progradation of the late quaternary gediz delta turkey abstract detailed 3 5 khz seismic reflection profiling and coring have shown that the continental shelf break and slope off izmir bay turkey are formed by prograding deltaic silty mud sequences the muds contain shallow brackish water benthic and cold water planktonic foraminifera they were deposited when sea level was about 110 m below its present position during the last pleistocene glaciation slumping took place on the prodelta slope leaving rotational slump scars and imbricate slump blocks downslope delta top truncation took place in shallow water by erosive coastline retreat after distributary abandonment there has been little or no sedimentation since that time outer izmir bay is thus floored by relict sands following rapid post glacial transgression the gediz delta was reestablished in izmir bay archaeological evidence shows it has prograded during the last 3000 yrs at least six shifts in the position of the gediz mouth are distinguished during this time and abandoned delta top channels can be correlated with submarine delta lobe sequences

calculated volumes of individual shield volcanoes at the young end of the hawaiian ridge abstract high resolution multibeam bathymetry and a digital elevation model of the hawaiian islands are used to calculate the volumes of individual shield volcanoes and island complexes niihau kauai oahu the maui nui complex and hawaii taking into account subsidence of the pacific plate under the load of the hawaiian ridge our calculated volume for the island of hawaii and its submarine extent 213 103 km3 is nearly twice the previous estimate 113 103 km3 due primarily to crustal subsidence that had not been accounted for in the earlier work the volcanoes that make up the island of hawaii mahukona kohala mauna kea hualalai mauna loa kilauea and loihi are generally considered to have been formed within the past million years and our revised volume for the island indicates that magma supply rates are greater than previously estimated 0 21 km3 yr as opposed to 0 1 km3 yr this result also shows that compared with rates calculated for the hawaiian islands 0 6 ma 0 095 km3 yr the hawaiian ridge 0 45 ma 0 017 km3 yr and the emperor seamounts 45 80 ma 0 010 km3 yr magma supply rates have increased dramatically to build the island of hawaii

late cenozoic basin development in west turkey gordes basin tectonics and sedimentation the early miocene sedimentary succession in the northeast southwest trending gordes basin is 1000 m thick and divided into the da dere tepekoy and kuslukkoy formations the age of this fill can be constrained as between 24 2 ma and 16 3 ma at its widest interval paleocurrent directions from south to north demonstrate that the basin had a north dipping basin floor these observations are inconsistent with a previous model of the gordes basin as a cross graben with a south dipping basin floor towards the alasehir graben and an anomalously thick up to 3000 m basin filling

analyses of fault mechanisms and expansion of southwestern anatolia since the late miocene abstract neotectonic field studies and detailed analyses of neogene and quaternary fault mechanisms in southwestern anatolia enable us to recognize a succession of compressional and extensional events and to characterize the direction of corresponding regional stresses the three most important compressive phases occurred during the miocene and a much smaller one near the plio quaternary boundary the last one or two interrupted a widespread extension of much greater duration and amplitude the whole tectonic evolution resembles that of the aegean the large extension by normal faulting is consistent with a minimum stress along a nne ssw average direction it appears that this direction was n s during the pliocene and changed to ne sw sometime during the quaternary this dominant nne ssw extension which began during late miocene or earliest pliocene was related to the development of the southwestern anatolian graben system

evidence for dynamic coupling of surface processes with isostatic compensation in the lower crust during active extension of western turkey western turkey in the eastern part of the aegean region is extending slowly with extension no faster than 0 5 mm yr 1 across any individual active normal fault up to 15 km of southward extension has occurred in the most active 100 km wide part of this region since 15 ma indicating a typical strain rate of 3 10 16 s 1 rivers carry a sediment flux of 4 106 m3 yr 1 westward to the aegean sea coast with offshore sedimentation at 1 mm yr 1 sediment loading causes coastal areas to subside much faster than would be expected from the extension alone most of this sediment is derived from regional erosion of inland areas to the east at a typical rate of 0 1 mm yr 1 this erosion being isostatically compensated by uplift it is suggested that the lower crustal material displaced by sediment loading near the coast flows east to isostatically compensate the erosion the average eastward velocity of this lower crustal channel flow beneath the aegean coast is estimated as 1 mm yr 1 the maximum velocity is 2 mm yr 1 this case study thus indicates the general point that isostatically compensated erosion and lower crustal channel flow can affect the evolution of sedimentary basins that are surrounded by eroding landmasses factors that are often neglected

active tectonics of the north and central aegean sea summary in this paper we examine the connection between the westward motion of turkey relative to europe and the extension in and around the aegean sea the principal new data available since the last attempt to synthesize the tectonics of this region by mckenzie 1978 are much improved focal mechanisms of earthquakes constrained by p and sh body wave modelling as well as by first motions these mechanisms show that the faulting in the western part of the aegean region is mostly extensional in nature on normal faults with a nw to wnw strike and with slip vectors directed nnw to nne there is evidence from palaeomagnetism that this western region rotates clockwise relative to stable europe in the central and eastern aegean and in nw turkey distributed right lateral strike slip is more prevalent on faults trending ne to ene and with slip vectors directed ne palaeomagnetic data in this eastern region is more ambiguous but consistent with very small or no rotations in the northern part and possibly anticlockwise rotations relative to europe in the south the strike slip faulting that enters the central aegean from the east appears to end abruptly in the sw against the nw trending normal faults of greece the kinematics of the deformation is controlled by three factors the westward motion of turkey relative to europe the continental collision between nw greece albania and the apulia adriatic platform in the west and the presence of the hellenic subduction zone to the south as the right lateral slip on the north anatolian fault enters the aegean region it splays out becoming distributed on several parallel faults the continental shortening in nw greece and albania does not allow the rotation of the western margin of the region to be rapid enough to accommodate this distributed e w right lateral shear and thus leads to e w shortening in the northern aegean which is compensated by n s extension as the southern aegean margin can move easily over the hellenic subduction zone the dynamics of the system once initiated is self sustaining being driven by the high topography in eastern turkey and by the roll back of the subducted slab beneath the southern aegean the geometry of the deformation resembles the behaviour of a system of broken slats attached to margins that rotate in spite of its extreme simplicity a simple model of such broken slats is able to reproduce quantitatively most of the features of the instantaneous velocity field in the aegean region including the slip vectors and nature of the faulting in the eastern and western parts the senses and approximate rates of rotation the overall extensional velocity across the aegean and the distribution of strain rates as seen in the seismicity and topography or bathymetry and using geodetic measurements as part of this study we re examined the relation between the surface faulting and the focal parameters determined seismologically for the three large 1981 gulf of corinth earthquakes and reassessed the evidence for associating particular earthquakes in the sequence with observed surface faulting an important result is that in one of the events there is a resolvable discrepancy between the slip vector measured at the surface and that determined from the seismic body waves

how long lived is ultrahigh temperature uht metamorphism constraints from zircon and monazite geochronology in the eastern ghats orogenic belt india abstract along the coast of peninsular india the eastern ghats expose a deep crustal section through a composite proterozoic orogenic belt to quantify the late mesoproterozoic early neoproterozoic pressure p temperature t time t evolution of the eastern ghats province new shrimp u pb zircon and monazite age data from multiple localities are reported and integrated with the results of phase equilibria modelling samples of residual granulite migmatite and enderbite yield a spread of weighted mean 207pb 206pb zircon and monazite ages between ca 970 and ca 930 ma based on ranges of spot ages from several samples the late prograde to peak ultrahigh temperature uht metamorphism counter clockwise evolution ccw to t 950 c at p 8 kbar and initial cooling is interpreted to have occurred between ca 1130 and ca 970 ma regionally extensive enderbite and charnockite magmas were emplaced into the hot suprasolidus crust around the time of peak metamorphism for the residual granulites and migmatites the retrograde p t t path is characterized by close to isobaric cooling to the variable but elevated solidi for different samples weighted mean ages between ca 970 and ca 930 ma in several samples are interpreted to record the timing of crystallization of melt trapped by the percolation threshold in each of these samples two additional weighted mean ages of ca 980 ma from korhonen f j saw a k clark c brown m bhattacharya s 2011 new constraints on uht metamorphism in the eastern ghats province through the application of phase equilibria modelling and in situ geochronology gondwana research 20 764 781 extend this range back in time by 10 my the variability in the calculated weighted mean ages across the region is interpreted to be due mainly to differences in the temperature of the elevated solidus from sample to sample suggesting a slow cooling rate of 1 c my during the retrograde stage of this long lived uht metamorphism these results demonstrate that the eastern ghats province sustained uht conditions t 900 c for 50 my and perhaps for as long as 200 ma from ca 1130 to 930 ma during a single ccw tectono metamorphic event

parameterized convection and the thermal evolution of the earth abstract thermal convection is an efficient means of extracting heat from the interior of the earth heat lost from the earth s interior comes from the decay of radioactive isotopes and the cooling of the earth to determine the magnitude of each contribution detailed studies of the convective mechanism must be carried out one approach to this problem is to parameterize a nondimensional mantle temperature in terms of the mantle rayleigh number the time variation of the radioactive heat production and the transient cooling of the entire earth are included also included is the differentiation of radioactive isotopes into the continents important conclusions are 1 1 that between 25 and 30 of the surface heat flow can be attributed to the cooling of the earth this gives a mean concentration of uranium in the mantle close to 30 ppb 2 2 that two scales of mantle convection are occurring the first associated with convection of the surface plates and the second a turbulent convection beneath the surface plates 3 3 that the mean temperature of the mantle in archean times was 100 150 k hotter than at present but that the mean thickness of the lithosphere was about one half the present value 4 4 that 60 to 80 of the area of the continents was formed prior to 3 b y b p

site response of deep alluvial deposits in the northern coast of izmir bay turkey and a microzonation study based on geotechnical aspects izmir the third largest city with fast economically growths in western turkey has experienced various moderate to large historical and recent earthquakes karsiyaka cigli districts and their surrounding areas located in northern coast of izmir bay and one of the major economically and residentially developing districts are subject to strong shakings due to deep sediments and shallow soft liquefiable soils in the area the purpose of this study is to develop a comprehensive microzonation model based on geotechnical aspects and put forth this model for use of residential developments in the area the properties and dynamic behavior of the quaternary alluvial soils in the study area were assessed using geotechnical and geophysical data gathered from 461 boreholes and 205 microtremor recordings one dimensional dynamic site response analyses were performed with equivalent linear earthquake site response analysis eera software by using the simulated earthquake time histories the maximum ground surface acceleration values obtained from the dynamic analyses were also used for liquefaction potential assessment soil classification dynamic soil properties under different earthquake excitations spectral amplification variation of soil predominant period and liquefaction potential of the study area were evaluated and mapped the produced maps showed that highest earthquake hazardous soil conditions are located along the shoreline and in the densely populated section of the southwestern part of the study area

temporal and spatial variations of gutenberg richter parameter and fractal dimension in western anatolia turkey abstract the temporal and spatial variations of gutenberg richter parameter b value and fractal dimension dc during the period 1900 2010 in western anatolia was investigated the study area is divided into 15 different source zones based on their tectonic and seismotectonic regimes we calculated the temporal variation of b and dc values in each region using zmap the temporal variation of these parameters for the prediction of major earthquakes was calculated the spatial distribution of these parameters is related to the stress levels of the faults we observed that b and dc values change before the major earthquakes in the 15 seismic regions to evaluate the spatial distribution of b and dc values 0 50 0 50 grid interval were used the b values smaller than 0 70 are related to the aegean arc and eskisehir fault the highest values are related to sultandagi and sandikli faults fractal correlation dimension varies from 1 65 to 2 60 which shows that the study area has a higher dc value the lowest dc values are related to the joining area between aegean and cyprus arcs burdur fethiye fault zone some have concluded that b values drop instantly before large shocks others suggested that temporally stable low b value zones identify future large earthquake locations the results reveal that large earthquakes occur when b decreases and dc increases suggesting that variation of b and dc can be used as an earthquake precursor mapping of b and dc values provide information about the state of stress in the region i e lower b and higher dc values associated with epicentral areas of large earthquakes

sedimentary environments of the simla group upper precambrian lesser himalaya and their palaeotectonic significance abstract the simla group of the western lesser himalaya comprises a prograding muddy delta sequence that was built by the collapse of a carbonate shelf during late precambrian time the simla sequence consists of a thick about 1500 m coarsening upwards clastic succession which is divisible into the basantpur chhaosa and sanjauli formations carbonate appears only in the basal formation basantpur formation three subfacies for the basal simla have been discerned a carbonate platform to the northeast basantpur subfacies shallow water with more clastic influence to the south kunihar subfacies and relatively deep water adjacent to a fault scarp to the northwest kashlog subfacies the first signs of deltaic sediments appear in the middle of the basantpur formation and are well developed in the overlying chhaosa formation the overall characteristics of the chhaosa facies are those of a delta front and distributary mouth bar where floods from distributaries and shelf storms lead to very rapid deposition mostly above wave base the uppermost sanjauli formation is relatively thick bedded coarse grained and more frequently cross bedded representing delta platform and distributary channel deposits a significant change in environment of deposition is observed in the overlying beds previously known as the upper sanjauli member and now being separated as the jagas formation the jagas facies suggests major uplifts and a climatic change to semi arid conditions the detritus of the simla delta came from the indian shield situated to the south of the delta most constituents indicate mature sediments with occasional lithoclasts of sedimentary and intraformational characters faulting presumably continued during the deposition of the simla group as is characteristic for rifted continental margins

pliocene and quaternary regional uplift in western turkey the gediz river terrace staircase and the volcanism at kula abstract along the upper reaches of the gediz river in western turkey in the eastern part of the aegean extensional province the land surface has uplifted by 400 m since the middle pliocene this uplift is revealed by progressive gorge incision and its rate can be established because river terraces are capped by basalt flows that have been k ar and ar ar dated at present the local uplift rate is 0 2 mm a 1 uplift at this rate began around the start of the middle pleistocene following a span of time when the uplift was much slower this was itself preceded by an earlier uplift phase apparently in the late late pliocene and early early pleistocene when the uplift rate was comparable to the present the resulting regional uplift history resembles what is observed in other regions and is analogously interpreted as the isostatic response to changing rates of surface processes linked to global environmental change we suggest that this present phase of surface uplift amounting so far to 150 m is being caused by the nonsteady state thermal and isostatic response of the crust to erosion following an increase in erosion rates in the late early pleistocene most likely as a result of the first large northern hemisphere glaciation during oxygen isotope stage 22 at 870 ka we suggest that the earlier uplift phase responsible for the initial 250 m of uplift resulted from a similar increase in erosion rates caused by the deterioration in local climate at 3 1 ma this uplift thus has no direct relationship to the crustal extension occurring in western turkey the rate and sense of which are thought not to have changed significantly on this time scale our results thus suggest that the present often deeply incised landscape of western turkey has largely developed from the middle pleistocene onwards for reasons not directly related to the active normal faulting that is also occurring the local isostatic consequences of this active faulting are instead superimposed onto this background of regional surface uplift modelling of this surface uplift indicates that the effective viscosity of the lower continental crust beneath this part of turkey is of the order of 1019 pa s similar to a recent estimate for beneath central greece the lower uplift rates observed in western turkey compared with central greece result from the longer typical distances of fluvial sediment transport which cause weaker coupling by lower crustal flow between offshore depocentres and eroding onshore regions that provide the sediment source

block rotation in western turkey 1 observational evidence western turkey is a region of rapid continental extension where extension rate increasing westward causes counterclockwise vertical vorticity and hence counterclockwise rotation around vertical axes on a regional scale field observations and seismicity of the past century are used to deduce positions and slip senses of major active oblique normal faults in this region which take up extension in the upper crustal brittle layer and allow fault bounded blocks to rotate around vertical axes the principal active normal faults in western turkey strike roughly east west near the aegean coast turning gradually toward westnorthwest eastsoutheast strike across 200 km distance inland to the east slip vector azimuths indicate typical extension direction on these faults is s18 8w they truncate a second set of faults with smaller displacement and roughly orthogonal strike and slip vector azimuth as well as subdividing the brittle layer into blocks that show little internal deformation some major oblique normal faults subdivide it into domains that show different neogene rotation around vertical axes some domains contain sets of major active oblique normal faults that bound blocks that are elongated angular and shaped like tilted dominoes these faults take up extension and can also take up rotation around vertical axes provided they and the blocks between them rotate around vertical axes at the same rate where adequate paleomagnetic observations are available they indicate these domains have rotated counterclockwise as expected by up to 40 roughly equal to the change in strike of the principal set of active faults between the aegean coast and the eastern edge of the actively extending zone however evidence is scarce for the right lateral strike slip expected in some kinematic models on a set of oblique normal faults that takes up extension and counterclockwise rotation instead each fault appears to have the component of strike slip necessary to enable it given its local strike to slip in ue direction in which the region is extending two domains that have rotated clockwise are approximately circular in plan view with diameter 90 km and are bounded by faults with variable orientation each comprises a single block with no internal major active faults

quaternary growth patterns of buyuk menderes and kucuk menderes deltas western turkey abstract detailed 3 5 khz and single channel seismic profiles and core data have shown that the continental shelf off the kucuk and buyuk menderes rivers was formed by prograding deltaic sediments during the last pleistocene glaciation the seismic profiles show that the present day shelf break denotes the topset to foreset transition of the latest pleistocene delta and that there are at least two older shelf breaks at depth that probably represent earlier delta progradation during glacially lowered sea level settings the general absence of coastal encroachment deposits between the shelf break and the present day 70 m isobath suggest that the last post glacial transgression was rapid between the 70 m isobath and the present coastline several lenticular seismic units are found shingled one on top of another they are interpreted as transgressive deltaic and marine deposits following the transgression kucuk menderes and buyuk menderes deltas were re established at the heads of the ancestral bays archaeological and historical evidence shows that between 6000 and 2000 yrs b p these deltas prograded within narrow grabens with fluvial processes predominating from 2000 yrs b p to present the deltas prograded relatively slowly and the present beach ridges dune systems were formed about 500 yrs b p the modern deltas are wave dominated and progradation has been largely halted where the grabens widen rapidly into larger coastal embayments tectonically controlled constrictions in the grabens are thus likely to be sites of preferential sand accumulation during basin subsidence

investigation on the tectonic significance of izmir uzunada fault zones and other tectonic elements in the gulf of izmir western turkey using high resolution seismic data abstract active faults at a range in scales are observed in different directions e w n s and ne sw in the extensional tectonic regime of the aegean region western turkey however mechanisms and types of faults in the gulf of izmir have not been investigated properly tectonic setting in the gulf together with the origin and characteristics of faults were studied in this study by integrating interpretation from various very high resolution acoustic data multibeam bathymetry and chirp very high resolution seismic acquired in the gulf of izmir the gulf of izmir has thick unconsolidated stratified sediment cover the water depth increases from the inner part se to the outer part nw of the gulf with complex sea floor morphology however northeastern part of the coastal region is very shallow because of the sedimentary influx transported by the gediz river the western margin and the southern part of the gulf were formed under the influence of uzunada uzun island and izmir faults respectively in the southern offshore there is only one e w directional normal fault dipping through the north and corresponding to the offshore segment of the izmir fault zone to the west the acoustic data enable identification of the uzunada fault zone extending as a simple lineament from near guzelbahce in the south but bifurcating toward the ne of the cicek archipelago and terminating with left lateral slip in the e ne of the hekim island after the sinistral strike slip the fault re extends in the nw direction untill the mid of uzunada as a single fault segment then the fault is observed as a bunch of many active fault segments like horse tail splays to the east of uzunada with n nw elongation through the outer gulf these segments were chronologically succeeded from the east to the west this progradational pattern is attributed to westward extension of the gulf of izmir with anti clockwise rotational escape of the anatolian plate in addition progradation of faults was controlled by the ne sw directional tear faults which may have played a key role in the shoreline extension and general pattern of the outer gulf islands a very young graben in the central part of the gulf also dislocated by the tear faults was observed parallel to the uzunada fault zone as another indicator of ongoing fan shaped opening of the gulf these tectonic elements are consistent with earlier interpretation of gps based observations indicating a four wheel gear system of rigid body rotations additionally a new fault extending from the far offshore of foca to suzbeyli village to the south was identified in this study its nw se extension is angular to the previous tectonic elements all these elements apparently project at least 10 km farther northward in the offshore foca where the earthquake epicenters cluster

neotectonic structures in the area offshore of alacati doganbey and kusadasi western turkey evidence of strike slip faulting in the aegean extensional province abstract about 400 km of new seismic reflection data has been acquired in the study region offshore of alacati doganbey and kusadasi which enables investigation of the active crustal deformation in this region the deformation onshore in western turkey is dominated by crustal extension and clear evidence of this process is also now available from this offshore area however in the onshore area adjacent to this study region evidence of active right lateral strike slip faulting has also previously been observed this strike slip faulting has previously been thought only to accommodate variations in extension between adjacent normal faults however in the offshore area there is considerable evidence of zones of deformation some of which may link to the strike slip faulting onshore suggesting that strike slip faulting may be of greater importance in this region than previously thought

shallow structure and recent evolution of the aegean sea a synthesis based on continuous reflection profiles abstract a dense grid of continuous seismic reflection profiles partly calibrated with drilling results has allowed construction of a structural outline of the entire aegean sea in the north aegean we observe a clear difference between the thickly sedimented northern margin basins and the steep slopes of the trough margin of the southern north aegean the trough itself comprises a series of separate tectonic depressions resulting from an apparent transtensional motion the central aegean consists of a complex tectonic puzzle caused by the prevailing extension incipient strike slip faulting sub parallel to the north aegean trough trend may however affect its eastern anatolian domain three main structural areas characterize the southern aegean comparable structural directions cut across this chiefly extensional basin but one fault system may be prevailing over the others depending on the area the central cretan sea results from the interaction of at least two distinct extensions these were superimposed on previous mostly e w structural trends generated during the inception of the southern hellenic subduction and led to the present day predominant sw ne trending extension as a hypothesis we propose that the overall late miocene present evolution of the aegean sea is directly dependent on two geodynamic processes to the southeast of the area collision between arabia and turkey leads to the lateral westward expulsion of the aegean continental crust and to the west hellenic subduction is still active

global positioning system constraints on plate kinematics and dynamics in the eastern mediterranean and caucasus we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1997 at 189 sites extending east west from the caucasus mountains to the adriatic sea and north south from the southern edge of the eurasian plate to the northern edge of the african plate sites on the northern arabian platform move 18 2 mm yr at n25 5 w relative to eurasia less than the nuvel 1a circuit closure rate 25 1 mm yr at n21 7 w preliminary motion estimates 1994 1997 for stations located in egypt on the northeastern part of africa show northward motion at 5 6 2 mm yr also slower than nuvel ia estimates 10 1 mm yr at n2 4 e eastern turkey is characterized by distributed deformation while central turkey is characterized by coherent plate motion internal deformation of 2 mm yr involving westward displacement and counterclockwise rotation of the anatolian plate the anatolian plate is de coupled from eurasia along the right lateral strike slip north anatolian fault naf we derive a best fitting euler vector for anatolia eurasia motion of 30 7 0 8 n 32 6 0 4 e 1 2 0 1 myr the euler vector gives an upper bound for naf slip rate of 24 1 mm yr we determine a preliminary gps arabia anatolia euler vector of 32 9 1 2 n 40 3 1 1 e 0 8 0 2 myr and an upper bound on left lateral slip on the east anatolian fault eaf of 9 1 mm yr the central and southern aegean is characterized by coherent motion internal deformation of 2 mm yr toward the sw at 30 1 mm yr relative to eurasia stations in the se aegean deviate significantly from the overall motion of the southern aegean showing increasing velocities toward the trench and reaching 10 1 mm yr relative to the southern aegean as a whole

late quaternary tectonic and sedimentary history of outer izmir and candarli bays western turkey abstract air gun and 3 5 khz seismic profiles from the eastern aegean sea off turkey show that the continental shelf of outer izmir and candarli bays is formed by several superimposed deltaic sequences during times of lowered sea level associated with late quaternary glaciations deltas prograded seaward more than 60 km from their present positions foreset progradation ceased with the rise of sea level in interglacial and post glacial times and deltas were reestablished far inland in drowned river valleys these major transgressions resulted in unconformities within the superimposed prograded delta sequences the most recent three unconformities are correlated with the beginning of oxygen isotope stages 5 3 and 1 and provide chronostratigraphic markers for a detailed analysis of sedimentation patterns in the late quaternary the coastal shelf and basins are subsiding at an average rate of about 1 m per 1000 years this tectonic subsidence manifests itself as widespread normal block faulting which can be related to the pre miocene structural framework of the region

the aegean sea we summarize briefly the main features of a kinematic model of evolution of the aegean area since 13 ma the formation of the aegean sea by extensional tectonics is related to the subduction of the mediterranean floor below the hellenic arc we then make a quantitative estimate of vertical movements in the aegean area on the basis of geological data and demonstrate that the outer arc was built since the beginning of this episode of subduction by vertical uplift the easiest way to explain the uplift is by underplating finally we discuss briefly the dynamics of the subduction marginal sea formation processes in this continental collision framework