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

stream length gradient hotspot and cluster analysis sl hca to fine tune the detection and interpretation of knickzones on longitudinal profiles abstract this work presents a new approach for fine tuning the analysis of stream longitudinal profiles we show that applying hotspot and cluster analysis hca based on the getis ord gi statistic to the stream length gradient sl index improves the visualization of anomalous values assisting in the identification of tectonic structures and large landslides high positive gi values indicate the clustering of sl anomalies hotspots and mirror the occurrence of knickzones on the stream long profiles we applied this methodology to a mountainous sector of the eastern emilia romagna region in northern italy remote sensing and field surveys conducted on hotspot sites indicate that large landslides are the main process associated to over steepened long profile segments along streams connected to the valley slopes along stream changes in bedrock resistance accounts for the main anomalies within sectors where hillslopes and valley floors are disconnected we demonstrate that specific relationships between geometry and intensity of sl hotspots are indicative of the process responsible for the knickzone formation and in particular that tectonic structures generally provide the longest and highest anomalies the results of this work suggest that sl hca maps are more advantageous for detecting and interpreting knickzones compared with traditional sl maps since i they need less input data to be computed thus making them useful to investigate regions poorly covered by detailed geological data and or where field surveys are difficult to be carried out and ii the hotspot geometry can help discriminate the knickzones attributable to gravitational mass movements from litho structural ones

fault generated mountain fronts in southeast spain geomorphologic assessment of tectonic and seismic activity abstract tectonic activity of se spain is evaluated through the application of a general morphometric analysis over 17 different mountain fronts the selected fronts are distributed along the two most prominent crustal scale structures of the mediterranean sector of spain the eastern betic shear zone ebsz and the valencia trough geomorphic indexes used in this study are mountain front sinuosity index smf and valley floor width ratio vf this work is largely based on the smf vf regression analysis of the studied fronts together with previous available data from sw usa the development of mountain fronts in both different lithologies and tectonic contexts enabled characteristic morphometric signatures for different activity scenarios tectonic activity classes to be obtained this study thus indicates that variations of mountain front geomorphology triggered by different styles of faulting can be detected by morphometric analysis it is demonstrated that discrete uplift rates of 0 15 0 08 m ka are sufficient to keep relatively low smf values down to 1 4 in active fronts class 1 taking into account the reported uplift rates and preliminary palaeoseismic data for some of the class 1 studied fronts recurrence periods for surface rupture events can be theoretically bracketed for se spain recurrence periods for class 1 fronts could theoretically range between 10 000 and 12 500 years for maximum slip conditions and 1750 and 2600 years for minimum slip conditions inactive fronts class 3 develop under uplift rates down to 0 03 m ka and tested recurrence intervals for rupture events range between 25 000 and 50 000 years class 2 fronts of intermediate characteristics and activity display uplift rates between 0 07 and 0 03 m ka

active tectonics and drainage evolution in the tunisian atlas driven by interaction between crustal shortening and mantle dynamics abstract active tectonics in north africa are fundamentally driven by nw se directed slow convergence between the nubia and eurasia plates leading to a region of thrust and strike slip faulting in this paper we analyse the morphometric characteristics of the northern tunisia sector we aim to identify unknown active tectonic structures and to further understand the mechanisms driving the drainage evolution in this region the interpretation of morphometric data was ground truthed with field data our analysis indicates that recent fluvial captures have been the main factor driving fluvial network reorganization in ne tunisia the medjerda river has increased its drainage area during the quaternary by capturing adjacent axial valleys to the north and south of its drainage divide these captures are probably driven by the gradual uplift of adjacent axial valleys by reverse oblique faults or associated folds like el alia teboursouk and dkhila faults our fieldwork found that these faults cut holocene sediments thus showing recent fault activity the growth and stabilization of the axial medjerda river contrary to the natural transverse drainage development of mature orogens might be caused by a combination of crustal shortening structures and mantle dynamic processes the medjerda river flows sw ne from the south atlassic dextral transfer zone to the regional topographic low defined by the gulf of gabes and the straits of sicily which in turn may be influenced by the underlying tunisian slab in the region

the summit erosion surfaces of the inner betic cordillera their value as tools for reconstructing the chronology of topographic growth in southern spain erosion surfaces at the top of mountain ranges have suggested to geomorphologists that the earth s crust can undergo rapid pulses of uplift during which rates of denudation fail to balance with rates of crustal uplift thereby preserving much of the initial plateau topography as it rises to greater elevations here we analyze a regionally extensive population of mappable planar surfaces which crown several major tectonically active sierras of the inner south eastern betic cordillera se spain based on a synthesis of long term landscape evolution involving landform reconnaissance dem based morphometric analysis structural geology sediment provenance analysis and field stratigraphy we conclude that the summit surfaces are a mosaic of discrete post orogenic erosion surfaces that each developed in relation to mediterranean marine base levels at a time when the sierras formed a series of low elevation islands they are not therefore fragments of a once regionally continuous paleoplain the summit surfaces were partly the result of shallow angle detachment faulting during the middle miocene in response to lithospheric slab detachment where evidence exists that the resulting low relief topography was reworked by marine abrasion during the tortonian sea level rise the terminal age of the surfaces is latest miocene age bracketing based on stratigraphic correlations among the many depocentres of the region and on published thermochronological data indicates that some erosion surfaces locally formed in less than 3 million years 8 ma 5 7 ma they were subsequently uplifted to their current elevations 1 7 to 2 km by pliocene to quaternary neotectonics in at least two major pulses

influence of chemical denudation on hillslope morphology 1 models of hillslope evolution involving diffusion like sediment transport are conventionally presented as an equation in which the changes in land surface elevation or soil thickness are balanced by the divergence of soil transport and tectonic uplift soil production or both these models typically do not include the loss or gain of mass in hillslope soils due to processes of chemical weathering and deposition we formulate a more general depth integrated equation for the conservation of soil mass on a hillslope that includes a term representing chemical deposition or denudation this general depth integrated equation is then simplified to determine the one dimensional form of a steady state hillslope which experiences both mechanical and chemical denudation the differences in morphology between hillslopes only experiencing diffusion like mechanical sediment transport and hillslopes experiencing both diffusion like mechanical sediment transport and chemical denudation are explored under the conditions of a downslope increase in local soil lowering rate due to chemical weathering the hillslope profile will depart from the parabolic shape predicted by models that incorporate only linear diffusion like mechanical sediment transport in addition hillslopes that experience both chemical and mechanical denudation may have a convex concave profile at steady state a necessary condition for such steady state profiles is that the chemical denudation rate must exceed the mechanical denudation rate we further suggest that combinations of other physical parameter values such as total denudation rate average soil depth sediment diffusivity and the increase in soil depth away from the divide that lead to steady state convex concave hillslope profiles may exist in a wide variety of natural settings

palaeostress analysis of the northern nijar and southern vera basins constraints for the neogene displacement history of major strike slip faults in the betic cordilleras se spain this paper presents the results of a detailed structural analysis of the northern nijar and southern vera basins with special emphasis on the evolution of the regional stress field and the associated timing of movement of the serrata gafarillos and palomares strike slip fault zones these major fault zones control the neogene deformation of the se internal betic cordilleras in spain detailed stress analysis on neogene sediments of the vera and nijar basins shows a strike slip regime with nw se oriented subhorizontal maximum principal stress 1 during tortonian and earliest messinian times under the influence of this stress field dextral displacement along the n090e trending gafarillos fault zone resulted in deformation of the sediments of the southern sorbas and northeastern nijar basins during the early messinian a clock wise rotation of the stress field occurred stress analysis in rocks with late early messinian up to quaternary ages in the nijar and vera basins indicates a strike slip regime with n s oriented subhorizontal maximum principal stress 1 under the influence of this stress field the main activity along the n010e striking palomares strike slip fault zone took place resulting in deformation of the neogene sediments of the southeastern vera basin and culminating in a maximum sinistral displacement of more than 20 km at the same time the stress field was not suitably oriented to exert a large shear component on the gafarillos fault zone which activity ended after the earliest messinian fault and outcrop patterns of syntectonic neogene sediments in the vera basin show that displacement along the palomares fault zone decreased at the end of the middle miocene although minor displacement phases may still have occurred during the late miocene and possibly even pliocene from the middle miocene onward deformation in the nijar basin was controlled by sinistral displacement along the n040e trending serrata strike slip fault zone

geomorphically driven late cenozoic rock uplift in the sierra nevada california geologists have long accepted that the sierra nevada california experienced significant late cenozoic tectonically induced uplift a flexural isostatic model presented here shows however that a large fraction of the primary evidence for uplift could be generated by the lithospheric response to coupled erosion of the sierra nevada and deposition in the adjacent central valley and therefore requires less tectonic forcing than previously believed the sum of range wide erosion and the resultant isostatic rock uplift would have lowered sierra mean elevation by 200 to 1000 meters since 10 million years ago and could also have increased summit elevations during the current period of relief production

kinematics of the western africa eurasia plate boundary from focal mechanisms and gps data summary the western mediterranean displays a complex pattern of crustal deformation distributed along tectonically active belts developed in the framework of slow oblique plate convergence we used earthquake and global positioning system gps data to study the present day kinematics and tectonics of the africa eurasia plate boundary in this region crustal seismicity and focal mechanisms analysed in terms of seismic moment release and seismic deformation outline the geometry of major seismic belts and characterize their tectonics and kinematics continuous gps data have been analysed to determine euler vectors for the nubian and eurasian plates and to provide the global frame for a new mediterranean gps velocity field obtained by merging continuous and campaign observations collected in the 1991 2005 time span gps velocities and displacements predicted by the nubia eurasia rotation pole provide estimates of the deformation accommodated across the tectonically active belts the rather simple deformation occurring in the atlantic region characterized by extension about perpendicular to the middle atlantic and terceira ridges and right lateral motion along the gloria transform fault turns into a complex pattern of deformation occurring along broader seismic belts where continental lithosphere is involved our analysis reveals a more complex fragmentation of the plate boundary than previously proposed the roughly e w trending mainly compressive segments i e southwestern iberia northern algeria and southern tyrrhenian where plate convergence is largely accomodated across rather localized deformation zones and partially transferred northward to the adjacent domains i e the algero balearic and tyrrhenian basins are interrupted by regions of more distributed deformation i e the rif alboran betics tunisia libya and eastern sicily or limited seismicity i e the strait of sicily which are characterized by less homogeneous tectonics regimes mainly transcurrent to extensional in correspondence of the observed breaks tectonic structures with different orientation interfere and we find belts with only limited deformation i e the high and middle atlas the tunisian atlas and the offshore tunisia libya belt that extends from the plate boundary into the nubian plate along pre existing tectonic lineaments our analysis suggest that the sicilian pelagian domain is moving independently from nubia according to the presence of a right lateral and extensional decoupling zone corresponding to the tunisia libya and strait of sicily deformation zone despite the space variability of active tectonic regimes plate convergence still governs most of the seismotectonic and kinematic setting up to the central aeolian region in general local complexities derive from pre existing structural features inherited from the tectonic evolution of the mediterranean region on the contrary along calabria and the apennines the contribution of the subducted ionian oceanic lithosphere and the occurrence of microplates i e adria appear to substantially modify both tectonics and kinematics finally gps data across the gibraltar arc and the tyrrhenian calabria domain support the hypothesis that slab rollback in these regions is mostly slowed down or stopped

adjustment of a drainage network to capture induced base level change an example from the sorbas basin se spain abstract quaternary catchments in the south of the sorbas basin se spain have been affected by two regionally significant river captures the river captures were triggered by changes in regional gradients associated with sustained quaternary uplift in the region of 160 m ma 1 the first capture occurred in the early pleistocene and re routed 15 of the original sorbas basin drainage into the carboneras basin to the south the second occurred in the late pleistocene and re routed 73 of the original sorbas basin drainage to the east this latter capture had dramatic consequences for base level in the sorbas basin master drainage local base level was lowered by 90 m at the capture site 50 m at 7 km upstream and 25 m at 13 km upstream of the site the base level change instigated a complex re organisation of the drainage networks in systems tributary to the master drainage over the ensuing period some 100 ka after the capture drainage systems closer to the capture site experienced a tenfold increase in incision rates over most of their network those located some 13 km upstream of the capture site experienced a fivefold increase in incision although in this instance the changes do not appear to have propagated to the headwater regions of the drainage nets the sensitivity of individual catchments was largely governed by geological controls structure and lithology the detailed network evolution in the most sensitive areas can be traced by reconstructing former drainage pathways using abandoned drainage cols and the alignment and degree of incision of the drainage networks three main stages of evolution can be identified which record the progressive spread of base level changes from the master drainage these are stage 1 pre capture original south to north consequent drainage stage 2 early stage post capture aggressive subsequent southwest to northeast and east west drainage developed along structural lineaments first in the east of the area stage 2a and later in the west of the area stage 2b and stage 3 late stage post capture obsequent drainage developing on the topography of the stage 2 drainage all stages of the network evolution are associated with drainage re routing as a function of river capture at a variety of scales the results highlight the complex response of the fluvial system and the very different geomorphological histories of adjacent catchments emphasising the need for regional approaches for examining long term changes in fluvial systems

deformation in neogene sediments of the sorbas and vera basins se spain constraints on simple shear deformation and rigid body rotation along major strike slip faults abstract detailed structural analyses are presented of the neogene sorbas basin adjacent to the e w striking gafarillos fault zone and the vera basin adjacent to the 020 striking palomares fault zone in southeastern spain a stress regime with an e w oriented subhorizontal maximum principal stress 1 existed in pre tortonian 11 3 ma time a strike slip regime with nw se oriented compression during tortonian and earliest messinian time caused dextral displacement along the e w trending gafarillos fault of approximately 10 km structural analysis indicates that most displacement took place in the early tortonian deformational patterns within the adjacent pull apart basin reflect a dextral simple shear zone of at least 500 m width kinematical analysis of folds in the sorbas basin suggests however that rotational effects are largely caused by rigid body rotation without much internal deformation sinistral strike slip displacements occurred along the palomares fault zone under the influence of the same stress regime an abrupt change in the orientation of the stress field to n s directed compression in earliest messinian time 6 5 ma caused the termination of displacements along the gafarillos fault zone whereas the 020 trending palomares fault zone continued to accumulate sinistral strike slip displacements of about 25 km volcanism occurred along splays of the fault zone a wider shear zone of a few kilometers width evolved in which considerable anti clockwise rotation of folds occurred kinematic analysis of these folds shows that these rotational effects are again dominantly rigid body rotations assuming rotations are merely caused by simple shear deformation overestimates the amounts of strain a better way to deal with simple shear deformation is to compare observed shortening caused by folding with the magnitude of rotation of fold hinges

geomorphology and neogene tectonic evolution of the palomares continental margin western mediterranean abstract the palomares continental margin is located in the southeastern part of spain the margin main structure was formed during miocene times and it is currently part of the wide deformation zone characterizing the region between the iberian and african plates where no well defined plate boundary occurs the convergence between these two plates is here accommodated by several structures including the left lateral strike slip palomares fault the region is characterized by sparse low to moderate magnitude mw

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

from extension to transpression quaternary reorganization of an extensional related drainage network by the alhama de murcia strike slip fault eastern betics abstract the complex present day drainage network of the lorca totana area records the changing tectonic setting from extension to transpression in the eastern betics through a detailed morphometric analysis we evaluate the topographic response to this major change in the tectonic setting and the influence in the drainage of miocene extension and middle pleistocene to present day transpression the present day drainage network preserves geomorphic features inherited from late miocene extension that are being overprinted by a new transverse fluvial system this new system advanced towards the nw since the middle pleistocene in response to a localized base level drop related to the ne sw oriented alhama de murcia sinistral reverse fault geomorphic indexes calculated in this work suggest the present day activity of the alhama de murcia fault and the sierra de la tercia anticline the two major tectonic structures in the area the landscape rejuvenation associated with this process results in contrasting mountain front sinuosity values between old and new mountain fronts high slk index anomalies convex shaped and complex hypsometric curves knickpoints in river profiles contrasting slope area plots and high steepness index values this fluvial reorganization was driven progressively by successive fluvial captures preserved as wind gaps in the present day drainage network

the timing of quaternary calcrete development in semi arid southeast spain investigating the role of climate on calcrete genesis quaternary aged calcrete horizons are common weathering products in arid and semi arid regions it is however unclear how calcrete forming processes respond to the major oscillations in climate that occur over the quaternary period this paper presents a u series based calcrete age database from the sorbas basin southeast spain the study constructs an age frequency distribution of these ages which is consequently compared to a range of palaeoenvironmental records from the mediterranean the age distribution presented here suggests that the formation of pedogenic calcrete horizons in the sorbas basin primarily occurs during warm isotope stages mis 1 and 5 with very few calcrete ages occurring during cold glacial stadial stages mis 2 3 and 4 it is suggested that this is a function of the environments that existed during warm isotope stages being more conducive to calcrete development than those that existed during cold climate episodes in a semi arid region such as the sorbas basin it is likely that increased aridity during glacial stages coupled with reduced vegetation and accelerated landscape instability was crucial in reducing rates of calcrete formation in a semi arid region such as southeast spain calcrete formation during the quaternary therefore oscillates with climate change but is primarily a warm episode phenomenon it is suggested that further studies are required to see how calcrete genesis responds to environmental change in more humid parts of the mediterranean

the structural evolution of active fault and fold systems in central otago new zealand evidence revealed by drainage patterns abstract central otago in new zealand is an area of active continental shortening in which a peneplain surface cut into schist has been deformed by folds which are developed above buried reverse faults we use the drainage patterns in this region to demonstrate various processes in fold and fault growth and interaction that would be difficult to identify by other means in particular we show 1 how simple asymmetric folds can develop into box folds 2 how apparently continuous ridges were formed by the coalescing of quite separate propagating fold and fault segments 3 evidence for the relative ages or relative uplift rates of adjacent structures and 4 evidence for the propagation direction of folds or faults as they grow the few quantitative estimates we obtain for fault propagation rates suggest an increase in length of 10 50 m per earthquake on faults about 20 km long these estimates are very uncertain but are similar in magnitude to an estimate made in nevada for a normal fault of similar size and are also similar to predicted estimates from theoretical growth models they raise the question of whether fault growth earthquake recurrence rates and climate change can interact to produce semi regular discrete features in an active landscape

compressional tectonic inversion of the algero balearic basin latemost miocene to present oblique convergence at the palomares margin western mediterranean interpretation of new multichannel seismic reflection profiles indicates that the palomares margin was formed by crustal scale extension and coeval magmatic accretion during middle to late miocene opening of the algero balearic basin the margin formed at the transition between thinned continental crust intruded by arc volcanism and back arc oceanic crust deformation produced during the later positive inversion of the margin offshore and onshore is partitioned between n50 e striking reverse faults and associated folds like the sierra cabrera and abubacer anticlines and n10 20 e sinistral strike slip faults like palomares and terreros faults parametric subbottom profiles and multibeam bathymetry offshore structural analysis available gps geodetic displacement data and earthquake focal mechanisms jointly indicate that tectonic inversion of the palomares margin is currently active the palomares margin shows a structural pattern comparable to the north maghrebian margins where africa eurasia plate convergence is accommodated by ne sw reverse faults nnw sse sinistral faults and wnw ese dextral ones contractive structures at this margin contribute to the general inversion of the western mediterranean since 7 ma coeval to inversion at the algerian margin shortening at the alboran ridge and al idrisi faults occurred later since 5 ma indicating a westward propagation of the compressional inversion of the western mediterranean

slab rupture and delamination under the betics and rif constrained from receiver functions abstract we map the lithospheric structure under the westernmost mediterranean convergent setting interpreting p receiver functions obtained from a dense seismic network no orogenic root occurs under the eastern and great part of the central betics however the subducted south iberian continental lithosphere is found beneath the western betics where the iberian moho reaches depths of approximately 65 km dipping gently towards the se meanwhile at the rif strong crustal and lithospheric thickness contrasts occur across the nekor nw se sinistral fault that overlies the region of present slab tearing east of the nekor fault there is no orogenic root and the crust has been thinned to approximately 22 km whilst to the west the crust reaches 55 km thickness and the maghrebian continental lithosphere is attached to the lithospheric slab imaged by tomography under the alboran basin these data suggest that subduction rollback under the alboran and algerian basins together with continental slab tearing or detachment producing edge delamination under the betics and rif have been the main tectonic mechanisms driving extension magmatism and regional uplift in the westernmost mediterranean since the late miocene until present the surface expression of edge delamination and slab tearing is marked by regional uplift denudation of hp rocks in elongated core complex type domes late miocene volcanism in the eastern betics and rif and by large ne sw strike slip transfer faults like the alpujarras crevillente torcal or nekor faults that accommodate strong gradients in crustal displacements the iberian slab is still attached to the oceanic slab imaged under the alboran basin at the western betics where intermediate depth seismicity recent dextral strike slip faulting and folding could reflect slab tearing meanwhile active faulting and differential gps measured displacements would mark slab tearing beneath the rif coinciding with the trace of the sinistral nekor fault

seismic velocity modelling of the carboneras fault zone se spain abstract the carboneras fault zone forms part of a major strike slip fault system in se spain striking ne sw and accommodating up to 40 km displacement it affects basement metamorphic rocks and unconformably overlying upper miocene sediments and volcanic rocks high resolution shallow seismic tomographic sections were made across the fault zone in two localities from the same areas fault rocks and their wallrocks were collected for laboratory seismic velocity measurements the laboratory data were corrected for the substantial effects of near surface crack damage by combining these results with geological cross sections forward velocity models for the fault zone were constructed to compare with field seismic measurements and hence to ground truth the inferences made from them these velocity depth relationships matched moderately well with those extracted from the in situ tomography results aspects of the in situ seismic sections matched features on the forward modelled sections but the comparisons showed that it is important to have some degree of foreknowledge of the geology to be able successfully to interpret seismic tomography sections as an exploration tool

geomorphic analysis of the sierra cabrera an active pop up in the constrictional domain of conjugate strike slip faults the palomares and polopos fault zones eastern betics se spain the nne ssw sinistral palomares and the conjugate dextral wnw ese striking polopos fault zones terminate in the sierra cabrera antiform in order to test the quaternary activity and topographic relief control in the termination of these fault zones here we present new qualitative and quantitative geomorphic analyses supported by a new structural map of the region the main mountain fronts of the cabrera antiform are formed by the north and south cabrera reverse faults that merge laterally into the palomares and polopos faults respectively these faults produce knickpoints stream deflections complex basin hypsometric curves high slk anomalies and highly eroded basins in their proximity furthermore the drainage network shows an s shaped pattern reflecting progressive anticlockwise rotation related to the sinistral palomares fault zone the estimated uplift rates determined by the integration between mountain front sinuosity index and valley floor width to height ratio are larger than those obtained for strike slip faults in the eastern betics these larger uplift rates with our geomorphic and structural dataset indicate that the topographic relief of the sierra cabrera antiform is controlled by reverse faults that form a pop up structure in the constrictional domain between the larger palomares polopos conjugate strike slip faults existing gps geodetic data suggest that the north and south cabrera reverse faults probably accommodate a large part of africa iberia convergence in the region

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

extensional tectonics in the northeastern betics se spain case study of extension in a multilayered upper crust with contrasting rheologies extension in the northeastern betics took place along two main directions corresponding to a minimum of two successive orthogonal extensional systems with n nw and w sw sense of shear respectively strain was strongly localised within weaker metapelites and gypsum leading to the development of several extensional detachments which accommodated the thinning produced by extensional ramps and listric faults within the stronger carbonate rocks extension along several detachments led to the preservation in a single thinned section of layers representative of different crustal depths of a previously thickened upper crust the n to nw directed extensional system was formed by brittle to brittle ductile detachments which were active during the upper oligocene and lower miocene coeval to vertical ductile thinning of underlying greenschist facies metamorphic rocks the w to sw directed extensional system active during the middle and upper miocene shows multiple slip surfaces which transferred displacement to a brittle detachment with a ramp flat geometry that stepped down into the footwall of the previous nw directed system the geometry of both extensional systems was determined by the rheological heterogeneity of the studied crustal section further upper miocene extension was accommodated by radial extension with a dominant set of sw directed listric faults which tilted the aforementioned detachments and exhumed them in the core of km scale elongated extensional domes

astrochronology for the messinian sorbas basin se spain and orbital precessional forcing for evaporite cyclicity the sorbas basin of se spain contains one of the most complete sedimentary successions of the mediterranean reflecting the increasing salinity during the messinian salinity crisis a detailed cyclostratigraphic study of these successions allows a correlation of the sedimentary cycle patterns to astronomical target curves here we present an astrochronological framework for the messinian of the central part of the sorbas basin this framework will form a solid basis for high resolution correlations to the marginal carbonate facies and to the central mediterranean area the early messinian abad member contains 55 precession induced sedimentary cycles marked by homogeneous marl opalrich bed alternations in the lower abad and by homogeneous marl sapropel alternations in the upper abad astronomical tuning results in an age of 5 96 ma for the transition to the yesares evaporites and thus for the onset of the messinian salinity crisis the marl sapropel cycles of the upper abad are replaced by gypsum sapropel cycles 14 in the yesares member indicating that the evaporite cyclicity is related to precession controlled oscillations in circum mediterranean climate as well as a consequence gypsum beds correspond to precession maxima insolation minima and relatively dry climate sapropelitic marls to precession minima insolation maxima and relatively wet climate an alternative glacio eustatic obliquity control for evaporite cyclicity can be excluded because the number of sedimentary cycles with a reversed polarity is too high sedimentation during the abad yesares and the overlying coastal sequences of the sorbas member took place in a continuously marine environment indicating that marine conditions in the sorbas basin prevailed at least until 5 60 5 54 ma according to our scenario deposition of the yesares and sorbas member took place synchronously with deposition of the lower evaporites in the central mediterranean finally the continental zorreras member consists of 8 sedimentary cycles of alternating reddish silts dry climate and yellowish sands wet climate which correlates very well with the upper evaporites and lago mare facies of the mediterranean q 2001 elsevier science b v all rights reserved

geomorphic evidence of active tectonics in the sierra alhamilla eastern betics se spain abstract active tectonic deformation influencing the streams and hillslopes of the sierra alhamilla ridge anticlinorium in southeast spain is related to the dextral reverse polopos fault zone to the north and east of the ridge and to normal faulting in the southern side of the ridge a fault segmentation and fluvial terrace mapping is presented in this paper the following geomorphic indices were calculated in the area the mountain front sinuosity valley floor width to height ratio drainage basin asymmetry factor basin hypsometric curve and integral longitudinal river profile and stream length gradient index normalized by the graded river gradient slk index the slk map shows two sets of high anomalies a an e w striking anomaly due to the dextral reverse polopos fault zone located in the northern limb of the anticlinorium b a group of nnw sse striking anomalies associated with pliocene quaternary nw se to nnw sse striking high angle normal faults that cut the southern limb late pleistocene holocene activity occurred along the north alhamilla reverse fault and the dextral transpressive south gafarillos fault two segments in the polopos fault zone the former fault produces rejuvenation of the streams at the base of the northern slope in this area mountain front sinuosity and valley floor width to height ratio suggest quaternary uplift rates between 0 05 and 0 5 m ky 1 holocene to present day activity of the south gafarillos fault is demonstrated by faulted late pleistocene terraces and holocene colluvial deposits and suggested by deflected streams that have complex or convex hypsometric curves pliocene quaternary high angle normal faults control the relief in the southern limb and the western end of the sierra alhamilla these faults produce low mountain front sinuosity and valley floor width to height ratio indices typical of uplift rates quite higher than field based rates from some other studies

mountain front migration and drainage captures related to fault segment linkage and growth the polopos transpressive fault zone southeastern betics se spain abstract the polopos e w to ese wnw oriented dextral reverse fault zone is formed by the north alhamilla reverse fault and the north and south gafarillos dextral faults it is a conjugate fault system of the sinistral nne ssw palomares fault zone active from the late most tortonian 7 ma up to the late pleistocene 70 ky in the southeastern betics the helicoidal geometry of the fault zone permits to shift se directed movement along the south cabrera reverse fault to nw directed shortening along the north alhamilla reverse fault via vertical gafarillos fault segments in between since the messinian fault activity migrated southwards forming the south gafarillos fault and displacing the active fault related mountain front from the north to the south of sierra de polopos whilst recent activity of the north alhamilla reverse fault migrated westwards the polopos fault zone determined the differential uplift between the sierra alhamilla and the tabernas sorbas basin promoting the middle pleistocene capture that occurred in the southern margin of the sorbas basin continued tectonic uplift of the sierra alhamilla polopos and cabrera anticlinoria and local subsidence associated to the palomares fault zone in the vera basin promoted the headward erosion of the aguas river drainage that captured the sorbas basin during the late pleistocene

ocean variability over the agulhas bank and its dynamical connection with the southern benguela upwelling system 1 this study analyzes the oceanic pathway connecting the agulhas bank to the southern benguela upwelling system by means of a quantitative lagrangian interpretation of the velocity field calculated by a high resolution numerical simulation of the ocean around the southwestern tip of africa the regional ocean model is forced with national centers for environmental prediction surface winds over 1993 2006 and offers a relevant numerical platform for the investigation of the variability of the water transferred between both regions both on seasonal and intraseasonal time scales we show that the intensity of the connection fluctuates in response to seasonal wind variability in the west coast upwelling system whereas intraseasonal anomalies are mostly related to the organization of the eddy field along the southwestern edge of the agulhas bank though the study only considers passive advection processes it may provide useful clues about the strategy adopted by anchovies in their selection of successful spawning location and period the pathway under investigation is of major interest for the ecology of the southern benguela upwelling system because it connects the spawning grounds on the agulhas bank with the nursery grounds located on the productive upwelling off the west coast

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

active faulting offshore se spain alboran sea implications for earthquake hazard assessment in the southern iberian margin the southern margin of the iberian peninsula hosts the convergent boundary between the european and african plates the area is characterised by low to moderate magnitude shallow earthquakes although large historical events have also occurred in order to determine the possible sources of these events we recently acquired swath bathymetry tobi sidescan sonar and high resolution seismic data on the almeria margin eastern alboran sea the new dataset reveals the offshore continuation of the ne sw trending carboneras fault a master fault in the eastern betic shear zone and its associated structures n150 and ns faults these structures are active since they cut the late quaternary sedimentary units the submarine carboneras fault zone is 100 km long 5 10 km wide and is divided into two n045 and n060 segments separated by an underlapping restraining stepover geomorphic features typically found in subaerial strike slip faults such as deflected drainage water gaps shutter ridges pressure ridges and ben echelonq folds suggest a strike slip motion combined with a vertical component along the submarine carboneras fault considering the nnw sse regional shortening axis a left lateral movement is deduced for the carboneras fault whereas right lateral and normal components are suggested for the associated n150 and ns faults respectively the offshore portion of this fault is at least twice as long as its onshore portion and together they constitute one of the longest structures in the southeastern iberian margin despite the fact that present day seismicity in the almeria margin seems to be associated with the n150 to ns faults the carboneras fault is a potential source of large magnitude mw 7 2 events hence the carboneras fault zone could pose a

seismic sources on the iberia african plate boundary and their tectonic implications the plate boundary between iberia and africa has been studied using data on seismicity and focal mechanisms the region has been divided into three areas a the gulf of cadiz b the betics alboran sea and northern morocco and c algeria seismicity shows a complex behavior large shallow earthquakes h 30 km occur in areas a and c and moderate shocks in area b intermediate depth activity 30 h 150 km is located in area b the depth earthquakes h 650 km are located to the south of granada moment rate slip velocity andhvalues have been estimated for shallow shocks and show similar characteristics for the gulf of cadiz and algeria and quite different ones for the central region focal mechanisms of 80 selected shallow earthquakes 8 mb 4 show thrust faulting in the gulf of cadiz and algeria with horizontal nnw sse compression and normal faulting in the alboran sea with e w extension focal mechanisms of 26 intermediate depth earthquakes in the alboran sea display vertical motions with a predominant plane trending e w solutions for very deep shocks correspond to vertical dip slip along n s trends frohlich diagrams and seismic moment tensors show different behavior in the gulf of cadiz betic alboran sea and northern morocco and northern algeria for shallow events the stress pattern of intermediate depth and very deep earthquakes has different directions vertical extension in the nw se direction for intermediate depth earthquakes and tension and pressure axes dipping about 45 o for very deep earthquakes regional stress pattern may result from the collision between the african plate and iberia with extension and subduction of lithospheric material in the alboran sea at intermediate depth the very deep seismicity may be correlated with older subduction processes

late neogene recent uplift of the cabo de gata volcanic province almeria se spain abstract cabo de gata is a miocene volcanic province in the betic cordillera in southeastern spain the distribution of coastal deposits in the successive marine sedimentary units overlying the last volcanic episode about 7 5 ma old has been used to reconstruct the post volcanic palaeogeographic evolution of the region during the late neogene the current elevation of well dated shoreline marker rocks has been used to estimate uplift amount and rates since the late tortonian a n45 e aligned the strike of the carboneras fault system topographic relief was emergent in the cabo de gata region the extension and height of this island increased throughout the late neogene smaller independent islands were emergent and finally became connected to the main island during the messinian the carboneras and agua amarga pliocene sub basins were the last two marine basins prior to the final emergence of the region since the last volcanic eruption ca 7 5 ma maximum uplift of sedimentary rocks in cabo de gata has taken place on the western margin of the n45 e aligned palaeorelief the altitude of the shoreline marker rocks in the successive sedimentary units decreases eastwards to the present day coast and northwards of the rambla del plomo uplift rates since deposition remain nearly constant for the successive messinian rocks and decrease slightly for the lower pliocene outcrops most of the uplift took place before the pliocene while the main island enlarged uplift amounts and rates since deposition of the upper neogene sedimentary units in the cabo de gata area are similar to the ones estimated for laterally equivalent units in the eastern betic basins approximately 50 m ma despite its volcanic nature and the occurrence of the carboneras fault system the cabo de gata probably became elevated as a consequence of regional uplift in connection with the rest of the betic cordillera

ubiquitous low velocity layer atop the 410 km discontinuity in the northern rocky mountains receiver functions from three 30 station iris passcal small aperture arrays 2 15 km station spacing operated for 10 months each in the northern rocky mountains show a ubiquitous negative polarity p to s conversion just preceding the 410 km discontinuity arrival data from the three arrays were sorted into nw se and sw back azimuth quadrants and stacked to form nine quadrant stacks remarkably the negative polarity arrival npa is apparent in 8 of the 9 quadrant stacks with 7 of the 8 having well correlated waveforms each quadrant stack also contains clear p to s conversions from the 410 and 660 km discontinuities moveout analysis shows that all the major phases display the correct moveout for forward scattered p s phases the waveshapes for the seven similar npa 410 km discontinuity arrivals are modeled with a five parameter double gradient slab model that is parameterized as follows a top gradient thickness and shear velocity decrease a constant velocity layer bottom gradient thickness and shear velocity increase model misfit is assessed via a grid search over the model space using a reflectivity code to calculate synthetic seismograms model likelihood is determined by calculating 1 and 2 d marginal probability density functions pdf for the five parameters the 1 d marginals display a range of peak values although significant overlap is observed for the top gradient thickness and its associated velocity decrement from the peak value of the summary pdf we find the top velocity gradient to be sharp 6 4 km and the shear velocity decrement to be large 8 9 vs defining an effective thickness of the low velocity layer as the mean layer thickness plus half the mean gradient thicknesses the 410 low velocity layer thickness is found to be 22 km a review of changes in the physical state required to match our new 410 lvl constraints suggests that the water filter model remains an operative hypothesis to test

u series isochron dating of immature and mature calcretes as a basis for constructing quaternary landform chronologies for the sorbas basin southeast spain immature and mature calcretes from an alluvial terrace sequence in the sorbas basin southeast spain were dated by the u series isochron technique the immature horizons consistently produced statistically reliable ages of high precision the mature horizons typically produced statistically unreliable ages but because of linear trends in the dataset and low errors associated with each data point it was still possible to place a best fit isochron through the dataset to produce an age with low associated uncertainties it is however only possible to prove that these statistically unreliable ages have geochronological significance if multiple isochron ages are produced for a single site and if these multiple ages are stratigraphically consistent the geochronological significance of such ages can be further proven if at least one of the multiple ages is statistically reliable by using this technique to date calcretes that have formed during terrace aggradation and at the terrace surface after terrace abandonment it is possible not only to date the timing of terrace aggradation but also to constrain the age at which the river switched from aggradation to incision this approach therefore constrains the timing of changes in fluvial processes more reliably than any currently used geochronological procedure and is appropriate for dating terrace sequences in dryland regions worldwide wherever calcrete horizons are present

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

plio pleistocene drainage development in an inverted sedimentary basin vera basin betic cordillera se spain abstract the vera basin is one of a series of interconnected neogene quaternary sedimentary basins located within the internal zone of the betic cordillera southeast spain since the pliocene the vera basin has been subjected to low uplift rates 11 21 m ma 1 and inverted via compressive tectonics that are related to the ongoing oblique collision between the african and iberian plates within this paper the sedimentary and geomorphic response to basin inversion is explored sedimentary processes and environments are established for key stratigraphic units of the pliocene plio pleistocene basin fill and pleistocene dissectional landscape these data are subsequently utilised to reconstruct an evolving basin palaeogeography fault and uplift data are employed to discuss the role of tectonically driven basin inversion for controlling the resultant palaeogeographic changes and associated patterns of drainage development during the early mid pliocene the vera basin was characterised by shallow marine shelf conditions cuevas formation a major palaeogeographic reorganisation occurred during the mid late pliocene strike slip movement along the eastern basin margin coupled with uplift and basin emergence created a protected partially enclosed marine embayment that was conducive for gilbert type fan delta sedimentation from fluvial inputs along the northern and eastern basin margins espiritu santo formation the vera basin then became fully continental and internally drained through the development of a consequent drainage network that formed following the withdrawal of marine conditions during the late pliocene to early pleistocene alluvial fans developed along the northern and western basin margins grading to a bajada and terminating in a playa lake in central basin areas salmeron formation during the early mid pleistocene a switch from basin infilling to dissection took place recorded by alluvial fan incision a switch to braided river sedimentation and fluvial incision into the underlying basin fill sediments and basin margin mountainous topography fluvial incision headwards erosion expansion and modification of the consequent drainage network is documented within a series of up to four major inset river terrace levels and associated landforms fluvial incision and drainage network expansion are attributed to differential uplift and the creation of regional gradients between adjacent basins the relatively low plio pleistocene uplift rate of the vera basin 11 21 m ma 1 in comparison to adjacent basins sorbas 80 160 m ma 1 huercal overa 50 m ma 1 resulted in a switch from internal to external basin drainage ancestral forms of the principal drainage systems within the vera basin the rios almanzora aguas and antas captured basins and mountain catchment areas to the north huercal overa basin southwest sorbas basin and west sierra de los filabres range the switch from basin infilling to fluvial dissection is coincident with a phase of early mid pleistocene compressional tectonics expressed by extensional faulting this deformation is probably linked to accelerated strike slip movement along the palomares fault zone the faulting is superimposed onto the longer term pattern of plio pleistocene uplift and basin inversion

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

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

evaluation of the relative tectonic activity in the eastern lake van basin east turkey abstract the eastern part of the lake van basin van region turkey is controlled by reverse faults such as the gurpinar everek and alakoy faults these represent the major tectonic structures within the van region and have caused many devastating earthquakes based on quantitative analyses the quaternary activity and topographic relief control of each of these faults was investigated the gurpinar everek and alakoy faults are restricted to the southern slopes of the guzelsu everek and karasu basins respectively analyses of the mountain front sinuosity smf and valley floor width to height ratio vf suggest high activity along the gurpinar fault the everek fault and the western part of the alakoy fault furthermore based on the integration between smf and vf the estimated uplift rates were observed to increase from north to south the gurpinar and everek hanging wall blocks are characterized by uplift rates of 0 5 mm yr 1 whereas the alakoy fault exhibited a rate of 0 05 to 0 5 mm yr 1 these faults produce knickpoints or knickzones complex basin hypsometric curves and high values of the stream length gradient index based on these geomorphic analyses it was established that the tectonic activity of both the gurpinar and everek faults is greater than that of the alakoy fault

mineral specific chemical weathering rates over millennial timescales measurements at rio icacos puerto rico abstract mineral weathering plays a prominent role in many biogeochemical and geomorphological processes it supplies nutrients to soils and streams accelerates physical erosion by weakening bedrock and producing easily erodible soil and modulates earth s long term climate by drawing down atmospheric carbon dioxide we calculate mineral specific chemical weathering rates at two field sites in the rio icacos catchment puerto rico by combining new mineral abundance measurements from quantitative powder x ray diffraction xrd with existing measurements of i soil production rates from cosmogenic nuclides ii chemical alteration of the regolith from x ray fluorescence xrf and iii dust deposition rates the central purpose of this paper is to show that combining measurements of cosmogenic nuclides with xrf based geochemistry and xrd based mineralogy can in favorable cases provide weathering rates of abundant soluble mineral phases in actively eroding terrain to an accuracy of better than 20 of the mean even in places with high dust deposition rates mineral weathering at our two field sites is dominated by plagioclase at rates of 3274 575 mol ha 1 yr 1 and 3077 541 mol ha 1 yr 1 followed by hornblende at 187 71 mol ha 1 yr 1 and 308 93 mol ha 1 yr 1 within the uncertainty of our data all weathering of these primary minerals occurs below the saprolite soil interface our measurements imply that kaolinite production in saprolite is roughly 1 3 times faster than kaolinite weathering in the soil our results are the first to show that field measurements of cosmogenic nuclides xrf xrd and dust fluxes can be combined within the geochemical mass balance method to quantify long term mineral weathering rates even in locations with high dust deposition rates this implies that the mass balance method can be a valuable tool for quantifying the effects of climate vegetation tectonics and other factors on weathering rates of individual mineral phases

neogene evolution of the sorbas basin se spain determined by paleostress analysis abstract the neogene subsidence history of the sorbas basin situated in the internal zone of the betic cordilleras of southeastern spain is strongly controlled by strike slip deformation the sedimentary sequence of the basin offers a good control on the timing of separate phases of fault activation the southern border of the sorbas basin is formed by a major east west trending fault zone the gafarillos fault zone which consists of intermixed slivers of pre neogene basement blocks and neogene basin sediments fault patterns and paleostress analysis both indicate that major displacement along this fault zone was dextral with a n310e oriented maximum principal stress axis strike slip movement along the east west oriented faults ended during the earliest messinian after a minimum of 6 ma of activation paleostress analysis indicates a subsequent phase of strike slip fault movement present in sites of up to early pliocene age the maximum principal stress axis orientation is n350e for this phase this deformation is synchronous with sinistral displacement along the palomares fault zone situated directly to the east of the study area subsequently our paleostress analysis indicates an extensional regime during the late pliocene to quaternary however extensional tensors were calculated at a number of sites possibly representing local stress regimes coexisting with the main strike slip deformation and sorbas basin subsidence folding of tortonian sediments points out that local compressional deformation took place as well during the neogene basin history observed wide ranges for the ellipsoid shapes of the calculated tensors support the existence of lateral stress variations

heterogeneous extension and the role of transfer faults in the development of the southeastern betic basins se spain large strike slip faults in the eastern betics are interpreted to have developed in a transcurrent setting in response to 4 6 mm yr of africa iberia nw se convergence however here we show that some of these faults are transfer faults accommodating heterogeneous late miocene extension the north cabrera dextral fault and other e w to ne sw strike slip faults in the sorbas basin were transfer faults produced under sw ne extension these faults together with related normal faults form the main boundaries of two sedimentary depocenters active between the serravallian and the tortonian the older north cabrera depocenter extended between the serravallian and the early tortonian approximately 13 8 to 9 ma while the younger gacia depocenter formed in response to late tortonian extension approximately 9 to 7 5 ma the latter formed to the west of the north cabrera depocenter by a listric fan of normal faults with sw directed transport that are linked by dextral and sinistral transfer fault segments these faults root on a low angle detachment cutting into the exhumed high pressure nevado filabride complex rocks at 0 8 km depth the present work reveals that 1 this extension was partially coeval with and kinematically linked to sinistral displacement along the carboneras fault farther south in the nijar basin 2 this westward directed extension produced elongated core complexes and tilted blocks to the north of the carboneras fault and magmatic accretion upon thinned continental crust to the south probably in response to slab tearing or detachment and associated edge delamination of the iberian continental lithospheric mantle beneath the betics

fluvial dissection isostatic uplift and geomorphological evolution of volcanic islands gran canaria canary islands spain abstract digital analysis of torrential gullies barrancos deeply incised into the volcanic island of gran canaria canary islands allows us to extract the longitudinal profiles and pre incision surfaces for individual basins from which morphometric parameters length elevation area slope have been calculated other derived parameters such as ridgeline profiles maximum incision values volume removed by fluvial erosion geophysical relief and isostatic uplift have also been computed based on k ar ages for the island well constrained incision uplift rates have been calculated by means of the combination of different methodological approaches commonly used in orogens and large mountain ranges the geomorphological and morphometric analyses reveal that the island is clearly divided into four environmental quadrants determined by the combination of a couple of key factors the age of the volcanic surfaces and the climatic conditions these factors determine a young sector covered with plio quaternary platform forming lavas finished at 1 9 1 5 ma evolving under contrasting wet ne to dry se climates and an older sector conserving the residual surfaces of the miocene shield building 14 5 8 7 ma at the ridgelines also subjected to wet nw and dry sw climates incision is related to the age zonation of the island maximum incisions

active fault segmentation in northern tunisia abstract active shortening structures in northern tunisia have developed by tectonic inversion since the pliocene after late miocene extensional collapse of the whole region restored plio quaternary deformation observed on reflection seismic lines indicates deformation rates around 0 6 0 8 mm yr in the studied segments and larger amounts of shortening to the west of northern tunisia 16 than to the east 7 which suggests tectonic inversion started earlier to the west and later propagated eastwards reaching northeastern tunisia in the late pliocene this shortening is registered on striated pebbles in quaternary alluvial terraces and fault slip data giving two populations of strain ellipsoids with n s and wnw ese maximum shortening morphometric analysis in combination with field fault segmentation mapping show that topographic uplift and drainage rejuvenation occurs in relation to 20 30 km long ene wsw reverse fault segments and related antiforms that are offset and linked by e w to wnw ese dextral and ne sw oriented sinistral faults the largest fully linked fault system is the alia thibar fault this 130 km long fault zone shows an helicoidal geometry with five different fault segments including reverse dextral sinistral and oblique faults due to the young age of tectonic inversion after late miocene extensional collapse of the region the present relief of northern tunisia is characteristic of a young thrust and fold belt with dominating axial valleys along synforms and an incipient transverse drainage development propagating from west to east

gps constraints on africa nubia and arabia plate motions summary we use continuously recording gps cgps and survey mode gps sgps observations to determine euler vectors for relative motion of the african nubian arabian and eurasian plates we present a well constrained eurasia nubia euler vector derived from 23 igs sites in europe and four cgps and three sgps sites on the nubian plate 0 95 4 8 n 21 8 4 3 e 0 06 0 005 myr 1 we see no significant 1m m yr 1 internal deformation of the nubian plate the gps nubian eurasian euler vector differs significantly from nuvel 1a 21 0 4 2 n 20 6 0 6 e 0 12 0 015 myr 1 implying more westward motion of africa relative to eurasia and slower convergence in the eastern mediterranean the arabia eurasia and arabia nubia gps euler vectors are less well determined based on only one cgps and three sgps sites on the arabian plate the preliminary arabia eurasia and arabia nubia euler vectors are 27 4 1 0 n 18 4 2 5 e 0 40 0 04 myr 1 and 30 5 1 0 n 25 7 2 3 e 0 37 0 04 myr 1 respectively the gps arabia nubia euler vector differs significantly from nuvel 1a 24 1 1 7 n 24 0 3 5 e 0 40 0 05 myr 1 but is statistically consistent at the 95 per cent confidence level with the revised euler vector reported by chu gordon based on a re evaluation of magnetic anomalies in the red sea 31 5 1 2 n 23 0 2 7 e 0 40 0 05 myr 1 the motion implied in the gulf of aqaba and on the dead sea fault dsf by the new gps nubia arabia euler vector i e ignoring possible sinai block motion and possible internal plate deformation grades from pure left lateral strike slip in the gulf and on the southern dsf with increasing compression on the central and northern dsf with relative motion increasing from 5 6 to 7 5 mm yr 1 1m m yr 1 from south to north along the northern dsf i e north of the lebanon restraining bend motion is partitioned between 6 1m m yr 1 left lateral motion parallel to the fault trace and 4 1m m yr 1 faultnormal compression relative motions on other plate boundaries including the anatolian and aegean microplates derived from the gps euler vectors agree qualitatively with the sense of motion indicated by focal mechanisms for large crustal earthquakes m 6 where data are available on fault slip rates on plate bounding faults north anatolian fault east anatolian fault dead sea fault red sea rift they are generally lower than but not significantly different from the full plate motion estimates suggesting that the majority of relative plate motion is accommodated on these structures

structure and geological history of the carboneras fault zone se spain part of a stretching transform fault system abstract the carboneras fault zone cfz is a major ne sw trending tectonic lineament in se spain active from upper miocene to recent times it separates the volcanic cabo de gata terrain to the se accumulated over 18 6 ma bp from the tract of uplifted alpine metamorphic basement blocks and post orogenic basins that comprise the betic cordilleras lying to the nw new geological mapping and age determinations have been used to constrain the geometry and geological history of the fault zone the cfz consists of left lateral strike slip faults bearing fault gouge formed in the uppermost 5 km of the crust the faults cut metamorphic basement and folded post orogenic sediments and volcanic rocks and acted as a conduit for calc alkaline volcanic rocks rising to the surface nw of the cfz a series of unconformities and deformation episodes affect successive sedimentary formations of upper miocene age the cfz is interpreted as part of a transform fault system separating ne sw stretched and nw se shortened crust deformed above a south westward retreating subducted slab from a less deformed terrain lying to the south east total offset on the cfz may be up to 40 km but is at least 15 km

geomorphologic proxies for bedrock rivers a case study from the rwenzori mountains east african rift system geomorphic proxies yield useful insights into understanding long term endogenic and exogenic response to erosion and or rock uplift rates by evaluating areal proxies including asymmetry factor af mountain front sinuosity smf hypsometric integral hi geophysical relief and shape factor shp and linear proxies including normalized steepness index ksn length gradient index slk and chi gradient m the erosion and or rock uplift rates can be quantified we carried out morphotectonic analysis in the rwenzori mountains which represents an anomalously uplifted precambrian horst within the western branch of the east african rift system ears this study aims to 1 evaluate the relationship between geomorphic proxies and drainage basin s maturity 2 evaluate the usefulness of geomorphic proxies as recorders of erosion and or rock uplift rates 3 evaluate the sensitivity of each geomorphic proxy to the drainage basin size and geometry stream order glaciers extent and local structures 4 explore internal correlation within the geomorphic proxies and 5 contribute to the understanding of morphotectonic evolution of the rwenzori mountains for this we computed the stream s good of fitness r2 an indicator of the drainage basin s maturity and geomorphic proxies for the drainage basins and their streams in the rwenzori mountains from the advanced spaceborne thermal emission and reflection radiometer aster digital elevation model dem subsequently we correlated the areal geomorphic proxies with each other and with r2 also we correlated the linear geomorphic proxies with each other and with published erosion rates obtained from cosmogenic 10be analysis our results show that the areal geomorphic proxies af smf hi relief and shp considering the drainage basin size and geometry stream order glacier extent and local structures can be applied to locally evaluate the maturity of the drainage basin we also found that the linear geomorphic proxies ksn slk and m have strong positive correlation with the erosion rates they are effective in detecting fault activities and some of them ksn and m are highly correlated with each other additionally our geomorphic proxy results suggest that the north and south sectors of the rwenzori mountains are in relative tectonic quiescence but that the central sector is experiencing higher levels of erosion and rock uplift

palaeomagnetic results from upper miocene and pliocene rocks from the internal zone of the eastern betic cordilleras southern spain palaeomagnetic and rock magnetic studies were carried out on samples from thirteen volcanic and nine sedimentary sites of late miocene to pliocene age from the internal zone of the eastern betic cordilleras after comparing palaeomagnetic results with the expected pliocene miocene direction rotated and unrotated areas can be recognized rotations being clockwise and counter clockwise some rotations are of great magnitude unlike deformation in the external betics late miocene to present block rotations in the internal betic zone are non systematic and related to the movement of faults as local responses to the late miocene present regional stress field due to the n140 convergence of africa and the iberian peninsula

crustal types and tertiary tectonic evolution of the alboran sea western mediterranean multichannel seismic reflection images across the transition between the east alboran and the algero balearic basins show how crustal thickness decreases from about 5 s two way traveltime twtt 15 km thick in the west east alboran basin to 2 s twtt typical of oceanic crust 6 km thick in the east algero balearic basin we have differentiated three different crustal domains in this transition mainly on the basis of crustal thickness and seismic signature boundaries between the three crustal domains are transitional and lack evidence for major faults tilted blocks related to extension are very scarce and all sampled basement outcrops are volcanic suggesting a strong relationship between magmatism and crustal structure stratigraphic correlation of lithoseismic units with sedimentary units of southeastern betic basins indicates that sediments onlap igneous basement approximately at 12 ma in the eastern area and at 8 ma in the western area linking seismic crustal structure with magmatic geochemical evidence suggests that the three differentiated crustal domains may represent from west to east thin continental crust modified by arc magmatism magmatic arc crust and oceanic crust middle to late miocene arc and oceanic crust formation in the east alboran and algero balearic basins respectively occurred during westward migration of the gibraltar accretionary wedge and shortening in the betic rif foreland basins arc magmatism and associated backarc oceanic crust formation were related to early to middle miocene subduction and rollback of the flysch trough oceanic basement subduction of this narrow slab beneath the alboran basin was coeval with collision of the alboran domain with the iberian and african passive margins and subsequent subcontinental lithosphere edge delamination along the betic rif margins

offset and evolution of the gowk fault s e iran a major intra continental strike slip system abstract we use drainage reconstructions to estimate long term offsets on the gowk fault an oblique right lateral strike slip fault in eastern iran on which there have been a number of recent large earthquakes a 3 km horizontal offset is inferred from well preserved geomorphology we further identify a total cumulative offset of 12 km which produces a simple reconstruction of geomorphology across the fault filling in pull apart basins restoring rivers to linear courses across the fault trace and aligning structural and bed rock features the probable age of the gowk fault and k ar dating of offset basalts north of the study region suggest an overall slip rate of 1 5 2 4 mm year this is small compared with the overall 10 20 mm year of shear expected between central iran and afghanistan and the deficit is likely to have been accommodated on other faults east of the gowk fault drainage displaced by dextral movement leads to the development of a series of basins along the fault and a longitudinal topographic profile that resembles an asymmetric saw tooth the geomorphic evolution of the fault zone at the surface includes both normal and reverse faulting components reflecting a probable ramp and flat structure in cross section this interpretation is consistent with evidence from the analysis of seismological radar and surface rupture data in recent earthquakes

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

assessment of the relative tectonic activity in the bailongjiang basin insights from dem derived geomorphic indices the bailongjiang drainage basin is located in the transition zone between the tibetan plateau and the loess plateau active tectonic records demonstrate the interplay between the tibetan plateau uplift and the different movement of the faults to assess the relative tectonic activities in this area five geomorphic indices derived through geographic information system were analyzed the stream gradient index sl hypsometric integral hi valley floor width valley height ratio vf drainage basin shape and drainage basin asymmetry af active faults seismogenic activity and river terraces were also integrated into this investigation the results indicate that four classes of relative tectonic activity were defined class 1 very high relative tectonic activity 5 5 in the area class 2 high 54 class 3 moderate 24 1 and class 4 low 16 4 sub basins at the midstream and upstream of bailongjiang show abnormally high sl high hi af and convex hypsometric curves and low vf values due to the impact of the east ward extrusion of the tibetan plateau and active faults the downstream shows low sl hi and af and concave hypsometric curves due to the low tectonic activity of the faults inhibited by minshan these results are consistent with the geological background

use of variable scale pressure test data to estimate the log hydraulic conductivity covariance and dispersivity of fractured granites near oracle arizona abstract application of modern stochastic theories to nonuniform geologic media requires among other things knowing the principal directions and correlation lengths of the log hydraulic conductivity covariance to infer this information by standard geostatistical methods directly from point measurements of hydraulic conductivity in three dimensional space is seldom possible due to a ubiquitous scarcity of data to show how this difficulty can be overcome we use an example of fractured granitic rocks near oracle arizona at this site hydraulic conductivities were measured on a small scale by packer tests and on a larger scale by cross hole tests the test results suggest that the measured hydraulic conductivities can be viewed as quantities defined over a continuum which are scalar on a local scale but exhibit large scale anisotropy due to spatial nonuniformity and the effect of fracture orientations based on this observation the two sets of hydraulic conductivity data are related theoretically and the resulting expression is used to estimate the anisotropic covariance function of log hydraulic conductivities at the oracle site we then employ these parameters to calculate a fickian dispersivity tensor for the oracle granite by relying on the recent theory of neuman et al 1987a our results highlight the need to extend available stochastic theories to the domain of strongly nonuniform media the properties of which fluctuate with large amplitudes

tectonic inversion of an asymmetric graben insights from a combined field and gravity survey in the sorbas basin the formation of sedimentary basins in the alboran domain is associated with the exhumation of metamorphic core complexes over a ca 15 ma period through a transition from regional late orogenic extension to compression an integrated study coupling field analysis and gravity data acquisition was performed in the sorbas basin in the southeastern betic cordillera detailed field observations revealed for the first time that extensional tectonics occurred before shortening in this basin two extensional events were recorded with nw se to n s and ne sw kinematics respectively the first of which being likely responsible for the basin initiation tectonic inversion of the basin then occurred around 8 ma in an overall ca n s shortening context 2d gravity sections reveal that the basin acted as an active depocenter as the basin floor locally exceeding 2 km depth is characterized by a marked asymmetric architecture based on this integrated study we explore a new evolutionary scenario which can be used as a basis for interpretations of the neogene tectonic history of the southeastern betics

morphometry of drainage basins and stream networks as an indicator of active fold growth gorm anticline fars province iran abstract the zagros folded belt as one of the most tectonically active areas in the world contains nw se trending whaleback anticlines that are growing vertically and laterally morphometric indices are widely used in tectonic geomorphological research because of their low cost and relative ease of application drainage basins and their networks adapt to tectonically induced changes in surface slope and hence their qualitative and quantitative analysis can reveal aspects of active anticlinal growth this study evaluates the morphometric properties of drainage basins and their networks developed on the fold limbs using this quantitative data to detect lateral propagation of the gorm anticline in the zagros simply folded belt zsfb the gorm anticline was considered to be suitable for this approach because of the variability of drainage basins and their networks along the axis of the anticline and also transversely across its forelimb and backlimb the morphometric properties of stream networks including drainage density dd drainage frequency df ratio of 1st order streams to the total number of streams of all orders n1 n length of 1st order streams l1 spacing ratio r of main streams on flanks and drainage patterns were analyzed in three zones of the anticline southeastern se central and northwestern nw also the morphometric indices of drainage basins such as basin area ba shape bs asymmetry factor af hypsometric integral hi a new proposed crescentness index ci and sinuosity of anticline divide sad were evaluated results show that an increase in n1 n ratio and l1 from the center towards both the southeastern and northwestern fold noses suggests lateral growth of the anticline towards the southeast and northwest the se and nw zones are characterized by the smaller elongated and crescent shaped basins lower elevations lower dip slopes higher hypsometric integral and lower sinuosity of anticline ridge these results collectively suggest that the southeastern and northwestern fold noses are younger less eroded and laterally growing the formation of crescent shaped basins with asymmetric forked drainages developed in the se and nw zones are considered to be useful indicators of lateral growth of the gorm anticline although higher values of ba sad df and s indexes in the central part of the fold can be attributed to the older relative age of this area the activity of the nezamabad fault and the exposure of some weak rocks also play some roles in explaining the increase the values of parameters overall the n1 n l1 ci sad indexes as well as the fan shaped and asymmetric forked drainage pattern are the most useful tectonic geomorphological criteria to detect lateral propagation of anticlines

analyzing the drainage system anomaly of zagros basins implications for active tectonics abstract morphometric analysis of hierarchical arrangement of drainage networks allows to evaluate the effects of external controls especially tectonics on basin development in this study a quantitative method for calculation of stream s hierarchical anomaly number is introduced morphometric parameters such as hierarchal anomaly index a percent of asymmetry factor paf basin shape bs basin length to mean width ratio bl bmw stream s bifurcation ratio rb bifurcation index r drainage density dd drainage frequency df and anticline s hinge spacing hs of 15 basins in zagros mountains were examined results show that the strong correlations exist between pairs a paf r 0 844 a bs r 0 732 a bl bmw r 0 775 a r r 0 517 paf bl bmw r 0 519 bs r r 0 659 bl bmw r r 0 703 hs a r 0 708 hs paf r 0 529 and hs bs r 0 516 the variations in trend of anticlines control the shape of basins so that where anticlines hinges become closer to each other in the downstream direction basin become narrower downward and hence the a increases the more uplifted northeastern anticlines cause the trunk river of the basins to migrate toward the younger anticlines in southwest and hence a increases because the trunk river receives a lot of first order streams data reveal that the rate of a is higher in elongated synclinal basins due to the decrease in the intensity of deformation from northeast toward southwest of zagros the hinge spacing of anticlines increases southwestwards data reveal that the variation in hinge spacing of anticlines strongly controls the basin s shape and tilting as well as the hierarchical anomaly of drainage system since the elongation and tilting of basins are associated with the variations in rates of folding uplift and hinge spacing of anticlines it can be concluded that the hierarchical anomaly of drainages in studied basins is controlled by the intensity of zagros tectonic activities

mode of extensional tectonics in the southeastern betics se spain implications for the tectonic evolution of the peri alboran orogenic system the gibraltar arc which closes the westernmost part of the mediterranean basin is a miocene a type subduction arc formed by the continental collision of various pre miocene terranes in the major zone of collision between the iberian and african cratons the hanging wall block known as the alboran domain has undergone more than 300 km migration from a more easterly position where it was the continuation of the alpine cretaceous paleogene orogen contemporaneous with thin skinned thrusting in the footwall the alboran domain underwent two episodes of nearly orthogonal extension in which extensional systems developed with directions of extension varying from a nnw sse system orthogonal to the belt axis in the late burdigalian langhian to a wsw directed orogen parallel one in the serravallian the superposition of these two systems resulted in a chocolate tablet megastructure this extensional pattern is not satisfactorily explained in previously proposed models for the evolution of the arc orthogonal extension is plausible in a process of the gravitational collapse of an overthickened crust nevertheless orogen parallel extension is more difficult to explain in this context we advocate that the wsw directed low angle normal faults formed during large scale extension in connection with important westward arc migration the driving force of extension in a general context of convergence is controversial and varies between a convective removal model and a delamination model constraints on both the timing and the kinematics of extension as presented in this paper seem to support the contribution of both mechanisms convective removal may have started the process but continued n s convergence could have resulted in westward tectonic escape and asymmetric lateral inflow of asthenospheric material accompanying lithospheric delamination

response of quaternary fluvial systems to differential epeirogenic uplift aguas and feos river systems southeast spain the geomorphic expression of two fluvial systems the rio de aguas and the rambla de los feos in southeast spain reflects their adjustment to differential epeirogenic uplift and local tectonic activity during the quaternary regional uplift of a depositional marine surface resulted in the development of a southward flowing drainage network during late pliocene early pleistocene time disruption of this consequent drainage began as the alhamilla cabrera sierras and the sorbas basin were differentially uplifted relative to the surrounding basins the ancestral feos drainage responded by incision across the uplift through a combination of superimposition and antecedence differential uplift of the sorbas basin enhanced headward erosion of strike oriented drainages and promoted capture of the ancestral feos drainage by the rio de aguas during the late pleistocene stratigraphic relations and soil development indicate that epeirogenic uplift and local tectonics together with climatic fluctuations have influenced the development of the drainage systems throughout the quaternary

tectonics controls on fluvial landscapes and drainage development in the westernmost part of switzerland insights from dem derived geomorphic indices abstract this work focuses particularly on the geomorphological evidence for the tectonic controls on the development of the present day fluvial landscapes in the westernmost part of switzerland the tectonic deformation was evaluated on the basis of a combined analysis of several classical geomorphic indices hypsometric curves and integrals transverse topographic symmetry index and channel s bottom gradients through high precision dem processing a new optimization strategy was applied for defining geomorphic anomalies related to tectonic activity along the channels of three rivers based on a combined investigation of topographic swath longitudinal profiles geological and geophysical observations the results show that the abnormally high values of hypsometric integral are spatially occurred on the hanging walls of thrust faults while abnormally low ones are spatially observed in the same locations of paleo ice stream pathways observations obtained from transverse topographic symmetry index display asymmetries in the most of the studied drainage basins with a predominant se direction of lateral migration this direction is in agreement with the dominant dip direction of the bedding planes within the study area abnormal changes in the channel s bottom gradients which almost coincide in space with pronounced change in the depth of the subsurface geologic layers and in the geophysical properties are marked by distinct topographic relief in areas where rivers flow above blind and emergent faults our analysis not only confirms that there is a significant tectonic control on the evolution of drainage systems but also revealed a possible evidence for the reactivation of some inherited faults

the impact of a major quaternary river capture on the alluvial sediments of a beheaded river system the rio alias se spain the rio alias is a transverse river system developed within the sorbas and almeria neogene sedimentary basins within the internal zone of the betic cordillera southeast spain headwaters of the rio alias rise in the southern margins of the sorbas basin following a superimposed transverse course across the sierra alhamilla cabrera and its associated boundary faults a major river capture event within the sorbas basin c 70 ka created a situation whereby the rio alias abruptly lost c 70 of its drainage area such an extensive loss of drainage area led to significant modification of the fluvial system in both upstream and downstream zones on the capturing stream and downstream on the beheaded system on the beheaded rio alias a combination of terrace mapping clast identification analysis field descriptions of pedological development and mineral magnetic analysis allows the relative timing of the capture event to be confirmed examination of the fluvial architecture of the quaternary terrace deposits reveals significant changes in bedform geometry involving a reduction in bedform height degree of channelisation and maximum clast size in the post capture sediment assemblage the post capture evolution of the rio alias has been heavily influenced by the river capture event highlighting the need for further analysis of beheaded drainage systems and their influence on developing landform assemblages

seismicity and focal mechanisms in south spain abstract recent improvements in regional seismological networks allow a better definition of the seismicity and the determination of focal mechanisms in south spain this region is part of the lithospheric plate boundary between africa and eurasia and shows a continuous seismic activity of moderate magnitude m h h 650 km earthquakes also occurring in the region eight fault plane solutions have been determined that can be related to the tectonics of the area the solutions for the shallow shocks are compatible with regional stresses with horizontal compressions in nw se direction and tensions in e w direction that produce normal faulting along the n30 to 60 w and n10 to 30 e systems of faults the mechanisms of the intermediate depth shocks can be explained in terms of a subduction zone from africa in a nw direction that is under compression

tectonic geomorphology of the serrania de san lucas central cordillera regional implications for active tectonics and drainage rearrangement in the northern andes abstract we explore the structural and geomorphological evidence for recent tectonic activity in the serrania de san lucas san lucas range slr the northern segment of the central cordillera in the colombian northern andes a morphostructural and geomorphological analysis was carried out in this isolated range using several topographic metrics like the local relief slope variability hypsometric integral swath profiles normalised concavity steepness ksn drainage basin shape index bs asymmetry factor af mountain front sinuosity smf and the ratio of valley floor width to valley floor height vf after remote sensing and geological analysis of the structural pattern we propose that the slr represents a horse tail termination of the palestina fault that seems to have reactivated in the miocene pliocene in a transpressive stress state during the andean orogeny based on this structural model and the geomorphic indices we divided the slr into two regional domains the simiti domain in the east and the palestina domain in the west the simiti domain is dominated by ne sw striking structures with a right lateral kinematic whereas the palestina domain is controlled by the n s right lateral palestina fault which is the predominant structure in the slr we demonstrate that recent tectonic activity and higher uplift rates have been preferably constrained to the simiti domain to the north of the simiti san blas faults along the ne sw striking faults in this area low smf and vf values suggest an active mountain front bounded by the reverse morales fault and quaternary uplift rates between 0 05 and 0 5 mm yr on the other hand the quaternary tectonic activity in the palestina domain was concentrated in the northern portion where climate has also played a significant role in controlling denudation rates and landscape evolution the variable uplift pattern between both domains has induced along strike changes in divide mobility and timing of drainage reorganisation within the slr discrete capture events forced a west southwest migration of the eastern side towards the western side of the slr the concentrated highest tectonic activity in the simiti domain progressively modified the topographic conditions and triggered the divide migration event our findings provide new and valuable information on the active tectonics and neogene to quaternary landscape evolution in this poorly studied area in the northern andes