sedimentation events will overprint or destroy most existing sedimentary characteristics thus in the ice free landscape structures mainly related to the formation of sinkholes and fractures remain imprinted on the sediment succession generally no inversion of the topography occurs during the final phase of de icing the overall topography recognized in the late phase of the fully ice cored terrain is merely lowered and the amplitude of the relief reduced as de icing progresses the sediment architecture of the ice free landscape is characterized by heterogeneous and often slumped diamict sediments with variable thickness and lateral distribution clast orientation is related to the direction of slopes and boulders are found in isolated groups or in linear arrangements

geotechnical controls on a steep lateral moraine undergoing paraglacial slope adjustment original article can be found at http sp lyellcollection org copyright geological society

reversal of ice motion during the outburst of a glacier dammed lake on gornergletscher switzerland during the outburst flood of a glacier dammed lake on gornergletscher switzerland in july 2004 the drained lake water triggered anomalous glacier motion at the onset of the outburst the ice flow direction in the vicinity of the lake became closer to the central flowline when the lake discharge magnitude decreased the flow direction altered such that the ice moved back to the azimuth of the initial motion at one of the survey points where the ice flows parallel to the central flowline the ice accelerated along the pre event flow direction followed by a 1808 backward motion that lasted over 2 days these observations indicate the impact of the lake outburst on the subglacial and englacial stress conditions however the reversal in the flow direction is difficult to explain by drawing on our current understanding of glacier mechanics the timing and the timescale of the flow direction changes suggest that the elastic glacier motion and its rebound played a role under the rapidly changing stress conditions but the young s modulus of ice is too large to cause the observed ice motion other processes including basal separation and subglacial sediment deformation are discussed as possible mechanisms for the reversal of the ice motion

p and s wave upper mantle seismic velocity structure beneath the northern apennines new evidence for the end of subduction orogeny in the geologically young northern apennines is explained by the eastward retreat of a convergence zone in which adriatic lithosphere subducts to the west it is unclear however whether all of the lithosphere or only the lower portion has subducted since 15 ma when the convergence zone lay near corsica we combine teleseismic p and s wave arrival time data from the retreat seismic network 2003 2006 and surrounding permanent stations to estimate tomographic images of the upper mantle structure beneath the northern apennines we image a vertically oriented slab that that extends to only 300 km depth our slab termination is shallower than previous studies but is confirmed by resolution tests furthermore our images resolve the southern edge of the northern apennines slab at 43 n with no deep continuity with any slab segment to the south as earlier proposed our results suggest that only a 300 400 km strip of lithosphere has subducted since 15 ma beneath the northern tyrrhenian sea a length roughly equivalent to the distance from the present day west coast of corsica to the crest of the northern apennines although not a definitive indicator the largely aseismic vertical slab configuration and its limited extent coupled with other volcanic and geophysical indicators suggests the delamination scenario of bird 1979 in which only the lower portion of the continental lithosphere subducts

georadar facies and glaciotectonic structures in ice marginal deposits northwest zealand denmark ground penetrating radar gpr measurements have been carried out on an outwash plain and in the rim of an adjacent ice push ridge in northwest zealand denmark the radar profiles are differentiated into radar facies with distinct reflection characteristics the lithology and depositional environment of the radar facies is interpreted by correlating information from profiles in gravel pits geological maps and bore hole data the gpr profiles reveal sedimentary structures and glaciotectonic deformation structures several thrust planes and folds are interpreted from the gpr data the deformation style of the tectonised glaciofluvial sediments is a pro glacial thin skinned thrust complex with associated folding the deformations have resulted in the present ridge morphology seen in the rim of the ice push ridge on top of the deformed sediments and in front of them penecontemporaneous and post tectonic sediments are deposited smoothing the ridge relief created by the thin skinned thrust complex

sks splitting measurements beneath northern apennines region a case of oblique trench retreat abstract we present here the new observations of seismic anisotropy obtained from sks birefringence analysis we studied 27 teleseismic earthquakes recorded by the temporary seismic network of retreat project in the northern apennines region for each station event couple we calculate the anisotropic parameters delay time and fast polarization direction by minimizing the energy in the transverse component our measurements confirm the existence of two domains the tuscany domain on the south west with respect to the apennines shows mostly nw se fast axes directions with a rotation toward e w direction moving toward the tyrrhenian sea the adria domain north east of the apennines orogen shows more scattered measurements with prevailing n s to nne ssw directions also with back azimuthal dependence the transition between the two domains is abrupt in the northern part of the study region but more gradual in the southern part measured delay times 1 8 s on average suggest that the detected anisotropy is located principally in the asthenosphere beneath the adria domain where the presence of a double layer structure seems consistent a lithospheric contribution is plausible an interpretation in terms of ongoing mantle deformation suggests a differential evolution of the trench retreat process along the northern apennines orogen the orogen parallel anisotropy in the study region is beneath the inner part of the belt instead of beneath its crest and no orogen normal measurements are found in the tuscany side compared to the anisotropy pattern of the typical slab retreat seen in southern part of the northern apennines in the northernmost one the anisotropy suggests that an oblique trench retreat has occurred possibly linked to northern apennines retreat since 5 ma

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

shear wave splitting measurements problems and solutions abstract we compare sensitivity and reliability of three basic techniques of shear wave splitting analysis cross correlation of wave components minimization of covariance matrix eigenvalues and minimizing energy on the transverse component of both synthetic and real data point out some problems and propose solutions we discuss major difficulties of evaluating shear wave splitting parameters which are not always obvious in routine processing and can sometimes lead to false results and wrong interpretations we describe effects of pre processing of digital records of shear waves e g filtering and setting lengths of analyzed signals and discuss reliability of results to minimize outliers in evaluated splitting parameters for reliable evaluation of splitting of medium quality sks wave forms which are valuable mainly in temporary deployments of stations we recommend a careful band pass filtering of the signal using a window length not shorter than the dominant period inspecting the signal noise ratio on t component and the particle motion the transverse minimization method provides usually more robust and stable solutions than the other two methods in the conclusion we suggest how to proceed in evaluation of splitting parameters to ensure reliable solutions even for medium or low quality shear waveforms recorded frequently during temporary field measurements

gpr survey of a lobate rock glacier in yankee boy basin colorado usa abstract the internal structure of a lobate rock glacier located in the san juan mountains of southwest colorado was investigated using ground penetrating radar gpr a 440 m 25 mhz longitudinal profile oriented along the central axis of the rock glacier shows moderate to strongly coherent reflection horizons or layers that can be recognized clearly to a depth of 30 35 m the layers are interpreted as representing ice supersaturated sediments and coarse blocky rockslide debris that are the result of flow perhaps generated by seasonal snow pack covered by episodic debris flows or high magnitude discharges of talus from the cirque headwall profiles collected at 50 mhz indicate that in the upper 20 m thickness of the rock glacier many of these layers are laterally continuous the total depth of penetration 40 m at 25 mhz was sufficient to detect the rock glacier cirque floor contact which is composed of underlying moraine several prominent reflection events that subdivide the profile into broad 10 15 m thick layers represent contacts between major depositional units these units are believed to be individual flow lobes that were initiated at various cirque headwall locations we interpret this rock glacier to be a composite feature that formed by a process involving the development and subsequent overlap of discrete flow lobes that have over ridden older glacial moraine and protalus rampart materials the latter materials have been incorporated into the present flow structure of the rock glacier

shear wave splitting as a diagnostic of variable anisotropic structure of the upper mantle beneath central fennoscandia abstract we analyze splitting of shear waves recorded during the svekalapko passive seismic experiment in south central finland to study fabrics of the mantle lithosphere of the precambrian region and thus to bring information into a debate on existence of plate tectonics or its forms in the early stage of continent formation geographical variations of the splitting parameters and their distinct dependence on direction of wave propagation through the upper mantle allow us to identify six domains of the central fennoscandian mantle lithosphere including the proterozoic archean transition and to model their fabrics by joint inversion of body wave anisotropic parameters fabrics of the archean mantle lithosphere can be approximated by a peridotite aggregate with lineation a dipping to the ne on the other hand anisotropy of the proterozoic mantle lithosphere is weaker and we model its fabric by the a c foliations dipping to the se we present a 3d self consistent anisotropic model of the proterozoic and archean upper mantle along the sw ne profile in the south central finland boundaries of inter growing wedges of the proterozoic and archean mantle lithospheres explain the longitudinal and shear wave propagation and polarization mantle xenolith ages surface wave tomography and location of the upper mantle reflectors we interpret the six anisotropic domains as fragments of mantle lithosphere retaining an old fossil olivine fabric which was created before these micro continents assembled

gpr based detection of pleistocene periglacial slope deposits at a shallow depth test site abstract pleistocene periglacial slope deposits ppsd almost completely cover the mountainous regions of germany and are the parent material for soil formation it is therefore necessary to map their thickness and spatial distribution the mapping of periglacial slope deposits can be performed more quickly than conventional probing by drilling or soil profile analysis if ground penetrating radar gpr is used because the use of gpr to map soils or soil depth depends to a large degree on the suitability of soil properties the performance of gpr in mapping layered substrates was evaluated at a test site with varying water content and substrate properties we focus on the efficiency of gpr in mapping loess rich layers above layers with a high stone content within a depth range of 1 m different materials such as loess metabasalt and slates including heavily weathered slates saprolite were studied the test site was equipped with several time domain reflectometry tdr probes to monitor soil water content changes for the period of one year systematic investigations of the reflection patterns were performed with 100 200 400 500 and 900 mhz antennae with respect to the quality of measurement dielectric coefficient and soil water content of different material combinations it became clear that the 400 mhz antenna is most suitable for creating images of loess and stone layers at the depth range of 1 m and under natural climatic conditions the results prove that the most important effect the substrates at the test site have on gpr is produced by the differences in water content of bordering layers making the soil water capacity of the materials a decisive parameter for evaluating gpr performance the water content dependent dielectric permittivities show higher values for saprolite heavily weathered slate compared to loess by a factor of 1 3 to 2 with water content increasing from 15 to 40 vol respectively in doing so we discovered the dielectric permittivity of loess to be 1 2 to 1 5 times higher than that of unweathered slate at the same water content we were able to locate horizontal layer boundaries at the test site starting at a minimum of 0 5 vol water content difference and a reflection coefficient r 0 02 between the layers the results obtained at the test site show the ability of gpr to detect layering in ppsd at different water contents and help to predict the performance of gpr measurements in mapping of ppsd

a method to estimate the ice volume and ice thickness distribution of alpine glaciers sound knowledge of the ice volume and ice thickness distribution of a glacier is essential for many glaciological applications however direct measurements of ice thickness are laborious not feasible everywhere and necessarily restricted to a small number of glaciers in this paper we present a method to estimate the ice thickness distribution and the total ice volume of alpine glaciers this method is based on glacier mass turnover and principles of ice flow mechanics the required input data are the glacier surface topography the glacier outline and a set of borders delineating different ice flow catchments three parameters describe the distribution of the apparent mass balance which is defined as the difference between the glacier surface mass balance and the rate of ice thickness change and two parameters define the ice flow dynamics the method was developed and validated on four alpine glaciers located in switzerland for which the bedrock topography is partially known from radio echo soundings the ice thickness along 82 cross profiles can be reproduced with an average deviation of about 25 between the calculated and the measured ice thickness the cross sectional areas differ by less than 20 on average this shows the potential of the method for estimating the ice thickness distribution of alpine glaciers without the use of direct measurements

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

belt parallel mantle flow beneath a halted continental collision the western alps constraining mantle deformation beneath plate boundaries where plates interact with each other such as beneath active or halted mountain belts is a particularly important objective of mantle tectonics that may bring a depth extent to the earth s surface observation such mantle deformation can be mapped at scale lengths of several tens of kilometers through the analysis of seismological data and particularly by mapping seismic anisotropy from the splitting analysis of vertically propagating sks waves that largely reflect the strain induced crystal preferred orientations of the rock forming minerals within the upper mantle in the present study we analyse data from approximately 50 broadband seismic stations covering the western alps and we provide a coherent picture of upper mantle anisotropy beneath the belt the large scale anisotropy pattern is characterized by fast split directions that closely follow the trend of the belt moreover the maximum anisotropy magnitude is not located beneath the internal zones of the belt but instead beneath external units all suggests that the anisotropy is likely dominated by sublithospheric mantle deformation we propose that the observed anisotropy pattern can be explained by recent or active mantle flow around the eurasian slab presently plunging beneath the inner parts of the alps

tomographic constraints on the geodynamic evolution of the italian region in this paper we present p wave tomographic images of the mantle beneath italy obtained by inverting 6000 teleseismic p and pkp wave arrival times accurately repicked recorded in the time period 1988 1994 by the stations of the national seismic network of the istituto nazionale di geofisica we pay great attention in the data selection and picking procedure of seismic phases to obtain a very high quality data set the data were inverted with the well established aki christofferson husebye tomographic technique different reference models and residuals computation have been tried to verify the stability of the results the high quality of the repicked arrival times allows us to enhance the definition of the deep structures beneath both the alps and the apennines looking for their lateral and vertical continuity down to 800 km depth the main finding of this study is a continuous high velocity body located between 250 and 670 km depth beneath the entire apenninic system dipping toward the tyrrhenian area which continues upward segmented in two main anomalies in the northern apenninic and the calabrian arcs we interpret this high velocity feature as the subducted oceanic lithosphere between the eurasian and african plates dipping down to the upper lower mantle boundary beneath the tyrrhenian sea the retrieved images of the lithosphere subducting beneath apennines are reliable in terms of thickness about 80 90 km and p wave velocity contrast 2 4 higher than the normal mantle furthermore our tomographic images which focus on the deep geometry and continuity of the velocity structures provide new keys to understanding the geodynamic evolution of the italian region the segmentation of the high velocity slab upward suggests a complex evolution of the arc trench system and the initially continuous subduction of the ionian adriatic plate progressively developed in subordinate arcs probably due to lateral heterogeneity of the subducting lithosphere

from underplating to delamination retreat in the northern apennines abstract recordings of teleseismic earthquakes from a dense set of temporary and permanent broadband seismic stations reveal the lithospheric structure of the northern apennines and support the scenario of a retreating detachment within the mid crust lithospheric delamination appears crucial to the formation and evolution of the apennines orogen receiver function rf stacks outline a continuous west dipping ps converted phase from a positive velocity jump that we interpret as the top of the lower crust and mantle of the adria continental lithosphere which is descending into the shallow mantle the correlation of seismicity with two rf profiles across the northern apennines suggests distinct stages of lithospheric delamination active penetration of the detachment into the adria lithosphere seems evident in the south east with induced shallow mantle flow facilitated by slab dehydration penetration of the detachment in the north west seems to have arrested and is possibly marked by crustal underplating this layer atop the apennines slab is visible only down to 80 km depth and suspends above an oppositely dipping paired positive negative ps converted phase in stacked receiver functions the break in the west dipping adria lithosphere conflicts with a westward subduction scenario continuous from the oligocene lateral changes of deep structure and seismicity along the northern apennines suggest that underplating of crustal material and delamination retreat are distinct mechanisms active today in the western and eastern sectors respectively of the northern apennines negative ps pulses at 100 120 km depth help to define a seismic lithosphere asthenosphere boundary lab but cross cut a volume of high velocity mantle rock as inferred from tomographic models we hypothesize that this seismic lab is a rheological discontinuity that affects the frequency band of seismic body waves but not the long term viscous response that governs the evolution and eventual detachment of the continental slab

mapping seismic anisotropy using harmonic decomposition of receiver functions an application to northern apennines italy 1 isotropic and anisotropic seismic structures across the northern apennines italy subduction zone are imaged using a new method for the analysis of teleseismic receiver functions rfs more than 13 000 p wave coda of teleseismic records from the 2003 2007 retreating trench extension and accretion tectonics retreat experiment are used to provide new insights into a peculiar subduction zone between two continental plates that is considered a focal point of mediterranean evolution a new methodology for the analysis of receiver functions is developed which combines both migration and harmonic decomposition of the receiver function data set the migration technique follows a classical common conversion point scheme and helps to focus on a crucial depth range 20 70 km where the mantle wedge develops harmonic decomposition of a receiver function data set is a novel and less explored approach to the analysis of p to s converted phases the separation of the back azimuth harmonics is achieved through a numerical regression of the stacked radial and transverse receiver functions from which we obtain independent constraints on both isotropic and anisotropic seismic structures the application of our method to the retreat data set succeeds both in confirming previous knowledge about seismic structure in the area and in highlighting new structures beneath the northern apennines chain where previous studies failed to clearly retrieve the geometry of the subducted interfaces we present our results in closely spaced profiles across and along the northern apennines chain to highlight the convergence of the tyrrhenian and the adriatic microplates which differ in their crustal structure where the adriatic microplate subducts beneath tuscany and the tyrrhenian sea a signature of the dipping adriatic moho is clearly observed beneath the tyrrhenian moho in a large portion of the forearc region in the area where the two mohos overlap our new analysis reveals the presence of an anisotropic body above the subducted moho there is a strong ps converted phase with anisotropic characteristics from the top of the adriatic plate to a depth of at least 80 km because the ps conversion occurs much deeper than similar ps phases in cascadia and japan dehydration of oceanic crust seems unlikely as a causative factor rather the existence of this body trapped between the two interfaces supports the hypothesis of lower crustal delamination in a postsubduction tectonic setting

glacier dammed lake outburst events of gornersee switzerland gornersee switzerland is an ice marginal lake which drains almost every year subglacially within a few days we present an analysis of the lake outburst events between 1950 and 2005 as well as results of detailed field investigations related to the lake drainage in 2004 and 2005 the latter include measurements of lake geometry water pressure in nearby boreholes and glacier surface motion a distributed temperature index melt model coupled to a linear reservoir runoff model is used to calculate hourly discharge from the catchment of gornergletscher in order to distinguish between the melt precipitation component and the outburst component of the discharge hydrograph in this way drainage volume and timing are determined from 1950 there is a clear trend for the outburst flood to occur earlier in the melt season but there is no trend in lake discharge volumes peak discharges from the lake lie significantly below the values obtained using the empirical relation proposed by clague and mathews 1973 the shapes of the 2004 and 2005 lake outflow hydrographs differ substantially suggesting different drainage mechanisms from water balance considerations we infer a leakage of the glacier dammed lake in 2005 starting 1 week prior to the lake outburst during the drainage events up to half of the lake water is temporarily stored in the glacial system causing substantial uplift of the glacier surface