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

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

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

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

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

laboratory investigations into wave period effects on sand bed erodibility under the combined action of waves and currents laboratory experimental data on sediment threshold conditions for fine to coarse sands under the combined action of waves and currents are presented higher flows are needed to satisfy threshold under short period waves than for longer period waves the combined threshold velocities indicate that under the shorter 5 s period waves the oscillatory and steady flows are independent of each other but interact to a greater extent as the wave period increases the derived threshold flow conditions are converted into threshold shear stress values using existing linear and non linear models the performance of the models for various periods of oscillation is then examined in view of the assumption that a unique threshold value exists for a particular grain size all models suggest that the critical stress of a particular grain is higher under shorter period waves for the range of grain sizes presented using different models for waves of different periods appears to remove the effect of wave period upon the data it is suggested that theories used by the existing models are insufficient to fully describe the interaction of the steady and oscillatory flows during the experiments

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

do critical stresses for incipient motion and erosion really exist the concept of critical stress for the initial motion of noncohesive sediment beds under turbulent flow conditions is reviewed observational definitions of incipient motion are many and not entirely compatible some laboratory flume observations of sediment movement suggest that no true threshold exists current understanding of turbulent fluid motion at a sediment bed suggests that some particle movement must occur at all nonzero time mean velocities a combined model for flume flow and sediment transport having no threshold is seen to explain features of data that have been previously used to support the threshold concept

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

the variability of critical shear stress friction angle and grain protrusion in water worked sediments the erodibility of a grain on a rough bed is controlled by among other factors its relative projection above the mean bed its exposure relative to upstream grains and its friction angle here we report direct measurements of friction angles grain projection and exposure and small scale topographic structure on a variety of water worked mixed grain sediment surfaces using a simple analytical model of the force balance on individual grains we calculate the distribution of critical shear stress for idealized spherical grains on the measured bed topography the friction angle projection and exposure of single grain sizes vary widely from point to point within a given bed surface the variability within a single surface often exceeds the difference between the mean values of disparate surfaces as a result the critical shear stress for a given grain size on a sediment surface is characterized by a probability distribution rather than a single value on a given bed the crtitical shear stress distributions of different grain sizes have similar lower bounds but above their lower tails they diverge rapidly with smaller grains having substantially higher median critical shear stresses large numbers of fines trapp ed within pockets on the bed or shielded by upstream grains are effectively lost to the flow our calculations suggest that critical shear stress as conventionally measured is defined by the most erodible grains entrained during transient shear stress excursions associated with the turbulent flow this implies a physical basis for the indeterminacy of initial motion these observations suggest that transport rate shear stress relationships may be controlled in part by the increasing numbers of grains that become available for entrainment as mean shear stress increases they also suggest that bed textures and grain size distributions may be controlled within the constraints of an imposed shear stress and sediment supply regime by the influence of each size fraction on the erodibility of other grain sizes present on the bed

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

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

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

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

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

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

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

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

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

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

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

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

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

the influence of clay on the threshold of movement of fine sandy beds the erosion threshold i e surface shear strength of mixed sediment deposits has been tested under the action of unidirectional currents mean critical speeds 4 mm above the bed ranging from 12 4 cm s 1 to 18 2 cm s 1 or simulated waves mean critical periods ranging from 2 0 s to 6 7 s for near bed wave amplitudes of 0 28 0 57 m using an oscillating tray in a rectangular recirculating flume the sediment mixtures investigated consisted of angular fine grained quartz sands d50 152 5 and 215 m and cohesive estuarine mud the investigation has shown that the cohesive material increases generally the erosion threshold of sandy deposits the rate of increase is smaller for mud contents 30 clay mineral content 11 14 by dry weight and is attributed to an increase of the internal angle of friction when the clay mineral content exceeds 11 14 by dry weight then the sand particles are not in contact with each other consequently the clay component controls the erodibility of the sediment mixture finally a prolonged and intense stress history can increase considerably by a factor of 1 3 1 7 the original erosion threshold value of these sediments

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

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

cohesive material erosion by unidirectional current the initiation of motion of consolidated cohesive sediments under a unidirectional flow of clear water was studied experiments were performed in a flume tunnel capable of providing a bed shear stress up to 26 pa and a velocity of 3 5 m s 3 mm above the bed samples were prepared in a specially designed press using a carefully controlled consolidation procedure critical shear stress and velocity were found to increase with compressive strength vane shear strength plasticity index clay content and consolidation pressure

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

ripple formation in combined transdirectional steady and oscillatory flow measurements are described of the geometry of ripples formed on beds of sand exposed to a steady current at right angles to an oscillatory flow four different sands were studied the oscillation was produced by an oscillating tray set into the bed of a steady flow flume it was observed that straight crested ripples formed by oscillatory flow would usually develop a serpentine form when the superimposed steady current exceeded a certain limit for amplitudes of the tray velocity u less than about 0 38 m s 1 this limit corresponded to u c 31 where c is the shear velocity measured just upstream of the oscillating tray it is suggested that the serpentine form is caused by the interaction of vortices carried back and forth between adjacent ripples on this assumption the wavelength of the serpentine form would be proportional to the product of period of oscillation and near bed steady current velocity the present measurements appear to support this hypothesis although there is also evidence that the wavelength is influenced by preferred spacing patterns between vortices the measurements also show the ratio of the amplitude of the serpentine form to its wavelength to be approximately constant empirical relationships are derived relating ripple geometry to flow and sediment properties it is observed that the influence of reynolds number and sediment properties on the geometry is very weak it is suggested that this is typical of ripples formed with relatively low sediment transport rates it is also found that under the present experimental conditions the ripple spacing in the direction of oscillation is almost independent of the magnitude of the steady current and in close agreement with the wavelengths previously measured in an oscillating water tunnel this suggests that the additional inertia effects associated with oscillating tray rigs were not sufficient to affect bed geometry under the present test conditions

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

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

garnet zoning and reaction textures in overprinted eclogites bohemian massif european variscides a record of their thermal history during exhumation eclogites from different parts of the variscan basement of the bohemian massif show a variation in temperatures recorded at peak pressures as well as during subsequent exhumation these differences are reflected in the extent of modification of pre syn and post eclogite facies garnet compositions and by the types of reactions taking place at garnet rims munchberg massif eclogites formed at conditions of 600 650 c 20 kbar were mainly overprinted in the amphibolite facies field and contain garnets with an old homogeneous core and often well preserved idiomorphic growth zoning to mg rich rims in the marianske lazn complex the eclogite facies stage 640 715 c 15 kbar many eclogites show well developed granulite facies overprints with widespread orthopyroxene growth in garnet and omphacite domains spinel and or sapphirine after kyanite and in some cases even a low pressure high temperature overprint that produced fe rich olivine the latter rocks clearly endured higher temperatures during breakdown but remarkably strong growth zoning and sharp overgrowth features are preserved in some cases diffusion modeling shows that the preservation of zoning in garnet of rocks that have experienced granulite facies temperatures is only possible if the time spent at these conditions is short 1 ma this time scale is inconsistent with a smooth p t t path as expected from thermal modeling for erosion or extension driven exhumation and implies that these variscan rocks experienced short lived thermal events during their exhumation history

threshold studies of gravel size particles under the co linear combined action of waves and currents gravel size sediment beds are tested under the combined influence of simulated wave action and co linear currents in a laboratory flume critical current speed at threshold increases with increasing size superimposed wave energy causes a small reduction in the unidirectional current energy for low values of wave induced near bed current velocities the resistance to erosion increases when the wave period decreases from 10 to 6 s finally combined critical shear stresses are found to be lower than those predicted using the shields curve as modified for oscillatory flow grain protrusion is suggested as a mechanism to explain this divergence

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

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

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

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

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

predicting erosion resistance of muds abstract when measured or apparent yield stress of cohesive muds is assumed to reflect average particle particle bond strength in network structures critical bed shear stress required for grain by grain entrainment can be predicted from an analysis of the forces acting on component grains of geometrically flat mud beds erosion resistance is then defined in terms of cohesive yield stress as well as nominal particle size shape relative density and packing geometry predicted values of critical bed shear stress compare favorably with existing data from selected studies in which appropriate yield stress and hydrodynamic parameters have been reported

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

stability analysis of semicohesive streambanks with concepts coupling field and laboratory investigations to quantify the onset of fluvial erosion and mass failure abstractthe overarching goal of this study is to perform a comprehensive bank stability analysis that is phenomenologically sound by considering both mass failure and fluvial erosion the nature of this study is twofold first field and experimental analyses are conducted to generate data for channel cross section properties soil index properties and mechanical and erosional strengths at two sites in a representative midsize midwestern stream in southeastern iowa that is subjected to frequent flash floods and characterized by active fluvial erosion and cantilever failure second the channel surveys and data obtained from the field and laboratory analyses are used as input parameters for an established one dimensional channel evolution model namely the conservational channel evolution and pollutant transport system concepts version 2 0 langendoen and alonso 2008 to estimate the factor of safety for mass failure fsm and fluvial erosion fsf and simulate the bank retreat as a result of eithe

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

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

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

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

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

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

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

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

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

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