the relationships between regional quaternary uplift deformation across active normal faults and historical seismicity in the upper plate of subduction zones the capo d orlando fault ne sicily in order to investigate deformation within the upper plate of the calabrian subduction zone we have mapped and modelled a sequence of late quaternary palaeoshorelines tectonically deformed by the capo d orlando normal fault ne sicily which forms part of the actively deforming calabrian arc in addition to the 1908 messina strait earthquake mw 7 1 this region has experienced damaging earthquakes possibly on the capo d orlando fault however it is not considered by some to be a potential seismogenic source uplifted quaternary palaeoshorelines are preserved on the hangingwall of the capo d orlando fault indicating that hangingwall subsidence is counteracted by regional uplift likely because of deformation associated with subduction collision we attempt to constrain the relationship between regional uplift crustal extensional processes and historical seismicity and we quantify both the normal and regional deformation signals we report uplift variations along the strike of the fault and use a synchronous correlation technique to assign ages to palaeoshorelines facilitating calculation of uplift rates and the fault throw rate uplift rates in the hangingwall increase from 0 4 mm yr in the centre of the fault to 0 89 mm yr beyond its sw fault tip suggesting 0 5 mm yr of fault related subsidence which implies a throw rate of 0 63 0 02 mm yr and significant seismic hazard overall we emphasise that upper plate extension and related vertical motions complicate the process of deriving information on the subduction collision process such as coupling and slip distribution on the subduction interface parameters that are commonly inferred for other subduction zones without considering upper plate deformation

effect of lithospheric thickness on the formation of high and low angle normal faults it is accepted that extension of a homogeneous brittle layer should produce high angle normal faults the rotation of the upper parts of such a fault to a low dip requires fault offset that is greater than the local lithospheric thickness new model calculations indicate that a fault cutting lithosphere thicker than 10 20 km can build up only a few kilometres horizontal throw before a new fault replaces it such a small offset leaves the fault little rotated from its initial high dip angle for thinner lithosphere the fault offset may be much larger leading to rotation of the upper inactive parts of a high angle fault to a low dip angle in continents this can happen where thin upper crustal lithosphere is decoupled from mantle lithosphere by weak lower crust the calculations suggest that normal faults begin with high dip angles and only in areas of very thin lithosphere can they be offset enough to produce low angle fault structures this prediction is consistent with the occurrence of low angle faults in areas with higher than normal heat flow

microearthquakes beneath median valley of mid atlantic ridge near 23 n tomography and tectonics data from a microearthquake experiment in the median valley of the mid atlantic ridge near 23 n in 1982 are used to measure earthquake source parameters to determine the laterally heterogeneous seismic velocity structure across the inner floor and to develop a kinematic tectonic model for this portion of the median valley fifty three microearthquakes occurred over a 10 day period beneath the median valley inner floor and eastern rift mountains twenty of 23 well located inner floor epicenters define a line of activity about 17 km long having a strike of n25 e and located near an along axis depression some 300 400 m deeper than surrounding regions earthquakes with well resolved hypocenters generally have focal depths of 4 8 km beneath the seafloor of both the inner floor and the rift mountains the hypocentral locations are robust with respect to plausible lateral variations in seismic velocity structure composite fault plane solutions for inner floor events indicate normal faulting on planes dipping at angles near 45 normal faulting mechanisms although poorly constrained are also indicated for the rift mountain microearthquakes seismic moments approximate fault dimensions and average stress drops for the largest events recorded are 1019 1020 dyn cm 200 400 m and 1 70 bars respectively a twodimensional tomographic inversion of p wave travel time residuals from microearthquakes and local shots indicates a well resolved lateral heterogeneity in crustal velocity structure across the median valley inner floor p wave velocities at 1 5 km depth within a zone less than 10 km wide beneath the central inner floor are lower by several percent than in surrounding regions the most likely explanation for the low velocities is that the region is the site of the most recent local magmatic injection and remains pervasively fractured as a result of rapid hydrothermal quenching of the newly emplaced crustal column by this view the seismic velocity structure at the ridge axis evolves probably by the sealing of cracks and pores within the first few hundred thousand years of crustal accretion consideration of the detailed sea beam bathymetry in this region of the inner floor the characteristics of large earthquakes that the region has experienced during the past 25 years and the results of the microearthquake and tomography analysis suggests that this section of the median valley has been undergoing continued horizontal extension and block faulting without significant crustal injection of magma for at least the past 104 years

worldwide initiation of holocene marine deltas by deceleration of sea level rise radiocarbon dated deltaic sequences of holocene age from different parts of the world began to accumulate within a restricted time range from about 8500 to 6500 years ago evaluation of major delta processes indicates that deceleration in sea level rise was the key factor in holocene delta formation within many deltas there is as much as a 2000 year age range between basal deposits in seaward and landward cores this age difference records the progressive landward migration of near mean sea level depositional environments during the lower to mid holocene establishment of a chronostratigraphic framework for holocene delta development provides a fundamental global baseline for distinguishing sea level change from vertical land motion by tectonism and isostasy and for evaluating rates of future marine incursion into low lying deltas

slow spreading ridge axis tectonics evidence from the lizard complex uk abstract the east coast section of the lizard ophiolite complex cornwall u k preserves a series of interrelated extensional faults and dyke sets which indicate that the formation of this section of obducted oceanic lithosphere resulted from a combination of contemporaneous structural and magmatic events three dolerite dyke sets are evident the first two sets 1 and 2 are cut by and rotated on a series of ridge parallel extensional faults and shear zones later dykes set 3 cross cut the extensional faults these data indicate that both rotation and significant thinning in the region of 40 of this part of the oceanic lithosphere occurred prior to the final period of dyke injection the thinning of the lithosphere was the result of extension along the normal faults all of the dolerite dykes show morb characteristics although the late dykes set 3 are more primitive tending to be aphyric to sparse olivine phyric and show higher cr ni and lower zr values than the typically plagioclase phyric dolerite dykes sets 1 and 2 intruded prior to the ductile shearing event the more primitive dolerites post date the tectonism and indicate the lack of a significant magma chamber following a period of amagmatic extension the data are consistent with observations at present day slow spreading ridge axes and some mafic ultramafic ophiolite sequences and provide insight into the nature of ridge related structures and the interrelationships between tectonism and geochemical evolution of the dykes and record a mechanism listric faulting to account for the presence of peridotites and gabbros commonly dredged at slow spreading centres

geo archaeological evidence for a holocene extreme flooding event within the arabian sea ras al hadd oman abstract the arabian sea is regarded as one of the least studied regions in terms of coastal hazards such as tropical cyclones and tsunamis parts of the coastline are developing rapidly especially in oman this calls for a proper understanding of the natural processes that act on and affect it this can be done by investigating the magnitude and impact of past events in particular on human settlements by doing this future risks may not only be scientifically predicted and evaluated but the damage caused by future events might even be mitigated evidence of past extreme wave events is preserved in the onshore stratigraphic record in addition to this the coastal zone of oman is rich in archaeological remains presented here are the results of comprehensive mapping and analysis of extreme wave deposits of an archaeological site near ras al hadd suggesting that the early bronze age site hd 6 was inundated at 4450 cal bp an event layer is identified between two settlement phases within the archaeological excavation a contemporaneous sand bed with a maximum thickness of 0 4 m was mapped in the vicinity of the settlement ground penetrating radar surveys allow measurement of the thickness as well as identification of the internal facies architecture of the deposit a high resolution digital elevation model reveals the coastal geomorphology it is concluded that the causative event must have been a tsunami that was most likely generated within the makran subduction zone this interpretation does however remain tentative at the moment archaeological evidence indicates that the site was immediately re occupied after the event which attests to a certain resiliences of the early bronze age coastal communities in the region

mechanisms of lithospheric extension at mid ocean ridges summary we examine the extensional deformation of oceanic plates at mid ocean ridges especially within an axial yield zone where pervasive faulting occurs thermal models of ridges are developed which include the effects of lithospheric thickening on the mantle flow the heat of magmatic crustal accretion at the ridge axis and the hydrothermal cooling due to seawater circulation in the crust when hydrothermal circulation occurs the brittle lithospheric plate at slow spreading ridges could be as thick as 8 9 km thicker than the crust while the plate at fast spreading ridges is only 1 2 km for a typical slow spreading ridge several kilometres of plate thickening are expected within a distance of 15 km from the ridge axis when subjected to the extensional force due to horizontal stretching shear failure by normal faulting will occur pervasively in an axial zone where the lithospheric plate is the thinnest adopting perfectly plastic rheology as a continuum description of deformation on the distributed faults we obtain approximate solutions for the stress distribution in the yield zone within this yield zone sea floor topography increases significantly away from the ridge axis so that the resuiting gravity sliding force balances the differential horizontal extensional force due to the thickening of the lithospheric plate basal stresses induced by the viscously deforming asthenosphere could significantly influence the stresses inside the lithospheric plate only if the mantle viscosity beneath the ridge is on the order of 10 pa s significantly higher than generally accepted values of 10 pa s model calculations reveal that although the seafloor topography at the mid atlantic ridge at 13 15 on is regionally compensated it is locally supported by stresses in the lithospheric plate the deviation of the lithospheric plate from its thermal isostatic equilibrium position can be explained by necking due to plastic stretching in the axial yield zone and elastic deflection of strong plates outside the yield zone the best fit models require the yield zones to have a half width of 10 15 km we find systematic variations in the gravity and topography of the east pacific rise which indicate strong influence of plate spreading rate on the ridge thermal and mechanical structure at the 16 17 on area where the half spreading rate is 4 3 cm yr a prominent axial topographic high and an axial mantle bouguer gravity low exist implying a crustal or sub crustal low density body the gravity low disappears at the 20 21 n area where the half spreading rate is 3 6 cm yr as the plate spreading rate decreases from 4 3 cm yr at the 16 17 on area to 2 7 cm yr at the 22 23 on area axial ridge topography changes from higher than the thermal isostatic equilibrium position to lower than the isostatic position the low axial topography at the 22 23 n area can be explained by the existence of a low amplitude median valley

toward mapping surface deformation in three dimensions using insar 1 one of the limitations of deformation measurements made with interferometric synthetic aperture radar insar is that an interferogram only measures one component of the surface deformation in the satellite s line of sight we investigate strategies for mapping surface deformation in three dimensions by using multiple interferograms with different imaging geometries geometries for both current and future missions are evaluated and their abilities to resolve the displacement vector are compared the north component is always the most difficult to determine using data from near polar orbiting satellites however a satellite with an inclination of about 60 120 would enable all three components to be well resolved we attempt to resolve the 3d displacements for the 23 october 2002 nenana mountain alaska earthquake the north component s error is much larger than the signal but proxies for eastward and vertical motion can be determined if the north component is assumed negligible inversions of hypothetical coseismic interferograms demonstrate that earthquake model parameters can be well recovered from two interferograms acquired on ascending and descending tracks

isostatic uplift driven by karstification and sea level oscillation modeling landscape evolution in north florida isostatic uplift of tectonically stable passive margin lithosphere can preserve a record of paleo shoreline position by elevating coastal geomorphic features above the influence of nearshore wave activity conversely depositional ages and modern elevations of these features can provide valuable information about the uplift history of a region we present a numerical model that combines sea level oscillation subaerial exposure a precipitation karstification function and isostatic uplift to explore the dynamic geomorphic behavior of coastal carbonate landscapes over multiple sea level cycles the model is used to estimate ages of coastal highstand depositional features along the atlantic coast of north florida numerical simulations using current best estimates for pleistocene sea level and precipitation histories suggest ages for trail ridge 1 44 ma the penholoway terrace 408 ka and the talbot terrace 120 ka that are in agreement with fossil evidence in addition model results indicate that the rate of karstification void space creation or equivalent surface lowering rate within the north florida platform is 3 5 times that of previous estimates 1 m 11 2 k y vs 1 m 38 k y and uplift rate is 2 times as high as previously thought 0 047 mm yr vs 0 024 mm yr this process has implications for landscape evolution in other carbonate settings and may play an underappreciated role within the global carbon cycle

three dimensional gravity and bathymetry analysis of the mid atlantic ridge between 20 n and 24 n flow geometry and temporal evolution of the segmentation bathymetry and gravity data covering 10 m y on both flanks of the mid atlantic ridge south of the kane fracture zone reveal a complex segmentation pattern well correlated with short scale temporal variations in crustal production segment and paleosegment centers are associated with crustal thickening while their extremities appear as elongated bands of thin crust subsidence rates vary between centers and extremities of a segment with higher than world average values at segmert midpoints and closer to average values at the edges this is consistent with segment centers being the site of focused mantle upwellings with associated thin lithosphere and with thick crust a pronounced circular minimum in the long wavelength of the mantle bouguer anomaly associated to a maximum in the long wavelength of the bathymetry marks the site of a mantle upwelling associated with a particularly robust segment located north of a small fracture zone 21 20 n an offset is often observed between extreme values of topography and crustal thickness resulting in a lack of isostatic equilibrium for off axis short wavelength features an obliquity between maxima of crustal thickening associated with active segments and the topographic axial domain suggests that the shift between topography and crustal structure may arise partly from a decoupling between crust and topography formation processes

continuous exhumation of mantle derived rocks at the southwest indian ridge for 11 million years the global mid ocean ridge system where tectonic plates diverge is traditionally thought of as the largest single volcanic feature on the earth yet wide expanses of smooth sea floor in the easternmost part of the southwest indian ridge in the indian ocean lacks the hummocky morphology that is typical for submarine volcanism at other slow spreading ridges the sea floor can extend by faulting the existing lithosphere along only one side of the ridge axis however the smooth sea floor in the easternmost southwest indian ridge also lacks the corrugated texture created by such faulting instead the sea floor is smooth on both sides of the ridge axis and is thought to be composed of altered mantle derived rocks here we use side scan sonar to image the sea floor and dredge samples to analyse the composition of two sections of the southwest indian ridge between 62 050 e and 64 400 e where the sea floor formed over the past 11 million years we show that the smooth floor is almost entirely composed of seawater altered mantle derived rocks that were brought to the surface by large detachment faults on both sides of the ridge axis faulting accommodates almost 100 of plate divergence and the detachment faults have repeatedly flipped polarity we suggest that this tectonic process could also explain the exhumation of mantle derived rocks at the magma poor margins of rifted continents

the implications of revised quaternary palaeoshoreline chronologies for the rates of active extension and uplift in the upper plate of subduction zones we demonstrate a synchronous correlation technique to determine the chronology of quaternary palaeoshorelines to test proposed relationships between tectonics climate and sea level change the elevations of marine palaeoshorelines in calabria around the active vibo normal fault have been measured from tin dem 10 m data and fieldwork and correlated with global sea level curves a synchronous correlation method and new u th dates are used to ascertain how the slip rate on the fault relates to uplift rates across the region regional uplift possibly associated with subduction along the calabrian trench or due to the cumulative effect of closely spaced active normal faults is rapid enough to uplift even the hangingwall of the vibo normal fault the actual value for the rate of background uplift can only be ascertained once the rate of slip on the vibo fault is subtracted synchronous correlation of multiple palaeoshorelines sampled along 29 elevation profiles with global sea levels shows that the resultant uplift rate background uplift minus local hangingwall subsidence is constant through time from 0 to 340 ka and not fluctuating by a factor of 4 as previously suggested the uplift rate increases from 0 4 mm yr at the centre of the hangingwall of the fault to 1 75 mm yr in the hangingwall in the vicinity of the fault tip palaeoshorelines can be traced from the hangingwall to the footwall around the fault tip and hence correlated across the fault the throw rate on the fault averaged over 340 ka decreases from a maximum at the centre of the fault 1 mm yr to zero at the tip this gradient in throw rate explains the spatial variation in resultant uplift rates along the fault we interpret the 1 75 mm yr resultant uplift rate at and beyond the fault tip as the signature of a regional uplift presumably related to subduction although we cannot exclude the possibility that other local faults influence this uplift the lower uplift rates in the hangingwall of the fault are due to interaction between regional uplift and subsidence associated with the local active normal faulting we discuss a how our synchronous correlation technique should trigger a re appraisal of palaeoshoreline chronologies worldwide and b the implications for the tectonics and seismic hazard of calabria suggesting that perturbations in the uplift rate field are a key criterion to map the locations of active faults their deformation rates and hence seismic hazard above subduction zones

space geodetic constraints on glacial isostatic adjustment in fennoscandia analysis of global positioning system gps data demonstrates that ongoing three dimensional crustal deformation in fennoscandia is dominated by glacial isostatic adjustment our comparison of these gps observations with numerical predictions yields an earth model that satis es independent geologic constraints and bounds both the average viscosity in the upper mantle 5 x 10 20 to 1 x 10 21 pascal seconds and the elastic thickness of the lithosphere 90 to 170 kilometers we combined gps derived radial motions with fennoscandian tide gauge records to estimate a regional sea surface rise of 2 1 0 3 mm year furthermore ongoing horizontal tectonic motions greater than 1 mm year are ruled out on the basis of the gps derived three dimensional crustal velocity field

late quaternary deformation of marine terraces on the cascadia subduction zone near cape blanco oregon the cape blanco region of south coastal oregon sits on the upper plate of the cascadia subduction zone about 60 70 km east of the base of the continental slope though the region has no historic coseismic deformation late quaternary deposits and landforms show abundant evidence of uplift folding and faulting a set of five late quaternary marine terraces and one uplifted holocene beach berm are preserved in the cape blanco region stratigraphic and altitudinal surveys of these physiographic features combined with several numerical and correlation age determinations permit a reconstruction of tectonic deformation near cape blanco in approximately the last 200 000 years the most cogent aspects of the neotectonics in this part of the cascadia subduction zone are that an east west trending anticline deforms the lower three terraces 80 125 ka as well as accounting for uplift of the holocene storm berm latest movement on the anticline was no more than 2 000 years ago but the anticline also deforms sediments as old as middle miocene the anticline is consistent with a north south principal contraction axis at cape blanco in about the last 100 000 years an older terrace at cape blanco approximately 200 ka is offset by two reactivated faults whose movements prior to the eocene served to suture several terranes to the north american continent tectonic tilting in the older terrace is not consistent with a north south principle axis of contraction but the axis of tilt is parallel to north northwest striking structures developed in the quaternary fold belt offshore on the continental shelf the observed deformation indicates that regional stress in the vicinity of cape blanco in the late quaternary has been accommodated by a variable pattern of strain

drainage systems and the development of normal faults an example from pleasant valley nevada abstract drainage systems in regions of active extension contain information about fault zone structure and development and particularly about the lateral growth of individual fault segments that is difficult to obtain by more conventional means such as the dating of sedimentary material we investigate drainage fault interaction in pleasant valley nevada where a large normal faulting earthquake occurred in 1915 we find geomorphological evidence for a propagation increase in length of several km at both ends of one of the 1915 fault segments at one end we estimate the propagation rate to be about 50 m per earthquake this estimate is uncertain but is within the range predicted by theoretical models of fault growth drainage along the axes of half graben in this region may be influenced by the spacing of tilted fault blocks the highest valleys are also the narrowest whether the axial streams succeed in reaching lower neighbouring sinks depends on whether sedimentation rates are able to keep basins filled to the levels of the basement highs that separate half graben of opposite polarity a knowledge of modern drainage fault interactions may help predict drainage systems and the position of potential syn rift reservoir sediments in older extensional terrains where fault configurations but not facies distributions are known from seismic reflection surveys

dyke complex of the east pacific rise exposed in the walls of hess deep and the structure of the upper oceanic crust abstract detailed observations have been made of the extrusive and intrusive units of the uppermost crust emplaced at the axis of the east pacific rise during dives conducted with the submersible nautile on the walls of hess deep at four widely separated locations the same sequence was found an upper thin 100 200 m unit of extrusives pillow lavas underlain by a mixed zone of variable thickness 50 500 m averaging 200 m where extrusives are found and intrusives and massive subhorizontal layers which may represent sills the mixed zone itself is underlain by a sheeted dyke unit that may be up to 1200 m thick where dykes are subvertical i e untilted and parallel to the east pacific rise fabric this sequence may be a general feature of medium to fast spreading crust because it is similar to that observed in hole 504b of the costa rica rift and is consistent with images of the upper oceanic crust derived from seismic experiments on the axis of the east pacific rise dyke thickness is a good measure of the depth to the roof of the axial magma chamber the observed sections provide much needed ground truth for east pacific rise crust the thickness of the lava sequence and the overall thickness of layer 2 at most 1400 m appear to have been overestimated in previous studies of the oceanic crust

differential uplift along the northern margin of the central anatolian plateau inferences from marine terraces abstract emerged marine terraces and paleoshorelines along plate margins are prominent geomorphic markers that can be used to quantify the rates and patterns of crustal deformation the northern margin of the central anatolian plateau has been interpreted as an actively deforming orogenic wedge between the north anatolian fault and the black sea here we use uplifted marine terraces across principal faults on the sinop peninsula at the central northern side of the pontide orogenic wedge to unravel patterns of quaternary faulting and orogenic wedge behavior we leveled the present day elevations of paleoshorelines and dated marine terrace deposits using optically stimulated luminescence osl to determine coastal uplift the elevations of the paleoshorelines vary between 4 0 2 and 67 1 4 m above sea level and osl ages suggest terrace formation episodes during interglacial periods at ca 125 190 400 and 570 ka corresponding to marine isotopic stages mis 5e 7a 11 and 15 mean apparent vertical displacement rates without eustatic correction deduced from these terraces range between 0 02 and 0 18 mm a with intermittent faster rates of up to 0 26 mm a we obtained higher rates at the eastern and southern parts of the peninsula toward the hinterland indicating non uniform uplift across the different morphotectonic segments of the peninsula our data are consistent with active on and offshore faulting across the sinop peninsula when integrated with regional tectonic observations the faulting pattern reflects shortening distributed over a broad region of the northern margin of the central anatolian plateau during the quaternary

unraveling sea level variations and tectonic uplift in wave built marine terraces santa maria island chile abstract the architecture of coastal sequences in tectonically active regions results mostly from a combination of sea level and land level changes the objective of this study is to unravel these signals by combining sequence stratigraphy and sedimentology of near shore sedimentary sequences in wave built terraces we focus on santa maria island at the south central chile margin which hosts excellent exposures of coastal sediments from marine isotope stage 3 a novel method based on statistical analysis of grain size distributions coupled with facies descriptions provided a detailed account of transgressive regressive cycles radiocarbon ages from paleosols constrain the chronology between 53 and 31 cal ka bp because the influence of glaciations can be neglected we calculated relative sea level curves by tying the onset of deposition on a bedrock abrasion platform to a global sea level curve the observed depositional cycles match those predicted for uplift rates between 1 2 and 1 8 m ka the studied sedimentary units represent depositional cycles that resulted in reoccupation events of an existing marine terrace our study demonstrates wave built marine terrace deposits along clastic shorelines in temperate regions can be used to distinguish between tectonic uplift and climate induced sea level changes

lower cretaceous strata of the sonora bisbee basin a record of the tectonomagmatic evolution of northwestern mexico lower cretaceous strata of the sonora bisbee basin record four discrete paleozoic and mesozoic magmatic episodes and indicate a previously unrecognized early cretaceous regional tectonic event along the southwestern margin of north america strata of the bisbee group in the sonora bisbee basin overlie upper jurassic strata on an angular unconformity cretaceous strata are predominantly continental fluvial deposits bisbee group sandstones are sublitharenites and litharenites rich in paleovolcanic lithic fragments detrital zircon age populations form five main groups proterozoic early permian early triassic late triassic jurassic earliest cretaceous and late early cretaceous aptian u pb zircon ages from three types of conglomerate clasts in the morita formation match these age groups 1 quartzite clasts are dominated by proterozoic ages 2 rhyolite clasts are middle jurassic ca 172 ma 3 andesite clasts are earliest cretaceous ca 140 ma proterozoic zircons and quartzite clasts were recycled from strata of the caborca block whereas permian and mesozoic grains and andesite and rhyolite clasts were derived from volcanic arc rocks to the west and northwest we identify two separate episodes of early cretaceous volcanism recorded in the basin the first between 145 and 133 ma and the second beginning ca 125 ma and continuing into the albian the presence in the sonora bisbee basin of near source fluvial detritus from the first of these episodes requires either the presence of a continental arc along the north american margin during the earliest cretaceous or the accretion of similar aged material to the margin prior to ca 130 ma neovolcanic zircon grains in the upper part of the morita formation record the initiation of volcanism in the alisitos arc an early cretaceous volcanic arc presently exposed in the peninsular ranges of baja and southern california structural stratigraphic and detrital zircon data suggest that a heretofore unrecognized episode of regional shortening uplift and incision occurred to the southwest of the study area in the interval 148 130 ma

a note of caution on the use of boulders for exposure dating of depositional surfaces abstract exposure dating of boulders has been widely applied to determine the age of depositional surfaces under the assumption that the pre depositional nuclide component in most boulders is negligible here we present a case study on fluvial terraces at the active mountain front of the eastern andes where this assumption is clearly invalid because sandstone boulders n 13 from terraces at two sites contain a highly variable inherited 10be component and have apparent 10be ages that exceed the age of the respective surface by up to 90 ka likewise boulders from active stream channels n 5 contain a substantial inherited 10be component equivalent to 5 48 ka of exposure the age of the fluvial terraces is well determined by two approaches that allow to correct for the pre depositional nuclide component 10be dating of amalgamated pebbles and 10be depth profiles on sand samples at site 1 three terraces have 10be ages of 3 5 ka t2 11 13 ka t3 and 16 20 ka t4 which are consistent with the terrace stratigraphy the age of terrace t3 is confirmed by a calibrated 14 c age of 12 61 0 20 ka bp obtained from a wood sample at site 2 terrace t3 has a 10be age of 13 16 ka the average inherited 10be concentration of sand grains determined from depth profiles and stream sediments is small and equivalent to 1 3 ka of exposure in contrast the mean inheritance of pebbles and boulders is higher and equivalent to exposure times of 10 ka and 30 ka respectively these differences in the pre depositional nuclide component are related to the different provenance and transport history of sand pebbles and boulders the sand is derived from rapidly eroding miocene sediments exposed near the mountain front whereas the pebbles and boulders originate from triassic sandstones in the internal part of the fold and thrust belt on their way to the mountain front boulders and pebbles were temporarily stored and irradiated in alluvial fans that are currently reworked as sediment deposition in intramontane basins and their subsequent excavation is common in the andes and other fold and thrust belts the presence of pre depositional nuclide components should be evaluated when applying exposure dating at active mountain fronts

active simultaneous uplift and margin normal extension in a forearc high crete greece abstract the island of crete occupies a forearc high in the central hellenic subduction zone and is characterized by sustained exhumation surface uplift and extension the processes governing orogenesis and topographic development here remain poorly understood dramatic topographic relief 2 6 km astride the southern coastline of crete is associated with large margin parallel faults responsible for deep bathymetric depressions known as the hellenic troughs these structures have been interpreted as both active and inactive with either contractional strike slip or extensional movement histories distinguishing between these different structural styles and kinematic histories here allows us to explore more general models for improving our global understanding of the tectonic and geodynamic processes of syn convergent extension we present new observations from the south central coastline of crete that clarifies the role of these faults in the late cenozoic evolution of the central hellenic margin and the processes controlling quaternary surface uplift pleistocene marine terraces are used in conjunction with optically stimulated luminesce dating and correlation to the quaternary eustatic curve to document coastal uplift and identify active faults two south dipping normal faults are observed which extend offshore offset these marine terrace deposits and indicate active n s margin normal extension further marine terraces preserved in the footwall and hanging wall of both faults demonstrate that regional net uplift of crete is occurring despite active extension field mapping and geometric reconstructions of an active onshore normal fault reveal that the subaqueous range front fault of south central crete is synthetic to the south dipping normal faults on shore these findings are inconsistent with models of active horizontal shortening in the upper crust of the hellenic forearc rather they are consistent with topographic growth of the forearc in a viscous orogenic wedge where crustal thickening and uplift are a result of basal underplating of material that is accompanied by extension in the upper portions of the wedge within this framework a new conceptual model is presented for the late cenozoic vertical tectonics of the hellenic forearc

factors controlling normal fault offset in an ideal brittle layer we study the physical processes controlling the development and evolution of normal faults by analyzing numerical experiments of extension of an ideal two dimensional elastic plastic brittle layer floating on an inviscid fluid the yield stress of the layer is the sum of the layer cohesion and its frictional stress faults are initiated by a small plastic flaw in the layer we get finite fault offset when we make fault cohesion decrease with strain even in this highly idealized system we vary six physical parameters the initial cohesion of the layer the thickness of the layer the rate of cohesion reduction with plastic strain the friction coefficient the flaw size and the fault width we obtain two main types of faulting behavior 1 multiple major faults with small offset and 2 single major fault that can develop very large offset we show that only two parameters control these different types of faulting patterns 1 the brittle layer thickness for a given cohesion and 2 the rate of cohesion reduction with strain for a large brittle layer thickness 22 km with 44 mpa of cohesion extension always leads to multiple faults distributed over the width of the layer for a smaller brittle layer thickness the fault pattern is dependent on the rate of fault weakening a very slow rate of weakening leads to a very large offset fault and a fast rate of weakening leads to an asymmetric graben and eventually to a very large offset fault when the offset is very large the model produces major features of the pattern of topography and faulting seen in some metamorphic core complexes

tertiary quaternary faulting and uplift in the northern oman hajar mountains field mapping and remote sensing investigations reveal two new major fault sets cutting through tertiary rocks quaternary terraces and a several hundred year old irrigation canal system in the hajar mountains of northern oman they extend for tens of kilometres forming fracture intensification zones several hundred metres wide wnw to nw oriented faults run parallel to the mountain fronts in the plains adjoining the central hajar range then obliquely crosscut the mountains in the north motion along these faults explains how quaternary marine terraces became elevated 190 m above sea level a second fault set strikes north to nne the associated juvenile topography suggests that they also accommodate recent uplift subsidiary to the wnw striking faults with minor strike slip and differential movement between various segments of the hajar mountains both fault systems and the amount of quaternary uplift between 100 and 500 m are similar to those in other active and ancient forebulge environments using the fracture patterns observed it is proposed here that the hajar range lies on the active forebulge of a collision zone between the ne margins of the arabian plate the zagros fold belt and the makran accretionary prism which resulted in the recent uplift

multiple dating approach 14c 230th u and 36cl of tsunami transported reef top boulders on bonaire leeward antilles current achievements and challenges abstract dating the transport deposition time of supratidal coarse clast deposits is difficult limiting their value for inferring frequency magnitude patterns of high energy wave events on bonaire leeward antilles caribbean these deposits form prominent landforms and transport by one or several holocene tsunamis is assumed at least for the largest clasts although a large dataset of 14c and electron spin resonance esr ages is available for major coral rubble ridges and ramparts it is still debated whether these data reflect the timing of major events and how these datasets are biased by the reworking of coral fragments as an attempt to overcome the current challenges for dating the dislocation of singular boulders three distinct dating methods are implemented and compared i 14c dating of boring bivalves attached to the boulders ii 230th u dating of post depositional secondary calcite flowstone and subaerial microbialites at the underside of the boulders and iii surface exposure dating of overturned boulders via 36cl concentration measurements in corals approaches ii and iii have never been applied to coastal boulder deposits so far the three 14c age estimates are older than 40 ka i e most probably beyond the applicability of the method which is attributed to post depositional diagenetic processes shedding doubt on the usefulness of this method in the local context the remarkably convergent 230th u ages all pointing to the late holocene period 1 0 1 6 ka are minimum ages for the transport event s the microbialite sample yields an age of 1 23 0 23 ka and both flowstone samples are in stratigraphic order the older onset of carbonate precipitation and younger flowstone layers yield ages of 1 59 0 03 and 1 23 0 03 ka respectively four coral samples collected from the topside of overturned boulders yielded similar 36cl concentration measurements however the computed ages are affected by large uncertainties mostly due to the high natural chlorine concentration after correction for the inherited component and chemical denudation since platform emergence inducing additional uncertainty the calculated 36cl ages cluster between 2 5 1 3 and 3 0 1 4 ka for three of four boulders whilst the fourth one yields an age of 6 1 1 8 ka probably related to a higher inheritance these 230th u and 36cl age estimates are coherent with a suggested tsunami age of

styles and rates of long term denudation in carbonate terrains under a mediterranean to hyper arid climatic gradient abstract carbonate minerals unlike silicates have the potential to dissolve almost completely and with high efficiency thus in carbonate terrains denudation rate and style the governing process of denudation mechanical or chemical should be more sensitive to climatic forcing using 36 cl measurements in 39 carbonate bedrock and sediment samples we calculate long term denudation rates across a sharp climatic gradient from mediterranean to hyper arid conditions our samples were collected along the arugot watershed which drains the eastern flank of the judea range central israel to the dead sea and is characterized by a pronounced rain shadow denudation rates of flat lying bedrock outcrops sampled along interfluves differ by an order of magnitude from 20 mm ka 1 in the mediterranean zone to 1 3 mm ka 1 in the hyper arid zone these rates are strongly correlated with precipitation and thus reflect the importance of carbonate mineral dissolution in the overall denudation process in contrast denudation rates of steep bedrock surfaces depend on the hillslope gradient but only in the hyper arid climate zone indicating that mechanical processes dominate the overall hillslope denudation within this zone the dominance of slope dependent mechanical erosion in the hyper arid zone is also reflected by an increase in spatially average denudation rates from 17 19 mm ka 1 in the mediterranean semi arid zones to 21 25 mm ka 1 in the hyper arid zone these higher rates are attributed to clast contribution from steep slopes under arid climate this suggests an increased importance of mechanical processes to the overall denudation in the hyper arid zone we demonstrate that the transition between chemically dominated denudation to mechanically dominated denudation occurs between 100 and 200 mm of mean annual precipitation long term denudation rates across the judea range indicate that between mediterranean and hyper arid climates chemical weathering rates are limited by precipitation nevertheless in more humid climates chemical weathering rates are apparently limited by the rates of carbonate mineral dissolution this study demonstrates that carbonate terrains have the capacity to shift between mechanically and chemically dominated denudation in response to changes in precipitation similar transitions in response to changes in temperature or the level of tectonic activity have been previously reported we suggest that the abrupt nature of such transitions can be primarily attributed to the efficiency of carbonate dissolution processes and the competition between surface and subsurface drainage systems in carbonate terrains

water load definition in the glacio hydro isostatic sea level equation abstract models of glacio hydro isostatic rebound and the concomitant sea level change have been progressively improved over the past three decades recently the procedures used by the group at the australian national university anu for the hydro isostatic component of the theory have been questioned quat sci rev 21 2002 409 although the details of the anu group s procedures have not been published because they are mainly computational in nature rather than representing significant conceptual advances because of this criticism we set out here in detail the procedures that have been used for the treatment of the migration of shorelines as sea levels rise and fall the effect of retreat and advancing grounded ice on shelves and shallow seas and the transitions from grounded to floating ice and vice versa we conclude that there is no basis for the criticism that these formulations and their implementation provide a high resolution and complete description of both sea level change and of the estimates of volumes of ice exchanged with the oceans the results from this formulation are confirmed by the entirely independent analyses of milne et al quat sci rev 21 2002 361 and mitrovica and milne geophys j int 2002 submitted for publication who conclude that our formulation is significantly more accurate than the procedure advocated by peltier science 265 1994 195 rev geophys 36 1998a 603 geophys res lett 25 1998b 3955

age estimates and uplift rates for late pleistocene marine terraces southern oregon portion of the cascadia forearc marine terraces are prominent landforms along the southern oregon coast which forms part of the forearc region of the cascadia subduction zone interest in the cascadia subduction zone has increased because recent investigations have suggested that slip along plates at certain types of convergent margins is characteristically accompanied by large earthquakes in addition other investigations have suggested that convergent margins can be broadly classified by the magnitude of their uplift rates with these hypotheses in mind we generated new uranium series amino acid and stable isotope data for southern oregon marine terrace fossils these data along with terrace elevations and two alternative estimates of sea level at the time of terrace formation allow us to determine terrace ages and uplift rates uranium series analysis of fossil coral yields an age of 83 5 ka for the whisky run terrace at coquille point in bandon oregon a combination of amino acid and oxygen isotope data suggest ages of about 80 and 105 ka for the lowest two terraces at cape blanco these ages indicate uplift rates of 0 45 1 05 and 0 81 1 49 m kyr for coquille point and cape blanco respectively late quaternary uplift rates of marine terraces yield information about deformation in the overriding plate but it is unclear if such data vary systematically with convergent margin type in order to assess the utility of the southern oregon uplift rates for predicting the behavior of the cascadia subduction zone we compared late quaternary uplift rates derived from terrace data from subduction zones around the world on the basis of this comparison the southern oregon rates of vertical deformation are not unusually high or low furthermore late quaternary uplift rates show little relationship to the type of convergent margin these observations suggest that local structures may play a large role in uplift rate variability in addition while the type of convergent margin may place an upper limit on possible uplift rate greater upper limits serve to increase the range of possible uplift rates in the case of the southern oregon coast variability in uplift rate probably reflects local structures in the overriding plate and the rate of uplift cannot be used as a simple index of the potential for great earthquakes along the southern cascadia subduction zone

rapid late pleistocene holocene uplift and coastal evolution of the southern arabian persian gulf the coastline along the southern arabian gulf between al jubail kingdom of saudi arabia and dubai uae appears to have risen at least 125 m in the last 18 000 years dating and topographic surveying of paleo dunes 43 53 ka paleo marine terraces 17 30 ka and paleo marine shorelines 3 3 5 5 ka document a rapid 1 mm a subsidence followed by a 6 mm a uplift that is decreasing with time the mechanism causing this movement remains elusive but may be related to the translation of the coastal area through the backbasin to forebulge hinge line movement of the arabian plate or alternatively by movement of the underlying infracambrian age hormuz salt in response to sea level changes associated with continental glaciation independent of the mechanism rapid and episodic uplift may impact the design of engineering projects such as nuclear power plants airports and artificial islands as well as the interpretation of sedimentation and archeology of the area

an example of a recent accretion on the mid atlantic ridge the snake pit neovolcanic ridge mark area 23 22 n abstract the inner rift vailey of the mark area mid atlantic ridge at the kane fracture zone was investigated with the submersible nautile at the latitude of the snake pit hydrothermal field 23 22 n a transect across the axial valley shows a stepwise increase in the sediment thickness away from the axis these steps probably reflect major magmatic and tectonic events in the evolution of the inner floor dives on the summit of the snake pit neovolcanic ridge constrain a generalized geological map and document relations between hydrothermal activity magmatism and faulting the neovolcanic ridge was constructed by the build up of several hundred metres of pillow lava flows its summit is intensely fissured and cut by an axial graben about 100 m wide three hydrothermal sites were recognized within the axial graben the eastern site the most active is structurally related to the eastern fault scarp the central site is located within the graben the western site associated with the western fault scarp is more complex and was constructed by two successive hydrothermal events the new data suggest a model of evolution for the inner floor of the rift valley involving alternating stages of magmatism and volcanism which produce ridges and troughs preserved outside of the axial domain these volcano tectonic cycles have an approximate duration of 100 000 years we discuss variations in the morphology of the mar along strike in the light of this model of evolution

a mechanism for decoupling within the oceanic lithosphere revealed in the troodos ophiolite contrasting kinematic histories recorded in the sheeted dykes and underlying plutonic rocks of the troodos ophiolite provide a new perspective on the mechanical evolution of oceanic spreading centres the kinematic framework of the decoupling zone that partitions deformation between the sheeted dykes and plutonics contrasts with low angle detachment models for slow spreading ridges based on continental rift analogues a model for the generation of multiple horizontal decoupling horizons linked by planar normal faults demonstrates new possibilities for the kinematic and rheological significance of seismic reflectors in oceanic lithosphere

uranium series age constraints on lavas from the axial valley of the mid atlantic ridge mark area abstract mass spectrometric measurements of 230 th 226 ra 235 u 231 pa and 238 u 230 th disequilibria are used to determine eruption ages for four mid ocean ridge basalts from the median valley of the mid atlantic ridge south of the kane fracture zone mark area three samples were collected across axis on the axial volcanic ridge i e the neovolcanic ridge near the snake pit hydrothermal mound and one sample was collected near the crest of serocki volcano 50 km south of snake pit 226 ra 230 th and 230 th 238 u activity ratios are low and uniform for all four samples while 231 pa 235 u activity ratios are elevated and somewhat more variable age constraints suggest that these lavas from the most robust volcanic edifices in the mark area are 10 000 20 000 yr old the age data are used to evaluate the efficacy of commonly used age estimate scales based on qualitative indicators e g sediment cover glass quality and to begin to quantify the temporal and spatial dependence of volcanic tectonic and hydrothermal processes at slow spreading oceanic ridges

along axis variations in seafloor spreading in the mark area recent investigations with the manned submersible alvin and the angus deep towed camera sled greatly extended the known range of variations in the style of seafloor spreading along the axis of the mid atlantic ridge five transects of the spreading centre at intervals of10 20 km south of the kane fracture zone at 24 n latitude demonstrate dramatic changes in the style and magnitude of tectonic extension development of the neovolcanic zone expression of hydrothermal venting types oflithologic exposures and morphology of the median valley

beachrock a tool for reconstructing relative sea level in the far field abstract today s understanding of sea level change developed through a combination of process based physical modelling and observational data observational data of sea level change derives from coral reefs in the far field of the former ice sheets where a geographically variable relative sea level signal is expected as a response of the earth to ocean loading given this variability and the limited geographical distribution of coral reefs there is a need to explore other non coral based sea level markers to further understand sea level change and for example to fingerprint melt water here we present beachrock as a coastal deposit suitable for relative sea level rsl observations in the far field beachrock is an intertidal deposit forming in the zone where carbonate saturated meteoric and marine water mix and p co 2 decreases we provide the conceptual framework for beachrock analysis and describe techniques suitable for analysing and dating the deposit the approach is standardised by outlining the sediment characteristics in terms of rsl indicative meaning and indicative range and is tested against published data a study conducted on coasts of the mediterranean sea exemplifies the utility of beachrock for rsl reconstruction it is shown that the precision of the reconstruction is derived from the combined uncertainty of age and tidal amplitude or tidal range the uncertainty can be reduced to half the tidal amplitude when a deposit can be ascribed to the upper or lower intertidal zone beachrock based data benefit from the lack of non quantifiable error terms such as post depositional compaction due to the instantaneous formation and high preservation potential of the deposit this underlines the high precision of beachrock based rsl reconstruction which is a prime requirement for testing and extending coral based records

the tectonic evolution of the indian ocean triple junction anomaly 6 to present the tectonic evolution of the indian ocean ridge ridge ridge triple junction the junction of the central indian ridge cir southeast indian ridge seir and southwest indian ridge swir is inferred by mapping structures along its traces on the three plates with a long range side scan sonar geological long range inclined asdic gloria the sonar images to the west of the triple junction show two different styles of tectonic evolution some sections of the trace on the african plate are marked by a swir facing scarp containing fine lineaments that are probably normal faults these correspond with sections of the trace on the antarctic plate of the same age that have a sharp intersection of swir and seir abyssal hills that is to be expected from a simple ridge ridge ridge triple junction evolution a herringbone pattern of isochrons in contrast there are other sections of the trace on the african plate that have a blocky structure with no definite termination of cir abyssal hills against those of the swir the corresponding regions of the antarctic plate show large 10 to 30 km long overlapping fault scarps tapering to the northeast and ending in asymmetric valleys to the southwest these major normal faults are each offset by 1 6 km forming an en echelon series the two different styles of tectonic structures indicate two different modes of evolution although why the triple junction has evolved with two different modes is unclear periods of asymmetric spreading in the cir magnetic anomaly sequence collected on the african plate may possibly indicate that the cir and seir have been offset by a fracture zone at the triple junction during one of these two modes echo sounder traverses on the antarctic and african plates commonly show a steady shallowing of the cir and seir seafloor toward the traces a steep scarp facing the swir and a broad marginal deep at the base of this scarp this rift flank shape resembles that of the swir valley s rift shoulders close to the present triple junction mitchell 1991a suggesting that the mechanical evolution has been similar to the present day and the relief due to the rift flank uplift has been preserved by the cooling and strengthening of the lithosphere with age away from the ridge axes if the shape of the rift shoulder uplift along the trace on the antarctic plate is interpreted with a simple flexural model involving an end loaded elastic plate the inferred rigidity 1019 1021 n m or 2 6 km effective elastic thickness is consistent with the suggestion that the isostatic uplift occurred in young weak lithosphere close to the triple junction interestingly the observed 1 km relief of the trace escarpment and the estimated rigidity suggest that the uplift was produced by a load 2 5 1011 n m that is equivalent to half the present cross sectional area of the swir valley 35 km from the triple junction

thermal structure and megathrust seismogenic potential of the makran subduction zone the makran subduction zone experienced a tsunamigenic mw 8 1 earthquake in 1945 and recent smaller earthquakes also suggest seismicity on the megathrust however its historical record is limited and hazard potential enigmatic we have developed a 2 d thermal model of the subduction zone the results are twofold 1 the thick sediment cover on the incoming plate leads to high 150 plate boundary temperatures at the deformation front making the megathrust potentially seismogenic to a shallow depth and 2 the shallow dip of the subducting plate leads to a wide potential seismogenic zone up to 350 km combining these results with along strike rupture scenarios indicates that mw8 7 9 2 earthquakes are possible in the seaward makran subduction zone these results have important earthquake and tsunami hazard implications particularly for the adjacent coastlines of pakistan iran oman and india as the makran has not been previously considered a likely candidate for a mw 9 earthquake

lithological mapping of the troodos ophiolite cyprus using airborne lidar topographic data traditional field based lithological mapping can be a time consuming costly and challenging endeavour when large areas need to be investigated where terrain is remote and difficult to access and where the geology is highly variable over short distances consequently rock units are often mapped at coarse scales resulting in lithological maps that have generalised contacts which in many cases are inaccurately located remote sensing data such as aerial photographs and satellite imagery are commonly incorporated into geological mapping programmes to obtain geological information that is best revealed by overhead perspectives however spatial and spectral limitations of the imagery and dense vegetation cover can limit the utility of traditional remote sensing products the advent of airborne light detection and ranging lidar as a remote sensing tool offers the potential to provide a novel solution to these problems because accurate and high resolution topographic data can be acquired in either forested or non forested terrain allowing discrimination of individual rock types that typically have distinct topographic characteristics this study assesses the efficacy of airborne lidar as a tool for detailed lithological mapping in the upper section of the troodos ophiolite cyprus morphometric variables including slope curvature and surface roughness were derived from a 4 m digital terrain model in order to quantify the topographic characteristics of four principal lithologies found in the area an artificial neural network the kohonen self organizing map was then employed to classify the lithological units based upon these variables the algorithm presented here was used to generate a detailed lithological map which defines lithological contacts much more accurately than the best existing geological map in addition a separate map of classification uncertainty highlights potential follow up targets for ground based verification the results of this study demonstrate the significant potential of airborne lidar for lithological discrimination and rapid generation of detailed lithological maps as a contribution to conventional geological mapping programmes

spreading induced faulting and fracturing of oceanic crust examples from the sheeted dyke complex of the troodos ophiolite cyprus

changing moisture sources over the last 330 000 years in northern oman from fluid inclusion evidence in speleothems speleothems from hoti cave in northern oman provide a record of continental pluvial periods over the last 330 000 yr periods of rapid speleothem deposition occurred from 6000 to 10 500 78 000 to 82 000 120 000 to 135 000 180 000 to 200 000 and 300 000 to 330 000 yr ago with little or no growth during the intervening periods during each of these five pluvial periods d values of water extracted from speleothem fluid inclusions dfi are between 60 and 20 vsmow and 18o values of speleothem calcite 18oc are between 12 and 4 to vpdb these values are much more negative than modern rainfall for d or modern stalagmites for 18o previous work on the isotopic composition of rainfall in oman has shown that northern and southern moisture sources are isotopically distinct combined measurements of the d values of fluid inclusion water with calculated 18o values from peak interglacial speleothems indicate that groundwater was predominantly recharged by the southern indian ocean moisture source when the monsoon rainfall belt moved northward and reached northern oman during each of these periods

late devensian and holocene shorelines of the british isles and north sea from models of glacio hydro isostatic rebound sea level change around the british isles since the time of the last glacial maximum is largely due to of the crustal rebound from the glacial unloading of northern britain and the concomitant melt water loading of the adjacent seas and atlantic ocean minor but not insignificant contributions also result from the rebound caused by the unloading of the distant ice sheets including fennoscandia and north america observations of sea level change for this period constrain the glacio hydro isostatic rebound model parameters describing the effective lithospheric thickness or rigidity and the effective mantle viscosity as well as certain ice sheet characteristics such as the ice thickness at the time of the last glacial maximum the models permit palaeobathymetry and palaeoshorelines to be predicted for the british isles region including the north sea the resulting evolution of the coastlines exhibits a complex behaviour through time one that is quite different from the usual models in which sea level change is assumed to be a function of time only in part this is because of the delayed response of the mantle to the spatially variable and time dependent ice and water loads and in part because the unloading history of the british ice sheet is different from those of the major global ice sheets thus maximum emergence of the north sea occurred after deglaciation had started and lasted for an extended period from about 15 000 to 12 000 radiocarbon years bp during this relative sea level still stand shoreline features could have formed for example along the western edge of the norwegian trough when access to the firths of eastern scotland would have been via a long and shallow marine inlet shoreline retreat across the north sea became relatively rapid after about 10000 years the model predictions for the irish and celtic seas also suggest a complex behaviour with the formation of a wide land bridge between about 20000 and 13 000 years ago the model also suggests that as long as the scottish ice extended across the northern irish sea until about 14 000 years ago there would have been a large freshwater periglacial lake located further south both the predicted sea level height age relations and the shoreline positions are consistent with a large body of observational evidence but some discrepancies occur particularly in northern scotland and ireland where the ice heights may have been somewhat greater than assumed in the model

quaternary normal faulting in southeastern sicily italy a seismic source for the 1693 large earthquake summary we present geological and morphological data combined with an analysis of seismic reflection lines across the ionian ovshore zone and information on historical earthquakes in order to yield new constraints on active faulting in southeastern sicily this region one of the most seismically active of the mediterranean is avected by wnw ese regional extension producing normal faulting of the southern edge of the siculo calabrian rift zone our data describe two systems of quaternary normal faults characterized by diverent ages and related to distinct tectonic processes the older nw se trending normal fault segments developed up to 400 kyr ago and striking perpendicular to the main front of the maghrebian thrust belt bound the small basins occurring along the eastern coast of the hyblean plateau the younger fault system is represented by prominent nnw sse trending normal fault segments and extends along the ionian ovshore zone following the ne sw trending avola and rosolini ispica normal faults these faults are characterized by vertical slip rates of 0 7 3 3 mm yr 1 and might be associated with the large seismic events of january 1693 we suggest that the main shock of the january 1693 earthquakes m 7 could be related to a 45 km long normal fault with a right lateral component of motion a long term net slip rate of about 3 7 mm yr 1 is calculated and a recurrence interval of about 550 50 yr is proposed for large events similar to that of january 1693

beachrock as sea level indicator a case study at the coastline of oman indian ocean abstract future sea level changes are a threat to coastal communities worldwide therefore reliable methods for the reconstruction of past relative sea level variations are essential to make predictions of future developments beachrocks are a widely distributed indicator of quaternary paleo coastlines with a high potential for preservation nevertheless their use as sea level indicator faces challenges in the determination of the exact elevation of beachrock formation with respect to paleo sea level this information is crucial to the establishment of a sea level index point our study area on the northeastern coastline of oman shows a set of twelve marine terraces that reach a height of 500 m above mean sea level while the upper terraces are erosional the lowest three are depositional on the erosional terraces beachrocks are the only sediment cover that withstood erosion on the depositional terraces however beachrocks occur alongside other sediments which can be fluvial alluvial or marine in origin the coastal development of the area is of high interest as uplift and tectonic activity are ongoing fieldwork and petrographic methods on eight outcrops on three terrace levels led to the identification of eight lithofacies in six facies associations we used facies analysis to improve the information on paleo sea level as derived by the sole use of geomorphological indicators here we demonstrate that facies analysis so far applied exclusively on sandy deposits is applicable also to gravel dominated systems the results contribute to knowledge on local changes in the depositional environment and help to reconstruct uplift rates

quaternary marine terraces as indicators of neotectonic activity of the ierapetra normal fault se crete greece abstract along the southern coast of the island of crete a series of east west oriented late pleistocene marine terraces exist demonstrating the significant coastal uplift of this area five uplifted terraces were mapped in detail and correlated with middle late pleistocene sea level stands following the global sea level fluctuations these terraces are deformed by the vertical movements of the nne ssw trending and dipping west ierapetra normal fault the elevation of the inner edges of the terraces was estimated at several sites by using aerial photographs and detailed topographic maps and diagrams supported by extensive field observations in this way detailed geomorphological maps were constructed utilizing gis technology all these allowed us to obtain rates of 0 3 mm yr for the regional component of uplift and 0 1 mm yr for the vertical slip movements of the ierapetra fault based on the obtained rates and the existence of coastal archaeological roman ruins it is concluded that ierapetra fault should have been reactivated sometime after the roman period

quaternary uplift along a passive continental margin oman indian ocean abstract crustal movement along the coastline of the arabian sea in oman is quantified along a 72 km long coastal section characterised by staircases of marine terraces an extensive topographic geomorphological and geological survey was conducted on these terraces and an age model based on cosmogenic nuclide 10be 36cl and optically stimulated luminescence dating is presented together with a new approach to extract palaeo shorelines from a high resolution digital elevation model the uplifting crustal block is fault bounded and is composed of obduction related peridotites overlain by shallow marine limestone nine distinct terrace levels are identified and the results indicate continuous uplift between marine isotope stage mis 5a and mis 19 the calculated uplift rates vary along the coastline and a northward tilting of the uplifted coastal block is interpreted as evidence for differential uplift the geomorphology of the terraces proves that the tilting must have taken place after the last interglacial tectonic forcing of the uplift by a crustal forebulge associated with the makran subduction zone is discussed it is also concluded that the uplift involves processes of serpentinisation of the peridotites in combination with karstification of the overlying limestone formations as water is essential for both processes climate change during the quaternary apparently played a significant role in the uplift process as well as hydro isostasy

evidence for a younger dryas deglaciation in the galicica mountains fyrom from cosmogenic 36cl abstract this study presents the first cosmogenic 36cl surface exposure data from a moraine in the former yugoslav republic of macedonia fyrom five limestone boulders from an end moraine in the galicica mountains 40 94 n 20 83 e 2050 m a s l were used for cosmogenic 36cl surface exposure dating the 36cl concentrations from the five boulders are identical within their measurement uncertainties ruling out major effects of inheritance erosion or snow cover the calculated ages are very consistent ranging from 11 3 1 3 to 12 8 1 4 ka mean 12 0 6 ka after applying a ca spallation production rate of 56 at g 1 a 1 lsd scaling and correction for 5 mm ka 1 carbonate weathering and 2 snow shielding the applied corrections for weathering and snow shielding cause a shift to older ages in the order of magnitude of ca 5 on average making the production rate the main impact on exposure ages the ages point to a moraine formation during the younger dryas period consistent with the timing of the last deglaciation in the galicica mountains derived from previous geomorphological studies in the area the formation of a glacier was likely favoured by several topoclimatic factors accounting for additional snow input this interpretation is in line with regional studies on glaciation chronologies from sara range fyrom republic of kosovo retezat mountains romania mt chelmos greece mount orjen montenegro and durmitor montenegro lake sediment analyses of prespa republic of albania fyrom greece maliq republic of albania and dojran lakes fyrom greece indicate that cold conditions promoted the formation of a local cirque glacier however studies of sediment records of the adjacent lakes ohrid republic of albania fyrom and prespa do not indicate the presence of a proximal glaciation an explanation might be a combination of the small size of the cirque glacier generating only small amounts of debris and the karstic bedrock which hampers fluvial transport and acts by its aquifer system as a natural sediment trap as the fluvial transport of the sediments to the lakes is absorbed by the karst system

sea level and deep sea temperature variability over the past 5 3 million years ice volume and hence sea level and deep sea temperature are key measures of global climate change sea level has been documented using several independent methods over the past 0 5 million years myr older periods however lack such independent validation all existing records are related to deep sea oxygen isotope 18o data that are influenced by processes unrelated to sea level for deep sea temperature only one continuous high resolution mg ca based record exists with related sea level estimates spanning the past 1 5 myr here we present a novel sea level reconstruction with associated estimates of deep sea temperature which independently validates the previous 0 1 5 myr reconstruction and extends it back to 5 3 myr ago we find that deep sea temperature and sea level generally decreased through time but distinctly out of synchrony which is remarkable given the importance of ice albedo feedbacks on the radiative forcing of climate in particular we observe a large temporal offset during the onset of plio pleistocene ice ages between a marked cooling step at 2 73 myr ago and the first major glaciation at 2 15 myr ago last we tentatively infer that ice sheets may have grown largest during glacials with more modest reductions in deep sea temperature a novel approach to the estimation of sea level and deep sea temperature has been used to determine these quantities over the past 5 3 million years this approach based on oxygen isotope records from the eastern mediterranean shows that temperature and sea level histories are broadly correlated but also show intriguing temporal offsets most records of past sea level variation and associated changes in ocean temperature rely on variations in oxygen isotopes recorded in deep sea marine microorganisms these signals unfortunately are confounded by other influences making it difficult to extract a clear climate related signal eelco rohling and colleagues now present a novel approach to estimating sea level and deep sea temperature variations for the past 5 3 million years the record based on oxygen isotope variations from the eastern mediterranean avoids the issues of the deep sea approach and generally corresponds to an independent record of the past 1 6 million years as expected temperature and sea level are broadly correlated but also show intriguing temporal discontinuities as at the initiation of plio pleistocene ice ages when a major sea level drop lagged a sharp temperature decline by several hundred thousand years

deformation of the 125 ka marine terrace in italy tectonic implications in peninsular italy marine terraces and shorelines created during oxygenisotope substage 5e known historically as the tyrrhenian highstand provide a reliable and homogeneous datum of vertical motions during the past 125 000 years published accounts of 121 locations on the tyrrhenian inner edge were reinterpreted and used to calculate both local and regional uplift rates the data show arching of southern italy between the tyrrhenian and the adriatic coasts and of the calabrian arc between the sangineto and the longi taormina tectonic lineaments at rates of up to 1 2 mm yr for the past 125 ka they also suggest that the present configuration of the southern apennines is the product of post early pleistocene regional uplift superimposed on tortonian to early pleistocene thrusting uplift patterns are characterised by different wavelength in different geodynamic settings suggesting a close link with the depth of the causative tectonic sources

tectonic and climatic implications of alluvial fan sequences along the batinah coast oman along the batinah coast in northern oman seven levels of alluvial fan remnants stretching from the oman mountains to the gulf of oman were considered evidence for quaternary uplift by previous workers we suggest that these regionally extensive fan remnants were instead caused by quaternary climate fluctuations acting on the oman mountain headwaters and the major wadi systems the gradients of these wadis were oversteepened twice by mid tertiary uplift of the mountains and by a major plio pleistocene alluvial aggradation event wadi channels are still being cut through this massive deposit the episodic nature of climatically induced downcutting has produced the fan terrace levels the southern batinah coast is a hinge zone about which the arabian plate is tilting as it collides with the eurasian plate to the north the musandam peninsula and the associated fans are subsiding in response to subduction to the south uplifted marine shorelines suggest an apparent rigid plate response to the northward subduction

bajada formation by monsoonal erosion of a subaerial forebulge sultanate of oman abstract a vast low gradient bajada is present in the interior of northern oman with an area of 40 000 km2 and longitudinal gradients less than 0 3 this late cenozoic bajada is 10 times larger and 10 times flatter than classical bajadas the tectonic and climatic setting that favored aerially extensive bajada formation is investigated in this paper a tectonic model is proposed that involves forebulge development associated with subduction of the arabian plate beneath the asian plate the model identifies the southern gulf of oman as a foredeep the oman mountains as a subaerial forebulge the vast bajada as a deposit that blankets the distal forebulge and the umm as samim sabkha as a backbulge basin deposit the model is supported by an excellent match between modern topography and a theoretical flexural profile of the omani lithosphere by the lateral distribution of pliocene pleistocene sediments by the inferred late miocene to pleistocene age span of the vast bajada and by evidence of active surface uplift of the oman mountains a second mechanism post orogenic exhumation of the pre existing oman mountains is likely to have accompanied and perhaps slightly preceded forebulge growth facilitating erosion and transport of sediment across the forebulge evidence for a palaeoclimatic model is provided by previous sedimentological studies and stable isotope data of cements in channel gravels as well as proxy data from odp leg 117 oman margin transport of coarse grained sediment across the bajada is interpreted to have occurred mainly during the late miocene to early pleistocene when a humid wet climate prevailed across arabia high water tables and accompanying cementation of bajada gravels may have aided long distance transport the evolution of surficial bajada sediments is correlated with changing climatic and hydrological conditions from seasonal perennial flows during the pliocene and before to mainly ephemeral and finally flash flood flows signifying increasing aridity during the pleistocene these data imply that the indian ocean monsoon represented by rainfall frequency and intensity had a more northerly range in arabia in the past compared to the present

geochronology of tag and snakepit hydrothermal fields mid atlantic ridge witness to a long and complex hydrothermal history geochronological studies of a large number of precipitates from the tag hydrothermal field and of few samples from snakepit hydrothermal field of the mid atlantic ridge show intermittent repeated hydrothermal events at both sites 210pb pb and 230th 234u measurements of sulfides iron and manganese oxides and 14c measurements of carbonates combined with observations of hydrothermal events recorded as discrete layers in sediment cores provide the basis for unravelling the temporal history of the fields the tag field shows intermittent activity over the past 120 000 years as evidenced by ages of low temperature mn oxides the presently active black smoker mound first formed about 40 000 50 000 years ago with precipitation of massive sulfides it has had intermittent pulsed high temperature activity every 5000 6000 years over the past 20 000 years which may reflect renewed magmatic activity at the ridge axis fluid flow is focussed at the mound site by structural and tectonic control suggested by the intersection of n s ridge parallel lystric normal faults and an e w transform fault periods of inactivity are marked by covering of the mound with pelagic carbonate ooze which is probably partially dissolved and reprecipitated as aragonite at the end of each high temperature event the snakepit field had an initial event about 4000 years ago probably shortly after the eruption of the volcanic ridge on which it sits a recent renewal still presently active was probably initiated by recent fissuring of the volcanic pile

impact of crustal evolution on changes of the seismic properties of the uppermost ocean crust one of the most important observations of oceanic crustal evolution is that the uppermost part of the igneous crust layer 2a appears to thin and eventually disappear as its seismic velocity doubles from approximately 2 2 to 4 5 km s 1 in the first 40 m y the most likely cause is decreasing porosity in extruded basalts that compose the uppermost igneous crust by filling cracks with hydrothermally generated minerals a by product of off axis hydrothermal circulation and alteration of basalts new insights from two recent papers on crustal hydrothermal circulation patterns and modeling of the effects of crack geometry distributions upon seismic velocities provide guidance to relate filling of cracks within the basement to seismic velocity increases a qualitative model of layer 2a crustal evolution is outlined that satisfies many geophysical and geochemical observations some seemingly unrelated somewhat surprisingly the crustal age at which layer 2a seismic velocities reach their maximum value is primarily controlled by the integrated permeability of the overlying sediment which in turn controls the hydrologic regime necessary for secondary mineral precipitation speculative predictions can be used to verify refine or invalidate this dynamic model of crustal evolution major scientific and technical obstacles must be overcome before a definitive model can be quantified with such a rigorous model of crustal upper crustal evolution in hand remote geophysical sensing tools can begin to fulfill the promise of interpreting the physical state composition and past history of oceanic crust

surface uplift uplift of rocks and exhumation of rocks uplift of the surface of mountain belts requires forces that are comparable in magnitude to those associated with plate motion and therefore determination of rates of surface uplift could provide important information on the dynamics of mountain ranges rates of uplift of the surfaces of mountain ranges have not however been quantified sufficiently well that they provide useful constraints on those processes many reports off surface uplift in mountain ranges are based on mistaking exhumation of rocks or uplift of rocks for surface uplift and provide no information whatsoever on the rates of surface uplift

karst driven flexural isostasy in north central florida deformed marine terraces can be used to explore a region s uplift history trail ridge is a marine terrace in north florida that is nearly 80 meters above modern sea level and contains quaternary marine fossils a fact that is inconsistent with estimates of paleo sea level history since the early pleistocene this implies that the terrace has experienced uplift since its formation as well as non uniform deformation recorded by the warping of its previously horizontal state the florida carbonate platform located on the passive margin of eastern north america is a setting where non tectonic influences e g isostatic adjustment dynamic topography can be examined we present a single transect numerical model of vertical displacement derived from elastic flexure to assess the influence of karst driven isostatic uplift on present day topography of trail ridge in north florida flexural modeling predicts elevations in central florida not observed today most likely because surface erosion and karst cavity collapse have obliterated this high topography older subsurface stratigraphic units however display the arched profile predicted from flexural modeling mass loss calculated by differencing modeled topography and observed topography was found to be 6 75 1012 kg since emplacement of trail ridge uplift rates assuming karst driven flexural isostasy alone using previously estimated ages of trail ridge of 0 125 1 4 3 or 3 5 ma were found to be 0 535 0 048 0 022 and 0 019 mm yr respectively a more likely explanation of uplift includes contributions from dynamic topography and glacial isostatic adjustment which should be further explored with more advanced geophysical modeling

lithospheric strength and rheological stratification at mid ocean ridges lithosphere at mid ocean ridges is rheologically stratified the extensional failure of rheologically stratified lithosphere can be modelled by integrating the appropriate failure criteria over the appropriate depths to the base of the lithosphere this integrated lithospheric strength is the force per unit length required for whole lithospheric failure to occur oceanic spreading centres are in a nearly constant state of whole lithospheric failure lithosphere at a given ridge axis has a characteristic integrated strength which is met for spreading to continue variations in integrated strength have important implications for tectonic phenomena such as jumps at spreading centres

crustal structure of the mid atlantic ridge south of the kane fracture zone from seafloor and sea surface gravity data seafloor and sea surface gravity data are inverted together to construct a model for the near axis crustal structure of a slow spreading ridge the seafloor data set offers two main advantages it allows us to recover shorter wavelengths signal and to constrain the value of a potential field at two different levels the model we propose here would not have been derived from sea surface data alone it is based on a dense sea surface gravity coverage and on 121 sea bottom gravity measurements collected in the mid atlantic ridge at kane mark area during the hydrosnake 1988 and gravinaute 1993 cruises the primary goal of the seafloor surveys was to test for the presence of a magma reservoir beneath the axial neovolcanic ridge first a forward two dimensional 2 d model of the crustal structure across the axis is fit to observed gravity anomalies using constraints from geological and structural observations bouguer anomalies computed from sea bottom measurements and downward continuation of sea surface measurements both constrain the forward modeling this forward model is the starting point of a 2 d monte carlo inversion of seafloor and sea surface data in addition to the crustal thickness variations along axis our data document the amplitude variations of the crustal thickness and or its density in the across axis direction the model resulting from our inversion exhibits several features of the crustal structure in the mark area 1 the presence of a low density ap 300 50 kg m 3 body beneath the neovolcanic ridge is suggested and could correspond to a magma chamber or more probably to a highly hydrothermally fissured zone 2 both long and short wavelength gravity signals exhibit a difference between the western and eastern sides of the axial domain the mean value and the amplitude of bouguer anomalies are higher on the western part this difference suggests that axial processes in this area are very asymmetric 3 abyssal hills are not associated with a single gravity signature for instance on the west side of the axis one of the explored hills has no bouguer anomaly and is interpreted as a neovolcanic ridge whereas the others are associated with a shifted bouguer anomaly high and are interpreted as having thinner magmatic crust 4 the last feature of the crustal fabric we document here is the asymmetric emplacement of some deep rocks outcrops in the mark area we find that pink hill a topographic high where serpentinized peridotites are outcropping is much more serpentinized on its east flank toward the axial valley than on its west flank alteration occurring mainly by fluid circulation through faulted zones the asymmetric serpentinization suggests that deep origin rocks have outcropped by means of a main fault zone and are not emplaced by diapirism

dating sediment burial with in situ produced cosmogenic nuclides theory techniques and limitations abstract dating sediment burial over million year time scales is crucial in many areas of the earth sciences and archeology but is often difficult using traditional techniques sediment burial can be dated by the radioactive decay of cosmogenic nuclides provided that the sediment was exposed to cosmic rays prior to burial dating calculations are straightforward if sediment is buried deeply and rapidly enough to prevent cosmogenic nuclide production after burial however the analysis can be complicated by postburial production if sediment is insufficiently shielded from secondary cosmic ray nucleons and muons this paper discusses how buried sediments can be dated over timescales up to 5 myr using 26 al and 10 be in quartz

coastal neotectonics in southern central andes uplift and deformation of marine terraces in northern chile 27 s abstract neotectonic observations allow a new interpretation of the recent tectonic behaviour of the outer fore arc in the caldera area northern chile 27 s two periods of deformation are distinguished based on large scale neogene to quaternary features of the westernmost part of the coastal cordillera late miocene to early pliocene deformations characterized by a weak ne sw to e w extension is followed by uppermost pliocene nw se to e w compression the middle pleistocene to recent time is characterized by vertical uplift and nw se extension these deformations provide clear indications of the occurrence of moderate to large earthquakes microseismic observations however indicate a lack of shallow crustal seismicity in coastal zone we propose that both long term brittle deformation and uplift are linked to the subduction seismic cycle

relative sea level fall since the last interglacial stage are coasts uplifting worldwide the growing interest in quantification of vertical ground motion stems from the need to understand in detail how the earth s crust behaves for both scientific and social reasons however only recently has the refinement of dating techniques made possible the use of paleoshorelines as reliable tools for tectonic studies although there are many local studies of quaternary vertical motions of coastlines we know of no comprehensive worldwide synthesis here we provide a compilation of 890 records of paleoshoreline sequences with particular emphasis on the last interglacial stage marine isotopic stage mis 5e 122 ka the quality of dating mis 5e makes it a reliable marker to evaluate vertical ground motion rates during the late quaternary on a global scale the results show that most coastal segments have risen relative to sea level with a mean uplift rate higher than 0 2 mm yr i e more than four times faster than the estimated eustatic drop in sea level the results also reveal that the uplift rate is faster on average for active margins than for passive margins neither dynamic topography nor glacio hydro isostasy may explain sustained uplift of all continental margins as revealed by the wide distribution of uplifted sequences of paleoshorelines instead we suggest that only plate tectonic processes reconcile all observations of quaternary coastal uplift we propose that long term continental accretion has led to compression of continental plates and uplift of their margins therefore this study concludes that plate tectonics processes impact all margins and emphasizes the fact that the notion of a stable platform is unrealistic these results therefore seriously challenge the evaluation of past sea levels from the fossil shoreline record