numerical study on deep seated gravitational slope deformation in a shale dominated dip slope due to river incision abstract based on numerical simulation this study investigates the triggering factors and evolution of deep seated gravitational deformation in a dip slope consisting of a shale dominated sequence of sediments results from continuum based finite difference numerical modeling demonstrate that long term strength degradation of a rock mass is a prerequisite for the development of gravitational slope deformation and that river incision resulting in change of slope geometry and corresponding stress concentration and redistribution is a major driving mechanism for the progressive evolution of deep seated gravitational slope deformation dsgsd numerical simulation considering the influence of weak planes indicates that the bedding planes control the strength of rock mass and form a structural constraint on the development of gravitational slope deformation a satisfactory correlation between the distribution of numerically simulated plastic shear bands and weak zones in drill cores demonstrates that the weak zones within the slope are formed due to gravitational slope deformation furthermore numerical simulation shows a link between geomorphological development and internal deformation of the slope which aids in the understanding of relationships between interior deformation of the slope the exterior geomorphology and related effect factors including river incision and strength degradation

active tectonics in the sierra nevada betic cordillera se spain insights from geomorphic indexes and drainage pattern analysis article i nfo the sierra nevada of the central betic cordillera is a 3000 m high mountain range surrounded by neogene quaternary sedimentary basins having been uplifted since late miocene times the southern and western mountain fronts of the sierra nevada are fault bounded while the northern one is an unconformity between the neogene quaternary sediments of the guadix baza basin and the metamorphic rocks of the nevado filabride complex we have carried out a geomorphic study by examining drainage patterns and characteristics of mountain fronts in order to reveal areal variations and styles of rock uplift mountain front sinuosity smf area altitude relations hypsometric curves and valley floor entrenchment differ significantly between the northern western and southern mountain fronts the lack of important faults along the northern sierra nevada mountain front together with the elevated topographic position of the guadix baza basin average altitude is around 1100 m points to similar uplift of both geomorphic units sierra and basin in a single large scale crustal block the asymmetry factors show systematic asymmetries at both sides of the lanjaron river probably due to the presence of an active nne ssw oriented antiform in the western sierra nevada finally river profiles indicate maximal river entrenchment in the western part of the sierra nevada probably related to the uplift of the footwall of the padul niguelas fault system therefore our geomorphic analysis suggests that the western part of the sierra nevada is tectonically active by means of a combination of normal faults along the mountain front and nne ssw oriented active folds which in turn likely have a gravitational origin related to the exhumation of the footwall of the normal fault system

non traditional and emerging methods for characterizing diffusion in minerals and mineral aggregates the data summarized in this rimg volume reflect the growing interest among geoscientists in the characterization of atomic transport in natural materials interest in diffusion dates back to the early 20th century e g bowen 1921 but the need for constraints on mobility of atoms became especially important in the 1950s and 60s with our increasing reliance upon radioactive decay for determination of mineral and rock ages the question of decay product retention in relevant phases became vitally important with a few notable exceptions however experimental geoscientists did not take up the cause of diffusion in solids until the 1970s and 80s by that time the motivation for acquiring diffusion data had spread to many areas of petrology mineralogy and geochemistry and experimental techniques began to blossom the result is very much in evidence in this volume all experiments aimed at measuring a diffusion coefficient have two things in common a technique to introduce the diffusant of interest to the sample and a method to determine the extent of diffusion traditionally diffusion experiments are designed to take advantage of an existing solution to the non steady state diffusion equation and experiments are conducted in such a way as to reproduce as well as possible the boundary conditions specified for the solution for ease of analysis and interpretation most experiments are set up to limit diffusion to just one dimension most researchers have further settled on one of three general experiment designs 1 the interdiffusion couple 2 the thin film geometry or 3 the constant surface concentration design fig 1 noble gas geochemists including those interested in k ar ar ar and u th he dating methods have exploited 3 d variants of this last approach by conducting bulk degassing studies of minerals in which radiogenic noble gases have accumulated over time in the natural environment baxter 2010

morphology and morphogenesis of a high latitude canyon the andoya canyon norwegian sea abstract the morphology of the high latitude andoya canyon in the norwegian sea was studied using multi beam bathymetry data the canyon excavation processes include sliding and slumping axial incision and gullying sliding and slumping has most frequently occurred in muddy sediments of the western sidewall due to canyon axial incision and undercutting and failures during infilling of a high relief terrain by alongslope transported sediments axial incision is inferred to be due to turbidity current erosion the turbidity currents were mainly the result of piracy of shelf sediments the eastern sidewall is dominated by gullies speculated to be the initial forms generated on a steep slope constructed from stiff poorly sorted glacigenic sediments from the present canyon morphology including the overall convex upwards form of the topographic long profile with a steep 20 25 upper headwall we favour a bottom up canyon development i e mass wasting and subsequent piracy of alongslope transported slope and shelf sediments in contrast to most other canyons the development of the andoya canyon was not only a result of side and headwall instability and axial incision most active during periods of high sediment transfer but also due to infilling of the canyon by sediments transported by alongslope flowing ocean currents and from the fennoscandian ice sheet at the shelf break there are little or no slide deposits covering the thalweg this leads us to suggest that the most recent process dominating within the canyon is turbidity current flushing and erosion inferred to have occurred during the holocene

reply to comment by j l diaz hernandez and r julia on quaternary landscape evolution and erosion rates for an intramontane neogene basin guadix baza basin se spain abstract we demonstrate that the age of 43 ka obtained for the topmost calcrete layer in the guadix baza remains the only reliable numerical dating of the flat geomorphic surface that marks the end of the sedimentation in the basin consequently the late pleistocene to holocene erosion rates derived from the incision of the present day drainage network into the flat geomorphic surface remain valid the calcrete radiometric ages reported by diaz hernandez and julia 2012 in their comment are untenable due to the contamination with detrital 230 th not corrected with the applied u th technique and the possible mix of textural elements with different ages older inherited grains and newly formed grains diaz hernandez and julia also quote u th ages for travertine terraces formed later than the calcrete layer these ages lack internal consistency probably due to systematic contamination and or weathering of the samples the archaeological ages reported by diaz hernandez and julia are subjected to great uncertainties but independently of the age assumed as most realistic they are completely compatible with the age of 43 ka that we obtained for the topmost calcrete layer in the guadix baza basin

late miocene stratigraphy and palaeogeographic evolution of the intramontane guadix basin central betic cordillera spain implications for an atlantic mediterranean connection abstract the guadix basin is an intramontane basin located in the central sector of the betic cordillera its late miocene stratigraphic record is divided into three depositional sequences limited by unconformities representing tectonic and or eustatic events depositional sequence i late tortonian is composed by two systems tracts the lower marks the beginning of marine sedimentation in the basin and comprises three retrograding lithological complexes or depositional systems coastal shallow platform and pelagic basin and is interpreted as a transgressive systems tract the upper systems tract consists of a shallow shelf prograding into a pelagic basin this systems tract exhibits a typically regressive pattern and was deposited during high sea level and is therefore interpreted as a highstand systems tract depositional sequence ii late tortonian is composed of both continental alluvial cones and shallow marine gilbert type delta shallow shelf and reef depositional systems the deposits of this sequence record a significant fall in sea level and are interpreted as a lowstand systems tract depositional sequence iii late turolian ventian or late tortonian messinian was formed of solely retrograding continental depositional systems alluvial fan lacustrine fan delta mud flat and lacustrine with this sequence begins the continental sedimentation in guadix basin in an endorheic context the palaeogeographic evolution of the guadix basin during the late miocene can thus be divided into three stages the first corresponds to depositional sequence i and is characterised by the development of shallow marine environments on the basin margins and deep water deposits in its centre during this stage the basin was connected to the west with the atlantic ocean via the granada and guadalquivir basins and toward the east with the mediterranean sea through the almanzora and campo coy basins in the second stage represented by depositional sequence ii most of the basin was occupied by shallow marine environments during this stage the connection with the atlantic and mediterranean was only open through the guadalquivir and campo coy basins respectively finally the third and last stage corresponding to depositional sequence iii is characterised by the development of continental environments throughout the basin this stage records the definitive closing of the connections with the atlantic ocean and the mediterranean sea

basement structure of the granada basin betic cordilleras southern spain abstract the analysis and interpretation of geophysical data gravity and seismic reflection has facilitated the definition of the granada basin structure the reflector showing the contact between the betic subbetic basement and the neogene quaternary sedimentary filling has been identified mapping of the basement in two and three dimensions is presented the presence of four important depocenters genil chimeneas cubillas and granada has been determined these troughs are limited by ridge areas through important sets of fractures in some cases the accumulation of neogene quaternary sediments reaches a thickness exceeding 3 km as in the genii and cubillas depocenters the mapping of the most important fractures affecting the basement has been achieved defining four systems that have influenced and conditioned the genesis and late evolution of the granada basin the directions of the most important groups of fractures are ne sw n70w to e w n45w and n10 30e

recent fault controlled glacis deformation and its role in the fluvial capture of the guadix baza basin betic cordillera southern spain abstract this work is focussed on the geomorphological changes related to the pleistocene capture of the formerly endorheic guadix baza basin betic cordillera we explore the possible tectonic controls in the basin opening through a combined geomorphological and structural study for this we have selected a study area that includes the connecting zone between the former endorheic basin and the capture channel guadiana menor river this zone also includes the se end of the so called tiscar fault zone tfz that has been active during the upper miocene and onwards we use the glacis surface that marks the end of the endorheic sedimentation middle upper pleistocene as the main reference surface to identify recent deformation structures our results indicate that the main channel crossing the pozo alcon glacis guadalentin river shows evidence of high levels of fluvial incision and that some anomalies in the stream longitudinal profile could be correlated to the presence of pre glacis faults linked to the tfz conversely abrupt changes in the stream orientation seems to be related to post glacis downthrow faults we have identified that the dextral strike slip tiscar fault the northern boundary of the tfz propagates towards the se as far as the guadalentin river giving rise to a deformation band with oblique slip that descends the sw block down to 250 m and affects the glacis surface additionally the pozo alcon glacis has undergone distributed deformation mainly achieved by n s to ne sw downthrow faults and subordinate wnw faults the roughly e w extension within the pozo alcon glacis can be interpreted as developed in the extensional lobe at the tip of a dextral strike slip fault the tiscar fault according to the orientation wnw ese and location of the guadiana menor river following the southern boundary of the tfz and the relief attenuation and tilting produced by the extensional systems in the pozo alcon glacis we interpret that the later stages of tfz activity probably controlled and favoured the localisation of the basin capture

on the effects of thermal properties structure and water bottom temperature variation on temperature gradients in lake sediments in heat flow determinations it is customary to treat the surface temperature variation as a finite sum of fourier components the medium is assumed to be homogeneous or horizontally stratified wit

3 d crustal structure of the extensional granada basin in the convergent boundary between the eurasian and african plates three dimensional p and s wave velocity models of the crust under the granada basin in southern spain are obtained with a spatial resolution of 5 km in the horizontal direction and 2 to 4 km in depth we used a total of 15407 p and 13704 s wave high quality arrival times from 2889 local earthquakes recorded by both permanent seismic networks and portable stations deployed in the area the computed p and s wave velocities were used to obtain three dimensional distributions of poisson s ratio r and the porosity parameter vpvs the 3 d velocity images show strong lateral heterogeneities in the region significant velocity variations up to 7 in p and s velocities are revealed in the crust below the granada basin at shallow depth high velocity anomalies are generally associated with mesozoic basement while the low velocity anomalies are related to the neogene sedimentary rocks the south southeastern part of the granada basin exhibits high r values in the shallowest layers which may be associated with saturated and unconsolidated sediments in the same area vpvs is high outside the basin indicating low porosity of the mesozoic basement a low velocity zone at 18 km depth is found and interpreted as a weak ductile crust transition that is related to the cut off depth of the seismic activity in the lower crust at 34 km depth a clear slow vp and vs anomalous zone may indicate variations in lithology and or with the rigidity of the lower crust rocks d 2002 elsevier science b v all rights reserved

medium term gully headcut retreat rates in southeast spain determined from aerial photographs and ground measurements this paper deals with gully retreat rates at different time scales whereby the short term time scale may span a time interval of 1 5 years the medium term time scale a time interval of 5 50 years and the long term time scale a time interval of more than 50 years an analysis of high altitude aerial photographs in combination with ground measurements allowed us to quantify volumetric gully head retreat rates for 12 permanent gullies in southeast spain guadalentin and guadix study areas over a 40 43 year time interval medium term time scale this resulted in an average retreat rate ve of 17 4 m3 year 1 a power relationship between drainage basin area a and medium term volumetric gully head retreat rate ve 0 069a0 380 r2 0 51 n 21 was found by combining the gully head retreat rates obtained in this study with those obtained by a dendrochronological method the exponent b and the coefficient of determination r2 of the power relationships ve aab increases from the short term to the long term time scale expressing the increasing importance of drainage basin area in gully development with time considerable differences between gully head retreat rates measured at the short and medium term time scales at individual gullies showed the importance of land use changes and unsuccessful management practices on gully head retreat and the episodic nature of gully head retreat when piping and tension cracking are involved higher gully head retreat rates are obtained at the medium term time scale compared to the short term time scale but the differences are not significantly different at 10 the medium term methods tend to measure proportionally more high gully retreat rates but less extreme values compared to the short term method this is explained by a more equal distribution of extreme rainfall events both in space and time at a longer term time scale and hence a higher probability of measuring the average effect of both small and extreme rainfall events at each gully

recent and present day stresses in the granada basin betic cordilleras example of a late miocene present day extensional basin in a convergent plate boundary the diffuse convergent boundary between the eurasian and african plates in the western mediterranean is associated with a seismicity zone more than 300 km wide although the two plates are converging nw se the betic and rif cordilleras contain extensional structures that have been active since the miocene the extensional tectonics in the region which occurred simultaneously with the uplift of the cordillera have been analyzed in the southeastern sector of the late miocene to recent granada basin using earthquake focal mechanisms the determination of paleostresses from the study of the orientation and kinematics of microfaults and the study of the major structures both the geological surface data and the focal mechanisms indicate present day regional conditions of ne sw extension with triaxial to prolate stress ellipsoids however the stress field is heterogeneous with local variations in stress over time with different stresses sometimes even acting simultaneously in adjacent areas the most frequent changes consist of pluridirectional or ne sw extension favored by the prolate character of the stress ellipsoids and nw se subhorizontal compression favored by the regional tectonic setting strike slip faults are scarce even though they are the most likely structure to be expected in a region with sw ne extension and nw se compression seismicity is concentrated in the upper crust and may correspond to the activity of low to high angle normal faults similar to the surface faults although they can not be correlated with them the lower cutoff of this seismicity probably coincides with the 300 c isotherm and suggests a low thermal gradient for the region present day regional stresses have 1 vertical at the surface but in depth plunge toward the sw

coupling between landslides and eroding stream channels reconstructed from spruce tree rings examples from the carpathians and sudetes central europe the analysis of the positive feedback between landslides and erosion requires determination of the precise temporal and spatial relations between events of colluvium delivery and fluvial erosion in our study we use decennial datasets on the occurrence of landsliding and erosion achieved through dendrochronological methods four sites covering areas of landslide slopes and adjacent valley floors with stream channels were studied landsliding on slopes was dated from the tree ring eccentricity developed in stems tilted due to bedrock instability erosion in channels was dated using the wood anatomy of roots exposed by erosion of the soil cover analysis of the temporal relations between dated landsliding erosion and precipitation record has revealed that two types of repeating sequences can be observed 1 rainfall landsliding erosion 2 rainfall erosion landsliding these sequences are an indication of the occurrence of slope channel positive feedback in the sites studied in the first type landsliding triggered by rainfall delivers colluvia into the valley floor and causes its narrowing which in turn causes increased erosion in the second type erosion triggered by rainfall disturbs the slope equilibrium and causes landsliding landsliding and erosion once triggered by precipitation can occur alternately in years with average precipitation and reinforce one another bidirectional coupling between landsliding and channel erosion was shown notably through the effects of channel shifting and forced sinuosity and by increased erosion of the slopes opposite the active landslides observations also suggest that the repetition of sequences described over longer periods of time can lead to a general widening of the valley floor at the expense of slopes and to a gradual change of the valley cross profile from narrow v shaped into a wide flat bottomed thus landsliding erosion coupling positive feedback was recognized as an important factor shaping hillslope valley topography of the mid mountain areas studied copyright 2014 john wiley sons ltd

gravitational instabilities triggered by fluid overpressure and downslope incision insights from analytical and analogue modelling fluid overpressure at the base of low permeability strata reduces effective stress allowing for gravitational sliding of the overlying cover the force driving sliding is the slope parallel component of the weight of the cover whereas the resisting forces are the friction at the base of the cover and the buttressing resistance to shortening which can be critically reduced by incision at the base of the slope we developed an analytical model and undertook a series of analogue experiments to better understand the evolution of a sedimentary cover sliding above a low permeability layer subjected to fluid overpressure where a downslope buttress was present the sliding sheet length decreased with increasing pore fluid pressure in the absence of such buttress the slide s length increased exponentially with increasing pore fluid pressure another important difference dealt with geometry and kinematics buttressed slides consisted of one large slope parallel mass rigidly translated and bounded by downslope thrusts and upslope normal faults with increasing pore fluid pressure the contractional structures propagated upslope by contrast non buttressed slides showed intense strain deformation started with normal faults forming near the incision then propagating upslope throughout the slide s evolution

tectonic constraints on a deep seated rock slide in weathered crystalline rocks abstract deep seated rock slides dsrss recognised as one of the most important mass wasting processes worldwide involve large areas and cause several consequences in terms of environmental and economic damage they result from a complex of controlling features and processes dsrss are common in calabria southern italy where the complex geo structural setting plays a key role in controlling the geometry of the failure surface and its development this paper describes an integrated multi disciplinary approach to investigate a dsrs in palaeozoic high grade metamorphic rocks of the sila massif it focuses on the definition of the internal structure and the predisposing factors of the serra di buda landslide near the town of acri which is a paradigm for numerous landslides in this area an integrated interdisciplinary study based on geological structural and geomorphological investigations including field observations of weathering grade of rocks minero petrographic characterisations geotechnical investigations and in particular fifteen years of displacement monitoring is presented stereoscopic analysis of aerial photographs and field observations indicate that the serra di buda landslide consists of two distinct compounded bodies i an older and dormant body 7 ha and ii a more recent and active body 13 ha that overlies the previous one the active landslide shows movement linked to a deep seated translational rock slide block slide the velocity scale ranges from slow 1 6 m year during paroxysmal stages to extremely slow

interplay between mass movement and fluvial network organization an example from southern apennines italy abstract relationships between landslides and drainage network arrangement have been investigated by classical and quantitative geomorphological analysis in an intermountain valley i e the upper valley of the sinni river of the southern italian apennines the 120 km 2 wide test area is characterized by very low grade metamorphic rocks mainly shale and associated crystalline metamorphic rocks which underwent high exhumation and uplift rates during quaternary times we recognized and mapped 534 landslides through the stereoscopic interpretation of one set of 20 panchromatic aerial photographs 1 33 000 scale landslides were classified according to both type of movement and relative age we detected and mapped 35 new landslides after a long rainfall period during the winter 2008 2009 the percentage of area affected by landslides d l of the area has a high value about 37 analysis of distribution of landslides areas within different age classes suggests that recent present day landslide distribution is strongly influenced by the legacy of widespread large and ancient landslides probably generated within a different morpho climatic setting a quantitative geomorphological analysis of the drainage network has been performed to evaluate the influence of landslide processes on morphometric properties of the drainage network in particular the degree of hierarchical organization of the drainage network is assessed through the hierarchical anomaly density a measure of the number of anomalous confluences i e channels of u order not flowing in channels of order u 1 in drainage basins on the basis of statistical relationships between morphometric indices of the drainage network and d l we argue that the activity of more recent mass movements rather than very old landslides can act as a disturbing element within the development of the drainage network generating anomalous confluences of the 1st order empirical relationships between suspended sediment yield and some geomorphic parameters of the drainage network allowed the estimation of short term denudation rates in the study area the comparison between uplift and denudation rates suggests that the landscape system has not reached a steady state between uplift and erosion in which tectonic uplift can represent a disturbing element within the recent morphogenesis on the basis of the data presented large mass movements in the study area are mainly linked to the relief growth promoted by quaternary tectonics whereas litho structural and morpho climatic factors assume a minor role

lithium isotope fractionation by diffusion in minerals part 2 olivine abstract recent experiments have shown that lithium isotopes can be significantly fractionated by diffusion in silicate liquids and in augite here we report new laboratory experiments that document similarly large lithium isotopic fractionation by diffusion in olivine two types of experiments were used a powder source method where lithium from finely ground spodumene lialsi2o6 diffused into oriented san carlos olivine and piston cylinder annealing experiments where kunlun clinopyroxene 30 ppm lithium and oriented san carlos olivine 2 ppm lithium were juxtaposed the lithium concentration along traverses across the run products was measured using both laser ablation as a source for a varian 820 ms quadrupole mass spectrometer and a cameca 1270 secondary ion mass spectrometer the cameca 1270 was also used to measure the lithium isotopic fractionation across olivine grains recovered from the experiments the lithium isotopes were found to be fractionationed by many tens of permil in the diffusion boundary layer at the grain edges as a result of 6li diffusing significantly faster than 7li the lithium concentration and isotopic fractionation data across the olivine recovered from the different experiments were modeled using calculations in which lithium was assumed to be of two distinct types one being fast diffusing interstitial lithium the other much less mobile lithium on a metal site the two site diffusion model involves a large number of independent parameters and we found that different choices of the parameters can produce very comparable fits to the lithium concentration profiles and associated isotopic fractionation because of this nonuniqueness we are able to determine only a range for the relative diffusivity of 6li compared to 7li when the mass dependence of lithium diffusion is parameterized as d 6 li d 7 li 7 6 the isotope fractionation for diffusion along the a and c crystallographic direction of olivine can be fit by 0 4 0 1 while the fractionation in the b direction appears to be somewhat lower model calculations were also used to fit the lithium concentration and isotopic fractionation across a natural olivine grain from a peridotite xenolith from the eastern north china craton the isotopic data were fit using values 0 3 0 36 similar to that of the laboratory experiments this along with the fact that the isotopic fractionation is restricted to that part of the mineral with a gradient in lithium concentration is strong evidence that the lithium zoning of this mineral grain is the result of lithium loss by diffusion and thus that it can be used as illustrated to constrain the cooling history

late quaternary large scale rotational slides induced by river incision the arroyo de gor area guadix basin se spain the arroyo de gor is a highly incised stream up to 200 m that has eroded into the pliocene pleistocene infill of the guadix basin in the betic cordillera se spain this paper concentrates on a particular reach of this stream namely the cenascuras gorafe reach where abundant inactive rotational slides can be recognized on both hillslopes of the canyon shaped valley the rotational slides have surface areas of 5 15 ha and volumes of mobilized material of 5 15 hm3 these rotational slides can be recognized by their main scarps which are still well featured at both margins of the valley as well as by the counter hillslope rotation of the strata in their bodies the surfaces of rupture are concave their width being greater than their length i e the landslides are elongated in a direction perpendicular to the landsliding displacement and parallel to the stream at depth the surfaces of rupture developed on fine grained sediments mostly clays underlying the conglomerates and sands affected by the rotational slides the clays at the surface of rupture are smectite rich and show several features produced by the landsliding such as striations and sigmoidal shaped structures the cenascuras gorafe canyon has been developed by a combination of entrenchment fracturing and landsliding initial deep entrenchment of the stream is attributed to a base level lowering related to the capture of the former endorheic basin by the gualdalquivir river in the late pleistocene this river incision created a canyon with subvertical unstable walls which due to gravitational instability would give way to vertical open tension cracks some distance from the canyon edge the tension cracks would end at depths equal to the base of the canyon which also coincides with the contact between the conglomerates and the underlying clays the rotational slides are thought to have occurred during heavy rains by a combination of piping which would have lengthened the tension cracks and infiltration which would reduce the shear strength along the gently dipping contact between conglomerates and the underlying clays thus the blocks bounded by the tension cracks and the subhorizontal lithological contact would slide under their own weight on the subhorizontal surfaces of reduced shear strength several age constraints lead us to tentatively assign the landslides to the isotope stage 5 around 32 ka an interglacial period agreed to be wetter and slightly warmer than the present day semi arid climate

reconciling li and o diffusion in zircon with protracted magmatic crystal residence lithium and o in zircon have strong potential as diffusion chronometers for assessing thermal histories of magmatic and metamorphic systems but their diffusion mechanisms remain controversial zircon populations erupted from el chichon volcano chiapas mexico often contain xenocrysts of detrital origin with juvenile overgrowth forming a natural diffusion boundary within individual crystals high spatial resolution o and li isotope analyses u pb and u th geochronology and li along with al and y scanning ion imaging were acquired to compare diffusion model timescales with those derived from radiometric dating oxygen isotopes in el chichon zircon xenocrysts preserve source heterogeneities with xenocrystic and juvenile domains of zircon being in o isotopic disequilibrium with the melt at the time of eruption preservation of these heterogeneities is consistent with recently determined o isotope diffusion parameters when crystal residence at magmatic temperatures is assumed over the 103 104 year timescales indicated by u th geochronology lithium concentration gradients across the same boundaries are sharp within the 2 5 m lateral resolution of the ion beam whereas li isotopic compositions for xenocrystic cores are homogeneous at 7li 7 8 2 3 1 standard error and different from their putative source diffusive equilibration of li isotopes in zircon is consistent with protracted magmatic crystal residence but preservation of li abundance heterogeneities is difficult to reconcile with evidence for recurrent high temperature exposure of zircon in a highly active magmatic system we speculate that li partitioning in zircon is in part coupled to slow diffusing trivalent cations which can cause severe underestimation of diffusion timescales extracted from li diffusion modeling

heat flow measurement in lacustrine or oceanic sediments without recording bottom temperature variations water bottom temperature variations btv introduce many uncertainties into heat flow density hfd values determined from the temperature depth t z plot from a one time probe insertion into the top few meters of sediments the btv have to be carefully monitored for a number of years up to the date of the probe measurements this makes the method time consuming and economically unattractive in this paper we present the theory for a promising new technique the method does not require monitoring of the btv but does require at least two t z profiles separated in time by only a few months a generalized inversion of the btv history using the separated t z data and any other a priori information that is available is then performed in the frequency domain to give the most probable bayesian estimates of various parameters and their error bounds numerical examples show that the inversion can resolve not only the hfd but also the mean sediment surface temperature and gives information on the longer term trend as well as details of the btv over the previous year these together with thermal properties structure are the factors that contribute most to the shape of the time dependent t z profiles used in a typical situation where a uniform half space with a background hfd 60 mw m 2 has been perturbed by complex btv with a maximum variation of 1 8 k using a misguessed hfd of 90 100 mw m 2 in the inversion of two t z profiles taken 3 months apart over a 2 to 5 m section results in a posteriori hfd of 58 11 m w m 2 although the technique gives an optimally determined mean hfd its principal value lies in the ability to place reliable error bounds on the mean

the depth of the earthquake activity in the central betics southern spain in this study we used relatively velocity independent methods wadati diagrams to estimate and check the focal depth of the seismic activity in a sector of the betic cordilleras alboran sea in southern spain to understand the behaviour of the seismic activity a total of 335 earthquakes have been analyzed the most interesting feature found in the analyzed sector is the strong variation of the focal depth on average the focal depth distribution in the granada basin is restricted to h 20 km the lower cut off in the seismic activity which is interpreted to mark the brittle ductile transition this cut off is coincident with a midcrustal reflector detected in the zone by previous seismic refraction and deep reflection experiments that was interpreted as an extensional detachment the seismic activity in the malaga zone reaches depths up to 100 km in this case the seismic activity affect to the crust and upper mantle the deepest activity coincides with low values of heat flow possibly thus indicating a thicking of the lithosphere towards the w in the centre of the alboran sea the activity is shallower and corresponds with a higher heat flow we think that our results support models that have proposed active delamination towards the west such a model may explain the increase in the lithosphere thickness in this direction which would be congruent with the depth of the earthquakes

heat flow measurements in 17 perialpine lakes thirty eight heat flow measurements were carried out in 17 perialpine lakes to supplement the scanty information concerning the thermal conditions in the crust underlying central europe a probe of the corer type was built which allowed the measurement of 11 temperatures at equally spaced subbottom intervals to a maximum penetration of 10 5 m measurements of this type were made in lake constance greifensee lake zurich lake zug lake lucerne baldeggersee lake biel lake murten lake neuch tel lake geneva lac d9annecy lac de bourget lago maggiore lago di lugano lago di como lago d9iseo and lago di garda after retrieval of the probe a sediment core was collected for samples on which thermal conductivity was measured with the needle probe method after treating the material to remove exsolved gas pubbles continuous seismic reflection and reflection profiles in all of these lakes provided a set of parameters for gradient correction due to heat flow refraction additional corrections were applied on the basis of palynologically determined sedimentation rates and for the influence of the last period of glaciation final heat flow values obtained in this manner are given the lesser values are generally found in the more western lakes north of the alps the higher values are found in the more eastern lakes north and south of the alps the higher values are partially confirmed by earlier measurements in lakes but show considerable discrepancy with measurements from the central alps this could be explained by the underthrusting of a cold wedge under the aar and gotthard massif in the late miocene and early pliocene which then would lower the temperature gradient in the central alps

sub bottom temperature perturbations due to temperature variations at the boundary of inhomogeneous lake or oceanic sediments abstract for many years continental heat flow data were obtained from temperature gradients measured in boreholes and conductivity measurements made on representative cores because of the difficulty of obtaining deep holes in suitable regions increasing use is being made of measurements made in the top few meters of the sediments at the bottom of continental lakes for reliable heat flow results two conditions must be met first an accurate record of the temperature history at the top of the sediment should be available preferably over a time span of 4 or 5 years second if the thermal properties are not constant with depth then the depth dependence should be known errors that may arise if either or both of these conditions cannot be met can be serious using various surface thermal histories we compare results from models assuming constant diffusivity a diffusivity changing exponentially with depth and a layered medium all being structures based upon observed variations near the sediment water interface where conductivity may change by a factor of two over 2 or 3 m in some situations errors as large as several hundred percents may occur but in such cases it should be possible to deduce from the data that something has occurred to make the data unreliable more realistically there are occasions where a temperature depth plot which is linear within normally acceptable limits of accuracy and with a gradient that is within the range of expectations may be as much as 100 in error

quaternary landscape evolution and erosion rates for an intramontane neogene basin guadix baza basin se spain abstract the landscape evolution in neogene intramontane basins is a result of the interaction of climatic lithologic and tectonic factors when sedimentation ceases and a basin enters an erosional stage estimating erosion rates across the entire basin can offer a good view of landscape evolution in this work the erosion rates in the guadix baza basin have been calculated based on a volumetric estimate of sediment loss by river erosion since the late pleistocene to do so the distribution of a glacis surface at ca 43 kyr characterised by a calcrete layer that caps the basin infilling has been reconstructed to support this age new radiometric data of the glacis are presented the volume of sediment loss by water erosion has been calculated for the entire basin by comparing the reconstructed geomorphic surface and the present day topography the resulting erosion rates vary between 4 28 and 6 57 m3 ha 1 yr 1 and are the consequence of the interaction of climatic lithologic topographic and tectonic factors individual erosion rates for the guadix and baza sub basins 11 80 m3 ha 1 yr 1 and 1 77 m3 ha 1 yr 1 respectively suggest different stages of drainage pattern evolution in the two sub basins we attribute the lower values obtained in the baza sub basin to the down throw of this sub basin caused by very recent activity along the baza fault

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

large lithium isotopic variations in minerals from peridotite xenoliths from the eastern north china craton abstractto investigate the effects of melt rock interaction on li isotope fractionation we report in situ li concentrations and 7li of olivine ol orthopyroxene opx and clinopyroxene cpx for six peridotite xenoliths from the eastern north china craton these xenoliths contain two lherzolites two cpx rich lherzolites and two wehrlites and are variably metasomatized lithium isotope zonation is observed in most peridotite minerals the majority of cpx grains display isotopically light cores with lower li concentrations than the heavy rims however the opx grains show a different style of zonation from cpx where higher li concentrations in the cores are associated with much lighter 7li olivines in most peridotites have a restricted range of li concentration and 7li within individual grains whereas the olivines in a lherzolite show isotopically light cores 10 3 with high li concentrations 2 3 ppm and heavy rims 5 5 with low li concentrations 1 7 ppm these li isotopic variations in m

geomorphologic evidence of the active baza fault betic cordillera south spain abstract the present work investigates a mountain front within the plio quaternary deposits belonging to the sedimentary fill of the guadix baza basin betic cordillera southern spain this 30 km long front developed in soft sediments and within a context of high erosion is generated by the recent activity of the baza normal fault the mountain front is the natural limit between the western and eastern sectors corresponding to the two sub basins of guadix and baza the two main glacis described in previous works in the area of the baza fault the old glacis in the guadix sub basin and the recent glacis in the baza sub basin are interpreted here as a single one displaced by the fault using this glacis as a marker we deduced that its age and the transition of the basin from endorheic to exorheic must be much older than previous estimations the baza fault may be considered as one of the most active faults of the central part of the betic cordillera according to the results of the general quantitative analysis of the mountain front relief using the smf vf ratio and the sl index

isotope fractionation by chemical diffusion between molten basalt and rhyolite abstract experimental diffusion couples were used to study chemical diffusion between molten rhyolite and basalt with special emphasis on the associated fractionation of calcium and lithium isotopes diffusion couples were made by juxtaposing firmly packed powders of a natural basalt suny morb and a natural rhyolite lake county obsidian and then annealing them in a piston cylinder apparatus for times ranging from 0 1 to 15 7 h temperatures of 1350 1450 c and pressures of 1 2 1 3 gpa profiles of the major elements and many trace elements were measured on the recovered quenched glasses the diffusivities of all elements except lithium were found to be remarkably similar while the diffusivity of lithium was two to three orders of magnitude larger than that of any of the other elements measured chemical diffusion of calcium from molten basalt into rhyolite was driven by a concentration ratio of 18 and produced a fractionation of 44ca from 40ca of about 6 because of the relatively low concentration of lithium in the natural starting materials a small amount of spodumene lialsi2o6 was added to the basalt in order to increase the concentration difference between basalt and rhyolite which was expected to increase the magnitude of diffusive isotopic fractionation of lithium the concentration ratio between li doped basalt and natural rhyolite was 15 and the resulting diffusion of lithium into the rhyolite fractionated 7li from 6li by about 40 we anticipate that several other major rock forming elements such as magnesium iron and potassium will also exhibit similarly larger isotopic fractionation whenever they diffuse between natural melts with sufficiently large differences in the abundance of these elements

the recent upper miocene to quaternary and present tectonic stress distributions in the iberian peninsula a general synthesis of the recent and present stress situation and evolution in the iberian peninsula was obtained from microstructural and seismological analysis the stress evolution was deduced from 1 fault population analysis fpa from 409 sites distributed throughout the iberian peninsula 2 paleostress indicators given by 324 stations taken from the bibliography and 3 seismic data corresponding to 161 focal mechanisms evenly spread in the studied region the application of fpa together with the determination of stress tensors and focal mechanisms for the whole iberian microplate has provided two main results 1 the iberian peninsula is undergoing a nw se oriented compression except for the northeastern part pyrenees ebro basin and iberian chain where it is n s to ne sw and the gulf of cadiz where it seems to be e w and 2 the main trends of the stress field have remained almost constant since the upper miocene the analysis performed by zones suggests the presence of local heterogeneities in the stress field

moraines and marls giant landslides of the lago pueyrredon valley in patagonia argentina abstract giant catastrophic landslides 108 m3 dot the formerly glaciated mountain forelands of the eastern patagonian andes from geomorphic mapping sedimentological logs and radiocarbon dating we infer the emplacement kinematics and approximate timing of giant landslides in moraines and other glacial deposits in the lago pueyrredon valley lpv argentina for the first time we report in detail examples of giant low gradient landslides with hummocky lobes derived from unconsolidated glacial deposits and weak bedrock we find that at least 4 5 km3 of debris and weak bedrock were mobilized by slope failures in an area of 500 km2 since the last glacial maximum lgm 25 18 ka nearly 90 of this landslide volume originated along the shores of or as subaqueous failures in a postglacial moraine dammed meltwater lake the larger landslides 1 km3 detached from moraines fringing the lake whereas other landslides displaced glacial and lake deposits either on the paleolake bed or in a river gorge that was cut upon drainage of the glacial lake sequences of till glaciofluvial and glaciolacustrine deposits overlying weak early miocene marlstone are mostly conducive to major landslides in the lpv cross cutting relationships indicate that largest landslides in the area originated during rapid glacial lake level drops distribution and internal structure of hummocks within landslide lobes suggest that these landslides were emplaced as catastrophic debris avalanches it suggests that giant catastrophic landslides in the glacier forelands of patagonia can result from layered weak rocks changes in meltwater lake levels and possibly as a consequence of strong earthquakes linked to rapid post glacial rebound following the retreat of the patagonian ice sheet pis

thermal history of deep sea sediments as a record of recent changes in the deep circulation of the eastern mediterranean 1 during three cruises of the medriff project in 1993 and 1994 154 geothermal heat flow measurements and seven ctd profiles in the water column have been collected along a 300 km sw ne oriented transect traversing the mediterranean ridge accretionary complex the original goal of the measurements was to identify areas of anomalous heat flow that could be interpreted as possible sites for fluid outflow contrary to expectations the upper few meters of the temperature profiles in the sediments showed decreasing temperature from the seafloor down to 3 to 6 m depth indicating consistently transient temperature regimes the only exception positive heat flow was found in the sirte abyssal plain measurements collected in the same area at different times indicated that the thermal structure in the bottom water and sediments had changed significantly at weekly monthly and interannual timescales one dimensional forward modeling of the conductive heat propagation into the sediment explains the observed thermal anomalies assuming up to 0 5 k warming of the bottom waters that propagated south westward from the matapan trench to the crestal area of the mediterranean ridge analysis of nonsteady state thermal profiles in the upper sediment provided time information on the onset of bottom water warming by what is now called the eastern mediterranean transient emt the sediment warming started in the matapan trench between spring 1992 and spring 1993 and reached the mediterranean ridge crest in spring summer 1993 the average propagation velocity of the thermal perturbation along the profile is about 0 5 1 6 km d 1 0 6 1 8 cm s 1

reassessing the cooling rate and geologic setting of martian meteorites mil 03346 and nwa 817 abstract lithium concentration and isotopic fractionation profiles across augite grains from two martian meteorites mil 03346 and nwa 817 were used to determine their thermal history and implications for their geologic setting the iron magnesium zoning and associated magnesium isotopic fractionation of olivine grains from nwa 817 were also measured and provide a separate estimate of the cooling rate the observed correlation of concentration with isotopic fractionation provides the essential evidence that the zoning of these grains was in fact due to diffusion and thus can be used as a measure of their cooling rate the diffusion rate of lithium in augite depends on the oxygen fugacity which has to be taken into account when determining a cooling rate based on the lithium zoning the fe mg exchange in olivine is much less sensitive to oxygen fugacity but it is significantly anisotropic and for this reason we determined the direction relative to crystallographic axes of the line along which the fe mg zoning was measured we found that the cooling rate of nwa 817 determined from the lithium zoning in augite grains and that based on the fe mg zoning of olivines are in good agreement at an oxygen fugacity close to that of quartz fayalite magnetite oxygen buffer the cooling rate of mil 03346 was found to be resolvably faster than that of nwa 817 of the order of 1 c h for the former and of the order of 0 2 c h for the latter an important observation regarding the history of mil 03346 and nwa 817 is that the lithium and fe mg zoning are only observed where the augite or olivine is in contact with the mesostasis which implies that they were already about 80 crystallized at the time diffusion began the augite and olivine core compositions while very homogeneous are not in equilibrium with each other which we interpret to imply that prior to the rapid cooling there must have been a protracted period of the order of years above the solidus during which the much faster fe mg exchange in olivine compared to that in augite allowed the olivine to maintain equilibrium with a changing melt composition while the augite was not significantly affected we suggest two possible geological settings for the origin and evolution of mil 03346 and nwa 817 1 a slow cooling stage in a crystallization front in a crustal magma chamber followed by eruption of melt plus portions of the crystallization front onto the surface where the final fast cooling took place at the bottom of a lava flow or melt pond and 2 eruption of a crystal laden melt as a thick long lived lava flow where the crystals continued to grow as a cumulate and were rapidly cooled when the overlying lava layer was suddenly drained

large landslides induced by fluvial incision in the cenozoic duero basin spain abstract the pleistocene opening of the endorheic duero river drainage basin northwestern spain and central portugal has led to river incision creation of steep valley sides and development of large 0 1 km2 and episodically active rotational and roto translational landslides along river reaches where a weak geological lithology has been exposed by river erosion these landslides occur in the central part of the duero basin despite low precipitation weak contemporary seismicity and low regional relief these landslides occurred as a result of the downcutting of the duero river and its tributaries through a sequence of miocene basin fill sediments in the last few thousand years the incision reached a series of high plasticity low strength clay layers within the sedimentary sequence owing to this mechanism these landslides occurred in a specific area at a specific period of time all of the large landslides are located at the outside of meander bends suggesting that river lateral erosion facilitated slip failures recent anthropogenic activities to control river flows and to stabilize river banks have decreased the possibility of future landslides in this area

testing the sensitivity of geomorphic indices in areas of low rate active folding eastern betic cordillera spain abstract active deformation structures have an incidence in topography that can be quantified by using geomorphic indices most of these indices have been checked in faulted regions with high deformation rates the application of several geomorphic indices hypsometric curve analysis normalized stream length gradient and valley width to valley height ratio to the drainage network of the southern limb of the sierra de las estancias antiform internal zones eastern betic cordillera where low rate active folding has been recognized allows us to investigate the suitability of these indices to identify active structures in such a scenario hypsometric curves clearly identify regions with recent uplift and young topography but they do not provide any constraint on the location of active folds local valley width to valley height index variations have been detected just coinciding whit the position of ene wsw active folds normalized stream length gradient index serves to locate active folds in areas of hard rock substratum but not in those areas with soft sediments neogene quaternary sedimentary basins this is most likely due to the fact that in the basins erosion is much more intense than in the hard rock sectors in view of these results we consider that geomorphic indices constitute a valuable tool for identifying sectors affected by low rate uplift related to active folding with the best results obtained in hard rock areas

relief and drainage evolution during the exhumation of the sierra nevada se spain is denudation keeping pace with uplift abstract we have performed a geomorphic analysis of the sierra nevada the highest range of the betic cordillera se spain with the aim to elucidate its late miocene to present day exhumation history the qualitative and quantitative analysis is based on filtered topography local relief swath profile analysis anomalies on stream orientation bulk erosion volume hypsometry and steepness index k sn all these parameters are intimately linked to river incision and development of drainage pattern having been calculated to assess the role of folding and faulting on the evolution of the sierra nevada moreover uplift rates in the core of the sierra nevada have been deduced from an extrapolation of the position of late tortonian to pliocene coastline deposits these data have been compared to apatite u th he fission track and 10 be cosmogenic data from se spain in order to evaluate the consistency among uplift thermal histories and denudation rates our preferred tectonic scenario is one that favors fast exhumation of the western sierra nevada in a nw se overall compressive setting produced by the convergence between the nubia and africa plates sub perpendicular to this compression a westward 4 mm year extensional hanging wall displacement promotes uplift and unroofing of the western part of sierra nevada

a novel heat flux study of a geothermally active lake lake rotomahana new zealand abstract a new technique for measuring conductive heat flux in a lake was adapted from the marine environment to allow for multiple measurements to be made in areas where bottom sediment cover is sparse or even absent this thermal blanket technique pioneered in the deep ocean for use in volcanic mid ocean rift environments was recently used in the geothermally active lake rotomahana new zealand heat flow from the lake floor propagates into the 0 5 m diameter blanket and establishes a thermal gradient across the known blanket thickness and thereby provides an estimate of the conductive heat flux of the underlying terrain this approach allows conductive heat flux to be measured over a spatially dense set of stations in a relatively short period of time we used 10 blankets and deployed them for 1 day each to complete 110 stations over an 11 day program in the 6 3 km lake results show that lake rotomahana has a total conductive heat flux of about 47 mw averaging 6 w m2 over the geothermally active lake the western half of the lake has two main areas of high heat flux 1 a high heat flux area averaging 21 3 w m2 along the western shoreline which is likely the location of the pre existing geothermal system that fed the famous pink terraces mostly destroyed during the 1886 eruption 2 a region southwest of patiti island with a heat flux averaging 13 1 w m2 that appears to be related to the explosive rift that formed the lake in the 1886 tarawera eruption a small rise in bottom water temperature over the survey period of 0 01 c day suggests the total thermal output of the lake is 112 132 mw and when compared to the conductive heat output suggests that 18 42 of the total thermal energy is by conductive heat transfer

heat flow density measurements in the sediments of three lakes in northern sweden abstract heat flow density measurements in the sediments of three lakes 36 m 73 m and 99 m deep were carried out during a period of 3 5 years the gradient measurements were made from ice during the winter season with a bullard type probe with nine thermistors 0 5 m apart the thermal conductivity was measured in situ corrections were made for the disturbing temperature wave in the horizontally stratified sediments caused by seasonal variations in the bottom water temperature it is clearly shown that the differences in bottom water temperatures between different years can be fully corrected for only by very long time series the heat flow density values obtained are compared with measurements in boreholes and they seem to be correct to within 20 30

a megalandslide in the northern caucasus foredeep uspenskoye russia geomorphology possible mechanism and age constraints abstract an extremely large landslide 2 8 km 3 in volume and 32 km 2 in area has been detected on the right bank of the kuban river in the northern caucasus foredeep russian federation the megalandslide has a very gently inclined slip surface

morphology and structure of a landslide complex in an active margin setting the waitawhiti complex north island new zealand article i nfo multi scale gravitational instabilities are widespread in the coastal ranges of the north island of new zealand we document here a detailed analysis of the waitawhiti landslide complex located in the core of the tawhero syncline and investigate the potential landslides triggering factors in the area four contiguous large slides form the waitawhiti complex these slides involve fine grained miocene sandstones and massive fractured siltstones sliding occurs mostly along nearly horizontal strata all slides are bounded laterally and or distally by deep incised valleys three gas seeps evidencing thermogenic gas release have been discovered in the vicinity of the slides we propose that river incision continuously removing distal buttresses is the main destabilizing factor in the area however additional factors such as tectonic activity and intense rainfall cannot be excluded we also propose that fluid overpressure reducing the effective shear strength at the base of low permeability layers may have influenced the triggering of landslides in the waitawhiti area

gis analysis of fluvial knickzone distribution in japanese mountain watersheds although a knickzone a location at which stream gradient is locally large and intense erosion occurs has been regarded as an important geomorphic feature in bedrock river morphology the distribution of knickzones has not been well investigated especially for broad area this study examines the distribution of fluvial knickzones along mountain rivers for the entire japanese archipelago whereas conventional manual methods of identifying knickzones based on map readings or field observations tend to be subjective and are impractical for a broad scale analysis this study employs a semi automated method of knickzone extraction using dems and gis in a recent study by the authors this method has been shown to enable efficient examination of knickzone distribution over a broad area investigations on major mountain rivers revealed that knickzones are generally abundant in upstream steep river reaches suggesting hydraulic origins for the knickzones the broad presence of such knickzones in the steep japanese mountain rivers indicates that rivers subjected to active erosion show complex morphology induced by natural irregularities of water flow hydraulics as well as various environmental perturbations such as climatic changes there also seems to be a characteristic frequency of knickzone distribution common to moderately steep to very steep bedrock reaches in japan although volcanic products such as lavas and welded pyroclastic flow deposits in valleys can cause distinct knickzones substrate geology plays only a limited role in determining the distribution and form of knickzones

long term control mechanisms of stream piracy processes in southeast spain the guadix basin developed as an endorheic depression during the upper miocene upper pleistocene its principal palaeogeographical characteristics are a large lake in the eastern sector an axial fluvial system and two fluvial systems transverse to it in the western sector the uplift of a central sector of the betic cordillera during the upper pleistocene affected the study area causing northward tilting from the internal zone of the cordillera sierra nevada and sierra de baza step faulting of the plio pleistocene infill of the ancient basin leaving more northern sectors in a lower topographical position alteration of fluvial current profiles and displacement of the ancient axial system to a position very close to the divide between the ancient endorheic guadix basin and the guadalquivir basin this facilitated capture of the endorheic basin by the headward erosion of a tributary of the guadalquivir river the region then began to be rapidly eroded as the new base level was now some 500 m lower than that of the ancient basin the present drainage network is similar to that of the ancient endorheic basin as regards the location of the main streams and the distribution of drainage patterns and fluvial styles although flow reversal is found in some stretches and a barbed drainage pattern appears locally as a result of the inheritance of drainage from the ancient basin fluvial superimposition is found in some stretches of the main streams 1997 by john wiley sons ltd

seismic potential of the main active faults in the granada basin southern spain the main active faults of the granada basin are located in its central eastern sector where the most important tectonic activity is concentrated uplifting its eastern part and sinking the western border several parameters related to the seismic potentiality of these active or in some cases probably active faults in this basin are used for the first time many of these faults can generate earthquakes with magnitudes larger than 6 0 mw although this is not the general case the fault situated to the n of sierra tejeda probably the one responsible for the big earthquake of 25 12 1884 stands out because it could generate an earthquake with magnitude 6 9 mw although at present all the data needed are not fully known we consider that the final results show as a whole the average expected return periods of the faults in the granada basin

tectonically driven landscape development within the eastern alpujarran corridor betic cordillera se spain almeria abstract the betic cordillera is a topographic manifestation of miocene to recent collision between the african and the european plates mountain ranges in the internal zone of the betic cordillera are exhumed massifs of metamorphic and sedimentary rocks and are surrounded by low lying sedimentary basins the neogene history of mountain range uplift and basin formation in the betics is well studied but quaternary topographic development and its relation to convergent plate boundary tectonics is less understood deformation rates of stream incision and factors controlling landscape evolution on the flanks of the highest mountains in the betic cordillera are studied to gain insight on the relationship of quaternary tectonics to topographic development specifically geomorphic processes that led to formation of topographic relief within the internal zone of the betic cordillera are assessed this paper is based on a field study conducted in the eastern alpujarran corridor eac which is the eastern half of a 4 6 km wide and 80 km long inverted sedimentary basin the mid to late quaternary history of basin denudation is deduced on the basis of morphostratigraphic geochronologic and structural geologic analyses of oxygen isotope stage 8 time fluvial deposits in the eac results of these analyses indicate that climate and faulting played only a minor role in landscape evolution in the eac instead the eac topographic trough was excavated by a drainage network whose axial stream rio andarax was incising at a rate between 0 3 and 0 7 m ka since oxygen isotope stage 8 this paper demonstrates that these incision rates are the same as regional rock uplift rates in the eac during the mid and late quaternary topographic relief between the eac and adjacent mountain ranges developed largely as a result of fluvial denudation driven by regional uplift the implications of the results of this investigation are used to propose a model of quaternary topographic relief development in the internal zone of betic cordillera topographic relief between internal zone bedrock massifs and adjacent basins formed largely as a result of fluvial denudation driven by regional uplift faulting also played a significant role in areas that are within a few kilometers of crustal scale fault zones

fluvial archives a valuable record of vertical crustal deformation abstract the study of drainage network response to uplift is important not only for understanding river system dynamics and associated channel properties and fluvial landforms but also for identifying the nature of crustal deformation and its history in recent decades geomorphic analysis of rivers has proved powerful in elucidating the tectonic evolution of actively uplifting and eroding orogens here we review the main recent developments that have improved and expanded qualitative and quantitative information about vertical tectonic motions the effects of horizontal deformation are not addressed channel long profiles have received considerable attention in the literature and we briefly introduce basic aspects of the behaviour of bedrock rivers from field and numerical modelling perspectives before describing the various metrics that have been proposed to identify the information on crustal deformation contained within their steady state characteristics then we review the literature dealing with the transient response of rivers to tectonic perturbation through the production of knickpoints propagating through the drainage network inverse modelling of river profiles for uplift in time and space is also shown to be very effective in reconstructing regional tectonic histories finally we present a synthetic morphometric approach for deducing the tectonic record of fluvial landscapes as well as the erosional imprint of tectonic forcing sedimentary deposits such as fluvial terrace staircases are also considered as a classical component of tectonic geomorphology we show that these studies have recently benefited from rapid advances in dating techniques allowing more reliable reconstruction of incision histories and estimation of incision rates the combination of progress in the understanding of transient river profiles and larger more rigorous data sets of terrace ages has led to improved understanding of river erosion and the implications for terrace profile correlation i e extrapolation of local data to entire profiles finally planform changes in fluvial systems are considered at the channel scale in alluvial rivers and regional level in terms of drainage reorganisation examples are given of how numerical modelling can efficiently combine with topographic data to shed new light on the dis equilibrium state of drainage systems across regional drainage divides

influence of combined incision and fluid overpressure on slope stability experimental modelling and natural applications abstract onshore slides are driven by gravitational forces that are either related to a basal or a surface slope resisting these driving forces are the friction at the base of the slide and the strength to compressional failure at the downslope edge of the slide two distinct processes can reduce these resisting forces and thereby promote slides on one hand fluid overpressure at the base of low permeability layers decreases the effective stress shifting the mohr circle closer to the failure envelope on the other hand river incision removes the downslope buttresses we undertook analogue experiments to investigate the combined influence of both processes on promoting landsliding we applied air pressure at the base of horizontal or tilted models made of high and low permeability layers to induce basal overpressure combined with local incision similar to river incision in nature we also tested the differences in deformation as a function of whether the incision was continuous throughout the models evolution no deformation occurred in the regions not subjected to overpressure in models subjected to continuous incision normal faults formed first along the valley flanks then propagated upslope retrogressively where incision was not continuous through time a downslope buttress progressively formed with the sliding mass comprised of an extensional domain upslope a long translated but non deformed slab at mid slope and a shortened domain downslope in our models the size of the deformed area increased with incision depth and or increasing basal slope these results show that river incision combined with fluid overpressure is a potential landslide triggering factor as suggested by field data gathered at the waitawhiti landslide complex north island new zealand

extreme lithium isotopic fractionation during continental weathering revealed in saprolites from south carolina the lithium concentration and isotopic composition of two saprolites developed on a granite and diabase dike from south carolina have been measured in order to document the behavior of lithium isotopes during continental weathering both saprolites show a general trend of decreasing d 7 li with increasing weathering intensity as measured by both bulk density and the chemical index of alteration cia the saprolite developed on the granite is isotopically lighter than the fresh igneous rock d 7 li 6 8x to 1 4x vs 2 3x respectively and is generally depleted in lithium these observations are consistent with leaching of lithium via rayleigh distillation during progressive weathering most saprolites fall on a rayleigh distillation curve corresponding to an apparent fractionation factor a of 0 997 however two samples have higher lithium contents than the fresh granite and thus point to additional processes affecting lithium in the saprolite e g sorption of lithium on to clay minerals the saprolite profile developed on the diabase dike shows highly variable d 7 li values ranging down to extremely light compositions 20x previous work has identified a chemical and mineralogical discontinuity at a depth of 2 m but our lithium data show a marked discontinuity at 6 m depth saprolite samples at or above 6 m depth are highly weathered cia 88 95 depleted in lithium having b50 of the original diabase lithium and isotopically light 10x to 20x vs 4 3x for the unweathered diabase most of the data are consistent with leaching of lithium via rayleigh distillation during intense weathering with apparent a values of 0 995 to 0 980 samples experiencing lower apparent a values tend to have higher kaolinite smectite ratios suggesting a mineralogical control on isotopic fractionation however the lightest sample at 20x is only slightly depleted in lithium and would require extremely low a values to explain via rayleigh distilliation this extreme composition remains enigmatic saprolite samples below 6 m have highly variable d 7 li 5x to 14x and importantly lithium concentrations that are higher than that of the unweathered diabase up to 2 4 times the concentration of the fresh diabase these deeper saprolites thus cannot be explained by rayleigh distillation a positive correlation between d 7 li and li

alkali diffusion in plagioclase feldspar tracer diffusion kinetics at 1 atm pressure under dry conditions using 6li 41k and 87rb in four plagioclase feldspars have been determined diffusion profiles were measured using an ion microprobe sims the arrhenius parameters and 2 uncertainties for li k and rb respectively in albite are pre exponential factor log do 3 8 1 0 3 4 1 4 and 5 8 3 8 in m2 s and activation energies 146 14 296 30 and 283 85 kj mol the diffusion rate of k in albite at 700 c and 100 mpa water pressure equals that at 1 atm dry suggesting that diffusion of k is not dependent on water fugacity between 0 004 and 100 mpa the k diffusion rate depends on plagioclase anorthite content and is approximately 20 times slower in labradorite than albite li diffusion rates in albite and anorthite are identical a linear relation between log d for the alkalis measured and their ionic radius squared permits an estimate of cs diffusion kinetics diffusion rates are isotropic or nearly so in albite

active continental subduction beneath the betic cordillera and the alboran sea p and s wave seismic tomography detect a low velocity anomaly in the upper mantle beneath the betic cordillera and the alboran sea region the anomaly is associated with the intermediate depth seismicity h

modelling mass failure in a mediterranean mountain environment climatic geological topographical and erosional controls extensive mass failures occur in the alpujarras on the south flank of the sierra nevada of southeast spain especially in the guadalfeo valley even though rainfall is low about 500 mm year there are four major controls on the occurrence of these landslides structure climate topography and erosion the tectonic control is through the structure and lithology of phyllites and mica schists with strong lineations providing preferred seepage and failure planes climate controls the long term seasonal and short term water pressure heads topography controls the localised head pressure gradients as a result of seepage and erosion controls the incidence of slope undercutting by fluvial action the effects of these controls are tested using a hydrological budget model for percolation to ground water a finite element model for ground water flows and stability analysis for modelling the actual failures the results suggest that in this mountainous terrain while climate may be very important for shallow failures the erosional history and the consequent morphology are in general much more important except for the trimming induced by occasional very large run off events

erosion and channel change as factors of landslides and valley formation in champlain sea clays the chacoura river quebec canada the champlain sea clays of eastern canada are incised by numerous rivers their slopes have been modified by landslides on the chacoura river near trois rivieres quebec several large landslide scars more or less recent are visible the role of erosion channel incision lateral channel migration and erosion of slopes due to agricultural drainage as a trigger of these landslides is important the aim of this study is to understand how erosion and landslides are related to valley development from a detailed analysis of aerial photographs and dems a map of the phenomena has been drawn by identifying various elements such as landslides limits of the slope position of the channel and the area covered by forest it is shown that channel change and erosion are strongly linked to landslides by the fact that they change the bank morphology in an unstable way a slide in itself is a natural way for the slope to achieve stability but when it occurs in a stream it creates a disturbance to the stream flow enhancing local erosion which may change the river path and generate more erosion downstream or upstream resulting in more slides cross valley sections and a longitudinal profile show that landslides are a major factor of valley formation it appears that the upper part of the chacoura river valley is still unaffected by landslides and has v shaped sections the lower part has been subject to intense erosion and many landslide scars can be seen this shows that the valley morphology is transient and that future activity is more likely to occur in the upper part of the river therefore the identification of areas prone to erosion will help determine the possible location of future large landslides just like the ones that occurred in the lower part

anatomy of a fossil landslide from the pleistocene of se spain abstract pleistocene landslide failures are rarely recorded in the literature due to difficulties in recognition in the field an adaptation of standard landslide classification based on activity is used to identify and examine the significance of a fossil pleistocene landslide from the mocatan catchment of the sorbas basin se spain recognition of the landslide is based on identifying key but subtle anomalies in the geology and drainage the fossil landslide at mocatan developed principally in response to a rapid increase in valley incision rates associated with capture induced base level changes in the master drainage this was facilitated by the weak sand and silt lithology of the study area the landslide was a significant morphological modifier of the environment holocene drainage follows the original landslide morphology whilst more recent gullying and piping exploits planes of weakness developed within the internal body of the landslide feature in addition the landslide removed much of the pleistocene divide facilitating future river capture

inversion of temperature measurements in lake sediment summary the problem of determining heat flow density hfd from temperature data obtained in lake sediments is formulated using an iterated linear inverse theory with numerical results presented in the forms of probability density function and sensitivity coefficient the galerkin finite element method and a weighted finite difference scheme are used in the spatial and temporal domains respectively to allow for layered structure in the sediments and for transient disturbances arising from lake bottom temperature variation btv with time when a record of btv is lacking inversion of temperature data from a single probe penetration gives an unreliable estimate of hfd this difficulty is alleviated by using multiple probe measurements which if taken at intervals of several months prove adequate for a reliable estimation of the hfd and the most recent part of btv thermal properties of the sediments however must be accurately known a priori because a simultaneous estimation of hfd btv and the thermal properties remains unattainable in a practical case hfd is usually resolved to the same extent that thermal conductivity is known a priori

numerical dating algorithms of amino acid racemization ratios from continental ostracodes application to the guadix baza basin southern spain abstract age calculation algorithms for the d l ratios of five amino acids isoleucine leucine aspartic acid phenylalanine and glutamic acid analysed in continental ostracodes were determined for southern and central iberian peninsula and allow the numerical dating of deposits in the mediterranean area since lower pleistocene time to present in order to obtain more accurate results for young samples other algorithms were calculated for aspartic acid phenylalanine and glutamic acid using these algorithms together with paleomagnetism the chronostratigraphy of the composite stratotype section of the east domain of the guadix baza basin that covers most of the pleistocene from the plio pleistocene boundary to 279 77 ka has been obtained ostracodes represent a formidable tool for amino acid racemization dating purposes in view of their abundance valves mineralogy and the high degree of preservation of amino acids within their caparaces even in old early pleistocene samples these results suggest that the range of the amino acid racemization dating method in the iberian peninsula is older than 1 1 ma

diffusion induced li isotopic fractionation during the cooling of magmatic rocks the case of pyroxene phenocrysts from nakhlite meteorites ion microprobe was used to measure li abundances and isotopic compositions in pyroxenes from three martian meteorites belonging to the nakhlite family the profiles performed across augite crystals from northwest africa 817 show a large isotopic zoning from crystal cores 7li not vert similar 0 to rims 7li not vert similar 20 while li abundances are almost constant not vert similar9 2 g g unlike nwa 817 the pyroxene studied in the miller range 03346 nakhlite shows a zoning in li abundance with concentrations increasing from not vert similar2 5 g g in the core to not vert similar9 g g in the rim the augite rim 7li 7 is slightly enriched in 7li with regard to the core 7li 4 but most of the isotopic variations observed occur at an intermediate position along the profile where 7li falls down to not vert similar 11 in the case of nakhla li concentrations in augite increase from cores not vert similar3 5 g g to rims not vert similar6 5 g g while the 7li variation is restricted i e between 7li 6 0 and 12 6 for the three meteorites the li abundances were also measured in the groundmass which was found to be enriched in lithium not vert similar10 g g conventional magmatic and post magmatic processes such as alteration and fractional crystallization fail to explain the dataset obtained on nakhlites degassing processes which were previously proposed to explain the li distribution in shergottite crystals cannot result in the strong decoupling between li abundances and isotopic composition observed in nakhlites we suggest that the original magmatic li distributions concentrations and isotopic compositions in nakhlites have been modified by diffusion of li from the li rich groundmass towards the pyroxene crystals during sub solidus cooling diffusion appears to have been efficient for nwa 817 and mil 03346 but apparently did not produce a significant migration of li in nakhla possibly because of the lower abundance of groundmass in the latter diffusion induced li redistributions may also affect terrestrial porphyric rocks but very specific cooling rates are required to quench the diffusion profiles as observed in two of the present nakhlites

evaluation of relative tectonic perturbations of the kashmir basin northwest himalaya india an integrated morphological approach abstract geomorphic and morphotectonic evaluations of the kashmir basin have been carried by implicating different geomorphic indices such as stream gradient index sl hypsometric integral hi drainage basin asymmetry af valley floor height and width ratio vf transverse topographic symmetry factor t mountain front sinuosity smf drainage basin shape bs and sinuosity index si for the categorization of relative index of active tectonics riat through the use of geographic information systems gis so as to decipher the role of neotectonics in geomorphologic evolution of the basin the verified riat classes through field investigation and validation reveal the traverse of twenty one active faults in the basin with demarcation of three riat classes viz class 1 inactive 20 07 of the area class 2 moderately active 36 52 of the area and class 3 very active 43 4 of the area the observed values of riat distribution pattern are well corroborated with field observations ultimately the overall geomorphic outputs and clustering of recent seismicity support the active tectonic control over the kashmir basin india

tectonic significance of the present relief of the betic cordillera abstract tortonian calcarenites of the betic cordillera were deposited in coastal or very shallow marine environments and represent an ideal marker for estimating vertical movements from the late miocene to the present a map showing the heights at which these tortonian marine rocks are situated has a clear correlation with the present relief indicating that today s relief has been formed since the tortonian there is also a good correlation between present relief and the bouguer anomaly distribution in the betic cordillera as well as with crustal thickness likewise the present relief is directly related to the geodynamic setting of a horizontal n s to nnw sse compression and an almost perpendicular extension along with isostatic readjustment existing in the betic cordillera from the tortonian as a result of these regional stresses faults and folds have produced notable vertical movements the highest rates of uplift of the betic cordillera coincide with large antiforms in particular those of the sierra nevada and the sierra filabres several subsiding sectors also exist for example the granada basin or the guadalquivir basin the foreland guadalquivir basin has a complex history because the uplift in its eastern sector and subsidence in the western sector coexisted during the late tortonian today the whole betic cordillera is characterized by differential regional uplift even in the aforementioned subsiding sectors

effect of slope failures on river network pattern a river piracy case study from the flysch belt of the outer western carpathians abstract landslides are important geomorphic agents in various mountainous settings we document here a case of river piracy from the upper part of the mala brodska valley in the vsetinske mts czech republic raca unit of the flysch magura group of nappes flysch belt of the outer western carpathians controlled by mass movement processes based on the field geological geomorphological and geophysical data we found out that the landslide accumulations pushed the more active river of out of two subparallel river channels with different erosion activity westwards and forced intensive lateral erosion towards the recently abandoned valley apart from the landslide processes the presence of the n striking fault accentuated by higher flow rates of the eastern channel as a result of its larger catchment area were the most critical factors of the river piracy as a consequence of the river piracy intensive retrograde erosion in the elbow of capture and also within the upper portion of the western catchment occurred deposits of two landslide dams document recent minimum erosion rates to be 18 8 mm ky 1 in the western captured catchment and 3 6 mm ky 1 in the eastern catchment respectively the maximum age of the river piracy is estimated to be of the late glacial and or the early holocene

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

gigantic low gradient landslides in the northern periphery of the crimean mountains ukraine abstract large scale low gradient ancient landslides estimated at 5 4 18 9 km 2 in area and 0 2 1 2 km 3 in volume have been studied in the northern hilly periphery of the crimean mountains ukraine they originated on slopes along wide water gaps of rivers belbek kacha alma and biyuk karasu crossing the cuestas of the northern foothills the slopes generally consist of slightly northward tilting miocene mainly sarmatian limestones overlying weak clay rich lower neogene palaeogene substratum with a significant content of smectite although the region is characterised by the least active contemporary morphodynamics within the crimean mountains the landslides which were studied are of the same size or even larger than various types of landslides occupying active geomorphic domains of the highest mountain range in the southernmost part of the peninsula the landslides are generally a spreading type but the sliding mechanics were probably very complex involving toppling rotational slides gravitational folding and translational block slides all the landslides which were studied are located in the vicinity of regional faults and three of them have headscarps aligned along faults a common feature is also a location close within several km to the mesozoic suture zone which is the most important tectonic feature in the northern periphery of the crimean orogene this suture was formerly classified as aseismic however evidence of strong low frequency palaeoearthquakes was collected during the last decade within both the mesozoic suture and the low lying northern part of the crimean peninsula radiocarbon dating of deposits associated with the landslides has revealed at least two phases of increased landslide activity during the late glacial chronozone and holocene epoch the main landslide phase presumably took place at some time between the late glacial and atlantic chronozones minor reactivation of landslide toes occurred during the subatlantic chronozone and some of them have been active up to recent times the first major landslide phase was possibly triggered by an earthquake whereas late holocene activity can be attributed both to seismic and hydroclimatic factors

p wave tomographic images in the central betics alboran sea south spain using local earthquakes contribution for a continental collision to investigate the relationship between shallow and intermediate depth earthquakes and the crust and upper mantle structure beneath the betic cordillera and alboran sea region we have applied seismic tomography to 2569 p wave arrival times from 367 microearthquakes recorded by both permanent and temporary seismic stations deployed in the region these earthquakes occurred in the depth range of 0 to 110 km beneath the central betic cordilleras and alboran sea our results have revealed significant structural heterogeneities in the crust and upper mantle beneath the study area in the upper crust there is a high velocity anomaly at sierra gorda western boundary of the granada basin penetrating to 15 km depth which is in good agreement with the aeromagnetic anomaly in the granada basin a low velocity anomaly is located in the middle crust which coincides with a previously detected greater cutoff depth of seismicity and are considered to be associated with a highly fractured zone generated by an intracrustal detachment the northern boundary of the alboran sea malaga coast is well imaged as low velocities from 50 to 90 km depths this low velocity zone in the upper mantle is associated with the intermediate depth seismicity which outline a section of continental crust related to the collision subduction beneath the northern part of the alboran sea southern part of the central betics

development of a new system for shallow sea heat flow measurement and its test application in the gulf of thailand abstract a new technique has been developed for the heat flow measurement in shallow seas the temperature in the sediment is measured at every 10 cm to the depth of 5 m by only one thermistor which moves up and down in the probe from the temperature data thus obtained the geothermal gradient is calculated in the least square sense by solving the thermal diffusion equation that is assuming an annual sinusoidal temperature variation at the sea bottom of which amplitude and initial phase are parameterized this system was used in the gulf of thailand and detailed temperature distributions were obtained in the future however to obtain more accurate heat flow values it is considered necessary to measure the temperature to at least the depth of 7 10 m

synchroneity between marine and terrestrial responses to millennial scale climatic variability during the last glacial period in the mediterranean region land sea climatic proxies have been obtained from the last glacial section of images core md95 2043 western mediterranean sea vegetation and alkenone derived sst curves indicate rapid 150 years and synchronous terrestrial and marine climatic changes paralleling the dansgaard oeschger d o climatic variability over greenland this frequency of climate change can be related to shifts between the two modes of operation of the north atlantic oscillation nao transfer functions applied to the pollen data indicate that there was an amplification of the climatic signal during heinrich events hes in comparison with other d o stadials the development and persistence of both scandinavian and atlantic mobile polar highs over southwestern europe may explain the extreme cooling 10 c and dryness 400 mm during heinrich events 5 and 4 in the mediterranean region comparison of the results of core md95 2043 with similar climatic data from images core md95 2042 located off portugal indicates that thermal and precipitation gradients occurred between the mediterranean and the atlantic sides of iberia within hes hes 4 and 5 are associated with more humid conditions in the atlantic by 200 mm than in the mediterranean site as is the case at the present time this comparison also illustrates the different behaviour of these areas during the d o stadials in contrast with the mediterranean site the atlantic site shows similar precipitation and temperature drops for all the d o stadials including those related to the hes here we propose the operation of different mobile polar highs mph as the driving mechanism for this difference in behaviour between the atlantic and mediterranean sides of iberia hes are related to a stronger influence of the scandinavian mph forcing a severe aridification and cooling of the full iberian peninsula the atlantic mph may have been dominant during the other stadials which would preferentially affect southwestern iberia

patterns and average rates of late neogene recent uplift of the betic cordillera se spain abstract the facies distribution in the sedimentary units infilling a series of neogene basins has been used to reconstruct the relief generation and uplift across the internal zone of the betic cordillera in southern spain uplift amounts and average rates can be estimated using the current elevation of the outcrops of well dated deposits indicative of ancient sea level positions coral reefs and coastal conglomerates record the initial development of emergent betic relief during the langhian continental and marginal marine deposits indicate the existence of a large island centred on the present sierra nevada sierra de los filabres chain by the end of the middle miocene the precursor of the sierra nevada sierra de los filabres chain originally part of this large island remained emerged whilst the surrounding areas were re invaded by the sea during the early tortonian at the end of the tortonian the inland basins granada and guadix basins became continental while the sierras de la contraviesa sierra de gador and sierra alhamilla emerged separating the alboran basin from the alpujarra tabernas and sorbas basins which became narrow passages of the mediterranean sea in contrast the sierra cabrera emerged during the late messinian suggesting a progressive uplift from west to east of the sierras south of the sierra nevada sierra de los filabres chain during the pliocene only the low areas closest to the present day coast remained as marine basins and progressively emerged throughout this stage the highest average uplift rate recorded is 280 m ma for the sierra de gador although the average uplift rates of upper neogene coastal marine rocks since depositon have maximum values of approximately 200 m ma most of the uplift of the betic mountains took place before the early pliocene the recorded uplift of neogene rocks was highest at the margins of western sierra nevada where peaks higher than 3000 m occur the average rates of uplift were lower to the east of this major relief the main sierras and depressions in the present day landscape correspond respectively to the emergent land in which uplift was concentrated and to the marine basins that existed before the final emergence of the region the altitude of the sierras reflects the time at which they became emergent the highest mountains being the first to rise above sea level

characteristics and controlling factors of bank gullies in two semi arid mediterranean environments abstract bank gullies are gullies that are formed due to a height drop caused by a terrace or a river bank which develop by headward retreat in erodible hillslopes this study aims i to investigate the morphology of actively eroding bank gullies i e geometrical characteristics resulting from past erosion and active erosion processes shaping the gully and ii to find relationships with environmental site characteristics such as topographical parameters material properties and climate the ultimate goal is to identify the most important controlling factors of past and present bank gully erosion fifty five active bank gullies formed in different lithologies by various erosion processes have been selected in the guadalentin basin and the surroundings of guadix southeast spain for each bank gully site geometrical and topographical parameters of both the channel and the drainage basin were measured erosion features indicating activity at the gully head such as tension cracks plunge pools undercutting fluting piping and rill or sheet erosion on sloping side walls were mapped and samples were taken from distinct lithological layers that were considered to influence the type and intensity of erosion processes a relationship could be shown between the presence of piping and fluting and a number of material characteristics including particle size distribution dispersion behaviour and electrical conductivity on the other hand lithology appeared not to be a differentiating factor on gully development in the long run as expressed by the total eroded volume v this parameter was most strongly related to the drainage basin area in which the entire bank gully had been formed a o explaining 66 of the variance the relationship is v 1 75 a o 0 59 no significant difference was found between regression lines through sub datasets of different soil textural classes finally multiple regression was used to include both topographical parameters and material characteristics in an explanatory and or predictive equation for the total eroded bank gully volume the results of the analyses using the entire dataset including the sites in the guadalentin as well as in the guadix area have been compared with the results for the separate study areas differences are not only related to topographical and lithological characteristics but may also be the consequence of a different climate in the two areas

s c mylonites two types of foliations are commonly developed in mylonites and mylonitic rocks a s surfaces related to the accumulation of finite strain and b c surfaces related to displacement discontinuities or zones of relatively high shear strain there are two types of s c mylonites type i s c mylonites described by berthe et al typically occur in deformed granitoids they involve narrow zones of intense shear strain which cut across mylonitic foliation type ii s c mylonites described here have widespread occurrence in quartz mica rocks involved in zones of intense non coaxial laminar flow the c surfaces are defined by trails of mica fish formed as the result of microscopic displacement discontinuities or zones of very high shear strain the s surfaces are defined by oblique foliations in the adjacent quartz aggregates formed as the result of dynamic recrystallization which periodically resets the finite strain clock these oblique foliations are characterized by grain elongations alignments of segments of the grain boundary enveloping surfaces and by trails of grains with similar c axis orientations examples of this aspect of foliation development in mylonitic rocks are so widespread that we suggest the creation of a broad class of s c tectonites and a deviation from the general tradition of purely geometric analysis of foliation and time relationships kinematic indicators such as those discussed here allow the recognition of kilometre scale zones of intense non coaxial laminar flow in crustal rocks and unambiguous determination of the sense of shear

a temperature probe survey on the louisiana shelf effects of bottom water temperature variations a survey of temperature gradients in the uppermost sediments of the louisiana continental shelf was done in 1983 by gulf oil corporation using a 5 m long temperature probe the survey covered 450 sq mi with an average grid spacing of less than 1 mi the purpose was to detect heat flow anomalies due to subsurface fluid flow however thermal perturbations due to seasonal variation of bottom water temperature mask the temperature gradients due to geological heat flow bottom water temperature variations similar to those recorded near the survey area in 1963 1965 explain most of the observed spatial and temporal changes in shallow temperature depth profiles the data set from this detailed survey has been donated to a publicly accessible scientific database to spur resear h into heat flow measurement on continental shelves

heat flow and gravity responses over salt bodies a comparative model analysis two dimensional numerical modeling of sea floor heat flow and water bottom gravity responses to systematic variations in simple subsurface salt body geometries provides insight on the relative usefulness of these two data types for extracting salt geometry information for a given salt body geometry diffusion of heat through overlying sediments results in a dramatic decrease in the amplitude of heat flow anomalies as the depth to the top of the salt body increases for top of salt depths greater than about 1 km the heat flow response is insensitive to the length of salt feeder stocks and to the thickness of salt tongues sheets this shallow depth to top of salt sensitivity range in addition to a number of environmental factors that can adversely affect interpretation of heat flow anomalies in terms of heat refraction towards and through salt bodies severely limits the usefulness of sea floor heat flow data for constraining aspects of salt body geometry for gravity data the critical factor for addressing salt body geometry is the distribution of salt relative to the sediment salt density crossover depth above and below which salt is more and less dense respectively than the surrounding sediment except when the relevant geometry information being sought presence and or length of feeder stock thickness of salt tongue or sheet is near the density crossover depth the geometry related information content of the gravity field is greater than that of the heat flow field based on these model results measurement uncertainty considerations and data limitations we conclude that gravity data generally offer an order of magnitude greater resolution capability than sea floor heat flow data for addressing salt body geometry issues of exploration interest

nitrogen diffusion in silicate minerals with implications for nitrogen transport and cycling in the lithosphere abstract diffusion laws for nitrogen in orthoclase quartz olivine and clinopyroxene were determined using a combination of experimental strategies that included in diffusion from c h o n vapor in diffusion from molten nh4cl and ion implantation followed by heating to mobilize n most experiments were conducted at pressures near 1 bar but seven experiments were also run in a piston cylinder device at ptotal 1 gpa the c h o n source experiments were wet h2o present those on ion implanted samples were dry all n sources were highly enriched in 15n to avoid spurious 14n signals resulting from surface contamination use of 15n also enabled depth profiling by nuclear reaction analysis nra using the 15n p 12c reaction which has a detection limit of 10 ppm nitrogen profiles in three samples were characterized by both nra and sims with similar results a total of 17 to 28 diffusion coefficient measurements were made on each of the four minerals 83 in all yielding results that conform for each mineral to an arrhenius relation of the form d d0exp ea rt the following values for the pre exponential constant d0 and activation energy ea were obtained mineral log d0 m2 s ea kj mol t range c orthoclase 13 9 0 4 95 4 6 6 500 900 quartz 12 4 0 3 147 3 5 7 550 1150 olivine 14 2 0 3 135 2 6 6 650 1400 clinopyroxene 14 1 0 3 135 6 7 4 750 1300 the various experimental strategies yield generally indistinguishable results at a given temperature and no significant effects of total pressure or h2o are discernible in the overall diffusion data set experiments that involved in diffusion from external n sources provide qualitative insight into the compatibility of n in the structures of the four minerals nitrogen concentrations attain the highest levels in orthoclase 100 8000 ppm atomic with quartz olivine and clinopyroxene falling in the tens to hundreds of ppm range the new diffusion laws enable us to model the diffusive release of n acquired at depth in the crust during fluid absent exhumation and cooling in general orthoclase is the least retentive of the minerals investigated and will lose most of its n during cooling from 600 c at tectonically typical rates olivine and clinopyroxene are the most retentive of n quartz is intermediate in retentivity between the mafic minerals and feldspar but in all cases the extent of n exchange with the surroundings depends critically on the specific t t path of the mineral of interest in subduction settings where n bearing fluid is released to the mantle wedge diffusion is sufficiently fast to homogenize individual mafic mineral grains with respect to n over geologically plausible time scales but equilibration on the outcrop or regional scale via volume diffusion is precluded by our data

lithium isotopic compositions of post collisional mafic ultramafic rocks from dabieshan china implications for recycling of deeply subducted continental crust abstract lithium li isotopes are potential tracers of processes related to crust mantle interaction and recycled crustal materials previous studies have reported that li isotopic compositions of island arc lavas are similar to those of fresh mid ocean ridge basalts morbs although the former are expected to record high slab derived 7li values caused by fluid metasomatism however it is unclear whether li isotopic signatures of subducted continental crust were transported to mantle depths and preserved there for clarification we determined whole rock major and trace element and li isotopic compositions of post collisional mafic ultramafic rocks from northern dabieshan china the analyzed samples have high mgo up to 20 67 wt and low sio2 41 06 56 20 wt contents and arc like trace element distribution patterns suggesting derivation by partial melting of fertile mantle sources the samples have 7li values of 2 9 to 7 2 average 2 7 n 42 and li concentrations of 2 50 to 28 1 g g average 9 20 g g both of which are beyond the relatively limited ranges of mantle values 7li 2 9 to 4 3 average 3 5 1 0 and li 1 20 0 10 g g excluding possible effects of wall rock assimilation and contamination magmatic crystallization and li isotopic fractionation during subduction exhumation processes the observed li isotopic heterogeneity is most likely related to the recycling of crustal materials based on a comparison with li isotopic compositions of ultrahigh pressure uhp metamorphic rocks from the dabie sulu orogenic belt and terrestrial sediments we suggest that the recycled continental crustal materials likely comprised gneisses sediments eclogites and or minor carbonate rocks i e marbles our study demonstrates that li isotopes may provide a novel means of tracing deeply subducted continental materials

microseismicity and tectonics in the granada basin spain a microseismic experiment carried out in 1994 in the granada basin spain permitted the precise recording of more than 80 local earthquakes the dense distribution of the local network with 40 to 50 instrumental records for each event enabled us to have well controlled hypocenters and also 10 reliable focal mechanisms the above observations are interpreted together with topographic data neotectonics and sub surface information microtectonic observations in sierra elvira padul and zafarraya gave a set of fault planes and striae which were interpreted in terms of the recent regional stress tensor the actual stress tensor obtained from the microseismic campaign data gives a regime in radial extension with r1 vertical and r3 oriented ns to nne microtectonic information is coherent with these orientations but closer to 3 axial extension a set of 64 mechanisms obtained from the permanent andalusian network favors a ns orientation for r3 this results are interpreted in terms of the general model implying the lateral ejection of the betic ranges towards the atlantic d 2002 elsevier science b v all rights reserved

diffusion driven extreme lithium isotopic fractionation in country rocks of the tin mountain pegmatite abstract lithium concentrations and isotopic compositions in the country rocks amphibolites and schists of the tin mountain pegmatite show systematic changes with distance to the contact both li and 7 li decrease dramatically along a 10 m traverse from the pegmatite into amphibolite with li concentration decreasing from 471 to 68 ppm and 7 li decreasing from 7 6 to 19 9 rubidium and cs also decrease from the pegmatite contact into the country rock but only within the first 2 m of the contact after which their concentrations remain constant neither mixing between pegmatite fluids and amphibolite nor li isotope fractionation by rayleigh distillation during fluid infiltration is a likely explanation of these observations due to the extremely light isotopic composition required for the amphibolite end member in the mixing model 7 li 20 and the similarly extreme isotopic fractionation required in a rayleigh distillation model rather these variations are likely due to isotopic fractionation accompanying li diffusion from the li rich pegmatite li 450 to 730 ppm into amphibolites li 20 ppm the fact that other alkali element concentrations vary only within 2 m of the contact reflects the orders of magnitude faster diffusion of li relative to heavier elements quartz mica schists in contact with the pegmatite also show large variations in both li and 7 li as a function of distance from contact 1 wt to 70 ppm and 10 8 to 18 6 respectively but over a longer distance of 30 m lithium concentrations of the schist decrease from 1 wt adjacent to the contact to 70 ppm 300 m from the contact the latter is a typical concentration in metapelites the nature of the 7 li variations in the schists is different than in the amphibolites schists within the first 2 m of the contact have nearly identical 7 li of 10 which mimics that of the estimated bulk pegmatite 8 to 11 at a distance of 30 m the 7 li reaches the lowest value in the schists of 18 6 similar to the lowest amphibolite measured at a distance of 300 m the 7 li climbs back to 2 5 which is within the range of 7 li of other schists in the region and metapelites worldwide the behavior of li in the schists can also be modeled by li diffusion with the effective diffusion coefficient in the schist being 10 times greater than that in the amphibolite the effective diffusion coefficients of li in the amphibolite and schist are 2 orders of magnitude greater that those in minerals which implicates the importance of fluid assisted grain boundary diffusion over solid state diffusion in transporting li through these rocks

normal faulting driven by denudational isostatic rebound fluvial piracy in the guadix baza basin southeast spain promoted erosion of a high volume of sediments during the late quaternary after the former internal drainage of this basin changed to external due to headward erosion by the guadalquivir river as a response to load release this basin underwent uplift which in turn enhanced fluvial incision and erosional processes differential erosion within the guadix baza basin resulted in dissimilar isostatic rebound we numerically model the lithospheric response to sediment unloading and show a total rising of 15 m in the guadix subbasin compared to 2 m in the baza subbasin this differential uplift is likely to have been accommodated along the baza normal fault which has been active throughout the quaternary modeling results suggest that 13 of the total quaternary fault throw directly arises from the differential isostatic readjustment between subbasins this example is one of the first estimates of fault slip partitioning between tectonic and isostatic effects due to unloading driven by river incision

the establishment and influence of baimakou paleo dam in an upstream reach of the yangtze river southeastern margin of the tibetan plateau abstract landslide damming is an important disturbance factor in the river evolution of mountain belts and may control river morphology at variable timescales this temporal aspect is mostly discussed in terms of the spatial relationships between the dams and river longitudinal profiles within any given region largely lacking are detailed studies of the geomorphic response for individual dams here we present field evidence and 24 optically stimulated luminescence osl ages that show the history of a landslide dam in an upstream reach of yangtze river at the southeastern margin of the tibetan plateau and its influence on river evolution the distribution of lacustrine ages suggests that there was only one long term damming event induced by landslide blocking the river the dammed lake formed at 12 1 ka and disappeared at 7 5 ka the estimated dam height was 120 m lake area was 96 km2 and lake volume was 7 5 km3 in addition the grain size and distribution of lacustrine deposits indicate the dam failed cataclysmically when the lake finally drained today the river long profile upstream of the dam site remains lower and the channel is wider in contrast to the downstream reach consequently the former dam still influences channel morphology our study shows that the interaction of landslide dams with the rivers in the southeastern tibetan plateau may impeded valley incision and headward erosion in those cases where damming continued over periods of several thousand years

lithium isotope analysis of olivine by sims calibration of a matrix effect and application to magmatic phenocrysts high spatial resolution analysis of light element isotope variations by secondary ion mass spectrometry sims has numerous applications in geochemistry and cosmochemistry recent attention has focused on 7li 6li variations in magmatic phenocrysts to infer the volatile degassing history of their parent magmas and on minerals from mantle samples to determine source region processes and the recycling history of mantle reservoirs in these studies the effect of mineral composition on the 7li 6li ratio measured by sims has been considered secondary and generally disregarded we show using a suite of nine olivines analyzed by mc icp ms or tims that there is a substantial effect of composition on the 7li 6li ratio of olivine measured by sims for magnesian olivine 74 fo 94 the effect is a linear function of composition with 7li increasing by 1 3 for each mole percent decrease in forsterite component at higher fe contents the relationship ceases to be linear the composition range over which linear behavior is exhibited appears to depend on instrumental conditions a calibration of this matrix effect over the linear range is presented assuming the measurement of 7li 6li relative to an olivine standard of known composition application of this calibration to a suite of olivines separated from basaltic lavas from ko olau hawai i demonstrates that the matrix effect is responsible for a geologically spurious correlation between 7li and mg however after correction the olivines retain evidence of li isotope heterogeneity the degree and nature of which differs in each of the four separates studied these results emphasize the importance of compositional correction for sims measurement of 7li in olivine particularly in zoned crystals and support previous conclusions that li isotope variability in igneous materials is subject to late stage disturbance the significant matrix effect demonstrated for olivine suggests that matrix effects in other minerals require further evaluation

seismotectonics of the ibero maghrebian region abstract a study of the seismotectonics of the ibero maghrebian region is presented as deduced from main geological features seismicity and focal mechanism data the hypocentral distribution of shallow intermediate depth and deep earthquakes is analyzed the direction of the stress distribution is inferred from the focal mechanism of 24 selected events a seismotectonic framework summarizing these results together with the main geological features shows that a nw se general direction of horizontal compressive stresses is present in the region with a localized zone of horizontal tensions in the betics and the alboran sea the presence of intermediate depth and deep earthquakes is tentatively explained as caused by two consecutive processes of subduction

influence of strike slip fault segmentation on drainage evolution and topography a case study the palomares fault zone southeastern betics spain abstract the palomares fault zone pfz is one of the main sinistral strike slip faults in the betics se spain with approximately 16 km of north south displacement the pfz initiated during the tortonian messinian as a transfer structure linking areas subject to nw se shortening during the plio quaternary the fault zone lengthened cutting previous fold structures and widened towards the east displacing the active mountain front to the western border of sierra almagrera sierra almenara these sierras which show moderate uplift rates of 0 05 0 15 m ka formed in response to the oblique slip regime of the pfz the drainage system in the vicinity of the pfz is asymmetric with respect to a main axial valley that runs parallel to the pfz on the downthrown fault block in this block the drainage density is lower and the streams are longer than in the uplifted block furthermore west of the main axial valley the streams describe eastward directed deflections indicating the progressive eastward migration of the main axial valley during the pleistocene the drainage system on the uplifted ranges shows a consequent pattern indicating recent uplift and folding under nnw sse convergence recent activity along segments of the pfz has increased topographical gradients favouring dissection of previous streams by headward erosion of streams transverse to the active fault segments

controls and feedbacks in the coupling of mountain channels and hillslopes mountain channels can be strongly coupled with adjacent hillslopes exchanging both mass and energy however hypotheses of the underlying cause and effect relations are based on indirect observations that do not resolve the mechanics of channel hillslope coupling at the process scale here we present direct observational data of a coupled channel hillslope system in the catchment area of the erlenbach a mountain stream in switzerland a slow moving landslide flanking this alpine stream failed after a flood had eroded an alluvial step in the channel at its base representing evidence for an upsystem link in channel hillslope coupling progressive accumulation of landslide debris in the channel resulted in a renewed step stabilizing the hillslope and restoring the channel step in a downsystem link thus upsystem and downsystem coupling mechanisms are joined in a negative feedback cycle in this cycle debuttressing and rebuttressing due to channel bed erosion and alluviation are the dominant controls on hillslope stability based on an order of magnitude estimate it is plausible that the observed feedback mechanism is a relevant process in the production of coarse 2 mm sediment in the erlenbach