rapid oscillations in vostok and grip ice cores we investigate the spectral properties of climatic times series derived from two recent ice cores in greenland and east antarctica we find that the signals behave in a similar way in the high frequency part of their spectra the rapid oscillations found in the grip ice core were closely correlated to heinrich events a comparable spectral feature is detected in the vostok ice core we discuss the possibilities of connections between the two hemispheres and proper ice sheet oscillations in the light of simple oscillating climate models

gcm analysis of local influences on ice core δ signals a high resolution gcm is used to examine the effect of changes in local surface climate parameters on the ice sheets that can influence the interpretation of the isotopic signal of the ice from deep cores the model suggests that the 10 c difference between the lgm surface temperature deduced from borehole thermometry and that deduced from the water isotope analysis to a great extent may be due to a modification of the precipitation seasonality in central greenland for central east antarctica the model tends to suggest a weak opposite bias

forces controlling the present day state of stress in the andes the present day state of stress in the andes is expected to be controlled primarily by two different types of forces 1 the resistive force exerted on the western overriding margin of the south american plate and 2 forces that arise from the thickened crust of the andes i e the effect of topography and its compensating crustal root we have studied these forces on the basis of a model for the dynamics of the entire south american plate in which the andes are embedded in this model a given set of forces is constrained by the criterion that the net torque on the plate should vanish a thin elastic shell representation is used to calculate the intra plate stress field associated with the various force distributions we define a reference model for the present study that incorporates a uniform magnitude for the resistance associated with convergence along the western plate margin fpcr plate contact resistance and does not include the effects of topography subsequently we investigate the effect of lateral variation in the magnitude of fpcr and add the topography related forces the main results are 1 a uniform magnitude of fpcr leads to a better match with the observations than a magnitude that is a function of the dip of the lithosphere subducting below the western plate margin 2 the amount of horizontal compression across the andes found in the case that ridge push is considered to be the only force driving the south american plate is small compared to the value required to sustain the andes

hydrothermal venting at hinepuia submarine volcano kermadec arc understanding magmatic hydrothermal fluid chemistry the hinepuia volcanic center is made up of two distinct edifices aligned northwest to southeast with an active cone complex in the se hinepuia is one of several active volcanoes in the northern segment of the kermadec arc regional magnetic data shows no evidence for large scale hydrothermal alteration at hinepuia yet plume data confirm present day hydrothermal discharge suggesting that the hydrothermal system may be too young to have altered the host rocks with respect to measurable changes in magnetic signal gravity data are consistent with crustal thinning and shallow mantle under the volcanic center following the discovery of hydrothermal plumes over hinepuia the submersible shinkai 6500 was used to explore the se cone and sample hydrothermal fluids the chemistry of hydrothermal fluids from submarine arc and backarc volcanoes are typically dominated by water rock interactions and or magmatic degassing chemical analyses of vent fluids show that hinepuia does not quite fit either traditional model moreover the hinepuia samples fall between those typically ascribed to both end member fluid types when plotted on a k mg so4 ternary diagram due to evidence of strong degassing abundant native sulfur deposition and h2s presence the vent sampled at hinepuia is ultimately classified as a magmatic hydrothermal system with a water rock influence this vent is releasing water vapor and magmatic volatiles with a notable lack of salinity due to subcritical boiling and phase separation magmatic hydrothermal fluid chemistry appears to be controlled by a combination of gas flux phase separation processes and volcano evolution and or distance from the magma source

preservation potential for late quaternary river alluvium valley sequences of late quaternary alluvial units reflect alluvial preservation as well as alluvial production factors effects of lateral channel migration incision aggradation and channel stability on preservation potential are explored and then considered in the light of 14 available data sets cartographically dated and model data based on lateral channel migration well mapped and dated late quaternary valley unit surveys and composite age frequency plots for dated alluvial units and flood sediments despite much expectable variation between sites and the complex effects of river activity combinations a common characteristic of the data sets examined is the significance of preservation factors lateral migration tends to eliminate older units as it creates new alluvial deposits whereas incision may lead to the preferential preservation of older units beyond the incision slot aggradational environments are likely to preserve more complete records although simultaneous lateral migration may eliminate possibly repeatedly the upper parts of alluvial units the common pattern of inset and incised streams within pleistocene and early holocene fills or bedrock gives finite extent to later units within narrowing valleys so that development of new valley floor units is necessarily at the expense of reprocessing earlier ones floods associated with both slack water deposits and berms are also responsible for the removal of accessible earlier materials thus limiting the preserved record of earlier events in light of these censoring effects of river activities the sequence of preserved late quaternary units within uk sequences is reconsidered it is concluded that preservation potential factors have led to spatial and temporal bias in the alluvial record and that both here and elsewhere preservation potential needs to be considered systematically alongside variable sedimentation resulting from allogenic environmental factors when interpreting the alluvial archive copyright 2003 john wiley sons ltd journal of quaternary science

crustal features along a w e tyrrhenian transect from sardinia to campania margins central mediterranean abstract the tyrrhenian sea is a neogene back arc basin formed by continental extension at the rear of the eastward migrating apennine subduction system its central part generated from tortonian to pliocene includes the sardinia rifted margin to the west an area with large volcanoes in the deep central sector and the campania rifted margin to the east a reprocessing of some 2000 km of mcs lines a new swath bathymetric map and a review of previous geological and geophysical data allow to analyse the nature and distribution of continental vs oceanic crust in this area which evolved in a short time span the central portion of the southern tyrrhenian sea is characterized by moho at about 10 km depth north of magnghi and vavilov smts this thinned crustal domain include a wide continent ocean transition with the occurrence of extensional allochthons and of serpenitinzed sub continental mantle recalling other well known rifted margins as the iberia one sectors floored by oceanic crust should occur mainly in the southern part of the study area but they do not appear related to discrete spreading ridges the continent ocean boundary cannot be drawn unequivocally in the area due also to the occurrence of widespread and huge magmatic manifestations not related to oceanic spreading these portions of the southern tyrrhenian sea represents therefore a complex oceanic back arc basin surrounded by magma rich rifted continental margins the abundant igneous manifestations and the very high stretching rates observed in the area may be related to the fact that the present tyrrhenian area was occupied by an orogenic domain affected by shortening until middle miocene times which is just before the late miocene onset of back arc extension the lithosphere in the region had then to be rheologically weak abundant generation and ascent of magmas mostly of ocean island basalt type was favoured by the large lithospheric permeability induced by strong extensional deformations

upper mantle structure below the european continent constraints from surface wave tomography and grace satellite gravity data 1 we here exploit fundamental mode rayleigh and love seismic wave information and the high resolution satellite global gravity model ggm02c to obtain a 1 1 3 d image of a upper mantle isotropic shear wave speeds b densities and c density vscoupling below the european plate 20 n 90 n 40 w 70 e the 3 d image of the density vscoupling provides unprecedented detail of information on the compositional and thermal contributions to density structures the accurate and high resolution crustal model allows us to compute a reliable residual topography to understand the dynamic implications of our models the correlation between residual topography and mantle residual gravity anomalies defines three large scale regions where upper mantle dynamics produce surface expression the east european craton the eastern side of the arabian plate and the mediterranean basin the effects of mantle convection are also clearly visible at 1 the eastern sirt embayment 2 the west african craton northern margins 3 the volcanically active region of the canarian archipelago 4 the northern edge of the central european volcanic province and 5 the northeastern part of the atlantic ocean between greenland and iceland strong connections are observed among areas of weak radial anisotropy and areas where the mantle dynamics show surface expression although both thermal and additional dependencies have been incorporated into the density model convective down welling in the mantle below the east european craton is required to explain the strong correlation between the estimated negative mantle residual anomalies and the negative residual topography

reassessment of net surface mass balance in antarctica abstract recent in situ measurements of surface mass balance and improved calculation techniques are used to produce an updated assessment of net surface mass balance over antarctica a new elevation model of antarctica derived from ers 1 satellite altimetry supplemented with conventional data was used to delineate the ice flow drainage basins across antarctica the areas of these basins were calculated using the recent digital descriptions of coastlines and grounding lines the delineation of drainage basins was achieved using an automatic procedure which gave similar results to earlier hand drawn catchment basins more than 1800 published and unpublished in situ measurements of net surface mass balance from antarctica were collated and then interpolated a net surface mass balance map was derived from passive microwave satellite data being employed as a forcing field to control the interpolation of the sparse in situ observations basinwide integrals of net surface mass balance were calculated using t

interpretation of gravity and magnetic anomalies at lake rotomahana geological and hydrothermal implications abstract we investigate the geological and hydrothermal setting at lake rotomahana using recently collected potential field data integrated with pre existing regional gravity and aeromagnetic compilations the lake is located on the southwest margin of the okataina volcanic center haroharo caldera and had well known pre 1886 tarawera eruption hydrothermal manifestations the famous pink and white terraces its present physiography was set by the caldera collapse during the 1886 eruption together with the appearance of surface activities at the waimangu valley gravity models suggest that subsidence associated with the haroharo caldera is wider than the previously mapped extent of the caldera margins magnetic anomalies closely correlate with heat flux data and surface hydrothermal manifestations and indicate that the west and northwestern shore of lake rotomahana are characterized by a large well developed hydrothermal field the field extends beyond the lake area with deep connections to the waimangu area to the south on the south the contact between hydrothermally demagnetized and magnetized rocks strikes along a structural lineament with high heat flux and bubble plumes which suggest hydrothermal activity occurring west of patiti island the absence of a well defined demagnetization anomaly at this location suggests a very young age for the underlying geothermal system which was likely generated by the 1886 tarawera eruption locally confined intense magnetic anomalies on the north shore of lake rotomahana are interpreted as basalt dikes with high magnetization some appear to have been emplaced before the 1886 tarawera eruption a dike located in proximity of the southwest lake shore may be related to the structural lineament controlling the development of the patiti geothermal system and could have been originated from the 1886 tarawera eruption

geophysical modeling of collapse prone zones at rumble iii seamount southern pacific ocean new zealand 1 catastrophic collapses of submarine volcanoes have the potential to generate major tsunami threatening many coastal populations recognizing the difficulties surrounding anticipations of these events quantitative assessment of collapse prone regions based on detailed morphological geological and geophysical mapping can still provide important information about the hazards associated with these collapses rumble iii is one of the shallowest and largest submarine volcanoes found along the kermadec arc and is both volcanically and hydrothermally active previous surveys have delineated major collapse features at rumble iii based on time lapse bathymetry dramatic changes in the volcano morphology have been shown to have occurred over the interval 2007 2009 furthermore this volcano is located just 300 km from the east coast of the north island of new zealand here we present a geophysical model for rumble iii that provides the locations and sizes of potential weak regions of this volcano shipborne and near seafloor geological and geophysical data collected by the auv sentry are used to determine the subsurface distribution of weak and unstable volcanic rocks the resulting model provides evidence for potentially unstable areas located in the southeastern flank of this volcano which should be included in future hazard predictions

palaeoflood and floodplain records from spain evidence for long term climate variability and environmental changes abstract palaeoflood chronologies from seven spanish river basins and floodplain aggradation chronologies from thirteen rivers are analysed these fluvial records were divided in to two sub sets namely atlantic 10 ka record and mediterranean 3 ka record river basins which represent distinct modern hydroclimatic conditions in atlantic basins floods result from intense widespread rainfalls associated with atlantic frontal systems transported by westerly airflow mediterranean river flooding is related to heavy rainfall induced by mesoscale convective systems mcss during autumn months evidence from radiocarbon dates in slackwater flood deposits shows six periods of flood clusters at 10 750 10 240 9550 9130 4820 4440 2865 2350 960 790 and 520 290 cal bp despite the different flood producing weather conditions in atlantic and mediterranean rivers the radiocarbon sample clusters overlap and indicate changes in large scale atmospheric circulation and climatic conditions in the iberian peninsula comparison with proxy records of mean temperature for the northern hemisphere demonstrates a relationship between the period of slackwater flood deposition and cold climatic phases e g the 2650 yr bp climatic event or ad 1590 1650 period of the little ice age radiocarbon dates from aggraded floodplain sediments were clustered at 2710 2320 2000 1830 and 910 500 cal bp the first cluster period is in phase with the timing of slackwater deposition whereas the third 910 500 cal bp occurs in between two periods of increased flood frequency as indicated by the palaeoflood and documentary flood records it is argued that the 910 500 cal bp floodplain aggradation period reflects the first post roman evidence of environmental change related to generalised land use changes at the catchment scale which produced high sediment load transported to overbank areas during high flows

western mediterranean environmental changes evidences from fluvial archives abstract when dealing with current and past landscape evolution a key issue addresses responses of geomorphic systems to the large number of influencing variables identifying morphodynamic phases and revealing interrelations with specific driving forces are demanding tasks for quaternary research in this paper we present late pleistocene and holocene fluvial sedimentation patterns of three western mediterranean river catchments namely jarama river guadalete river and guadalquivir river that extent along a climatic transect from semi humid sw spain to semi arid central spain these studies are based on extensive fieldwork conducted on 36 exposures and 13 drillings in floodplain positions field data is supported by geochemical analyses while the chronological framework was obtained from the analyses of 70 radiocarbon samples results show distinct patterns of fluvial sedimentation as well as soil formation linked to floodplain stability for each river catchment on regional or catchment scale pollen stratigraphical correlation and comparison with lacustrine records show that fluvial dynamics have a strong reaction to climatic shifts with phases of high fragility characterized by catchment erosion and floodplain sedimentation in response to climatic aridification events and phases of climate change in general the comparison of the examined river systems reveals that periods of supra regional floodplain sedimentation in several catchments occurred from 8 0 to 7 0 5 0 to 3 8 2 2 to 1 5 and around 1 0 as well as 0 4 ka cal bp while we found periods of supra regional soil formation from 13 3 to 12 7 7 0 to 5 1 with a short interruption around 6 0 to 5 5 ka 2 8 to 2 3 ka 1 4 to 1 2 ka and 0 8 to 0 5 ka cal bp beside these consistencies we found deviating dynamic patterns that are apparently expressed in terms of differing onset and offset differing durations or even the lack of fluvial system response the main reasons for this can be seen in different regional climate condition and impacts of further influencing factors or in different levels of sensitivity of the river catchments that may be controlled by initial hydrological conditions catchment size or the degree of anthropogenic influence a larger scale assessment shows that fluvial dynamic patterns are hardly comparable across entire spain due to strong spatial heterogeneity of physiographic and climatic conditions on the iberian peninsula in particular when areas are influenced by different circulation systems e g regions influenced by the atlantic ocean vs regions influenced by the mediterranean sea however the consideration of north atlantic marine records reveals a certain coupling between north atlantic coolings atmospheric processes leading to arid climate over large parts of spain as well as increased landscape instability including strong fluvial sedimentation activity attendant atmospheric conditions are discussed

fluvial changes of the guadalquivir river during the holocene in cordoba southern spain this research was funded by a grant from proyectos de cordoba siglo xxi coordinated by prof r jose roldan canas universidad de cordoba

the two stage opening of the western central mediterranean basins a forward modeling test to a new evolutionary model abstract the algero provencal and the tyrrhenian extensional basins developed in two stages in a geodynamic setting characterized by the nearly n s convergence between africa and eurasia the spreading of the provencal basin occurred in the early miocene following a long period of rifting in the western mediterranean area a dramatic eastward shift of the active extensional deformation resulted in the tortonian to quaternary opening of the tyrrhenian basin in a companion paper carminati et al propose that a trench retreat process in a geodynamic setting locked by the continental collisions in the alps and in the betic chain is a viable mechanism for the late oligocene early langhian opening of the western mediterranean a langhian slab detachment episode along the north african margin is likely to have caused the end of the trench retreat along this part of the boundary determining the end of active expansion in the western mediterranean and the beginning of active extension in the tyrrhenian basin the objective of the present paper is to quantitatively test this proposed scenario we calculate by means of a thin shell model the effects of these plate boundary reorganizations on the european stress and strain field we show that the two stage opening of the western and central mediterranean can be explained by the evolution proposed by carminati et al and that in particular the eastward shift of the active extension which produced the termination of the first opening stage and the beginning of the second is likely to have been triggered by the slab detachment episode along the north african margin

morphological pedological and sedimentary evolution on the fringe of the southwestern european drylands during the late pleistocene and holocene evidence of climate and land use changes abstract late quaternary alluvial sedimentary units in the guadiana menor river valley a tributary of the guadalquivir river in southern spain are described based on geomorphological mapping sedimentological analysis palaeosol development and radiocarbon chronology four infill units in the valleys were differentiated with surfaces at 45 mu1 70 mu2 8 6 mu3 and 10 m mu4 above the riverbed each unit is capped by a palaeosol unit mu1 late pleistocene 43 5 34 cal kyr bp consists of gravel and sand in channels and bars in braided river systems distally evolving to silty clays in the floodplain with vertic and clayic calcisols it is capped by dark clays with gleysol development representing wetland environments in endorheic basins channelized gravels alternating with sandy silts make up unit mu2 34 24 cal kyr bp capped by a gypsisol and interpreted as a semi arid alluvial fan distally evolving to playa lake depositional systems unit mu3 5600 2700 cal yr bp extending along the valley bottom is represented by gravels and sand distally evolving to a red and white laminated rhythmite of silt and clay deposited in the playa unit mu4 600 700 cal yr bp is scattered and represented by centimetre thick gravels and sand sheet layers deposited by sheet flows in semi arid constrained alluvial fans alternating intervals of alluvial aggradation 43 5 24 kyr bp 5700 2700 cal yr bp late middle ages and fluvial incision 24 6 cal kyr bp 2700 cal yr bp to 1200 ad 1500 ad to present are interpreted as valley responses to climate variations and changes in land use two regional geomorphological changes are recorded in the sediments 1 climate induced aridification after 34 cal kyr bp with an arid climax after 24 cal kyr bp before the incision linked to the last glacial period and 2 two human forced aggradation stages 5600 2700 cal yr bp and 1200 1400 ad interrupting the late pleistocene to early holocene incisional trend

investigations of the oxygen 18 content of samples from snow pits and ice cores from the filchner ronne ice shelves and ekstrom ice shelf

channel adjustments in the lower guadalquivir river southern spain over the last 250 years abstract the lower guadalquivir river has been subjected to a series of channel adjustments over the last 250 years mainly in response to human factors and disturbances from 1778 to 1918 the results show an oscillation in the sinuosity along the upstream segment and a reduction along the downstream segment in response to artificial cut offs the first phase of incision started in approximately the 1840s 1850s following a previous phase of predominant aggradation probably related to abundant sediment supply caused by deforestation in the catchment during approximately the last 100 years notable incision and progressive channel narrowing occurred in both segments although secondary aggradation upstream of the dams and widening in a portion of the downstream segment were also observed the first phase of bed incision migrating upstream is interpreted as a consequence of artificial meander cut offs whereas most of the adjustments that occurred during the last 100 years are interpreted as a consequence of the large number of dams in the catchment and along the studied area which caused a notable deficit in bedload

enhancing rescue archaeology using geomorphological approaches archaeological sites in paredes asturias nw spain abstract palaeolithic remnants a necropolis roman villa and another minor archaeological site were discovered in paredes spain these sites were the focus of multidisciplinary research during the construction of a large shopping centre in asturias nw spain the aims of this study are 1 to contribute to archaeological prospection in the sites and 2 to develop evolutionary models of the sites based on geomorphological inferences detailed archaeological prospection 103 trenches geomorphologic mapping stratigraphic studies 36 logs and ground penetration radar gpr surveys on five profiles indicate that the location of the settlement source of the necropolis is outside the construction perimeter farther to the southeast the pre holocene evolution of the fluvial landscape is marked by the development of two terraces t1 and t2 that host the early palaeolithic remains in the area ca 128 71 ka the holocene evolution of the landscape was marked by the emplacement of the nora river flood plain covered by alluvial fans after ca 9 ka bp cal bc 8252 7787 subsequently neolithic pebble pits dated ca 5 3 ka bp cal bc 4261 3963 and 4372 4051 were constructed on t2 at the area reoccupied as a necropolis during the late roman period 1590 45 years bp cal ad 382 576 coeval human activity during the late roman period at 1670 60 years bp cal ad 320 430 is also recorded by channel infill sediments in a minor site at the margin of an alluvial fan located to the southeast this work shows that a rescue archaeological study can be significantly enhanced by the implementation of multidisciplinary scientific studies in which the holistic view of geomorphologic settings provide key insights into the geometry and evolution of archaeological sites

analysis of a gradual change in stress regime example from the eastern iberian chain spain abstract the compression extension passage in the eastern iberian chain during the miocene is analyzed structural data suggest that it is a gradual change in stress regime which does not involve rotation but interchange of 1 and 2 axes one of them remaining always vertical the gradual stress evolution is interpreted by a numerical graphic method y r diagram which optimizes combinations of y azimuth of the maximum horizontal axis and r stress ratio explaining groups of fault movements the y r diagrams of some fault populations measured in the castellon region provide optimum tensors appearing within a continuous cloud of solutions from the compressional field to the extensional one movement sequences obtained from superimposed striations indicate a systematic stress change between these two regimes

joint inversion methods with relative density offset correction for muon tomography and gravity data with application to volcano imaging muography is a relatively new geophysical imaging method that uses muons to provide estimates of average densities along particular lines of sight muography can only see above the horizontal elevation of the detector and it is therefore attractive to attempt a joint inversion of muography data with gravity data which is also responsive to density but generally requires combination with another geophysical data set to overcome issues related to non uniqueness and poor depth resolution some previous work has investigated this joint inverse problem and demonstrated the potential improvements to be gained by jointly inverting muography and gravity data however there has yet to be a thorough investigation of different numerical approaches for formulating the joint inverse problem particularly important is how to account for the fact that even though the two data types are sensitive to the same physical quantity density they respond through different response functions moreover the two measurements are affected by different systematic uncertainties that are difficult to model in this work we considered an approximation where the two density quantities inferred from the two data types can be related by an unknown scalar offset we considered various existing and new joint inversion methods that might solve this problem and we applied them to a synthetic volcano imaging scenario based on the puy de dome volcano in the central massif region of france we used unstructured meshes in our modelling to adequately honour the significant topography in that scenario our experiments indicated that the most successful joint inversion method for this type of geological scenario was one in which the data misfit function is reformulated to automatically determine the best fitting offset following a least squares minimization argument however other approaches showed merit and we suggest several of the investigated methods be applied and compared for any specific joint inversion scenario

temporal variation in the stress field of the aegean region we use a forward numerical model to analyse the intra plate stress field in an area of active extension of continental lithosphere the aegean region recent tomographic images of the hellenic subduction zone offer the unique opportunity to address the relation between the evolving aegean stress field and temporal variations in the subduction process to this extent we apply our model to both the present day and the late pliocene situation regarding the current situation it is found that subduction related forces largely explain the observed pattern of tension results obtained for the pliocene indicate that detachment of the slab subducted below western greece may have controlled the observed temporal variation in the pattern of tension

crustal model for the middle east and north africa region implications for the isostatic compensation mechanism summary we present a new 3 d crustal model for the middle east and north africa region that includes detailed topography sediment thickness and moho depth values the model is obtained by collecting integrating and interpolating reliable published sedimentary rock thickness and moho depth measurements in the middle east and north africa region to evaluate the accuracy of the model the 3 d gravity response of the model is calculated and compared with available observed bouguer gravity anomalies in the region the gravity modelling shows that the new crustal model predicts large portions of the observed bouguer anomalies however in some regions such as the red sea and caspian sea regions where crustal structure is relatively well determined the residual anomalies are of the order of a few hundred milligals since the new crustal model results in large residual anomalies in regions where reasonably good constraints exist for the model these large residuals cannot simply be explained by inaccuracies in the model to analyse the cause of these residuals further we developed an isostatically compensated airy type moho depth model and calculated its gravity response isostatic gravity anomalies are in nearly perfect agreement with the observed gravity values however the isostatic model differs significantly from the new 3 d crustal model if isostasy is to be maintained crustal and or upper mantle lateral density variations are needed to explain the large observed gravity residuals

the holocene fluvial chronology of spain evidence from a newly compiled radiocarbon database abstract a critical analysis of 74 radiocarbon dates selected from a total of 102 published and unpublished dates from holocene fluvial environments in spain has identified a number of periods of increased fluvial activity in spain namely 11 170 10 230 9630 8785 7980 6860 5800 4800 3880 3085 2895 1820 1300 0 cal bp the latter period reflecting sustained fluvial response to increased human impact the radiocarbon samples were classified according to type of depositional environment a alluvial overbank b flood basin c alluvial channel gravels d fluvio torrential deposits and e slackwater flood deposits palaeofloods dates from slackwater flood deposits indicated at least five phases of increased frequency of large magnitude floods during the holocene 10 855 10 230 9530 8780 2880 2430 975 790 and 520 265 cal yr bp flood basin type deposition occurred from 7980 to 4830 cal yr bp the main clusters of dates from alluvial floodplain deposits occurred at 2750 2150 and 930 520 cal yr bp the record is discussed in relation to other palaeoenvironmental archives including pollen records of holocene vegetation change and palaeoclimatic proxies such as the north atlantic drift ice record comparison with the latter indicates that major holocene flooding coincided with cold climate phases during 9530 9280 2880 2430 and 520 265 cal yr bp a cooling phase at 10 855 10 230 and warming phases at 9030 8780 and 975 790 cal yr bp

bouguer density determination by fractal analysis density values for the bouguer reduction of two gravity data sets from iceland are determined using a new method based on minimization of the roughness of the bouguer anomaly surface the fractal dimension of the surface is used as a gauge of the roughness the analysis shows the size of topographic features supported by crust without isostatic compensation to be 25 to 30 km in southwest iceland and 9 to 10 km inside the active rifting zone the densities selected for these areas are 2490 and 2730kg m3 respectively

the role of slab detachment processes in the opening of the western central mediterranean basins some geological and geophysical evidence abstract a review of the geological and geophysical data from the central and western mediterranean region and the present day upper mantle structure derived from tomographic studies are utilized in order to define the oligocene recent geodynamic evolution for the area in line with previous work we suggest that the miocene quaternary opening of the western and central mediterranean basins is the result of back arc extension due to the roll back toward the southeast of a northwestward subducting african slab in a geodynamic setting pinned between the alpine and betic collisional zones we find however that this general pattern is complicated by four different detachment events which occurred beneath the alps early oligocene the betic chain aquitanian northern africa langhian and the apennines late miocene pliocene we show that each of these events determines a major tectonic reorganization within the european plate

stress and palaeostress in the betic rif cordilleras miocene to the present palaeostress orientation in the betic rif cordilleras can be determined for the miocene to the quaternary by analysis of brittle microstructures faults joints striated pebbles and stylolites in the central and northern south iberian domain 1 was subhorizontal and trended nw se from the early miocene to the present in the northern alboran domain from the burdigalian to the serravallian palaeostress ellipsoids were oblate with 3 subhorizontal and trending ene wsw in the southern part of the south iberian domain and in the northern part of the alboran domain betic cordillera from the tortonian to the quaternary palaeostress ellipsoids were variable in the granada region they were prolate with 1 subvertical but in the almeria region they were triaxial with 2 subvertical and 3 subhorizontal and trending ne sw to e w in the rif the alboran and african maghrebian domains were affected by palaeostresses with 1 subhorizontal varying from ne sw in tortonian times to n s in the plio quaternary a study of earthquake focal mechanisms by the right dihedra method indicates that the present day general stress field around the betic rif cordilleras is compressional with 1 subhorizontal and trending nw se in the betic rif cordilleras this general stress field is modified and the present day orientations of 1 2 and 3 are nearly the same as those of the palaeostresses in the pliocene and quaternary the distribution and evolution of stresses in the betic rif cordilleras from the miocene to the present can be correlated with the main neogene deformations extensional structures in the central and northern alboran domain and the southern part of the south iberian domain and compressional structures in the south iberian and african maghrebian domains and in the southern part of the alboran domain

palaeoflood record of the tagus river central spain during the late pleistocene and holocene abstract palaeoflood hydrology of the tagus river central spain was reconstructed from slackwater deposits and palaeostage indicators in two canyon reaches located at el puente del arzobispo in the central part of the catchment 35 000 km 2 in drainage area and in alcantara at the lower part of the catchment 52 000 km 2 in drainage area near the portuguese border the palaeoflood record with more than 80 flood events shows clusters of floods at specific periods from 9440 to 9210 14 c yr bp 8540 8110 bc 8500 to 8000 14 c yr bp 7500 7000 bc 6750 14 c yr bp 5000 bc 1200 to 950 14 c yr bp ad 785 1205 410 14 c yr bp ad 1450 1500 170 to 80 14 c yr bp ad 1670 1950 the largest flood s occurred during the periods 9440 to 9210 14 c yr bp 6750 14 c yr bp and 1200 to 950 14 c yr bp reaching minimum discharge estimates of between 4000 and 4100 m 3 s 1 in the el puente del arzobispo reach and 13 700 15 000 m 3 s 1 in the alcantara reach these periods with increased flood magnitude and or frequency in the tagus river are strongly related to increased moisture influx and winter precipitation in the iberian peninsula especially in the western zone proxy records sensitive to winter precipitation such as lake levels and vegetation changes indicated by pollen records are in good agreement with the clusters of floods found in the tagus river this flood variability seems to correspond to changes in the prevailing atmospheric circulation pattern affecting the iberian peninsula

gravity anomalies and flexure of the lithosphere at mountain ranges the bouguer gravity anomaly over the himalayan alpine and appalachian mountains is characterized by a generally asymmetric gravity low which spans the mountains and associated foreland basins the minimum of the gravity low is generally systematically displaced from the region of greatest topographic relief and shows no obvious relationship to surface geology in addition the alps and appalachians are associated with a generally symmetric gravity high that is unrelated to the topographic relief together the gravity low and high form a characteristic positive negative anomaly couple the steep gravity gradient between the positive and negative couple correlates with the insubric line and its equivalents in the alps and the brevard zone in the southern appalachians this gravity anomaly couple is interpreted as evidence for flexure of the continental lithosphere by subsurface buried and surface topographic loading the magnitude of the subsurface load is estimated from the integrated excess mass represented by the positive anomaly and the magnitude of the surface load from the topography by combining these loads the flexure of the lithosphere and the associated bouguer gravity anomaly are calculated for different assumed values of the elastic thickness te of continental lithosphere the best fitting value of te for the himalayas is 80 100 km for the alps 25 50 km and for the appalachians 80 130 km the model calculations suggest that the main contribution to the gravity couple in the alps and appalachians arises not from surface loads such as thrust sheets and nappes but from subsurface loads however in the case of the himalayas the topography appears to be a sufficient load to explain the observed asymmetric gravity low when subsurface loads do exist therefore we would not expect a close correlation between mountain topographic relief and depth to the m discontinuity as required by classical models of isostasy rather the m discontinuity is expected to relate to the center of mass of all the loads acting on the lithosphere the surface and subsurface loads inferred from the gravity anomaly play a major role in the development of mountains and foreland basins the emplacement of large subsurface loads represents the primary event in the alps and appalachians while in the himalayas the emplacement of the surface load is the primary event the emplacement of the subsurface load probably marks the initiation of foreland basin development the regional characteristics of the basin are controlled by the primary load while local variations are controlled by the secondary thrust sheet loads subsequent movement of either load will produce migration of the basin depocenter the origin of the subsurface load is not clear but its association with the insubric line in the alps and the brevard zone in the appalachians suggests that it may be related to the obduction of crustal blocks flakes onto the underlying plate during continental collision or possibly to the preloaded crustal structure of the underlying plate

spatial and temporal variation of sublimation on antarctica results of a high resolution general circulation model in this paper we use output of a high resolution general circulation model echam 3 t106 resolution 1 1 x 1 1 to study the spatial and temporal variation of sublimation on antarctica first we compare model results with available observations of sublimation rates the yearly cycle with small latent heat fluxes during the winter is well reproduced and the agreement with sparsely available spot observations is fair the model results suggest that a significant 10 15 of the annual precipitation over antarctica is lost through sublimation and that sublimation plays an important role in the formation of blue ice areas a preliminary analysis of the atmospheric boundary layer moisture budget shows that the spatial variation of sublimation in the coastal zone of east antarctica can be explained by variations of horizontal advection of dry air dry air advection and thus surface sublimation is enhanced in areas where katabatic winds are strong and have a large downslope component and where the antarctic topography drops suddenly from the plateau to the coastal zone in areas where horizontal advection is small like the plateau and the large ice shelves special conditions must be met to make significant sublimation at the surface possible

morphological and sedimentary evolution of an alluvial floodplain in an urban area geoarchaeological approaches and applications tours france urban zones on alluvial plains offer considerable geoarchaeological potential for understanding river dynamics over large time spans and their relationship with land use because of the extensive subsoil data that is available in the alluvial plain of tours lying between the loire and the cher multidisciplinary studies of the relationships between societies and environment have been conducted as part of an archaeological research programme launched in the 1960s a sedimentary database containing data for 1309 surveys has been compiled and assembled in a geographic information system to produce geostatistical models of valley bottom geomorphology the stratigraphy and chronology of alluvial filling have also been studied with information and c14 and osl dating obtained during archaeological operations taken together the results offer a new interpretation of the morphological evolution of the alluvial plain of tours from the weichselian to the present day by providing new information that either validates or invalidates previous hypotheses bedrock incision prior to the end of the weichselian upper pleniglacial coarse sedimentation during the lateglacial relative morphological stability up to the late holocene the morphological context of the first human settlements which are not concentrated on the low alluvial reliefs and the role of urbanization conditions on the present morphology of the valley floor are also presented this applied study shows the relevance of combining different methodological approaches

cosmogenic 26al in the atmosphere and the prospect of a 26al 10be chronometer to date old ice abstract cosmogenic radionuclides in the one million year half life range offer unique possibilities for age determinations in geophysics in measurements where the radioactive decay is being utilized as a clock uncertainties in age determinations may be reduced if the ratio of two radioisotopes with different half lives can be used as a chronometer in this work we investigate the atomic ratio of atmospheric 26al t1 2 0 717 ma to 10be t1 2 1 386 ma measured with accelerator mass spectrometry ams and its potential as a chronometer for dating old ice the 26al 10be ratio decreases with an effective half life of t1 2 26al 10be 1 49 ma for its application as a chronometer the atmospheric 26al 10be ratio has to be well characterized however the properties of atmospheric 26al have been understood only poorly so far at the vera ams facility of the university of vienna a first systematic study of the global variations of the 26al 10be ratio in the atmosphere and in surface firn has been carried out and pilot measurements of the 26al 10be ratio in deep antarctic ice have been performed our results indicate that this ratio is globally constant to within 5 in the atmosphere and in surface firn with a mean value of 1 89 10 3 the data also suggest that non atmospheric sources of 26al such as extraterrestrial in situ produced or re suspended 26al do not contribute significantly to the observed 26al 10be ratio in addition atmospheric mixing seems to exert only a minor influence in a first application of the method 26al 10be ratios were measured in chips collected in connection with the drilling of the lowest part of an ice core 2250 to 2760 m in dronning maud land antarctica surprisingly variable 26al 10be ratios ranging between 0 5 and up to 2 times the atmospheric ratio were found at different locations in this deep ice core while the cause for the ratios higher than atmospheric remains unexplained so far the ratios lower than atmospheric may be caused by radioactive decay allowing a first dating attempt using the 26al 10be ratio thus at an ice depth of 2760 m an approximate date of 6 7 2 6 105 years was established

measuring gravity on ice an example from wanapitei lake ontario canada large lakes have always represented a problem for regional gravity databases the difficulty of access means gaps or coarse spacing in the sampling satellite airborne and shipborne gravity techniques are options but the resolution and or cost of these systems make them impractical or inaccurate for exploration or environmental studies where the required resolution is 0 1 mgal km in this study the feasibility of a ground gravity survey over a frozen lake where ice moves because of windy conditions is assessed lake wanapitei widely accepted as resulting from the impact of a meteorite 37 million years ago is one of these cases in which the necessity of expanding coverage over poorly sampled regions arose from a significant gap between surface and airborne geophysical maps two gravity surveys were completed on the ice of lake wanapitei in the winters of 2003 and 2004 to study the structure longtime series of gravity field measurements were recorded for 98 stations allowing for improved control over the noise sources in the data final processing and integration with an existing regional data set in the area and the application of terrain corrections reduced the amplitude of the circular anomaly from 15 to 9 mgal and its diameter from 11 to 6 km the feasibility of gravity surveys on ice was assessed and we determined that for large scale studies such as this one the quality of the data even under noisy conditions was acceptable however for more detailed mapping calm wind conditions and long time series are required

recent increase in south pole snow accumulation this paper summarizes the 37 year history of net accumulation measurements at the geographic south pole obtained by numerous investigators using a variety of techniques these data lead to the conclusion that annual net snow accumulation has increased in the vicinity of south pole station sps since 1955 the records were examined for evidence of a station effect and it is concluded that not all of the observed increase can be attributed to snow drift associated with the presence of the station furthermore the accumulation increase at the south pole appears consistent with increases observed at other locations on the east antarctic plateau and in the peninsula region as well these data suggest that the recent accumulation increase at sps may be regionally extensive over the east antarctic plateau

crustal thickness beneath libya and the origin of partial melt beneath as sawda volcanic province from receiver function constraints this study investigates crustal thickness and properties within the libyan region results obtained from 15 seismic stations belonging to the libyan center for remote sensing and space science are reported in addition to 3 seismic stations publically available using receiver functions the results show crustal thicknesses ranging from 24 km to 36 km with uncertainties ranging between 0 10 km to 0 90 km more specifically crustal thickness ranges from 32 km to 36 km in the southern portion of the libyan territory then becomes thinner between 24 km and 30 km in the coastal areas of libya and thinnest between 24 km and 28 km in the sirt basin the observed high vp vs value of 1 91 at one station located at the as sawda volcanic province in central libya indicates the presence of either partial melt or an abnormally warm area this finding suggests that magma reservoirs beneath the libyan territory may still be partially molten and active thereby posing significant earthquake and volcanic risks the hypothesis of an active magma source is further demonstrated though the presence of asthenospheric upwelling and extension of the sirt basin this study provides a new calculation of unconsolidated sediment layers by using the arrival time of the p to s converted phases the results show sediments thicknesses of 0 4 km to 3 7 km with the vp vs values ranging from 2 2 to 4 8 the variations in crustal thickness throughout the region are correlated with surface elevation and bouguer gravity anomalies which suggest that they are isostatically compensated

geoarchaeological alluvial terrace system in tarazona chronostratigraphical transition of mode 2 to mode 3 during the middle upper pleistocene in the guadalquivir river valley seville spain abstract a geoarchaeological study of some lithic assemblages found in late middle pleistocene and beginning upper pleistocene alluvial terraces system has been carried out the mis 6 mis 5 transition in the fluvial terraces of the guadalquivir river has been identified in the middle terraces complex mtc at tarazona t11 1 44 38 m and t11 2 36 30 m seville spain the results were obtained from an archaeological excavation tar iii and two other complementary archaeological sites tar i and tar ii geomorphological cartography chronostratigraphic study with osl dating cantometric analysis and technotypological characterization of 5870 lithic pieces measurement techniques for erosion and transport on gravels and lithic have been accomplished the alluvial chronosequence shows a probable climatic character with autocyclic sedimentary processes correlated with the transition from mis 6 to mis 5 four alluvial episodes with associated lithic techno complexes were identified which refer to the chronostratigraphic transition from mode 2 to mode 3 during the late middle pleistocene mis 6 and the beginning of upper pleistocene mis 5 episode 1 with mode 2 mis 6 episode 2 with varied assemblages that could be associated to mode 2 or mode 3 129 121 ka mis 5e and mis 5d pre 110 ka episode 3 with mode 3 between 110 and 104 ka mis 5c and episode 4 with mode 3 post mis 5c the archaeological sites have lithic pieces which were knapped in situ workshop habitual or temporary sites or were slightly displaced the raw material selection of high quality quartzites from alluvial deposits is very notable during mode 2 acheulian tar i2 mode 2 or mode 3 assemblages tar iii5 and mode 3 tar iii1 2 3 during mode 3 middle paleolithic tar ii1 the selection of flint raw material was from areas near or in the guadalquivir terraces

transfer zones in an oblique back arc basin setting insights from the latium campania segmented margin tyrrhenian sea new multichannel seismic reflection profiles were acquired to unravel the structure of a portion of the eastern margin of the tyrrhenian basin this extensional feature is part of an oligocene to present back arc basin in the hangingwall of the west directed apennines subduction system the basin provides excellent conditions to investigate the early stage processes leading to the development of rifted passive margins and to the emplacement of oceanic crust in an oblique setting the interpreted post stack migrated seismic profiles highlight the geometry and kinematics of the pontine escarpment that connects the latium campania continental margin to the vavilov basin the latter is the main feature of the area related to the early pliocene extension of the tyrrhenian sea several morphological variations are pointed out along strike mirroring different structural settings of the margin itself a steeper margin to the north corresponds to high angle possibly transtensional faults whereas a smooth slope in the southern portion corresponds to several more distributed listric faults this work contributes to the understanding of the interplay between extensional and transtensional tectonics along the margins of an oblique back arc basin

integrated crustal model beneath the po plain northern italy from surface wave tomography and bouguer gravity data abstract to obtain a 3 d crustal density and shear wave velocity structure beneath the po plain we exploit seismic records gathered from 2006 to 2014 and bouguer gravity data assembled for the last estimation of the italian geoid 2 d maps for both love and rayleigh fundamental mode at periods between 4 and 20 s are obtained applying a tomographic inversion the defined local dispersion curves are then jointly inverted using a linearized scheme to obtain a 3 d isotropic shear wave velocity model across the po plain region the model transformed into density through a priori velocity density relationships is then the input of the sequential integrated inversion algorithm which enables us to recover a new 3 d density shear wave velocity coupling and inferences on the lithology and tectonics low and fast s wave velocities are highlighted for the shallow pliocene quaternary sediments along the foredeep in front of the northern apennines and for the presence of limestone units in the upper crust respectively whereas sediment trends seem to be consistent with the results obtained the mesozoic carbonates which are inherently characterized by high variability are less resolved a major result is the recovery of a high speed 3 3 km s density 2 2 kg m3 structure in the upper crust 6 10 km localized beneath the arcuate po plain thrust front expanding from the external margin of the ferrara arc toward the alps and the adriatic sea at the boundaries of this brittle body we locate earthquakes of the emilia 2012 seismic sequence and the historical seismicity mapping lateral discontinuities in density and shear wave velocity could provide insights in defining strengthening and weakening zones and in focusing on transition zones often prone to earthquakes

factors determining subsidence in urbanized floodplains evidence from mt insar in seville southern spain major rivers have traditionally been linked with important human settlements throughout history the growth of cities over recent river deposits makes necessary the use of multidisciplinary approaches to characterize the evolution of drainage networks in urbanized areas since under consolidated fluvial sediments are especially sensitive to compaction their spatial distribution thickness and mechanical behavior must be studied here we report on subsidence in the city of seville southern spain between 2003 and 2010 through the analysis of the results obtained with the multi temporal insar mt insar technique in addition the temporal evolution of the subsidence is correlated with the rainfall the river water column and the piezometric level finally we characterize the geotechnical parameters of the fluvial sediments and calculate the theoretical settlement in the most representative sectors deformation maps clearly indicate that the spatial extent of subsidence is controlled by the distribution of under consolidated fine grained fluvial sediments at heights comprised in the range of river level variation this is clearly evident at the western margin of the river and the surroundings of its tributaries and differs from rainfall results as consequence of the anthropic regulation of the river on the other hand this influence is not detected at the eastern margin due to the shallow presence of coarse grain consolidated sediments of different terrace levels the derived results prove valuable for implementing urban planning strategies and the insar technique can therefore be considered as a complementary tool to help unravel the subsidence tendency of cities located over under consolidated fluvial deposits

neogene evolution of the sorbas basin se spain determined by paleostress analysis abstract the neogene subsidence history of the sorbas basin situated in the internal zone of the betic cordilleras of southeastern spain is strongly controlled by strike slip deformation the sedimentary sequence of the basin offers a good control on the timing of separate phases of fault activation the southern border of the sorbas basin is formed by a major east west trending fault zone the gafarillos fault zone which consists of intermixed slivers of pre neogene basement blocks and neogene basin sediments fault patterns and paleostress analysis both indicate that major displacement along this fault zone was dextral with a n310e oriented maximum principal stress axis strike slip movement along the east west oriented faults ended during the earliest messinian after a minimum of 6 ma of activation paleostress analysis indicates a subsequent phase of strike slip fault movement present in sites of up to early pliocene age the maximum principal stress axis orientation is n350e for this phase this deformation is synchronous with sinistral displacement along the palomares fault zone situated directly to the east of the study area subsequently our paleostress analysis indicates an extensional regime during the late pliocene to quaternary however extensional tensors were calculated at a number of sites possibly representing local stress regimes coexisting with the main strike slip deformation and sorbas basin subsidence folding of tortonian sediments points out that local compressional deformation took place as well during the neogene basin history observed wide ranges for the ellipsoid shapes of the calculated tensors support the existence of lateral stress variations

a deterministic approach toward isostatic gravity residuals a case study from south america a new deterministic method for correcting isostatic effects in gravity data sets overcomes the deficiencies of empirically based methods this technique produces a superior gravity image for south america and has application to other continental scale gravity data sets the basis for the correction is the airy heiskanen isostatic model which assumes that surface topography is supported by crustal thickening the three key parameters 1 the crustal thickness at sea level 2 the surface reduction density and 3 the density contrast between the crust and the mantle are determined directly from the elevation free air gravity and bouguer gravity data sets the surface density parameter of 2 60 g cc is determined using a new fractal technique this technique assumes that the topography is fractal the best value for density is that which minimizes the fractal component caused by topographic effects the new value is substantially different than the 2 67 g cc density assumed by many previous workers for most continental scale data sets the crust mantle density contrast parameter of 0 45 g cc is determined by comparison between the densities determined from crossplots of the bouguer values versus elevation the crustal thickness parameter of 30 km is determined using a spectral method applied to the free air gravity the results of this work are not only an isostatic residual map but a methodology that cross checks the data for quality control the final isostatic residual map can be used with confidence for basin evaluation throughout the continent of south america basins at high elevations like the eastern foreland basins of the andes and the altiplano basin are imaged better by using this method

the deformation of aegea a finite element study abstract the concentration of extension in southern aegea is a consequence of the velocities imposed along the boundaries of this region this result is demonstrated by using the finite element method and velocities derived independently from the kinematics of the hellenic subduction zone and that of the north anatolian fault the thinning of the lithosphere resulting from this extension is in good agreement with that required to explain the aegean subsidenceand the forces along the boundaries are approximately normal to the aegean arc neotectonic data agree with these results

statistical analysis of lateral migration of the rio grande new mexico abstract the lateral migration rates of alluvial rivers are affected by changes in water and sediment regimes the rio grande downstream from cochiti dam exhibits spatial and temporal variability in lateral movement rates documented since 1918 a tremendous database exists that documents planform bed material size channel geometry and water and sediment regimes a statistical analysis reveals that migration rates primarily decreased with decreasing flow energy r2 0 50 p 60 the findings show that lateral movement increases with increasing flow energy and with degree of braiding

determining the optimal bouguer density for a gravity data set implications for the isostatic setting of the mediterranean sea summary we have used free air gravity satellite data from geosat and ers 1 missions to compile a bouguer gravity map of the mediterranean sea the complete bouguer correction has been applied by using the method of parker that acts in the fourier domain and permits the exact evaluation of the gravity contribution from an highly sampled topographic model of the land the density used for the bouguer reduction has been obtained from the gravity data set itself by using two different optimization methods that have given the same optimal result of 2400 kg m 3 we have studied the radial power spectrum of the data choosing the optimal bouguer density from its slope as the one which minimizes the fractal dimension of the resulting gravity map the second approach consists of studying the correlation between topography and bouguer anomaly by spatial cross plots for a significant subset of the data both these approaches are aimed at reducing the short wavelength effects of topography in the gravity map but in the past they have been traditionally used alternatively since they gave different optimization values especially the second method that seems to ignore large wavelength isostatic effects actually we have revisited both the methodologies proposing slight modifications to make their efforts compatible their coincident results confirm their validity of application and give reliability to the recovered value of the bouguer optimal density moreover modifying the second approach allows us to compile a sort of normalized correlation map which we propose in this paper defining the 2 d isostatic setting of the investigated region without introducing any further lithospheric model the final result is a revised bouguer map compiled using a grid with a resolution of 2 min that is useful for large scale geological studies and gives important information about the compensation mechanism of the mediterranean sea in a direct way we have found that the overall region seems to be in a complete isostatic equilibrium apart from the young basins of tyrrhenian sea and aegean sea confirming previous similar results

geoarchaeology in a meandering river a study of the bk site 1 35 ma upper bed ii olduvai gorge tanzania abstract bk site hosts 8 archaeological levels preserved inside the channel of a meandering river this river is not found in a floodplain but encased in a wide karstified carbonate surface with no edaphic development the river at bk has been recurrently used by hominins for carcass processing in the river channel coinciding with a high concentration of vegetation and water resources along the channel banks the spatial distribution of the different archaeological levels is the result of a complex sedimentary record such complexity in meandering river deposits is due to processes such as erosion transport and sedimentation occurring simultaneously and coarse and very fine sediments being deposited at the same time throughout the same isochronal surface bk site offers a unique opportunity thanks to its abundance in archaeological remains and the quality of the outcrop to geoarchaeologically depict and describe an archaeological site in a meandering channel the geology of this fluvial environment is considered regarding a fluvial architecture b facies distribution and c fluvial dynamics furthermore the abundance of archaeological remains and megafauna found inside the channel at bk contrasts with the absence of any remains outside the channel we hypothesize that this area was preferred by hominins since it offers a high concentration of water resources and vegetation as well as a greater protection against predators than an open plain a detailed reconstruction of the paleolandscape will try to uncover the reason behind the huge contrast existing between the abundance of remains found inside and outside the channel leading to the interpretation that an ecological or landscape related factor is conditioning the location and formation of the archaeological assemblage

satellite gravity enhancements from new satellites and new altimeter technology abstract this paper reviews the impacts of new satellite altimeter data sets and new technology on the production of satellite gravity it considers the contribution of the increased data volume the application of new altimeter acquisition technology and the potential for future developments satellite altimeter derived gravity has provided gravity maps of the world s seas since the 1980s but from 1995 to 2010 virtually all improvements were in the processing as there were no new satellite data with closely spaced tracks in recent years new data from cryosat 2 launched in 2010 and the geodetic mission of jason 1 2012 2013 have provided a wealth of additional coverage and new technology allows further improvements the synthetic aperture radar mode of cryosat 2 uses a scanning approach to limit the size of the altimeter sea surface footprint in the along track direction tests indicate that this allows reliable data to be acquired closer to coastlines the synthetic aperture radar interferometric mode of cryosat 2 uses two altimeters to locate sea surface reflection points laterally away from the satellite track in a study to generate gravity for freshwater lakes this mode is found to be valuable in extending the available satellite coverage the altika altimeter uses higher frequency radar to provide less noisy sea surface signals and its new orbit mode gives potential for further improvements in satellite gravity future developments include the potential for swath mapping to provide further gravity improvements

gravity data inversion for moho depth modeling in the hellenic area the main objective of this study is the determination of the moho discontinuity in the hellenic area based on gravity data inversion high resolution 2 arcmin and accuracy 2 to 3 mgal gravity data were used in the computations following the parker oldenburg iterative method and a low pass filter was applied to gravity information towards the convergence of the final solution to determine the cut off wavenumber of the filter we tested different mean depths and density contrasts of the crust and the mantle mohorovicic discontinuity the selected density contrast and mean depth of the mohorovicic discontinuity are those which agree with the moho depth interpreted from deep seismic imaging data by comparing the moho depth estimated covering both land and marine areas and including the ionian and aegean sea with those interpreted from previous studies it is shown that our solution is consistent with the available seismic data interpretation moreover the resolution of the gravity data and the appropriate filtering used in this study contributed to the representation of local features of the moho discontinuity finally area dependent discrepancies detected between the moho depths of the current solution and those derived from previous studies are extensively discussed

predicting gully width and widening rates from upstream contribution area and rainfall a case study in sw spain abstract gully width w is usually characterized by having a power relation with discharge however calculating runoff discharge in ungauged basins where these gullies typically form is inherently difficult and associated with large uncertainties this paper examines a simplified approach to relating gully width directly to the runoff contributing area a in a cultivated area in sw spain the effect of rainfall and land use on this w a relation was also analysed gully width was measured in 46 sections through the analysis of 10 historical orthophotos between 1956 and 2013 in a 21 km2 catchment in s spain these were validated by field measurements in 2013 widening rates varied strongly over time at between 0 and 2 19 m year 1 no significant differences in the gully widening rates were found between the two land uses present in the study zone olive groves and herbaceous crops the data obtained show a significant power relation of the form w a for all time periods analysed except for 1980 when many gullies were filled in artificially due to a change in land use in the study area the power relation coefficient varied at between 0 2 and 0 3 a good correlation was obtained between the number of days with daily rainfall of above 13 mm and the increase in the coefficient over time the results of this study on gully width dynamics provide new insights into improving the estimation of gully volume for example in combination with gully headcut retreat models and including the effects of different climate scenarios

channel changes in the jarama and tagus rivers central spain over the past 500 years abstract long term channel changes of the tagus and the jarama rivers in central spain were studied in relation to variations in hydroclimatic factors such as rainfall and flooding and also with respect to human activities undertaken in their valleys data were taken from historical 1580 1823 and topographical 1877 1988 maps as well as aerial photographs 1945 1999 the available hydroclimatic data consists of a series of monthly rainfall totals 1859 1994 and mean river flow values recorded at gauging stations 1911 1985 in addition a historical flood record 1550 1947 was produced from documentary sources some of the data was incorporated into a geographical information system gis to quantify the changes in the course of the rivers the results show there have been two distinct periods before and after human intervention in the river system which took place around 1950 during the earlier period 1550 1950 a correlation exists between climate frequency and magnitude of flooding and changes in fluvial geomorphology between 1860 and 1892 an increase in flood frequency and magnitude occurred which produced half of the cut offs recorded in the study area between 1823 and 1877 the meanders length l width w and radius of curvature rc of the tagus river have decreased since 1750 however those of the jarama reached their maximum values during flood periods both rivers have different geomorphological responses during flood events which can explain these different trends floods in the jarama not only led to the cut offs but also enlarged the channel size l w and rc in the second period 1956 present flow regulation via dams and gravel mining modified the system completely and impeded the natural development of these rivers

isostatic response of the australian lithosphere estimation of effective elastic thickness and anisotropy using multitaper spectral analysis gravity and topography provide important insights regarding the degree and mechanisms of isostatic compensation the azimuthally isotropic coherence function be tween the bouguer gravity anomaly and topography evolves from high to low for increasing wavenumber a diagnostic that can be predicted for a variety of lithospheric loading models and used in inversions for flexural rigidity thereof in this study we investigate the isostatic response of continental australia we consider the effects of directionally anisotropic plate strength on the coherelce the anisotropic coherence function is calculated for regions of australia that have distinctive geological and geophysical properties the coherence estimation is performed by the thomson multiple slepian taper spectral analysis method extended to two dimensional fields our analysis reveals the existence of flexural anisotropy in central australia indicative of a weaker n s direction of lower te this observation is consistent with the suggestion that the parallel faults in that area act to make the lithosphere weaker in the direction perpendicular to them it can also be related to the n s direction of maximum stress and possibly the presence of e w running zones weakened due to differential sediment burial rates we also demonstrate that the multitaper method has distinct advantages for computing the isotropic coherence function the ability to make many independent estimates of the isostatic response that are minimally affected by spectral leakage results in a coherence that is more robust than with modified periodogram methods particularly at low wavenumbers our analysis elucidates the reasons for discrepancies in previous estimates of effective elastic thickness te of the australian lithosphere in isotropic inversions for te we obtain values that are as much as a factor of 2 less than those obtained in standard inversions of the periodogram coherence using bouguer gravity and topography but greater than those obtained by inversions that utilize free air rather than bouguer gravity and ignore the presence of subsurface loads however owing to the low spectral power of the australian topography the uncertainty on any estimate of te is substantial

when did sardinia stop rotating new palaeomagnetic results previous palaeomagnetic results from tertiary volcanic rocks of sardinia suggest that the island underwent a quick counterclockwise rotation between 20 5 and 19 ma in order to test this hypothesis a new palaeomagnetic study was carried out on sediments and volcanic rocks with well controlled biostratigraphic or radiometric ages younger than the suggested age for the end of the rotation unrotated palaeomagnetic directions obtained from the upper ignimbrites radiometric age 18 5 19 7 myr and the aquitanian tuffs collected in the anglona region n sardinia would suggest that the rotation ended earlier than 20 5 myr the directions found in the volcanics are perhaps the result of secular variation rather than differential rotation of the anglona region with respect to surrounding regions two sites belonging to the upper ignimbritic unit si2 in the monte traessu monte rispisu area logudoro region exhibited a large amount of rotation d 320 4 i 60 which may be age related radiometric age 19 9 myr four dikes radiometric age 18 3 16 7 myr in the arcuentu volcanic complex arburese region yield results d 348 4 i 33 8 that indicate a further amount of rotation after their emplacement stable end point directions were successfully isolated from three upper burdigalian langhian sedimentary sites biostratigraphic age 18 15ma from the marmilla and logudoro regions consistent paleomagnetic directions obtained from these sites d 352 i 49 indicate that a small amount of rotation was still to be completed in the langhian time this result is consistent with the history of sardinian volcanism which did not end until 13 ma

climatic and glaciological information inferred from air content measurements of a law dome east antarctica ice core the total air content v of ice has been measured along the dome summit south dss core from law dome east antarctica the main features of this record are the very well preserved sub annual fluctuations of v down to at least 900 m depth and the significant increase of the v values during the last deglaciation the sub annual variations reflect changes in close off porosity and we interpret the v seasonal peaks as tracers of depth hoar layers for the longer time scale the large v fluctuations observed are interpreted in terms of elevation and or close off porosity changes under different assumptions we analyze the possible influence of a different global pressure field and or a change in seasonal temperature and precipitation cycles during the last glacial period our estimates of surface elevation changes derived from the v data are then compared with independent reconstructions of past elevations

advances in gravity survey resolution major technological advances have been made in the last few years in gravity resolution for many acquisition systems currently available for exploration these advances have resulted from better instrumentation better use of dgps and better processing methods this in turn led to a renaissance in the use of gravity in modern multidisciplined cost effective oil and mineral exploration the aim of this article is to show how gravity resolution has improved with time rather than how improved resolution is being used to investigate and map subsurface density structures

global marine gravity field from the ers 1 and geosat geodetic mission altimetry satellite altimetry from the geosat and the ers i geodetic missions provide altimeter data with very dense spatial coverage therefore the gravity field may be recovered in great detail as neighboring ground tracks are very closely distributed cross track variations in the sea surface heights are extremely sensitive to sea surface variability to avoid errors in the gravity field caused by such effects sea surface variability needs to be carefully eliminated from the observations initially a careful removal of gross errors and outliers was performed and the tracks were fitted individually to a geoid model and crossover adjusted using bias and tilt subsequently sea surface heights were gridded using local collocation in which residual ocean variability was considered the conversion of the heights into gravity anomalies was carried out using the fast fourier transform fft in this process filtering was done in the spectral domain to avoid the so called orange skin characteristics comparison with marine gravity was finally carried out in three different regions of the earth to evaluate the accuracy of the global marine gravity field from ers 1 and geosat

a new isostatic residual gravity map of the conterminous united states with a discussion on the significance of isostatic residual anomalies to display more clearly the gravity anomalies caused by geologic bodies in the upper parts of the crust a new colored isostatic residual gravity map of the conterminous united states has been prepared using the gravity data set compiled for the gravity anomaly map of the united states society of exploration geophysicists 1982 the new isostatic residual gravity map is based on an airy heiskanen model of local compensation in which the surface load requiring compensation is defined by 5 min topographic and bathymetric data sets a colored first vertical derivative map of isostatic residual gravity further enhances the short wavelength anomalies produced by bodies at or near the surface and emphasizes the regional fabrics and trends in the gravity field for the purpose of displaying gravity anomalies caused by shallow bodies of geologic significance the nature of the isostatic model and the values of its parameters are of lesser importance than the application of an isostatic correction of some sort most isostatic models result in residual gravity maps that appear nearly identical in their main patterns and features anomalies on isostatic residual gravity maps should not be casually interpreted in terms of undercompensation or overcompensation because large amplitude anomalies can be produced by crustal bodies in complete local isostatic equilibrium many isostatic residual gravity anomalies less than several hundred kilometers wide can be related to known geologic bodies we present here a classification scheme that attempts to categorize such anomalies on the basis of tectonic environment in general highs correlate with intruded or accreted mafic material or with upthrusted crustal sections whereas lows occur over low density sedimentary or volcanic sections felsic intrusive bodies or down warped crustal sections although some longer wavelength anomalies such as the broad gravity high centered over montana could be manifestations of density contrasts deep in the mantle many such anomalies can also be modeled by geologically reasonable density contrasts that are isostatically compensated and confined to depths of less than several hundred kilometers so that their source bodies need not be deep the fact that certain of these broader anomalies have well defined boundaries which correlate with near surface geologic features increases the likelihood that their sources lie entirely within the lithosphere if so then the density contrasts required to explain the gravity data imply fundamental anomalies in chemical composition or thermal state for the crustal and upper mantle columns under these regions we have investigated spectral analysis as a method to quantitatively characterize regional anomaly patterns contoured plots of normalized amplitude spectra were prepared for various areas of the isostatic residual gravity field of the united states these fourier domain representations show characteristic patterns that can be interpreted in terms of the trends and wavelengths of anomalies and may help to more objectively distinguish geologic basements with different origins or tectonic histories

bouguer reduction density why 2 67 one of the most widely recognized parameters in solid earth geophysics is the assumed density of the surface rocks of the continental crust 2 67 g cm 3 or 2670 kg m 3 in today9s preferred si units in the calculation of bouguer and isostatic gravity anomalies which are widely used for geological studies the gravitational effect of the earth mass between an observation site and a datum is calculated assuming an infinite flat slab of a specified density that approximates the mass the datum for most surveys is sea level or in the case of surveys of limited areas it may be the elevation of the lowest station in the survey although the choice of datum is arbitrary commonly sea level is used in an attempt to standardize anomalies from different surveys similarly a density of 2 67 g cm 3 is generally assumed for the density of the included mass in regional gravity surveys

palaeogene evolution of deformation in the northeastern iberian peninsula during the palaeogene alpine compression three units were differentiated in the studied area south of the ebro basin the catalan coastal range dominated by ne sw major basement faults with a sinistral movement the iberian range where the important basement faults have a nw se direction and a reverse movement often with a dextral component the linking zone between these two ranges where an e w dominant structural direction is marked by an array of folds and thrusts with a northward vergence in the mesozoic cover from the analysis of both these major structures and the small scale structures it can be deduced that the compression in the studied area has evolved from a nw se direction lower middle eocene to a n s direction and to a ne sw one uppermost oligocene the major structures are due to the n s compression later the stress field progressively changed to a distensive regime we suggest a relation between the compressive phases and the displacement direction of the iberian plate with reference to the european plate

sensitivity of gravity and topography regressions to earth and planetary structures abstract the availability of global gravity fields and topography through calculation services like the international centre for global earth models allows easy access to gravity data greatly enlarging the spectrum of users the applications extend much farther than the classic modeling through the gravity specialist we investigate the sensitivity of the joint analysis of topography and gravity data based on linear regression analysis and clustering of the response to particular characteristics of the lithosphere structure the parameters of the regression analysis are predicted to have characteristic values which allow to distinguish continental crust from oceanic crust and signalize the presence of crustal inhomogeneity predictions are made through theoretical considerations and on synthetic models we use the south atlantic ocean and the confining south american and african continents for illustration where the regression parameters distinguish oceanic crust from the ridge up to the bathymetric inflection point from the transitional crust and the continental crust allowing to map these units the general properties of the parameters are statistically relevant since the errors on the parameters are

the effect of temporal variations in the surface mass balance and temperature inversion strength on the interpretation of ice core signals the proxy for temperature signal in ice cores is stored in the snow ice during precipitation events and hence reflects the temperature at which precipitation is formed here approximated by the inversion temperature t weighted with the accumulation results from a 14 year integration 1980 93 with a regional atmospheric model racmo x 55 km show that the annual mean accumulation weighted inversion temperature t i w and the annual mean t i are not covariant in time at four out of the five deep drilling sites considered mainly due to year to year variations in the seasonality of precipitation as a consequence the surface temperature t s core derived from racmo output using a method analogous to the retrieval of the surface temperature from ice core signals deviates from the directly modelled surface temperature t s on interannual time scales results from a 5 year sensitivity integration forced with a 2 k temperature increase show an 18 overestimation of the increase in t s core relative to the increase in t s due to a change in the relationship between the inversion strength and the surface temperature in a different climate regime similar errors may occur in deriving the temperature difference between last glacial maximum and present day climate from signals in ice cores

urban geo archaeology in medieval alzira prov valencia spain abstract alzira is situated in a cut off meander loop of the rio jucar geo archaeological study shows that the islamic city wall was built during the second quarter of the 11th century ad at a time when the river had a low amplitude and low energy flood regime after mid century overbank silts began to invade the city as peak flood discharge increased with a spate of destructive floods reflected by high energy deposits during the late 11th century urban expansion within the city wall is dated to the later 11th or early 12th century interrupted by local abandonment and moderate energy flood silts major construction during the mid 12th century was followed by protracted abandonment after a siege in ad 1171 and further moderate energy flood silts that redistributed occupation and collapse debris reoccupation during the late 14th century was terminated by catastrophic floods in 1517 and 1571 after which much of the western end of alzira was not rebuilt following further flood catastrophes during the 17th century parts of the central walled city remained abandoned until the 19th century with new occupation atop flood sands of yet another disaster in 1864 the change in flood regime after 1150 was a result of deforestation of the watershed but progradation of a downstream tributary fan after 1517 created an unstable aggrading floodplain increasingly prone to severe flooding climatic anomalies were responsible for periods of recurrent severe floods archaeologically verified during the 11th and 12th centuries and historically documented beginning in 1318 the geo archaeological methodology illuminates the constructional and settlement history of alzira allows distinction of fluvial and cultural components and provides the necessary microstratigraphic detail and dating control to document the true complexity of alluvial processes during the last 1000 years

flexural behavior of the continental lithosphere in italy constraints imposed by gravity and deflection data a procedure is developed that systematically matches observations of plate flexure and gravity anomalies at simple convergent boundaries to the bestfitting two dimensional flexural geometry obtained by a thin elastic sheet of specified elastic strength the procedure allows analytical solution for three independent variables one of which is the initial preflexure elevation of the reference surface and two of which are related to the vertical forces and bending moments that act on the plate application to four profiles constructed across the apennine convergent system in italy shows that the observed depth of the basal pliocene surface which marks the base of the foredeep basin and the observed bouguer gravity anomalies can be fit by a two dimensional elastic plate model with an effective elastic thickness of about 20 km on three profiles and about 10 km on the fourth profile the initial elevation prior to flexure is determined to have been about 1000 m below sealevel on all profiles large bending moments and or vertical shear forces are required to act at the effective plate ends in order to maintain the observed deflection moments between 0 5 1017 and 3 1017 n and shear forces between 3 1012 and 3 1012 n m gravity modelling indicates that on the two northernmost profiles these terminal forces can not be supplied by a static mass at crustal depths and suggests that on all four profiles the terminal forces are supplied by anomalously dense material present at depths of 75 150 km beneath and west of the west coast of italy this dense material probably corresponds to westward subducted lithosphere of the adriatic plate extending from the northern apennines to the southern apennines and calabria this study suggests that in subduction systems like the apennines that are characterized by backarc extension forces acting on subducted lithosphere at depth can be expressed at the surface in the geometry of the foredeep basin that forms adjacent to the subduction zone

effect of the lateral topographic density distribution on interpretational properties of bouguer gravity maps until recently the information about the topographic density distribution has been limited to only certain regions and some countries while missing in the global context the unb topodens is the first model that provides the information about a lateral topographic density globally the analysis of this model also reveals that the average topographic density for the entire continental landmass excluding polar glaciers is 2247 kg m 3 this density differs significantly from the value of 2670 kg m 3 that is typically adopted to represent the continental upper crustal density in this study we use the unb topodens density model to inspect how the topographic density variations affect interpretational properties of bouguer gravity maps since this model provides also the information about density uncertainties of individual lithologies main rock types we estimate the corresponding errors in the bouguer gravity data despite a new estimate of the average topographic density corresponds to relative changes of 16 per cent in values of the topographic gravity correction these changes do not affect interpretational properties of bouguer gravity maps the anomalous topographic density distribution taken with respect to the average density of 2247 kg m 3 however modifies the bouguer gravity pattern we demonstrate that the gravitational contribution of anomalous topographic density is globally mostly within 25 mgal but much large values are detected in himalaya tibet central andes and along the east african rift system our estimates also indicate that errors in the bouguer gravity data attributed to topographic density uncertainties are mostly less than 15 mgal but in mountainous regions could reach large values exceeding even 50 mgal unarguably the unb topodens model provides an improved information about the global topographic density variations and their uncertainties nevertheless much more in situ measurements of rock density samples together with detailed 3 d geological models are still necessary to understand better the actual density distribution within the whole topography particularly to mention a density change with depth

fracture zones in the north atlantic from combined geosat and seasat data we present a new tectonic fabric map of the northern and central north atlantic ocean floor from 10 s to 66 n based on combined geosat and seasat altimetry data short wavelength vertical gravity along track was derived by hilbert transforming and high pass filtering geosat and seasat deflection of the vertical profiles the along track gravity data were used in conjunction with magnetic anomaly data to locate a large number of fracture zones as well as extinct spreading ridges and v shaped structures we traced many fracture zones more continuously and closer to adjacent continental margins than was previously possible we also mapped a number of unnamed fracture zones and fracture zone segments many of which were previously uncharted we have evaluated the agreement between the mapped fracture zones and synthetic flow lines as predicted from recent plate models for the opening of the north central north and south atlantic most fracture zones in this area correlate quite well with synthetic flow lines supporting the proposition that geosat seasat altimetry data serve as a useful tool to map fracture zones where insufficient bathymetric data are available many fracture zones including some small offset fracture zones in the central north atlantic have been stable and follow tectonic flow lines for tens of millions of years however many other fracture zones do not reflect a railroad track pattern of plate motions the geometry of many small and medium offset fracture zones indicates that the ridge axis discontinuities that produce them can migrate along the ridge causing off axis traces that deviate from tectonic flow lines velocity space diagrams constructed using a recent relative and absolute present day plate motion model indicate that some low angle v shaped troughs and ridges are likely formed by migration of the plate boundary relative to a mesospheric reference frame other low angle v shaped structures reflect slow migrations oscillations of small offset ridge axis discontinuities that are distinct from both tectonic flow lines and v shapes reflecting absolute plate motions high angle v shaped structures are the result of fast migrating ridge axis discontinuities propagating rifts

what are the limitations of satellite altimetry radar altimeter measurements of the marine geoid collected during the seasat altimeter mission gave geophysicists hope of uncovering the gravity field over all the ocean basins however because of insufficient track density it has taken 16 years for the full potential of the satellite altimeter to be realized the high density coverage obtained by ers 1 during its geodetic mapping phase april 1994 march 1995 prompted the u s navy to declassify all of the geosat altimeter data in june 1995 the combination of these two high density data sets provided the first global view of all the ocean basins at a wavelength resolution of 20 30 km

crossing forest thresholds inertia and collapse in a holocene sequence from south central spain a holocene palaeoecological sequence from villaverde south central spain is presented the pollen stratigraphy is used to infer past vegetation changes within a catchment area that represents the boundary between semi arid plateau and mountain vegetation from c 9700 7530 cal yr bp pinus is dominant probably as a result of a combination of a relatively dry climate and natural fire disturbance from c 7530 5900 cal yr bp moderate invasion by quercus appears to be a migrational response following increased moisture and temperature but in part shaped by competitive adjustments from c 5900 5000 cal yr bp the pine forests are replaced by deciduous quercus forests with an important contribution from corylus betula fraxinus and alnus mediterranean type forests spread from c 5000 to 1920 cal yr bp coincident with expansions of artemisia juniperus and other xerophytes from c 1920 1160 cal yr bp pinus becomes dominant after a disturbance mediated invasion of the oak forests human impact u

ground based measurements of spatial and temporal variability of snow accumulation in east antarctica the east antarctic ice sheet is the largest highest coldest driest and windiest ice sheet on earth understanding of the surface mass balance smb of antarctica is necessary to determine the present state of the ice sheet to make predictions of its potential contribution to sea level rise and to determine its past history for paleoclimatic reconstructions however smb values are poorly known because of logistic constraints in extreme polar environments and they represent one of the biggest challenges of antarctic science snow accumulation is the most important parameter for the smb of ice sheets smb varies on a number of scales from small scale features sastrugi to ice sheet scale smb patterns determined mainly by temperature elevation distance from the coast and wind driven processes in situ measurements of smb are performed at single points by stakes ultrasonic sounders snow pits and firn and ice cores and laterally by continuous measurements using ground penetrating radar smb for large regions can only be achieved practically by using remote sensing and or numerical climate modeling however these techniques rely on ground truthing to improve the resolution and accuracy the separation of spatial and temporal variations of smb in transient regimes is necessary for accurate interpretation of ice core records in this review we provide an overview of the various measurement techniques related difficulties and limitations of data interpretation describe spatial characteristics of east antarctic smb and issues related to the spatial and temporal representativity of measurements and provide recommendations on how to perform in situ measurements

gravity constraints on the dynamics of the crust mantle system during calabrian subduction summary the thermomechanic evolution of the lithosphere upper mantle system during calabrian subduction is analysed using a 2 d finite element approach in which the lithosphere is compositionally stratified into crust and mantle gravity and topography predictions are cross checked with observed gravity and topography patterns of the calabrian region modelling results indicate that the gravity pattern in the arc trench region is shaped by the sinking of light material belonging to both the overriding and subduction plates the sinking of light crustal material up to depths of the order of 100 150 km is the ultimate responsible for the peculiar gravity signature of subduction characterized by a minimum of gravity anomaly located at the trench bounded by two highs located on the overriding and subducting plates with a variation in magnitude of the order of 200 mgal along a wavelength of 200 km in agreement with the isostatically compensated component of gravity anomaly observed along a transect crossing the calabrian arc from the tyrrhenian to the ionian seas the striking agreement between the geodetic retrieved profiles and the modelled ones in the trench region confirms the crucial role of compositional stratification of the lithosphere in the subduction process and the correctness of the kinematic hypotheses considered in our modelling that the present day configuration of crust mantle system below the calabrian arc results from trench s retreat at a rate of about 3 cm yr 1 followed by gravitational sinking of the subducted slab in the last 5 myr

effects of seasonal variability of accumulation on yearly mean δ18o values in antarctic snow the annual mean oxygen isotope content of antarctic snow is strongly influenced by the seasonal variability ofaccumulation since the annual mean 18 o value is frequently used to derive mean annual temperatures from ice cores changes in atmospheric circulation pattern can lead to large errors in the deduced temperature record at the german antarctic wintering base neumayer accumulation measurements have been carried out continuously over the last 16 years weekly readings of accumulation stakes combined with snow pits and shallow firn cores are used to investigate the influence of the seasonal variability of accumulation on the annual mean 18 o values and to estimate the possible error in the determination ofannual mean temperatures from ice cores by using the oxygen isotope record

temporal variability of accumulation at neumayer station antarctica from stake array measurements and a regional atmospheric model in this study we investigate the ability of the regional atmospheric model racmo to represent temporal variations of antarctic accumulation using weekly stake array measurements from neumayer station the model uses ecmwf reanalyses data to force the atmospheric variables at the lateral boundaries of the model domain accumulation is defined as precipitation minus sublimation generally the model represents the synoptic situations that lead to precipitation reasonably well the amounts of accumulation are however usually lower in the model than in the measurements it cannot be distinguished whether the model underestimates precipitation or whether this effect is due to the redistribution of snow by the wind which is not taken into account in the model but affects the accumulation at the measuring site significant differences between model and measurements also occur in cases of net ablation due to wind erosion or when accumulation was due to snowdrift from southwest without precipitation observed

the graham and terrible volcanic province nw sicilian channel gravimetric constraints for the magmatic manifestations a few kilometres off the sw coast of sicily lie the shallow banks of graham terrible and nerita these morphological reliefs are affected by two lithospheric scale n s trending tectonic lineaments known as capo granitola to the west and sciacca to the east within the graham and terrible banks several volcanic edifices have been documented and mapped using high resolution bathymetry and seismic profiles three groups of volcanic features can be distinguished i a cluster of n s aligned volcanic cones in the graham bank generally developed along the capo granitola fault ii a series of poorly developed volcanic constructs roughly positioned along the northern edge of the terrible bank and iii a few isolated volcanic centres located north of the terrible bank within an undeformed zone here we present a 2 d gravimetric model constrained at shallow levels by an integrated seismic dataset which we use to interpret the distribution of magmatic manifestations in this sector of the sicilian channel at the graham bank where there are no significant positive gravity anomalies the magmatic material seem to migrate to the surface along the capo granitola lithospheric fault without the presence of a shallow magma source in the terrible bank where there is a well defined positive gravity anomaly the model implies the presence of a shallow magma chamber from which sea floor volcanic constructs are fed upwards along cracks the origin for the volcanic cones located between the two fault systems is more problematic as no significant structural discontinuities were identified in this area from the available seismic data however the presence of a potential wide sill complex suggests that it facilitated lateral magma flow from source to surface over lateral distances of tens of kilometres

the combined inversion of seismological and goce gravity data new insights into the current state of the pacific lithosphere and upper mantle abstract in this study we combine seismological and goce satellite gravity information by using a bayesian like technique with the aim of inferring the density structure of the pacific 90 n 90 s 121 e 60 w lithosphere and upper mantle we recover a 1 1 3 d density model down to 300 km depth which explains gravity observations with a variance reduction of 67 41 the model with an associated a posteriori standard deviation provides a significant contribution to understanding the evolution of the pacific lithosphere and answers to some debated geodynamic questions our methodology enables us to combine the recovery of density parameters with the optimum density v sv scalings the latter account for both seismological and gravity observations in order to identify the regions characterized by chemically induced density heterogeneities which add to the thermally induced anomalies chemically modified structures are found west of the east pacific rise epr and are of relevant amplitude both below the north western side of the pacific plate at the base of the lithosphere and up to 100 km depth beneath the hawaiian and super swell regions thus explaining the anomalous shallow regions without invoking the thermal buoyancy as the sole justification coherently with the chemically modified structures our results a support a lighter and more buoyant lithosphere than that predicted by the cooling models and b are in favor of the hypothesized crustal underplating beneath the hawaiian chain and beneath the volcanic units in the southern branch of the super swell region the comparison between calculated mantle gravity residuals and residual topography a suggests a lateral viscosity growth associated with the increasing thickness and density of the plate and b correlates well with sub lithospheric mantle flow from the epr towards west up to the kermadec and tonga trench in the south and the kuril kamchatka trench in the north

architecture and neogene to recent evolution of the western calabrian continental margin an upper plate perspective to the ionian subduction system central mediterranean the western calabria continental margin forms the transition between the pliocene to recent marsili spreading center and continental calabria all parts of the upper plate of the ionian subduction zone integrating high resolution and crustal seismic images constrained by gravity modeling we provide a detailed reconstruction of the architecture of the margin and develop a new scheme for its miocene to present evolution this time span encompasses the continent continent collision between africa and eurasia subsequent orogenic collapse and rifting apart between the two continental masses and the pliocene to recent emplacement of oceanic crust in the vavilov and marsili basins the crust of the margin thins from the calabria coast 25 km to the marsili continent ocean transition 12 km on the whole upper and lower crusts thin proportionally with pure shear geometry the continental margin is covered by an oligocene to present sedimentary succession reaching a maximum thickness of 6 0 km in the paola basin during the miocene the continental margin experienced regional shortening accommodated by a large number of mainly west vergent thrusts possibly associated with the late stages of the kabilo calabrian chain shortening continued through pliocene to recent but was accommodated by a limited number of west vergent thrust faults located in the western part of the margin and by a few tens of kilometers wide syncline located in the eastern part of the profile the accommodation space created in the syncline core hosted a 4 5 km thick plio quaternary sedimentary succession the paola basin no significant extensional fault is observed along the profile miocene to recent subsidence was controlled by 1 a short wavelength component related to shortening and responsible for the formation of the paola basin syncline and possibly contributing to the uplift of onshore calabria and 2 a long wavelength component responsible for the regional subsidence and oceanward tilting of the calabria margin short wavelength subsidence ended in the late pliocene but long wavelength downward movements persisted and even accelerated during late pliocene to quaternary times when the present day bathymetry was achieved both horizontal deformations and vertical movements are difficult to explain in the context of a normal back arc basin without taking into consideration patterns of secondary mantle flow generated by the retreat of the subducting slab