changing climate changing process implications for salt transportation and weathering within building sandstones in the uk salt weathering is a crucial process that brings about a change in stone from the scale of landscapes to stone outcrops and natural building stone facades it is acknowledged that salt weathering is controlled by fluctuations in temperature and moisture where repeated oscillations in these parameters can cause re crystallisation hydration de hydration of salts bringing about stone surface loss in the form of for example granular disaggregation scaling and multiple flaking however this traditional view of how salt weathering proceeds may need to be re evaluated in the light of current and future climatic trends indeed there is considerable scope for the investigation of consequences of climate change on geomorphological processes in general building on contemporary research on the deep wetting of natural building stones it is proposed that as stone may be wetter for longer ion diffusion may become a more prominent mechanism for the mixing of molecular constituents and a shift in focus from physical damage to chemical change is suggested data from ion diffusion cell experiments are presented for three different sandstone types demonstrating that salts may diffuse through porous stone relatively rapidly in comparison to for example dense concrete pore water from stones undergoing diffusion experiments was extracted and analysed factors controlling ion diffusion relating to time of wetness within stones are discussed continued saturation connectivity of pores mineralogy behaviour of salts sedimentary structure and potential changes in system dynamics as a result of climate change are addressed system inputs may change in terms of increased moisture input translating into a greater depth of wetting front salts are likely to be stored differently in stones with salt being in solution for longer periods during prolonged winter wetness this has myriad implications in terms of the movement of ions by diffusion and the potential for chemical change in the stone especially in more mobile constituents leading to a weakening of the stone matrix grain boundary cementing the output may be mobilisation and precipitation of elements leading to for example uneven cementing in the stone this reduced strength of the stone or compromised ability of the stone to absorb stress is likely to make crystallisation a more efficacious mechanism of decay when it does occur thus a delay in the onset of crystallisation while stonework is wet does not preclude exaggerated or accelerated material loss when it finally happens

salt weathering simulations under hot desert conditions agents of enlightenment or perpetuators of preconceptions because of access difficulties and inhospitable environmental conditions our understanding of rock weathering in hot deserts has been strongly influenced by laboratory simulations however a risk exists that results may come to owe more to experimental design than to actual environmental conditions experienced at the atmosphere rock surface interface this was especially true in early salt weathering simulations that seemingly sought to reinforce the orthodoxy of a physically dominated weathering environment driven by extremely high absolute temperatures and large diurnal temperature ranges however improvements in environmental sensors over the last 20 years have established the complexity of desert climates and the importance of microclimatic controls and allowed considerable refinement of experimental design this overview evaluates the implications of recent simulation studies and presents new information on possible fatigue effects of differential thermal expansion of salts and the salt weathering of test blocks under compressive loading in doing so it demonstrates how physical rock properties change during experimentation the importance of short term surface temperature fluctuations distinctions between the weathering of unconfined debris and larger rock surfaces the importance of moisture and salt applications that replicate their availability in deserts the importance of rock thermal properties in controlling their weathering response in environments dominated by radiative heating and cooling and the overall complexity of weathering regimes

effects of direct and indirect heating on the validity of rock weathering simulation studies and durability tests rock surface and subsurface temperature responses in samples exposed to direct heating insolation under natural hot desert conditions reveal considerable variability between lithologies related to differences in thermal properties especially albedo and thermal conductivity however when the same samples are heated indirectly by air in an oven based environmental cabinet lithological differences in temperature response disappear and all samples attain temperatures similar to the air temperature within the cabinet rates and patterns of rock decay produced in such environmental cabinets may not therefore reflect those encountered under natural conditions where breakdown is related to micro environmental conditions at the rock air interface and where rock temperature is one of the most important controlling factors in addition to implications for assessment of weathering effectiveness use of only indirect forms of heating affects the determination of comparative rock durability because all rock types are cycled through the same temperature regimes because temperature exerts such a major control on rock breakdown through its control on physical and chemical weathering processes all significant factors influencing it must be included in the design of weathering simulations and durability tests

daytime rock surface temperature variability and its implications for mechanical rock weathering tenerife canary islands summary summer and winter rock surface temperature measurements are presented from three sites along an altitudinal gradient significant between and within site variability is recognised related to insolation cloud cover and air temperature differences maritime influences and time of year the variability argues against the use of a single rock temperature regime to characterise hot desertic environments in for example weathering simulation studies superimposed upon diurnal patterns of heating and cooling are numerous short 3 15 minutes and medium term 1 2 hours fluctuations related to wind speed and cloud cover variations rates of surface temperature change are very high during these fluctuations 3 c minute and it is proposed that they may enhance the operation of a number of mechanical rock weathering mechanisms

first palaeomagnetic results from the cycladic massif greece and their implications for miocene extension directions and tectonic models in the aegean abstract the aegean region is characterised by major fault bound blocks with markedly contrasting structural trends recent models account for these variations either through differential block rotation or through a process of radial extension the cycladic massif in the back arc region to the hellenic trench represents a critical area where apparently divergent extension directions are observed this contribution provides the first palaeomagnetic results from this area magnetic remanence and ams data are presented for middle miocene granodiorites on the islands of mykonos and naxos these rocks are exposed in the footwalls of major extensional detachments within the metamorphic core complexes that characterise the cycladic massif a clear correlation between the orientation of an l s fabric developed within the intrusions and the magnetic fabric data is observed demonstrating the presence of a normal magnetic fabric of extensional origin the mean extension directions inferred from the orientations of the maximum axes of the magnetic susceptibility ellipsoids are markedly divergent at 064 mykonos and 351 naxos northeasterly in situ magnetic remanences are observed on mykonos whereas those on naxos are directed to the nnw neither direction corresponds to the appropriate palaeomagnetic reference direction for the miocene standard palaeomagnetic tilt corrections cannot be applied at these sites because of the lack of palaeohorizontal markers deviations of in situ remanences away from the reference direction are potentially due to rotation around any one of an infinite number of net tectonic rotation axes each of these may be arbitrarily decomposed into components of tilting and vertical axis rotation geologically realistic solutions which restore the in situ magnetisations back to the reference direction may be found by consideration of regional structural trends assuming that tilting is controlled by the major block bounding faults these solutions indicate significant components of differential vertical axis rotations across the cyclades mykonos is bound by nw se trending regional faults and is shown to have rotated clockwise by ca 22 in contrast naxos is bound by ene wsw trending structures and has rotated anticlockwise by ca 33 the apparent divergence of extension directions inferred from both the magnetic anisotropy and structural data is resolved by correcting the mean ams data for subsequent rotation using the rotation solutions derived from the magnetic remanence data the data imply that the primary middle miocene extension direction in the cycladic massif was nearly uniform along a nne ssw azimuth we consider that the uniform extension direction and opposing senses of block rotation determined for this portion of the cycladic massif are most consistent with a recent model describing deformation within the aegean in terms of a system of broken fault bounded slats within this scenario mykonos occupies a position on a clockwise rotating slat which continues northwest at least as far as evvia a major ene wsw trending fault between the islands previously identified on shallow seismic sections separates this domain from an anticlockwise rotating slat which includes naxos

strain reversal a windows program to determine extensional strain from rigid brittle layers or inclusions abstract an on line windows based computer program to calculate extensional strain from the separation of rigid brittle layers or inclusions is presented the program uses the incremental strain reversal methodology rather than traditional finite length methodologies this approach not only provides a better estimate of the extensional strain suffered by the system but also allows for fracture and separation histories to be studied an example application is included based on boudinaged belemnites from the french alps to show the facility of the program which can be downloaded direct from the world wide web

a simple theoretical approach to the thermal expansion mechanism of salt weathering abstract the traditional plate theory in solid mechanics is used to estimate the thermal stress caused by a superficial salt layer on a rock substrate this preliminary investigation theoretically demonstrates that the thermal expansion of superficial salt layers is difficult to result in rock breakdown during the process of salt weathering

phase relationships of sursassite and other mn silicates in highly oxidized low grade high pressure metamorphic rocks from evvia and andros islands greece high pressure low temperature metamorphic mn rich quartzites from andros and evvia euboea islands greece situated in the eocene blueschist belt of the hellenides reveal different mn al ca mg silicate assemblages in response to variable metamorphic grade on evvia piemontite and or braunite rich quartzites which are associated with low grade blueschists t 8 kbar show the principle mineral assemblage quartz montite sursassite braunite mg chlorite hematite rutile titanite the mn al silicate sursassite basically mn2 ca 4 al2 al fe3 mn3 mg 4si6o21 oh 7 thus far reported as a rare mineral locally occurs as a rockforming mineral in cm to m thick layers on andros higher grade quartzites t 450 500 c p 10 kbar of similar composition contain the assemblage quartz piemontite spessartine braunite mg chlorite hematite phengite phlogopite rutile rare sursassite is present only as a relict phase additional mostly accessory minerals in quartzites from evvia and andros are ardennite na amphibole acmitic clinopyroxene albite apatite and tourmaline the chemical composition of the main phases is characterized in detail

selective weathering of cross bedded layers forming shelters and small caves on akopan tepui venezuela field laboratory and experimental evidence about diagenesis and weathering of the mataui formation arenites roraima supergroup middle proterozoic abstract south american table top mountains tepuis are formed by quartzites and sandstones of mataui formation belonging to the roraima supergroup lower to middle proterozoic field observations in the northern part of akopan tepui in venezuela revealed that unlike the beds with flat bedding the cross bedded layers are commonly affected by selective weathering expressed by depressions shelters and even small caves all the arenites are fine grained most of them are likely of aeolian origin hardness measurements confirmed that the cross bedded layers are softer than the flat bedded or structureless beds occurring above and below them petrographic analysis showed that the rocks are mostly fine grained quartzites to quartz sandstones with original sand grains overgrown by syntaxial quartz cement and bearing signs of compaction manifested by local pressure solution some intergranular spaces are filled by newly formed phyllosilicates paragonite locally intergrown with muscovite in the overlying beds no porosity was observed by microscopic study and under sem whereas in the underlying rocks signs of slight weathering and etching of phyllosilicates was observed together with locally widened spaces along the grain to grain boundaries the samples from cross bedded layers display weathering the degree of which depends on the present access of flowing water where water has periodical access to the arenite it shows dissolution of quartz cement arenization together with complete leaching and removal of the phyllosilicates due to lateritization the intergranular spaces are considerably widened and quartz grains bear signs of strong skeletal etching and pitting samples from the sites where the water access ceased show mostly leaching of phyllosilicates with weak skeletal dissolution of quartz grains without pitting to imitate the origin of structures observed in the field experimental modelling was performed using artificially layered and compacted fine grained sands on which sodium silicate solution was dripped during soaking downward preferential penetration of the solution along the cross bedding laminae funnel flow was observed in the cross bedded layer the resulting structures display good lithification of horizontally layered sands and relatively poorer lithification of the cross bedded sediment between them showing triangular shaped overhangs and shelters which mimic those on the akopan tepui differential weathering of otherwise petrologically very similar arenites indicates that there had to be a difference in the initial porosity in the time of the rock denudation a preserved porosity in the cross bedded layers was necessary for the water rock contact to perform dissolution

near surface temperature cycling of stone and its implications for scales of surface deterioration abstract many previous studies into internal temperature gradients within stone have assumed smooth exponential increases and decreases in sub surface temperatures in response for example to diurnal patterns of heating and cooling and these have been used to explain phenomena such as large scale contour scaling this high resolution experimental study in which a porous limestone block was subjected to alternate surface heating and cooling using an infrared lamp demonstrates that internal temperature gradients in response to short term environmental cycles measured in minutes can in fact be complex and inconsistent results confirm the significance of very steep temperature stress gradients within the outer 10 mm or less of exposed stone below this the data indicate complex patterns of temperature reversals the amplitudes of which are attenuated with depth and which are influenced in their intensity and location by variations in the relative duration of heating and cooling phases it is suggested that the reversals might represent interference patterns between incoming and outgoing thermal waves but whatever their origin they are potentially important because they occur within the zone in which many stone decay processes especially salt weathering operate these processes invariably respond to temperature and moisture fluctuations and short term interruptions to insolation could for example trigger these fluctuations on numerous occasions over a day in particular the reversals occur at a scale that is commensurate with decay by multiple flaking and could indicate an underlying control on this previously little researched pattern of weathering in the context of this publication however the main lesson to be learned from this study is that differing scales of behaviour require different scales of enquiry

from ductile to brittle evolution and localization of deformation below a crustal detachment tinos cyclades greece 1 the cycladic oligo miocene detachment of tinos island is an example of a flat lying extensional shear zone evolving into a low angle brittle detachment a clear continuum of extensional strain from ductile to brittle regime is observed in the footwall the main brittle structures marking extension are shallow and steeply dipping normal faults associated with subvertical extensional joints and veins the earliest brittle structures are low angle normal faults which commonly superimpose on and reactivate earlier precursory ductile shear bands but newly formed low angle normal faults could also be observed low angle normal faults are cut by late steeply dipping normal faults the inversion of fault slip data collected within and away from the main detachment zone shows that the direction of the minimum stress axis is strictly parallel to the ne sw stretching lineation and that the maximum principal stress axis remained subvertical during the whole brittle evolution in agreement with the subvertical attitude of veins throughout the island the high angle of 1 to the main detachment suggests that the detachment was weak this observation together with the presence of a thick layer of cataclasites below the main detachment and the kinematic continuum from ductile to brittle leads us to propose a kinematic model for the formation of the detachment boudinage at the crustal scale induces formation near the brittle ductile transition of ductile shear zones near the edges of boudins shear zones are progressively exhumed and replaced by shallow dipping cataclastic shear zones when they reached the brittle field most of the displacement is achieved through cataclastic flow in the upper crust and only the last increment of strain gives rise to the formation of brittle faults the formation of the low angle brittle detachment is thus prepared by the ductile shear zone and the cataclasites and favored by the circulation of surface derived fluids in the shear zone

geochemistry and particle size of surface sediments of gulf of manfredonia southern adriatic sea abstract in this study we describe mechanisms influencing the spatial distribution of the surface sediments in the gulf of manfredonia seventy three samples were collected on a regional grid and analyzed for grain size major and trace elements and organic matter content sediments contain marine derived carbonate as well as terrigenous fractions indicating highly heterogeneous sediment composition dictated by different provenance and complex transport processes principal component analysis provides information about processes involved in the formation and dispersal of the sediments the regional sediment distribution is function of the gulf s morphology and sedimentary inputs from fluvial sources mainly from the ofanto river and from the north and central adriatic basin biogenic carbonate reefs identified in two restricted coastal areas add complexity to sediment shelf dispersal the north adriatic current flowing southward transports and deposits sediments from the northern basin in the offshore area of the gulf while an inner anticyclonic current distributes and mixes northern and fluvial sediment with a clockwise pattern in order to better assess the fluvial contribution also bedload samples from the main river debouching into the gulf were sampled enabling the identification of geochemical indexes to distinguish the role of both fluvial inputs and hydrodynamic processes affecting solid particles dispersion within the gulf this study provides a contribution to a qualitative estimate of the sediment supply entailed in the southwestern adriatic basin

bioprotection and disturbance seaweed microclimatic stability and conditions for mechanical weathering in the intertidal zone as well as their destructive roles plants animals and microorganisms contribute to geomorphology and ecology via direct and indirect bioprotection which can reduce weathering and erosion for example indirect bioprotection can operate via biotic influences on microclimate whereby physical decay processes associated with fluctuations in temperature and moisture salt crystallization thermal fatigue and wetting drying are limited in the intertidal zone the spatial and temporal distribution of macroalgae seaweeds is patchy related to physical and ecological conditions for colonization and growth and the nature and frequency of natural and anthropogenic disturbance we examined the influence of seaweed canopies fucus spp on near surface microclimate and by implication on conditions for mechanical rock decay and under canopy ecology monitoring on hard artificial coastal structures in south west england uk built from limestone and concrete showed that both the range and maxima of daily summertime temperatures were significantly lower by an average of 56 and 25 respectively in areas colonized by seaweed compared to experimentally cleared areas short term microclimatic variability minutes hours was also significantly reduced by an average of 78 for temperature and 71 for humidity under algal canopies during low tide events using seaweed as an example we develop a conceptual model of the relationship between biological cover and microclimate in the intertidal zone disturbance events that remove or drastically reduce seaweed cover mediate shifts between relatively stable and unstable states with respect to mechanical decay and ecological stress associated with heat and desiccation in urban coastal environments where disturbance may be frequent facilitating the establishment and recovery of canopy forming species on rocks and engineered structures could enhance the durability of construction materials as well as support conservation planning and policy targets for biodiversity enhancement

weathering of sandstone by the combined action of frost and salt preliminary results from a continuing series of laboratory experiments designed to examine the combined effects of salt and frost weathering indicate that some salts greatly enhance the breakdown of rocks by frost samples of ardingly sandstone from southeast england were soaked in saturated solutions of sodium chloride or sodium sulphate and subjected to alternating cycles of freezing and thawing rapid disintegration of the sandstone occurred within twenty cycles in each of the salt solutions in contrast samples subjected to freezing and thawing in deionized water suffered very little damage unless they were saturated under vacuum when samples were subjected to twenty cycles of wetting and drying at temperatures above 0 c those soaked in deionised water or sodium chloride suffered no appreciable damage but those soaked in sodium sulphate rapidly disintegrated tentative explanations of these results are offered the enhancement of frost weathering by salt appears to have been overlooked by many writers yet it is likely to be an important geomorphological process in those areas of mid and high latitudes where rocks are saturated with sodium salts

rock temperatures as an indicator of weathering processes affecting rock art to aid rock art conservation rock temperatures have been monitored at different depths and at low 30 min and high 1 min acquisition rates in a painted rock shelter in the ukhahlamba drakensberg park south africa preliminary data for winter cold and dry show that in that season cryoclasty is unlikely to occur rare subzero thermal events and probable reduced moisture availability and thermal shocks are improbable highest measured t t 2 c min 1 high amplitude about 30 c rock temperature cycles accompanied by reversals of the thermal gradient have been observed to occur almost daily and hint at the possibility of thermal stress fatigue copyright 2006 john wiley sons ltd

weathering of rock art at two sites in the kwazulu natal drakensberg southern africa sediments of the karoo basin in southern africa represent one of the world s finest laboratories for investigating sandstone weathering the natural breakdown of these sandstones most notably in the clarens formation is destroying much of the indigenous rock art heritage that exists there in an attempt to elucidate the operative weathering processes a range of micro climatic rock temperature rock moisture rock chemistry and rock property data have been monitored over a 15 year period at two sites in the kwazulu natal drakensberg results suggest that rock moisture regimes and to a lesser extent rock thermal regimes exert the most damaging influence on san paintings it is argued that granular disintegration and the enlargement of existing sandstone pores and bedding planes close to the rock surface facilitate an increasingly dynamic moisture regime which leads to an accelerating rate of weathering recent technological advances in data collection suggest that a re evaluation of environmental controls may be necessary before weathering at a scale appropriate to the deterioration of rock art can be fully understood the continued existence of indigenous rock art in southern africa depends on investigations aimed at the development of techniques for its preservation

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

late orogenic doming in the eastern betic cordilleras final exhumation of the nevado filabride complex and its relation to basin genesis the geometry timing and kinematics of late orogenic extension in the betic cordilleras pose the problem of a decoupling of upper crustal and lower crustal deformation regimes perpendicular directions of extension in metamorphic domes and nearby sedimentary basins remain unexplained this paper puts kinematic constraints on the final exhumation of the nevado filabride complex focusing on the formation of metamorphic domes and their relations with the adjacent basins structural fabrics and kinematic indicators below the main shear zones as well as their relations with both published changing metamorphic p t conditions and geochronological data were studied our approach describes 1 a consistent top to the west shear parallel to dome axes of during d2 i e during decompression with distributed ductile flow and the onset of strain localization along major shear zones 2 further strain localization along the major shear zones under greenschist facies conditions during d3 leading to s c mylonites formation accompanied with a rock strong thickness reduction 3 the divergence of shear direction on either limbs of domes during d3 showing the appearance of the dome geometry and 4 a local evolution toward n s brittle extension d4 in the upper plate and formation of sedimentary basins continuous ductile to brittle top to the west shear is compatible with the slab retreat hypothesis from the miocene the formation of domes which adds gravitational forces responsible for the final stages of exhumation is thus characterized by important kinematics changes necessary to explain coeval n s opened basins later from the upper tortonian a contractional event d5 amplified the earlier domal structures forming the present north vergent folds

relation between the intensity of deformation and retrogression in blueschist metapelites of tinos island greece evidenced by chlorite mica local equilibria the late greenschist deformation of the cycladic blueschists unit on tinos island evolves along a ne sw gradient of non coaxial strain across a major extensional shear zone deformation is more intense and the greenschist overprint is also more severe close to the shear zone that separates the cycladic blueschists from the upper ophiolitic unit in the ne of the island the compositional variability of chlorite and k white mica kwm in metapelites sampled along a ne sw cross section is characteristic of their p t conditions of crystallization and is mainly characterized by variations of their si al fe and mg contents due to the tschermak substitution siiv fe mg vi alvialiv multi equilibrium p t estimates based on the assumption of local equilibrium indicate that each sample recorded a part of the p t history which depends on the distance to the contact to the main shear zone i e the intensity and the pattern of deformation the combination of p t estimates obtained from all the samples collected along the transect provides a continuous p t path which is composed of two parts it provides insights on the syn and post orogenic exhumation for some of the cycladic blueschists in particular we could distinguish two stages in the exhumation process a first stage in the blueschist facies occurred along a cold p t path during the construction of the hellenides the second exhumation stage occurred along a warmer p t path during the formation of the aegean sea between the two stages of exhumation there is a thermal reequilibration of the crust and a partial thermal overprint of the blueschist parageneses

low angle faults above and below a blueschist belt tinos island cyclades greece new observations from the island of tinos greece allow a better definition of the structural position of the alpine eocene blueschist belt exposed in the islands of the aegean sea these blueschists over a significant part of the aegean sea are delimited from below by a low angle thrust fault while from above they are delimited by a low angle normal type fault which omits a substantial crustal interval both underlying and overlying rocks were not affected by the high metamorphism the rapid uplift and exhumation of the high rocks was therefore mainly the result of fault movements rather than erosion and whole crust uplifting the low angle normal fault apparently had a major role in the uplift of the blueschists

heavy metals in sediments from different environments of a northern adriatic sea area italy sediments from different environments of an area directly affected by the discharge of the po river and 13 other minor rivers have been studied three main sources of metals and several distribution mechanisms can be identified concentration profiles of metals in a core allow one to establish background levels of finegrained sediments for cd hg pb and zn seabed sediments do not appear to be very polluted mainly because of desorption and dilution processes

normal faulting in the upper continental crust observations from regions of active extension abstract observations of present day normal faulting in regions of active continental extension may be helpful when interpreting the geological record in older extensional basins the most obvious manifestation of active extension is normal faulting in earthquakes earthquake foci are mostly confined to the upper seismogenic continental crust whose thickness imposes a scale on the observed deformation large earthquakes move faults with lengths similar or large compared with the thickness of the seismogenic layer large seismogenic normal faults on the continents appear to be restricted to a dip range of around 30 60 dips significantly gentler than 20 have not been observed in fault plane solutions of large earthquakes large seismographic normal faults are approximately planar in cross section and cut through the base of the upper seismogenic layer rotating about a horizontal axis as they move a reasonable estimate of the regional extension can often be made from the dip of the large normal faults and the tilt of the blocks they bound the domino model such faults are rarely continuous for more than 15 20 km but commonly change strike or step in an en echelon fashion this segmentation may occur on a scale controlled by the thickness of the seismogenic layer and is an important influence on sedimentation and drainage these observations are common to large seismogenic normal faults from a variety of tectonic settings and suggest that the kinematics of normal faulting may not be strongly influenced by the forces responsible for the extension which can vary widely in nature and magnitude small earthquakes which move faults that are small compared with the seismogenic layer thickness show no simple pattern and often can be interpreted as internal deformation of blocks bounded by large faults in some places the seismogenic basement faults do not reach the surface but are decoupled from the sedimentary cover by layers of weak lithology faults in the sedimentary cover may be strongly curved in cross section requiring their hangingwalls to deform internally estimating extension from such faults is not straightforward and requires a knowledge of the hangingwall deformation estimates made in this way are often very non unique and prone to large errors we postulate that the thickness of the seismogenic upper crust controls both the maximum length of large normal fault segments along strike and the maximum size of blocks that can rotate coherently about a horizontal axis

east west extension and holocene normal fault scarps in the hellenic arc examination of surface fault traces with spot images and in the field corroborates the inference that the active tectonics of southern peloponnesus and crete are dominated by approximately north south normal faulting and approximately east west extension the heights of holocene normal fault scarps yield first order regional estimates of fault slip rates between 0 1 and 2 3 mm yr most of the surface scarps probably ruptured during past earthquakes such as that which destroyed sparta in 464 b c on the sparta fault the holocene average slip rate and the recurrence time of large earthquakes may be 1 mm yr and 3000 yr respectively the regional pattern of quaternary faulting suggests that the east west extension near the hellenic subduction zone is fast about 5 10 m y the change from north south to east west extension in the late pliocene 2 4 ma implies that the aegean is starting to collide with the northern margin of africa

characterization and modeling of the cemented sediment surrounding the iulia felix glass abstract about 1800 years ago a roman corbita sunk off the coast of italy carrying a barrel of glass cullet to the floor of the adriatic sea samples of glass cullet and the cemented surrounding sediment have been characterized and the reaction between the glass and the sea water saturated with respect to calcite and dolomite has been modeled results from characterization and modeling show that the phase surrounding and cementing together the sediment grains is a high mg calcite we find that the origin of this cementing phase is likely the reaction between the glass and the sea water to form a mg silicate here modeled as sepiolite mg 4 si 6 o 15 oh 2 6 h 2 o

a comparison of geodetic and finite strain pattern in the aegean geodynamic implications abstract a comparison of the active strain pattern of the aegean constrained by global positioning system measurements and the oligo miocene finite strain field shows some striking similarities in terms of direction and rates of extension the geometry of extension at crustal scale is also very similar with north dipping normal faults connecting near the brittle ductile transition to shallow north dipping shear zones this pattern of extension is not significantly modified by the recent extrusion of the motion of anatolia and aegea the persistence over more than 25 myr of the same pattern of extension suggests that the cause for extension resides within the aegean lithosphere gravitational collapse allowed by extensional boundary conditions after 30 ma slab retreat is the primary cause for post orogenic extension in the aegean and western anatolia

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

geochemistry of ferromanganoan metasediments from the island of andros cycladic blueschist belt greece abstract on the island of andros cycladic blueschist belt metamorphosed ferromanganoan sediments occur in widespread lateral distribution they form concordant layers and lenses within a uniform sequence of quartz rich metapelitic schists which can be derived from pelagic siliceous mudstones three main types of ferromanganoan metasediments were geochemically investigated 1 piemontite spessartine and piemontite quartzites psq containing braunite rich lenses 2 spessartine quartzites sq and 3 napyroxene quartzites npxq textural and geochemical evidence leads to the conclusion that psq is derived from a mn nodule bearing sediment consisting of a mixture of terrigenous illitic clay with biogenic radiolarian ooze compared to recent nodule bearing sediments psq is markedly enriched in cu pb sr and as we assume that these elements were mobilized during diagenesis and or early metamorphism from the sedimentary column and were subsequently concentrated in minerals like piemontite ardennite and braunite under highly oxidizing conditions in contrast to psq sq and npxq are derived from parent sediments rich in smectite sq shows a higher al fe ratio in rock composition than npxq and may change into npxq by a decreasing content of spessartine while sq is chemically equivalent to a montmorillonitic clay mn 2 na almost spessartine free npxq can be derived from fe rich nontronitic clay na mn 2 required for the formation of sq was probably mobilized from adjacent mn nodule bearing sediments psq

deformation of granitoids at low metamorphic grade i reactions and grain size reduction abstract deformation and chemical reaction in granitoids at greenschist facies conditions were investigated in samples from three shear zones two from the alps corvatsch granodiorite and aiguilles rouges granite switzerland and one from eastern australia wyangala granite when examined by light and electron microscopy all show similar features of deformation that progressed from coarse parent rock through to fine grained mylonite quartz deformed plastically while both k feldspar and plagioclase fractured and recrystallized in conjunction with chemical change which had as its end point an assemblage albite quartz white mica caal silicates k feldspar and calcic plagioclase depending on fluid chemistry from the parent rock were unstable at low metamorphic grades in the presence of aqueous fluid since ca bearing plagioclase was not stable in these environments myrmekite did not replace k feldspar in any of the rocks examined recrystallization of feldspar which should perhaps be termed neocrystallization was initiated predominantly at clast margins or along microfractures that are marked by fluid inclusions and twin offsets in old feldspar grains particularly in plagioclases dislocations exist in wall like structures that are commonly associated with voids suggesting origins in microfractures these dislocations had severely limited mobility and subgrain rotation does not appear to have contributed to recrystallization we conclude that recrystallization mainly occurred via a classical nucleation mechanism with minor contributions from twin boundary migration we argue that the 450 550 c lower limit for recrystallization of feldspar referenced throughout the literature is not applicable to the rock systems under investigation and should be discarded as a universal limit microfracturing microboudinage and reaction are seen as the prerequisites for mylonite formation from coarse grained granitic rocks at low metamorphic grades see part ii of this paper neocrystallization fluid access and nucleation appear to have accompanied or immediately followed the first deformation increments and were primarily responsible for continued grain size reduction transgranular fracture was comparatively important only at the onset of deformation since the formation of shear zones in granitoids commonly takes place under conditions of low metamorphic grade in the presence of aqueous fluids in the earth s crust breakdown reactions and nucleation recrystallization in feldspars may be important influences upon localization of deformation in granitoids

structural evolution of andros cyclades greece a key to the behaviour of a flat detachment within an extending continental crust the continental crust extends in a brittle manner in its upper part and in more distributed ductile manner in its lower part during exhumation of hp metamorphic rocks brittle features superimpose on earlier ductile ones as a result of the progressive localization of deformation the islands of tinos and andros are part of the numerous metamorphic core complexes exhumed in the aegean domain they illustrate two steps of a gradient of finite extension along a transect between mt olympos and naxos this study confirms the main role of boudinage as an initial localizing factor at the brittle ductile transition and emphasizes the continuum of strain from ductile to brittle during exhumation early low angle semi brittle shear planes superimpose onto precursory ductile shear bands whereas steeply dipping late brittle planes develop by progressive steepening of structures or sliding across en echelon arrays of veins the comparison between tinos and andros allows us to propose a complete dynamic section of the aegean extending continental crust and emphasizes that the strain localization process depends on both its rheological stratification and its compositional heterogeneity

surface temperature differences between minerals in crystalline rocks implications for granular disaggregation of granites through thermal fatigue thermal expansion differences between minerals within rocks under insolation have previously been assumed to drive breakdown by means of granular disaggregation however there have been no definitive demonstrations of the efficacy of this weathering mechanism different surface temperatures between minerals should magnify thermal expansion differences and thus subject adjacent minerals to repeated stresses that might cause breakdown through fatigue failure this work confirms the existence of surface temperature differences between minerals in granitic rocks under simulated short term temperature fluctuations so as to discriminate their potential for initiating granular disaggregation the influence of colour as a surrogate for albedo and crystal size as a function of thermal mass are specifically identified because of their ease of quantification four rock types with a range of these properties were examined and subjected to repeated short term temperature cycles by radiative heating and cooling under laboratory conditions results show that while albedo is the main control for overall and individual maximum temperatures crystal size is the main factor controlling higher temperature differences between minerals thus stones with large differences of mineral sizes can undergo magnified stresses due to thermal expansion differences

rock temperatures from southeast morocco and their significance for experimental rock weathering studies surface and subsurface rock temperature measurements are presented from three rock types chalk granite and sandstone from a hot desert climate the temperature regimes undergone by each rock type and the differences between them can be best explained by reference to the values of albedo and thermal conductivity for the rocks the significance of thermal properties in influencing rock temperatures suggests that these properties should be taken into account when attempting to simulate desert weathering and also when trying to explain variations in the weathering behavior of different rock types

spatial trends in the geochemical composition of sediments in the panuco river discharge area gulf of mexico major and trace elements organic matter carbonates loss of ignition grain size gravel sand silt clay and qualitative mineralogical composition were determined on surficial marine sediments sampled during the stormy february dry may and rainy september seasons in the coastal area adjacent to panuco river discharges into the gulf of mexico the sediments supplied by the river move in a north east direction and are deposited in the north east extreme of the studied area terrigenous sediments show a strong association of al2o3 with fe2o3 na2o k2o p2o5 rb cu zn organic matter clay and grain size mz mineralogical analysis shows that they are formed by quartz kaolinite montmorillonite illite montmorillonite and biotite the highest metal concentration of cu 25 mg kg zn 155 mg kg pb 50 mg kg and organic matter 1 26 was observed in the sampling points located very close to the river mouth a statistical analysis was done with the information contained in the variables five significant factors explain 77 of the total variance factor 1 is due to sediments from a terrigenous source factor 2 corresponds to sediments from a biogenous source factor 3 is associated to sediments with heavy minerals factor 4 is due to co concentration and factor 5 is due to ni concentration the sediments supplied from the river had a short term local impact on the sediment distribution as observed by the carbonate and heavy mineral concentration of the sediments

evolution of hydrothermal regime along a crustal shear zone tinos island greece 1 structural cathodoluminescence and sims 18o analyses of quartz calcite veins are combined to constrain the evolution in space and time of fluid infiltration in an exhuming detachment shear zone tinos island cyclades greece careful description of vein arrays shows that the plumbing system evolved into an interconnected network just beneath the ductile to brittle transition microtextures of quartz and calcite infilling veins display deformed relics and newly precipitated grains high resolution 18o mapping in relics yields a steady quartz calcite fractionation of 2 at 400 c whereas fractionation increases in neograins from 2 to 5 in 190 m toward the fault or a 150 c temperature fall cooling is associated with a shift of fluid stable isotope signature from 15 to 0 beneath the detachment results are interpreted as advective removal of heat by massive infiltration of surface derived fluids over depths of 10 15 km fluid penetration was promoted by the coalescence of late ductile early brittle veins as the exhuming footwall crossed the ductile brittle transition only small amounts of fluids penetrated the ductile crust beneath the transitional rheology

the adriatic sea general circulation part ii baroclinic circulation structure abstract in the second part of the paper dedicated to the adriatic sea general circulation the horizontal structure of the hydrographic parameters and dissolved oxygen fields is described on a seasonal timescale maps of temperature and salinity climatological fields reveal the enhanced seasonal variability of the adriatic sea which at the surface is associated with the major dilution effects of river runoff the density and derived dynamic height fields show for the first time the baroclinic geostrophic structure of the general circulation winter is dominated by compensation effects between temperature and salinity fronts along the western coastline the resulting baroclinic circulation is weak and suggests the presence of barotropic current components not accessible by the dataset spring and summer seasons have the smallest spatial scales in the temperature and salinity fields and stronger subbasin scale gyres and current systems which have been classified in a schematic representation of the circu

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

influence of surface heterogeneities of building granite on its thermal response and its potential for the generation of thermoclasty surface properties especially albedo and aspect are widely accepted as strong influences on the surface thermal response of building stone to insolation however the influence that adjacent areas of stone with very different surface properties may have on the thermal response of a patch of stonework and the ways in which spatial variation in thermal characteristics might enhance stone decay has received relatively little attention this paper examines the differential thermal response of granite used in construction that results from the presence of dark coloured micro granular enclaves within a leucocratic host surface temperatures and temperature differences between enclaves exhibiting mico spalling enclaves with no spalling and the surrounding stone were measured for different aspects and seasons on a 20th century building in madrid these data were used to calculate a number of indices related to short term temperature cycling and temperature gradients that have the theoretical capability of generating irreversible deformation of the stone these indices suggest that micro spalling of enclaves compared to a lack of similar decay on the host rock is related to their differential thermal response to insolation most importantly the lower albedo and thermal conductivity values of the enclaves however these factors are not sufficient on their own to trigger spalling and breakdown was only observed where enclaves also experienced repeated short term surface temperature cycling caused by for example temporary shading by adjacent vegetation these rapid temperature reversals are identified as a key contributory factor to the thermally driven decay observed on some of the enclaves

ductile and brittle shortening extension parallel folds and maintenance of crustal thickness in the central aegean cyclades greece in contrast to previous studies that concentrated on the two dimensional crustal strain in the central aegean region cyclades it is shown that nne ssw extension via ductile and brittle stretching and low angle detachments was accompanied and or alternated with horizontal shortening perpendicular to the stretching direction since at least the early miocene roughly e w directed ductile shortening produced large scale overturned and upright folds having axes parallel or slightly oblique to the stretching lineation upright folding and arching of low angle normal faults occurred above the brittle ductile transition and brittle e w compression culminated with vertical axis block rotations strike slip faults and minor thrusts since at least the early miocene the structure of the cycladic massif evolved through alternating and or coeval increments of horizontal shortening and vertical thinning associated with an approximately constant nne ssw stretching exact magnitudes of the vertical and horizontal deformational components are difficult to assess nevertheless we note that extensional tectonics that affected the cyclades during the last 15 20 m y have produced no net crustal thinning we suggest that crustal thickness was maintained by extension parallel folds which represent true contractional structures and that crust was fed into the extended region from its margins

crustal scale geometry and kinematics of late orogenic extension in the central aegean cyclades and ewia island abstract the aegean continental domain is known to be the site of widespread back arc extension since at least the middle miocene overprinting structures related to the mesozoic cenozoic hellenic orogeny features attributed to early thrusting include the overall ductile deformation within two broad belts that have suffered hp lt metamorphism across the aegean this study summarizes the results of a structural study in the central aegean area cyclades and evvia island examining in particular the relationship between ductile and brittle deformation on a regional scale extension appears to be responsible for most of the ductile deformation within hp rock units that have experienced penetrative greenschist facies and higher grade metamorphic overprinting on each island studied progressive extensional deformation has occurred through the development of a major normal sense detachment zone down to depths of about 18 25 km the geometry of the extensional system on the scale of the central aegean is described taking into account the characteristic features of the regional scale ductile strain field at least two probably three subparallel major north dipping detachment zones are identified trending nw se in the northwestern cyclades and e w in the southeastern cyclades both with initial dips estimated at around 30 45 the present geometry of the extensional system implies that these detachment zones and related metamorphic core complexes interfere with each other two main evolutionary models are considered which can account for such a kinematic link between parallel detachment zones structural data favour the sequential development of synthetic major detachments zones in a direction opposite to the sense of dip of the detachments early oligocene lower miocene detachment type extension in the area studied is related to a late orogenic post thickening back arc setting

north aegean crustal deformation an active fault imaged to 10 km depth by reflection seismic data three multichannel seismic profiles imaged a normal fault to at least 10 km depth in the north aegean trough and thermaikos basin the fault is active and recent forming a scarp at sea bottom and crossing the quaternary deltaic front on the northern slope of the trough controlled to the south by the north anatolian fault prestack depth migration imaged the fault as a seismic reflector cutting steeply across the sedimentary rocks and flattening in the basement from the seismic image the n100 e strike of the fault scarp and the orientations of the three profiles the true fault dip is constrained to an average 20 in the basement a low angle dip the throw and age estimated from the geometry in the sedimentary rocks document recent onset of the motion that must have occurred at a high rate both the direction and the rate of slip are consistent with the instantaneous motion as measured by space based geodesy which shows the fault to be forming by pure normal slip large earthquakes that have occurred in the basin may relate to such normal faults whereas the north anatolian fault with its current strike slip earthquakes appears to slip here under low resolved shear stress

marine geology of the gulf of trieste northern adriatic geochemical aspects abstract geochemical analyses of surficial sediment in the gulf of trieste in terms of organic carbon total nitrogen and phosphorus 13c composition of sedimentary organic matter the trace metals hg pb cr cu zn cd ni mn and fe and the radionuclides 137cs and 210pb were carried out the higher values of organic carbon total nitrogen and phosphorus are restricted to the clayey silty sediments of the small bays of koper piran muggia and panzano and around the river isonzo outflow on the basis of 13c values the sedimentary organic matter is of entirely marine origin in the central part of the gulf which is bordered by two areas of greater terrigenous influence with the exception of hg and pb the areal distribution of the trace metals is similar to that of carbon nitrogen and phosphorus with higher contents in the clayey silty and silty sediments the mercury and pb contents exhibit a gradual decrease from the mouth of the isonzo river towards the southern part of the gulf riverine inputs also provide the most important sources of 137cs in the sediments of the gulf high 137cs activities in the uppermost layer of the cores indicate the chernobyl signal and in contrast to 210pb the vertical profiles show its occurrence in deeper layers which is attributed to diffusion of the 137cs distribution studies of the biogenic elements carbon nitrogen and phosphorus and the trace metals in the surficial and subsurficial layers of the 40 m deep borehole mk 6 in koper bay shows practically no enrichment in the former but an increase in the hg and pb contents this would not indicate a rapid increase in eutrophication in the gulf or that the sediments are an important sink for biogenic elements

constraining the physical chemical conditions of pleistocene cavernous weathering in late paleozoic granites abstract cavernous weathering such as tafoni alveoles and honeycomb structures have been recorded from a great variety of bedrocks and landforms in the present study cavernous weathering from late variscan granites was discussed as to its physical chemical regime of formation u pb dating yielded a maximum age of 1 52 0 03 ma supergene u mineralization is accompanied by kaolinite nontronite and fe iii phosphates based upon eh ph diagrams calculated for u fe p mineralization the physical chemical conditions may be described as oxidizing with ph values fluctuating around neutral at near ambient temperatures of 25 c alteration occurs in two stages dissolution of rock forming minerals and neoformation of hydrosilicates under mildly acidic conditions followed by phosphate precipitation under near neutral conditions

building sandstone surface modification by biofilm and iron precipitation emerging block scale heterogeneity and system response stone surfaces are sensitive to their environment this means that they will often respond to exposure conditions by manifesting a change in surface characteristics such changes can be more than simply aesthetic creating surface subsurface heterogeneity in stone at the block scale promoting stress gradients to be set up as surface response to for example temperature fluctuations can diverge from subsurface response this paper reports preliminary experiments investigating the potential of biofilms and iron precipitation as surface modifiers on stone exploring the idea of block scale surface to depth heterogeneity and investigating how physical alteration in the surface and near surface zone can have implications for subsurface response and potentially for long term decay patterns salt weathering simulations on fresh and surface modified stone suggest that even subtle surface modification can have significant implications for moisture uptake and retention salt concentration and distribution from surface to depth over the period of the experimental run the accumulation of salt may increase the retention of moisture by modifying vapour pressure differentials and the rate of evaporation temperature fluctuation experiments suggest that the presence of a biofilm can have an impact on energy transfer processes that occur at the stone surface for example buffering against temperature fluctuation affecting surface to depth stress gradients ultimately fresh and surface modified blocks mask different kinds of system which respond to inputs differently because of different storage mechanisms encouraging divergent behaviour between fresh and surface modified stone over time copyright 2014 john wiley sons ltd

techniques for measuring rock weathering application to a dated fan segment sequence in southern tunisia there are a number of techniques for estimating the amount of weathering a clast has undergone these usually have the objective of establishing an ordinal chronology of geomorphological surfaces or investigation of site specific conditions affecting weathering rates three such techniques are applied to a dated sequence of alluvial fan segments in southern tunisia two of these techniques depend on measuring surface roughness the micro roughness meter and a displacement approach and one uses the structural weakening of the rock fabric schmidt hammer the micro roughness meter enables calculation of standard deviation of surface height variation root mean square roughness and surface autocorrelation function of these techniques schmidt hammer rebound values standard deviation root mean square roughness and the displacement technique show systematic changes on the three fan segments which are statistically significant at the 0 05 level however the amount of variance in all datasets is very large indicating the need for caution in application of these techniques for relative dating 1998 john wiley sons ltd

influence of daily surface temperature fluctuations on rock slope stability case study of the rochers de valabres slope france the present paper describes a rockfall that has affected the rochers de valabres slope france s southern alps region and discusses one possible mechanism for the occurrence of this rockfall along with the potential for future ones in the absence of an obvious explanatory trigger factor we set out to examine whether natural daily surface temperature changes could have played a role in this event in particular it is suspected that these slight yet repeated perturbations may be a preparatory factor for rockfalls with a day to day cumulative effect a numerical model strengthens this hypothesis by showing that thermally induced deformations can be sufficient to cause the gradual downward creep of a rock block located in an awkward position to investigate this notion more thoroughly a currently vulnerable part of the rochers de valabres slope has been instrumented with a high precision geodetic monitoring system total station it is believed that this device is able to capture thermally induced movements if specific precautions are taken the instrumented rock volume is used as a test site in the aim of better understanding the consequences of surface temperature changes on slope stability measured data with a precision level never before achieved on rock slopes are compared herein with numerical modelling results the initial conclusions of the long term study we are conducting indicate that surface temperature changes play an important while not easily quantifiable role in preparing rockfalls

rock warming and drying under simulated intertidal conditions part i experimental procedures and comparisons with field data the wetting drying and warming cooling behaviours of rock and stone are known to influence the nature and rate of weathering the way materials warm up and dry out also influences their suitability as biological substrata while rock thermal behaviours have been measured under controlled laboratory conditions previous experiments have largely been restricted to terrestrial simulations due to practical constraints where efforts have been made to simulate intertidal conditions expansion and contraction of rocks or rates of breakdown i e sediment production and weight loss have been measured while detailed observations of thermal and drying behaviours have rarely been made a simple semi automated procedure is described that enabled measurement of surface temperatures and desorption evaporative water loss for different material types rock and concrete under simulated semidiurnal tide conditions some preliminary results are presented illustrating the types of data that were obtained and comparisons are made with temperature data collected on a rock platform in the uk to assess the ability of the procedure to adequately represent field conditions copyright 2011 john wiley sons ltd

investigations into the relationship between changes in internal moisture regimes and rock surface deterioration in cavernous sandstone features cavernous features commonly develop in sandstone but their development over time remains enigmatic it has been suggested that moisture movements within the rock mass play a key role in the location development and dynamics of cavernous features in this research the role of internal moisture movement is tested through monitoring moisture and surface deterioration dynamics in april 2008 and april 2009 within two large cavernous features mega tafoni in the golden gate highlands national park south africa gghnp data are presented from surveys of internal moisture using electrical resistivity tomography ert surface moisture using a protimeter and deterioration using surface hardness as recorded with an equotip as a proxy for surface deterioration across five 2 45 m long transects in addition a high resolution temperature record is presented to assess the influence of micro climates within the caverns the results indicate consistency in the gross spatial pattern of moisture flow within the rock mass over a one year period but significant changes in mean moisture contents and in the fine detail of moisture patterning some noticeably weakened areas had developed within the central parts of the cavernous features often linked to wetter subsurface conditions supporting the theory that core softening is a main driver of cavernous feature formation however in some areas surface hardening is also found to be associated with wetter subsurface conditions supporting the theory that case hardening is a main driver of cavernous feature formation in addition the presence of well established biofilms suggests an even more complex interaction between moisture surface development and biological activity a model is presented therefore which integrates this paradox by proposing a non linear relationship between moisture dynamics facilitation of biofilm formation and deterioration within cavernous features

geochemistry of sediments in the northern and central adriatic sea abstract major minor and trace elements loss of ignition specific surface area quantities of calcite and dolomite qualitative mineralogical composition grain size distribution and organic micropollutants pah pcb ddt were determined on surficial marine sediments sampled during the 1990 ascop adriatic scientific cooperative program cruise mineralogical composition and carbonate content of the samples were found to be comparable with data previously reported in the literature whereas geochemical composition and distribution of major minor and trace elements for samples in international waters and in the central basin have never been reported before the large amount of information contained in the variables of different origin has been processed by means of a comprehensive approach which establishes the relations among the components through the mathematical statistical calculation of principal components factors these account for the major part of data variance loosing only marginal parts of information and are independent from the units of measure the sample descriptors concerning natural components and contamination load are discussed by means of a statistical model based on an r mode factor analysis calculating four significant factors which explain 86 8 of the total variance and represent important relationships between grain size mineralogy geochemistry and organic micropollutants a description and an interpretation of factor composition is discussed on the basis of pollution inputs basin geology and hydrodynamics the areal distribution of the factors showed that it is the fine grain size fraction with oxides and hydroxides of colloidal origin which are the main means of transport and thus the principal link between chemical physical and granulometric elements in the adriatic

grain size sensitive flow and shear stress enhancement at the brittle ductile transition of the continental crust localized shear zones along low angle normal faults have been identified in regions of extension at the brittle ductile transition of the continental crust the possibility of the strain localizing at a depth of 10 km is interpreted here as a consequence of an increase in the equivalent shear stress applied to the flow of the lower crust this enhancement of the flow stress is seen as a prerequisite for the triggering of brittle deformation mechanisms leading to strain localization the lower crust rheology used to examine this stress increase is strain rate temperature and grain size dependent due to the coupling of dislocation and diffusion creep the model structure proposed consists of a top layer the upper crust gliding rigidly above a bottom layer the lower crust which deforms in simple shear during a short time interval 1400 years the equivalent shear stress is found to increase by a factor of up to 3 67 mpa for anorthite and 17 mpa for quartz for anorthite this stress could explain the activation of a mohr coulomb failure with a friction coefficient of 0 2 which is reasonable at the depth of 10 km dislocation creep is activated during a rapid change in the prescribed velocity whereas diffusion creep dominates if the velocity is held constant highlighting the importance of grain size sensitivity for lower crustal rheology

thermal properties as controls on rock surface temperature maxima and possible implications for rock weathering four rock types basalt sandstone granite and chalk are examined with respect to the maximum surface temperatures which they experience when subjected to similar conditions of exposure rock temperature measurements are reported for an urban environment and for two experimental situations in which an infrared lamp is used to simulate heating under cold and hot conditions differences in rock temperatures are discussed with reference to thermal rock properties albedo specific heat capacity and thermal conductivity some natural situations are suggested in which thermal rock properties could conceivably play a role in determining the extent to which rocks would be affected by particular weathering processes

sediment pathway of the east china sea inferred from an r mode factor analysis of surface sediments in the okinawa trough major and trace elements loss on ignition loi and grain size distributions were determined on 190 surface sediment samples collected from the continental shelf slope and the north okinawa trough in the east china sea at water depths of 100 200 200 600 and more than 600 m respectively the sediments are composed mainly of sand and silt generally low clay contents average 10 5 increasing over the range of 0 12 53 6 from the shelf and slope to the trough sediments were sandier on the continental shelf particularly in the northern shelf sector spatial distributions in chemical compositions show that the contents of sio 2 cao sr and loi values were relatively high on the sandy continental shelf by contrast the contents of al 2 o 3 mgo na 2 o mno feo tio 2 cu zn co ni and cr were relatively high in the trough and along the central western shelf margin where the sediments were composed mainly of silt fe 2 o 3 p 2 o 5 and zr enrichment was highest in the slope sediments three factors were extracted by means of an r mode factor analysis of chemical composition factor 1 has two inversely correlated elemental assemblages 1 sio 2 k 2 o tio 2 al 2 o 3 and zr which can be associated with terrigenous debris input and show high positive factor scores in the southern sector of the shelf and 2 cao sr and loi which can be related with biogenic debris enrichment and show high negative factor scores in the northern shelf sector as well as in a more restricted area along the slope cao sio 2 k 2 o and sr represent the element assemblage of the shelf factor 2 comprises na 2 o feo al 2 o 3 tio 2 cu zn and ni and shows high scores in the trough sediments na 2 o cu zn and ni represent the elemental assemblage of the okinawa trough and can be associated with volcanic matter factor 3 comprises fe 2 o 3 mgo cr and co with high factor scores on the slope and along the central western shelf margin of the study area due to upwelling induced enrichments in nutrients and biogenic shells fe 2 o 3 and mgo are the slope elements based on the results of the distribution of the chemical compositions and the elemental assemblage of the surface sediment in the source to sink system the influence of the yellow river on the continental shelf is stronger than that of the yangtze river from the continental shelf and slope to the trough the influence of the yellow river decreased from north to south in the okinawa trough the sediment from the yellow river decreases and from the yangtze river increases and the chemical compositions changed c 2009 elsevier ltd and inqua all rights reserved

relative age dating of inorganic deposits the need for a more critical approach relative age dating rd techniques rely on indices of post depositional change principally degree of rock surface weathering or soil development in the chronosequence approach where a measured parameter displays a trend in values that parallels a trend in surface age the parameter is commonly assumed to be age dependent such an assumption may be invalid this is demonstrated with particular reference to glacier forelands where environmental and sedimentological factors that can influence commonly used rd parameters may exhibit systematic variations in parallel with but independent of surface age where some independent dating control is available regression analysis may be used to define chronofunctions providing numerical ages based on rd parameters however the error limits of such ages are often underestimated the use of modal rather than mean values is particularly problematic a more critical approach is suggested involving deductive experiments to examine the influence of non tempo

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

microclimate and weathering in the central namib desert namibia data on rock surface microclimates at four sites kleinberg vogelfederberg gobabeb and ganab along a transect across the central namib desert over a 3 year period have been collected alongside some shorter term data sets rock surface temperature rst air temperature wind relative humidity and surface wetness data are presented here weathering of exposure blocks of local marble and granite has also been monitored over the 3 year period with change observed visually and with scanning electron microscopy complex temporal patterns of rock temperature fluctuations are observed over the 3 years although the four sites show very similar overall trends suggesting spatial homogeneity in the rock surface temperature regime relative humidity and surface wetness data show clear differences between the four sites related to the frequency of fogs granite blocks show no visible changes after 2 years of weathering whereas marble blocks especially those at ganab show sem evidence of structural weakening after 1 year

cymrite and celsian in manganese rich metamorphic rocks from andros island greece manganese rich rocks from the island of andros cyclades greece contain cymrite baal2si2o8 h2o and celsian the textural relationships indicate replacement of celsian by cymrite several microprobe analyses of cymrites show a solid solution of 0 7 6 1 mole kalsi3o8 h2o the relic celsians have similar k contents thus the described rocks from andros represent the first natural example for the reaction celsian water cymrite the rocks from andros underwent an eocene high pressure metamorphism lateron the high pressure parageneses were nearly effaced by a late oligocene barrovian type metamorphism it is assumed that both cymrite and celsian were formed at conditions near the reaction curve celsianss water cymritess during the barrovian type event

geochemical characteristics of western ross sea antarctica sediments abstract a geochemical study of bottom sediments from 50 stations in various ross sea sedimentary environments ranging from the coastal strip to the external platform situated off southern victoria land between the david and mariner glaciers has demonstrated the silicate nature of these sediments and significant variations in the major element concentrations the presence and concentrations of the trace elements studied cr ni co v cu pb zn and cd differ from one geographic area to another and within a given basin a statistical analysis of the geochemical variables using the cluster method shows that si is independent of the other elements which group into associations a multivariate statistical analysis based on geochemical granulometric and environmental parameters identifies five distinct sediment groups located in different areas of sedimentation and with peculiar geochemical characteristics group 1 on the external platform which comprises very fine sediments is characterised by the highest contents of mg loi cr ni and v and of cu and zn group 2 from the banks formed by pelitic sands is distinguished on the basis of lower cu and zn and higher cr and si group 3 on the internal platform consisting of sandy sediments comprises high values of na al ca and pb and low values of zn and v group 4 in the coarse coastal sands is enriched in co and ca na k and al group 5 formed by materials with different grain size distribution located south of coulman island is distinguished by a very high content of zn fe ti and na with cr co pb and si being found at lower levels the materials are glacial detrital are derived from the rocky hinterland formations and are reworked by transport and deposition processes depending on the energy level of the marine sedimentary environments given the scarcity of comparison data from the hinterland rocks it is difficult to establish the parent rocks of these glaciomarine sediments on the basis of geochemical data alone only in the case of the sediments south of coulman island can one be certain of a contribution from the mcmurdo volcanics for the external platform sediments the highest contents of si and l o i confirm the input of material from biogenic neoformation

metamorphic core complexes of cordilleran type in the cyclades aegean sea greece the islands of ios and naxos in the cycladic archipelago greece contain elongate domes over which a pervasive north to north northeast stretching lineation is warped these islands may be metamorphic core complexes of cordilleran type involving middle crustal rocks drawn upward and outward from underneath the sedimentary basins now 100 km to the south from ca 25 ma onward during uplift the crystalline rocks now exposed on the islands were deformed noncoaxially in the deeper levels of a major shallow dipping ductile shear zone this shear zone may have connected with low angle normal faults in its upper levels because it is probable that its later history involved the metamorphic complexes being dragged out from under a stretching and fracturing upper plate composed mainly of unmetamorphosed sedimentary and ophiolite suite rocks this model can be extended to explain the exhumation of the high pressure low temperature metamorphic rocks on crete which with the cyclades forms a distended paired metamorphic belt separated by an active sedimentary basin