esr dating of raised coral reefs from kish island persian gulf electron spin resonance esr dating of raised coral reefs from kish island persian gulf iran was used for the calculation of uplift rates from the methodological point of view it has been demonstrated that concentrations of uranium as needed for the calculation of dose rates determined by instrumental neutron activation analyses were significantly lower than the results of inductively coupled plasma mass spectrometry and are probably systematically underestimated the esr ages for the corals show no increase with elevation as was expected due to field observations this apparent discrepancy is explained by the dicyclic nature of the palaeo reef average uplift rates for kish island are between 0 13 and 0 24 mm a 1 this is consistent with previous estimates based on 230th 234u dating of raised marine deposits from the nearby iranian mainland and qeshm island strait of hormuz but contrary to results based on 14c dating that predicted uplift rates as high as 3 mm a 1 in that area it is once more demonstrated that 14c dates 20 ka from this context often have to be interpreted as minimum ages

a new contribution to the late quaternary tephrostratigraphy of the mediterranean aegean sea core lc21 tephra layers preserved in marine sediments can contribute to the reconstruction of volcanic histories and potentially act as stratigraphic isochrons to link together environmental records recent de velopments in the detection of volcanic ash tephra at levels where none is macroscopically visible so called crypto tephra have greatly enhanced the potential of tephrostratigraphy for synchronising environmental and archaeological records by expanding the areas over which tephras are found in this paper crypto tephra extraction techniques allow the recovery of 8 non visible tephra layers to add to the 9 visible layers in a marine sediment core lc21 from the se aegean sea to form the longest single core record of volcanic activity in the aegean sea using a novel shard specific methodology sources of the tephra shards are identified on the basis of their major and trace element single shard geochemistry by comparison with geochemical data from proximal mediterranean volcanic stratigraphies the results indicate that the tephra layers are derived from 14 or 15 separate eruptions in the last ca 161 ka bp 9 from santorini 2 or 3 from kos yali or nisyros 2 from the campanian province and one from pan telleria the attributions of these tephra layers indicate that 1 inter plinian eruptions from santorini may have produced regionally significant tephra deposits 2 marine tephrostratigraphies can provide unique and invaluable data to eruptive histories for island volcanoes and 3 tephra from both pantelleria and campania may be used to correlate marine records from the aegean sea to those from the tyrrhenian adriatic and ionian seas

tectonics of the central zagros iran deduced from microearthquake seismicity summary microearthquakes in central zagros recorded for 7 weeks in 1997 lie in a 6 8 km zone that is likely located beneath 11 km of sediments they are not located on an active decollement between the sediments and the crystalline crust but rather define a pattern of nnw sse trending lineaments parallel to the fold axes observed at the surface the spacing between the seismic lineaments is 15 20 km and therefore different from that between the folds 10 15 km which suggests that there is not a simple relationship between the two focal mechanisms and precise relative locations are consistent with nw se striking reverse faulting connected by nnw sse striking right lateral strike slip faults the dip of the reverse faults is not certain but is likely ne for the northernmost faults the strain pattern deduced from the p axes is remarkably similar to the shortening deduced from gps based geodesy suggesting that microearthquakes are the response of the prefractured brittle crust to strain rather than localized on single active faults

active faults in the zagros and central iran abstract active tectonic movements in the northwestern zagros include right lateral slip at the rate of about 10 mm a along the main recent fault which inherits the position of the main thrust now inactive and active thrusting and accompanying folding distributed between several zones southwest of the main recent fault in the southeastern zagros the fars province there are several right lateral faults that extend n s obliquely to the overall trend of the zagros fault and fold belt these may be either branches of the main recent fault or faults accommodating relative broadening of the outer zagros in its southeastern segment the main thrust in the southeastern zagros also remains inactive the ipak north tehran and mosha fault zones and several minor structures in the eastern alborz form the e w trending active fault system with combined reverse and left lateral slip on the ipak and mosha zones lateral movements with the late quaternary mean rate exceeding 1 mm a dominate over vertical fault movements together with right lateral faults stretching northeast of zagros the faults of the alborz may accommodate east directed motion of the iranian microplate

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

volcanology and petrology of volcanic products from the island of milos and neighbouring islets abstract new geochronological and volcanological data from volcanics of the island group of milos south aegean active volcanic arc allow four main cycles of volcanic activity to be distinguished ranging in age between 3 5 and 0 1 m y b p the oldest volcanic activity consists almost totally of pyroclastics and submarine products followed by subaerial ones the eruptive centers migrated in time and concentrated during the most recent volcanic phase in the central part of milos and on the island of antimilos the oldest products are dominated by andesites and dacites while the most recent ones mainly consist of rhyolites the volcanic evolution and the geochemical characters of the erupted products suggest that the feeding system of the oldest volcanism was located in the deep continental crust where contamination and fractional crystallization jointly occurred the younger cycle of volcanic activity was fed from small and relatively shallow magma chambers where contamination processes played a minor role these magma bodies are considered to responsible for the shallow thermal anomaly giving rise to the high enthalpy field on milos

central zagros fold thrust belt iran new insights from seismic data field observation and sandbox modeling 1 we present five generalized cross sections across the central zagros fold and thrust belt iran these sections show that the fold geometry varies significantly both horizontally and vertically the style is closely related to the changes in the mechanical behavior of the lithostratigraphic horizons and in particular to the presence of intermediate decollements within the sedimentary pile restoration of the sections shows amounts of shortening of the same order from one section to the other however it appears to be unequally distributed suggesting variations in basal decollement shear strength analogue modeling has been performed to systematically investigate the effect of an intermediate decollement level at different depths on the style of folding the models demonstrate that the position of intermediate decollements is an important factor controlling both structural style and fold wavelength models with shallow intermediate decollement show regularly and widely spaced anticlines in these models the fold wavelength depends directly on the thickness of the dominant competent layer and short wavelength superficial structures mask broad anticlines at depth models with deep intermediate decollement are characterized by the rapid propagation of deformation with small rate of shortening along this decollement influencing localization of forthcoming anticlines in the upper levels such propagation favors the development of duplexes and multiwavelength folds on this basis fold kinematics in central zagros is discussed using the variation of structural style along different folds as an indicator of the sequence of deformation detachment folding is the main folding style at least for the initial stages of deformation and thrust faults developed only at later stages some of these faults branched on decollement levels express the progression of folding whereas others are linked to late basement faults cutting through early structures in general the decollement levels are activated sequentially from deeper horizons to shallower ones however in one case gachsaran decollement a shallow decollement is activated during the early stages of folding and then abandoned during the subsequent evolution

influence of secular variation of the geomagnetic field on production rates of in situ produced cosmogenic nuclides abstract scaling factors are presented that allow a full description of the cosmic ray flux modulation during secular variation of the geomagnetic field these scaling factors are analogous to those determined in a similar work dunai t j earth planet sci lett 2000 176 157 169 that were accurate for field strengths equivalent to present day field strength but cannot accommodate field strength variations strategies to derive the relevant geomagnetic field parameters are discussed and are tested with existing production rate calibrations for 3 he a production rate of 103 4 2 atoms g olivine yr sea level and for zero cutoff rigidity was derived from calibration sites from hawaii western usa and canary islands covering the time range of 2 281 kyr

geometric analysis of fold development in overthrust terranes abstract fault bend folding fault propagation folding and detachment or decollement folding are three distinct scenarios for fold thrust interaction in overthrust terranes simple kink hinge models are used to determine the geometric associations implicit in each scenario bedding maintains constant thickness in the models except in the forelimb of the fold the forelimb is allowed to thicken or thin without limit the models address individual folds and the calculated fold geometries are balanced structures each mode of fold thrust interaction has a distinct set of geometric relationships final fold geometry is adequate in itself to discern many fault bend folds this is not the case for fault propagation and detachment folds these two fold forms have very similar geometric relationships some knowledge of the nature of the underlying thrust or decollement zone is usually needed to distinguish between them the geometry of a fold is altered in a predictable fashion by transport through an upper ramp hinge and by fault parallel shearing of the structure the shearing results in a tighter fold whereas transport through the ramp hinge produces a broader fold the viability of the geometric analysis technique is demonstrated through its application to a pair of detachment folds from the canadian cordillera the geometric analysis is also used to evaluate cross sections through subsurface structures in an example from the turner valley oil field the analysis indicates how the interpretation should be altered so as to balance the cross section the analysis reveals hidden assumptions and specific inconsistencies in structural interpretations

revisiting the y 3 tephrostratigraphic marker a new diagnostic glass geochemistry age estimate and details on its climatostratigraphical context the y 3 tephra is a crucial stratigraphic marker within the central mediterranean region that falls close to the marine isotope stage 3 2 transition and a cooling event proposed as a correlative of the north atlantic heinrich stadial 3 hs3 consequently this tephra offers great potential to assess any leads and lags in environmental responses to this abrupt climatic transition new grain specific glass analysis empa and la icp ms of the type locality y 3 tephra recorded in the ionian sea confirms its origin from campi flegrei cf but reveals that it is compositionally different from the previously suggested proximal equivalent the vra eruptive unit verdolino valley cf consequently the 40ar 39ar age of the vra should not be exported distally to the y 3 tephra instead we propose a new robust age for the y 3 tephra following its identification in the tenaghi philippon sedimentary record ne greece a bayesian based 14c age model from tenaghi philippon provides a distal age of 28 680 29 420 cal yrs bp for the y 3 tephra the identification of this tephra in ne greece markedly extends its known eastern dispersal whilst its stratigraphic position falls within the latter part of a period of low tree pollen percentages related to dry stadial conditions this new age and environmental context suggest that this marker postdates the onset of hs3 in the eastern mediterranean region by 2300 years

active deformation within the zagros mountains deduced from gps measurements we present and interpret the results of global positioning system gps measurements at 35 stations in and beside the zagros mountain belt sw iran for three campaigns ending march 1998 december 1999 and june 2001 preliminary motion estimates show clearly the change in character along the strike of the belt stations to the se move at 13 22 3 mm a 1 towards n 7 5 e with respect to eurasia most of the shortening indicated by the gps velocities seems to occur in the se zagros along two major seismic zones and along the zagros front to the nw stations move oblique to the trend of the belt towards n 12 8 w at 14 19 3 mm a 1 most of the shortening in the nw zagros seems to occur along the mountain front fault with its major earthquakes as well as along the zagros front the change in direction and magnitude of the velocity vectors across the north south trending kazerun and karebas faults involves extension of up to 4 mm a 1 along the strike of the zagros belt

long term fluvial incision rates and postglacial river relaxation time in the french western alps from 10be dating of alluvial terraces with assessment of inheritance soil development and wind ablation effects studying river long profile development as a response to tectonic and climatic controls requires reliable age dating of paleo profile remnants preserved as river terraces cosmic ray exposure cre dating often represents the only method available to date river terraces but the interpretation of cosmogenic nuclide concentrations is complicated by pre depositional inheritance and post depositional disturbance of the terrace deposits through pedogenesis and surface inflation or deflation here we use cosmogenic 10be measurements to date alluvial terraces in the french western alps in order to estimate river incision rates and to infer river response to climatic fluctuations and tectonic forcing we assess inheritance by constructing 10be concentration vs pebble depth profiles and use a monte carlo technique to estimate terrace ages we find that inheritance is negligible on all terraces enabling us to date terraces as young as 5 ky terraces that predate the last glaciation experienced intense pedogenesis and wind ablation which led to significant scatter in the 10be concentrations of surface samples we assess these effects using a model of 10be ingrowth and show that the oldest cre ages of surface clasts are close to the probable terrace age we study two catchments which have undergone varying degrees of glacial disruption the buech river experienced variations in runoff and sediment flux during the last glaciation as well as occasional ice dammings of its outlet its upper terraces record incision rates averaged over 190 ky of 0 8 mm yr consistent with denudation rates estimated in the surrounding areas and suggesting long term stability of river incision rates climatic forcing is well documented for the drac river which was repeatedly dammed by glaciers during cold periods its postglacial incision history was triggered by an 800 m drop in base level following ice dam disappearance long profile development by knickpoint propagation explains the time lag of 2 5 ky between this base level drop and terrace abandonment upstream as well as subsequent peak incision rates of 6 cm yr followed by a gradual decrease in incision rates the present knickpoint location 55 km upstream from the glacial damming site enables us to calculate a fluvial response time of 15 20 ky controlled by knickpoint propagation rates of several meters per year within the drac river

first evidence of a distal early holocene ash layer in eastern mediterranean deep sea sediments derived from the anatolian volcanic province article i nfo a hitherto unknown distal volcanic ash layer has been detected in a sediment core recovered from the southeastern levantine sea eastern mediterranean sea radiometric stratigraphic and sedimentological data show that the tephra here termed as s1 tephra was deposited between 8970 and 8690 cal yr bp the high silica rhyolitic composition excludes an origin from any known eruptions of the italian aegean or arabian volcanic provinces but suggests a prevailing central anatolian provenance we compare the s1 tephra with proximal to medial distal tephra deposits from well known mediterranean ash layers and ash fall deposits from the central anatolian volcanic field using electron probe microanalyses on volcanic glass shards and morphological analyses on ash particles we postulate a correlation with the early holocene dikkartin dome eruption of erciyes dag volcano cappadocia turkey so far no tephra of the central anatolian volcanic province has been detected in marine sediment archives in the eastern mediterranean region the occurrence of the s1 tephra in the south eastern part of the levantine sea indicates a wide dispersal of pyroclastic material from erciyes dag more than 600 km to the south and is therefore an important tephrostratigraphical marker in sediments of the easternmost mediterranean sea and the adjacent hinterland

interseismic strain accumulation on the himalayan crustal ramp nepal the departement of mines and geology has been monitoring the seismicity of the central himalayas of nepal since 1985 intense microseismicity and frequent medium size earthquakes ml 4 tend to cluster beneath the topographic front of the higher himalaya this 10 20km deep seismicity also correlates with a zone of localized uplift that has been evidenced from geodetic data both microseismic and geodetic data indicate strain accumulation on a mid crustal ramp that had been previously inferred from geological and geophysical evidence this ramp connects a flat decollement under the lesser and sub himalaya with a deeper decollement under the higher himalaya and probably acts as a geometric asperity where strain and stress build up during the interseismic period the large himalayan earthquakes could nucleate there and probably activate the whole flat and ramp system up to the blind thrusts of the sub himalaya

young pumice deposits on nisyros greece the island of nisyros aegean sea consists of a silicic volcanic sequence upon a base of mafic andesitic hyaloclastites lava flows and breccias we distinguish two young silicic eruptive cycles each consisting of an explosive phase followed by effusions and an older silicic complex with major pyroclastic deposits the caldera that formed after the last plinian eruption is partially filled with dacitic domes each of the two youngest plinian pumice falls has an approximate dre volume of 2 3 km3 and calculated eruption column heights of about 15 20 km the youngest pumice unit is a fall surge flow surge sequence laterally transitional fall and surge facies as well as distinct polymodal grainsize distributions in the basal fall layer indicate coeval deposition from a maintained plume and surges planar bedded pumice units on top of the fall layer were deposited from high energy dry steam propelled surges and grade laterally into cross bedded finegrained surge deposits the change from a fall to a surge flow dominated depositional regime coincided with a trend from low temperature argillitic lithics to high temperature epidote and diopside bearing lithic clasts indicating the break up of a high temperature geothermal reservoir after the plinian phase the transition from a maintained plume to a surge ash flow depositional regime occurred most likely during break up of the high temperature geothermal reservoir during chaotic caldera collapse the upper surge units were possibly erupted through the newly formed ringfracture

a unified kinematic model for the evolution of detachment folds abstract detachment folds represent a major structural element in a number of fold belts they are common in the jura mountains the zagros fold belt the central appalachian fold belt the wyoming fold belt the brooks range the parry islands fold belt and parts of the subandean belt these structures form in stratigraphic packages with high competency contrasts among units the competent upper units exhibit parallel fold geometries whereas the weak lower unit displays disharmonic folding and significant penetrative deformation two distinct geometric types disharmonic detachment folds and lift off folds have been recognized however these structures commonly represent different stages in the progressive evolution of detachment folds the structures first form by symmetric or asymmetric folding with the fold wavelength controlled by the thickness of the dominant units volumetric constraints require sinking of units in the synclines and movement of the ductile unit from the synclines to the anticlines continuing deformation results in increasing fold amplitudes and tighter geometries resulting from both limb segment rotation and hinge migration initially limb rotation occurs primarily by flexural slip folding but in the late stages of deformation the rotation may involve significant internal deformation of units between locked hinges the folds eventually assume tight isoclinal geometries resembling lift off folds variations in the geometry of detachment fold geometry such as fold asymmetry significant faulting and fold associated with multiple detachments are related to variations in the mechanical stratigraphy and pre existing structure

chronology and rates of faulting of ventura river terraces california new evidence concerning the chronology of four late pleistocene terraces of the ventura river near oak view california that are vertically offset and tilted by reverse and reverse flexural slip faults provides a means of estimating rates of fault movement and downcutting by the ventura river radiocarbon ages of charcoal contained within terrace deposits date two of the terraces correlation of soils that have developed on terrace deposits and extrapolation of the rate of vertical displacement of the arroyo parida santa ana fault not a flexural slip fault date the others resulting age estimates for the four main late pleistocene terraces are qt5b 30 000 qt6a 38 000 qt6b 54 000 and qt6c 92 000 yr b p vertical slip rates on flexural slip faults range from 0 3 to 1 1 mm yr and apparently are related to the rate form and mechanics of folding of the north limb of the ayers creek canada larga syncline average rates of downcutting of the ventura river for several intervals during the late pleistocene estimated from the chronology and relative elevation of river terraces north of the arroyo panda santa ana fault upstream from the zone of faulting vary from 0 5 to 1 3 mm yr the range in rates probably reflects variations in local uplift as well as adjustments to changing eustatic sea level climatic conditions and or regional deformation of the western transverse ranges the average rate of downcutting of the ventura river north of the zone of flexural slip faulting is 0 8 mm yr compared with 1 2 to 2 2 mm yr in the deformation zone immediately to the south this apparently indicates that during tectonic deformation there is an approximate balance between the rate of uplift due to faulting and folding and the rate of downcutting by the fluvial system

cenozoic evolution of neotethys and implications for the causes of plate motions africa north america eurasia plate circuit rotations combined with red sea rotations and new estimates of crustal shortening in iran define the cenozoic history of the neotethyan ocean between arabia and eurasia the new constraints indicate that arabia eurasia convergence has been fairly constant at 2 to 3 cm yr since 56 ma with slowing of africa eurasia motion to 1 cm yr near 25 ma coeval with the opening of the red sea ocean closure occurred no later than 10 ma and could have occurred prior to this time only if a large amount of continental lithosphere was subducted suggesting that slowing of africa significantly predated the arabia eurasia collision these kinematics imply that africa s disconnection with the negative buoyancy of the downgoing slab of lithosphere beneath southern eurasia slowed its motion the slow steady rate of northward subduction since 56 ma contrasts with strongly variable rates of magma production in the urumieh dokhtar arc implying magma production rate in continental arcs is not linked to subduction rate

local erosion rates versus active tectonics cosmic ray exposure modelling in provence south east france over the past decade in situ produced cosmogenic nuclides have revolutionised the study of landscape evolution in particular numerous studies have demonstrated that in active tectonic settings cosmic ray exposure dating of deformed or displaced geomorphic features makes it possible to quantify long term deformation rates in western european countries erosion due to climatically driven processes and human activities is probably the factor that most limits the accuracy of exposure ages and landscape modification rates in this study we present the results of a depth profiling technique applied to alluvial terraces located along the rhone and the moyenne durance rivers the expected decrease with depth of the measured 10be concentrations has been modelled using a 2 inversion method in order to constrain the exposure history of the alluvial sediments the results suggest that 1 over the quaternary the local surface erosion rates including both regional uplift and climatically driven processes acting on landforms are on the order of 30 m myr in southeastern france and 2 providing a fairly good bracketing of the exposure age the modelled abandonment age of alluvial terraces affected by the moyenne durance fault allows estimating incision rates comparing the alluvial terrace elevations with topographic river profiles and a minimum vertical slip rate value of roughly 0 02 mm yr for the southern segment of the moyenne durance fault

magnetostratigraphy of miocene pliocene zagros foreland deposits in the front of the push e kush arc lurestan province iran abstract the timing of the deformation in the zagros simply folded belt is poorly constrained because of the lack of an accurate absolute chronology of the syntectonic sedimentary sequences the foreland basin infill at the front of the push e kush arc is composed of fine grained fluvial plain deposits agha jari fm and coarse conglomerates at the top of the section bakhtyari fm a magnetostratigraphic study was carried out in a composite section spanning about 2800 m in order to date growth strata and to constrain the timing of the deformation in the mountain front flexure mff magnetostratigraphic correlation of the base of the agha jari fm with chron c5a yields an age of 12 8 to 12 3 ma for this base the transition to the conglomerates of the bakhtyari fm correlates with the upper gauss chron c2an at approximately 3 ma the deposition age of the top of the preserved bakhtyari fm is extrapolated around the pliocene pleistocene boundary the base of the agha jari fm growth strata and thus the beginning of the deformation in the front of the push e kush arc is dated at 8 1 7 2 ma the topmost preserved bakhtyari is folded in the ne flank of the changuleh anticline and is unconformably overlying the sw flank of the anaran anticline this indicates that the tectonic deformation in the front of the push e kush arc was active at least during 5 my the mff is a relatively long lived structure active from 8 1 to 7 2 ma to about the pliocene pleistocene boundary partly synchronous with the changuleh anticline to the foreland after mff tectonic cessation only the changuleh anticline remained active

paleomagnetic stratigraphy and radiometric dating of the pliocene volcanic rocks of aegina greece the island of aegma includes some of the oldest volcanic rocks in the south hellenic arc previous radiometric dates range from 3 87 to 4 4 ma the volcanic sequence is divided into nine units on the basis of field relations petrography and geochemistry and the characteristic paleomagnetic polarity of each unit has been determined two new radiometric dates 2 1 and 3 9 ma show that the volcanism spans the pliocene a detailed chronology is proposed using the paleomagnetic data which places the most voluminous volcanism in the mid pliocene

marine tephra from the cape riva eruption 22 ka of santorini in the sea of marmara abstract a discrete tephra layer has been discovered in three marine sediment cores from the sea of marmara eastern mediterranean the rhyodacitic glass chemistry and the stratigraphical position suggest a santorini provenance and in particular a correlation with the marine y 2 tephra that is known from the southern aegean sea and eastern levantine basin this tephra represents the distal facies of the cape riva eruption of santorini which has been dated by 14c on land at 21 950 cal yr bp hitherto the y 2 tephra has been detected only in marine sediment cores recovered south to southeast of its volcanic source the new occurrence in the sea of marmara approximately 530 km nne of the santorini eruptive centre suggests a more north easterly dispersal of fallout products of the cape riva eruption than previously supposed

cenozoic post collisional brittle tectonic history and stress reorientation in the high zagros belt iran fars province abstract the zagros fold and thrust belt of sw iran is among the youngest continental collision zones on earth collision is thought to have occurred in the late oligocene early miocene followed by continental shortening the high zagros belt hzb presents a neogene imbricate structure that has affected the thick sedimentary cover of the former arabian continental passive margin the hzb of interior fars marks the innermost part of se zagros trending nw se that is characterised by higher elevation lack of seismicity and no evident active crustal shortening with respect to the outer sw parts this study examines the brittle structures that developed during the mountain building process to decipher the history of polyphase deformation and variations in compressive tectonic fields since the onset of collision analytic inversion techniques enabled us to determine and separate different brittle tectonic regimes in terms of stress tensors various strike slip compressional and tensional stress regimes are thus identified with different stress fields brittle tectonic analyses were carried out to reconstruct possible geometrical relationships between different structures and to establish relative chronologies of corresponding stress fields considering the folding process results indicate that in the studied area the main fold and thrust structure developed in a general compressional stress regime with an average n032 direction of 1 stress axis during the miocene strike slip structures were generated under three successive strike slip stress regimes with different 1 directions in the early miocene n053 late miocene early pliocene n026 and post pliocene n002 evolving from pre fold to post fold faulting tensional structures also developed as a function of the evolving stress regimes our reconstruction of stress fields suggests an anticlockwise reorientation of the horizontal 1 axis since the onset of collision and a significant change in vertical stress from 3 to 2 since the late stage of folding and thrusting a late right lateral reactivation was also observed on some pre existing belt parallel brittle structures especially along the reverse fault systems consistent with the recent n s plate convergence however this feature was not reflected by large structures in the hzb of interior fars the results should not be extrapolated to the entire zagros belt where the deformation front has propagated from inner to outer zones during the younger events

correlation of widespread holocene and pleistocene tephra layers from newberry volcano oregon usa using glass compositions and numerical analysis abstract during the last ca 500 000 years newberry volcano in oregon has produced at least 50 rhyolitic and dacitic tephras ranging from locally distributed pumice rings and cones to ignimbrites to widely dispersed plinian fallout deposits to date 13 tephra units with ages ranging from about 1525 14c years bp to 200 000 years bp have been traced to 20 sites across five western states of the usa correlations have been established by applying similarity coefficient and discriminant function analysis to major element compositions of tephra derived glasses determined by electron microprobe analysis newberry pumice correlates to four locations in oregon and idaho east lake or central pumice cone tephra correlates to two locations in oregon paulina creek ice quarry 9912d 9920c 984f 984g5 9917c and 9881c tephras correlate to ash beds at summer lake oregon paulina creek tephra also correlates to several locations in northern california and is equivalent to the olema ash bed tephra 9917c is very similar to tephras k and d at pringle falls oregon lava pass or a related tephra correlates to an unnamed tephra in the bonneville basin utah

geomagnetic dipole moment and 10be production rate intercalibration from authigenic 10be 9be for the last 1 3 ma 1 a synthesis of authigenic 10be 9be ratio records constructed from sedimentary sequences deposited over the last 300 ka in the north east atlantic and over the 500 1300 ka bp interval in the west equatorial pacific ocean is compared with proxies of the geomagnetic moment variations over the same time intervals these proxies consist in 1 relative paleointensity records obtained from the same sediments 2 a seafloor magnetization record derived from magnetic anomalies and 3 an absolute virtual dipole moment vdm record constructed from an updated database of absolute paleointensities the authigenic 10be 9be ratio records document the occurrence of the paleomagnetic events excursions and reversals reported for these time intervals by paleomagnetic studies reconstructions of 10be 9be derived magnetic moment records based on theoretical and empirical relationships between 10be 9be ratio and absolute vdm allow establishing 10be derived vdm records that exhibit the same overall structures as the geomagnetic proxy records

improved age estimates for key late quaternary european tephra horizons in the reset lattice abstract the research project response of humans to abrupt environmental transitions reset used tephra layers to tie together and synchronise the chronologies of stratigraphic records at archaeological and environmental sites with the increasing importance of tephra as chronological markers in sedimentary sequences both in this project and more generally comes a requirement to have good estimates for the absolute age of these volcanic horizons this paper summarises the chronology of the key tephra in the reset tephra lattice in the time range 10 60 ka bp from the existing literature from papers produced as part of the reset project and reanalysis conducted for this paper the paper outlines the chronological approach taken to the dating of tephra within the reset project and the basis for further work as part of the intimate integrating ice core marine and terrestrial records initiative for each of the tephra layers in the lattice the existing literature is discussed and where relevant date estimates updated using the latest radiocarbon calibration curves intcal13 and marine13 and methods maps show the approximate extent of tephra finds giving a visual indication of the coverage of the lattice in different time periods

focal mechanism solutions for earthquakes in iran abstract focal mechanism solutions derived by using p wave first motion directions read from seismograms of worldwide standardized stations network wwssn are presented for 36 earthquakes in iran in many cases the first motion data admit more than one solution these solutions along with previously published solutions for 18 other earthquakes are graphically summarized on a tectonic map of iran

modelling river discharge and precipitation from estuarine salinity in the northern chesapeake bay application to holocene palaeoclimate long term chronologies of precipitation can provide a baseline against which twentieth century trends in rainfall can be evaluated in terms of natural variability and anthropogenic influence howev

variation of structural style and basin evolution in the central zagros izeh zone and dezful embayment iran abstract structural style and its relationship to sedimentary facies and the evolution of sedimentary depocenters since late cretaceous times have been studied on the basis of one regional balanced transect and several updated isopach maps in the izeh zone and the dezful embayment central zagros this study relies on fieldwork data existing geological maps seismic data and well information a new structural classification for part of the zagros sedimentary cover is presented to highlight the different mechanical behavior of the formations in the stratigraphic column it shows the existence of several local decollement levels activated during folding these decollement levels separate lithotectonic units which accommodate shortening in different ways the lower paleozoic is the basal decollement level throughout the studied area triassic evaporites albian shales eocene marls and miocene evaporites can act as intermediate decollement levels and present variable facies in the central zagros lateral facies and thickness variations the sedimentary overburden and the close relationship with inherited fault patterns influenced the wavelength amplitude and style of folding in the study area furthermore surface structures do not necessarily coincide with deeper objectives where these disharmonic levels are involved in folding the evolution of sedimentary depocenters from the late cretaceous obduction episode until early miocene collision is described based on updated isopach maps and tectonic subsidence curves this analysis shows continuous compression and movements along n s and nw se trending faults in the zagros basement which predate the neogene zagros folding and influence sedimentation history it also indicates a southwestward migration of the depocenters through time in addition to the basement involvement below some folds during the zagros orogeny

examination of surface exposure ages of antarctic moraines using in situ produced 10be and 26al concentrations of 10be t12 1 5 106 y and 26a1 t12 0 72 106 y have been determined by accelerator mass spectrometry ams in a suite of quartz samples taken from sandstone boulders in several moraines in arena valley a dry valley adjacent to the taylor glacier in the quatermain mountains southern victoria land east antarctica these isotopes are produced in surficial quartz by cosmic ray spallation of o and si the concentrations in these samples ranged from 6 1 105 to 3 0 107 at g 1 for 10be and from 9 4 106 to 1 2 108 at g 1 for 26a1 depending upon the extent of exposure at the surface analyses of 10be in several samples from a single moraine at altitudes ranging from 1300 to 1650 m permitted an estimation of the air attenuation pathlength of cosmic ray neutrons the value of 142 96 41 g cm 2 is consistent with other published values production rates of 17 6 4 at g 1 y 1 for 10be and 113 54 16 at g 1 y 1 for 26a1 at 1300 m and 87 s and a 26al 10be production ratio of 6 5 1 3 1 3 were calculated from the data these values correspond to sea level production rates at high geomagnetic latitude of 6 4 at g 1 y 1 and 41 7 at g 1 y 1 for 10be and 26a1 respectively consistent with determinations based on 11 ky glacially polished surfaces in the sierra nevada in california these production rates imply exposure ages for the various moraines ranging from 50 ky to 2 5 my in accordance with other geological evidence the 10be and 26al ages of these rocks compare favorably with those found using a similar dating method based on in situ production of 3he examination of the 3he concentrations in conjunction with the present data set yields an estimate of 3he production of 230 8540 at g 1 y 1 corresponding to 85 31 15 at g 1 y 1 at sea level this is lower than previously reported values of 240 60 at g 1 y 1 and 190 at g 1 y 1 scaled to sea level and high geomagnetic latitude based respectively on volcanic flows less than 2000 years old at low latitude and samples collected from 14 400 year old volcanic flows this discrepancy is likely due to diffusive losses which may become significant up to 50 for surface exposure ages on the order of 2 0 my nevertheless the general correlations among the three isotopes suggest that 3he does not suffer gross losses through diffusion

discovery of a huge sector collapse at the nisyros volcano greece by on land and offshore geological structural data abstract this study uses on land and offshore geological and structural data to demonstrate that a huge lateral collapse involved the se flank of nisyros volcano the collapse beheaded the summit part of the volcano and also involved the submarine portion of the slope producing a large debris avalanche deposit with a volume of about 1 km3 which has been recognized on the sea floor on land stratigraphic and structural data indicate that a thick succession of lava flows nikia lavas was emplaced in a huge horseshoe shaped depression open seaward and extending below the sea the magma feeding system in the volcano pre dating and following the collapse was structurally influenced by a dominant ne sw direction which is perpendicular to the newly recognised sector collapse the ne sw structural trend is consistent with the regional tectonic structures found offshore around nisyros and with the related nw se extension direction we suggest that the lateral magma pressure produced by repeated magma injections along tectonic discontinuities contributed to destabilise the volcano flank the occurrence of a pyroclastic deposit that mantled the scar left by the collapse suggests that a magma batch might have been injected inside the volcano and triggered the collapse the lavas of the pre collapse edifice have been deposited in alternating submarine and subaerial environments suggesting that vertical movements might also be a major triggering mechanism for large lateral collapses recognition of this phenomenon is particularly important in recent active island or coastal volcanoes as it can trigger tsunamis

the marine isotope stage 1 5 cryptotephra record of tenaghi philippon greece towards a detailed tephrostratigraphic framework for the eastern mediterranean region abstract the iconic climate archive of tenaghi philippon tp ne greece allows the study of short term palaeoclimatic and environmental change throughout the past 1 3 ma to provide high quality age control for detailed palaeoclimate reconstructions based on the tp archive crypto tephra studies of a peat core tp 2005 have been carried out for the 0 130 ka interval the results show that the tp basin is ideally positioned to receive tephra fall from both the italian and aegean arc volcanic provinces two visible tephra layers the santorini cape riva y 2 c 22 ka and the campanian ignimbrite ci y 5 c 39 8 ka tephras and six primary cryptotephra layers namely the early holocene e1 tephra from the aeolian islands c 8 3 ka the campanian y 3 c 29 ka and x 6 tephras c 109 5 ka as well as counterpart tephras tm 18 1d c 40 4 ka tm 23 11 c 92 4 ka and tm 33 1a c 116 7 ka from the lago grande di monticchio sequence southern italy were identified along with repeatedly redeposited y 2 and ci tephra material bayesian modelling of the ages of seven of the primary tephra layers 60 radiocarbon measurements and 20 palynological control points have been applied to markedly improve the chronology of the tp archive this revised chronology constrains the age of tephra tm 18 1d to 40 90 41 66 cal ka bp 95 4 range several tephra layers identified in the tp record form important isochrons for correlating this archive with other terrestrial e g lago grande di monticchio sulmona basin and lake ohrid and marine e g adriatic sea core prad 1 2 and aegean sea core lc21 palaeoclimate records in the mediterranean region

the present day deformation of the central zagros from gps measurements 1 in 1997 and in 2000 we measured the distances between 14 geodetic benchmarks across the central zagros mountain belt the results show that about 10 mm yr of shortening in the central zagros is distributed across the mountain belt this shortening corresponds to roughly 50 of the total convergence between arabia and eurasia and is consistent in direction the persian gulf does not deform significantly the main zagros reverse fault is not an active kinematic boundary the internal deformation of the folded belt is rather homogeneous at the scale of our survey which does not allow us to detect any individual active blind fault however the strain pattern suggests that n s dextral strike slip faults may accommodate part of the deformation

interpretation of nisyros volcanic terrain using land surface parameters generated from the aster global digital elevation model abstract to model the morphotectonic evolution of nisyros stratovolcano in the aegean volcanic arc 36 35 n 27 10 e a 30 m resolution aster gdem was used nisyros is characterized by a relative pristine volcanic terrain elevation slope and aspect images the corresponding frequency distributions and rose diagrams enabled the geomorphometric analysis of nisyros revealing the major geomorphological structures that are associated to both endogenetic and exogenetic processes acting on the island either new or previously reported in the literature new elements include the number loci of issue relative age ogive structures of the voluminous precalderan nikia flows and their contact relationships with the avlaki flows the tectonic control fine feature morphology and flow paths of lavas and smaller domes associated with the main postcalderan domes become visually apparent particularities of the hydrographic network accentuate and bring forward non mapped radial faults intense landslide scarring and the volcanic stratigraphy of the intact units were revealed in the northeastern quadrant of nisyros major new volcano tectonic features include the division of the island into three northwesterly trending sectors and the dipping of nisyros towards the southeast as a result of segmentation by two major ring faults the kos ring fault krf and perigussa ring trapdoor fault prf which represent ring faults of the kos sagging caldera the aster gdem has provided suitable thematic information content in the geomorphometric analysis of nisyros and therefore it offers a reconnaissance tool in the geomorphological analysis of a volcanic landscape

structural styles in the zagros simple folded zone iran arabia eurasia convergence is achieved in the nw zagros by a combination of shortening on nw se trending folds and thrusts mainly in the simple folded zone and by right lateral strike slip on the nw se trending main recent fault a balanced and restored cross section across this part of the range indicates c 49 km of shortening this probably occurred since c 5 ma providing an estimate of the long term shortening rate across the simple folded zone of c 10 mm a 1 the geometries of exposed structures suggest both basement thrusts and thin skinned decollement levels with major folds possibly nucleated above basement faults fold geometries indicate several decollement horizons shale units are candidates as well as evaporites in the neogene mesozoic lower palaeozoic and upper proterozoic successions the se part of the simple folded zone deforms by north south shortening on broadly east west trending folds and thrusts the link between these regions occurs via a set of fault blocks c 400 km wide in total each bounded by north south right lateral faults incremental changes in the strike of some of the folds occur across these right lateral faults with more east west orientations to the east

distribution and chemical composition of tephra layers from eastern mediterranean abyssal sediments abstract most cores of late quaternary sediments from the eastern mediterranean sea contain many ash layers glass shards from discrete layers have been analysed chemically for major elements the layers from different cores have been correlated and unambiguously related to known volcanic events on the basis of the chemical data most of the layers are derived from explosive eruptions of the santorini volcanic complex other layers have their source in other volcanoes of the hellenic arc yali nisyros kos one layer originated from the campanian area italy

tephra correlations and climatic events between the mis6 5 transition and the beginning of mis3 in theopetra cave central greece abstract three cryptotephra layers associated with important periods of climatic change were identified in the middle palaeolithic sequence of theopetra cave greece the lower cryptotephra layer thp tii5 is correlated with the p 11 pantellerian eruption dated to 128 131 ka this cryptotephra postdates a thick sequence of combustion layers that show a complex vegetation succession quite similar to that of the last deglaciation succession in the cave two other cryptotephras thp tii10 and thp tii12 are correlated with the nisyros upper pumice and the pantellerian y6 green tuff dated to 50 ka and 45 7 ka respectively this sequence confirms the position of the nisyros upper tephra below the pantellerian green tuff in the volcanic event stratigraphy of the mediterranean moreover these two upper cryptotephras bracket an extended combustion layer with interstadial vegetation characteristics that may be coincident with the complex greenland interstadial 13 14 on the basis of this new chronology it can be deduced that the intensity of occupation and presence or absence of humans in the cave were closely related to climatic changes in addition a remarkable similarity in the pattern of occupational intensity during the last two deglaciations can be suggested

hydrothermal eruptions of nisyros dodecanese greece past events and present hazard abstract the detailed analysis of the craters of hydrothermal eruptions and related products present on nisyros island demonstrates the ephemerality of these morphological forms in other words the mere recognizable existence of the craters and associated deposits implies recency of hydrothermal activity the minimum temperature required to cause the explosive phenomenon and possibly the depth of the reservoir which can be evaluated on the basis of the correlation between the diameter of the crater and the depth of explosion as proposed by fytikas and marinelli 1976 are therefore closely representative of the current hydrothermal circulation both field evidence and historical records indicate that all the deposits of hydrothermal eruption recognized on nisyros island were emplaced as debris flows almost all the ballistic ejecta were entrained in these debris flows and either redeposited far from their landing sites or involved in later crater collapse and erosion this emplacing mechanism implies that the original products were characterized by a water content higher than about 5 by weight steam driven hydrothermal eruptions one of which took place in 1871 originated deposits of limited dispersion as no sign of these erodible products can be found in the field today surface geology and fluid geochemistry together with subsurface information e g primary and hydrothermal lithologies distribution of temperature with depth physical chemical characteristics of deep water bearing zones indicate that two distinct hydrothermal aquifers are present underneath the southeastern part of the caldera floor both aquifers were probably involved in the most important historically documented hydrothermal eruptions which occurred in 1873 at that time violent earthquakes fractured the brittle aquiclude separating the two aquifers and caused a sudden transfer of fluids from the deep to the shallow aquifer thus triggering the hydrothermal eruptions hydrothermal eruptions will probably occur in future and this hazard must be taken into serious consideration the southern half of lakki plain where all past eruptions took place and active fumaroles are concentrated is the zone at highest risk at present gas geochemistry represents an effective tool to detect changes in the p t conditions of the shallow aquifer and particularly the phenomena of pressure build up that may lead to a hydrothermal eruption

late cenozoic and modern stress fields in the western fars iran implications for the tectonic and kinematic evolution of central zagros 1 the zagros iran developed during mio pliocene times in response to arabia eurasia convergence the western fars highlights a major bend of the deformation front and displays a remarkable set of nearly n s right lateral strike slip faults the kazerun borazjan karebass sabz pushan sarvestan faults oblique at high angle to the belt the region likely plays a major kinematic role by accommodating the change in shortening modes from partitioned in the western central zagros to nonpartitioned in the eastern zagros the inversion of focal mechanisms from small and moderate earthquakes shows a consistent n020 030 compression with a low ratio between differential stresses this regime accounts for the combination of strike slip and thrust type mechanisms through likely 2 3 permutations fault slip analysis reveals two successive late cenozoic regional compressional trends ne sw then n020 the latter is in good agreement with the present day stress the significance of the ne sw compression is discussed alternatively in terms of stress deviations or block rotations in relation to the strike slip fault system fieldwork and satellite imagery suggest that these faults behave first as transfer faults during folding of the cover and later as strike slip faults in agreement with the succession of stress regimes and the evolution of the dominant deformation style from thin skinned to thick skinned the first order stability of the collision related state of stress since 5 ma supports that the arabia eurasia convergence did not give rise to partitioning in the western fars but rather was and is still accommodated by distributed deformation involving both shortening and strike slip motion throughout the cover and the basement

new light on old pumice the origins of mediterranean volcanic material from ancient egypt this paper presents and discusses the neutron activation analysis naa results newly obtained from pumice pieces found decades ago at the egyptian sites of maiyana sedment kahun and amarna now in the collections of the ashmolean museum oxford and the petrie museum of egyptian archaeology london which could be successfully related to several volcanic eruptions in the mediterranean the work contributes to the constant accumulation of knowledge concerning the first appearance of pumice from the so called minoan eruption of the santorini volcano in addition it unexpectedly sheds more light on the long distance trade of mediterranean volcanic material in the bronze age world by disclosing another connection between lipari and the eastern mediterranean

ground deformation of nisyros volcano greece for the period 1995 2002 results from dinsar and dgps observations differential gps dgps and differential inter ferometric synthetic aperture radar dinsar analyses were applied to the kos yali nisyros volcanic field se hellenic volcanic arc to quantify the ground deformation of nisyros volcano after intense seismic activity in 1996 a gps network was installed in june 1997 and re occupied annually up to 2002 a general uplift ranging from 14 to 140 mm was determined at all stations of the network the corresponding horizontal displacements ranged from 13 to 53 mm the displacement vectors indicate that the island is undergoing extension towards the east west and south a two source mogi model combined with assumed mo tion along the mandraki fault was constructed to fit the observed deformation the best fit model assumes sources at a depth of 5500 m nw of the centre of the island and at 6500 m offshore ese of yali island dinsar analysis using four pairs of images taken between may 1995 and september 2000 suggests that deformation was occurring during 1995 before the start of the seismic crisis an ampli tude of at least 56 mm along the slant range appeared for the period 1996 through 1999 this deformation is consistent with the two source model invoked in dgps modelling surface evidence of ground deformation is expressed in the contemporaneous reactivation of the mandraki fault

thick and thin skinned deformation rates in the central zagros simple folded zone iran indicated by displacement of geomorphic surfaces although the geology and structure of the zagros fold and thrust belt iran have been studied extensively the distribution of active deformation across the belt and its seismotectonic behaviour remain controversial we have mapped deformed fluvial terraces along the dalaki and mand rivers in the central zagros as well as marine terraces along the persian gulf in order to unravel the spatial pattern of vertical displacements and to analyse active deformation and its implications for seismicity using appropriate fold models based on structural data allows interpreting such vertical displacements in terms of horizontal shortening across the fold structures obtaining well constrained rates of deformation depends on reliably dating deformed geomorphic markers by combining different dating techniques and correlations to sea level history we propose an internally consistent set of ages which allow the first geomorphic estimates of shortening rates absorbed by individual structures in the central zagros our results show that shortening on late pleistocene timescales is concentrated in the frontal part of the belt consistent with recent gps data three or four frontal structures appear to absorb practically all of the active shortening across the zagros broadly consistent with a normal forward propagating deformation sequence but with local out of sequence activation of structures behind the forward most folds the localization rate and direction of surface shortening across individual structures appear decoupled from basement deformation as indicated by structural cross sections and the distribution of seismicity such independent behaviour suggests that the sedimentary cover of the frontal zagros is decoupled from the basement most probably at the level of the hormuz salt this weak basal detachment level together with several intermediate decollement levels appears to be responsible for the overwhelmingly aseismic deformation of the zagros sedimentary cover and also to control the development of a large panel of fold structures from detachment to fault propagation folds with varying wavelength and rooting depth

correction of in situ cosmogenic nuclide production rates for geomagnetic field intensity variations during the past 800 000 years we present integrated relative production rates for cosmogenic nuclides in rock surfaces which take into account reported variations of the geomagnetic field intensity during the past 800 000 yr the calculations are based on the model simulating cosmic ray particle interactions with the earth s atmosphere given by masarik and beer simulation of particle fluxes and cosmogenic nuclide production in the earth s atmosphere j geophys res 104 d10 12099 12111 1999 corrections are nearly independent on altitude between sea level and at least 5000 m the correction factors are essentially identical for all stable and radioactive cosmogenic nuclides with half lives longer than a few hundred thousand years at the equator integrated production rates for exposure ages between 40 000 to 800 000 yr are 10 to 12 higher than the present day values whereas at latitudes 40 geomagnetic field intensity variations have hardly influenced in situ cosmogenic nuclide production correction factors for in situ 14c production rates differ from those of longer lived nuclides they are always smaller than 2 because the magnetic field intensity remained rather constant during the past 10 kyr when the major fraction of the 14c extant today was produced

volcanogenic mass flow deposits and seafloor diapirism following the largest insular quaternary eruption of the eastern mediterranean at nisyros island aegean volcanic arc abstract nisyros volcanic island at the eastern end of the aegean volcanic arc was mainly constructed after the ultra plinian kos plateau tuff kpt eruption at 161 ka the surrounding submarine area consists mostly of marginal mass transport deposits that commonly characterize insular stratovolcanoes this study aims at providing insights into the deposition and volume of such deposits by elucidating the products of a mega eruption and subsequent paroxysmal volcanicity typical of subduction zone island arc systems seismic reflection and multibeam bathymetry around nisyros identify pyroclastic and debris flow deposits covering areas several orders of magnitude greater than the island the entire seabed between the basins of east kos and tilos is underlain by a 7 km3 volcaniclastic unit that defines a ubiquitous basal unconformity at an average depth of 30 m below the seafloor southwest of nisyros two groups of avalanche deposits from the same unit are bathymetrically identified on the slopes of the northernmost karpathos basin apron seismic stratigraphic markers that trace the unit on the shelf of tilos suggest it is concomitant with the kpt eruption this formerly unknown submarine expansion of the kpt deposits into three neighboring basins when added to the volume of this massive unit to the rest of the nisyros surroundings gives it an explosivity index vei 6 as such it represents the largest quaternary subaqueous volcanogenic mass flow deposit of the eastern mediterranean from this dataset it can be inferred that the submarine advance of the erupted material occurred mainly through erosive gravity flows envisioned as the main dispersion mechanism of large scale subaqueous pyroclastic deposits of plinian eruptions east of nisyros unique small scale diapiric domes and seafloor mounds are attributed to loading by the kpt in combination with regional faulting subsequent nisyros effusive activity produced pyroclastic units around the northeast as well as debris avalanche and lava flows south of the island these have been correlated to known onshore formations the present study documents the intensity and impacts of a volcanic island mega eruption and paroxysmal epilogue over a cycle of 100 kyr

convergence history across zagros iran constraints from collisional and earlier deformation the zagros orogen provides a unique opportunity within the alpine system to evaluate the interplay between a young tertiary collision and earlier subduction obduction processes within the crush zone and the sanandaj sirjan internal zone separating the zagros fold belt from central iran we document several major tectonic events taking place at the end of the cretaceous of the eocene and from the mio pliocene onwards ca 20 15 ma contrary to recent interpretations our data cross sections and description of the overall deformation style strongly suggest that the main zagros thrust mzt is deeply rooted possibly to moho depths and that the suture zone effectively runs along the mzt field observations show that the final resorption of the oceanic domain took place slightly after 35 ma and that collision must have started before ca 23 25 ma in northern zagros the shortening rate across the crush zone since the mid miocene 20 15 ma is estimated at a minimum 3 4 mm year shear movements in the crush zone during the eocene oligocene period and extensional strike slip movements in the internal zones during the late cretaceous point to an oblique setting early in the convergence history a geotectonic scenario for convergence from the time of obduction to the present is finally proposed

late cenozoic partitioning of oblique plate convergence in the zagros fold and thrust belt iran the nw trending zagros fold and thrust belt is affected by two major dextral faults 1 the nw trending main recent fault that accommodates partitioning of oblique convergence at the rear of the western zagros and 2 the north trending kazerun fault located in the central zagros combined structural and fault kinematics studies and spot images analysis have shown a pliocene kinematic change accompanied by a fault pattern reorganization which has led to a modification in the accommodation of oblique convergence since the late pliocene the distributed transpressional deformation operating at the rear of the belt has become partitioned along the newly formed main recent fault this fault cuts through early pliocene nappes and transpressional structures by right laterally reactivating high angle thrusts the southeastern termination of the main recent fault connects to the northern termination of kazerun fault that consists of three fault zones that end in bent orogen parallel splay thrust faults the kazerun fault together with a series of north to nnw trending inherited basement strike slip faults define an orogen scale fan shaped fault pattern pointing toward the main recent fault kazerun fault junction this structural pattern allows slip from along the main recent fault to become distributed by transfer to the longitudinal thrust faults and folds of the zagros belt with the fan shaped fault pattern acting as a horse tail termination of the main recent fault

the early to mid holocene marine tephrostratigraphic record in the nisyros yali kos volcanic center se aegean sea abstract the kos nisyros yali volcanic region is one of the centers in the south aegean volcanic arc to exhibit holocene volcanic activity with poorly dated thin tephra layers on yali associated with neolithic artifacts this paper helps to resolve the age and character of early to mid holocene volcanism in the south aegean sea it presents the lithostratigraphic record of seven newly recovered cores from this region at the se termination of the south aegean volcanic arc the cores were scanned for magnetic susceptibility split logged and sampled at one centimeter resolution for carbonate content selected intervals were analyzed for grain size organic carbon content and feldspar content by xrd in order to identify lithostratigraphic levels with enhanced volcanic minerals subsequently textural and electron microprobe analyses of volcanic glass shards and pumice fragments were carried out on 20 samples chronology was inferred from the upper and lower limits of the s1 sapropel and from five ams 14c dates on foraminifera in several cores in the s1 interval mixed volcanic glass types that compositionally correlate with the nisyros lower and upper pumice yali pumices and kpt suggest that the volcanic glass is reworked from previous deposits and transported by turbidity currents cores from deep water northeast and northwest of yali have a single population of tephra at two or more horizons within s1 that geochemically resembles holocene yali 4 pumice on land these beds likely represent air fall ash that was dispersed at least 10 km from yali with ages of 8 and 10 ka moreover we report two or more tephra layers within s1 from the kalymnos basin that are not reworked and geochemically resemble santorini tephra this study thus confirms the occurrence of small early holocene eruptions at yali and provides possible evidence for early holocene eruptions at santorini

fluvial incision and tectonic uplift across the himalayas of central nepal the pattern of fluvial incision across the himalayas of central nepal is estimated from the distribution of holocene and pleistocene terraces and from the geometry of modern channels along major rivers draining across the range the terraces provide good constraints on incision rates across the himalayan frontal folds sub himalaya or siwaliks hills where rivers are forced to cut down into rising anticlines and have abandoned numerous strath terraces farther north and upstream in the lesser himalaya prominent fill terraces were deposited probably during the late pleistocene and were subsequently incised the amount of bedrock incision beneath the fill deposits is generally small suggesting a slow rate of fluvial incision in the lesser himalaya the terrace record is lost in the high range where the rivers are cutting steep gorges to complement the terrace study fluvial incision was also estimated from the modern channel geometries using an estimate of the shear stress exerted by the flowing water at the bottom of the channel as a proxy for river incision rate this approach allows quantification of the effect of variations in channel slope width and discharge on the incision rate of a river the determination of incision rates requires an additional lithological calibration the two approaches are shown to yield consistent results when applied to the same reach or if incision profiles along nearby parallel reaches are compared in the sub himalaya river incision is rapid with values up to 10 15 mm yr it does not exceed a few millimeters per year in the lesser himalaya and rises abruptly at the front of the high range to reach values of 4 8 mm yr within a 50 km wide zone that coincides with the position of the highest himalayan peaks sediment yield derived from the measurement of suspended load in himalayan rivers suggests that fluvial incision drives hillslope denudation of the landscape at the scale of the whole range the observed pattern of erosion is found to closely mimic uplift as predicted by a mechanical model taking into account erosion and slip along the flat ramp flat geometry of the main himalayan thrust fault the morphology of the range reflects a dynamic equilibrium between present day tectonics and surface processes the sharp relief together with the high uplift rates in the higher himalaya reflects thrusting over the midcrustal ramp rather than the isostatic response to reincision of the tibetan plateau driven by late cenozoic climate change or late miocene reactivation of the main central thrust

explicit treatment of inheritance in dating depositional surfaces using in situ 10be and 26al we describe a new strategy for dating depositional landscape surfaces using in situ produced cosmogenic radionuclides crns that removes the complication of nuclide inheritance by clasts prior to depositon two amalgamated samples each consisting of 30 clasts one from the surface and one from a fixed depth in the subsurface constrain this crn inheritance and date the surface the inheritance may be used to estimate minimum exhumation rates and maximum transport times within the geomorphic system we test the technique using sup 10 be and sup 26 al to date the third fr3 of five terraces along the fremont river utah and the third wr3 of 15 along the wind river wyoming whereas effective ages based solely upon the surface samples yield 118 138 ka fr3 and 93 ka wr3 the subsurface samples reveal that inheritance accounts for 22 wr3 to 43 fr3 of the total crn concentration taking this into account yeilds terrace ages of nearly 61 81 ka for fr3 and nearly 67 76 ka for wr3 we explore the dependence of age estimates on the accumulation history of the terrace silt caps 22 refs 3 figs 1 tab

the upper and lower nisyros pumices revisions to the mediterranean tephrostratigraphic record based on micron beam glass geochemistry abstract the greek island of nisyros is the source of tephra found in distal settings throughout the aegean in this contribution we define geochemical fingerprints for the lower and upper pumice eruptions of nisyros based on micron beam major empa and trace la icp ms element data these two eruptions are compositionally distinct from each other the high phenocryst content of proximal lower and upper pumice tephra means that the differences between the two magmas are masked in whole rock analyses we demonstrate that all previous reports of distal marine and continental tephras correspond to the younger upper pumice not the older lower pumice this has important implications for the marine tephrochronology of the mediterranean and for the age of the upper and lower pumice eruptions we suggest an age of at least 47 ka for the upper pumice and an older unconstrained age for the lower pumice

the structure and kinematics of the southeastern zagros fold thrust belt iran from thin skinned to thick skinned tectonics 1 we present the first complete balanced cross section across the southeastern zagros fold thrust belt zftb the following main structural features emerge from this section 1 in the south of the zftb the proterozoic to recent sedimentary sequence has been decoupled from its panafrican basement along the ductile basal evaporites and folded into a series of large detachment anticlines ongoing shortening of these structures has resulted in migration of the basal salt layers into the cores of the anticlines and propagation of forelimb thrusts 2 in the north of the zftb deep seated ramps have folded the hanging wall rocks and produced imbrications and duplex structures within the higher levels of the sedimentary sequence 3 out of sequence thrusts linked to major seismogenic basement faults have cut through the structures in the cover of the zftb a three step incremental restoration of the section shows that two main phases of deformation can be separated in the tectonic evolution of the zftb a mio pliocene thin skinned phase in the course of which most of the structures in the cover were generated followed by a pliocene to recent thick skinned phase expressed as out of sequence faulting in the cover which is currently underlined by the seismicity within the basement in plan view the initial structures of the southeastern zftb developed with a curved shape essentially controlled by the shape and thickness of the underlying proterozoic salt basin i e the jura style in the following basement involved phase out of sequence thrusts cut at oblique angles through the preexisting structures of the cover the total shortening absorbed in the cover amounts to at least 45 km corresponding to a ratio of 22

comparison of strain and stress tensor orientation application to iran and southern california strain and stress tensors along plate boundaries in iran and southern california are oriented coaxially if they are estimated based on small to moderate earthquakes if large earthquakes m 7 are included in the analysis the estimate of stress directions does not change but the orientation of the released strain rotates significantly thus the direction of the total released strain is different from the stress by about 20 in both iran and southern california and by about 45 in central california we interpret this observation to indicate that the smaller earthquakes occur on faults favorably oriented for failure in the prevailing stress field in which they are possibly generated the larger events rupture near vertical strike slip faults that are unfavorably oriented but weak this weakness causes failure under low ratio of shear to normal stress this view is supported by the fact that in the southern california data set the average angle between the fault planes and the greatest principal stress is about 40 whereas it forms an angle of 70 with the san andreas fault nearly 90 in central california for estimating the seismic strain release by kostrov s method along about a 10 km wide section of the san andreas fault zone we used the data set from which jones determined the stress directions for earthquakes in the range of 2 6 m 4 3 we estimated the directions of principal strain for iran based on 111 focal mechanisms and the scalar moment for earthquakes in the range of 4 4 m 8 we inverted regional subsets of these data for volumes with dimensions of a few hundred kilometers for the stress directions using the method of gephart and forsyth the average misfits for these inversions ranged from 2 to 5 based on test inversions of synthetic data with known misfits we found that these misfits can be attributed solely to inaccuracies of less than 10 in the fault plane solutions therefore the results for iran are most likely obtained for volumes with uniform stress directions we propose that stress inversions with misfits smaller than 6 can be accepted as meaningful as an approximate general guideline because our tests for iran agree with those for hawaiian data sets performed by wyss

earthquakes on the kazerun line in the zagros mountains of iran strike slip faulting within a fold and thrust belt summary the kazerun line is a transverse valley of about 200 km long that obliquely crosses the regular anticlines of the zagros fold belt in sw iran at its northern end it is a clear fault which can be mapped on the surface anticline axes die out or bend towards this valley but do not cross it six moderate sized earthquakes that occurred close the the kazerun line and within a 25 km area involved right lateral strike slip motion parallel to the strike of the valley they indicate that the kazerun line is the surface expression of a buried strike slip fault slip vectors in these strike slip earthquakes are different from those of neighbouring reverse fault earthquakes suggesting that the kazerun line accommodates some of the shortening between arabia and central iran by an elongation of the zagros mountains parallel to strike the centroid depths and the source dimensions of these earthquakes combined with the lack of seismogenic surface faulting in the zagros suggest to us that all these earthquakes involve faulting in the metamorphic basement beneath the sedimentary cover the sedimentary cover is almost certainly decoupled from the basement by several thick evaporite horizons the seismicity of the kazerun line thus demonstrates how lateral interruptions to the regularity of a fold belt can arise from faulting in the basement and not just from lateral ramps between the thrust sheets that deform the sedimentary cover

cosmogenic chlorine 36 from calcium spallation calcium is a major target element for cosmogenic 36cl production consequently 36cl rapidly reaches detectable levels in minerals such as calcite and calcium feldspar exposed at the earth s surface spallation of calcium isotopes typically accounts for 80 90 of 36cl production in these minerals with subsidiary contributions from negative muon capture by 40ca and thermal neutron capture by 35cl to provide a basis for surface exposure dating we have calibrated cosmogenic 36cl production in calcium feldspar from the 17 300 year old tabernacle hill basalt at an altitude of 1445 m and an effective geomagnetic latitude of 40 9 the calcium spallation rate is 152 11 atoms g ca 1 a 1 the corresponding rate at sea level and high latitude is estimated at 48 8 3 4 atoms g ca 1 a 1 the muon capture rate used to derive these values is 8 8 2 2 atoms g ca 1 a 1 at the tabernacle hill site scaled from a value of 4 8 1 2 atoms g ca 1 a 1 at sea level and high latitude the calcium spallation rate determined in this study is in excellent agreement with previous whole rock calibration measurements at tabernacle hill when these are recalculated with respect to the absolute timescale the calibration of 36c1 production from calcium underpins development of an exposure dating technique for calcite due to its high calcium content the 36cl production rate in calcite is higher than in any other common rock forming mineral measurement of 36cl in calcite with an accelerator mass spectrometric detection limit of 5 103 atoms per gram allows dating of limestone surfaces exposed for periods ranging from 102 106 years alternatively erosion rates from less than 1 to greater than 1000 m per year can be determined in the case of eroding karst surfaces though the 36cl production rate is lower in calcium feldspar than in calcite measurements on this mineral will provide a useful means of dating young basalt lavas