practical application of the sequential balancing technique an example from the irish variscides the process of sequential restoration presented by cooper trayner 1986 is applied to a n s cross section through the irish variscides to demonstrate that this approach improves the accuracy of thin skinned structural modelling and allows the progressive deformation of a marginal belt to be examined the principles and methods of sequential restoration are illustrated the cross section is restored in four steps and gives a bulk shortening of 52 in this model the fold belt evolved as the basal decollement migrated northwards and considerable ductile shortening by folding and cleavage formation preceded faulting although faulting gradually became more important towards the north the section is divided into four structural domains based upon different deformation histories each is restored independently by removing the ductile strain before restoring the faulting from this example it is clear that many models derived from single step balancing especially those through ductile deformed areas should be re examined

seismicity deformation and seismic hazard in the western rift of corinth new insights from the corinth rift laboratory crl this paper presents the main recent results obtained by the seismological and geophysical monitoring arrays in operation in the rift of corinth greece the corinth rift laboratory crl is set up near the western end of the rift where instrumental seismicity and strain rate is highest the seismicity is clustered between 5 and 10 km defining an active layer gently dipping north on which the main normal faults mostly dipping north are rooting it may be interpreted as a detachment zone possibly related to the phyllade thrust nappe young active normal faults connecting the aigion to the psathopyrgos faults seem to control the spatial distribution of the microseismicity this seismic activity is interpreted as a seismic creep from gps measurements which shows evidence for fast continuous slip on the deepest part on the detachment zone offshore either the shallowest part of the faults is creeping or the strain is relaxed in the shallow sediments as inferred from the large ns strain gradient reported by gps the predicted subsidence of the central part of the rift is well fitted by the new continuous gps measurements the location of shallow earthquakes between 5 and 3 5 km in depth recorded on the on shore helike and aigion faults are compatible with 50 and 60 mean dip angles respectively the offshore faults also show indirect evidence for high dip angles this strongly differs from the low dip values reported for active faults more to the east of the rift suggesting a significant structural or rheological change possibly related to the hypothetical presence of the phyllade nappe large seismic swarms lasting weeks to months seem to activate recent synrift as well as pre rift faults most of the faults of the investigated area are in their latest part of cycle so that the probability of at least one moderate to large earthquake m 6 to 6 7 is very high within a few decades furthermore the region west to aigion is likely to be in an accelerated state of extension possibly 2 to 3 times its mean interseismic value high resolution strain measurement with a borehole dilatometer and long base hydrostatic tiltmeters started end of 2002 a transient strain has

holocene and quaternary uplift in the central part of the southern coast of the corinth gulf greece abstract the southern coast of the gulf of corinth greece has long been recognized as an area of rapid quaternary uplift in a normal faulting environment but the amplitude dating and significance of this uplift remain a matter of debate mainly due to the scarcity of reliable and detailed estimates of holocene and longer term uplift evidence of holocene emergence is analysed for two sites in the most uplifted area of the southern coast of the gulf of corinth at mavra litharia the uppermost holocene marine limit has been identified at 9 3 m and dated about 7100 14 c years bp near platanos where the holocene marine limit is above 12 5 m in situ infralittoral boring shells at 11 5 m have been dated about 4800 14 c years bp average uplift rates can be estimated between 2 9 and 3 5 mm year at mavra litharia and possibly even greater ca 2 1 2 7 mm year near platanos the pattern of the variation of holocene uplift along the coast seems to mimic the pattern of late quaternary terraces well constrained in the eastern pattern of the gulf corinth xylokastro area

crustal strain in central greece from repeated gps measurements in the interval 1989 1997 summary a 66 station gps network spanning central greece first observed in 1989 has been occupied fully on three occasions june 1989 october 1991 and may 1993 subsets of this network bounding the gulf of korinthos have also been occupied in june 1995 october 1995 may 1996 and september october 1997 the first three occupations were processed using a fiducial gps methodology whereas later surveys were processed using code precise orbits combination of data from different surveys to yield smooth site velocities requires global network translations at each epoch to compensate for errors in the realization of the reference frame this method provides a posteriori estimates of the relative coordinate errors and reference frame noise only one earthquake the 1995 june 15 egion event has caused significant local coseismic displacement and its effects on the interseismic velocity field are removed using an elastic dislocation model we constrain the orientation of the 100 yr triangulation gps velocity estimates of davies et al 1997 using 14 sites common to the two networks the goodness of fit of this transformation indicates that the short term and 100 yr geodetic estimates of deformation are highly compatible we infer that short term geodetic studies are capable of determining longer term deformation rates provided that transient local effects can be modelled from the combined velocity field we estimate principal strains and rigid body rotation rates at points on a regular grid using data from neighbouring sites strain rates are high within the gulf of korinthos and much lower elsewhere the extension rate across the gulf of korinthos increases from east to west comparison of the extension rate with historical and recent rates of seismic release of strain reveals significant medium term seismic hazard in the western gulf of korinthos and may also indicate long term aseismic strain

new constraints on the active tectonic deformation of the aegean 1 site velocities from six separate global positioning system gps networks comprising 374 stations have been referred to a single common eurasia fixed reference frame to map the velocity distribution over the entire aegean we use the gps velocity field to identify deforming regions rigid elements and potential microplate boundaries and build upon previous work by others to initially specify rigid elements in central greece the south aegean anatolia and the sea of marmara we apply an iterative approach tentatively defining microplate boundaries determining best fit rigid rotations examining misfit patterns and revising the boundaries to achieve a better match between model and data short term seismic cycle effects are minor contaminants of the data that we remove when necessary to isolate the long term kinematics we find that present day aegean deformation is due to the relative motions of four microplates and straining in several isolated zones internal to them the rms misfit of model to data is about 2 sigma very good when compared to the typical match between coseismic fault models and gps data the simplicity of the microplate description of the deformation and its good fit to the gps data are surprising and were not anticipated by previous work which had suggested either many rigid elements or broad deforming zones that comprise much of the aegean region the isolated deforming zones are also unexpected and cannot be explained by the kinematics of the microplate motions strain rates within internally deforming zones are extensional and range from 30 to 50 nanostrain year nstrain year 10 9 year 1 to 2 orders of magnitude lower than rates observed across the major microplate boundaries lower strain rates may exist elsewhere within the microplates but are only resolved in anatolia where extension of 13 4 nstrain year is required by the data our results suggest that despite the detailed complexity of active continental deformation revealed by seismicity active faulting fault geomorphology and earthquake fault plane solutions continental tectonics at least in the aegean is to first order very similar to global plate tectonics and obeys the same simple kinematic rules although the widespread distribution of aegean seismicity and active faulting might suggest a rather spatially homogeneous seismic hazard the focusing of deformation near microplate boundaries implies the highest hazard is comparably localized

structure of lower carboniferous basins of nw ireland and its implications for structural inheritance and cenozoic faulting abstract the geometry of lower carboniferous basins across the northern part of ireland is characterised by a gradual change in polarity of structure from a predominantly southward dipping fault system in northern ireland through the lough allen basin and into a mainly northward dipping fault system of connemara in the southwest this polarity change is reflected in the emergence of northward facing uplifted footwall blocks such as at croagh patrick and the ox mountains in the southwest with southward facing blocks in the northeast despite these structural changes there is a great degree of along strike continuity of lower carboniferous structure strain and displacement with the system forming a link between comparable sized and coeval basins in northern england and scotland to the east and the canadian maritime provinces to the west the spatial distribution of carboniferous normal faults suggests that caledonian structure such as the fair head clew bay line plays an important role in the localisation of post caledonian strain although the reactivation of individual caledonian structures may be less common the terrain of the west of ireland is strongly influenced by major carboniferous faults offsetting the base carboniferous unconformity as opposed to previously suggested cenozoic normal faulting of a tertiary peneplain

fluvial landscape response time how plausible is steady state denudation whether or not steady state topography and denudation are probable states depends on the timescale of system response to tectonic and climatic perturba tions relative to the frequency of those perturbations this paper presents analytical derivations of algebraic relations for the response time of detachment limited fluvial bedrock channel systems both to tectonic and climatic perturbations detachment limited fluvial erosion is described by the stream power incision model and the derivations are limited to the applicability of that model all factors likely to influence system response time that are not adequately captured by the stream power incision model will tend to increase the response time the calculations presented thus provide minimum estimates of landscape response time and therefore over predict the prob ability of attaining and sustaining steady state topography and denudation the central range of taiwan is used as a case study to estimate response times in a landscape often argued to be in steady state model parameters are fit to modern stream profiles by assuming that the topography represents a quasi steady state form estimated response times generally range from 0 25 to 2 5 ma depending on the non linearity of the incision rule and the magnitude and type of perturbation thus it may be reasonably argued that steady state topography and denudation are likely to prevail during periods of climatic stability response time is sufficiently short compared with plate tectonic timescales however rapid climatic fluctuation in the quaternary appears to preclude the attainment of steady state conditions in modern orogens motivation

differentiating geology and tectonics using a spatial autocorrelation technique for the hypsometric integral 1 hypsometry is thought to be sensitive to tectonic uplift rates and lithology differences in this study we calculated hypsometric integrals his using as topographic sources two digital elevation models of 10 and 90 m of pixel resolution in the granada basin se of spain the hi spatial distributions do not show clear spatial patterns and do not correlate with basin parameters as mean elevation or relief amplitude however when exploratory spatial data analysis is applied to the data distributions through local indices of spatial autocorrelation clear hot spots are visible that improve the geologic meaning of the hi the distributions are robust and independent of the model resolution but are scale influenced the application of this new method to the granada basin shows a strong correlation between the main distribution of active normal faults in the basin and the clusters of high or low hi values obtained in our analysis clusters with high hi values define the uplifted footwalls of these faults and regions uplifted in relation with rollover anticlines or where epeirogenic uplift has not been counteracted by local extension once the method was adjusted in the granada basin we tested its applicability in an area of known contractive tectonic activity central otago new zealand showing that the meaning of hi values is improved by using the autocorrelation techniques

cleavage strain in the variscan fold belt county cork ireland estimated from stretched arsenopyrite rosettes abstract in south west ireland hydrothermally formed arsenopyrite crystals in a devonian mudstone have responded to variscan deformation by brittle extension fracture and fragment separation the interfragment gaps and terminal extension zones of each crystal are infilled with fibrous quartz stretches within the cleavage plane have been calculated by the various methods available most of which can be modified to incorporate terminal extension zones the strain reversal method is the most accurate currently available but still gives a minimum estimate of the overall strain the more direct hossain method which gives only slightly lower estimates with this data is more practical for field use a strain ellipse can be estimated from each crystal rosette composed of three laths assuming the original interlimb angles were all 60 and because actual rather than relative stretches are estimated this provides a lower bound to the area increase in the plane of cleavage based on the average of our calculated strain ellipses this area increase is at least 114 and implies an average shortening across the cleavage of at least 53 however several lines of evidence suggest that the cleavage deformation was more intense and more oblate than that calculated and we argue that a 300 area increase in the cleavage plane and 75 shortening across the cleavage are more realistic estimates of the true strain furthermore the along strike elongation indicated is at least 80 which may be regionally significant estimates of orogenic contraction derived from balanced section construction should therefore take into account the possibility of a substantial strike elongation and tectonic models that can accommodate such elongations need to be developed

the structures stratigraphy and evolution of the gulf of corinth rift greece summary a multichannel seismic and bathymetry survey of the central and eastern gulf of corinth goc greece reveals the offshore fault geometry seismic stratigraphy and basin evolution of one of earths most active continental rift systems active right stepping en echelon north dipping border faults trend ese along the southern gulf margin significantly overlapping along strike the basement offsets of three akrata derveni sithas and xylocastro are linked the faults are biplanar to listric typically intermediate angle 35 in the centre and 45 48 in the east near the surface but decreasing in dip and or intersecting a low or shallow angle 15 20 in the centre and 19 30 in the east curvi planar reflector in the basement major s dipping border faults were active along the northern margin of the central gulf early in the rift history and remain active in the western gulf and in the subsidiary gulf of lechaio but unlike the southern border faults are without major footwall uplift much of the eastern rift has a classic half graben architecture whereas the central rift has a more symmetric w or u shape the narrower and shallower western gulf that transects the 40 km thick crust of the hellenides is associated with a wider distribution of overlapping high angle normal faults that were formerly active on the peloponnesus peninsula the easternmost sector includes the subsidiary gulfs of lechaio and alkyonides with major faults and basement structures trending ne e w and nw the basement faults that control the rift architecture formed early in the rift history with little evidence other than the vrachonisida fault along the northern margin in the marine data for plan view evolution by subsequent fault linkage several have maximum offsets near one end crestal collapse graben formed where the hanging wall has pulled off the steeper onto the shallower downdip segment of the derveni fault the dominant strikes of the corinth rift faults gradually rotate from 090 120 in the basement and early rift to 090 100 in the latest rift reflecting a 10 rotation of the opening direction to the 005 presently measured by gps the sediments include a locally 1 5 km thick early rift section and a late rift section also locally 1 5 km thick that we subdivide into three sequences and correlate with seven 100 ka glacio eustatic cycles the gulf depocentre has deepened through time currently 700 mbsl as subsidence has outpaced sedimentation we measure the minimum total horizontal extension across the central and eastern gulf as varying along strike between 4 and 10 km and estimate full values of 6 11 km the rift evolution is strongly influenced by the inherited basement fabric the regional nnw structural fabric of the hellenic nappes changes orientation to ese in the parnassos terrane facilitating the focused north south extension observed offshore there the basement penetrating faults lose seismic reflectivity above the 4 14 km deep seismogenic zone multiple generations and dips of normal faults some cross cutting accommodate extension beneath the goc including low angle 15 20 interfaces in the basement nappes the thermally cool forearc setting and cross orogen structures unaccompanied by magmatism make this rift a poor analogue and unlikely precursor for metamorphic core complex formation

analysis and tectonic interpretation of gravity data over the variscides of southwest ireland the gravity data set for southwest ireland comprising 5500 stations with a spacing of about 1 3 km has been filtered using standard wavenumber domain techniques a band pass filtered map emphasizing gravity anomalies originating to a maximum depth of 3 4 km correlates well with surface geology it shows major faults and density contrasts among six lithostratigraphical units the most important being between the old red sandstone and underlying basement a low pass filtered map emphasizing gravity anomalies from a maximum depth of 10 12 km shows major negative gravity anomalies at killarney and fermoy and positive anomalies beneath the shannon estuary on the dingle peninsula and along the south coast these data suggest that caledonian basement was involved in variscan deformation and any detachment lies at mid crustal levels two north south gravity profiles are modelled along eastings 100 and 200 constrained by surface geology and published seismic refraction data on line 100 the source of the negative anomaly at killarney is modelled as either a granite within basement or a deformed devonian basin the source of the shannon positive anomaly is modelled as a large dense body within the crust whose southern limit coincides with the iapetus suture zone on line 200 the fermoy low is modelled as a laccolithic granite within basement the positive anomaly along the south coast is a consequence of mesozoic crustal thinning

moho topography under central greece and its compensation by pn time terms for the accurate location of hypocenters the example of the gulf of corinth 1995 aigion earthquake abstract in this paper we expand over the whole of central greece the moho map centered on the gulf of corinth from tomographic inversion of pmp traveltime profile data recorded by several tens of temporary stations our approach is based on pn moho refracted waves from a large regional earthquake recorded by both temporary stations and the permanent hellenic network the moho map shows the large moho depth under the hellenides belt it also highlights the shallower moho domain towards the aegean sea south and east of the corinth gulf the domain of shallow moho is limited along a ne sw prolongation ahead of the north anatolian fault from the north aegean trough to the western tip of the gulf of corinth towards the gulf of patras the pn time terms provide corrections for the permanent stations that can be used together with the 1d velocity depth model for a first order compensation of lateral heterogeneity and contribute to the accurate and fast location of earthquake hypocenters as a test we relocated the 1995 aigion earthquake in this way using only the sparse data of the permanent stations hypocentral coordinates then shift close to those derived by a dedicated dense array deployed after the earthquake implying improvement of the routine location

river profiles along the himalayan arc as indicators of active tectonics abstract longitudinal profiles along sixteen major transverse himalayan rivers add important constraints to models of active continental subduction and its evolution these profiles are characterized by a zone of relatively high gradient that cannot be associated with differential resistence to erosion in all cases the base of the zone of increased gradients correlates with 1 the topographic front between the lesser and high himalayas 2 the narrow belt of intermediate magnitude thrust earthquakes 3 the main central thrust zone mct these features define a small circle in the central portion of the himalayan arc these correlations suggest that the discontinuity in the river profiles and the other features are controlled by a major tectonic boundary between the rising high himalayas and the lesser himalayas no sharp increases in gradient are observed near the main boundary thrust mbt except on a few rivers such as the jhelum or kundar where the mbt lies close to both the mct and the seismic belt thus it is unlikely that the mbt is a major tectonic boundary the diversion of river courses along the mbt and around anticlines in the sub himalayas has probably been caused by aggradation near the rosion deposition boundary upstream of uplifts in the mahabharat range and sub himalayas a parallel is drawn between the himalayas and new guinea based on the hypothesis that continent arc collision of the type occurring in northern australia preceded continent continent collision in the himalayas the present sedimentary tectonic phase in new guinea resembles the subathu paleocene eocene phase in the himalayas incipient counterparts of the major himalayan structures including the mct and the mbt are recognized in new guinea the drainage patterns in the himalayas and in new guinea bear a similar relation to major structures this suggests that 1 the tectonic evolution of the himalayas has been rather uniform since early stages of collision and 2 the himalayan drainage was also formed at these early stages and is therefore antecedent to the rise of the high himalayas

active faulting at the western tip of the gulf of corinth greece from high resolution seismic data abstract the gulf of corinth is one of the fastest spreading intra continental rifts on earth gps data indicate that the rift is currently opening in a nne ssw direction with a rate of extension reaching up to 16 mm yr 1 in its westernmost part although the rest of the offshore rift has been well studied the western tip of the rift is still poorly explored we present an accurate map of submarine faults in this area based on two high resolution seismic reflection surveys single channel sparker in the eastern part of the studied area the sedimentary infill is affected by the known north eratini south eratini and west channel faults further to the west the seafloor is mostly flat and is bounded to the north by the normal south dipping trizonia fault to the north the shallower part of the gulf shows to the east a diffuse pattern of normal and strike slip deformation which is replaced to the west by a 7 5 km long se striking strike slip fault zone called the managouli fault zone to the westernmost tip of the gulf in the nafpaktos basin two fault sets with different strikes are encountered the one with a ne sw strike exhibits a clear strike slip component the western tip of the gulf of corinth is the only part of the corinth rift where convincing evidence for strike slip movement has been found this fault pattern is likely related to the complex deformation occurring at the diffuse junction at the western tip of the rift between three crustal blocks continental greece peloponnese and the ionian island akarnania block

comparison of geodetic and geologic data from the wasatch region utah and implications for the spectral character of earth deformation at periods of 10 to 10 million years the wasatch fault and adjacent fault zones provide an opportunity to compare present day deformation rate estimates obtained from space geodesy with geologic displacement rates over at least four temporal windows ranging from the last millennium up to 10 myr the three easternmost gps sites of the basin and range geodetic network bargen at this latitude define a 130 km wide region spanning three major normal faults extending east west at a total rate of 2 7 0 4 mm yr with an average regional strain rate estimated to be 21 4 nstrain yr about twice the basin and range average on the wasatch fault the vertical component of the geologic displacement rate is 1 7 0 5 mm yr since 6 ka 0 6 mm yr since 130 ka and 0 5 0 7 mm yr since 10 ma however it appears likely that at the longest timescale rates slowed over time from 1 0 to 1 4 mm yr between 10 and 6 ma to 0 2 to 0 3 mm yr since 6 ma the cumulative vertical displacement record across all three faults also shows time variable strain release ranging from 2 to 4 mm yr since 10 ka to 1 mm yr averaged over the past 130 kyr conventional earthquake recurrence models reid type behavior would require an accordingly large variation in strain accumulation or loading rate on a 10 kyr timescale for which there appears to be no obvious geophysical explanation alternatively seismic strain release given a wide range of plausible constitutive behaviors for frictional sliding may be clustered on the 10 kyr timescale resulting in the high holocene rates with comparatively low uniform strain accumulation rates on the 100 kyr timescale wallace type behavior the latter alternative combined with observations at the million year timescale and the likelihood of a significant contribution of postseismic transients implies maxima of spectral amplitude in the velocity field at periods of 10 myr variations in tectonic loading 10 kyr clustered strain release and of 100 years postseismic transients if so measurements of strain accumulation and strain release may be strongly timescale dependent for any given fault system

controls on knickpoint migration in a drainage network of the moderately uplifted ardennes plateau western europe much research has been devoted to the development of numerical models of river incision in settings where bedrock channel erosion prevails numerous studies have used field data to calibrate the widely acknowledged stream power model of incision and to discuss the impact of variables that do not appear explicitly in the model s simplest form however most studies have been conducted in areas of active tectonics displaying a clear geomorphic response to the tectonic signal here we analyze the traces left in the drainage network 0 7 my after the ardennes region western europe underwent a moderate 100 150 m uplift we identify a set of knickpoints that have traveled far upstream in the ourthe catchment following this tectonic perturbation using a misfit function based on time residuals our best fit of the stream power model parameters yields m 0 75 and k 4 63 10 8 m 0 5y 1 linear regression of the model time residuals against quantitative expressions of bedrock resistance to erosion shows that this variable does not correlate significantly with the residuals by contrast proxies for position in the drainage system prove to be able to explain 76 of the residual variance high time residuals correlate with knickpoint position in small tributaries located in the downstream part of the ourthe catchment where some threshold was reached very early in the catchment s incision history removing the knickpoints stopped at such thresholds from the data set we calculate an improved m 0 68 and derive a scaling exponent of channel width against drainage area of 0 32 consistent with the average value compiled by lague for steady state incising bedrock rivers copyright 2014 john wiley sons ltd

basin and river profile morphometry a new index with a high potential for relative dating of tectonic uplift abstract geomorphometry may be a powerful tool to describe the characteristics of the landscape s response to tectonic signals but the meaning of morphometric indices is often obscured by the interplay between the many variables controlling the geomorphological evolution moreover although the so called hypsometric integral refers to the basin scale most indices are generally derived from the river long profiles and thus focus mainly on the short term response of a drainage network to base level change providing limited information in regions of older and or moderate uplift here using the rhenish shield western europe an area of moderate quaternary uplift as a test case i attempt to build an index yielding a comprehensive view of the stage attained by the landscape s response and indirectly an evaluation of the timing of the triggering base level change this index called r 1 is a ratio of differences between the three integrals linked respectively to the classical basin s hypsometric curve to the main river s long profile and at the intermediate level to a drainage network s hypsometric curve while its ratio form minimizes the lithological effect on r 1 this index is strongly correlated with basin size regional correlation coefficients are in the range 0 88 0 93 reflecting the way an erosion wave propagates from the outlet of a basin toward its headwaters therefore it is not directly usable as a proxy for relative uplift age however one can show that the relation between r 1 and basin size is theoretically expected to change with time following uplift the slope s r of the linear relation r 1 f ln a first increases rapidly but briefly then it gradually diminishes over several million years this is fully confirmed by the analysis of r 1 and s r in the study area once its initial increase is completed assumedly in a few ten thousand years s r appears to be a reliable indicator of relative uplift or any other cause of base level lowering age

a chronology of foreland deformation ultra violet laser 40ar 39ar dating of syn late orogenic intrusions from the variscides of southwest ireland abstract the upper palaeozoic sedimentary rocks of the munster and south munster basins southern ireland lie within the rhenohercynian zone of the european variscan orogeny this foreland region accommodated shortening during the asturian phase of variscan deformation at the end of the carboniferous by the development of kilometre scale and lower order folding high angle reverse faulting and regional fabric development at the southwestern extremity of the belt lies the black ball white ball heads area of the beara peninsula where high level igneous intrusions locally exhibit a close relationship with both the ductile and late brittle phases of variscan deformation 40 ar 39 ar ultra violet laser analysis of phlogopite crystals from these intrusions principally trachytic dykes has yielded ages that when combined with structural field relationships help to constrain the timing of variscan deformation in southern ireland these ages include 314 44 1 00 ma for a penetratively deformed lamprophric pipe on black ball head 301 98 1 47 298 08 0 61 ma for dyke material associated with later stage brittle deformation and a date of 296 88 0 60 ma for an undeformed post orogenic dyke on white ball head

lateral propagation of the surface trace of the south alkyonides normal fault segment central greece its impact on models of fault growth and displacement length relationships abstract the evolution of deformed marine terraces and drainage systems have been examined in order to investigate the growth and lateral propagation of an active normal fault geological mapping has revealed three distinct raised marine terraces in the immediate footwall of the western end of the active south alkyonides fault segment safs gulf of corinth central greece we correlate these terraces with sea level highstands at 125 240 and 330 ka using elevation estimates of the inner edges of the terraces we show that uplift rates decrease towards the perachora fault segment boundary at the western end of the safs analysis of terraces and drainage wind gaps in the footwall of the fault shows that the surface trace of the safs propagated westwards at a rate of 12 1 16 7 mm y over at least the last 330 ka whilst the surface trace length has increased analysis of the geometry and kinematics of fault slip suggests that fault length at depth has remained fixed implying progressive increase in the values for the displacement length ratio if this is correct growth is not self similar and fault length has been established early in the evolution of the system i e before 330 ka

recent history of the eastern eliki fault gulf of corinth geomorphology palaeoseismology and impact on palaeoenvironments summary the eliki fault system dominates the landscape of the southwestern shore of the gulf of corinth where rapid extension rates result in frequent earthquakes these include an event in 373 bc that destroyed the city of helike and a recent event in 1861 uplifted late pleistocene marine terraces within the eastern eliki fault footwall suggest revised slip rates of 3 5 mm yr 1 contributing 2 3 mm yr 1 geological extension to a net geodetic extension of 10 15 mm yr 1 across this part of the rift palaeoseismological trenches indicate two and possibly three earthquakes on the eastern eliki fault in the last 1500 yr including the 1861 earthquake one trench eet1a reveals displaced stratigraphy but the main fault trace is thought to lie further south beneath the old national road trench eet1a reveals liquefied sediments associated with an event between ad 1460 and the present which may be the 1861 event and displacement during a second event in the interval ad 440 1410 or ad 1270 1640 a third earlier event identified by liquefaction occurred on the eliki or a nearby fault in ad 440 1410 using the 1861 and second event most likely ad 1270 1640 the interval between recent earthquakes is 200 600 yr suitable trench sites are rare in this region compounded by human activity over several thousand years borehole and trench data indicate that the kerynites river frequently flowed eastwards along the eastern eliki fault during the last 20 40 kyr possibly influenced by tectonic tilting from the eliki and aigion fault systems and natural channel avulsion

morphotectonic control on drainage network evolution in the perachora peninsula greece abstract in tectonically active areas drainage systems are often influenced by the type geometry and recent activity of regional and local faults in the perachora peninsula eastern gulf of corinth greece most drainage networks are influenced by neotectonic processes and eustasy two major east west trending fluvial systems perachora and pissia in the southwestern part of the peninsula are affected by faults of similar orientation detailed geomorphological mapping was performed focusing on knickpoints gorges planation and depositional surfaces alluvial fans and talus cones longitudinal river profiles and hypsometric curves of their basins were constructed utilizing gis technology the two drainage systems exhibit opposite network asymmetries the pissia network is well developed south of the main channel while the perachora extends to the north the analysis of the longitudinal profiles of the main stream channels denotes that they exhibit different evolutionary trends the pissia stream has a transverse drainage crossing the active loutraki fault while the perachora stream has a parallel evolution as it has the same orientation as the loutraki fault the drainage system of pissia is much older than the perachora as a large part of the latter was underwater in late pleistocene times the combination of eustacy and vertical tectonic movements has led to the development of four marine terraces corresponding to previous high sea level stands during oxygen isotope stages ois 5e 7e 9c and 11c following the analysis of the longitudinal profiles and the hypsometric curves two depositional surfaces were verified at perachora village the first surface at 280 360 m and the second one between 120 and 160 m are probably related to marine terraces 11c and 7e respectively the development of the present drainage systems of perachora and pissia in the late quaternary depends mostly on the fault tectonism of the two main offshore fault systems of xylokastro and loutraki resulting in the uplift of marine terraces to heights of more than 300 m but also due to the inland faults pissia and alepochori which created depositional surfaces and knickpoints sea level changes have played a secondary role in the development of the drainage systems

accretionary history and crustal evolution of the variscan belt in western europe abstract the variscan belt of western europe is part of a large intra paleozoic belt extending on both sides of the atlantic from the ouachitas in the us and the mauritanides in west africa to the bohemian massif in czechoslovakia and poland the belt was constructed between 500 and 250 ma as a result of convergence and collision between two main continents laurentia baltica and africa after the closure of various oceanic basins iapetus rheic and galicia massif central now recorded as discrete in part cryptic sutures which form the roots of large crystalline nappes in which are found dismembered remnants of oceanic crust and mantle the accretionary history of the variscan belt in western europe is related to the progressive closure of probably two oceanic basins the rheic in the north and another the galicia massif central in the south by respectively southward and northward intraoceanic subduction followed by obduction and intracontinental lithospheric subduction the result is a broad 700 800 km fan like divergent belt which must be considered as a classical obduction collision orogen with a long intracontinental history of about 100 150 ma its arcuate shape is probably due to the northwestward impingement of a promontory of the african continent into laurentia baltica

a great deepening chronology of rift climax corinth rift greece continental rift deposits contain critical clues concerning the evolution of extensional tectonics yet such evidence is often obscure due to poor geochronology burial by younger deposits or later tectonic overprinting we revisit corinth rift development which began as distributed extension created synrift depocenters with rivers flowing into shallow 50 m lakes subsequent focused deformation initiated a great deepening event evidenced by fan deltas prograding into 300 600 m deep water a chronology is provided for the event from 40ar 39ar dating of the xylocastro ash by single crystal co2 laser fusion yielding a precise age of 2 550 0 007 ma 1 full error propagation sedimentological data indicate that the ash bearing sediments were deposited as turbidites and hemipelagites on sublacustrine fans fed from the mavro fan delta at the faulted south central rift margin the ash age and turbidite provenance data enable stratigraphic constraints for an estimate of central rift climax occurring between 3 2 and 3 0 ma this is some 0 8 1 0 m y earlier than radioisotopic and magnetostratigraphic constrained estimates for the eastern corinth rift central rift climax was probably triggered by initial counterclockwise rotation of the peloponnesus block with respect to central greece the rotation pole of this block subsequently migrated to its present position as rift climax moved eastward in an unzipping action with the southern active margin also migrating northward these events are unlikely to be due to local or regional fault kinematics but rather to the consequences of deep seated interactions between the rapidly southward moving aegean continental forearc and the slowly northward subducting african oceanic plate a possible scenario involves forearc pushback with decollement on a low angle subducting lower plate this causes acceleration and counterclockwise rotation of peloponnesus with respect to central greece and strain localization across the boundary the corinth rift

landscape response to tectonic forcing digital elevation model analysis of stream profiles in the mendocino triple junction region northern california the topographic evolution of orogens is fundamentally dictated by rates and patterns of bedrock channel incision quantitative field assessments of process based laws are needed to accurately describe landscape uplift and denudation in response to tectonics and climate we evaluate and calibrate the shear stress or similar unit stream power bedrock incision model by studying stream profiles in a tectonically active mountain range previous work on emergent marine terraces in the mendocino triple junction region of northern california provides spatial and temporal control on rock uplift rates digital elevation models and field data are used to quantify differences in landscape morphology associated with along strike northwest to southeast changes in tectonic and climatic conditions analysis of longitudinal profiles supports the hypothesis that the study area channels are in equilibrium with current uplift and climatic conditions consistent with theoretical calculations of system response time based on the shear stress model within uncertainty the profile concavity of the trunk streams is constant throughout the study area 0 43 as predicted by the model channel steepness correlates with uplift rate these data help constrain the two key unknown model parameters the coefficient of erosion k and the exponent associated with channel gradient n this analysis shows that k cannot be treated as a constant throughout the study area despite generally homogeneous substrate properties for a reasonable range of slope exponent values n best fit values of k are positively correlated with uplift rate this correlation has important implications for landscape evolution models and likely reflects dynamic adjustment of k to tectonic changes due to variations in orographic precipitation and perhaps channel width sediment load and frequency of debris flows the apparent variation in k makes a unique value of n impossible to constrain with present data

new 234u 230th coral dates from the western gulf of corinth implications for extensional tectonics we derive rates of uplift of 0 7 0 8 mm yr for the western end of the gulf of corinth greece using geomorphic paleaoshoreline modeling we calibrate the modeling with new 234u 230th dates on the coral cladocora caespitosa collected from raised marine terraces uplifted in the footwall of the active psathopyrgos fault the only major active normal fault reported on published maps controlling the downthrown rio straits at the western end of the gulf of corinth in this area of high 15 22 mm yr extension rates measured with gps the ratio of uplift rate to extensional velocity is 0 025 0 035 much lower than values of 0 15 0 25 found further east in the gulf these low values imply that if gps extension rates are correct then mechanical kinematic models developed for the eastern and central gulf may not be applicable to the western gulf

kinematic retro modelling of a cross section through a thrust and fold belt the western irish namurian basin the western irish namurian basin winb developed into a fold and thrust belt at the front of the northward propagating variscan orogenic wedge part of this basin is well exposed along the coast of county clare ireland from a detailed study that used an integrated gps mapping approach we produced a c 50 km long balanced cross section parallel to the tectonic transport vector we sequentially decompacted and retro deformed the namurian strata in 7 stages to evaluate the palinspastic situation of the basin and the amount of shortening by using passive markers in the model and a highly detailed timescale we were able to determine that shortening of the winb from the onset of central clare group sedimentation was 7 44 or 4 07 km of which shortening due to folding accounts for c 2 64 c 1 37 km and therefore c 4 80 c 2 69 km was solely because of thrusting the rate of horizontal shortening ranges from 1 34 mm a 1 this is within typical orogenic values

wave train model for knickpoint migration rivers respond to a drop in their base level by incising the topography the upstream propagation of an incision as usually depicted by a knickpoint migration is thought to depend on several parameters such as the drainage area lithology and the amplitude of the base level drop we first investigate the case of the messinian salinity crisis that was characterized by the extreme base level fall 1500 m of the mediterranean sea at the end of the miocene the response of drainage areas of three orders of magnitude 103 to 106 km2 highlights the dominant role of the drainage area with a square root relationship in controlling the knickpoint migration after a base level fall a compilation of mean rates of knickpoint propagation for time durations ranging from 102 to 107 years displays a similar relationship indicating that successive wave trains of knickpoint can migrate in a river first wave trains linked to the release of the alluvial cover and then wave trains related to the bedrock incision which correspond to the real time response of rivers wave trains with very low retreat rates long lived knickpoints 1 my rather correspond to the response time of regional landscape

a new structural model for the sw irish variscides the variscan front of the nw european rhenohercynian abstract the variscan front of nw europe has been drawn in the past from belgium across southern england and southern wales towards southern ireland but the term variscan front is not well defined and means different things to different people a tectonic front should represent the outcrop of a frontal thrust or the tip line of the basal detachment in fact such a tectonic front cannot be traced along the so called variscan front in ireland field based studies of the western part of the irish variscides show that the fold and thrust belt continues north of the so called variscan front but deformation decreases gradually therefore we suggest supported by seismic data a detachment which ends as a blind thrust far to the north the tip line of this basal detachment represents the true tectonic front of the variscides in sw ireland shear indicators show locally a dextral shear component near major faults and 3d microstructural strain analyses show varying x axes and oblate deformation indicating transpression during the tectonic evolution of the western irish variscides therefore a thin skinned model associated with dextral shearing and transpression in the hanging wall of the basal detachment is suggested the evolution of the variscan fold and thrust belt in nw europe is related to the west european indentation model but also to pre variscan basement structures as the leinster wales and london brabant massifs finally an attempt is made to outline the variscan front along the entire nw european rhenohercynian fold and thrust belt ftb

fold cleavage relationships as indicator for late variscan sinistral transpression at the rheno hercynian saxo thuringian boundary zone central european variscides abstract the boundary between the rheno hercynian and the saxo thuringian zones of the european variscides is characterized by a ne sw striking late orogenic fold and thrust belt affecting the intervening rheic suture classical models used the first order strike of this zone as an indicator for perpendicular plate convergence i e nw se we present structural data from both sides of the suture focusing on fold cleavage relationships the statistical analysis reveals an orientation maximum of the youngest cleavage that deviates from the strike of the fold and thrust belt by c 22 the presence of clockwise transection of the folds by the cleavage up to 16 indicates pervasive sinistral transpression three types of fold cleavage relationships are observed ne trending folds i with or ii without a transecting cleavage and iii non transected ene trending folds we explain the occurrence of different fold cleavage types by strain partitioning due to nnw convergence obliquely to pre existent ne trending mechanical anisotropies in terms of plate tectonics we propose that the classical boundary of the rheno hercynian and the saxo thuringian zone represents an initial transform plate boundary that was finally affected by sinistral transpression

hypsometric analysis to identify spatially variable glacial erosion 1 relatively little research has been undertaken on the use of digital elevation models to recognize the spatially variable glacial imprint of a landscape using theoretical topographies and a landscape evolution model we investigate to what extent the hypsometric analysis of digital elevation models may be used to recognize the glacial signature of mountain ranges a new morphometric parameter which we term the hypsokyrtome from the greek ipsos elevation kyrtoma curvature is derived from the gradient of the hypsometric curve the efficacy of the hypsometric integral and hypsokyrtome is tested through the study of the ben ohau range new zealand whose glacial imprint has been described previously with a numerical model we further test the geomorphic parameters in describing the morphologies of regions subject to diverse climatic and tectonic conditions the hypsokyrtome is highly sensitive to glacial erosion and the maps produced provide insights into the spatial distribution of glacial erosion we use srtm data and focus on two alternative geomorphic settings the european alps and the apennines the former has been affected by both fluvial and glacial erosion while the latter mainly exhibits a fluvially dominated morphology the correlation between elevations with increased glacial erosion and last glacial maximum lgm equilibrium line altitudes elas suggests the prevalence of a glacial buzz saw in the alps indicating that climate may put a limit on alpine topography

initiation and recession of the fluvial knickpoints of the island of tahiti french polynesia abstract in this paper we study the origin and evolution of the 42 knickpoints spanning the island of tahiti a large extinct shield volcano in the south pacific ocean french polynesia by combining dem analysis and numerical modeling these knickpoints are located along rivers 107 in total with a total length exceeding 6 km and with a total drainage of 3 km2 the knickpoint locations do not correspond to lithology tributary confluence or uplift we argue that these knickpoints have been initiated by a sudden sea level drop of 135 m 20 ky ago and that the littoral cliffs circling two thirds of tahiti are the result of marine erosion that took place 7 ky ago from a stand level that was 5 m higher than now the head to toe height of the knickpoints increases with respect to the knickpoints distance from the ocean the major process controlling the knickpoints is plunge pool incision and the n 2 stream power model works well for modeling the profile form the mean retreat rate of the knickpoints corresponds very well with a drainage area dependant model with velocities ranging from 0 17 to 1 2 m y

high sediment yields and cool wet winters test of last glacial paleoclimates in the northern mediterranean opposing models have been proposed for last glacial paleoclimates in the mediterranean area to discriminate between the alternative models we calculate variations in sediment yield within a high resolution stratigraphic framework developed for the alkyonides basin central greece latest quaternary highstand deposits are distinguised from lowstand lake corinth deposits on the basis of seismic reflection data and micropaleontological and palynological analyses of drop cores after depth conversion and calculation of solid sediment masses in successive time slices sediment discharge rates during the last glacial lowstand interval ca 70 12 ka are shown to have exceeded discharge rates during the preceeding interglacial highstand interval ca 128 70 ka by 60 implying enhanced seasonality during the glacial period with cool dry summer and wet winter conditions in the region sediment yield calculations can thus provide an empirical test of paleoclimate models and offer input to sequence stratigraphic models

structural evolution of the irish variscides the effects of the variscan orogeny on the upper palaeozoic succession are recognizable throughout central and southern ireland the deformation can be zoned using structural styles and trends which illustrate a northward decrease in deformation intensity coupled with increasing control by pre variscan structures in the basement the most intense deformation occurs to the south of the dingle dungarvan line where shortening approaches 50 as a result of layer parallel shortening followed by buckling and finally thrusting the deformation is considered to have developed above a shallow dipping sole thrust which has been located offshore by the swat seismic reflection profiles cross faults which are common throughout the orogen resulted from n s shear couples this is consistent with their origin as accommodation structures due to differential shortening along strike the original shape of the munster basin has exerted a control on the distribution and overall facing of the major structures the sole thrust extends to the north of the dingle dungarvan line and the structural zonation of the orogen is due to variations in the stratigraphic level of this thrust the leinster massif is considered to be essentially autochthonous slip on the sole thrust decays towards the massif which acted as a rigid passive block and was partially responsible for the arcuate trend of the orogen

along strike variations of morphotectonic features in the western foothills of taiwan tectonic implications based on stream gradient and hypsometric analysis abstract the taiwan mountain belt provides a key example for analyzing the relation between morphology and tectonics in an active compressional environment there is a striking geometrical relationship between the location of salients and reentrants of the mountain belt and the presence of major crustal inhomogeneities such as structural highs in the foreland basin major along strike variations of structural styles occur in range front rock units of the fold thrust belt stream gradient and hypsometric analysis has been carried out to highlight the along strike variations of morphotectonic features and to illustrate the relative activities in different tectonic regimes of the western foothills the normalized stream length gradient index sl index and the hack profile are two of the stream gradient indices that effectively reflect the tectonic uplift in a region de trending and residual analysis of the hypsometric integral hi eliminates the spatial dependency of small drainage basins and the residual hypsometric integral corresponds to differential uplift activity integration of stream gradient indices and hypsometry provides more robust tectonic interpretation five morphotectonic provinces have been identified in the western foothills based on stream gradient indices and hypsometry each province is bounded by a series of n140 e trending transfer fault zones either inherited from the eurasian passive margin and or newly formed in the sedimentary cover in response to the presence of basement highs within the foreland basin the peikang and kuanyin highs the morphotectonic features as well as deformation styles vary within each province a high uplift but low shortening rate typifies the crustal deformation style in the transpressional regime north of the peikang basement high on the contrary a low uplift but high shortening rate characterizes the crustal deformation style in the transtensional regime south of the peikang basement high the higher geomorphic indices suggest that greater tectonic activity occurs in central than in southwestern taiwan this inference is also supported by the coseismic deformation of the 1999 chi chi earthquake

patterns of quaternary uplift of the corinth rift southern border n peloponnese greece revealed by fluvial landscape morphometry abstract the rift of corinth is a world class example of young active rifting and as such is an ideal natural laboratory of continental extension however though much investigated for two decades several aspects of the mechanisms at work are still poorly understood the aim of this paper is a detailed morphometric study of the fluvial landscape response to the tectonic uplift of the rift southern shoulder in order to reconstruct the rift s quaternary evolution with special attention to timing location and intensity of uplift episodes based on the use of a large set of catchment and long profile metrics complemented by the new r sr integrative approach of the regional drainage network we identified three distinct episodes of uplift of the northern peloponnese coastal tract of which the intermediate one dated around 0 35 0 4 ma is only recorded in the topography of the central part of the rift shoulder and the youngest one appears to have propagated from east to west over the last 10 20 ka while net uplift remained minimum in the eastern part of the study area during the whole quaternary it shows a clear maximum in the central part of the rift shoulder since 0 4 ma and an eastward shift of this maximum in recent times maximum uplift rates calculated from the morphometric data are of 1 05 and 2 5 mm year 1 for the mid middle pleistocene and holocene uplift episodes respectively the morphometric evidence reveals an onshore uplift history remarkably consistent with the rift evolution reconstructed from other data sets in the long term it shows a stable pattern of maximum activity in the central part of the rift confirming previous conclusions about the absence of rift propagation in the short term it sheds light on a possible e w migration of the zone of recent uplift suggesting that in the near future fault activity and seismic hazard might concentrate in the heliki aegion area at the western tip of this uplift wave

westward propagation of the north anatolian fault into the northern aegean timing and kinematics we present new evidence for the propagation processes of the north anatolian fault folding in the dardanelles straits region allows us to document the timing of the deformation preceding and the finite displacement after the passage of the propagating tip of the fault the accuracy of the observations is due to interplay between deformation and the sea level changes in the mediterranean the well known messinian regression followed by the pliocene transgression the long term kinematics around the sea of marmara pull apart total displacement of about 85 km over the past 5 m y is similar to the present day kinematics deduced from space geodesy at a larger scale westward propagation of the north anatolian fault over nearly 2000 km in the past 10 m y appears to be associated with strain recovery suggesting that the continental lithosphere retains long term elasticity

rates of uplift investigated through 230th dating in the gulf of corinth greece abstract the sr u and th isotope compositions of fourteen coral samples from raised terraces on the south side of the gulf of corinth greece have been analysed by high precision mass spectrometry 234u 230th ages of pure coral aragonite together with 87sr 86sr determinations provide the basis for an investigation of tectonic uplift rates in the w aegean over the last 350 ka the corinth basin is a continental fault bounded depression formed by crustal extension northeast of subduction along the hellenic trench and in the vicinity of the aegean volcanic arc the sr isotope composition of present day seawater in the gulf of corinth is indistinguishable from that in the north atlantic but this was not the case during earlier high stands 120 190 and 240 ka ago when 87sr 86sr ratios as estimated from the corals were apparently significantly lower than the ratios of their open ocean counterparts although the cause of the earlier discrepancy between the two reservoirs is unknown it is likely to result from one of two processes either circulation between the gulf of corinth and the open ocean may have been restricted at certain earlier highstands or the lower sr isotope compositions could be the result of diagenetic effects the latter hypothesis is favoured by large variations in the initial 234u 238u ratio of the corals by their unusually high th contents and by the observation that the underlying massive miocene carbonate is severely altered the ages of the corals as determined by mass spectrometry ranges between 70 2 and 385 5 ka for samples from terraces at elevations of 7 to 65 m above present sea level a mean uplift rate for this area of 0 3 mm yr over the last 350 ka has been estimated by combining the coral ages with terrace heights allowing for changes in sea level during this period the uplift here is probably caused by footwall uplift adjacent to large normal faults and put constraints on likely fault slip rates extension rates and the timescales of earthquake recurrence

finite strain and strain variation analysis in the sheeprock thrust sheet an internal thrust sheet in the provo salient of the sevier fold and thrust belt central utah abstract the sheeprock thrust sheet in west central utah is an internal thrust sheet in the provo salient of the sevier fold and thrust belt we have measured finite strain in quartzites the dominant lithology sampled along a square grid within the thrust sheet using the modified normalized fry method mcnaught m a 1994 modifying the normalized fry method for aggregates of non elliptical grains journal of structural geology16 493 503 the x y and x z axial ratios from unsampled locations within the sample area were estimated using the spatial statistics approach the strain ellipsoids exhibit a variable three dimensional orientation pattern resulting from modification of the initial layer parallel shortening lps strain ellipsoid by fault parallel shear in conjunction with vertical flattening and or horizontal stretching indicating that the thrust sheet did not undergo plane strain deformation in the transport plane this suggests that the plane strain assumption used in drawing restorable balanced cross sections breaks down for internal thrust sheets with more than one penetrative strain producing deformation event the x z strain axial ratios decrease away from the thrust towards the middle of the sheet the x y strain axial ratios from interpolated image diagrams indicate transport parallel stretching at the front end of the sheet and strike parallel stretching at the back end of the sheet the footwall and hanging wall finite strain patterns are similar indicating that most of the strain in the sheeprock thrust sheet developed early in the deformation history of the thrust sheet before and perhaps during the growth of a large fault propagation fold pair

alternating marine and lacustrine sedimentation during late quaternary in the gulf of corinth rift basin central greece abstract the gulf of corinth in central greece has a maximum depth of about 900 m and is separated from the open sea by the rion strait with a sill depth of 62 m marked by an extensive submarine terrace during eustatic sea level lowstands the gulf of corinth was a lake under lacustrine conditions stratified sediments accumulated in the deep water basins and turbid underflows from rivers eroded the basin slopes as the sea level rose marine waters flooded the gulf and deltas prograded across the shelves in shallow water areas two key reflectors termed z and x are terrace surfaces commonly erosional which mark the base of the overlying deltaic sequences in deep water basins z and x mark the top of the acoustically stratified sediments interpreted as lacustrine turbidites reflectors y and w mark the base of these stratified intervals and overlie acoustically transparent sections similar to the holocene section the last lacustrine conditions in the gulf z to y were during isotopic stage 2 and terminated about 12 000 yr ago age estimates based on sedimentation rates suggest that the x to w interval corresponds to the stage 4 lowstand of sea level in the western gulf of corinth shoreline transgressive surfaces corresponding to minor transgressions in stage 5 and to major transgression at the end of stage 6 are recognised this seismic stratigraphy permits a detailed interpretation of the history of the gulf of corinth in the past hundred thousand years it also provides a general model for sedimentation in rift basins in which marine and lacustrine sediments alternate

knickpoint recession rate and catchment area the case of uplifted rivers in eastern scotland knickpoint behaviour is a key to understanding both the landscape responses to a base level fall and the corresponding sediment fluxes from rejuvenated catchments and must be accommodated in numerical models of large scale landscape evolution knickpoint recession in streams draining to glacio isostatically uplifted shorelines in eastern scotland is used to assess whether knickpoint recession is a function of discharge here represented by its surrogate catchment area knickpoints are identified using ds plots log slope versus log downstream distance a statistically significant power relationship is found between distance of headward recession and catchment area such knickpoint recession data may be used to determine the values of m and n in the stream power law e kamsn the data have too many uncertainties however to judge definitively whether they are consistent with m n 1 bedrock erosion is proportional to stream power and kps should be maintained and propagate headwards or m 0 3 n 0 7 bedrock incision is proportional to shear stress and kps do not propagate but degrade in place by rotation or replacement nonetheless the e scotland m and n values point to the dominance of catchment area discharge in determining knickpoint retreat rates and are therefore more consistent with the stream power law formulation in which bedrock erosion is proportional to stream power copyright 2005 john wiley sons ltd

spatial analysis of stream power using gis slk anomaly maps the stream length gradient index sl shows the variation in stream power along river reaches this index is very sensitive to changes in channel slope thus allowing the evaluation of recent tectonic activity and or rock resistance nevertheless the comparison of sl values from rivers of different length is biased due to the manner in which the index is formulated thus making correlations of sl anomalies along different rivers difficult therefore when undertaking a comparison of sl values of rivers of different lengths a normalization factor must be used the graded river gradient k has already been used in some studies to normalize the sl index in this work we explore the relationships between the graded river gradient k the sl index and the stream power proposing the use of a re named slk index which enables the comparison of variable length rivers as well as the drawing of slk anomaly maps we present here a gis based procedure to generate slk maps and to identify slk anomalies in order to verify the advantages of this methodology we compared an slk map of the ne border of the granada basin with both simple river profile knickpoint identification and with an sl map the results show that the slk map supplies good results with defined anomalies and suitably reflects the main tectonic and lithological features of the study area copyright 2008 john wiley sons ltd

the structural evolution of the western irish variscides an example of obstacle tectonics abstract detailed mesostructural and strain analysis investigations across the killarney mallow fault i e the traditional variscan front in southwest ireland reveal that this structural line separates two distinct tectonic regimes north of the killarney mallow fault bulk shortening orthogonal to orogenic strike is estimated to be 12 all of which is accounted for by late stage buckling microscopic strain analysis reveals that there is only local development of a tectonic fabric south of the front bulk shortening is 40 due to combined layer parallel shortening lps buckling and faulting variscan deformation is presented as being essentially coaxial the regional finite strain pattern outlined above is thought to be primarily controlled by the combined effect of a buried basement obstacle in eastern iveragh and increased sedimentary pile thickness at the western end of the orogen

tectonic and climatic controls on knickpoint retreat rates and landscape response times 1 the rate at which transient knickpoints propagate through a landscape fundamentally controls the rate of geomorphic response to tectonic and climatic perturbation here we present knickpoint retreat rates upstream of active faults for 19 bedrock catchments in turkey and 11 bedrock catchments in italy where we have very good constraints on both the magnitude and timing of the tectonic perturbation and where climate histories are well documented we show that the knickpoints have average retreat rates of between 0 2 and 2 mm yr for catchments with drainage areas between 6 and 65 km2 and we test whether differences in rock mass strength and catchment size are sufficient to explain this range in retreat rates our analysis suggests that even accounting for these two variables knickpoint propagation velocities differ markedly and we show that channels crossing faults with higher throw rates have knickpoints that are retreating faster the dependence of knickpoint retreat velocity on throw rate is at least as important as catchment drainage area these results indicate counterintuitively that landscapes forced by large amplitude tectonic perturbations will have shorter response times than those perturbed by smaller amplitude changes the link between the knickpoint propagation velocity and throw rate is largely but not completely explained by channel narrowing in areas of high uplift rate channel steepening upstream of the active faults may explain all of the residual dependency of knickpoint retreat rate on fault throw rate but only if the slope exponent n in the standard stream power model is greater than 1 3 however we cannot rule out a role for sediment supply in driving enhanced knickpoint retreat rate in addition to the well documented channel narrowing effect finally we find that mean knickpoints retreat rates in turkey are only half of those in italy for catchments of equivalent size crossing faults with similar throw rates this difference in fluvial response time is accounted for by long term differences in the ratio of precipitation to infiltration in the two areas over the last 1 my

regional relief characteristics and denudation pattern of the western southern alps new zealand abstract the southern alps of new zealand are the topographic expression of active oblique continental convergence of the australian and pacific plates despite inferred high rates of tectonic and climatic forcing the pattern of differential uplift and erosion remains uncertain we use a 25 m dem to conduct a regional scale relief analysis of a 250 km long strip of the western southern alps wsa we present a preliminary map of regional erosion and denudation by overlaying mean basin relief a modelled stream power erosion index river incision rates historic landslide denudation rates and landslide density the interplay between strong tectonic and climatic forcing has led to relief production that locally attains 2 km in major catchments with mean values of 0 65 0 68 km interpolation between elevations of major catchment divides indicates potential removal of l01 103 km3 or a mean basin relief of 0 51 0 85 km in the larger catchments local relief and inferred river incision rates into bedrock are highest about 50 67 of the distance between the alpine fault and the main divide the mean regional relief variability is 0 5 km local relief valley cross sectional area and catchment width correlate moderately with catchment area and also reach maximum values between the range front and the divide hypsometric integrals show scale dependence and together with hypsometric curves are insufficient to clearly differentiate between glacial and fluvial dominated basins mean slope angle in the wsa 30 is lower where major longitudinal valleys and extensive ice cover occur and may be an insensitive measure of regional relief modal slope angle is strikingly uniform throughout the wsa 38 40 and may record adjustment to runoff and landsliding both and show non linear relationships with elevation which we attribute to dominant geomorphic process domains such as fluvial processes in low altitude valley trains surface runoff and frequent landsliding on montane hillslopes relief dampening by glaciers and rock fall avalanching on steep main divide slopes

end carboniferous fold thrust structures oxfordshire uk implications for the structural evolution of the late variscan foreland of south central england interpretation of commercial seismic reflection data from the west of banbury south central england has provided information on the late carboniferous structural evolution of the oxfordshire syncline end carboniferous structures are preserved in the footwall of the main basin bounding faults of the permo triassic worcester graben restoration of major pre triassic normal faults has allowed reconstruction of earlier compressional structures in contrast to the wnw ese trend of structures to the south in the variscan foreland fold thrust belt major faults and folds in oxfordshire are approximately n s trending the structures seen to deform westphalian d stephanian aged sequences on the seismic profiles are a combination of steep 30 40 dip fault bounded uplifts and less dominant thin skinned tectonics apparently showing transport to the east in the south some thin skinned structures are present and in the north cover sequences are uplifted in a narrow zone of deformation on reactivated basement faults the amount of shortening also changes along strike from c 1600 m in the south to c 950 m in the north reactivation of major basement faults with differential basement shortening accounts for the main structures localized detachment in the young and weak sediments close to the palaeo land surface explains the thin skinned structures seen on some of the seismic lines these end carboniferous structures in oxfordshire and structures in the malvern abberley hills represent the structural limits of a large n s striking intra stephanian uplift in the late variscan foreland it is suggested that the structures formed during a discrete phase of intra stephanian e w directed regional shortening prior to the final phase of movement in the variscan belt

variscan transpressive inversion in the northwestern central rhenohercynian belt of western germany abstract important orogen parallel strike slip components during the convergence of the variscan orogen of central europe have been increasingly recognized these oblique slip faults often develop from pre existing tectonic boundaries and are influenced by pre existing structural trends in the basement in this paper evidence is presented for a 3 6 km wide distributed shear zone here named the monschau shear zone in epizone metamorphic cambro ordovician and lower devonian clastic rocks of the northwestern rhenohercynian belt kinematic indicators including field observations of anomalous mullion and fold axes patterns a set of two cleavages stretching lineations and shear and kink bands microscopical observations of stretching parallel asymmetric pressure shadows of quartz on prekinematic epizone metamorphic pyrite porphyroblasts and microfabrics of phyllosilicates by x ray texture goniometry point to a sinistral tranpressive shear zone with emplacement of the southeast hangingwall under retrograde conditions coincidence of the anchizone epizone metamorphic boundary with the change along strike from penetrative shearing to distributed thrusting suggests a ductile brittle transition the monschau shear zone is situated on the backlimb of an allochthonous anticlinorium located above a basement ramp that corresponds roughly to a pre orogenic synsedimentary normal fault its continuation shows up clearly in a dekorp seismic reflection profile to a depth of 12 15 km

quaternary evolution of the corinth rift and its implications for the late cenozoic evolution of the aegean summary we present geological and morphological observations at different scales to constrain rates of faulting and the distribution of deformation in the seismically active aegean region we focus first on the 130 km long corinth rift an asymmetric graben where a flight of terraces of marine origin are uplifted we show that the edges of the terraces lie in the footwall of the normal fault bounding the corinth rift and correspond to sea level highstands of laic pleistocene age using a detailed analysis of aerial and spot imagery supported by field observations we have mapped 10 terrace platforms and strandlines ranging in elevation from 10 to 400 m over distances of 2 to 20 km from the fault the elevation of the terraces inner edges was estimated at 172 sites with an error of 5m this data set contains a precise description of the uplift and flexure of 10 different palaeohorizontal lines with respect to the present sea level to date the deformation we correlate the corinth terraces with late pleistocene oxygen isotope stages of high sea level stands and with global sea level fluctuations using a thick elastic plate model consistent with our current understanding of the earthquake cycle and a boundary element technique we reproduce the geometry of the shorelines to constrain both mechanical parameters and the slip on the fault we show that the seismogenic layer behaves over the long term as if its elastic modulus were reduced by a factor of about 1000 all the terraces are fitted for fault slip increasing in proportion to terrace age and the component of regional uplift is found to be less than 0 3 mm yr 1 the best fits give a slip rate of 11 3 mm yr 1 on the main rift bounding fault over the last 350 kyr other geological and morphologic information allows us to estimate the total age of the main fault 1 ma and to examine the mechanical evolution of the corinth rift the minimum observed sediment thickness in the gulf places an extreme check on the results of the modelling and a lower bound on slip rate of 6 7 mm yr 1 40 per cent less than estimated with modelling even this slip rate is nearly 10 times higher than for comparable features in most of the aegean and elsewhere in the world at a larger scale the spacing and asymmetry of the rift systems in the aegean suggest strain localization in the upper mantle with slow extension starting 15 myr ago or earlier the more recent 1 myr rapid phase of rifting in corinth partly reactivated this earlier phase of extension the younger faulting in corinth appears to result from its present location in the inhomogeneous stress field process zone of the south westward propagating tip of the southern branch of the north anatolian fault we extend these relations to propose a mechanical model for the late cenozoic evolution of the aegean as the arabia europe collision progressed in eastern turkey it caused anatolia to move to the west and the north anatolian fault to propagate into the aegean where the early slow extension started to be modified about 5 ma ago the process of propagation dramatically increased the activity of some but not all of the earlier rifts the model we present is compatible with tectonic observations as well as with the seismicity the palaeomagnetic rotations and the displacement field now observed with gps and slr

corinth rift margin uplift new evidence from late quaternary marine shorelines 1 new evidence for uplift of the southern margin to the corinth rift one of the world s most rapidly extending continental regions defines an area of uniform uplift separating a more rapidly uplifting western rift flank from a slowly backtilting eastern flank this major tectonic boundary coincides with geophysical evidence for a junction between flat underlying subducted oceanic plate and steep subduction we propose that trench rollback by the anatolian plate over the subducting african plate has led to differential uplift and possible migration of active faulting at the southern rift margin in the last few million years

hypsometry of glaciated landscapes hypsometry frequency distribution of elevations is often used to characterize landscape morphology traditionally in the context of the degree of uvial dissection recently the hypsometry of glaciated regions has been used to infer how rates of glacial erosion compare with tectonic uplift rates however many factors other than tectonics can also exert a major in uence on the hypsometry of a glaciated landscape resulting in a wide variety of hypsometries using examples from the eastern sierra nevada california the western sangre de cristo range colorado and the ben ohau range new zealand we demonstrate that all else being equal the hypsometries of neighbouring basins can indicate the relative degree of glacial modi cation in each a selection of drainage basins from the rocky mountains shows that the position of the equilibrium line altitude ela within the drainage basin relief is a dominant variable in determining the hypsometry of a glaciated basin this is a non linear effect once the ela falls to some critical level the glaciers scour deeply below the ela causing a noticeably different hypsometry the hypsometry of an arbitrary region encompassing many drainage basins can disguise the variation present in the hypsometries and thus landforms of the individual basins unique local circumstances such as the presence of a mountain ice eld waiho basin southern alps substantial hanging valleys avalanche creek glacier national park a narrow outlet canyon sawmill creek sierra nevada and isolated geologic structures baker creek sierra nevada can have a major impact on the hypsometry of an individual basin copyright 2004 john wiley sons ltd

comparing extension on multiple time and depth scales in the corinth rift central greece summary the young 10 15 mm yr 1 in the west we quantify total upper crust and whole crust extension on three profiles across the corinth rift whole crust extension is greater across the central rift 11 21 km than across the western part of the rift 5 13 km this correlates with the overall rift morphology which shows maximum basement subsidence sediment accumulation rift width and greatest summed late quaternary fault displacements in the central basin but contrasts with the pattern of geodetic extension rates which are greater to the west of the central basin the e w increase in strain rates interpreted from geodetic data cannot have persisted over rift history to produce the observed rift morphology we suggest the discrepancy between shortterm and long term extension patterns is related to shifts in the loci of maximum extension due to fault growth and linkage during corinth rift history and is likely a characteristic of rift development in general total upper crust and whole crust extension estimates in the western rift where extension estimates are best constrained are within error we propose that uniform pure shear extension is a viable extension mechanism in the western rift and crustal extension estimates do not require the existence of a major active n s dipping detachment fault

crustal scale balanced cross sections through the variscan fold belt germany the central egt segment abstract this paper presents crustal scale geometrically and isostatically balanced cross sections through the rhenohercynian and saxothuringian zones of the variscan fold belt of germany the cross sections are based on surface geological data and on results of the dekorp deep reflection profiles they were constructed by means of computer assisted iterative forward modelling the rhenohercynian zone corresponding to the externides of the variscan belt developed out of a some 300 km wide rifted continental margin sedimentary prism limited to the south by the narrow giessen oceanic basin during carboniferous imbrication this shelf sequence is stripped of its basement above one or more decollements and shortened by some 150 km closure of the giessen ocean and emplacement of the ophiolite bearing giessen nappe entailed a minimum additional 200 km of crustal shortening the structure of the model correlates well with the present outcrop pattern of rock units their metamorphic history the seismic and magnetotelluric architecture of the crust and its present regional distribution of thickness the deeper crust beneath the rhenish massif is probably devoid of extremely weak decollement horizons and pronounced rheological stratification in the southward adjacent saxothuringian zone nappe development involving the stacking of crustal slices during middle devonian to visean times accounts for a further 170 km of crustal shortening above an infracrustal partly blind thrust system with flat ramp geometry total crustal shortening in the analyzed profiles is estimated to be of the order of 520 km this figure is a conservative value prominent uncertainties include the unknown importance of crustal wrenching the state of strain within thrust units the distribution of strain within the lower crust and major changes in thrusting directions during the course of orogenic history

the pindos fold and thrust belt greece inversion kinematics of a passive continental margin continuous exposure in the pindos mountain chain greece and the detailed stratigraphic measurements in the area enable us to construct eight balanced cross sections across the pindos fold and thrust belt pftb and to approach quantitatively some parameters which controlled foreland evolution the 160 km wide passive continental margin of the apulian continent in greece was progressively shortened from east to west at rates of 6 mm year between the early oligocene and late eocene from the rear to the frontal part of the wedge fault bend folds duplexes and imbricates were formed while strain was partitioned into faulting 34 layer parallel shortening 23 and buckling 9 foreland subsidence and internal deformation of the orogenic wedge are strongly affected by two parameters of equal importance the thrust load of the overthrusted microcontinents and the rigidity of the underthrusted apulian passive margin changes in the thickness of the pre orogenic sediments and reactivated transform faults induced salients during the lower miocene the orogenic wedge in the peloponnese suffered additional uplift and westward gravitational gliding induced by the intracontinental subduction of the palaeozoic rift zone of the phyllite quartzite series which was reactivated and returned to the earth s surface during the hellenic orogeny

a model of the atmospheric boundary layer over the marginal ice zone a one layer primitive equation model is presented for the atmospheric boundary layer over the marginal ice zone miz the model simulates the slow rate of inversion growth and rate of warming of the boundary layer seaward of an ice edge for off ice winds observed on two cruises in the bering sea by the noaa r v surveyor the horizontal temperature gradient in the boundary layer caused by the oceanic heat flux seaward of an ice edge induced an increase in wind speed with a maximum increase of 8 at 50 km seaward of the edge at 100 km off ice a momentum balance is established between accelerative terms boundary layer baroclinity momentum entrainment synoptic scale scale pressure gradient and decelerative terms surface drag and the local pressure force resulting from inversion rise wind velocity in the boundary later over the miz during off ice winds is sensitive to changes in surface roughness when an miz is modeled as a smooth interior cd 2 10 3 and a 30 km wide rough marginal ice zone cd 3 8 10 3 with an unstable surface layer over the ocean the model shows a decrease in wind speed of 9 at the windward side of the miz and an 18 increase in wind speed from 5 km interior to the ice edge to 40 km seaward of the edge these results suggest an atmospheric mechanism for rafting at the windward side of the marginal ice zone divergence of the ice at the edge and ice band formation seaward of the edge

timing of deformation within old red sandstone lithologies from the dingle peninsula sw ireland finite strain analysis of deformed clastic sedimentary rocks below and above the acadian unconformity on the dingle peninsula sw ireland reveals that this boundary represents a significant bulk strain discontinuity the late emsian acadian event is primarily responsible for penetrative cleavage development and high strain in rocks below the unconformity and not as previously held the later variscan event which overprinted the peninsula with a weak and localized disjunctive cleavage the presence of apparent anticlockwise transecting cleavage and implied dextral closure of the dingle basin during the acadian event is compatible with northward convergence of armorica with respect to eastern avalonia

quaternary erosion induced isostatic rebound in the western alps the high elevation and deep incision of the alps have traditionally been used as an argument for recent tectonic activity that has elevated the belt and increased erosion rates normal faulting and horizontal extension however dominate current tectonic activity and isostatic compensation of thinning crust should lead not to increased but to decreased mean elevations here we test the idea that enhanced quaternary erosion of the alps and isostatic compensation of the mass removed can account for the distribution of present day geodetically measured rates of vertical movement in the western alps using geophysical relief and kuhlemann s estimated average erosion rate for the alps we quantify the spatial distribution of erosion and the volume of eroded rock respectively from these we obtain a map of rock eroded within a given time span the calculated isostatic response of the alpine lithosphere to erosional unloading for a variety of values of the flexural rigidity of the alpine lithosphere reaches a maximum of 500 m since 1 ma in the inner swiss alps and vertical movement extends across the entire belt including peri alpine basins assuming a steady erosion rate since 1 ma this rebound accounts for half of the measured vertical motion of 1 1 mm yr in the southern valais thus a significant fraction 50 of the present day vertical movement results from the isostatic response to enhanced erosion during plio quaternary time

transformation of a magmatic arc and an orogenic root during oblique collision and it s consequences for the evolution of the european variscides mid german crystalline rise the architecture of the european variscides has been subdivided by kossmat 1927 into paleogeographically coherent units which are presently interpreted as former plate fragments the mid german crystalline rise mgcr separates two fragments rhenohercynian and saxothuringian belts at the site of an inferred plate boundary and reequilibrated orogenic root the commonly favoured model interprets the mgcr as the magmatic arc on saxothuringian crust above a south dipping subduction zone in upper devonian and carboniferous times data from the mgcr the kinematic evolution of the mid european variscides and first order volume balancing suggest a reinterpretation of this unit which challenges classical views on the mgcr as well as on the subdivision of variscan architecture the mgcr is composed of two rock groups with different tectonic identity a lower carboniferous low pressure high temperature magmatic arc association on lower paleozoic basement rests tectonically on a stack of medium pressuremedium temperature rocks of inferred rhenohercynian origin the latter were tectonically accreted to the base of the overriding plate by tectonic underplating the entire process was controlled by oblique convergence this led to regional partitioning of the plate kinematic vector into contractional domains lower rhenohercynian plate and back arc area of the upper saxothuringian plate bulk heterogeneous plate margin parallel extensional domains mgcr and plate margin parallel wrench domains mgcr boundaries during this process material was continually transferred from the lower plate to the upper plate uplifted and exhumed by net crustal extension the concomitant removal of parts of the former arc and the entire orogenic root necessitates a reappraisal of variscan architecture and evolution

the terraces of corinth gerrce a detailed record of eustatic sea level variations during the last 500 000 years abstract between corinth and xylokastro 20 marine terraces reflect the interaction of the northern peloponnese uplift and the global eustatic sea level fluctuations during the last 500 000 years correlation of the terraces with oxygen isotope records in deep sea cores allowed accurate dating of these fossilized transgressive shorelines curves of altitude versus age have been plotted they show a regular decrease of the uplift rate and a frequent return of the sea level very close to the present day one not only during the interglacial periods 5 7 9 11 13 but also during glacial periods 3 1 3 3 6 8 the alternative would be to suppose very complicated and highly improbable vertical movements of the substratum to explain the regularity of the curves the rhythm of these high sea levels is around 20 30 ka since at least 330 000 years ago

deep structure of southern ireland a new geological synthesis using birps deep reflection profiling the birps deep seismic reflection data of wire west of ireland 1 1b from galway bay to the celtic sea are integrated with geological and other geophysical data to produce a synthesis of the fundamental tectonic character of the crust in and around southern ireland the iapetus suture forms a zone of north dipping reflectors which projects up between the shannon estuary and the dingle peninsula and is overlain by a late caledonian reflector with a shallow south dip across the iapetus suture zone the crust thickens southward and the lower crust becomes less reflective it is proposed that the lower palaeozoic volcano sedimentary rocks which form the leinster massif extend southwestward beneath the variscan province and at least 30 km offshore to the wire lines we argue that the weak south dipping reflectors in the upper and middle crust south of the iapetus suture represent an early caledonian fault system linked to a mid crustal detachment which formed during the south dipping subduction event recorded onshore by the ordovician volcano sedimentary successions these faults were selectively reactivated causing the predominant ene trend of younger regional tectonic features in and around southern ireland the three onshore upper palaeozoic basins close east of the wire lines we point out that the variscan front is only a map line across the british isles with no consistent tectonic character thus the south dipping reflector below the north margin of the north celtic sea basin on swat 4 generally referred to as the variscan front is correlated by us with the northern boundary of the rosslare complex thus making it the northern tectonic boundary of the caledonian basement block known as the rosslare monian terrane furthermore the north dipping south irish sea lineament on winch 4 can be correlated with the menai straits lineament and could thus be the southern boundary of this terrane the south dipping reflector on swat 2 also previously called the variscan front is correlated with the johnston benton fault system in southwest wales

morphometric age estimate of the last phase of accelerated uplift in the kazdag area biga peninsula nw turkey article i nfo while the plio quaternary uplift of the kazdag mountain range biga peninsula nw turkey is generally acknowledged little is known about its detailed timing partly because of this lack of data the cause of this uplift phase is also debated being associated either to back arc extension in the rear of the hellenic subduc tion zone to transpression along the northern edge of the west moving anatolian microplate or to extension driven by gravitational collapse here we perform a morphometric study of the fluvial landscape at the scale of the biga peninsula coupling the recently developed r sr analysis of the drainage network with concavity and steepness measures of a set of 29 rivers of all sizes while the dependence of profile concavity on basin size confirms that the landscape of the peninsula is still in a transient state the spatial distribution of profile steepness values characterized by higher values for streams flowing down from the kazdag massif shows that the latter undergoes higher uplift rates than the rest of the peninsula we obtain a sr value of 0 324 0 035 that according to the relation established by demoulin 2012 yields an age range of 0 5 1 3 ma and a most probable value of 0 8 ma for the time of the last tectonic perturbation in the region in agreement with the analysis of knickpoint migration in a subset of rivers this suggests that a pulse of uplift occurred at that time and corroborated by sparse published observations in the bayramic and canakkale depressions that the peninsula was uplifted as a whole from that time this uplift pulse might have been caused by transient compressive conditions in the anatolian plate when the eratosthenes seamount came to subduct beneath the cyprus arc around the early to mid pleistocene transition schattner 2010

the partitioning of deformation in flowing rock masses abstract most geological structures owe their development to heterogeneous and or non steady flow flow partitioning refers to the division of the instantaneous velocity field into components related to translation strain and rotation flow partitioning during the development of a geological structure usually changes with time and different histories of flow are involved at different points in the developing structure heterogeneity leads to the development of flow domains with different characteristics notably the degree of non coaxiality of deformation and different partitionings of the rotational component of flow into shear induced vorticity and spin during non steady flow there is often continual repartitioning of vorticity between the spin and shear induced components spin is an important aspect of flow leading to the development of structure this paper discusses the partitioning of deformation in a flowing rock mass coaxial flow tends to occur in isotropic materials in regions near weakly constrained boundaries non coaxial flow is favoured by suitably oriented material anisotropy and or the presence of well defined boundary constraints involving parallel relative displacements a developing anisotropy e g a crystallographic fabric in a shear zone can induce a change from coaxial to non coaxial flow other effects are related to the scale of approximation for example bulk shear induced vorticity can be locally converted to spin flow in the crust and mantle of the earth produces geological structures on all scales and involves many different types of rheological response the factors that affect flow partitioning e g spin versus non coaxial deformation are therefore of interest

pleistocene relief production in laramide mountain ranges western united states gently sloped summits and ridges collectively referred to as summit flats are abundant in many laramide ranges in the western united states the erosion rate of summit flats is 10 m m y on the basis of the concentrations of cosmogenic radionuclides because erosion rates in valleys between summit flats are an order of magnitude faster relief within these ranges is currently increasing by about 100 m m y if summit flat erosion is slower than rock uplift driven by the isostatic response to valley erosion then this relief production could result in increased summit elevations the mean depth of material eroded from a smooth surface fit to existing summit flats varies from 280 to 340 m in four laramide ranges based on geographic information system gis analyses of digital elevation models this erosion would result in a maximum of 250 300 m of rock uplift assuming airy isostasy however because the laramide ranges examined here are narrow relative to the flexural wavelength of the lithosphere erosionally driven rock uplift is limited to 50 100 m over the past several million years summit erosion would approximately offset this rock uplift therefore we conclude that summit elevations have remained essentially constant even though several hundred meters of relief has been produced on the basis of valley and summit erosion rates and the average depth of erosion we estimate that relief production in laramide ranges began at ca 3 ma we hypothesize that this relief production was climatically driven and was associated with the onset or enhancement of alpine glaciation in these ranges

revisiting the hypsometric curve as an indicator of form and process in transport limited catchment hypsometry has historically been used as an indicator of geomorphic form of catchments and landforms yet there has been little work aimed at relating hypsometry to landform process and scale this paper uses the siberia catchment evolution model to explore linkages between catchment process and hypsometry siberia generates results that are qualitatively and quantitatively similar to observed hypsometric curves for physically realistic parameters however we show that not only does the hypsometry reflect landscape runoff and erosion process but it is strongly dependent on channel network and catchment geometry we show that the width to length ratio of the catchment has a significant influence on the shape of the hypsometric curve though little on the hypsometric integral for landforms dominated by fluvial sediment transport the classic strahler mature hypsometric curve is only generated for catchments with roughly equal width and length narrow catchments show a hypsometric curve more similar to strahler s monadnock form for landscapes dominated by diffusive transport the simulated hypsometric curve is concave down everywhere this being consistent with curves reported for some example catchments in france because the transition between diffusive dominance to fluvial is scale dependent with larger catchments exhibiting greater fluvial dominance then the hypsometric curve is a scale dependent descriptor of landforms experimental results for simulated landforms from a small scale rainfall erosion simulator are reported it is shown that siberia yields satisfactory fits to the data confirming its ability to predict the form of the hypsometric curve from a simple model of geomorphic processes 1998 john wiley sons ltd

sediment and rock strength controls on river incision into bedrock recent theoretical investigations suggest that the rate of river incision into bedrock depends nonlinearly on sediment supply challenging the common assumption that incision rate is simply proportional to stream power our measurements from laboratory abrasion mills support the hypothesis that sediment promotes erosion at low supply rates by providing tools for abrasion but inhibits erosion at high supply rates by burying underlying bedrock beneath transient deposits maximum erosion rates occur at a critical level of coarse grained sediment supply where the bedrock is only partially exposed fine grained sediments provide poor abrasive tools for lowering bedrock river beds because they tend to travel in suspension experiments also reveal that rock resistance to fluvial erosion scales with the square of rock tensile strength our results suggest that spatial and temporal variations in the extent of bedrock exposure provide incising rivers with a previously unrecognized degree of freedom in adjusting to changes in rock uplift rate and climate furthermore we conclude that the grain size distribution of sediment supplied by hillslopes to the channel network is a fundamental control on bedrock channel gradients and topographic relief

a statistical framework to quantify spatial variation in channel gradients using the integral method of channel profile analysis 1 we present a statistical technique for analyzing longitudinal channel profiles our technique is based on the integral approach to channel analysis drainage area is integrated over flow distance to produce a transformed coordinate which has dimensions of length assuming that profile geometry is conditioned by the stream power law defined as e kamsn where e is erosion rate k is erodibility a is drainage area s is channel gradient and m and n are constants the slope of a transformed profile in elevation space should reflect the ratio of erosion rate to channel erodibility raised to a power 1 n this quantity is often referred to as the channel steepness and represents channel slope normalized for drainage area our technique tests all possible contiguous segments in the channel network to identify the most likely locations where channel steepness changes and also identifies the most likely m n ratio the technique identifies locations where either erodibility or erosion rates are most likely to be changing tests on a simulated landscape demonstrate that the technique can accurately retrieve both the m n ratio and the correct number and location of segments eroding at different rates where model assumptions apply tests on natural landscapes illustrate how the method can distinguish between spurious channel convexities due to incorrect selection of the m n ratio from those which are candidates for changing erodibility or erosion rates we also show how given erosion or uplift rate constraints the method can be used to constrain the slope exponent n

effective sub zechstein salt imaging using low frequency seismics results of the grundy 2003 experiment across the variscan front in the polish basin abstract the extent of the variscan deformation front is one of the key problems of the regional geology of the central european permian basin system particularly in its polish part conventional reflection seismics usually fails to produce a satisfactory image of the pre permian strata due to the shielding effect of zechstein upper permian evaporites thus we used a novel seismic acquisition technique to study the base of the permian complex and its variscan basement in the grundy 2003 experiment we combined wide angle reflection refraction measurements with the near vertical reflection seismics by the use of the constant geophone array with dense 100 m receiver spacing occupying 50 km long profile 3d design of the experiment covering 50 10 km area helped in eliminating the effect of out of plane propagations and local inhomogeneities an effective integration of traveltime tomography cdp reflection processing and prestack depth migration of wide angle reflections applied to our data allowed us to present the model in which we deduced the contact zone of the variscan overthrust structure variscan front with its molasse filled foredeep the latter might be a gas generation zone which is of a great importance for hydrocarbons prospecting in this area

dem and gis analysis of geomorphic indices for evaluating recent uplift of the northeastern margin of the tibetan plateau china the northeastern margin of the tibetan plateau is a tectonically active region consisting of a series of faults with bounded intermountain basins and is located in the transition zone between the tibetan plateau and the loess plateau active deformation that may affect the topography in this region can be quantified using geomorphic indices therefore we applied geomorphic indices such as the hypsometric integral and the stream length gradient index to infer neo tectonics in the northeastern margin of the tibetan plateau different time scaled geodetic leveling data and river incision rates were also integrated into the investigation the results show that the hypsometric integrals are not significantly affected by lithology but spatially correspond to the hanging walls of thrust faults the hypsometric integrals are also positively correlated with the leveling data although the stream length gradient index is influenced by lithology its most pronounced anomalies of the stream length gradient are associated with the thrust faults consequently the uplift in the northeast margin of the tibetan plateau appeared to be concentrated along the hanging walls of the thrust faults

a deep seismic reflection transect across the irish caledonides new reflection profiles recorded to 18s c 60km along a 600 km north south transect west of ireland wire lines provide a cross section of the irish caledonides from lewisian basement in the north to the variscan fold and thrust belt in the south and constrain the offshore extrapolations of major caledonide structures we interpret the profiles as showing the great glen fault and associated ne trending strike slip faults as near vertical structures which cut the whole crust and the uppermost mantle beneath the surface trace of the fair head clew bay line we image a north dipping zone which soles into horizontal layers just above the reflection moho the north dipping zone separates south dipping reflections above and to the north from north dipping reflections below and to the south from the fair head clew bay line as far south as the iapetus suture the lower crust contains north dipping packages of reflectors possibly related to acadian accretionary underplating the iapetus suture zone can be identified as a zone more than 50 km wide dipping north at 30 from 5 km depth offshore dingle peninsula to sole into the moho at c 30 km depth west of the shannon estuary in the upper crust the shallow part of the iapetus suture zone appears to be transported to the north by late caledonian retrocharriage or by variscan thrusting the iapetus suture does not penetrate through the present day reflection moho but there are scattered reflectors in the mantle not continuous with crustal reflectors perhaps relics of a subducted slab we recognize lower crustal reflectivity and the reflection moho along almost all the wire profiles regionally the travel time to the reflection moho varies from 9 s c 28 km offshore donegal northwest of ireland to 12 s c 35 km offshore kerry and cork southwest of ireland apparent moho offsets rapid lateral changes in the travel time to the reflection moho north of donegal and north of mayo are probably due to the great glen fault and associated faults the lower crustal reflectivity varies considerably in thickness and prevalent dip direction along the wire profiles in donegal bay this reflectivity is observed at depths less than 5 km c 1 5s whereas west of kerry prominent reflectivity is only observed beneath 6s c 17 km though the age of crustal reflectors cannot in general be determined beneath central ireland from donegal to dingle the lower crustal reflectors mimic in dip direction the structural vergence of the exposed dalradian and early palaeozoic rocks so that the lower crustal reflectivity patterns and probably much of the crust must be caledonian in age

implications of sediment flux dependent river incision models for landscape evolution 1 developing a quantitative understanding of the factors that control the rate of river incision into bedrock is critical to studies of landscape evolution and the linkages between climate erosion and tectonics current models of long term river network incision differ significantly in their treatment of the role of sediment flux we analyze the implications of various sediment flux dependent incision models for large scale topography in an attempt 1 to identify quantifiable and diagnostic differences between models that could be detected from topographic data or from the transient responses of perturbed systems and 2 to explain the apparent ubiquity of mixed bedrock alluvial channels in active orogens although certain forms of the various models can be discarded as inconsistent with morphological data we find that the relative intrinsic concavity indices of detachment and transport limited systems defined herein largely dictate whether the various models can be tied to distinctive steady state morphologies preliminary data suggest that no such diagnostic differences may exist and other methods must be developed to test models accordingly we develop and explore differences in the scaling behavior of topographic relief and the extent of detachment versus transport limited channels as a function of rock uplift rate that may allow discrimination among various models further we explore potentially diagnostic differences in the rates and patterns of transient channel response to changes in rock uplift rate in addition to general differences between detachment and transport limited systems our analysis identifies an interesting hysteresis in landscape evolution hybrid channels at the threshold between detachment and transport limited conditions are expected to act as detachment limited systems in response to an increase in rock uplift rate or base level fall and as transport limited systems in response to a decrease in rock uplift rate especially during postorogenic topographic decline the analyses presented set the stage for field studies designed to test quantitatively the various river incision models that have been proposed

comparative evolution of the iapetus and rheic oceans a north america perspective abstract differences in the origin and evolution of the iapetan and rheic oceans profoundly affected the development of the ouachitan appalachian variscan orogen the iapetus ocean was initiated in the late neoproterozoic early cambrian by the separation of large continental landmasses laurentia baltica gondwana whereas the rheic ocean originated in the late cambrian early ordovician as the result of the separation of several ribbon continents collectively termed peri gondwanan terranes from the northern margin of gondwana compared to the classic passive margin developed along the laurentian margin of iapetus passive margin successions to the rheic ocean are more limited in extent during convergence both margins of the iapetus ocean developed western pacific type arc back arc systems whereas subduction of the rheic ocean was primarily directed beneath laurentia and was andean in style closure of iapetus involved a number of arc back arc accretionary events and had occurred by the middle silurian as a result of laurentia baltica collision to form laurussia and the accretion of the peri gondwanan terranes rheic ocean closure occurred in the carboniferous by way of continent continent collision between laurussia and gondwana with gondwana on the lower plate within iapetus the formation of ophiolites occurred early in the orogenic cycle and was followed soon after by obduction hp lt metamorphism and foreland directed thrusting that is intimately related to accretionary events these features dominate the northern appalachian orogen where ht lp metamorphism is attributed to post accretionary slab break off events in contrast hp lt metamorphism within the rheic ocean reflects a type subduction during laurussia gondwana collision and is rapidly succeeded by ht lp metamorphism attributed to orogenic collapse ophiolites are rare and were formed either very early early ordovician or very late devonian carboniferous in the evolution of the ocean the early ordovician ophiolites were not obducted until the carboniferous at least 100 million years after their protoliths were formed rheic ocean closure resulted in the formation of large scale bivergent structures within the orogen with symmetry changing on either side of the rheic suture comparison of the evolution of the iapetus and rheic oceans suggests that differences in rift configuration passive margin development and subduction zone geometry within the two oceans profoundly influenced the subsequent style of orogenesis within the ouachita appalachian variscan orogen

morphometric dating of the fluvial landscape response to a tectonic perturbation 1 despite constant progress in numerical and field studies of landscape evolution time evolution is still poorly constrained in many uplifted areas where low denudation rates prevent the use of low temperature thermochronology especially outside high relief mountainous areas here i show that regional statistics of the landscape metric r involving hypsometric integrals at three nested levels of a catchment are able to isolate the time effect on landscape geometry during the latter s transient response to a tectonic perturbation analysis of 210 catchments from 9 regions of known uplift age worldwide shows that the regionally characteristic r derivedsrindex is in inverse power law relation with the time elapsed since a base level lowering suggesting a response time of 5 my this finding has important implications for quantifying the rate of landform evolution and determining whether a landscape has reached steady state form

diachronous variscan late orogenic collapse as a response to multiple detachments a view from the internides in france to the foreland in the irish sea