transition from a singly vergent to doubly vergent wedge in a young orogen the greater caucasus the greater caucasus mountains due to their youth 5 ma provide an opportunity for insight into the early stages of orogen development during continent continent collision however their recent tectonic evolution and first order architecture remain unclear here we investigate the evolution of the orogen by integrating new observations of the fluvial geomorphology and neotectonics of the range with prior work on seismicity geodetic strain bedrock geology and foreland basin structure we find that the range contains four zones along strike that differ in structural architecture topography and first order tectonic history in particular two south directed singly vergent zones at the western and eastern tips of the orogen are separated by both a central doubly vergent zone that is dominated by north directed deformation and an eastern doubly vergent zone in which south directed thrusting dominates we hypothesize that the along strike changes in vergence and locus of deformation reflects different stages in the development of a doubly vergent orogen with the tips of the range preserving an early singly vergent form and the center recording a more advanced orogen the differences between the two doubly vergent zones seem to be driven by the initial stages of collision between the structurally thickened crust of the greater and lesser caucasus orogens which initiated at 5 ma

topography of the variscan orogen in europe failed not collapsed the variscan orogenic collage consists of three subduction collision systems rheno hercynian saxo thuringian and massif central moldanubian devonian to early carboniferous marine strata are widespread not only in the individual foreland fold and thrust belts but also in post tectonic basins within these foreland belts and on the cadomian crust of peri gondwanan microcontinental fragments which represent the upper plates of the subduction collision zones these marine basins preclude high elevations in the respective areas and also in their neighbourhood widespread late carboniferous intra montane basins with their coal bearing sequences are likewise incompatible with high and dry plateaus while narrow belts with high elevations remain possible along active margins within the orogen comparison of the variscides with the himalaya tibetan plateau is unfounded plausible reasons for the scarcity of high variscan relief include subduction of oceanic and even continental crust subduction erosion orogen parallel extension and most important lithospheric thinning accompanied by high heat flow and magmatism in many areas timing and areal array of magmatism and ht metamorphism are not compatible with a model of tectonic thickening and subsequent gravitational collapse it is suggested instead that lithospheric thinning and heating are due to mantle activities caused by the tethys rift the lower and middle crust were thermally softened and rendered unfit for stacking and isostatic uplift in terms of topography the variscides represent a failed orogen the ht regime also explains the abundance of granitoids and ht lp metamorphic rocks typical of the variscides melting in the ht regime extracted mafic components from variscan and cadomian crust as well as from cadomian metasomatized lithospheric mantle thus mimicking subduction related magmatism the onset of the ht regime at c 340 ma may also have triggered the final ascent of hp uhp felsic metamorphic rocks

tectonosedimentary evolution related to extreme crustal thinning ahead of a propagating ocean example of the western pyrenees 1 in this paper we describe the tectonosedimentary evolution and its subsequent inversion of a basin that underwent extreme crustal thinning in a transtensional setting ahead of a propagating ocean in the western pyrenees the labourd mauleon area situated in the western pyrenees at the termination of the v shaped bay of biscay is an ideal natural laboratory to study how such complex basins evolve in time and space because of a mild inversion of the basin during pyrenean compression the rift structures and their relations to basement rocks and sediments are exposed and can be directly studied in the field the basin shows a complex polyphase evolution that starts with left lateral dominated transtension in latest jurassic early aptian time this event is overprinted by a late aptian early albian extension that is related to the counterclockwise rotation of iberia away from europe leading to the opening of the bay of biscay during this stage the late triassic to jurassic carbonate platform was stretched salt migrated and detachment faults exhumed upper and lower crustal and mantle rocks to the seafloor the final structure of the basin resembles a sag basin floored by exhumed rocks overlain by extensional allochthons and compartmentalized by n40 to n60 transfer faults the sedimentary architecture is characterized by late aptian synrift sediments e g urgonian limestones that were deposited in fault bounded basins and are overlain by thick latest aptian to albo cenomanian sediments e g flysch noir that define a sag sequence the complex tectonosedimentary evolution of the basin is associated with salt tectonics and overprinted by a major magmatic thermal event that postdates mantle exhumation

relations between climatic changes and prehistoric human migrations during holocene between gissar range pamir hindu kush and kashmir the archaeological and ecological data in the beginning of the holocene hunter gatherer populations settled in the pamir plateau especially in the tectonic depression of markansu near the kara kul lake osh kona site 4100 m 9580 bp and 7145 bp these populations were well adapted to high altitude life conditions in summer they were using stone tools related to a cobble tool tradition that ranov considered as the local continuation of an asian middle palaeolithic ferghana darwaz or punjab however they disappeared during the second half of the holocene as well hunters gatherers characterised by a tradition close to markansu culture namely hissar culture appeared during the holocene in the northern mountains of the tajik afghan depression amu darya upper basin occupying the middle altitude valleys gissar range when neolithic populations began to develop at lower altitudes for ranov origin and destiny of both markansu and hissar cultures were the most important questions to solve in this region the department of prehistory national museum of natural history paris conducted field work in collaboration with the university of peshawar between 1996 and 1998 in the northernmost valley of the indus basin giving access to the wakhan corridor the upper yarkhun valley chitral district pakistan accessible only by foot was surveyed from 2500 to 4000 m altitude this allowed the discovery of 6 sites yielding lithic artefacts among which half are cobble tools they attest to human activity later than 5500 bp suggesting population movements between the amu darya and indus basins the consequences of the quaternary climate oscillations between south asian monsoon and northern hemisphere influences on the one hand and the impact on biotopes of the increasing pastoral activity on the other hand are discussed as probable causes for the disappearance of the mountainous nomadic hunters of central asia

a wide angle seismic reconnaissance survey of the crust and upper mantle in the celtiberian chain of eastern spain abstract data from seismic refraction profiles to investigate the crust and upper mantle in the celtiberian chain are presented and discussed a rather heterogeneous deep crustal structure with lateral variations can be inferred from the available data in the central part of the chain crustal depths of about 32 km are coincident with those in the iberian meseta whereas close to the mediterranean shore the moho is located at about 20 km depth the varying thickness of the crust can be interpreted in terms of different tectonic regimes the shallowing towards the mediterranean is associated with the neogene rifting process which has its main expression in the gulf of valencia but whose effects seem to reach well towards the interior of iberia the upper mantle has a structure typical for the hercynian domain in europe a seismic phase reflected from about 80 km is the most important feature this may be interpreted as a mantle discontinuity with a positive velocity jump or alternatively as an indication for the bottom of the lithosphere

three dimensional gravity and magnetic modeling of crustal indentation and wedging in the western pyrenees cantabrian mountains 1 the complex crustal structure of the boundary zone between the iberian and european plates from the western pyrenees to the cantabrian mountains is probed by three dimensional 3 d gravity and magnetic modeling constrained by deep seismic profiles the 3 d modeling results support the presence of a continuous iberian crustal root and suggest that the geometry of the orogenic belt that formed in latest cretaceous tertiary times along the northern margin of iberia was conditioned by oblique structures separating areas characterized by different tectonic styles in the western pyrenees and the basque cantabrian basin a thick mesozoic basin presently incorporated to the pyrenean cantabrian belt the relatively narrow thinning of the crust inherited from the mesozoic rifting stage conditioned a structural style in which portions of the southward indenting european lower crust are interpreted to be back thrusted toward the north and uplifted to shallow depths promoting the appearance of significant potential field anomalies in the basque cantabrian basin the strongest aeromagnetic anomaly of the whole iberian mainland is superimposed on the eastern part of a well defined positive gravity anomaly similar in amplitude and wavelength to those located along the north pyrenean zone these observations suggest that the eastern part of the dense lower crustal causative body is strongly magnetized and may correspond to a gabbroic cumulate originated in the axis of the ancient mesozoic rift to the west tertiary compression affected the north iberian cantabrian passive continental margin whose geometry and inherited structures conditioned the formation of a double crustal delamination and the uplift of the cantabrian mountains

pleistocene volcanism and the geomorphological record of the hrazdan valley central armenia linking landscape dynamics and the palaeolithic record abstract the southern caucasus lies at the intersection of africa the levant and eurasia and is thus a region of considerable interest in the study of pleistocene hominin population dynamics and behaviour while palaeolithic archaeological sites in the region such as dmanisi and nor geghi 1 attest to such palaeogeographic significance a greater understanding of the chronology and nature of climatic and geomorphic changes in the region is needed to fully understand hominin settlement dynamics the hrazdan river valley central armenia has the potential to offer such insights given its rich palaeolithic record and complex history of pleistocene infill as a result of alluvial lacustrine aeolian and volcanic processes we therefore present a stratigraphic framework for basin infill and hominin activity during the pleistocene based on extensive geomorphological and geological mapping published chronometric results 40ar 39ar and k ar and archaeological survey we demonstrate that the onset of pleistocene volcanism in the gegham range to the immediate east of the hrazdan valley occurred around 700 ka bp after which there were several phases of effusive eruption lasting until 200 ka interbedded with lava emplaced by these eruptions are alluvial and lacustrine sequences some with evidence of pedogenesis and several of which have yielded palaeolithic artefacts taken together these sequences suggest a cyclical model of infill whereby lava flow along the valley resulted in the blockage of the palaeo hrazdan river and lake formation in the lea of the lava dams breaching of these dams resulted in a shift to predominately fluvial deposition and the consequent development of floodplain soils hominin populations exploited the floodplains at times when the last of these phases coincided with interglacial and interstadial climates but they also occupied the surrounding valley sides during the same warm humid phases

pleistocene glaciations of central asia results from 10be surface exposure ages of erratic boulders from the pamir tajikistan and the alay turkestan range kyrgyzstan abstract we have determined the timing of glaciations in the pamir tajikistan and the alay turkestan range kyrgyzstan using 10be surface exposure dating glacial advances in the area have occurred 93 136 60 80 40 55 27 25 22 20 19 17 16 15 15 13 and 11 9 cal ka bp all late pleistocene glaciers in the pamir and the alay turkestan ranges have been valley glaciers except for the most extended glaciers on the pamir plateau which have formed local piedmont glaciations in the eastern pamir these are characterized by ela depressions of 370 380 m thar 0 5 in the turkestan range and alay range ela depressions at the same time were 750 and 600 m respectively late pleistocene glacier advances all over western high asia were contemporaneous with climatic cold phases rather than monsoonal maxima their maximum extent and that of the western hemisphere ice sheets were asynchronous due to increasing aridity in the region over the course of the last glacial late pleistocene climate in central asia seems to have been influenced by the interplay of the westerly circulation and the siberian anticyclone some indirect monsoonal influence in the eastern pamir may be responsible for the existence of some of the lateglacial moraine stages in this area high altitude glaciers seem to have reached their maximum extent earlier mis 5 4 than low altitude glaciers first half of mis 3 possibly due to prolonged glacial aridity imparting with moisture advection onto high altitude sites inducing glacial retreat but prolonged cold during the same time imparting with glacier ablation at lower altitude sites inducing glacial advance

evidence for slab rollback in westernmost mediterranean from improved upper mantle imaging this work is funded by the picasso project nsf grant ear 0808939 the deployment and data processing for spanish stations was funded by consolider ingenio 2010 project topo iberia csd2006 00041 as well as alert es cgl2010 19803 c03 02

a framework for late quaternary lake level fluctuations in lake karakul eastern pamir focusing on lake glacier landform interaction abstract this paper presents a framework for late quaternary lake level fluctuation in the closed basin lake lake karakul eastern pamir on the basis of the stereoscopic observation of remote sensing data field mapping and relative dating the palaeoshorelines approximately 60 in number observed around the lake karakul can be classified into four groups h shorelines m shorelines l shorelines and ll shorelines in the descending order of height the highest level of each of the above palaeoshoreline groups is 205 m 85 m 35 m and 10 m above the present lake level 3915 m asl from the glacial landform developments and related valley fill sedimentation patterns around the threshold of the present basin closure the lake level fluctuation defined by these palaeoshoreline groups was found to be a consequence of the water balance change within the closed basin with respect to the timing of the palaeolake highstands the relationship between lacustrine terraces and terminal moraines suggests the synchroneity of the highest stand of each palaeolake with the corresponding maximum glacier advance the tentative chronology of the lake level fluctuation was established from the synthesis of the style of geomorphic development and related glaciation relative dating on moraine gravels and the correlations to established glacial histories in and around the pamir the periods of the palaeolake highstands indicated by h m l and ll shorelines seem to be correlated with the antepenultimate glacial mis 8 penultimate glacial mis 6 early last glacial mis 4 and the late last glacial mis 2 periods respectively based on this chronology each of the 60 palaeoshorelines are expected to show stable lake surfaces during lake regressive stages toward the terminations from the glacial maxima of mis 8 6 4 and 2 given that the distinct landforms of each palaeoshoreline group were formed in association with the predominant stagnation or small re transgression of the palaeolake the short term cooling and or wetter episodes which turned positive lake hydrologic balances from negative ones were superimposed on the major palaeoclimate changes during the glacial termination periods

crust and mantle lithospheric structure of the iberian peninsula deduced from potential field modeling and thermal analysis abstract we investigate the lithospheric structure of the iberian peninsula and lateral crustal density variations using a three step approach first the crustal and mantle lithosphere thicknesses are calculated from joint geoid and elevation modeling combined with thermal analysis further constrained by seismic data we then compute the 3d gravity effect of the resulting lithospheric structure to separate the measured bouguer anomaly into its regional and local components finally we invert the residual gravity anomalies to highlight lateral average crustal density variations and discuss them in terms of crustal structures our results show that for the majority of the study area the crustal thickness does correlate with the regional topography pattern the highest topography above 1500 m shows thicknesses above 44 km with local values up to 48 km crustal thicknesses in the range of 36 40 km are obtained in the uplifted alpine areas while a thinner crust is observed in sedimentary basins and in the iberian massif 30 to 35 km with the exception of sw iberia region where the crust thins from 30 to 28 km thick lithosphere above 140 km is found along the pyrenees the cantabrian mountains the iberian chain and in the betics while the thinnest lithosphere is found in sw iberia 90 km 3d inversion of residual anomalies show that for the majority of the area the average density of the crust is in the range of 2810 10 kg m 3 the denser crust is found in the nw and sw regions of the iberian massif 30 kg m 3 on average and locally in the pyrenees above 70 kg m 3 nw of the iberian chain 15 kg m 3 on average and in the southern internal betics 70 kg m 3 the least dense crust is found in the central and western betic chain 30 kg m 3 on average and in sedimentary basin depocenters

structural assemblage of high pressure mantle and crustal rocks in a subduction channel cabo ortegal nw spain 1 high pressure metamorphic fold nappes and ductile thrusts occur in the cabo ortegal upper allochthons they involve arc root lithospheric mantle peridotites high pressure volcanic arc granulites normal mid oceanic ridge basalt eclogites and shallow crustal volcanosedimentary high pressure gneiss units confluence of units from such disparate tectonic settings occurred at an eo hercynian convergent plate margin their internal deformation juxtaposition and high pressure synmetamorphic reworking resulted from kinematically simple but intense and polyphase ductile deformations fold nappes exhibit a remarkable sheath like form and contain mineral and stretching lineations defined by high pressure mineral assemblages subparallel to fold axes we argue that these structures outline the internal organization of high pressure sheets at deep tectonic realms of an oblique subduction collision orogenic channel

ongoing lithospheric removal in the western mediterranean evidence from ps receiver functions and thermobarometry of neogene basalts picasso project the western mediterranean tectonic system consists of the betic mountains in southern spain and the rif mountains in northern morocco curved around the back arc extensional alboran basin multiple tectonic models have been developed to explain the coeval compressional and extensional tectonic processes that have affected the western mediterranean since the oligocene in order to provide constraints on these evolutionary models we use ps teleseismic receiver functions rf thermobarometric analyses of post oligocene basalts and previous teleseismic tomography images to investigate the lithospheric structure of the region ps rfs were calculated using seismic data from 239 broadband seismic stations in southern iberia and northern morocco and thermobarometric analysis was performed on 19 volcanic samples distributed throughout the region the rf images reveal a highly variable moho depth 25 to 55 km as well as a strong positive sub moho horizon between 45 and 80 km depth beneath the central betic and rif mountains which we interpret to be the top of the previously imaged alboran sea slab thermobarometric constraints from magmas in the eastern betics and rif indicate mantle melting depths between 40 and 60 km typical of melting depths beneath mid oceanic ridges where little to no lithosphere exists together the rf and thermobarometric data suggest ongoing and recent slab detachment resulting from delamination of the continental lithosphere

a seismic geotraverse across the iberian variscides orogenic shortening collisional magmatism and orocline development 1 a crustal geotraverse through the iberian variscides is presented by integrating the available geological and seismic profiling data different modes of orogenic shortening are identified with varying degrees of coupling between upper and lower crust in northern and southern regions of the geotraverse a decoupling in the middle crust permits the lower crust to subduct underthrust thus compensating for strong upper crustal shortening this behavior does not result in great crustal thickening except in sectors of crustal underthrusting in southern central iberia moderate upper crustal shortening is due to a mechanically strong lower crust impeded to subduct underthrust in this region shortening is partitioned between upper and lower crust deformation being distributed in the upper crust while localized at major fault zones in the lower crust finally the central region of the geotraverse northern central iberia shows a coupled crustal deformation having given way to the largest orogenic thickening in the iberian variscides the thermal maturity of this much thickened crust originated voluminous crustal melting and concomitant normal fault detachments developed while shortening dominated in other regions theoretical models suggest that compressive stresses may prevail in the lower crust beneath the extending upper crust thus explaining the efficient syncollisional exhumation in this part of the orogen a particular feature of the iberian variscan geotraverse is the great importance of out of section mass movements mainly left lateral shear zones concentrated in two suture boundaries which displaced to the nw present coordinates central and northern iberia with respect to southern iberia

gravity constraints on the deep structure of the pyrenean belt along the ecors profile abstract in order to furnish further constraints to modelling the ecors pyrenees deep seismic profile gravity data were collected along a stripe 20 km wide and 220 km long containing the seismic line a total of 4020 stations have been used to derive a bouguer anomaly map of the area a large and roughly symmetrical negative anomaly 100 mgal is centered on the axial zone a local positive anomaly over the north pyrenean zone disturbs the negative regional trend somewhat detailed densities were assigned to the sedimentary cover on the basis of borehole samples refraction data and a velocity density relationship were used to constrain the densities adopted for the deeper layers the results of the two dimensional gravity modelling confirm the asymmetrical shape of the crust mantle boundary beneath the pyrenean belt the downward deflection of the iberian moho from the ebro basin leads to a maximum depth of 65 km under the paleozoic axial zone whereas a depth of 35 km is found for the european moho under the north pyrenean zone two extreme models are proposed for the northern limit of the iberian crust a vertical contact in the downward continuity of the north pyrenean fault or a 70 northward sloping interface the positive anomalies beneath the north pyrenean zone may be explained by dense intracrustal mantle slices or lower crustal sheets the outcrop of granulitic basic gneiss within the labourd massif suggests that the anomaly results from lower crustal sheets

cenozoic vertical motions of the catalan coastal ranges ne spain the role of tectonics isostasy and surface transport 1 we analyze the cenozoic topographic evolution of the catalan coastal ranges ne spain and the role of fault activity erosion sedimentation and isostasy in controlling uplift and subsidence a forward numerical model constrained by an extensive geological and geophysical data set is used to examine the temporal and spatial record of cenozoic vertical motions we show that the effect of isostasy erosion and sedimentation is as important as the contribution of fault deformation to the topography of the catalan coastal ranges the model predicts that paleogene topography generation by thrusting was compensated by erosion up to 1 3 km and isostatic subsidence up to 1 2 km resulting in a 1 2 1 9 km high mountain range by the end of compression 29 ma during the neogene strong tectonic subsidence related to normal faulting and the consequent flexural uplift of 0 7 1 2 km surface erosion as much as 1 6 2 3 km and sedimentation up to 4 5 km led to the present landscape configuration extension rates along the barcelona fault controlled flexural uplift and in combination with erosion and sedimentation processes led to the migration of the topographic maximum of the prelitoral range toward the easternmost ebro basin

a deep seismic crustal transect from the ne iberian peninsula to the western mediterranean the crustal structure of the transition from the ne iberian peninsula to the western mediterranean is characterized by large scale variations related to its successive compressional and extensional cenozoic tectonics the spanish esci spanish acronym for seismic studies of the iberian crust program recorded 450 km of deep vertical reflection profiles on land and at sea to complete a first crustal transect from the pyrenees to the south balearic basin highly energetic north dipping reflections imaged by combining the etude continentale et oceanique par reflexion et refraction sismique ecors and esci land profiles mark a crustal thickening toward the pyrenees the reflective band becomes horizontal beneath the catalan coastal ranges and the moho is found at 11s no evidence of crustal thinning affecting the iberian mainland is observed the transition to the mediterranean basin is constrained by complementary onshore offshore recordings forward modeling combined with multichannel processing of the wide angle data set shows that a strong thinning of the continental crust by a factor of 2 over a distance of 50 km affects both the catalan and balearic flanks of the valencia trough this thinning affects mainly the deep crust characterized by low velocities of 6 4 6 5 km s suggesting a removal of part of the lower crust during the rifting processes velocities of 7 8 7 9 km s are interpreted in the uppermost mantle with no evidence of underplating the moho appears as a marked discontinuity throughout the transect the nw part of the balearic promontory is characterized by a thick and reflective crust from 12 to 30 km depth an intensely fracturated evaporitic sequence is seen for 100 km along the south balearic basin the seismic images of the continent ocean transition are disturbed by these prominent sediments however the deep reflectivity suggests a crustal thinning moho at 6 7 s to be related to the middle miocene present extensional tectonics

are the oroclines of the variscan belt related to late variscan strike slip tectonics terra nova 23 241 247 2011 abstract early variscan structures and magnetic anomalies delineate four oroclines along the variscan belt the arcs bend the lithostratigraphic zones of the autochthon and the allochthonous terranes which include ophiolites of the rheic suture and units of gondwanan derivation subducted on both sides of the rheic ocean a transcurrent model dominated by right lateral motion explains the genesis and evolution of the oroclines and a simple plate tectonics scenario links late variscan dextral strike slip movements in the variscides to a broad intracontinental shear zone kinematically equivalent to a transform fault terra nova 00 1 7 2011

crustal and velocity structure of the valencia trough western mediterranean part i a combined refraction wide angle reflection and near vertical reflection study abstract in november 1988 a 2 ship seismic survey was carried out in the valencia trough western mediterranean to collect normal incidence seismic reflection profile data and six expanding spread profiles along the continental shelf and trough velocity depth solutions derived from the analysis of the esp show a pattern that corresponds with that of continental type crust except in the northeastern part of the basin where oceanic type crust is present along the iberian margin and centre of the trough the seismic data show a well developed neogene and quaternary sequence with velocities ranging from 1 6 to 4 8 km s 1 whereas along the mallorca margin these deposits are absent at the base of the neogene there is a tertiary unconformity which marks the top of the pre rift mesozoic carbonate platform the carbonates which have velocities from 5 4 to 5 9 km s 1 thin towards the axis of the trough along both margins the upper and middle crust is characterised by an almost transparent layer of variable thickness 6 9 km with velocities ranging from 6 1 to 6 4 km s 1 dipping reflections are observed however in the southern part of the trough these reflections are the result of a locally thick mesozoic sequence a 6 km thick highly reflective lower crust with velocities from 6 4 to 7 0 km s 1 is seen beneath the iberian margin along the mallorca margin the lower crust is variably reflective with a velocity of about 6 6 km s 1 in the centre of the trough the total crustal thickness is less than 14 km which thickens asymmetrically towards the flanks reaching values of 20 21 km off shore the iberian peninsula and 23 km in the mallorca margin the seismic moho increases in depth from 13 to 16 km in a ne sw direction relatively low upper mantle velocities from 7 6 to 8 0 km s 1 have been found throughout the basin indicating a slightly anomalous uppermost mantle or a crust mantle transitional layer in the northeast the velocities for the sediments are similar to those described above however the crustal velocity solution can be characterised by three velocity gradient layers ranging from 4 8 6 1 6 1 6 7 to 6 7 7 2 km s 1

high resolution moho topography map beneath iberia and northern morocco from receiver function analysis abstract crustal thickness maps at regional scales are typically compiled using estimations inferred from different geophysical datasets providing a variable coverage of the investigated area consequently spurious effects related to changes in data resolution or artifacts in grid interpolation may affect significant zones of those maps the topoiberia iberarray broad band seismic network covering the iberian peninsula and northern morocco with stations distributed on a regular 60 60 km grid provides a unique opportunity to avoid such technical problems and to obtain a crustal thickness map derived from a same method sampling evenly all the region data from more than 340 stations has been gathered and analyzed using the p to s conversion phases at the moho discontinuity receiver functions the crustal thickness has been inferred applying the classical h stacking technique though in regions of complex crustal structure we have preferred to estimate the thickness directly from the arrival time of the converted phase at some sites the topography of the moho discontinuity is strongly correlated with tectonic processes the investigated area extending from the sahara platform to the bay of biscay has a great geodynamic diversity including north to south crustal imbrication in the pyrenean and cantabrian range a large and relatively undisturbed variscan massif in the center of iberia and areas of complex and still not completely understood geodynamics in the alboran crust domain and the atlas range the crustal thickness map reflects this diversity showing variations reaching 30 km between the thickest and thinnest zones of continental crust the final map has an overall similarity with previous estimations of the crustal thickness using independent data as those coming from more sparse deep seismic sounding profiles but provides further constraints at regional scale

modeling the evolution of the guadalquivir foreland basin southern spain 1 previous quantitative studies dealing with the origin of foreland basins have focused primarily either on the rheological basis of the lithosphere mechanical response or on the relationship between orogenic loading and sediment geometry to link the evolution of the guadalquivir foreland basin south iberia with the thermomechanical stratification of the iberian lithosphere we combine quantitative approaches to deep and shallow processes thrust loading lithospheric flexure thickness changes of the crust and the lithospheric mantle and surface mass transport a planform flexural analysis of the present day load distribution shows that basement subsidence is related not only to upper crustal thrusting but also to a deep seated additional load on the basis of the observed gravity and geoid fields we propose this additional load to be related to a lithospheric mantle thickening larger than the coeval crustal thickening further modeling of the evolution of a basin cross section reveals that the architecture of the sedimentary basin is additionally related to the lithosphere rheological response the quantitative study of the evolution of basement faulting and the forebulge uplift of sierra morena leads us to conclude that viscous stress relaxation and or plastic yielding within the lithosphere are key processes to explain the flexural evolution of the basin

mantle lithosphere bodies in the alboran crustal domain ronda peridotites betic rif orogenic belt abstract geological and geophysical data are used to demonstrate the existence of intracrustal high density high p wave velocity bodies in the western betics these bodies appear to correspond to buried peridotites similar to those that outcrop in the ronda area a gravity study shows how the gravity field is mainly the result of a combined effect of crustal thinning and the presence of ultramafic bodies the size of the buried high density body as interpreted from gravity and seismic results shows maximum dimensions of about 40 km in length nnw sse about 8 km in thickness and a lateral extension ene wsw of about 70 km the thinning of the crust from 32 35 km to 20 22 km takes place in a narrow area less than 35 km wide our results are compatible with an interpretation in terms of an unrooted peridotite slab dismembering of an initial slab of ultramafic rocks is a possible consequence of the extensional regime that originated the alboran basin

estimated source wavelet incorporated reverse time migration with a virtual source imaging condition manygeophysicistsperformreverse timemigrationusingavarietyofartificialsources to obtain the source wavefield upon processing the seismic data however it is difficult to recover the original phase and amplitude of the source wavelet used for seismic exploration regardless of the source we have therefore used several artificial source wavelets such as ricker or the first derivative gauss wavelets expressed by well known functions there are some differences between these artificial source wavelets and the original source wavelets resulting in imperfect migration images artificial source wavelets tend to distort the exact location of subsurface reflectors and they create noise around the boundary of the stratum to solve this problem we applied the source estimation technique to the reverse time migration algorithm the source estimation technique approximates the source wavelet to the original exploration source wavelet by a deconvolution method this technique is used in full waveform inversion and provides better inversion results as demonstrated by other studies toprovetheeffectofreverse timemigrationwithsourceestimation wetested this algorithm on the sigsbee2a model seg eage 3d salt model and 3d real field land data using the resulting images of these three models we found that the source estimation technique can yield better migration images to suppress the artefacts produced in the migration image we used a wavenumber filter and laplacian filter on 2d and 3d examples respectively furthermore we used the pseudo hessian similar to the source illumination to scale the migration image because the virtual source imaging condition was used for reverse time migration

three dimensional flexural modelling of the ebro basin ne iberia summary the ebro basin the southern foreland basin of the pyrenees has undergone a complex evolution in which apart from the pyrenees the iberian range and the catalan coastal ranges have played an important role both as sediment sources and as basin confining structures the deflected basement underlying the ebro basin dips north suggesting a lithospheric scale control on the structure of this basin this is compatible with the results of subsidence analyses which show that the study area is not in a local mode of isostatic compensation in order better to understand the mechanisms that led to the present configuration of the ebro basin and particularly the relevance of the various kinds of un loading e g surrounding fold and thrust belts basin topography subsurface loads we carried out a 3 d kinematic modelling study that accounts for the flexural state of the lithosphere subjected to various loads applied at its lateral boundaries and the sedimentary fill of the basin we also included the effect of neogene extensional tectonics along the eastern basin margin which is related to the opening of the valencia trough we show the suitability of the 3 d lithospheric scale flexural modelling approach to the study of ne iberia modelling results point to a relatively strong lithosphere in this area with values of effective elastic thickness ranging from 10 to 35 km in the ebro basin increasing towards the pyrenees we also find that the topographic tectonic load itself is insufficient to explain the observed basement deflection thus an extra subsurface load beneath the pyrenees corresponding to the underthrusted iberian lithosphere is required the effect of lithospheric stretching in the valencia trough on the ebro basin is appreciable only in its eastern part where the lithosphere was uplifted this had considerable repercussions on the sedimentary and erosional regime of the ebro basin we have analysed the link between the stretching related tectonically uplifted areas and the erosional patterns observed onshore northeast iberia

late quaternary record of the vegetation and catchment related changes from lake paravani javakheti south caucasus abstract here we present a palynological and sedimentological record from a 96 cm sediment core covering the last 13 ka aiming to document palaeoecological changes in the central south caucasus driven by climate and or human impact the core was retrieved from lake paravani 2073 m asl 41 27 n 43 48 e located in the steppic grasslands of south caucasus in the samsari javakheti volcanic plateau the geomorphological features observed on the plateau including moraine deposits suggest the presence of local glaciers reaching the lake level during the last glacial periods based on sediment and pollen data three palaeoecological phases have been identified the first phase spanning the younger dryas and the early holocene corresponds to a steppic environment with a limited lake productivity driven by a cold and particularly dry climate according to the age depth model this phase ends near 8500 cal bp with the decline of chenopodiaceae the second phase starts with an important expansion of trees at 8300 cal years bp the delayed afforestation recorded in lake paravani is a pattern that has now been recognised widely through the black sea region s more continental areas as soon as the climatic and edaphic conditions were favourable the main deciduous and coniferous trees expanded concurrently due to the proximity of glacial forest refugia located in western caucasus this second phase marked by a climatic optimum is also characterized by an increase in lake productivity the third phase starts at 2000 3000 cal bp and corresponds to the decline of forests on the plateau and the expansion of herbaceous formations leading to the present day steppic environment this deforestation phase is driven by the deterioration of the climate conditions and human impact

lithospheric folding in iberia integration of stress indicator data gravity data crustal kinematics data and analysis of topography and recent vertical motions demonstrates the occurrence of consistently oriented spatial patterns of large scale alpine to recent intraplate deformation in iberia the inferred upper crustal and lithospheric deformation patterns and the timing of the associated expressions at or near the surface support the existence of a close coupling with plate boundary processes operating at the margins of iberia patterns of lithosphere and upper crustal folds are oriented perpendicular to the main axis of present day intraplate compression in iberia inferred from structural analysis of stress indicator data and focal mechanism solutions these findings suggest the presence of lithospheric folds with wavelengths compatible with theoretical predictions of folding wavelengths of variscan lithosphere stress induced intraplate deformation set up by plate interactions is compatible with indications for the absence of present day deep mantle lithosphere interactions inferred from seismic tomography

paleomagnetic structural and stratigraphic constraints on transverse fault kinematics during basin inversion the pamplona fault pyrenees north spain 1 the pamplona fault in the pyrenees is a major transverse structure that has been classically interpreted as a strike slip fault however lack of consensus concerning the sense of movement casts doubt on its actual kinematics and as a consequence its role in the cenozoic evolution of the pyrenees remains controversial in order to assess its kinematics we have conducted a paleomagnetic structural and stratigraphic study focused on the mesozoic and tertiary sedimentary rocks that outcrop around the southern segment of the fault restoration of balanced cross sections allows us to examine the present day spatial relationship of the sedimentary sequences on both sides of the fault and to reconstruct the geometry of the extensional basins formed during mesozoic rifting episodes in the bay of biscay and pyrenean domains paleomagnetic results indicate that no significant tectonic rotations occurred around the fault during tertiary inversion of the pyrenees the lack of tectonic rotations and revaluation of previous hypotheses argues against a strike slip movement of the fault we propose a new model in which the pamplona fault is treated as a large scale hanging wall drop fault whose kinematics was determined by variations in the geometry and thickness of mesozoic sequences on both sides of the fault these variations influenced the geometry of the thrust sheet developed during tertiary compression we are unaware of any other transverse fault that has been interpreted in this fashion thus the pamplona fault serves as a case study for the evolution of transverse faults involved in basin inversion processes

crustal structure beneath the iberian peninsula and surrounding waters a new compilation of deep seismic sounding results abstract we present here an updated compilation of crustal parameters beneath the iberian peninsula and surrounding waters inferred from extensive deep seismic exploration performed in the last three decades firstly the more relevant experiments developed in both terrestrial and marine domains are revisited together with the corresponding seismic velocity depth models published that reveal the characteristics of the different tectonic domains sampled including oceanic zones continental margins orogenic and rift belts the results are summarized in three crustal transects sketched along representative directions secondly we compiled the moho depths along all the available seismic profiles to produce a geo referred database this database has then been interpolated using kriging algorithms to obtain a continuous moho depth model in the form of a regular grid file this integrative moho map for a key area in the western mediterranean documenting the interaction between european and african plates can contribute to constrain further regional studies either at crustal lithospheric or mantle scales

glacial isostatic adjustment in the static gravity field of fennoscandia in the central part of fennoscandia the crust is currently rising because of the delayed response of the viscous mantle to melting of the late pleistocene ice sheet this process called glacial isostatic adjustment gia causes a negative anomaly in the present day static gravity field as isostatic equilibrium has not been reached yet several studies have tried to use this anomaly as a constraint on models of gia but the uncertainty in crustal and upper mantle structures has not been fully taken into account therefore our aim is to revisit this using improved crustal models and compensation techniques we find that in contrast with other studies the effect of crustal anomalies on the gravity field cannot be effectively removed because of uncertainties in the crustal and upper mantle density models our second aim is to estimate the effects on geophysical models which assume isostatic equilibrium after correcting the observed gravity field with numerical models for gia we show that correcting for gia in geophysical modelling can give changes of several kilometer in the thickness of structural layers of modeled lithosphere which is a small but significant correction correcting the gravity field for gia prior to assuming isostatic equilibrium and inferring density anomalies might be relevant in other areas with ongoing postglacial rebound such as north america and the polar regions

evidence for long lasting landform surface instability on hummocky moraines in the pamir mountains tajikistan from 10be surface exposure dating abstract surface exposure dating is a new but already widely used tool in geomorphological studies aiming e g at the establishment of glacial chronologies sometimes however results from samples taken from one and the same moraine scatter widely and thus interpretation turns out to be difficult here we assess sample specific effects topographic shielding sample geometry and erosion on 17 surface exposure ages obtained by analysis of in situ produced cosmogenic 10be in boulders from moraines in the pamir mountains tajikistan a wide scatter of exposure ages is observed only for hummocky moraines 45 to 10 ka bp but not for distinct lateral moraines 20 and 60 ka bp respectively it is hypothesized that inheritance prior exposure and moraine degradation may be responsible for the wide scatter of exposure ages on the hummocky moraines to proof this hypothesis a data set of 72 boulders from the pamir mountains is used we conclude that most likely hummocky moraines experienced long lasting landform surface instability probably due to buried glacier ice that is protected from melting several ten thousand years by a thick debris cover

data model comparison of the younger dryas event the younger dryas cooling event is well established in the north atlantic region through numerous climate proxy records although the climatological controls vary from site to site it is considered to have taken place between about 10 000 and 11 000 bp radiocarbon years 11 500 13 000 calendar years ago outside the north atlantic region climate proxy records and chronology commonly become problematic because of weaker signals and less dating control in addition to this evidence oceanic records reveal conflicting evidence for younger dryas forcing mechanisms and the timing of events we compare proxy evidence with the results from an ocean general circulation model coupled to the energy moisture balance atmospheric model the model results reveal a global pattern and regional magnitude which generally agree with temperature changes interpreted from paleoclimate reconstructions the model also supports the general duration of global cooling of the younger dryas although proxy data can be controversial outside of the north atlantic region the authors believe that there is enough evidence to support the younger dryas event on a global scale they also recognize however that more concrete evidence is needed before the question can be unequivocally answered

seismic evidence of alpine crustal thickening and wedging from the western pyrenees to the cantabrian mountains north iberia 1 the alpine collision between the iberian and european plates resulted in a complex crustal structure beneath the northern iberian peninsula as revealed from a new set of seismic refraction wide angle reflection profiles the study area is characterized by two major e w ranges the cantabrian mountains and the pyrenees which are relayed to the south by the iberian chain important variations in crustal thickness and velocity distribution are found in a 560 km long e w transect in contrast to the typical 30 to 32 km thick european variscan crust of the western end of the profile a continuous alpine crustal root is evidenced from the cantabrian mountains to the central pyrenees with a moho depth of 46 48 km locally rising to 40 km depth in between beneath the basque cantabrian basin another outstanding feature is the inferred presence of high velocities of 6 40 6 75 km s at midcrustal depths which can be associated with portions of a lower crustal wedge from the northern european domain indenting the southern iberian crust during the alpine stage of compression this indentation produces the delamination of the iberian crust with northward underthrusting of its lower half and the consequent crustal thickening the indenting wedge has a discontinuous presence along the longitudinal section as it was controlled and or affected by n s to ne sw structures further evidence of the northward subduction of the iberian plate is provided by another profile toward the aquitaine basin while a n s profile across the iberian chain reveals an alpine midcrustal thickening beneath this belt with moho depths of 42 km

on the post 25 ma geodynamic evolution of the western mediterranean during the neogene and quaternary western mediterranean geodynamics were dominated by the eastward migration of the apenninic arc and associated back arc basins the migration was controlled by retreat of the apenninic slab and was associated with boudinage of the lithosphere in the back arc area palaeo reconstruction of the kinematics of the arc suggests about 775 km of migration from the late oligocene to present along a transect from the gulf of lions to calabria a maximum of 135 km of n s converge occurred between africa and europe during the same time span the western mediterranean was thus mainly shaped by the migration of the slab related to west directed subduction it is hypothesized that minor n s convergence deformed the arc but was not the cause of its formation 1998 elsevier science b v all rights reserved

late quaternary glaciation in the kyrgyz tien shan the tien shan of kyrgyzstan contains multiple moraines and drift from late quaternary glaciations the spatial temporal distribution of the glaciers inferred from the moraines suggests that the main factor controlling glacier advance here was the availability of moisture the dominant modern climatic signatures in northern central asia include orographic thunderstorms in summer cold and dry siberian high pressure cells in winter and westerly cyclonic storms from the north atlantic and eastern mediterranean in spring and fall changes in any of these systems during the late quaternary would have varied precipitation delivery to and glacier growth in the kyrgyz tien shan geomorphic mapping and reconnaissance level 10be cosmic ray exposure dating of moraine sequences in six drainages indicate that there were multiple maximum advances of similar extents and equilibrium line depressions across the range glaciers in the north and east of the kyrgyz tien shan last advanced to their maximum positions during marine oxygen isotope stage mis 5 and again during mis 4 while in the south and west of the range advance occurred during mis 3 in contrast to maritime europe and north america there is no evidence of a major glacial advance during mis 2 glacier advances during mis 2 and since were restricted to the vicinity of modern glaciers allowing the older glacial record to be preserved well