weathering rates of historic sandstone structures in semiarid environments ebro basin ne spain abstract long term weathering rates of sandstones were obtained for well dated from 400 to 1100 years bp historic structures wall sections of the alberuela castle in a semiarid environment of the central ebro basin ne spain using an exclusive movable contour plotting frame this sandstone has a low durability controlled mainly by textural properties differences observed in weathering rates are clearly controlled by the age of building as well as the orientation of the studied sandstone wall sections weathering processes related to insolation control the asymmetric spatial pattern of weathering rates in surfaces exposed for since 1100 bp which are higher in southeast facing sandstone wall sections 8 4 mm 100 years than in southwestern 4 4 mm 100 years and northern faces 3 9 mm 100 years in addition exponential increase in weathering rates with time from 1 6 2 2 mm 100 years in surfaces exposed for since 800 400 bp to 8 4 mm 100 years in surfaces exposed for since 1100 bp in southeastern faces may be probably related to environmental changes during the last millennium

late cenozoic geodynamic evolution of eastern indonesia this paper presents an internally and globally consistent model of plate evolution in eastern indonesia from middle miocene to present time it is centered on the banda sea region located in the triple junction area between the pacific philippine australia and south east asia plates the geological and geophysical data available from indonesia were until recently insufficient to define a unique plate tectonic model in this paper the new data taken into account clearly restrict the possible interpretations owing to a great number of geological geophysical and geochemical studies the major plate boundaries the sunda banda subduction zone to the south the tarera aiduna fault zone and the seram thrust to the east and the sorong fault zone and molucca sea collision zone to the north are now clearly identified the age of the major tectonic structures is also better known geodetic measurements well constrain the present time plate kinematics we also consider the deformation history within eastern indonesia where numerous short lived microplates and their related microcontinents successively accreted to the asiatic margin moreover magnetic anomalies identification of the north and south banda sea basins allows a precise kinematic reconstruction of the back arc opening we used the plates software to test the coherency of our model presented as a series of 4 plate reconstruction maps from 13 ma to the present finally the origin of oceanic domains restored by our reconstruction is discussed

salt weathering simulation using a single immersion technique samples of concrete were subjected in an environmental cabinet to six different diurnal cycles of temperature and humidity change representative of desert surface conditions in the presence of a range of saturated salt solutions the samples were not subjected to repeated immersion or continuous partial immersion as has been the case in most previous experiments breakdown did occur nonetheless the two most effective cycles were one from egypt with a very high daytime maximum and one from the negev with high nocturnal humidity conditions cycles with relatively modest temperature and humidity cycles were ineffective in causing debris liberation

the effect of rock strength on weathering rates of sandstone used for angkor temples in cambodia abstract this study determined the weathering rates from the depths of hollows formed by the deterioration of sandstone blocks used to build angkor temples in the 7th 12th centuries due to capillary processes these hollows generally develop at the bases of building components such as doorframes false doorframes window frames and pillars in this study 55 locations in 29 temples were selected to measure maximum hollow depth based on the ages of the temples the weathering rate was calculated to be in the range 7 92 mm ka 1 the weathering rate was found to be independent of building component type and aspect the calculated weathering rate corresponds to the physical weathering rate of sandstone caused by the wetting drying cycles that result from the tropical environment along with the dry season an equation that can estimate the maximum depth of a hollow in a sandstone block was proposed based on temple age and the coefficient obtained from two types of rock hardness values the equation coefficient is an effective index that can help predict the deterioration of stone cultural artifacts such as the angkor temples

magmatism and metallogenic mechanisms of the baoshan cu polymetallic deposit from the lesser xing an range ne china constraints from geology geochronology geochemistry and hf isotopes abstract the baoshan cu polymetallic deposit is a recently discovered skarn deposit in the northern lesser xing an range ne china the orebodies are mainly hosted in the contact zone between granitic intrusions and lower cambrian dolomitic crystalline limestones or skarns we present here zircon u pb and molybdenite re os age data whole rock geochemistry and zircon hf isotopic data to constrain the geodynamic mechanisms of igneous activity and metallogenesis within the baoshan cu polymetallic deposit la icp ms zircon u pb dating suggests that a hornblende quartz monzonite and porphyritic biotite granite were emplaced at 252 45 0 70 ma and 251 10 0 98 ma respectively molybdenite separated from ore bearing quartz veins or skarn type ores yields a weighted mean model age of 250 3 3 4 ma which coincide with the emplacement of the igneous rocks these data suggest that the late permian early triassic magmatic and mineralization event led to the formation of the baoshan cu polymetallic deposit granitic intrusions are closely associated with this mineralization and have high contents of sio 2 60 90 68 98 wt al 2 o 3 15 15 16 98 wt and k 2 o 2 77 4 17 wt with a cnk ratios of 0 86 0 96 these granites are classified as metaluminous and high k calc alkaline i type granites and are enriched in rb th u and k and depleted in nb ta p and ti moreover moreover the hornblende quartz monzonite and porphyritic biotite granite have geochemical characteristics similar to adakites and island arc calc alkaline rocks respectively in situ zircon hf isotope data on the hornblende quartz monzonite samples show e hf t values from 0 1 to 3 1 and porphyritic biotite granite samples exhibit heterogeneous e hf t values from 5 4 to 1 1 the geochemical and isotopic data for the baoshan intrusions indicate that the late permian early triassic continental continental collision caused over thickening and delamination of the lower crust partial melting of delaminated lower crust formed the primary adakitic magmas which may have reacted with surrounding mantle peridotite during ascent hornblende quartz monzonite was formed by the emplacement of the adakitic magmas whereas the formation of the porphyritic biotite granite was caused by the mixing of adakitic magmas with ancient crustal materials during ascent moreover ore forming materials were typically derived from the adakitic magmas with high oxygen fugacity which incorporated significant amounts of ore forming elements based on the regional geological history and the new geochemical and isotopic data from intrusions we suggest that diagenesis and mineralization of the baoshan cu polymetallic deposit took place in a transitional tectonic setting from collisional orogeny to extension after collision of the north china plate and songnen block during the latter stages of the xingmeng orogeny

engineering aspects and time effects of rapid deterioration of sandstone in the tropical environment of sabah malaysia cut slopes in rock masses start to deteriorate directly after excavation due to stress relief and weathering the deterioration is a time dependent process that depends on the local climate and the rock mass including its history and the environment the amount of deterioration per time unit the weathering intensity rate is not a constant over time but is for most rock masses larger when the mass is less weathered and becomes smaller with further progressing weathering a study has been carried out to establish the relationship between weathering intensity rate and exposure time for the intact rock strength irs of sandstone in humid tropical areas the data set for the study was collected in and near kota kinabalu sabah malaysia which has a humid tropical climate the geology in the area consists of thick sequences of sandstone and shale beds of the crocker formation results show that the best relationship between intact rock strength irs and exposure time t is by a logarithmic function irs t 105 34 log 1 t this relationship can likely be used for prediction of the intact rock strength development of similar sandstone over the engineering lifetime of man made slopes in tropical areas

weathering rates of sandstone in a semi arid environment hunter valley australia the rate of sandstone weathering in the semi arid climate of the hunter valley new south wales australia has been estimated from observations of gravestone weathering in the area the gravestone data points to two distinct stages in the weathering process the first stage covering the first century of exposure is characterised by a relatively low recession rate of 0 5 mm 100 years this is followed by a second stage in which the rate of weathering increases sharply to ca 2 5 mm 100 years the non linear nature of the weathering trends over time suggests that during the first century of exposure structural changes took place within the sandstone material which lay the foundation for accelerated weathering after further exposure laboratory trials were also conducted to identify the effectiveness of different weathering processes in the decay of sandstone in this region of the four processes examined only the freeze thaw cycle produced a significant degree of mass loss and is therefore most likely a strong contributor to the weathering of sandstone in this region

fault reactivation and structural inversion backarc and intraplate compressive deformations example of the eastern sunda shelf indonesia the tectonic evolution of the eastern sunda platform in indonesia is revealed by the study of seismic profiles and comprises three general tectonic periods during the cenozoic extension with graben infill from the paleogene to the early miocene a tectonically quiet period with only broad subsidence and a middle miocene recent period of folding inversion and thrusting these structures reveal changes in the intraplate stress field which was controlled by the changes in the boundary conditions of the plates collisions on the northern and eastern sides and interplate coupling southward along the java subduction zone inversions often occurred without reactivation of pre existing normal fault planes at the upper levels of these faults the factors controlling these deformations are discussed with special interest placed on the conditions for the potential reactivation of cohesionless normal faults inversion and reactivations were mostly controlled by the orientation of the pre existing fault planes in relation with the regional stress field and by the tectonic stress regime in a strike slip regime effective principal stresses 1 and 3 horizontal with 1 2 3 the optimum conditions for reactivation in isotropic rocks are pre existing faults that strike close to the potential two vertical conjugate failure planes the same mechanical properties as for pre existing fault prevail in such conditions strike slip movements and reverse strike slip movements and associated en echelon folds were generally observed in a compressive regime 1 and 2 horizontal with 1 2 3 typical steeply dipping normal faults are difficult to reactivate by slip movements we suggest that reverse slip movements occurred in the deeper levels of faults and were accommodated by flexure above the pre existing fault planes and the inversion of grabens the strongly inverted grabens are those whose orientation is perpendicular to the regional compression nevertheless with strong regional shortening large uplifts and thrust faults were observed with reactivation in the form of reverse or reverse strike slip movements along pre existing steeply dipping normal fault planes

chemistry of oil field brines in relation to diagenesis of reservoirs 1 use of mineral stability fields to reconstruct in situ water composition example of the mahakam basin abstract during mineral diagenesis the chemical composition of pore water can be strongly influenced by mineral reactions especially under geological conditions where water rock ratios are low to model and eventually to predict diagenesis it is important to have an understanding of formation water composition however available water analyses in many basins are not complete enough for this purpose in most cases reliable values for ph dissolved silica and aluminium are lacking such data can be reconstructed using various relations developed herein these data are constrained by petrographic observations because of their well preserved or authigenic character some alumino silicates are considered as relatively stable and can be thought of as effectively saturated with respect to them the saturation state of the other minerals of the matrix can be discussed according to these constraints the sub arkosic series of the mahakam basin resevoirs mio pliocene are used as a reference example to perfect a method capable of reconstructing consistent compositions of diagenetic waters suitable for input into diagenetic modelling

the structural development of the wessex basin the mesozoic and cenozoic structures of southern england form part of a system of disturbances which extends across the channel into northern france they are reviewed in the light of published data from south dorset basin development started with permo triassic rifting and is believed to have continued through the jurassic and early cretaceous with intermittent growth on deep seated listric normal faults probably associated with roll over anticlines this regime had ceased by the aptian and the basin passed through a period of relative stability in the late cretaceous followed by tectonic inversion and in the miocene by northwards compressive movement along the former normal faults this partially restored the earlier separative displacement at depth and probably accentuated pre existing roll over anticlines it was expressed in the surficial upper cretaceous palaeogene sequence as monoclinal flexuring the early rifting and the change from overall n s crustal stretching to compression may reflect plate tectonic events in the north atlantic region

the structure and evolution of the wessex basin southern england an example of inversion tectonics abstract the wessex basin of southern england consists of four main sub basins each sub basin is thought to be fundamentally controlled by the normal reactivation of hercynian basement thrust and wrench or transfer faults post hercynian polyphase reactivation of both east west thrust and northwest southeast transfer faults tended to compartmentalise the basement thereby leading to the initiation of discrete permian cretaceous depocentres while rifting was confined to the western portions of the area during the permo triassic easterly migration in the mesozoic allowed the initiation of the weald and channel basins the sub basins represent therefore simple sinistral pull apart basins opening along northwest southeast faults this same fault direction is postulated to have also played a major role in controlling and or modifying the development of european basins in general major pre aptian uplift and erosion is largely attributed to the thermal effects and hence the isostatic uplift of the basin associated with continental rifting of the bay of biscay and the north atlantic margins major inversion and hence basin destruction began in the late cretaceous early tertiary with the uplift of the channel weald and vale of pewsey basins and culminated in the oligocene miocene synchronous with the helvetic phase of alpine deformation wessex basin inversion was facilitated by the thrust reactivation of variscan faults above an intracrustal detachment surface the same surface which allowed upper crustal extension and hence basin initiation in the permo triassic the structural development of the wessex basin both during extension basin formation phase and compression inversion phase was ultimately controlled by the plate motion of africa relative to europe such plate motions successfully predict the observed nw se sinistral motion from the stephanian to the aptian e w sinistral motion during the aptian cenomanian and largely nw se dextral motion from the cenomanian to the present day

anisotropic rayleigh wave phase velocity maps of the sunda plate abstract we explore the rayleigh wave phase velocity and shear velocity structures beneath sunda plate over a broad period range of 30 150 s and 5 100 km the two stations technique was used to measure dispersion curves from the waveforms of 19 233 teleseismic events 1998 2018 recorded worldwide by 75 broadband seismic stations spread around the sunda plate the interstation path specific dispersion curves are then inverted for high resolution isotropic and azimuthally anisotropic phase velocity maps in the frequency range 30 150 s as well as for shear velocity model between 5 and 100 km main findings include a strong dichotomy with fast velocities located beneath the south china sea and the sunda shelf compared with slow velocities found beneath the surrounding regions at short periods our model also exhibits very slow velocities beneath the hainan plume at lithospheric and asthenospheric depths the complex anisotropy in the region at shorter periods contrasts with the pattern observed at longer periods sampling the asthenosphere and is consistent with the absolute plate motions in the region

reinterpretation of the tectonic context of high temperature metamorphism in the broken hill block nsw and implications on the palaeo to meso proterozoic evolution abstract the origin of high temperatures during regional low pressure granulite facies metamorphism within the proterozoic broken hill block australia has been reinterpreted to be the result of burial of anomalously hot rock packages for which the lithospheric geothermal gradient was initially elevated during early rifting ca 1 71 1 67 ga and then maintained during a ca 1 62 ga short lived mid crustal extensional event mid crustal extension at ca 1 62 ga was associated with amphibolite facies metamorphism and elevated lithospheric geothermal gradients and occurred prior to activity along d2 high temperature shear zones peak low pressure granulite facies metamorphism ca 1 60 ga and crustal shortening during the olarian orogeny ca 1 60 1 59 ga this reinterpretation places the broken hill block within an environment in which multiple episodes of transient extension ca 1 71 1 62 ga were followed by a switch to shortening at ca 1 60 ga the interpreted tectonic environment is a continental back arc setting located in the over riding plate of a subduction zone along the southern margin of palaeoproterozoic australia

scale issues in weathering studies a review of the major scale issues in weathering studies reveals concerns over the fundamental spatio temporal distributions of weathering phenomena as well as issues of upscaling microscope based observations and linking different scales of observations in explanations of landform development various strategies are proposed which can be used to tackle these issues many rooted in non linear dynamical systems ideas as an initial step spatio temporal scale distributions are estimated here for weathering processes landforms and controls based on a range of empirical data two case studies of phytokarst in grand cayman and blistering and scaling of building stones are presented to illustrate the types of data that might be used to establish more convincing scale linkages in weathering investigations

effects of aspect on weathering anomalous behaviour of sandstone gravestones in southeast england rocks in the humid temperate zone tend to weather more severely on faces exposed to the prevailing winds than on their more sheltered leeward faces in southeast england however gravestones composed of a non local quartz rich sandstone exhibit a reverse weathering pattern the east facing lee sides exhibit a much greater depth and areal extent of weathering than the west sides which face the westerly wind and rain possible reasons for the asymmetric pattern of weathering are discussed copyright 2000 john wiley sons ltd

on the reactivation of extensional fault systems in terranes that have undergone substantial extension three sets of faults dominate a shallow to steep dipping commonly rotational normal faults b a really extensive shallow dipping normal detachment faults and c steep dipping transfer faults that strike at high angles to the normal faults these fault systems may extend through a large fraction of the crust reactivation of these fault systems will depend primarily on the relative strengths of the faults shear zones and their host rock and their orientation in the prevailing stress field it is concluded that reactivation is generally mechanically favoured but that it will probably only take place when the fault shear zones are in near ideal orientations consideration of the tectonic setting of extended terranes and of the limited number of well described examples suggests that reverse thrust reactivation of the normal and detachment faults and wrench reactivation of transfer faults are the most likely styles examples of these styles are described from the bass strait basins of southeastern australia because extended terranes commonly underlie sedimentary basins for example on passive continental margins reactivation of extensional faults may be a key control on the tectonic evolution of such basins i e basin inversion

mantle induced subsidence and compression in se asia since the early miocene rift basins developed extensively across sundaland the continental core of southeast asia since the eocene beginning in the early miocene basins in southern sundaland experienced widespread synchronous compression inversion and marine inundation despite a large drop in long term global sea level the mechanism for this large scale synchronous regional sea level rise basin inversion and subsidence is not well understood and contrary to expectations from traditional basin models and eustatic sea level trends we present geodynamic models of mantle convection with both deformable and rigid plate reconstructions to investigate this enigma models suggest that a slab stagnates within the transition zone beneath southeast asia before the miocene the stagnant slab penetrated through the 660 km mantle discontinuity during the early miocene and formed a slab avalanche event due to continuous subduction and accumulation of negatively buoyant slabs this avalanche may have induced large scale marine inundation regional compression and basin inversion across southern sundaland we argue mantle convection induced large scale basin compression in contrast to conventional plate margin induced compression this suggests mantle convection may exert a much stronger control on surface processes than previously recognized

the interaction between armouring and particle weathering for eroding landscapes the interaction between particle weathering and surface armouring and its effect on erosion has been investigated the effect of soil armouring is to decrease sediment transport with time by preferentially stripping away fine particles on the other hand the effect of weathering which breaks down the particles in the armour is generally believed to increase erosion by extending an existing armouring model armour and using a variety of published weathering mechanisms this interaction has been explored the model predicts that while this is generally true in some cases erosion can be decreased by weathering when the particles generated by weathering were approximately of equal diameter erosion increased while armouring decreased when weathering produced very fine particles by spalling erosion increased and armouring also increased when weathering produced a range of particles from fine to coarse the armour layer broke down and erosion decreased relative to the no weathering case this latter decrease in erosion was due to the high entrainment of coarser transportable materials from the bed decreasing the sediment transport capacity of the flow in these studies clear regimes could be identified where erosion was limited by either the energy of the flow alone i e transport limited or the rate of weathering weathering limited however for some mechanisms there was an interaction between the two which we called weathering transport limited copyright 2006 john wiley sons ltd

from faulted blocks to megamullions and megaboudins tethyan heritage in the structure of the western alps along the grenoble pelvoux viso transect in the western alps we schematize the geometrical relationships between 1 ductile marly calcareous sedimentary covers and 2 their more rigid substratum this substratum may be the pre alpine granitic gneissic basement the triassic dolomites or even the jurassic ophiolites basement mullions a few kilometer size are characteristic of the external part of the western alps arc dauphine zone they strongly contrast with the dolomitic or ophiolitic boudins also a few kilometer size in the inner part of the arc piedmont zone the dauphine megamullions formed and then became accentuated during the oligocene and then the neogene tectonic phases which correspond to the last major alpine contractions at relatively shallow structural levels in the sedimentary cover upright or inclined folds were associated with slaty or strain slip cleavage development and low grade metamorphism the corresponding stretching directions locally subvertical trend normal to the regional fold and mega mullions axes and to the mountain belt itself the piedmont megaboudinage took place during the earlier major eocene alpine phase which but for some exeptions did not affect the dauphine zone in the very ductile schistes lustres that surround the dolomitic and ophiolitic megaboudins generalized intrafolial recumbent folding was associated with blueschist metamorphism the deformation characteristic of a deep structural level was a strong flattening within a subhorizontal plane and a preferential elongation parallel to the fold axes owing to regional horizontal festooning those axes trend normal oblique or even parallel to the piedmont zone i e to the incipient mountain belt restored initial trends coeval megaboudinage was probably omnidirectional chocolate tablet pattern the eocene piedmont structure has not been really obliterated during the later alpine deformations leading to megamullions development in the dauphine zone we summarize the very numerous stratigraphical sedimentological and tectonic field observations which lead us to regard each dauphine megamullion as directly inherited from a previous pre alpine faulted block each piedmont megaboudin has a similar origin the corresponding paleofaults are in fact normal and or strike slip faults of truly tethyan age their synsedimentary offset occurred either during the liassic middle jurassic passive margin rifting evolution of the southern edge of the european continent or during the late jurassic opening up of the ligurian oceanic tethys we analyze how those tethyan faults partly induced the style of the alpine collisional structures according to the regional characters of the successive synmetamorphic deformations i e to their localization in the western alps mountain belt

the weathering rates of some sandstone cliffs central weald england short term 1 30 months weathering rates were obtained for steep cliffs of cretaceous ardingly sandstone in southern england using a new photographic method mean rates for an exposed and a sheltered outcrop were 0 11 and 0 033 mm a 1 respectively significant p 0 1 positive correlations were obtained with illumination and algal biomass and a significant negative correlation p 0 05 with slope angle there was no correlation with grain size porosity or mean surface temperature highest weathering rates were observed on south and west facing exposed cliffs the results are discussed with reference to algal growth climate and wind direction

using gravestones to assess changing rates of weathering in the united kingdom weathering rates were calculated using the height difference between lead lettering and marble on gravestones at three sites in the uk comparison of their regression lines and residuals suggested that two of the sites portsmouth and wolverhampton had similar amounts and rates of weathering over the last 100 150 years gravestones in swansea appear to have weathered much more and much faster than gravestones at the other two sites these differences may be the result of the differing pollution and rainfall histories of the three sites

salt weathering and experimental desalination treatment of building sandstone sydney australia local sandstone used in nineteenth century buildings in sydney has been affected by salt weathering and surface crust formation this study trialled two approaches namely washing and vacuuming and poulticing to salt removal treatment of weathered sandstone blocks from the sydney hospital and australian museum both treatments removed solutes from the stones in laboratory tests icp titration of sampled scrapings at depths of 0 2 2 5 and 50 mm showed substantial between sample variation with no significant difference being recorded in solute levels after treatment mann whitney u test except for sulfur and sodium sulfur levels increased at the surface 0 2 mm following washing and vacuuming but not poulticing for the hospital and museum samples sodium levels increased at the surface 0 2 mm following poulticing but not washing and vacuuming for the hospital samples the presence of surface crusts may have contributed to some of the variation in desalination responses

salt weathering influence of evaporation rate supersaturation and crystallization pattern micro and macroscale experiments which document the dynamics of salt damage to porous stone have yielded data which expose weaknesses in earlier interpretations previously unexplained differences are found in crystal morphology crystallization patterns kinetics and substrate damage when comparing the growth of mirabilite na2so4 10h2o and thenardite na2so4 versus halite nacl the crystallization pattern of sodium sulphate was strongly affected by relative humidity rh while a lesser rh effect was observed for sodium chloride macroscale experiments confirmed that mirabilite crystallizing at rh 50 per cent and thenardite crystallizing at rh 50 per cent tend to form subflorescence in highly localized areas under conditions of constant rh and temperature this crystallization pattern was more damaging than that of halite since halite tended to grow as efflorescence or by filling the smallest pores of the stone in a homogeneous fashion a result which contradicts wellman and wilson s theoretical model of salt damage low rh promoted rapid evaporation of saline solutions and higher supersaturation levels resulting in the greatest damage to the stone in the case of both sodium sulphate and sodium chloride crystallization at any particular crystallization condition sodium chloride tended to reach lower supersaturation levels resulting in the crystallization of isometric crystals and created negligible damage while sodium sulphate reached higher supersaturation ratios resulting in non equilibrium crystal shapes resulting in significant damage esem showed no damage from sodium sulphate due to hydration instead after water condensation on thenardite crystals rapid dissolution followed by precipitation of mirabilite took place resulting in stone damage by means of crystallization pressure generation it is concluded that salt damage due to crystallization pressure appears to be largely a function of solution supersaturation ratio and location of crystallization these key factors are related to solution properties and evaporation rates which are constrained by solution composition environmental conditions substrate properties and salt crystallization growth patterns when combined with a critical review of salt damage literature these experiments allow the development of a model which explains variations in damage related to combinations of different salts substrates and environmental conditions

active normal faulting and crustal extension a world wide review of fault plane solutions and focal depths for large normal faulting earthquakes on the continents shows that the overwhelming majority of such earthquakes nucleate in the depth range 6 15 km on faults dipping between 30 and 60 in the few cases where levelling or seismic data are good enough these normal faults are shown to be approximately planar from the surface to their nucleation depth at the base of the brittle crust there is evidence that in some cases as a result of the enormous transitory increase in strain rate during large earthquakes rupture continues into the normally ductile lower crust on surfaces with substantially gentler dips these low angle surfaces may be analogous to some of the detachments seen in metamorphic core complexes of the western usa but the nature of the motion on them depends on strain rate as well as on rheological contrasts between the detachments and the blocks on either side such contrasts however are unlikely to introduce substantial curvature to an originally planar shear zone if the observed spread in active normal fault dips is caused by rotation of the faults and the blocks they bound during extension then a maximum value of 1 7 can be accommodated by seismic activity on a single generation of normal faults with continued extension either a new generation of steeper faults cutting the rotated first faults is likely to form or the deformation will continue aseismically on faults dipping at less than 30 large earthquakes have not been observed to nucleate on very low angle 20 normal faults within the continental crust anywhere in the world such faults can of course move aseismically but are unlikely to do so on a large scale within the upper crust in areas where steep normal faults are seismically active thus extensional models that require concentrated simple shear on large sub horizontal faults within the brittle upper crust will also require a spatial separation between aseismic very low angle faulting and seismic highangle faulting since seismogenic high angle faults dominate the topography of extending regions upper crustal very low angle faulting if it occurs on a large scale presumably does so in areas that are relatively fiat

from hydroplastic to brittle deformation controls on fluid flow in fold and thrust belts insights from the lower pedraforca thrust sheet se pyrenees abstract we present a multidisciplinary study to decipher the controls of deformation on fluid flow regime in fold and thrust belts using the lower pedraforca thrust sheet in the se pyrenees as an example we integrate field based and petrographic observations and geochemical and geochronological data to differentiate seven types of fractures eight types of calcite cement cc1 to cc8 and two sets of stylolites during the deformation stretching the studied thrust sheet during syn sedimentary hydroplastic normal faulting affecting poorly consolidated upper cretaceous and eocene syn orogenic sediments calcite cement did not precipitate during burial bed parallel stylolites formed and cc1 and cc2 precipitated from formation waters in a closed palaeohydrological system during the layer parallel shortening cc3 precipitated from formation waters 5 4 vsmow with 87sr 86sr ratios of 0 707922 and at 70 c cc4 precipitated from formation waters recording different burial conditions as the up to 4 dispersion in 18o of this cement suggests contrarily during folding and thrusting cc5 to cc7 precipitated in an open palaeohydrological system cc6 precipitated from formation waters 5 vsmow with 87sr 86sr ratios of 0 707817 and at 75 c these fluids carried hydrocarbons and probably interacted with upper triassic evaporites an 87sr 86sr ratio of 0 708230 for cc5 indicates that formation waters also interacted with clays within continental deposits during this period stylolites formed in relation to faulting and previous hydroplastic normal faults reactivated as reverse and strike slip faults allowing fluid flow cc7 precipitated after cc6 also from fluids in isotopic disequilibrium with their adjacent host rock the fluid system continued open during the oligocene when cc8 precipitated in normal faults affecting syn orogenic conglomerates deposited during the reactivation of the lower pedraforca thrust sheet the influence of deformation on fluid flow observed in the lower pedraforca thrust sheet is similar to that observed in other fractured areas worldwide

weathering of coastal defensive structures in southwest england a 500 year stone durability trial historic structures can be viewed as exposure trials of the stone of which they are constructed as such they represent a geomorphological weathering experiment several structures of henrician sixteenth century and greater age on the coast of southwest england have been exposed to coastal salt weathering for 500 600 years long term weathering rates on five different rock groups are derived from careful study of weathering depths and forms there is significant variation in weathering rate between five major rock groups rank ordering of weathering rate values reveals a durability order of these rock groups which is confirmed by local juxtapositions controls on rock durability in the coastal weathering environment include both mechanical and mineralogical characteristics specific density and combined quartz and muscovite content are positively related to durability high feldspar and chlorite content are associated with low durability copyright 2000 john wiley sons ltd

geodynamics of rifting and implications for hydrocarbon habitat abstract rifting activity is probably mainly governed by frictional forces exerted on the base of the lithosphere by the convecting sub lithospheric upper mantle combined with deviatoric tensional stresses developing over upwelling branches of the asthenospheric convection system and by far filed stresses controlling the interaction of lithospheric plates moving relative to each other mantle plumes rising from the deep mantle do not appear to be a major driving force of rifting therefore it is questioned whether a distinction between active and passive rifts is still justified lithospheric extension triggers by decompression partial melting of the lower lithosphere and upper asthenosphere magmatic processes contribute materially to thinning of the subcrustal lithosphere and probably also of the lower crust this could explain the frequently observed discrepancy between upper crustal extension by faulting and lower crustal attenuation as defined by refraction and deep reflection seismic data the duration of the rifting stage of palaeorifts and passive margins is highly variable depending on plate interaction crustal separation can be achieved after as little as 7 ma and as much as 280 ma of rifting activity the availability of crustal discontinuities does not appear to play a significant role in the time required for crustal separation to be achieved the structural style of rifts is controlled by the physical state of the lithosphere the mode and amount of its extension and the lithological composition of pre and syn rift sediments subsidence of rift basins is controlled by the balance between isostatic adjustment of the crust to lithospheric stretching and uplift induced by mechanical and thermal attenuation of the subcrustal lithosphere post rift basin subsidence is mainly governed by the decay of rift induced thermal anomalies densification of the lower crust and intra plate stresses provide overprinting effects in view of this it is unlikely that quantitative analyses of post rift basin subsidence give a direct measure of lithospheric extension tectonically active rifts palaeorifts and passive margin basins contain major hydrocarbon provinces their hydrocarbon charge can rely exclusively on pre rift syn rift or post rift sedimentary sequences or a combination thereof maturation of source rocks can be achieved during the syn and or post rift stage of basin evolution during rifting conductive and convective heat transfer accounts for elevated geothermal gradients these play an important role in the maturation of pre and syn rift source rocks thermal gradients decrease asymptotically during the post rift stage

structural evolution of malay basin its link to sunda block tectonics abstract the malay basin is located offshore west malaysia in the south china sea within north central region of 1st order sunda block the basin developed partly as a result of tectonic collisions and strike slip shear of the southeast asia continental slabs as the indian plate collided into eurasia and subsequent extrusion of lithospheric blocks towards indochina the sunda block epicontinental earliest rift margins were manifested by the palaeogene w e rift valleys which formed during nw se sinistral shear of the region later eocene nw se dextral shear of 2nd order indochina block against east malaya block rifted open a 3rd order malay basin developed within it is a series of 4th order n s en echelon ridges and grabens the grabens and some ridges sequentially host w e trending 5th order folds of later compressional episodes the malay basin ridge and graben model explains the multi phased structural deformation which started with the a pre rift palaeo mesozoic crystalline metamorphic basement b synrift phase during paleogene c fast subsidence from late oligocene to middle miocene d compressional inversion of first sunda fold during late miocene and e basin sag during plio pleistocene with mild compressional episodes the subsequent mio pliocene folding history of malay basin is connected to the collision of sunda block against subducting indian australian plate this neogene sunda tectonics to some degree after the cessation of south china sea spreading is due to the diachronous collision along the 1st order plate margins between se asia and australia

seismic characteristics and identification of negative flower structures positive flower structures and positive structural inversion negative and positive flower structures and positive inverted structures imply specific modes of formation and their distinctive characteristics make them important criteria for the identification of certain structural styles a negative flower structure from the andaman sea consists of a shallow synform bounded by upward spreading strands of a wrench fault that have mostly normal separations paralleling monoclines and oblique en echelon normal faults flank the divergent wrench fault a positive flower structure from the ardmore basin oklahoma consists of a shallow antiform displaced by the upward diverging strands of a wrench fault that have mostly reverse separations en echelon folds are present on either side of this convergent wrench fault flower structures may resemble extensional or contractional fault blocks on individual seismic profiles flower structures are identified by their unique internal fault and fold architecture by their association with a straight and throughgoing zone of deformation and by their lack of a consistent sense of separation or regional upthrown side positive structural inversion at the rambutan oil field south sumatra basin has formed a shallow anticlinorium and has partly uplifted the underlying graben deeper fault segments bounding the graben have retained their normal fault profiles but at shallow levels some of these faults have reverse separations similar changes of separation with depth may be produced by strike slip but sets of faults with listric profiles and nearby blocklike trend patterns identify the inversion as a dip slip event where correlation of reflections is uncertain or deep control is unobtainable positive inverted structures may also resemble contrational fault blocks detached normal fault assemblages and certain negative inverted structures

the tectonic evolution of the north celtic sea and cardigan bay basins with special reference to basin inversion abstract the morphology and structural evolution of the north celtic sea basin ncsb and cardigan bay basin cbb are in large part controlled by reactivation of basement features of caledonian and possibly variscan origin from earliest triassic until maastrichtian times sedimentation was almost continuous initially in a rapidly subsiding rift system and finally in a progressive passive sag phase at the onset of the alpine orogeny both basins experienced spectacular inversion along readily identifiable axes the inversion takes the form of a compressive reactivation and reversal of the pre existing growth faults and a broad regional upwarping of the cretaceous depocentre the amount of inversion varies depending on the location within the basin but values in excess of 1000 m are possible by utilising regional seismic data the timing of inversion can be estimated as occurring between maastrichtian and eocene times which correlates with the so called laramide pulse of the alpine orogeny

new evidence for the incision history of the liuchong river southwest china from cosmogenic 26al 10be burial ages in cave sediments cosmogenic nuclides be 10 and al 26 have been analyzed for sediments from the multilevel riverside caves along the liuchong river at the southeastern margin of the tibetan plateau the liuchong river is the northern origin of wujiang river which passes through the northwestern guizhou plateau and cuts down hundreds of meters into the bedrock leaving behind an abundance of multilevel caves the measured al 26 be 10 ratios produced the apparent burial ages in range of 0 49 2 85 ma taking into account of geomorphic and geological backgrounds the dashi cave located at the highest level along the liuchong river system formed around 0 75 ma ago which probably suggests the initial formation age of the modern wujiang river the resulted incision rate of similar to 480 m ma in guizhou in the last 0 75 ma is slightly higher than those in adjacent areas this feature implies an intensive downcutting history of the liuchong river during the quaternary which might be primarily caused by the uplift of tibetan plateau cut through of the three gorges and soluble carbonate bedrock c 2013 elsevier ltd all rights reserved

cretaceous early tertiary inversion tectonism in the danish central trough abstract the inversion of the danish central trough was heralded by a mild precursor during the late hauterivian before rifting had ended the main inversion took place during the late cretaceous it can be subdivided into several sub phases of which those occurring during the turonian santonian mid maastrichtian and post danian early tertiary are the most pronounced minor inversion tectonism occurred more or less continuously between these major events the turonian santonian event had the greatest impact in the northern part of the danish central trough whereas the effects of later events are most pronounced in the south throughout the late cretaceous danian a gradual change from more brittle deformation with faulting to more plastic deformation characterised by folding and flexuring can be seen

frost and salt weathering further experimental results a laboratory experiment has been conducted to examine the effects of frost and salt weathering i e physical breakdown by the freezing of salt solutions on a limestone results show that the presence of certain salts in solution can inhibit frost damage these findings are in direct conflict with those presented by goudie 1974 and more recently williams and robinson 1981 comparison of the experimental methods used in each of these three studies suggests that opposing results can be explained in terms of the different experimental procedures which were employed if salt supply is frequent and plentiful then it seems likely that rock breakdown will be enhanced this is the case represented by the experiment of williams and robinson conversely if the salt supply is limited and the amounts of salt remain more or less constant then rock breakdown will be inhibited the case of the present experimental study caution is therefore advocated when attempting to extrapolate laboratory derived results to infer on the behaviour of rocks under natural conditions several environmental situations in which frost and salt weathering may be a possibility are dsiscussed but it is concluded that further field data especially concerning temperature regimes and salt availability at and below rock surfaces in cold regions would be necessary before more definite statements could be made about the efficacy of this process

fault reactivation by stress pattern reorganization in the hyblean foreland domain of se sicily italy and seismotectonic implications abstract between the october 2011 and the july 2012 several seismic swarms occurred in the hyblean foreland domain of se sicily italy along the cavagrande canyon one of the most impressive fluvial incisions of sicily despite the low magnitude of the events main shock with m 3 7 they represent the biggest strain release of the hyblean area over the last 10 years a careful waveform analysis of the earthquakes revealed that most of them form a family of multiplets these findings allow us to reconstruct the attitude of the accountable fault plane by interpolating their high precision 3d location parameters into a gis platform a detailed morpho structural analysis performed at the ideal updip projection of the modeled plane showed that during the middle late pleistocene the epicentral area has been deformed by a belt of extensional faults a segment of which matches well with the computer generated surface despite the field evidence computed focal solutions support contrasting strike slip kinematics on the same fault plane clearly indicating a dextral shearing on this pre existing normal fault the seismic swarms nucleated on a small rupture area along a 10 km long nw se trending fault segment that could be able to generate m 6 earthquakes following our analysis and looking at seismicity distribution in the se portion of hyblean area we assess that a stress pattern reorganization occurred all over the hyblean foreland between the late pleistocene and present day change in the trajectory of the max stress axes from vertical to horizontal seems to have involved a pre existing large scale fault configuration with considerable seismotectonic implications

luminescence chronometry and geomorphic evidence of active fold growth along the kachchh mainland fault kmf kachchh india seismotectonic implications abstract the kachchh region of western india is a pericratonic basin experiencing periodic high magnitude earthquakes events in 2001 a catastrophic seismic event occurred at bhuj measuring mw 7 7 the epicenters of both the 1956 and 2001 earthquakes were along the kachchh mainland fault kmf proximal to the eastern end of the northern hill range nhr the latter is a topographic expression of an active fault related fold on the hanging wall and is controlled by a south dipping blind thrust the present study deals with the eastern sector of nhr and uses optical dating to reconstruct the chronology of tectonically caused incisions along the backlimb of the nhr incision ages on channel fills and valley fill terraces progressively decrease from 12 ka to 4 3 ka this age progression along with geomorphic evidences decrease in topographic relief drainage capture and drainage migration across the fold nose suggests an active vertical and lateral fold growth along the kmf optical ages suggest that during the late holocene the average uplift rate along the eastern nhr was 10 1 mm a recent gps based estimates on crustal shortening are 12 mm a the kmf and the south wagad fault swf represent the bounding faults of a transtensional basin that formed during the initial rifting this basin is termed as the samakhiali basin the compressive stresses on account of structural inversion from normal to reverse phase resulted in lobate shaped anticlines along kmf and swf zone these anticlines subsequently coalesced and formed linked and overlap segments the present study suggests that eastward lateral deformation across the eastern portion of kmf has continued and has now resulted in its interaction with a left step over transfer fault called the south wagad master fault swmf this implies an increasing transpersional deformation of the samakhiali basin we therefore suggest that the eastward nhr ridge propagation along kmf resulted in the thrust faulting on the south dipping swmf resulting in the bhuj 2001 event the increasing strain on this basin may cause enhanced seismicity in the future along the eastern kmf and wagad region

formation of arcs and backarc basins inferred from the tectonic evolution of southeast asia since the late cretaceous abstract results of the geological and geophysical surveys in the daito ridges and basin in the northern west philippine basin suggest that the daito ridge was an arc facing toward the south from the late cretaceous to the early tertiary the late cretaceous and tertiary history of southeast asia is evaluated based on these data in the daito ridges and basins and reconstructed based on overall plate kinematics that have operated in this area during the late cretaceous the daito ridge and the east philippine islands were positioned along the boundary between the indian and pacific plates the western half of the philippines setting on the indian plate approached from the south and collided with the east philippine daito arc either during the latest paleocene or the earliest eocene it is inferred that the bulk of the philippine archipelago rotated clockwise and borneo spun counterclockwise during the tertiary from the reconstruction the formation of backarc basins and their spreading direction are assessed as a result some primary causes and significant characteristics are suggested for the opening of backarc basins in southeast asia first opening of some backarc basins commenced with or was triggered by collisions second backarc basins opened approximately parallel to oceanic plate motion third the formation of some backarc basins was triggered by the approach of a hot spreading center fourth the spreading mode or direction of backarc basins was greatly affected by the configuration of the surrounding continent and was also rearranged to spread approximately parallel to oceanic plate motion the formation of backarc basins and their spreading direction can be reasonably explained by plate kinematics however the generative force responsible for their formation is possibly within the subduction system particularly to form horizontal tensional force in backarc side

island arc tectonics abstract tectonic stress states in arc backarc systems have been examined on simplified model structures corresponding to the chilean mariana and intermediate arc types two sources of tectonic stress are assumed the stress due to lateral density variations and the stress transmitted from the subducting oceanic plate to the forearc the average vertical stress zz of the former type has been calculated for each isostatically compensated model lithospheric plate using the difference from a reference structure from the sign of xx zz one can estimate whether the tectonic situation is extentional or compressional if we assume that xx is caused by mechanical coupling between the subducting oceanic slab and is laterally constant in one arc backarc system we can estimate at least the upper or lower boundary of the mechanical coupling for the chilean type arcs where the truly great interplate earthquakes occur and no backarc spreading takes place the transmitted average stress must be larger than 660 bar for the mariana type arcs where no large interplate earthquakes are recorded and spreading takes place in the backarc region xx should be smaller than 100 bar in any arc backarc system the most extentional feature is expected at the highest topography of the volcanic arc once spreading has started the viscosity under the backarc region drops dramatically and the spreading will continue in the backarc even if its topography is subdued in comparison with the now separated main and remnant arcs

the dynamics of subduction and trench migration for viscosity stratification summary although subduction plays a dominant role in plate tectonics related processes such as trench migration are not well understood we investigate the influence of viscosity stratification and different flow boundary conditions on the trench migration dynamics of a subducting lithosphere in a 2 d model using a finite difference code subduction and mantle flow are driven by a compositionally prescribed density contrast between the high viscosity slab and the ambient mantle no overriding plate is assumed the model rheology is viscoplastic at shallow and viscous at greater depth the mantle is stratified with a higher viscosity in the lower part of the computational domain the plastic rheology allows the plate to decouple from the top of the box and is described by a simplified friction law to mimic the brittle deformation of the shallow lithosphere the flow patterns and slab morphologies differ as a function of the velocity boundary conditions bcs for reflective bcs we model either a plate which is fixed on the box side or a plate that can freely move a slab with periodic bcs is always laterally free we find that when the slabs interact with the highly viscous lower mantle the slab with reflective bcs is more folded than the periodic one due to the confinement of mantle flow around the slab in general the trench is observed to roll back toward the oceanic plate for free slabs with reflective bcs the trench retreat velocity deceases after the interaction with the lower mantle in contrast for the free slab with periodic bcs it is nearly constant or even increases with time if described in a reference frame fixed to the lower mantle the free slab with periodic bcs exerts a force on the lower mantle which causes a net differential flow between the upper and lower mantle we also carried out additional experiments with different mechanical slab properties and thicknesses stiffer free slabs subduct more steeply and are able to penetrate straight into the lower mantle after penetration into the lower mantle the trench moves toward the continent thinner slabs deform more easily and are folded for all boundary conditions we can generalize the rollback systematics for free slabs by normalizing trench velocities by the plate speed free slabs being more representative of the west pacific subduction zones show large temporal variations of normalized trench velocities ranging between a retreat value of 1 0 to an advancing value of 0 3

linking weathering and rock slope instability non linear perspectives weathering is linked complexly to the erosion and evolution of rock slopes weathering influences both the strength of rock slopes and the stresses that act upon them while weathering has often been portrayed in an over simplified way by those studying rock slope instability in reality it consists of multiple processes acting over different spatial and temporal scales with many complex inter linkages through a demonstration of the sources of non linearities in rock slope weathering systems and their implications for rock slope instability this paper proposes five key linkages worthy of further study copyright 2012 john wiley sons ltd

compressional intra plate deformations in the alpine foreland an introduction abstract the recognition of the basin inversion phenomenon dates back to the 1920 s and 1930 s the true scope of the latest cretaceous and cenozoic basin inversions became apparent only in the 1970 s it is proposed that these intra plate deformations are related to compressional stresses exerted on the foreland during the alpine orogeny

sandbox model studies of inversion tectonics abstract scaled plane strain sandbox models have been used to simulate basement controlled structural inversion in a sedimentary overburden two basement configurations were tested in the first one reversal of movement along vertical and normal faults that controlled a graben relief induced only a partial recovery of displacement along the pre existing overburden faults the inversion produced new reverse faults in the footwall of the pre existing overburden faults the reactivated normal faults and the new reverse faults defined wedge shaped fault blocks at the edges of the inverted structure in the second configuration the relationship between inversion and tilted fault blocks was tested when a tilting basement block does not move parallel to its bounding fault a compression is induced in the overburden which generates an inverted structure bounded by new reverse faults both experiments show that structural inversion not only reactivates pre existing faults but also generates new faults in the overburden faults related to inversion are the result of horizontal compression either associated with rotation of one of the fault blocks or with vertical uplift of basement blocks

structural evolution timing and tectonic style of the sole pit inversion abstract the nw se oriented sole pit high located in the western half of the southern north sea basin is the result of three different structural processes initiated during the late palaeozoic basin subsidence probably related to late hercynian pull apart movements led to continuous sedimentation from the permian to the middle jurassic mid jurassic doming of its eastern flank followed by erosion transtensional movements and differential subsidence until the early cretaceous reflect the mid and late kimmerian crustal distension and fragmentation of the north sea rift basinwide inversion occurred between the turonian and the campanian and was repeated in the oligocene resulting in a total uplift of some 1500 m the present structural style is represented by a complex network of transpressional and transtensional faults at permian rotliegend levels which are thought to represent the upward termination of a series of wrench induced flower structures with a right lateral sense of displacement these faults are detached by zechstein and triassic salt from more orderly transtensional faults systems at shallower levels in areas where salt is absent late kimmerian normal faults became reactivated in a reverse sense during inversion however the relationship of these shallow mappable tectonic components to the deeper pre permian structure of the sole pit high and to the underlying crustal configuration remains speculative

a review of the tectonics of the northern middle east region the structure of the northern part of the arabian platform is reviewed in the light of hitherto unpublished exploration data and the presently accepted kinematic model of plate motion in the region the palmyra and sinjar zones share a common history of development involving two stages of rifting one in the triassic jurassic and the other during late cretaceous to early tertiary times deformation of the palmyra zone during the mio pliocene is attributed to north south compression on the eastern block of the dead sea transcurrent system which occurred after continental collision in the north in southeast turkey the asymmetry of the palmyra zone is believed to result from northward underthrusting along the southern boundary facilitated by the presence of shallow triassic evaporites an important nw se cross plate shear zone has been identified which can be traced for 600 km and which controls the course of the river euphrates over long distances in syria and iraq transcurrent motion along this zone resulted in the formation of narrow grabens during the late cretaceous which were compressed during the mio pliocene to a large extent present day structures in the region result from compressional reactivation of old lineaments within the arabian plate by the transcurrent motion of the dead sea fault zone and subsequent continental collision

seismic stratigraphy and cenozoic evolution of the lombok forearc basin eastern sunda arc abstract on the basis of single and multi channel seismic reflection data the stratigraphic framework and geologic history of the lombok forearc basin is discussed the lombok basin is built on the southeast sunda shelf continental margin and probably underlain by basement of thinned rifted continental crust it represents a broad ridged residual forearc basin which is still in an early stage of evolution five seismo stratigraphic sequences reflecting the cenozoic history and development of the forearc basin south of the islands of bali and lombok were identified the lowermost sequence 1 probably is composed of synrift deposits of paleogene age which predate the initiation of the present convergent margin sequences 2 and 3 reflect two major phases of tectonic evolution of the accretionary prism between the late oligocene and mid miocene sequences 4 and 5 represent slope front fill deposits and reflect both volcanic activity as well as tectonic uplift of the magmatic arc from mid miocene times onwards by the late miocene increased convergence between the subducting indian and overlying asian plates resulted in a stronger mechanical coupling between both plates this was expressed in the southern forearc basin by folding of the oldest basin fill deposits the present tectonic activity in the lombok basin is governed by the late pliocene collision of the accretionary prism with the scott marginal and roo rise oceanic plateaus this resulted in uplift of both the outer arc ridge and the southern part of the forearc basement

sunda java trench kinematics slab window formation and overriding plate deformation since the cretaceous the kinematics and time dependence of back arc extension or compression is one of the most poorly understood aspects of plate tectonics and has nearly exclusively been studied from snapshots of present day observations here we combine absolute and relative plate motions with reconstructions of now subducted ocean floor to analyse subduction kinematics and upper plate strain from geological observations since 80 ma along the 3200 km long sunda java trench one of the largest subduction systems on earth combining plate motions and slab geometries enables us to reconstruct a time dependent slab window beneath sundaland formed through wharton spreading ridge subduction we find that upper plate advance and retreat is the main influence on upper plate strain but subduction of large bathymetric ridges and slab window effects also play a significant and at times dominant role compression in the sundaland back arc region can be linked to advance of the upper plate extension of the sundaland backarc region correlates with two patterns of upper plate motion a retreat of the upper plate and b advance of the upper plate combined with more rapid advance of the sundaland margin due to hinge rollback subduction of large bathymetric ridges causes compression in the upper plate especially wharton ridge subduction underneath sumatra over the period 15 0 ma our reconstructions unravel the evolving geometry of a slab window underlying the java south sumatra region and we propose that decreased mantle wedge viscosities associated with this slab window exacerbated palaeogene extension in the java sea region via active rifting and enabled sumatran continental extension to continue at 50 35 ma when upper plate advance would otherwise have led to compression

geomorphology s role in the study of weathering of cultural stone abstract great monumental places petra giza angkor stonehenge tikal macchu picchu rapa nui to name a few are links to our cultural past they evoke a sense of wonderment for their aesthetic fascination if not for their seeming permanence over both cultural and physical landscapes however as with natural landforms human constructs are subject to weathering and erosion indeed many of our cultural resources suffer from serious deterioration some natural some enhanced by human impact groups from the united nations to local civic and tourism assemblies are deeply interested in maintaining and preserving such cultural resources from simple rock art to great temples geomorphologists trained in interacting systems process and response to thresholds rates of change over time and spatial variation of weathering processes and effects are able to offer insight into how deterioration occurs and what can be done to ameliorate the impact review of recent literature and case studies presented here demonstrate methodological and theoretical advances that have resulted from the study of cultural stone weathering because the stone was carved at a known date to a baseline or zero datum level some of the simplest methods e g assessing surface weathering features or measuring surface recession in the field provide useful data on weathering rates and processes such data are difficult or impossible to obtain in natural settings cultural stone weathering studies demonstrate the importance of biotic and saline weathering agents and the significance of weathering factors such as exposure microclimate and human impact more sophisticated methods confirm these observations but also reveal discrepancies between field and laboratory studies this brings up two important caveats for conservators and geomorphologists for the conservator are laboratory and natural setting studies really analogous and useful for assessing stone damage for the geomorphologist does cultural stone data have any real relevance to the natural environment these are questions for future research and debate in any event cultural stone weathering studies have been productive for both geomorphologists and conservators continued collaboration and communication between the geomorphic historic preservation archaeological and engineering research communities are encouraged

tertiary tectonic and magmatic evolution of western sulawesi and the makassar strait indonesia evidence for a miocene continent continent collision

variable weathering response in sandstone factors controlling decay sequences differences in weathering response characteristics of fine and coarse grained stanton moor sandstone samples were assessed in a laboratory weathering simulation experiment using a variable combination of salt weathering and freeze thaw cycles preliminary analysis of permeability characteristics identified similar mean values for each type of stanton sandstone but significant differences in the range of values between the two sample sets with coarse grained samples of stanton moor sandstone displaying a restricted range of values in comparison to fine grained samples which showed much greater within block variation data indicated that the greater the range in initial permeability values the greater the potential for salt and moisture ingress and retention and hence eventual disruption of the fabric of the stone experimental data also identified different stages in decay sequences with significant structural change occurring during the initial preparatory stage before material breakdown and loss became apparent evidence suggests that relatively minor structural and mineralogical differences between samples of the same stone type can have a significant influence on weathering behaviour resulting in distinct rates and patterns of breakdown copyright 2005 john wiley sons ltd

tectonic analysis of fault slip data sets using data that include the direction and the sense of motion on individual fault surfaces determined by slickenside lineations it is possible to reconstruct reduced stress tensors that correspond to the orientation of stress axes and to the ratio 2 3 1 3 between principal stress values 1 2 3 compression being positive no assumption is made concerning the orientation of fault planes relative to stress axes so that reactived faults are taken into account as well as newly created ones qualitative and quantitative methods for analysis of fault slip data were developed during the last 10 years the practical limitation of the methods and the necessity for critical field observations are emphasized these methods can be applied to focal mechanisms of earthquakes a more complex analysis of heterogeneous data sets involving an iterative separation of different stress systems is also discussed this analysis enables one to distinguish successive faulting events careful qualitative study in the field is in all cases essential

contrasting weathering rates in coastal urban and rural areas in southern britain preliminary investigations using gravestones weathering rates were calculated using the height differences between lead lettering on marble gravestones from inland urban inland rural coastal urban and coastal rural sites within southern britain all sites exhibit similar amounts and variations in rainfall over the study period for which gravestone measurements are available comparison of mean weathering rates suggested that the coastal urban site of clacton had a similar weathering rate to the nearby coastal rural site the other urban sites of oxford lodge hill and portsmouth had similar weathering rates despite their diverse locations and histories the inland rural site had a significantly lower mean weathering rate than any other site analysis of covariance confirms that there are similarities between some sites linear and curvilinear regression of depth of loss against age suggests that a linear regression adequately describes the relationship over the period for which data are available although there are problems with this simple interpretation copyright 2000 john wiley sons ltd

how much does slip on a reactivated fault plane constrain the stress tensor given a fault plane and its slip vector the stress tensor which caused the displacement is sought two constraints are considered first a geometrical constraint that the shear stress applied to the fault plane is parallel to the slip wallace 1951 bott 1959 second a frictional constraint that the shear to normal stress ratio equals tan 0 coulomb 1776 in a first step the stress tensors that satisfy the geometrical constraint are sought for tensors belonging to the vectorial space of solutions shear and normal stress magnitudes become a function of the orientation of the principal stresses and are mapped extending a study by mckenzie 1969 in a second step it is investigated which of these tensors also satisfy the frictional constraint within this more restricted vectorial space there is a relationship between the magnitudes 1 2 1 3 and s 1 3 1 and the orientations of the principal stresses both the range of s and the spatial distribution of are more restricted than when the geometrical constraint alone is considered as when the geometrical constraint is solely considered mckenzie 1969 the orientations of the principal stresses may lie significantly away from and up to right angle to the p b t axes however this can happen only in two cases 1 either the effective stress difference s has reached a high value which is unlikely to happen if enough preexisting fractures are available to release the stress or 2 2 becomes close to either 1 or 3 and therefore barely distinguishable from it in that case the delocalization of the orientations of the principal stresses is best described by a tendency for to exchange role with either or when the stress difference remains small and 2 reasonably away from 1 and 3 approach positions that we define as the pf b tf axes and that are obtained from the p b t axes by a rotation of angle 0 2 around b and toward the slip vector this explains why the p b t axes gives reasonable estimates of the orientations of the principal stresses scheidegger 1964 despite objections mckenzie 1969 however whenever the fault plane can be distinguished from the auxiliary plane pf b tf should give a better estimate raleigh et al 1972 in an area where many fault planes are available and a uniform tensor is assumed the scatter in the plane orientations contains information about both the relative position of 2 represented by and the relative stress difference s the higher s or the closer to either 0 or 1 the more scatter this information could then be extracted by inverse methods because a friction law would constrain these inverse method more tightly it may show the necessity of nonuniform tensor to explain scattered fault plane

tertiary syntectonic carbonate platform development in indonesia cenozoic tropical carbonate sedimentation was strongly influenced by local and regional tectonics in se asia this paper outlines the evolution of the syntectonic eocene to middle miocene tonasa formation of south sulawesi evaluating controls on sedimentation facies distribution and sequence development development of a facies model for this cenozoic tropical carbonate platform provides a meaningful analogue for similar less well studied se asian carbonates which commonly comprise targets for hydrocarbon exploration this study also has considerable implications for the study of syntectonic carbonates controls on carbonate sedimentation carbonate platform development in backarc areas and se asian tectonics detailed facies mapping logging petrographic and biostratigraphic analyses indicate that the tonasa formation was deposited initially as part of a transgressive sequence in a backarc setting by late eocene times shallow water carbonates were being deposited over much of south sulawesi forming a widespread 100 km long platform area shallow water sedimentation continued unabated in some areas of the platform until the middle miocene elsewhere active normal faulting resulted in fault block platforms with local subaerial exposure of footwall blocks and the formation of basinal graben in adjacent hangingwall areas platform top facies were aggradational and dominated by larger benthic foraminifera low angle slopes particularly hangingwall dip slopes were characterized by the development of ramps faults controlled in part by pre existing structures were periodically active and formed steep escarpment margins variable regional subsidence strongly influenced the development of the tonasa carbonate platform whereas platform wide effects caused by regional eustacy have not been identified computer modelling of the tonasa platform confirms that the accommodation space and sedimentary geometries observed can be produced by block faulting and regional subsidence alone modelling also reveals that regional subsidence and extension oblique to the main stretching direction were low on the margins of the backarc basin shallow water accumulation rates for this foraminifera dominated tropical carbonate platform were an order of magnitude lower than those for modern warm water platforms dominated by corals or ooids

longitudinal evolution of the suez rift structure egypt abstract a three dimensional study of the structure of the suez rift has been carried out using field and subsurface data in an attempt to determine the role of transverse faults and the longitudinal evolution of the rift as in most intracontinental rifts the structure of the gulf of suez area is governed by normal faults and tilted blocks whose crests constitute the main target of exploratory wells the fault pattern consists of two major sets of trends 1 1 longitudinal faults parallel to the rift axis and created in an extensional regime where 3 was trending ene wsw and 2 2 transverse faults with a n s to nne ssw dominant trend the transverse faults are inherited passive discontinuities while most of the longitudinal faults were created during neogene times in a purely extensional regime both sets were simultaneously active producing a zigzag pattern and rhombic shaped blocks the transverse faults can show horizontal strike slip components and act as relays between major normal faults although the suez rift appears as a simple narrow elongated trough dominated by two almost symmetrical shoulders its internal structure is asymmetrical cross profiles show that all the major blocks are tilted in the same direction however the tilt direction changes twice along the rift to the north and to the south of the rift the blocks are tilted eastward while in the central part they are tilted westward to the north the change of dip is accompan ed by a graben type twist zone without transverse faulting at least in the neogene series to the south the change of dip is accompanied by a more complex structure involving both a major transverse fault and a horst type twist zone in this latter case the transverse fault does not cut through the entire rift balanced cross sections established from subsurface data show that the tilt angle and the amount of extension increase from north to south while the width of the blocks decreases indicating a pole of opening close to the northern end of the gulf minimum values for the amount of opening range from 5 km in the north to about 20 km in the south

patterns of damage in igneous and sedimentary rocks under conditions simulating sea salt weathering a saline spray artificial ageing test was used to simulate the effects produced in granites and sedimentary rocks calcarenites micrites and breccia under conditions in coastal environments three main points were addressed in this study the durability of the different kinds of rock to salt decay the resulting weathering forms and the rock properties involved in the weathering processes for this mineralogical and textural characterization of each of the different rocks was carried out before and after the test the soluble salt content at different depths from the exposed surfaces was also determined two different weathering mechanisms were observed in the granite and calcareous rocks physical processes were involved in the weathering of granite samples whereas dissolution of calcite was also involved in the deterioration of the calcareous rocks we also showed that microstructural characteristics e g pore size distribution play a key role in salt damage because of their influence on saline solution transport and on the pressures developed within rocks during crystallization copyright 2003 john wiley sons ltd

laboratory simulation of the salt weathering of schist 1 weathering of schist blocks in a seasonally wet tropical environment data describing sediment generation focusing on the temporal evolution of size gradation are required for the prediction of long term landform evolution this paper presents such data for the salt weathering of a quartz chlorite schist obtained from the ranger uranium mine in northern australia rock fragment samples are subjected to three different climate regimes 1 a dry season climate 2 a wet season climate both based on observations at the ranger site and 3 an oven drying sequence designed to test the sensitivity of the weathering process by exposing the rocks to more extreme temperatures two mgso4 salt solutions are applied one being typical of wet season runoff and the other a more concentrated solution salt solution is applied daily in the wet season experiments and once only at the beginning of the dry season experiments results of the experiments reveal four stages of weathering the kinetics of each stage are described and related to the formation of sediment of different sizes wet season climate conditions are shown to produce greater moisture variability and lead to faster weathering rates however salt concentrations in the wet season are typically lower and so when climate is combined with observed salt concentrations the dry and wet season experiments weather at approximately equal rates finally small variations in rock properties were shown to have a large impact on weathering rates leading to the conclusion that rock weathering experiments need to be carefully designed if results are to be used to help predict weathering behaviour at the landscape scale copyright 2006 john wiley sons ltd

sandstone weathering a century of research and innovation abstract a review of sandstone weathering research particularly in the past 100 years reveals a trajectory of enquiry from early description and classification of features to development of process based explanations to decreasing scales of investigation and a disparity between understanding of process es and explanations of the genesis of sandstone weathering features developments in expositions on mesoscale weathering features on sandstone surfaces are discussed demonstrating a range of approaches to weathering phenomena field based and laboratory based that must be linked to provide an explanation of observed features on a landform scale throughout the twentieth century a thematic chronology highlights certain trends in research description of forms often in arid and semi arid environments single process form models an emphasis on experimentation difficulties in measuring weathering rates and a persistent emphasis on physical causes of breakdown a new research agenda is promoted in which biodeterioration and chemical processes gain parity a holistic approach based on conceptual modeling of weathering systems gains prominence and scale issues are addressed more rigorously

fault related folding a review of kinematic models and their application abstract folding that is directly related to fault activity is an important deformation feature that occurs all over the world in mountain belts accretionary wedges fold and thrust belts and intra plate settings in either strike slip compressional or extensional regimes due to their widespread occurrence knowledge about the development of these structures is important to a broad spectrum of geoscience sub disciplines such as structural geology seismology geomorphology petroleum geology and quaternary geology fault related folding has been analyzed intensively over the last 140 years for the sake of this review we divide the folds according to the way the faults and the folds form that is into detachment fault bend and fault propagation folds all fault related folds are caused by changes in fault parameters the simplest method to produce folds is to transport material along faults that have stepped flat ramp flat geometries fault bend fold alternatively the slip can decrease along the length of the fault and depending on whether the fault remains within a detachment layer or steps up through mechanical stratigraphy either a detachment fold or a fault propagation fold is formed respectively detachment folding was first investigated in the early 20th century whereas the full significance of fault propagation folds was recognized quite late in the 1980s seminal work on fault related folding was carried out in the 1930s but quantitative kinematic models have only been available in the last 30 years these models are extremely valuable because they allow a comprehensive understanding of the evolution of fault related folds and lead to more accurate predictions of the sub surface structure from the mid 1990s onwards numerical simulations have been used to identify how fault parameters such as dip and fault bend angle propagation to slip ratio and shape of the trishear zone influence the geometry of the related folding this is directly applicable to the analysis of the shape of anticlines produced however this does not mean that fold geometry is uniquely related to fault geometry on the contrary different kinematic approaches can lead to a similar fold shape

mechanical validation of balanced cross sections the case of the mont terri anticline at the jura front nw switzerland abstract close to north west front of the jura thrust belt in switzerland the mont terri anticline is located at a disruption of the muschelkalk decollement due to a former normal fault numerous geological data are available thanks to a motorway tunnel cross cutting the fold and an underground laboratory original field data two geological maps a borehole and a highway tunnel constrain the inner structure the anticline is characterized by an overturned frontal limb a steep back limb and a ramp cross cutting older normal faults three geological cross sections and three 2d kinematic models are proposed as various combinations of fault bend folding fault propagation folding and detachment folding the main motivation of this study is to illustrate how geometrical constructions can be constrained by the kinematic approach of limit analysis which determines the optimal deformation including faults that verifies mechanical equilibrium and the coulomb criterion matching some of the important kinematic steps assumed in each three interpretations to the optimal deformation leads us to define the compatible ranges of values of the frictional parameters these ranges allow us to assess the likeliness of the important kinematic steps of each kinematic model the present analysis provides a quantitative link between the assumed evolution of the internal structure and the concomitant evolutions of the topography and of the frictional parameters

the role of moisture cycling in the weathering of a quartz chlorite schist in a tropical environment findings of a laboratory simulation long term weathering of a quartz chlorite schist via wetting and drying was studied under a simulated tropical climate cubic rock samples 15 mm 15 mm 15 mm were cut from larger rocks and subjected to time compressed climatic conditions simulating the tropical wet season climate at the ranger uranium mine in the northern territory australia fragmentation moisture content and moisture uptake rate were monitored over 5000 cycles of wetting and drying to determine the impact of climatic variables five climatic regimes were simulated varying water application temperature and drying one of the climatic regimes reproduced observed temperature and moisture variability at the ranger uranium mine but over a compressed time scale it is shown that wetting and drying is capable of weathering quartz chlorite schist with changes expected over a real time period of decades while wetting and drying alone does produce changes to rock morphology the incorporation of temperature variation further enhances weathering rates although little fragmentation occurred in experiments significant changes to internal pore structure were observed which could potentially enhance other weathering mechanisms moisture variability is shown to lead to higher weathering rates than are observed when samples are subjected only to leaching finally experiments were conducted on two rock samples from the same source having only subtle differences in mineralogy the samples exhibited quite different weathering rates leading to the conclusion that our knowledge of the role of rock type and composition in weathering is insufficient for the accurate determination of weathering rates copyright 2005 john wiley sons ltd

a note on fault reactivation reactivation of existing faults whose normal lies in the 1 3 plane of a stress field with effective principal compressive stresses 1 2 3 is considered for the simplest frictional failure criterion n n p where and n are respectively the shear and normal stresses to the existing fault p is the fluid pressure and is the static friction for a plane oriented at to 1 the stress ratio for reactivation is 1 3 1 cot 1 tan this ratio has a minimum positive value at the optimum angle for reactivation given by 12tan 1 1 but reaches infinity when 2 beyond which 3 0 is a necessary condition for reactivation an important consequence is that for typical rock friction coefficients it is unlikely that normal faults will be reactivated as high angle reverse faults or thrusts as low angle normal faults unless the effective least principal stress is tensile

structures and active tectonics of compressionally reactivated back arc failed rift across the toyama trough in the sea of japan revealed by multiscale seismic profiling abstract compressional reactivation of back arc failed rifts in the sea of japan and its mechanism that mobilizes active tectonics based on the crustal structures remains poorly understood here we show new results and interpretations of onshore offshore deep seismic reflection profiles across the toyama trough and its southern extension located in the sea of japan back arc rift to reveal their deep to shallow structures of the crust and reactivated active faults we observed 1 approximately 5 km thick syn and post rift neogene sediments underlain by pre neogene basement rocks characterized by high velocity anomalies and 2 crustal thrust wedges adjacent to the rift axis shallower high resolution seismic reflection profiles also suggest quaternary structural growth of the reactivated thrusts and thrust wedges consistent with tectonic geomorphology of the middle to late pleistocene marine and fluvial terraces these findings demonstrate that the mechanical contrasts between the crustal thrust wedges primarily composed of the pre rift continental crust and high velocity lower crust caused by mafic intrusions in the rifting stage have fundamentally controlled the styles of active deformation during the post rift quaternary compressional stress regime these results also contribute to the construction of the seismic source fault models for tsunamis and seismic hazard estimations of this region in addition we emphasize that combining multi scale seismic reflection profiles with tectonic geomorphology sheds light on complicated structural characteristics and recent activities of reactivated normal faults that are mostly blind because of the dynamic subsidence of failed rift structures

a one dimensional model for simulating armouring and erosion on hillslopes 1 model development and event scale dynamics this paper presents an erosion model armour which simulates time varying runoff erosion deposition and surface armour evolution down a hillslope either as a result of a single erosion event or as the cumulative impact of many events over periods up to decades armour simulates sediment transport for both cohesive and non cohesive soil and dynamically differentiates between transport limited and source limited processes a variety of feasible processes for entrainment of different size classes can be modelled and evaluated against data the generalized likelihood of uncertainty estimation glue technique was used to calibrate and validate armour using data collected during rainfall simulator experiments at two contrasting sites 1 non cohesive stony sediments at ranger uranium mine northern territory australia and 2 cohesive silty sediments at northparkes gold mine nsw australia the spatial and temporal variations of model predictions within the individual runoff events showed that some entrainment processes could not model the spikes in concentration and subsequent depletion while the hiding model of andrews and parker best simulated the concentration trends for both calibrated and independent runoff events armour also successfully captured the coarsening of the surface material though small over the duration of the rainfall simulator trials this was driven by the depletion of the finest size class of the soil for a constant discharge armour simulated higher sediment flux at the start of the storm with the sediment flux and concentration diminishing with time for natural rainfall a power law relationship between sediment flux and discharge was observed the calibration exercise showed that sediment concentration and discharge alone are insufficient to calibrate all aspects of the physics in particular the armour depth this appears to be because the armouring during the short duration events is driven by depletion of the finest classes of the sediments diameters less then 62 5 mm which are not normally measured copyright 2006 john wiley sons ltd

dynamic processes controlling evolution of rifted basins abstract the extension of the lithosphere controlling the development of rifted basins is driven by a combination of plate boundary forces frictional forces exerted on the base of the lithosphere by the convecting asthenosphere and deviatoric tensional stresses developing over upwelling branches of the asthenospheric convection system although mantle plumes are not a primary driving force of rifting they play an important secondary role by weakening the lithosphere and by controlling the level of rift related volcanic activity a distinction between active and passive rifting is only conditionally justified the extension of the lithosphere depending on its rate and magnitude and the potential temperature of the asthenosphere can cause by adiabatic decompression partial melting of the lower lithosphere and upper asthenosphere in rift systems the level and timing of volcanic activity is highly variable the lack of volcanic activity implies passive rifting an initial passive rifting stage can be followed by a more active one during which magmatism plays an increasingly important role magmatic destabilization of the moho may account for the frequently observed discrepancy between upper and lower crustal extension factors combined with evidence for thermal thinning of the mantle lithosphere this suggest that the volume of the lithosphere is not necessarily preserved during rifting as advocated by conventional stretching models the structural style of rifts is controlled by the rheological structure of the lithosphere the availability of crustal discontinuities that can be tensionally reactivated the mode orthogonal or oblique and amount of extension and the lithological composition of pre and syn rift sediments simple shear extension prevails in rifts that subparallel the structural grain of the basement pure shear extension is typical for rifts cross cutting the basement grain pre existing crustal and mantle lithospheric discontinuities contribute to the localization of rift systems the duration of the rifting stage of extensional basins is highly variable stress field changes can cause abrupt termination of rifting in major rift systems progressive strain concentration on the zone of future crustal separation entails abandonment of lateral rifts depending on constraints on lateral block movements crustal separation can be achieved after as little as 9 my and as much as 280 my of rifting activity syn rift basin subsidence is controlled by isostatic adjustment of the crust to mechanical stretching of the lithosphere its magmatic inflation and thermal attenuation of the mantle lithosphere post rift basin subsidence is governed by thermal reequilibration of the lithosphere asthenosphere system deep seated thermal anomalies related to syn rift pull up of the asthenosphere lithosphere boundary have decayed after 60 my by about 65 and after 180 my by about 95 the magnitude of post rift subsidence is a function of the rift induced thermal anomaly and crustal density changes the potential temperature of the asthenosphere and initial water depths intraplate stresses can have an overprinting effect on post rift subsidence stretching factors derived from post rift subsidence analyses must be corrected for such effects

diagenesis and fracturing of a large scale syntectonic carbonate platform abstract the influence of coeval tectonics on carbonate platform development is widely documented yet the diagenesis of such syntectonic platforms is barely evaluated an outcrop petrographic and geochemical study details here for the first time the diagenesis of the tonasa limestone formation developed in an extensional regime in central indonesia this equatorial carbonate system was affected by block faulting tilt block rotation differential uplift and subsidence throughout its eocene to early miocene history wilson 1999 wilson et al 2000 the tonasa carbonate platform is dominated by alteration in shallow to deeper burial depths by fluids with predominantly marine precursor origins mechanical and chemical compaction features are common as are a range of mainly burial related granular mosaic blocky and equant calcite cements earlier marine cements and meteoric influences are rare being highly localised to block faulted highs and or bathymetrically upstanding platform margin areas early marine micritisation of allochems was common on the platform top tectonic uplift together with a major oceanic throughflow current are thought to be key influences on localised karstification meteoric diagenesis and marine cementation the distribution and orientation of faults fractures and calcite veins together with evidence for their relative timing are the strongest manifestation of tectonism coeval with diagenesis there is concordance in the orientation and timing of structures affecting the tonasa platform with those basin wide with the potential for reactivation of pre existing basement fabrics tectonic subsidence including fault associated differential subsidence controlled the degree of burial diagenesis impacting different areas of the platform a predominance of burial diagenetic features and dearth of earlier marine or meteoric cementation is seen in other tertiary equatorial platforms and is partly attributed to 1 predominance of non framework building larger benthic foraminifera and or algae that are prone to remobilisation have low production rates and limited potential to build to sea level and 2 high runoff due to the equatorial humid climate contributing to lowered marine salinities in se asia underlying tectonic reasons for the preponderance of a regional diagenetic signature over a syntectonic one fracturing excepted are 1 development on the flanks of a backarc basin not on typical continental crust 2 key platform influencing structures are oblique to the main extensional direction in the basin and 3 development in an overall subsiding tectonic regime post dating basin initiation the aim here is that this study will contribute to understanding diagenetic alteration of syntectonic carbonate platforms and those from equatorial regions

far field contractional polarity changes in models and nature abstract a change in contractional polarity occurs when the direction of tectonic transport switches along strike this switch is conditioned by lateral variations in rheology or inherited asymmetries such as contrasts in structure or changes in the polarity of subduction zones the parameters controlling contractional polarity changes are less understood in situations when the strain is transferred at large distances from indenters analysing this type of strain transfer is critical for understanding the mechanics of thrusting in fore or back arc settings of orogenic areas comparison of crustal scale analogue modelling with the inversion of the black sea back arc and the formation of the new guinea new britain fore arc suggest that far field changes in contractional polarity are related to rheological contrasts across inherited normal faults the initial extension creates rheological weak zones that localize the subsequent far field contractional deformation along groups of thrusts with opposite vergence along the strike of the system the largest amount of far field contractional deformation is recorded in the transfer zone located between the two indenters moving in opposite directions and is particularly high when inverting oblique extensional systems

inversion of pre orogenic extensional basins in the external western alps structure microstructures and restoration during collision continental margins are shortened along with the inversion inherited syn rift basins in this contribution we explore the internal deformation of pre orogenic basins during their inversion in the external western alps new structural and microstructural data allow us to provide a new kinematic scenario for the shortening of two inherited basins in the oisans external crystalline massif two cleavages and three vein sets are documented by field observations in the sedimentary cover metamorphosed in the greenschist facies their spatial and temporal development is strongly dependent on the structural style that is controlled by the initial basin geometry in the basement shear zones accommodate the shortening while the cover is disharmonically folded we present a new approach for the restoration of cross sections where ductile deformation prevailed thus for which classical methods do not apply both length conservation for basement top and area conservation for the sedimentary cover as well as fixed hinge kinematics for the cover folds are assumed such restoration is discussed in the light of cover strain ellipsoid quantification based on field data analysis we apply this approach to the morcles nappe and propose a new restored geometry which is further compared to the oisans section